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Chapter One: Introduction

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Chapter One

Introduction

1.1 Introduction

Due to high and rapid development in the oil industry at the last

century, many different problems had occurred, one of them is the

environmental pollution in all elements of the environment, such as water,

soil and air, which began to raise serious questions that need a rapid

solutions. Soil pollution is one of these environmental pollutions.

In general, there are many sources of soil pollution, man-made sources

including automobiles, power generation and the industrial activities. They

represent the main source of air pollution and thus causes soil pollution by

precipitation; especially, oil industry activities using huge amount of

consumable fuel, like power plants and oil refinery; due to the high rate

emission of fume, solid particulates and toxic gases more than other

industry in quantity (Afaj and Al-Khashab, 2007).

These industries are more hazardous to the environment upon its

existence within the limits of the cities, or its existence within urban area,

and or near the agricultural terrines such as Al-Daura power plant, south

Baghdad power plant and Al-Daura oil refinery.

1.2 Aim of Study

Due to higher increase in oil industry activities in Iraq, since there are a

little information of the environmental status of the areas around the

refinery locations, and the concerns of a possible environmental pollution


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that will cause health and life threats to living organisms, this study was

carried out.

The results of this study, therefore, will be helpful to decision-makers,

planners, scientists, and the local communities. The study will also be

useful as a base for decision making to protect the environment in areas

surrounding various oil refineries in the country.

1.3 Study Objectives

1.3.1 Overall Objective

The overall objective of the study is to assess the risk level of heavy

metals pollution in soils and plants in areas surrounding Al-Daura refinery

sites in Baghdad.

1.3.2 Specific Objectives

1. Determine the concentration of the heavy metals, such as zinc,

nickel, lead and cadmium in the soil and plants (seasonal vegetable),

and illustrate the distribution of these pollutants within the

production units of the refinery and in the area around the refinery by

using ArcGIS software; and to indicate the areas of high

concentration for the selected pollutants after comparison with the

standards values.

2. To study the environmental impact of these pollutants on the areas

near and around the refinery.

3. Study the relation between the pollutants and type of soil within the

depth of sample.

4. Set the appropriate environmental solutions and recommendations.


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1.3.3 Hypotheses

The study was conducted based on the hypotheses that: -

1. The area around Al-Daura refinery is significantly and highly polluted

with heavy metals.

2. There are many levels of heavy metals and chemicals in soil and plants

species growing around the oil refining areas.

1.4 Study Area

The study area is located at the south-west of Baghdad governorate,

specifically at Al-Daura region, just 4 Km from the city centre of Baghdad,

close to the western bank of Tigers River. Seventeen locations of sample,

soil and plants, distributed as seven inside the refinery and ten outside it,

Figs.(1-1) and (1-2) show the study area and sample locations.


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Fig.(1-1) Study Area Location in Baghdad.


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Fig.(1-2) Location of Samples.


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1.5 Thesis Layout

The present work is divided into five chapters:

Chapter One includes the present brief introduction and the objectives

of the present study.

Chapter Two contains a brief theoretical background and also

introduces the essential literature available about the soil polluted by heavy

metals.

Chapter Three is concerned with the oil refinery technology,

experimental and field works for detecting heavy metals concentration in

soil and plants, and soil characteristics measurements.

Chapter Four involves with the results obtained from field and

laboratory experimental work and the discussion of these results.

Chapter Five contains conclusions and recommendations for future

works.

Chapter Two: Theoretical Background and Literatures Review

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Chapter Two

Theoretical Background and Literatures Review

2.1 Introduction

Heavy metals have been differently defined by many sectors of

academia. Many different definitions have been proposed – some based on

density, some on atomic weight, and some on chemical properties or

toxicity (Duffus, 2002). Heavy metals are natural components of the earth

crust which cannot be degraded or destroyed [EPA (SA), 2009].

Many industries, such as refining, mining and smelting give rise to

release of heavy metals into the environment, and also because the adverse

effects of these metals on the environment, many researchers, studies and

legislations have been introduced all over the world to explain the effects

of heavy metals on the environment generally.

2.2 Heavy Metals

The metals are classified as “heavy metals” if, in their standard state,

they have a specific gravity of more than 5 (Issa, 2008). There are sixty

known heavy metals. Heavy metals can accumulate over time in soils and

plants and could have a negative influence on physiological activities of

plants (e.g., photosynthesis, gaseous exchange, and nutrient absorption),

causing reductions in plant growth, dry matter accumulation and yield

(Devkota and Schmidt, 2000). There are many terms used to describe and

categorize metals, including trace metals, transition metals, micronutrients,

toxic metals and heavy metals. Many of these definitions are arbitrary, and

these terms have been loosely used in the literature to include elements that

do not strictly meet the definition of the term. Metals are defined as any


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element that has a silvery luster and is a good conductor of heat and

electricity (McLean and Bledsoe, 1992).

2.2.1 Fate of Heavy Metals in Soil and Environment

The incidence of heavy metal contamination from both natural and

anthropogenic sources has increased concern about possible health effects.

Natural and anthropogenic sources of soil contamination are widespread

and variable (Tahir et al., 2007). According to Ross (1994), the

anthropogenic sources of metal contamination can be divided into five

main groups:

(1) metalliferous mining and smelting (arsenic, cadmium, lead and

mercury); (2) industry (arsenic, cadmium, chromium, cobalt, copper,

mercury, nickel, zinc); (3) atmospheric deposition (arsenic, cadmium,

chromium, copper, lead, mercury, uranium); (4) agriculture (arsenic,

cadmium, copper, lead, selenium, uranium, zinc); and (5) waste disposal

(arsenic, cadmium, chromium, copper, lead, mercury, zinc). Heavy metal

contamination of soil results from anthropogenic processes, such as

refining (Conservation Current, 2005), mining (Navarro et al., 2008),

smelting procedures (Brumelis et al., 1999) and agriculture (Vaalgamaa

and Conley, 2008) as well as natural activities.

Chemical and metallurgical industries are the most important sources of

heavy metals in the environment (Cortes et al., 2003). Industries, such as

plating, ceramics, glass, mining, refining and battery manufacture are

considered the main sources of heavy metals in local water systems,

causing the contamination of groundwater with heavy metals.

Heavy metals which are commonly found in high concentrations in

landfill leachate, are also a potential source of pollution for groundwater

(Aziz et al., 2004). Large areas of agricultural land are contaminated by

heavy metals that mainly originate from former or current mining activities,


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industrial emissions or the application of sewage sludge. Metals exist in

one of four forms in the soil: mineral, organic, sorbed (bound to soil), or

dissolved. Sorbed metals represent the third largest pool and are generally

very tightly bound to soil surfaces. Although mineral, organic and sorbed

metals are not immediately absorbed by plants, they can slowly release

metals into solution (Jones and Jacobsen, 2003). The inability to determine

metal species in soils hampers efforts to understand the mobility,

bioavailability and fate of contaminant metals in environmental systems

together with the assessment of the health risks posed by them and the

development of methods to remediate metal contaminated sites (D‟Amore

et al., 2005). However, in some natural soils developed from metal rich

parent materials as well as in contaminated soils, up to 30 to 60% of heavy

metals can occur in easily unstable forms (Karczewska et al., 1998). In soil,

metals are found in one or more of several "pools" of the soil, as described

by Shuman (1991):

1. dissolved in the soil solution;

2. occupying exchange sites in inorganic soil constituents;

3. specifically adsorbed in inorganic soil constituents;

4. associated with insoluble soil organic matter;

5. precipitated as pure or mixed solids;

6. present in the structure of secondary minerals; and/or

7. present in the structure of primary minerals

In situations where metals have been introduced into the environment

through human activities, metals are associated with the first five pools.

Native metals may be associated with any of the pools depending on the

geological history of the area. The aqueous fraction and those fractions in

equilibrium with this fraction, i.e., the exchange fraction, are of primary

importance when considering the migration potential of metals associated

with soils (McLean and Bledsoe, 1992).


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Heavy metals occur naturally in the environment, but may also be

introduced as a result of land use activities. Natural and anthropogenically

introduced concentrations of metals in near-surface soil can significantly

vary due to the different physical and chemical processes operating within

soils across geographic regions (Murray et al., 2004). Migration of metals

in the soil is influenced by physical and chemical characteristics of each

specific metal and by several environmental factors. The most significant

environmental factors appear to be (1) soil type, (2) total organic content,

(3) redox potential and (4) pH (Murray et al., 1999). Although heavy

metals are generally considered to be relatively immobile in most soils,

their mobility in certain contaminated soils may exceed ordinary rates and

pose a significant threat to water quality (Bunzl et al., 2001). Organic

manure, municipal waste and some fungicides often contain fairly high

concentrations of heavy metals.

Soils receiving repeated applications of organic manures, fungicides and

pesticides have exhibited high concentrations of extractable heavy metals

(Han et al., 2000) and increased concentrations of heavy metals in runoff

(Moore et al., 1998). Previous studies indicate that metal constituents of

surface soil directly influence the movement of metals, especially in sandy

soils (Moore et al., 1998; Cezary and Singh, 2001).

2.2.2 Behavior of Heavy Metals in Soil

Monitoring the endangerment of soil by heavy metals is of interest

due to their influence on ground and surface water (Clemente et al., 2008;

Boukhalfa, 2007) and also on flora (Pandey and Pandey 2008; Stobrawa

and Lorenc-Plucińska, 2008), animals and humans (De Vries et al., 2007).

The overall behavior of heavy metals in soil is said to be governed largely

by their sorption and desorption reactions with different soil constituents,

especially clay components (Appel and Ma, 2002).


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The chemical behavior of heavy metals in soils is controlled by a

number of processes, including metal cation release from contamination

source materials (e.g., fertilizer, sludge, smelter dust, ammunition, slag),

cation exchange and specific adsorption onto surfaces of minerals and soil

organic matter, and precipitation of secondary minerals (Manceau et al.,

2000). The relative importance of these processes depends on soil

composition and pH. In general, cation exchange reactions and

complexation to organic matter are most important in acidic soils, while

specific adsorption and precipitation become more important at near-

neutral to alkaline pH values (Voegelin et al., 2003). El-Ghawi et al. (2007)

studied the trace metal concentrations in some Libyan soils and found that

the concentrations in clay surface soil are higher than in sandy soil. The

multiple regression analyses performed confirmed the importance of pH as

well as other soil properties, such as composition, electrical conductivity

and organic matter or carbonates on the behavior of nutrients and heavy

metals (Soriano-Disla et al., 2008). Increased anthropogenic inputs of Cu

and Zn in soils have caused a considerable concern relative to their effect

on water contamination (Zhang et al., 2003).

Oxidizing conditions generally increase the retention capacity of

metals in soil, while reducing conditions will generally reduce the retention

capacity of metals (McLean and Bledsoe, 1992). Filep (1998) stated that

contaminants reaching the soil can be divided into two groups, namely

micropollutants and macropollutants. Micropollutants are natural or

anthropogenic molecules, which are toxic at very low concentration.

Macropollutants are present in the environment locally and/or temporarily

to a much higher degree than normal level. The main micropollutants of

soils are inorganic or organic compounds.

(1) Inorganic micropollutants are mainly the toxic and potentially toxic

heavy metals (Pb, Cd, Ni, Zn, Cr, Hg, Cu, etc.), (2) Organic


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micropollutants include pesticides and certain non-pesticide organic

molecules: e.g., aliphatic solvents, monocyclic aromatics, halogenated

aromatics, polychlorinated biphenyls (PCBs) and polycyclic aromatic

hydrocarbons (PAHs), surfactants, plastifiers. Frequent macropollutants

are:

Inorganic (nitrogenous fertilizers).

Organic (crude oil and products of oil industry).

In liquid phase, they exist as hydrated ions, soluble organic and

inorganic complexes and as a component of fine disperse floating colloids.

In the solid, phase they occur as insoluble precipitates and minerals on the

surface of organic and inorganic colloids in exchangeable and non-

exchangeable (specific adsorbed) forms (Filep, 1998).

2.2.2.1 Accumulation

Atanassov et al. (1999) stated that heavy metals are of interest due to

their abundance in the environment, which has increased considerably as a

result of human activities. Their fate in polluted soils is a subject of study

because of the direct potential toxicity to biota and the indirect threat to

human health via the contamination of groundwater and accumulation in

food crops (Martinez and Motto, 2000). Heavy metals are dangerous,

because they tend to bioaccumulate. This means that the concentration of a

chemical in a biological organism becomes higher relative to the

environmental concentration (Kampa and Castanas, 2008). Heavy metal

pollution of soil enhances plant uptake, causing accumulation in plant

tissues, eventual phytotoxicity and change of plant community (Gimmler et

al., 2002). In environments with high nutrient levels, metal uptake can be

inhibited because of complex formation between nutrient and metal ions

(Gothberg et al., 2004). Therefore, a better understanding of heavy metal

sources, their accumulation in the soil and the effect of their presence in


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water and soil on plant systems seems to be a particularly important issue

(Sharma et al., 2004). Accumulation of heavy metals can also cause a

considerable detrimental effect on soil ecosystems, environment and human

health due to their nobilities and solubilities which determine their

speciation (Kabata-Pendias and Pendias, 1992).

Several studies have indicated that the crops grown on soils

contaminated with heavy metals have higher concentrations of heavy

metals than those grown on uncontaminated soil (Nabulo, 2006). Heavy

metals accumulating in soil directly (or through plants indirectly) enter

food chains, thus endangering herbivores, indirectly carnivores and not

least the top consumer humans (Kadar, 1995). Plant cells have mechanisms

for bioaccumulation, selective absorption and storage of a great variety of

molecules. This allows them to accumulate nutrients and essential minerals

(Cunningham, 2001). Compounds accumulate in living organisms any

time, they are taken up faster than they are broken down (metabolized) or

excreted (O‟Brien, 2008). Total levels of heavy metals have shown a trend

relationship between metal concentration in soil and long term irrigation

(Abdelazeem et al, 2007).

Metals such as lead, arsenic, cadmium, copper, zinc, nickel, and

mercury are continuously being added to our soils through various

agricultural activities; such as agrochemical usage and long-term

application of urban sewage sludge in agricultural soils; industrial

activities, such as waste disposal, waste incineration and vehicle exhausts

together with anthropogenic sources. All these sources cause accumulation

of metals and metalloids in our agricultural soils and pose threat to food

safety issues and potential health risks due to soil to plant transfer of metals

(Khan, 2005). Investigations of heavy metal migration and accumulation in

natural conditions are very laborious as it is difficult to control all


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numerous factors influencing metal behavior in the field (Ermakov et al.,

2007).

2.2.2.2 Solubility and Mobility

Among the negative impacts related to human activities, the

mobilization of heavy metals from their naturals reservoirs to the aquatic

and terrestrial ecosystems has become a generalized problem almost

worldwide (Han et al., 2002; Koptsik et al., 2003; Salemaa et al., 2001).

Heavy metal solubility and mobility in soils are of environmental

significance due to their potential toxicity to both humans and animals

(Chirenje et al., 2003).

The transfer and the chemical stability of metal contaminants in soils

and sediments are controlled by a complex series of biogeochemical

processes, depending on variables like pH, clay content and redox potential

(Vanbroekhoven, 2006).

Trace metal mobility is closely related to metal solubility, which is

further regulated by adsorption, precipitation and ion exchange reactions in

soils (Ma and Dong, 2004). Pb is reported to be the least mobile among the

other heavy metals, but the Cd is known to be the most mobile under

conditions of different soils (Kabata-Pendias and Pendias, 1992).

The transfer of heavy metals from soils to plants is dependent on

three factors: (1) the total amount of potentially available elements

(quantity factor), (2) the activity as well as the ionic ratios of elements in

the soil solution (intensity factor), and (3) the rate of element transfer from

solid to liquid phases and to plant roots (reaction kinetics) (Brummer et al.,

1986). However, changes in soil solution chemistry, such as pH, redox

potential and ionic strength, may also significantly shift the retention

processes of trace metals by soils (Gerringa et al., 2001).


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These effects may be further complicated by ligand competition from

other cations (Norrstrom and Jacks, 1998). Soil redox status varies

temporally and spatially. In a surface soil, it is influenced by the rainfall,

bioactivity, and changes in the land use, whereas it varies mainly with the

fluctuation of water table (Boul et al., 1997). Reduction in the redox

potential may cause changes in metal oxidation state, formation of new

low-soluble minerals and reduction of Fe, resulting in release of associated

metals (Baumann et al., 2002; Chuan et al., 1996). Metal solubility

increases usually as the pH decreases, with the notable exception of metals

present in the form of oxyanions or amphoteric species. Since soil solution

properties might change with time (for example following sludge

application), the solubility and speciation of metals might also be time-

dependent (Mo et al., 1999). As the soil pH increases, the solubility and

availability of these trace nutrients decrease (Mellbye and Hart, 2003). The

solubility of most metals becomes limited around pH values of 5.5 to 6.0.

Immobilization of metals by the mechanisms of adsorption and

precipitation will prevent movement of the metals to the ground water.

Metal-soil interaction is such that when metals are introduced at the soil

surface, the downward transportation does not occur to any great extent

unless the metal retention capacity of the soil is overloaded or metal

interaction with the associated waste matrix enhances mobility. Changes in

soil environmental conditions over time, such as the degradation of the

organic waste matrix, changes in pH, redox potential, or soil solution

composition, due to various remediation schemes or to natural weathering

processes may also enhance the metal mobility (McLean and Bledsoe,

1992).


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2.2.2.3 Bioavailability

Bioavailability depends on biological parameters and on the

physicochemical properties of metals, their ions and their compounds.

These parameters in turn depend upon the atomic structure of the metals,

which is systematically described by the periodic table (VanLoon and

Duffy, 2000). The bioavailability and mobility of metals in soil depend

strongly on the extent of their sorption with solid phases. Partitioning of

heavy metals between solid and aqueous phases is controlled by properties,

such as surface area, surface charge (induced by the formation of organic

coatings on the surface), pH, ionic strength and concentration of

complexing ligands (Petrovic et al., 1999).

The pH and redox potential affect the bioavailability of metals in

solution; at high pH, the elements are present as anions, while at low pH

the bioavailability of metals ions is enhanced (Peterson et al., 1984). In

natural systems, the bioavailability of trace metals is primarily controlled

by adsorption-desorption reactions at the particle-solution interface (Backes

et al., 1995). The availability of metals also decreases in the calcareous soil

horizons because of the enhanced buffering capacity of these horizons

(Sipos, 2004). The soil pH will influence both the availability of soil

nutrients to plants and how the nutrients react with each other. Hollier and

Reid (2005) stated that at a low pH, many elements become less available

to plants, while others such as iron, aluminum and manganese become

toxic to plants and in addition, aluminum, iron and phosphorus combine to

form insoluble compounds. In contrast, at high pH levels, calcium ties up

phosphorus, making it unavailable to plants, and molybdenum becomes

toxic in some soils. Generally, heavy metals become increasingly mobile

and available as the pH decreases (Tyler and Olsson, 2001) depending on

the actual combination of physical and chemical properties of soil

(Shuman, 1985).


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2.2.2.4 Toxicity

Recently, pollution of the general environment has gathered an

increased global interest. In this respect, the contamination of agricultural

soils with heavy metals has always been considered a critical challenge in

the scientific community (Faruk et al., 2006). Heavy metals are generally

present in agricultural soils at low levels. Due to their cumulative behavior

and toxicity, however, they have a potentially hazardous effect not only on

crop plants but also on human health (Das et al., 1997). Even metals,

essential to plant growth, like copper (Cu), manganese (Mn), molybdenum

(Mo), and zinc (Zn) but can be toxic to the plants at high concentrations in

the soil. Some elements, not known to be essential to plant growth, such as

arsenic (As), barium (Ba), cadmium (Cd), chromium (Cr), lead (Pb), nickel

(Ni) and selenium (Se) are also toxic at high concentrations or under

certain environmental conditions in the soil (Slagle et al., 2004).

Both pH and redox potential affect the toxicity of heavy metals by

limiting their availability (Peterson et al., 1984). At low pH, metals

generally exist as free cations; at alkaline pH, however, they tend to

precipitate as insoluble hydroxides, oxides, carbonates, or phosphates

(Mamboya, 2007). Chemical hazards include chemical agents like heavy

metals, nutrients, such as nitrogenous compounds, phosphorus compounds,

minerals, insecticides, pesticides, fertilizers, fungicides, herbicides and

organic hazards (Nabulo et al., 2008).

Metals, unlike the hazardous organics, cannot be degraded. Some

metals, such as Cr, As, Se and Hg can be transformed to other oxidation

states in soil, thus influencing their mobility and toxicity (McLean and

Bledsoe, 1992). Many of them (Hg, Cd, Ni, Pb, Cu, Zn, Cr, Co) are highly

toxic both in elemental and soluble salt forms. The high concentration of

heavy metals in soils is toxic for soil organisms: bacteria, fungi and higher

organisms (Woolhouse, 1993). Short-term and long-term effects of


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pollution differ, depending on metal and soil characters (Kadar, 1995;

Nemeth and Kadar, 2005). In the after-effect of heavy metal pollutions, the

role of pollutant bounding or leaching increases, which determines their

bioavailability and toxicity (Mathe-Gaspar et al., 2005). When the soil is

acidified it increases the concentration of free aluminum ions in the water

that is in the soil, and these are potentially toxic to the root systems of

plants.

The mobility of many heavy metals also increases when the soil

becomes more acidic. Perhaps, the most serious consequence of the higher

metal concentrations is their negative effect on many of the decomposers

that live in the soil (Elvingson and Agren, 2004). The U.S. Environmental

Protection Agency (U.S. EPA, 1993) regulates nine trace elements for the

land-applied sewage sludge: As, Cd, Cu, Pb, Hg, Mo, Ni, Se and Zn. Only

six of these elements (Cu, Ni, Zn, Cd, Pb, Se) are considered to be

phytotoxic (Schmidt, 1997). Accounting for element speciation,

complexation and the dynamic interaction of solid surfaces (soils, organic

matter and live plants) and water with trace elements, it is difficult to

determine the maximum allowable total trace element concentrations that

can exist in soils without becoming potentially toxic to plants or harming

the environment (Slagle et al., 2004).

2.2.3 General Features of the Investigated Heavy Metals

2.2.3.1 Zinc

Zinc is a very common substance that occurs naturally. It is the 23rd

most abundant element in the Earth's crust. Many foodstuffs contain certain

concentrations of zinc. Drinking water also contains certain amounts of

zinc, which may be higher when it is stored in metal tanks. Industrial

sources or toxic waste sites may cause the zinc amounts in drinking water

to reach levels that can cause health problems.

http://www.lenntech.com/drinking-water-FAQ.htm


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(http://www.lenntech.com/periodic/elements/zn.htm)

Zinc occurs naturally in air, water and soil, but zinc concentrations

are rising unnaturally due to the addition of zinc through human activities.

Most zinc is added during industrial activities, such as mining, coal and

waste combustion and steel processing. Some soils are heavily

contaminated with zinc, and these are because the use of sewage and

composted materials in agricultural and the use of agrochemicals, such as

fertilizers and pesticides (Alloway, 1995). Some of the studies have also

linked high Zn levels to accumulation from traffic, industry input (Imperato

et al., 2003) vehicle emissions and tyre and brake abrasion (Garty et al.,

1985; Ward, 1990).

Zinc is strongly adsorbed onto organic matter and clay particles in

the soil and this adsorption is related to the Cation Exchange Capacity of

the system in acidic media and is influenced by organic ligands in alkaline

media (Antoniadis, 1998).

Health Effects of Zinc: Zinc is a trace element that is essential for

human health. When people absorb too little zinc, they can experience a

loss of appetite, decreased sense of taste and smell, slow wound healing

and skin sores. Zinc-shortages can even cause birth defects.

Although humans can proportionally handle large concentrations of

zinc, too much zinc can still cause eminent health problems, such as

stomach cramps, skin irritations, vomiting, nausea and anemia. Very high

levels of zinc can damage the pancreas and disturb the protein metabolism

and cause arteriosclerosis. Extensive exposure to zinc chloride can cause

respiratory disorders.

http://www.lenntech.com/water-FAQ.htm

http://www.lenntech.com/Periodic-chart-elements/Cl-en.htm


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In the work place environment, zinc contagion can lead to a flu-like

condition known as metal fever. This condition will pass after two days and

is caused by over sensitivity.

Zinc can be a danger to unborn and newborn children. When their

mothers have absorbed large concentrations of zinc, the children may be

exposed to it through blood or milk of their mothers.


Effects of Zinc on the Environment: The world's zinc production is

still rising. This basically means that more and more zinc ends up in the

environment.

Water is polluted with zinc due to the presence of large quantities of

zinc in the wastewater of industrial plants. This wastewater is not purified

satisfactory. One of the consequences is that rivers are depositing zinc-

polluted sludge on their banks. Zinc may also increase the acidity of

waters.

Some fish can accumulate zinc in their bodies, when they live in

zinc-contaminated waterways. When zinc enters the bodies of these fish, it

is able to bio magnify up the food chain.

Large quantities of zinc can be found in soils. When the soils of

farmland are polluted with zinc, animals will absorb concentrations that are

damaging to their health. Water-soluble zinc that is located in soils, can

contaminate the groundwater.

Zinc cannot only be a threat to cattle, but also to plant species. Plants

often have a zinc uptake that their systems cannot handle due to the

accumulation of zinc in soils. On zinc-rich soils, only a limited number of

plants have a chance of survival. That is why there is not much plant


21

diversity near zinc-disposing factories. Due to the effects upon plants, zinc

is a serious threat to the productions of farmlands. Despite of this zinc-

containing, manures are still applied.

Finally, zinc can interrupt the activity in soils, as it negatively

influences the activity of microorganisms and earthworms. The breakdown

of organic matter may seriously slow down because of this.


2.2.3.2 Nickel

Most nickel on Earth is inaccessible, because it is locked away in the

planet's iron-nickel molten core, which is 10 % nickel. The total amount of

nickel dissolved in the sea has been calculated to be around 8 billion tons.

Organic matter has a strong ability to absorb the metal which is why coal

and oil contain considerable amounts. The nickel content in soil can be as

low as 0.2 ppm or as high as 450 ppm in some clay and loamy soils. The

average is around 20 ppm. Nickel occurs in some beans where it is an

essential component of some enzymes. Another relatively rich source of

nickel is tea which has 7.6 mg/kg of dried leaves.

(http://www.lenntech.com/periodic/elements/ni.htm)

Health Effects of Nickel: Nickel is a compound that occurs in the

environment only at very low levels. Humans use nickel for many different

applications. The most common application of nickel is the use as an

ingredient of steel and other metal products. It can be found in common

metal products, such as jewellery.

Foodstuffs naturally contain small amounts of nickel. Chocolate and

fats are known to contain severely high quantities. Nickel uptake will boost

when people eat large quantities of vegetables from polluted soils. Plants

are known to accumulate nickel, and as a result, the nickel uptake from


22

vegetables will be eminent. Smokers have a higher nickel uptake through

their lungs. Finally, nickel can be found in detergents.

Humans may be exposed to nickel by breathing air, drinking water,

eating food or smoking cigarettes. Skin contact with nickel-contaminated

soil or water may also result in nickel exposure. In small quantities, nickel

is essential, but when the uptake is too high, it can be a danger to human

health.

An uptake of too large quantities of nickel has the following

consequences:

Higher chances of development of lung cancer, nose cancer,

larynx cancer and prostate cancer.

Sickness and dizziness after exposure to nickel gas.

Lung embolism.

Respiratory failure.

Birth defects.

Asthma and chronic bronchitis.

Allergic reactions, such as skin rashes, mainly from jewellery.

Heart disorders.

Nickel fumes are respiratory irritants and may cause pneumonitis.

Exposure to nickel and its compounds may result in the development of a

dermatitis known as “nickel itch” in sensitized individuals.


Effects of Nickel on the Environment: Nickel is widely used in

industry, as it is a metal which does not corrode as much as Fe. It is,

therefore, used in the production of alloys, on which it confers them stain

and corrosion protection (Bunce, 1993).

Nickel is released into the air by power plants and trash incinerators.

It will than settle to the ground or fall down after reactions with raindrops.

http://www.lenntech.com/drinking-water-FAQ.htm


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It takes usually a long time for nickel to be removed from air. Nickel can

also end up in surface water when it is a part of wastewater streams.

The larger part of all nickel compounds that are released to the

environment, will adsorb to sediment or soil particles and become

immobile as a result. In acidic ground, however, nickel is bound to become

more mobile and it will often rinse out to the groundwater. It is evident that

the local solid waste litter and anthropogenic activities, such as burning of

fuel and residual oil contribute to the increase in Ni content in the soil

(Alloway, 1995), and the organic matter has a great influence on this

element as Ni can be strongly adsorbed by it (Leeper, 1978).

There is not much information available on the effects of nickel upon

organisms other than humans. It is known that high nickel concentrations

on sandy soils can clearly damage plants, and high nickel concentrations in

surface waters can diminish the growth rates of algae. Microorganisms can

also suffer from growth decline due to the presence of nickel, but they

usually develop resistance to nickel after a while.

For animals, nickel is an essential foodstuff in small amounts. But,

nickel is not only favorable as an essential element; it can also be

dangerous, when the maximum tolerable amounts are exceeded. This can

cause various kinds of cancer on different sites within the bodies of

animals, mainly of those that live near refineries.


2.2.3.3 Lead

Native lead is rare in nature. Currently, lead is usually found in ore

with zinc, silver and copper, and it is extracted together with these metals.

The main lead mineral is in Galena (PbS), and there are also deposits of

cerrussite and anglesite which are mined.

http://www.lenntech.com/waste_water.htm


24

Lead occurs naturally in the environment. However, most lead

concentrations that are found in the environment, are a result of human

activities. Due to the application of lead in gasoline, an unnatural lead-

cycle has consisted. Deposition related to automobile emissions and

transportations sector, in general (considering the long residence time of

Pb), may be the major source of increase in Pb content (Chatterjee and

Banerjee, 1999; Madrid et al., 2002; Imperato et al., 2003). The greatest

and most commonly known use of Pb is as fuel additives (Pb(CH3)4 and

Pb(C2H5)4) which are „anti knocking‟ agents (Baird, 1995). Lead is also

used as a absorber of high energy X and γ rays and in roofing, while PbO is

used in crystal glass, because it dispenses light spectrally (Bunce, 1993).

The larger particles will drop immediately to the ground and pollute

soils or surface waters, the smaller particles will travel long distances

through air and remain in the atmosphere. Part of this lead will fall back on

earth when it is raining. This lead-cycle caused by human production is

much more extended than the natural lead-cycle. It has caused lead

pollution to be a worldwide issue.

(http://www.lenntech.com/periodic/elements/pb.htm)

Health Effects of Lead: Lead is a soft metal that has known many

applications over the years. It has been widely used since 5000 BC for

application in metal products, cables, pipelines, in paints and pesticides.

Lead is one out of four metals that have the most damaging effects on

human health. It can enter the human body through uptake of food (65%),

water (20%) and air (15%).

Foods, such as fruit, vegetables, meats, grains, seafood, soft drinks

and wine may contain significant amounts of lead. Cigarette smoke also

contains small amounts of lead.

http://www.lenntech.com/water-FAQ.htm


25

Lead can enter drinking water through corrosion of pipes. This is

more likely to happen when the water is slightly acidic. That is why public

water treatment systems are now required to carry out pH-adjustments in

water that will serve drinking purposes.

For as far as known, lead fulfils no essential function in the human

body, it can merely do harm after uptake from food, air or water.

Lead can cause several unwanted effects, such as:

Disruption of the biosynthesis of hemoglobin and anemia.

A rise in blood pressure.

Kidney damage.

Miscarriages and subtle abortions.

Disruption of nervous systems.

Brain damage.

Declined fertility of men through sperm damage.

Diminished learning abilities of children.

Behavioral disruptions of children, such as aggression,

impulsive behavior and hyperactivity.

Lead can enter a foetus through the placenta of the mother. Because

of this, it can cause a serious damage to the nervous system and the brains

of unborn children.


Environmental Effects of Lead: Not only leaded gasoline causes

lead concentrations in the environment to rise, but also other human

activities, such as fuel combustion, industrial processes and solid waste

combustion, also contribute.


26

Lead can end up in water and soils through corrosion of leaded

pipelines in a water transporting system and through corrosion of leaded

paints. It cannot be broken down and can only convert to other forms.

Lead accumulates in the bodies of water organisms and soil

organisms. These will experience health effects from lead poisoning.

Health effects on shellfish can take place even when only very small

concentrations of lead are present. Body functions of phytoplankton can be

disturbed when lead interferes. Phytoplankton is an important source of

oxygen production in seas and many larger sea-animals eat it.


Soil functions are disturbed by lead intervention, especially near

highways and farmlands, where extreme concentrations may be present.

Soil organisms suffer from lead poisoning, too. Lead is strongly adsorbed

to organic matter in soils, more than any other heavy metal, and therefore,

organic matter is a very important sink for Pb in polluted soils. (Kabata-

Pendias and Pendias, 1992).

Lead is one of the hazardous metals that can transport to the humans

and animals through the chain food and can accumulate in the body,

causing a physiological damage.

2.2.3.4 Cadmium

Cadmium can mainly be found in the earth's crust. It occurs always

in combination with zinc. Cadmium also consists in the industries as an

inevitable by-product of zinc, lead and copper extraction. After being

applied, it enters the environment mainly through the ground, because it is

found in soils is phosphate fertilizers and manures (Kabata-Pendias and

Pendias, 1992).

http://www.lenntech.com/water-microbiology-FAQ.htm

http://www.lenntech.com/oxygen.htm

http://www.lenntech.com/Periodic-chart-elements/Zn-en.htm

http://www.lenntech.com/Periodic-chart-elements/Pb-en.htm

http://www.lenntech.com/Periodic-chart-elements/Cu-en.htm


27

Naturally, a very large amount of cadmium is released into the

environment, about 25,000 tons a year. About half of this cadmium is

released into rivers through weathering of rocks, and some cadmium is

released into air through forest fires and volcanoes. The rest of the

cadmium is released through human activities, such as manufacturing.

No cadmium ore is mined for the metal, because more than enough is

produced as a byproduct of the smelting of zinc from its ore, sphelerite

(ZnS), in which CdS is a significant impurity, making up as much as 3%.

Consequently, the main mining areas are those associated with zinc.

(http://www.lenntech.com/periodic/elements/cd.htm)

Health Effect of Cadmium: Human uptake of cadmium takes place

mainly through food. Foodstuffs that are rich in cadmium can greatly

increase the cadmium concentration in human bodies. Examples are liver,

mushrooms, shellfish, mussels, cocoa powder and dried seaweed.

An exposure to significantly higher cadmium levels occurs when

people smoke. Tobacco smoke transports cadmium into the lungs. Blood

will transport it through the rest of the body where it can increase effects by

potentiating cadmium that is already present in the cadmium-rich food.

Other high exposures can occur to people who live near hazardous

waste sites or factories that release cadmium into the air and to people who

work in the metal refinery industry. When people breathe in cadmium it

can severely damage the lungs. This may even cause death.

Cadmium first transports to the liver through the blood. There, it is

bond to proteins to form complexes that transport to the kidneys. Cadmium

accumulates in kidneys, where it damages filtering mechanisms. This

causes the excretion of essential proteins and sugars from the body and

further kidney damage.


28

Other health effects that can be caused by cadmium are:

Diarrhea, stomach pains and severe vomiting.

Bone fracture.

Reproductive failure and possibly even infertility.

Damage to the central nervous system.

Damage to the immune system.

Psychological disorders.

Possibly DNA damage or cancer development.


Environmental Effects of Cadmium: Cadmium has a wide range of

uses in the industry (Volensky, 1990). Cadmium waste streams from the

industries end mainly up in soils. The causes of these waste streams are for

instance, zinc production, phosphate ore implication and bio industrial

manure. Cadmium waste streams may also enter the air through

(household) waste combustion and burning of fossil fuels. Because of the

regulations, only little cadmium now enters the water through disposal of

wastewater from households or industries.

Another important source of cadmium emission is the production of

artificial phosphate fertilizers. Part of the cadmium ends up in the soil after

the fertilizer is applied on farmland, and the rest of the cadmium ends up in

the surface water when the waste from fertilizer productions is dumped by

production companies.

Cadmium can be transported over great distances when it is absorbed

by sludge. This cadmium-rich sludge can pollute the surface water as well

as soils.

http://www.lenntech.com/waste_water.htm


29

Cadmium strongly adsorbs to organic matter in soils. When

cadmium is present in soils, it can be extremely dangerous as the uptake

through food will increase. Soils that are acidified, enhance the cadmium

uptake by plants. This is a potential danger to the animals that are

dependent upon the plants for survival. Cadmium can accumulate in their

bodies, especially when they eat multiple plants. Cows may have large

amounts of cadmium in their kidneys due to this.

Earthworms and other essential soil organisms are extremely

susceptive to cadmium poisoning. They can die at very low concentrations,

and this has consequences for the soil structure. When cadmium

concentrations in soils are high, they can influence the soil processes of

microorganisms and threat the whole soil ecosystem.

In aquatic ecosystems, cadmium can bio accumulates in mussels,

oysters, shrimps, lobsters and fish. The susceptibility to cadmium can vary

greatly between aquatic organisms. Salt-water organisms are known to be

more resistant to cadmium poisoning than freshwater organisms.

Animals eating or drinking cadmium sometimes get high blood-

pressures, liver disease and nerve or brain damage.


2.3 Soil Properties and Heavy Metals

2.3.1 Soil pH

The link between soil pH and heavy metal threshold values reflects

the complex interaction between the heavy metals and the various soil

properties (Gawlik and Bidoglio, 2006). pH is a measure of the hydrogen

ion concentration acidity or alkalinity of the soil. Measured on a

logarithmic scale, a soil at pH 4 is 10 times more acidic than a soil at pH 5


30

and 100 times more acidic than a soil at pH 6. Increasing and decreasing

the soil pH influence the chemical reactions in the soil (Thien and Graveed,

1997).

Alkalinity is usually an inherent characteristic of soils, although

irrigation can increase the alkalinity of saline soils. Soils made alkaline by

calcium carbonate alone have rarely pH values above 8.5 and are termed

„calcareous‟. Under normal conditions, the most desirable pH range for

mineral soil is 6.0 to 7.0 and 5.0 to 5.5 for organic soil.

At the neutral values of pH, Zn, Ni and Pb have a strong relation

with soil solids, and hence its movement towards the deeper layers will be

limited or very slowly (Kabata-Pendias and Pendias, 1992).

The buffer pH is a value used for determining the amount of lime to

apply on acidic soils with a pH less than 6.6. Increases in soil pH can occur

as the result of organic matter decomposition, because mineralization and

ammonification processes release OH- ions and consume H

+ ions (Ritchie

and Dolling, 1985). Colloid and metal mobility were enhanced by

decreases in solution pH and colloid size and increases in organic matter,

which resulted in higher elution of sorbed and soluble metal loads through

a metal–organic complex formation (Karathanasis et al., 2005). Soil

weathering often involves soil acidification, and most chemical

immobilization reactions are pH dependent. Alkaline amendments reduce

the concentration of heavy metals in soil solution by raising the soil pH,

thereby allowing the formation of insoluble metal precipitates, complexes

and secondary minerals (Mench et al., 1994).

2.3.2 Organic Matter

Soil organic matter is the most important indicator of soil quality and

productivity and consists of a complex and varied mixture of organic

substances. Commonly, soil organic matter is defined as the percentage of


31

humus in the soil. Humus is the unidentifiable residue of plant soil

microorganisms and fauna that becomes fairly resistant to further decay.

Organic matter is very important in the functioning of soil systems

for many reasons (Jankauskas et al., 2007). Soil organic matter increases

soil porosity, thereby increasing infiltration and water-holding capacity of

the soil, providing more water availability for plants and less potentially

erosive runoff and agro-chemical contamination (Lal et al., 1998). Clay

minerals and organic matter have a contrary effect on heavy metal retention

in soils. There are factors dependent (e.g., clay minerals) on and

independent (e.g., organic matter) of bedrock, of which a common effect

forms the actual distribution of heavy metals in soils (Sipos, 2003).

Chemical elements in the soil are more adsorbed on the finest soil particles

(colloids) which are clay and humus. Although they are small in size,

colloids play a major influence in soil properties (Thien and Graveed,

1997). The organic matters are important factor in adsorption and

accumulation of heavy metals in soil (Alloway, 1995; Kabata-Pendias and

Pendias, 1992).

El-Ghawi et al. (2005) showed that the trace metals concentrations in

clay surface soils are higher than in the sandy soils, humic and folic acid

(organic matter) that capture the elements. Heavy metal cations sorb to the

soil organic matter and other forms of humified natural organic matter. The

type of sorption by the natural organic matter affects the environmental fate

of the heavy metal.

Heavy metal cations form sparingly soluble phosphate, carbonates,

sulfides and hydroxides. Sorption and many metal precipitation processes

are highly pH dependent with increased sorption with pH. The pH of the

soil-residual system is often the most important chemical property

governing sorption and precipitation of heavy metals (Basta et al., 2005).


32

2.3.3 Microbiological Effect

Microbes are arguably the most important consideration in managing

the living soil. Soil microbes are responsible for the greatest percentage of

nutrient recycling within the soil (Fenchel et al., 1998).

Metals play an integral role in the life processes of microorganisms.

The and metals, such as calcium, cobalt, chromium, copper, iron,

potassium, magnesium, manganese, sodium, nickel and zinc are an

essential source of micronutrients and are used for redox processes.

Microbial transformations of metals serve various functions. Generally,

microbial transformations of metals can be divided into two main

categories: redox conversions of inorganic forms and conversions from

inorganic to organic form and vice versa (Turpeinen, 2002). Through

oxidation of iron, sulfur, manganese and arsenic, microbes can obtain

energy (Santini et al., 2000). On the other hand, reduction of metals can

occur through dissimilatory reduction, where microorganisms utilize metals

as a terminal electron acceptor for anaerobic respiration (Turpeinen, 2002).

For example, oxyanions of chromium (Quilntana et al., 2001) can be used

in a microbial anaerobic respiration as terminal electron acceptors.

Microorganisms may possess reduction mechanisms that are not coupled to

respiration, but instead, are thought to impart metal resistance (Turpeinen,

2002); for example, aerobic and anaerobic reduction of Cr(VI) to Cr(III)

(Quilntana et al., 2001).

Microbiological processes can either dissolve metals, thereby

increasing their bioavailability and potential toxicity, or immobilize them

and thereby reducing the bioavailability of metals (Turpeinen, 2002). In

microbial systems, the term redox conditions refer to the microbial terminal

electron accepting processes taking place. If oxygen is present, aerobic

conditions will dominate and microbial metabolism takes place with

oxygen as the terminal electron acceptor.


33

Nitrate, oxides and hydroxides of manganese (IV) and iron (III),

sulfate and carbon dioxide can be used as electron acceptors in order to

gain energy for microbial maintenance and growth (Stumm and Morgan,

1996). Heavy metals are often mixed with organic pollutants in

contaminated sites.

In anaerobic soils, the redox potential was shown to be negatively

correlated with microbial activity (Kralova et al., 1992). Low redox

potential developed with increased soil moisture content because of the

partial or complete displacement of oxygen from soil and rapid

consumption of oxygen by soil microbes (Savant and Ellis, 1964). The

redox potential was also found to be affected by the microbial activity in

aerobic soils. Volk (1993) showed that in arable, the soils moisture

indirectly decreased the redox potential by increasing the bacterial activity.

As in other studies (Faulkner et al., 1989), a relationship between the

moisture content and redox status was observed.

2.4 Oil Refinery Technology

2.4.1 Oil Refinery Process

An oil refinery is an industrial process plant where crude oil is

processed and refined into more useful petroleum products, such as

gasoline, diesel fuel, asphalt base, heating oil, kerosene and liquefied

petroleum gas (Gary and Handwerk, 1984; Leffler, 1985). Oil refineries are

typically large sprawling industrial complexes with extensive piping

running throughout, carrying streams of fluids between large chemical

processing units.

2.4.1.1 Operation

Crude oil is separated into fractions by the fractional distillation. The

fractions at the top of the fractionating column have lower boiling points


34

than the fractions at the bottom. The heavy bottom fractions are often

cracked into lighter, more useful products. All of the fractions are further

processed in other refining units.

Raw or unprocessed ("crude") oil is not useful in the form it comes

in out of the ground. Although "light, sweet" (low viscosity, low sulfur) oil

has been used directly as a burner fuel for the steam vessel propulsion, the

lighter elements form explosive vapors in the fuel tanks, and so it is quite

dangerous, especially in warships. For this and many other uses, the oil

needs to be separated into parts and refined before use in fuels and

lubricants, and before some of the byproducts could be used in

petrochemical processes to form materials, such as plastics, detergents,

solvents, elastomers and fibers, such as nylon and polyesters. Petroleum

fossil fuels are used in ship, automobile and aircraft engines. These

different hydrocarbons have a different boiling point, which means they

can be separated by distillation. Since the lighter liquid elements are in

great demand for use in internal combustion engines, a modern refinery

will convert heavy hydrocarbons and lighter gaseous elements into these

higher value products using complex and energy intensive processes.

Oil can be used in so many various ways, because it contains

hydrocarbons of varying molecular masses, forms and lengths, such as

paraffins, aromatics, naphthenes (or cycloalkanes), alkenes, dienes and

alkynes. Hydrocarbons are molecules of varying length and complexity,

made of only hydrogen and carbon atoms. Their various structures give

them their differing properties and thereby uses. The trick in the oil

refinement process is separating and purifying these.

Once separated and purified of any contaminants and impurities, the

fuel or lubricant can be sold without any further processing. Smaller

molecules, such as isobutene and propylene or butylenes can be

recombined to meet specific octane requirements of fuels by processes,


35

such as alkylation or less commonly, dimerization. The octane grade of

gasoline can also be improved by a catalytic reforming which strips the

hydrogen out of hydrocarbons to produce aromatics which have much

higher octane ratings. Intermediate products, such as gas oils can even be

reprocessed to break heavy, long-chained oil into a lighter short-chained

one by various forms of cracking, such as fluid catalytic cracking, thermal

cracking and hydrocracking. The final step in gasoline production is the

blending of fuels with different octane ratings, vapor pressures and other

properties to meet the product specifications.

Oil refineries are large scale plants, processing from about a hundred

thousand to several hundred thousand barrels of crude oil per day. Because

of the high capacity, many of the units are continuously operated (as

opposed to processing in batches) at steady state or approximately steady

state for long periods of time (months to years). This high capacity also

makes the process optimization and advanced process control very

desirable (Alfredo, 2008).

2.4.1.2 Major Products of Oil Refineries

Most products of oil processing are usually grouped into three

categories: light distillates (LPG, gasoline and naphtha), middle distillates

(kerosene, diesel), heavy distillates and residuum (fuel oil, lubricating oils,

wax and tar).

This classification is based on the way crude oil is distilled and

separated into fractions (called distillates and residuum). (Leffler, 1985)

• Liquid petroleum gas (LPG)

• Gasoline (also known as petrol)

• Naphtha

• Kerosene and related jet aircraft fuels

• Diesel fuel


36

• Fuel oils

• Lubricating oils

• Paraffin wax

• Asphalt and Tar

• Petroleum coke

2.4.1.3 Common Process Units Found in a Refinery

The number and nature of the process units in a refinery determine

its complexity index.

• Desalter unit washes out the salt from the crude oil before it enters

the atmospheric distillation unit.

• Atmospheric Distillation unit distills the crude oil into fractions.

• Vacuum Distillation unit further distills the residual bottoms after

the atmospheric distillation.

• Naphtha Hydrotreater unit uses the hydrogen to desulfurize naphtha

from the atmospheric distillation. The naphtha must be hydreotreated

before sending to a Catalytic Reformer unit.

• Catalytic Reformer unit is used to convert the naphtha-boiling

range molecules into a higher octane reformate (reformer product). The

reformate has a higher content of aromatics, olefins and cyclic

hydrocarbons. An important byproduct of a reformer is the hydrogen

released during the catalyst reaction.

The hydrogen is used either in the hydrotreaters or the hydrocracker.

• Distillate Hydrotreater unit desulfurizes the distillates (such as

diesel) after the atmospheric distillation.

• Fluid Catalytic Cracker (FCC) unit upgrades the heavier fractions

into lighter, more valuable products.

• Hydrocracker unit uses the hydrogen to upgrade the heavier

fractions into lighter, more valuable products.


37

• Visbreaking unit upgrades the heavy residual oils by thermally

cracking them into lighter, more valuable reduced viscosity products.

• Merox unit treats the LPG, kerosene or jet fuel by oxidizing

mercaptans to organic disulfides.

• Coking units (delayed coking, fluid coker, and flexicoker) process

the very heavy residual oils into gasoline and diesel fuel, leaving petroleum

coke as a residual product.

• Alkylation unit produces a high-octane component for gasoline

blending.

• Dimerization unit converts the olefins into higher-octane gasoline

blending components. For example, butenes can be dimerized into

isooctene which may subsequently be hydrogenated to form isooctane.

There are also other uses for dimerization.

• Isomerization unit converts the linear molecules to higher-octane

branched molecules for blending into gasoline or feeding to alkylation

units.

• Steam reforming unit produces the hydrogen for the hydrotreaters

or hydrocracker.

• Liquefied gas storage units for propane and similar gaseous fuels at

a pressure sufficient to maintain in liquid form. These are usually spherical

vessels or bullets (horizontal vessels with rounded ends).

• Storage tanks for crude oil and finished products, usually

cylindrical, with some sort of vapor emission control and surrounded by an

earthen berm to contain spills.

• Amine gas treater, Claus unit and tail gas treatment for converting

hydrogen sulfide from hydrodesulfurization into elemental sulfur.

• Utility units, such as cooling towers for circulating cooling water,

boiler plants for steam generation, instrument air systems for pneumatically

operated control valves and an electrical substation.


38

• Wastewater collection and treating systems consisting of API

separators, dissolved air flotation (DAF) units and some types of further

treatment (such as an activated sludge biotreater) to make such water

suitable for reuse or for disposal.(Beychok, 1967)

• Solvent refining units use the solvent, such as cresol or furfural to

remove the unwanted, mainly the asphaltenic materials, from the

lubricating oil stock (or diesel stock).

• Solvent dewaxing units remove the heavy waxy constituents

petrolatum from the vacuum distillation products (Alfredo, 2008).

2.4.1.4 Flow Diagram of Typical Refinery

The figure (2-1) is a schematic flow diagram of a typical oil refinery

that depicts the various unit processes and the flow of intermediate product

streams that occurs between the inlet crude oil feedstock and the final end

products. The diagram depicts only one of the literally hundreds of

different oil refinery configurations. The diagram also does not include any

of the usual refinery facilities providing utilities such as steam, cooling

water, and electric power as well as storage tanks for crude oil feedstock

and for intermediate products and end products.

There are many process configurations other than that depicted in

Fig.(2-1). For example, the vacuum distillation unit may also produce

fractions that can be refined into end products such as: spindle oil used in

the textile industry, light machinery oil, motor oil, and steam cylinder oil.

As another example, the vacuum residue may be processed in a coker unit

to produce petroleum coke.


39

Fig.(2-1) Flow Diagram of a Typical Oil Refinery (Alfredo, 2008).


40

2.4.1.5 Specialty End Products

These will blend various feedstocks, mix appropriate additives,

provide short term storage and prepare for bulk loading to trucks, barges,

product ships and railcars.

• Gaseous fuels, such as propane stored and shipped in liquid form

under pressure in specialized railcars to the distributors.

• Liquid fuels blending (producing automotive and aviation grades of

gasoline, kerosene, various aviation turbine fuels and diesel fuels, adding

dyes, detergents, antiknock additives, oxygenates and anti-fungal

compounds as required). They may be shipped by barge, rail, tanker ship

and regionally in dedicated pipelines to point consumers, particularly

aviation jet fuel to major airports, or piped to distributors in multi-product

pipelines using product separators called pipeline inspection gauges

("pigs").

• Lubricants (light machine oils, motor oils and greases, adding

viscosity stabilizers as required) usually shipped in bulk to an offsite

packaging plant.

• Wax (paraffin) used in the packaging of frozen foods, among

others. may be shipped in bulk to a site to prepare as packaged blocks.

• Sulfur (or sulfuric acid), byproducts of sulfur removal from the

petroleum which may have up to a couple percent sulfur as organic sulfur-

containing compounds. Sulfur and sulfuric acid are useful industrial

materials. Sulfuric acid is usually prepared and shipped as the acid

precursor oleum.

• Bulk tar shipping for offsite unit packaging for use in tar-and-

gravel roofing.

• Asphalt unit, prepares the bulk asphalt for shipment.

• Petroleum coke, used in specialty carbon products or as a solid fuel.


41

• Petrochemicals or petrochemical feedstocks which are often sent to

the petrochemical plants for further processing in a variety of ways. The

petrochemicals may be olefins or their precursors, or various types of

aromatic petrochemicals (Alfredo, 2008).

2.4.1.6 Siting/Locating of Petroleum Refineries

The principles of finding a construction site for refineries are similar

to those for other chemical plants:

• The site has to be reasonably far from residential areas.

• Facilities for raw materials access and products delivery to markets

should be easily available.

• Processing energy requirements should be easily available.

• Waste product disposal should not cause difficulties.

For refineries which use large amounts of process steam and cooling

water, an abundant source of water is important. Because of this, oil

refineries are often located (associated to a port) near navigable rivers or

even better on a sea shore. Either is of dual purpose, making also available

cheap transport by river or by sea. Although the advantages of crude oil

transport by the pipeline are evident, and the method is also often used by

oil companies to deliver large output products, such as fuels to their bulk

distribution terminals, the pipeline delivery is not practical for small output

products. For these, rail cars, road tankers or barges may be used.

It is useful to site refineries in areas where there is abundant space to

be used by the same company or others, for the construction of

petrochemical plants, solvent manufacturing (fine fractionating) plants

and/or similar plants.

The reason is to allow easy access to large output refinery products

for further processing, or plants that produce chemical additives that the


42

refinery may need to blend into a product at source rather than at blending

terminals (Alfredo, 2008).

2.4.1.7 Safety and Environmental Concerns

The refining process releases numerous different chemicals into the

atmosphere. Consequently, there are substantial air pollution emissions,

and a notable odor normally accompanies the presence of a refinery. Aside

from air pollution impacts, there are also wastewater concerns, (Beychok,

1967) risks of industrial accidents, such as fire and explosion, and noise

health effects due to industrial noise.

The public has demanded from many governments to place restrictions on

the contaminants that refineries release, and most refineries have installed

the equipment needed to comply with the requirements of the pertinent

environmental protection regulatory agencies.

2.5 Previous Studies Concerning of Heavy Metals

A brief review of works published about soil contamination is

presented below:

Hana and Al-Hilali, (1986) analyzed (720) soil samples to

determine the contents of (Cr, Ni, Zn, Pb, Cu and V) elements in the soil of

Mesopotamian plain, Iraq. The authors concluded that the Mesopotamian

plain sediments are relatively free from pollution of time being. The results

have also shown that a geochemical differentiation between various

sedimentary soil units within the Mesopotamian plain is possible.

Al-Kendy, (2005) measured the lead concentration in the soil at (0, 8

and 15 m) from both the eastern and western sides of Mohammed Al-

Kasim highway road in the east of Baghdad city. The results ranged

between (20-4550 µg/g) for (48) samples. The study proves the fact that the

concentrations of lead decrease with distance from the edge of the


43

highway, and this agrees with previous studies. The pH results of the study

area were ranged between (6.9-8.2), and the organic content ranged

between (11.6-38.8 %). For the same study, lead measured at four sites in

Baghdad as an environmental background, the arithmetic mean was (19.75

µg/g) and the results were (20.5 µg/g in Al-Husseinyah, eastern north of

Baghdad; 19.5 µg/g in Al-Taji, western north of Baghdad; 21 µg/g in Al-

Kamaliyah, eastern south of Baghdad; 18 µg/g in Al-Sweeb, western south

of Baghdad).

UNEP, (2005) studied a selective hot spots region in Iraq, such as

Al-Qadissiya, Al-Suwaira, Khan Dhari, Al-Mishraq, Ouireej to determine

the qualitative and quantitative pollution of air, water and soil and their

effects on the environment. The results of laboratory and field tests have

shown that the soil and water are contaminated with heavy metals,

hydrocarbons and other parameters. The study also specifies the

approximate concentrations of each contaminant.

Al-Maliky, (2005) constructed maps to explain the zones of

distributions and concentrations of pollutants in air, water and soil of

Baghdad city. These maps were constructed depending on an integrated

measured and collected data base utilizing a GIS and Arcview software.

The concentrations of air pollutants, such as TSP, Pb, Co, SO2 and HC

were measured, and the obtained results have shown that TSP levels

exceede the standard level of pollution. The water quality of Tigris River

was also studied by testing the physical and chemical properties (electrical

conductivity, TDS, TSS and total hardness) of 13 water samples. In

addition to air and water, Al-Maliky tested the concentration of heavy

metals (Zn, Cu, Co, Ni and Cd) in trace elements of Baghdad soil and

concluded that Baghdad city soil is contaminated with low percentages of

Co, Cd, Ni and Cu.


44

Kaur and Rani, (2006) presented detailed spatial information on

bio-available heavy metal concentrations in the soil and surface/sub surface

water by testing of 144 randomly selected samples in the study area of

(Delhi). This information was based on the actual soil/water surveys,

standard laboratory methods and GIS techniques. The ESP values together

with EC and pH values were then used for assessing the quality of the

tested soil samples. In addition, Cu, Fe, Mn, Zn, Cd, Cr, Ni and Pb

concentrations were also estimated. Then, the map of the tested area was

digitalized in an Arc-View spatial Analyst-GIS software to characterize the

regional distribution of physico-chemical characteristics of the soil/waters.

They concluded that the generated maps for each trace metal can be used

for understanding the spatial distribution, type and extent of heavy metal

pollution in the soils and surface/sub surface waters.

Neupane, (2006) examined the concentration of As, Cr, Cu, Ni, Pb

and Zn in arable and forest soils near Pemberville, Ohio in (60) soil

samples obtained from (10) sites. The soil samples contain a large

proportion of fines (32% clay and 37% silt). The soil samples were

digested according to EPA 3050B method and analyzed for heavy metals

with ICP-AES. The results of tests prove that the variations of heavy metal

contents in the layer from the surface to 50 cm depth are as follows: As

increased from (4.6 to 11) mg/kg, Cr increased from (19 to 23) mg/kg and

Ni increased from (21 to 25) mg/kg. While, the content of Cu decreased

from (27 to 17) mg/kg, and Pb content decreased from (16 to 10) mg/kg

respectively

Sahib, (2007) measured the lead concentrations in (16) testing

locations in different districts of Baghdad city, and the soil samples were

taken from the gardens of school which lies the chosen districts to represent

the environment of these districts and their conditions. The samples were

taken at four depths (0, 10, 20 and 30 cm from the soil surface) for each


45

district. The results ranged between (28-1865 µg/g) for all soil samples.

The pH values in this study ranged between (6.8- 8.2), the organic content

results ranged between from (4.5-19.8 %) and the organic matter was

noticed to accumulate at the top layers of the soil and decreased with depth.

Salman, (2007) measured the concentrations of heavy metals (Pb,

Ni, Co, Cd, Cu, Fe and Cr) in several ecological components, (soil, surface

water, palm fronds ash, dust and molluscan Shells) in Al-Basra Province.

Salman also indicated the probable sources of pollution and proposed the

proper remediation methods as well as comparing the concentrations of

heavy metals in the studied ecological components with the local and

international standards. The obtained results have shown increasing in the

concentrations of some heavy metals (Pb, Co, Cd and Cr) in the studied

ecological components and decreasing in others (Ni, Cu, Fe) as compared

with the local and world standards. The main reason for increasing the

concentrations of heavy metals in several ecological components in Al-

Basra province is the anthropogenic activities, like the disposal of sewage

water and domestic wastes, and the industrial wastes, especially from the

oil industries in the west of Al-Basra.

Barbooti et al., (2008) intended to assess the environmental effects

of the operations of Al-Daura refinery on the land and water environment.

An overview of the site was first performed using a specially designed

Environmental Site Assessment (ESA) checklist. Soil samples were

collected at various depths from almost all locations inside the refinery.

The performance of the wastewater treatment system was evaluated.

Samples of rain water accumulated in ponds were collected and analyzed.

For evaluation of the ground water quality and the nature of soil layers, a

monitoring well drilled in the vicinity of a wide dumping area of heavy

untreatable materials. Water samples were taken from this well for several

weeks period. Some field tests were carried out to evaluate the hydrocarbon


46

in soil, dissolved oxygen (DO), pH and electrical conductivity (EC) for

water. Laboratory analysis on water and soil included heavy metal

determination in soil extracts, such as (V, Ni and Pb) and types of

hydrocarbon pollutants in water and soil samples. Oil content

determinations as well as other routine analysis were carried out on water

samples to indicate any possible hydrocarbon pollution of the ground

water. The assessment of heavy metals concentration is that the danger

from these metals is limited due to their insolubility in water.

Zhang et al., (2009) studied the effect of the land use and soil

properties on the total and available concentration of Cu by using a

correlation and analysis of variance (ANOVA) in China. A total of 276

surface soil samples were collected from seven land uses. For each soil

sample, the total and available concentration of Cu, pH, organic matter,

total nitrogen and cation exchangeable capacity were measured. This study

also included drawing a probability map for the grains Cu that exceed 10

mg/kg by using ArcGIS software. The analyses have shown that the land

use has significant effects on Cu concentration and soil properties,

especially the total nitrogen and pH.

Chapter Three: Field and Experimental Work

47

Chapter Three

Field and Experimental Work

3.1 Introduction

This chapter includes the description of the field and experimental

work that took place and a description of the location, at which this work

was applied. The experimental work of this study consisted of measuring of

some characteristics of soil samples as well as the measurement of heavy

metals level in these samples. While the field works consist of collecting

soil samples from representative areas inside and outside the refinery.

Finally, a brief description for the instruments and chemical

materials used in the experimental work has been also reviewed.

3.2 Al-Daura Refinery

Al-Daura refinery which is one of the refineries operated by the

Midland Refineries Company (MRC), is located to the south east, just 4

Km from the city centre of Baghdad, close to the western bank of Tigers

river (Fig.(1-1) (p.4) shows Al-Daura refinery location in Baghdad).

It occupies an area with nearly (1,011,714 m2). Al-Daura refinery is the

oldest and largest one in Iraq and marks the true beginning of the modern

oil refinery industry (Afaj and Al-Khashab., 2007). It was constructed at

1953 by major oil companies, like Fortes Wheeler, M. W. Kellog and

Exxon research and engineering. The refinery was developed and expanded

from 1956 to 2004 by many companies, such as the Italian, Japanese,

Yugoslavian, Germany and American companies to include different new


48

units and plants. About more than 5000 workers work in different

departments of the refinery.

Al-Daura refinery consists of three main processes departments which

are:

1. Light oil department.

2. Lube oil department.

3. Power and utilities department.

In addition to ten services department, such as Maintenance and

Mechanical, Safety and Fire Fighting, Studies and Engineering, Research

and Quality Control, Training and Development, Environment,

Accounting, Stores and Purchasing, Personal and Administration.

Al-Daura refinery receives an average amount of 100,000 m3/day or 36

million m3/year, which is equal to 12.6 million ton/year of crude oil from

different oil fields in Basra, Naft Khana, Kirkuk in addition to oil fields of

East Baghdad to produce in different separation techniques, such as

physical, thermal and chemical. Their several components include fuel and

nonfuel products, such as liquid petroleum gas LPG, Gasoline, Kerosene,

Jet Fuel, Gas Oil, Diesel Oil, Lubricating Oils and Asphalt of different

grades. Approximately more than 95% of the petroleum products of Al-

Daura oil refinery are fuel products.

About 100,000 m3 of crude oil from different origins will be blended as

a mixture, this blended crude oil produces some products, like Liquid

petroleum gas LPG, Kerosene, Jet Fuel, Gas Oil, Gasoline and Heavy Fuel

Oil.

The Reduced Crude (R.C.) of the refining possesses in Light Oil

department will be provided and sent out to the Lube Oil department. Its

amount ranges to about 2,100 m3/d, where the other amount of R.C. can be


49

supplied to the power station out the refinery, like Al-Daura Power Plant

and South Baghdad Power Plant. Also, about 350 m3/d of R.C. will be

supplied to the Power and Utilities department. The main products in the

Lube Oil department are Lubricating Oil, Greases, Waxes and Asphalt of

different grades.

3.3 Location of Samples

The selected locations of samples were as follows: (1) ten locations

outside the refinery, and (2) seven locations inside it, as shown in the

Fig.(1-2) (p.5), those locations were chosen according to security

conditions during samples collection and determinants of site.

These sample locations might reflect the heavy metals pollution arising

from the oil refinery activities in all directions. Other one location was

chosen in a rural (control) area, in the University of Baghdad, to compare

between the heavy metals concentration in the study area and a sample

from the rural area not affected by the pollution.

3.4 Sampling Process

The soil samples were taken from a 5 cm depth from the top surface

of the soil used for chemical tests and physical properties for the soil, and

at 60 cm depth by using auger (maximum depth can auger be reached about

60 cm). Three samples were taken from each depth for each location to

take an average of results.

The plant samples were taken from all location in Fig.(1-2) (p.6).


50

All the samples were taken during the period from Dec/2010 to

Feb/2011, and collected in labeled sacks and transported directly to the

laboratory.

The coordinates of all locations for samples were also taken by using

a geographic position system (GPS) instrument type GARMIN.

3.5 Laboratory Tests

3.5.1 Physical Tests of Soil

The following soil characteristics were measured for each sample from

each testing location:

1. Organic Content.

2. pH Value Measurement.

3. Soil Classification:

Specific Gravity.

Grain Size Analysis.

Atterberg Limits (Liquid Limit & Plastic Limit).

All physical tests were conducted in the Soil laboratory at the University

of Technology.

3.5.1.1 Organic Content Measurement

The objective of the organic content measuring is to calculate the

amount of organic matters in soil samples according to (Rcsp, 1988).

The procedure of measuring organic content was executed by taking (5 gm)

of dried ground soil and placed in a burning furnace to 550 oC for 2 hours.


51

The organic content percentage can be then calculated by applying

the following equation:

………. (3-1)

Where:

OC %: organic content percentage.

Ww: wet weight of soil sample before burning (gm).

Wd: dry weight of soil sample after burning (gm).

W: weight of dried ground soil = 5 gm.

3.5.1.2 pH Value Measurement

The approach of this measurement was performed according to

(Rayment and Higginson, 1992).

The procedure of measuring the (pH) value is as follows:

1. The pH value was determined as 1:5 soil: distilled water suspension,

by taking 20 gm of dry ground soil: 100 ml of distilled water.

2. The suspension was shaken using a mechanical stirrer for one hour at

15 rpm.

3. The suspension was filtered with filtering papers.

4. The electrode of pH meter was immersed into the filtered sample,

and the pH value was recorded.


52

3.5.1.3 Soil Classification

Specific Gravity (Gs): The Specific gravity for all soil samples were

tested according to (BS: 1377, 1975, Test 6B).

Grain Size Analysis: The soil samples were tested according to

ASTM (D422).

Atterberg Limits: The soil samples were tested according to (BS:

1377, 1975, Test 2B) for liquid limit and (BS: 1377, 1975, Test 3)

for plastic limit.

3.5.2 Chemical Laboratory Test of Soil

The chemical laboratory test includes finding the concentrations of

heavy metals, such as Zinc (Zn), Nickel (Ni), Lead (Pb) and Cadmium (Cd)

by using Atomic Absorption Spectrometry (AAS) device. This device was

adopted in this work, and the chemical extraction was prepared in the

laboratories of the Central Agency for Standardization and Quality Control

in the Ministry of Planning.

The procedure of chemical extract preparation was as follows:

(Jardoa and Nickless, 1989).

1. All samples were dried in a drying oven to 105 oC for 24 hours.

2. All samples were ground and sieved with 105 mesh sizes.

3. A (1 gm) from the sieved soil was extracted with 10 ml of

concentrated HNO3 acid (Analar nitric acid) on a hot plate for

heating till the volume reached 2 ml, then the sample (extracted

sample) was left to stand 2 hours.

4. After that, the sample was first diluted with distilled water twice, and

then, the sample was filtered on Whatman 541 papers, and finaly, a


53

second dilution was made for the sample with distilled water for 25

ml volume.

Then the sample placed in the Atomic Absorption Spectrophotometer

(AAS) to measure the heavy metals concentrations.

The results obtained from the AAS were in (mg/L) and to convert these

results to (µg/g), the following formula has been applied: (Karnoob, 1986)

………. (3-2)

Where:

Y: heavy metals concentration in soil sample (µg/g).

X: heavy metals concentration obtained from AAS instrument (mg/L).

V: sample volume used in the AAS = 25 ml.

I: dilution factor.

W: weight of soil extracted = 1 gm.

3.5.3 Chemical Laboratory Tests of plants

The chemical laboratory test for plants (seasonal vegetable) includes

finding the concentrations of Zn, Ni, Pb and Cd by using the Atomic

Absorption Spectrometry (AAS) method. The chemical extraction was

prepared in the same laboratories of the Central Agency for Standardization

and Quality Control in the Ministry of Planning.


54

The plants samples were taken from the field (the whole plant with

its roots) and placed in plastic sacks and then transported to the lab to run

the tests on them.

The procedure of chemical extract preparation was as follows:

(Haswel, 1990)

1. The plant samples were first washed with distilled water and

then dried completely.

2. Cutting the sample into small pieces and taking 2 gm from it.

3. Adding 40 mL from nitric acid (HNO3) and covering the

sample for one night to soak.

4. Heating the sample until appearance of steam and left to cool.

5. Adding 3 mL from berchloric acid (HClO4) and heating the

sample with opening cover until dried.

6. Leaving the residual for cooling, then adding 2 mL from

hydrochloric acid (HCl) with 2-3 mL distilled water and

heating the sample until the residual dissolved.

7. Cooling and filtering the sample, rinsing the filtered one with

distilled water to 50 mL, and then the sample was ready to

analysis by Atomic Absorption Spectrometry (AAS).

3.6 Apparatuses Used in All Experiments

The apparatuses used were:

1. Atomic Absorption Spectrophotometer.

Type: SHIMADSU AA6300

Use: Detection for the heavy metals concentration levels in soil and

plants extracts.


55

2. Geographic Position System (GPS).

Type: GARMIN

Model: rino 120

Use: Determination for the coordinate of the samples location.

3. Digital indicator balance with a range of (0.0001-220.0000 gm).

4. Digital indicator balance with a range of (0.01- gm).

5. Drying oven with a maximum temperature degree of 200 oC.

6. Burning furnace for burning soil to 550 oC.

7. Casagrande device.

8. Hydrometer H-152.

9. Pycnometer.

10. Set of sieves.

11. Auger and shovel.

Chapter Four: Results and Discussion

56

Chapter Four

Results and Discussion

4.1 Introduction

This chapter includes the results of the experimental work for both

heavy metals and soil characteristics, beside the statistical analysis for these

results. The relationship between the heavy metals concentrations and the

soil characteristics has been also introduced, analyzed and discussed.

4.2 Heavy Metals Concentration Results in Soil

Heavy metals concentrations levels were measured in soil samples

which were taken from the testing locations at different depths (5 and 60

cm from soil surface).

The total results of heavy metals concentration are listed in tables

(4-1) to (4-8).


57

Table (4-1) The Results of Zinc Concentrations and Soil Characteristics

Outside the Refinery Location. S

am

ple

No.

Position Depth

(cm)

Av. Zn con.

(µg/g)

[Mean

Allow. Val.

(50 µg/g)]

Ratio

Ratio

OC% pH Clay

% East North

1 447921.8 3681095

5 71.1 1.422 5.182 13.45 7.6 20.5

60 52.7 1.054 3.841 8.62 7.3

2 447640.5 3681216

5 40.2 0.804 2.930 12.2 7.3 12.3

60 47.6 0.952 3.469 9 6.9

3 448271.5 3682971

5 35.2 0.704 2.566 6 7.8 2.15

60 62.6 1.252 4.563 6.04 7.5

4 447674.1 3683174

5 62.5 1.25 4.555 7.54 8.1 15.5

60 58.8 1.176 4.286 5.87 7.8

5 446309.7 3682524

5 54.2 1.084 3.950 5.91 6.9 13

60 29.7 0.594 2.165 3.36 7

6 446695.6 3682706

5 59 1.18 4.300 11.87 7.2 18

60 52.1 1.042 3.797 7 7.1

7 444986.0 3682242

5 15 0.3 1.093 1.48 7.6 1.7

60 16.5 0.33 1.203 1.35 7.7

8 445361.1 3681741

5 33.8 0.676 2.464 8.29 7 1.85

60 60 1.2 4.373 4.49 7.2

9 445429.1 3680757

5 42 0.84 3.061 9.34 7.2 14.3

60 41.5 0.83 3.025 4.5 7

10 445146.1 3680584

5 43.3 0.866 3.156 8.31 7.3 9

60 56.6 1.132 4.125 8.43 6.9

Note: All bold numbers in tables means that this value exceeded the mean allowable

value.


58

Table (4-2) The Results of Zinc Concentrations and Soil Characteristics

Inside the Refinery Location. S

am

ple

No.

Position Depth

(cm)

Av. Zn con.

(µg/g)

[Mean

Allow. Val.

(50 µg/g)]

Ratio

Ratio

OC% pH Clay

% East North

11 446569.8

3682261

5 101.8 2.036 7.420 6.65 7.4 43

60 51.2 1.024 3.732 4.1 7.1

12

447027.4

3682652

5 77.5 1.55 5.649 5.13 7.6 20

60 101.3 2.026 7.383 4.35 7.6

13

447144.6

3682469

5 60.9 1.218 4.439 4.2 7.8 8

60 48.7 0.974 3.550 4.54 7.7

14

447567.7

3681528

5 52.6 1.052 3.834 3.83 7.4 2.2

60 44.2 0.884 3.222 3.8 7.2

15

447075.4

3681779

5 66.8 1.336 4.869 6.68 8.1 22

60 50.2 1.004 3.659 5 7.8

16

447048.9

3682156

5 115.1 2.302 8.389 8.67 7.5 33

60 86.2 1.724 6.283 3.94 7.4

17

446751.8

3681911

5 128.9 2.578 9.400 9.26 7.8 35

60 76.2 1.524 5.554 4.68 7.4


59

Table (4-3) The Results of Nickel Concentrations and Soil Characteristics


am

ple

No.

Position Depth

(cm)

Av. Ni con.

(µg/g)

[Mean

Allow. Val.

(20 µg/g)]

Ratio

Ratio

OC% pH Clay

% East North

1 447921.8 3681095

5 117.4 5.870 4.278 13.45 7.6 20.5

60 94.8 4.740 3.455 8.62 7.3

2 447640.5 3681216

5 104.1 5.205 3.794 12.2 7.3 12.3

60 113.4 5.670 4.133 9 6.9

3 448271.5 3682971

5 89.2 4.460 3.251 6 7.8 2.15

60 136 6.800 4.956 6.04 7.5

4 447674.1 3683174

5 100.6 5.030 3.666 7.54 8.1 15.5

60 128.5 6.425 4.683 5.87 7.8

5 446309.7 3682524

5 95 4.750 3.462 5.91 6.9 13

60 54.5 2.725 1.986 3.36 7

6 446695.6 3682706

5 118.3 5.915 4.311 11.87 7.2 18

60 105 5.250 3.827 7 7.1

7 444986.0 3682242

5 30.6 1.530 1.115 1.48 7.6 1.7

60 37.3 1.865 1.359 1.35 7.7

8 445361.1 3681741

5 84.5 4.225 3.079 8.29 7 1.85

60 127.8 6.390 4.657 4.49 7.2

9 445429.1 3680757

5 107.4 5.370 3.914 9.34 7.2 14.3

60 91.3 4.565 3.327 4.5 7

10 445146.1 3680584

5 103.9 5.195 3.786 8.31 7.3 9

60 117.8 5.890 4.293 8.43 6.9


60

Table (4-4) The Results of Nickel Concentrations and Soil Characteristics


am

ple

No. Position

Depth

(cm)

Av. Ni

con.

(µg/g)

[Mean

Allow.

Val.

(20 µg/g)]

Ratio

Ratio

OC% pH Clay

% East North

11 446569.8 3682261

5 110.1 5.505 4.012 6.65 7.4 43

60 90 4.500 3.280 4.1 7.1

12 447027.4 3682652

5 106.1 5.305 3.867 5.13 7.6 20

60 145.5 7.275 5.302 4.35 7.6

13 447144.6 3682469

5 89 4.450 3.243 4.2 7.8 8

60 79.6 3.980 2.901 4.54 7.7

14 447567.7 3681528

5 90.8 4.540 3.309 3.83 7.4 2.2

60 85.6 4.280 3.120 3.8 7.2

15 447075.4 3681779

5 120.9 6.045 4.406 6.68 8.1 22

60 103.9 5.195 3.786 5 7.8

16 447048.9 3682156

5 124.4 6.220 4.534 8.67 7.5 33

60 97 4.850 3.535 3.94 7.4

17 446751.8 3681911

5 116.2 5.810 4.235 9.26 7.8 35

60 104.3 5.215 3.801 4.68 7.4


61

Table (4-5) The Results of Lead Concentrations and Soil Characteristics


am

ple

No.

Position Depth

(cm)

Av. Pb con.

(µg/g)

[Mean

Allow. Val.

(28 µg/g)]

Ratio

Ratio

OC% pH Clay

% East North

1 447921.8 3681095

5 13 0.464 26.0 13.45 7.6 20.5

60 10.8 0.386 21.6 8.62 7.3

2 447640.5 3681216

5 9.9 0.354 19.8 12.2 7.3 12.3

60 7.3 0.261 14.6 9 6.9

3 448271.5 3682971

5 7.5 0.268 15.0 6 7.8 2.15

60 8 0.286 16.0 6.04 7.5

4 447674.1 3683174

5 6 0.214 12.0 7.54 8.1 15.5

60 14 0.500 28.0 5.87 7.8

5 446309.7 3682524

5 6 0.214 12.0 5.91 6.9 13

60 3.5 0.125 7.0 3.36 7

6 446695.6 3682706

5 9.5 0.339 19.0 11.87 7.2 18

60 8.3 0.296 16.6 7 7.1

7 444986.0 3682242

5 2.8 0.1 5.6 1.48 7.6 1.7

60 5 0.179 10.0 1.35 7.7

8 445361.1 3681741

5 9.7 0.346 19.4 8.29 7 1.85

60 5.7 0.204 11.4 4.49 7.2

9 445429.1 3680757

5 8.4 0.300 16.8 9.34 7.2 14.3

60 4.9 0.175 9.8 4.5 7

10 445146.1 3680584

5 4.3 0.154 8.6 8.31 7.3 9

60 3.8 0.136 7.6 8.43 6.9


62

Table (4-6) The Results of Lead Concentrations and Soil Characteristics


am

ple

No.

Position Depth

(cm)

Av. Pb con.

(µg/g)

[Mean

Allow. Val.

(28 µg/g)]

Ratio

Ratio

OC% pH Clay

% East North

11 446569.8 3682261

5 64.4 2.300 128.8 6.65 7.4 43

60 7.9 0.282 15.8 4.1 7.1

12 447027.4 3682652

5 5.1 0.182 10.2 5.13 7.6 20

60 7.2 0.257 14.4 4.35 7.6

13 447144.6 3682469

5 1.45 0.052 2.9 4.2 7.8 8

60 0.5 0.018 1.0 4.54 7.7

14 447567.7 3681528

5 1.4 0.050 2.8 3.83 7.4 2.2

60 0.7 0.025 1.4 3.8 7.2

15 447075.4 3681779

5 48.4 1.729 96.8 6.68 8.1 22

60 9.4 0.336 18.8 5 7.8

16 447048.9 3682156

5 6.8 0.243 13.6 8.67 7.5 33

60 2.7 0.096 5.4 3.94 7.4

17 446751.8 3681911

5 10 0.357 20.0 9.26 7.8 35

60 5.6 0.200 11.2 4.68 7.4


63

Table (4-7) The Results of Cadmium Concentrations and Soil

Characteristics Outside the Refinery Location. S

am

ple

No. Position

Depth

(cm)

Av. Cd

con.

(µg/g)

[Mean

Allow. Val.

(0.45 µg/g)]

Ratio

Ratio

OC% pH Clay

% East North

1 447921.8 3681095

5 0.03 0.067 3 13.45 7.6 20.5

60 1.22 2.711 122 8.62 7.3

2 447640.5 3681216

5 0.02 0.044 2 12.2 7.3 12.3

60 0.61 1.356 61 9 6.9

3 448271.5 3682971

5 0.01 0.022 1 6 7.8 2.15

60 0.24 0.533 24 6.04 7.5

4 447674.1 3683174

5 0.01 0.022 1 7.54 8.1 15.5

60 0.01 0.022 1 5.87 7.8

5 446309.7 3682524

5 0.02 0.044 2 5.91 6.9 13

60 0.25 0.556 25 3.36 7

6 446695.6 3682706

5 0.03 0.067 3 11.87 7.2 18

60 0.5 1.111 50 7 7.1

7 444986.0 3682242

5 0.02 0.044 2 1.48 7.6 1.7

60 0.02 0.044 2 1.35 7.7

8 445361.1 3681741

5 0.03 0.067 3 8.29 7 1.85

60 1.7 3.778 170 4.49 7.2

9 445429.1 3680757

5 0.01 0.022 1 9.34 7.2 14.3

60 0.02 0.044 2 4.5 7

10 445146.1 3680584

5 0.02 0.044 2 8.31 7.3 9

60 2.1 4.667 210 8.43 6.9


64

Table (4-8) The Results of Cadmium Concentrations and Soil

Characteristics Inside the Refinery Location. S

am

ple

No.

Position Depth

(cm)

Av. Cd con.

(µg/g)

[Mean

Allow. Val.

(0.45 µg/g)]

Ratio

Ratio

OC% pH Clay

% East North

11 446569.8 3682261

5 0.21 0.467 21 6.65 7.4 43

60 0.06 0.133 6 4.1 7.1

12 447027.4 3682652

5 0.06 0.133 6 5.13 7.6 20

60 2.31 5.133 231 4.35 7.6

13 447144.6 3682469

5 0.01 0.022 1 4.2 7.8 8

60 0.12 0.267 12 4.54 7.7

14 447567.7 3681528

5 0.05 0.111 5 3.83 7.4 2.2

60 0.07 0.156 7 3.8 7.2

15 447075.4 3681779

5 0.03 0.067 3 6.68 8.1 22

60 0.64 1.422 64 5 7.8

16 447048.9 3682156

5 0.04 0.089 4 8.67 7.5 33

60 0.07 0.156 7 3.94 7.4

17 446751.8 3681911

5 0.01 0.022 1 9.26 7.8 35

60 1.3 2.889 130 4.68 7.4

From previous tables, the concentrations results ranged as follows:

Zinc: From (15- 128.9 µg/g) at top soil.

From (16.5- 101.3 µg/g) at 60 cm from soil surface.

Nickel: From (30.6- 124.4 µg/g) at top soil.


Lead: From (1.4- 64.4 µg/g) at top soil.

From (0.5- 14 µg/g) at 60 cm from soil surface.

Cadmium: From (0.01- 0.21 µg/g) at top soil.


65


Tables (4-1) to (4-6) show that the concentrations of Zn, Ni and Pb,

with some exceptions, accumulate at the top soil and decrease with the

depth. This accumulation of heavy metals in top of soil is due to the

accumulation of organic matters at these layers which act as absorbent; this

fact has been proved before by (El-Ghawi et al., 2005). Also, the neutral

values of pH play an important role to keep the accumulation of heavy

metals at the top layers of soil, because at the neutral values of pH, Zn, Ni

and Pb have a strong relation with the soil solids, and hence its movement

towards the deeper layers will be limited or very slowly. This fact has been

proved by (Kabata-Pendias and Pendias, 1992).

Tables (4-7) and (4-8) indicate that the concentrations of Cd at the

top soil is less than in the 60 cm depth from top soil surface, this is because

the Cd goes readily to solution during the weathering (Kabata-Pendias and

Pendias, 1992).

The surface accumulation of heavy metals on the soil proved that the

atmospheric heavy metals are the main source of heavy metals in the soil.

The atmospheric heavy metals are transported to soil by dry and wet

deposition and are related with soil solids.

4.3 Distribution of Heavy Metals Concentrations in Soil

Zinc: The Zn concentration in the study area at the top soil varies

from (15- 128.9 µg/g) with a mean value of (62.4 µg/g). The observed

values have been reportedly higher than the common world average for

total Zn concentrations in soil (50 µg/g) (Alloway, 1995). It is also higher

than the mean concentrations of trace elements calculated on the world

scale for silty soil (60 µg/g) (Kabata-Pendias and Pendias, 1992).


66

At (60 cm) depth from soil surface, the Zn concentration varies from

(16.5- 101.3 µg/g) with a mean value of (55.1 µg/g). This mean value has

been higher than the common world average illustrated above.

This study indicates that (64.7%) of all soil samples contain zinc

concentration greater than the standard limit of zinc in soil; and (100%) of

all samples contain zinc concentration greater than (13.72 µg/g) which is

the zinc concentration in soil sample from the rural area.

The maximum concentrations of Zn inside the refinery were near the

old storage basins and in the center of refinery, and the maximum value

outside the refinery was near the expressway (Mohammed Al-Kasim),

which is agricultural area, because the main sources of Zn have been

reported as an agricultural use of sewage and composted materials and the

use of agrochemicals, such as fertilizers and pesticides (Alloway, 1995).

Some of the studies have also linked the high Zn levels to accumulation

from the traffic and industry input (Imperato et al., 2003) and also from the

vehicle emissions and tire and brake abrasion (Ward, 1990).

Rainfall was the main reason that makes the fluctuation in the path of

Zn concentration with soil depth, because the solubilization of Zn minerals

during weathering produces mobile Zn+2

, especially in acid, oxidizing

environments (Kabata-Pendias and Pendias, 1992).

The distribution of Zn levels at the top soil and 60 cm depth from

surface in the study area is illustrated in Fig.(4-1) and Fig.(4-2),

respectively.


67

Fig.(4-1) Distribution of Zinc at Top soil


68

Fig.(4-2) Distribution of Zinc at 60 cm Depth from Soil Surface


69

Nickel: The Ni content in the study area at the top soil varies from

(30.6- 124.4 µg/g) with a mean concentration of (100.5 µg/g). The

observed mean value is higher than the world average concentration of Ni

in soil, which is around (20 µg/g) (Alloway, 1995). These results exceed

the calculated world mean for silty soil (26 µg/g) (Kabata-Pendias and

Pendias, 1992).

At (60 cm) depth from soil surface, the Ni concentration varies from

(37.3- 145.5 µg/g) with a mean value of (100.7 µg/g). This value is also

exceeding the above mean values.

This study points out that (100%) of all soil samples contain nickel

concentration greater than the standard limit of nickel in soil; and (100%)

of all samples contain nickel concentration greater than (27.44 µg/g) which

is the nickel concentration in soil sample from the rural area.

Maximum concentrations of Ni inside the refinery were in the center

of refinery and near the flare, and the maximum value outside the refinery

was near the expressway (Mohammed Al-Kasim) and near to the flare. It is

evident that local solid waste litter and anthropogenic activities, such as

burning of fuel and residual oil contribute to the increase in Ni content in

the soil of the study area (Alloway, 1995).

Ni is easily mobilized during weathering. However, unlike Ni+2

is

relatively stable in aqueous solutions and is capable of migration over a

long distance, therefore, the Ni concentration path is with the soil depth are

fluctuated.

Figs.(4-3) and (4-4) show the distribution of Ni levels at the top soil and 60

cm depth from surface in the study area, respectively.


70

Fig.(4-3) Distribution of Nickel at Top soil


71

Fig.(4-4) Distribution of Nickel at 60 cm Depth from Soil Surface


72

Lead: The Pb content in the study area varies from (1.4- 64.4 µg/g)

at top soil with a mean value of (12.6 µg/g). The observed values are less

than the calculated world average of silty soil (28 µg/g) (Kabata-Pendias

and Pendias, 1992).

Also, the Pb contents at 60 cm depth from soil surface (0.5- 14 µg/g)

are less than the calculated world average value.

This study indicates that (6%) of all soil samples contain lead

concentration greater than the standard limit of lead in soil; and (97%) of

all samples contain lead concentration greater than (0.5 µg/g) which is the

lead concentration in soil sample from the rural area

The maximum concentrations of Pb inside the refinery were near the

power former unit, and the maximum values outside the refinery were at

samples near the road sides. Deposition related to the automobile emissions

and transportations sector, in general (considering the long residence time

of Pb), may be the major source of increase in Pb content (Chatterjee and

Banerjee, 1999; Madrid et al., 2002; Imperato et al., 2003).

Pb is reported to be the least mobile among the other heavy metals

(Kabata-Pendias and Pendias, 1992), therefore, the Pb content paths with

the depth of soil were less fluctuated among other heavy metals.

Figs.(4-5) and (4-6) depict the distribution of Pb levels at the top soil and

60 cm depth from surface in the study area, respectively.


73

Fig.(4-5) Distribution of Lead at Top soil


74

Fig.(4-6) Distribution of Lead at 60 cm Depth from Soil Surface


75

Cadmium: The Cd content in the study area varies from (0.01- 0.21

µg/g) at top soil with a mean value of (0.035 µg/g). The observed values

are less than the calculated world mean for silty soil (0.45 µg/g) (Kabata-


At (60 cm) depth from soil surface, the Cd concentration varies from

(0.01- 2.31 µg/g) with a mean value of (0.66 µg/g). This mean value has

been higher than the common world mean illustrated above.

This study shows that is (20.6%) of all soil samples contain cadmium

concentration greater than the standard limit of cadmium in soil; and

(82.35%) of all samples contain cadmium concentration greater than (0.01

µg/g) which is the cadmium concentration in soil sample from the rural

area.

The maximum concentrations of Cd inside the refinery were near the

flare, and the maximum values outside the refinery were at samples near

the roadsides, which were agricultural areas. Cadmium has a wide range of

uses in the industry (Volensky, 1990), and a significant source of Cd in

soils is the phosphate fertilizers (Kabata-Pendias and Pendias, 1992).

Among the other trace metals, Cd is known to be most mobile under

conditions of different soils (Kabata-Pendias and Pendias, 1992), therefore,

the concentration of Cd increases with soil depth.

Figs.(4-7) and (4-8) reveals the distribution of Cd levels at the top soil and

60 cm depth from surface in the study area, respectively.


76

Fig.(4-7) Distribution of Cadmium at Top soil


77

Fig.(4-8) Distribution of Cadmium at 60 cm Depth from Soil Surface


78

The results have shown that the concentrations of heavy metals

inside the refinery were higher than outside it, and they decrease with the

wind direction (Western North), and the areas in this direction were

agricultural areas without any industrial activities, their irrigation is from

the Tigres River. Therefore, the concentration of heavy metals is very low

in the top soil, and there is no clear effect from the refinery activities. In the

other hand, the southern side of the refinery has a high concentration,

which were also agricultural areas, because there are the expressway

(Mohammed Al-Kasim) and station of electrical generation (South

Baghdad) to the Eastern South side from the refinery.

4.4 Soil Characteristics Results and Their Relationship with Heavy

Metals Concentrations

4.4.1 Organic Content Results

The results of organic content (OC %) are listed in Table (4-1), these

ranges are as follows:

From (1.48- 13.45 %) at top soil.

From (1.35- 9 %) at 60 cm from soil surface.

The results of organic contents manifest that the organic content,

with few exceptions, decreases with the depth. That is due to the

accumulation of decomposed plants and hydrocarbons emitted from the

refinery in the top layers of soil.

The relationship between the organic content and heavy metals

concentrations at each depth are shown in Figs.(4-9) to (4-16). These

figures indicate that the heavy metals concentration increases at the high

organic content sites. That is because the organic matters play an important

role in heavy metals adsorption on soil solids and also absorption. That

agrees with the results obtained by (Alloway, 1995; Kabata-Pendias and


79

Pendias, 1992) when they found that the organic matters are an important

factor in adsorption and accumulation of heavy metals in soil.


80

Fig.(4-9) Organic Content Relationship with Zinc Concentration at top soil

for all the Testing Locations

Fig.(4-10) Organic Content Relationship with Zinc Concentration at 60cm

Depth for all the Testing Locations

0

20

40

60

80

100

120

140

0 2 4 6 8 10 12 14 16

Zn

con

. µ

g/g

Organic cont. %

0

20

40

60

80

100

120

0 1 2 3 4 5 6 7 8 9 10

Zn

Con

. µ

g/g

Organic cont. %


81

Fig.(4-11) Organic Content Relationship with Nickel Concentration at top

soil for all the Testing Locations

Fig.(4-12) Organic Content Relationship with Nickel Concentration at

60cm Depth for all the Testing Locations

0

20

40

60

80

100

120

140

0 2 4 6 8 10 12 14 16

Ni

con

. µ

g/g

Organic cont. %

0

20

40

60

80

100

120

140

160

0 1 2 3 4 5 6 7 8 9 10

Ni

con

. µ

g/g

Organic cont. %


82

Fig.(4-13) Organic Content Relationship with Lead Concentration at top


Fig.(4-14) Organic Content Relationship with Lead Concentration at 60cm

Depth for all the Testing Locations

0

10

20

30

40

50

60

70

0 2 4 6 8 10 12 14 16

Pb

con

. µ

g/g

Organic cont. %

0

2

4

6

8

10

12

14

16

0 1 2 3 4 5 6 7 8 9 10

Pb

con

. µ

g/g

Organic cont. %


83

Fig.(4-15) Organic Content Relationship with Cadmium Concentration at

top soil for all the Testing Locations

Fig.(4-16) Organic Content Relationship with Cadmium Concentration at

60cm Depth for all the Testing Locations

0

0.05

0.1

0.15

0.2

0.25

0 2 4 6 8 10 12 14 16

Cd

con

. µ

g/g

Organic cont. %

0

0.5

1

1.5

2

2.5

0 1 2 3 4 5 6 7 8 9 10

Cd

con

. µ

g/g

Organic cont. %


84

These results showed that there is a weak direct correlation;

therefore, one can’t be estimate the heavy metals concentration in soil

depending on the organic content percentage and at certain depth.

4.4.2 Soil pH Results

The results of pH values of the study area are listed in tables (4-1)

and (4-2). Generally, these results range from (6.9-8.1), and are close to

those measured by (Al-Zubaidy, 1978) when he found that pH values for

Iraqi soil ranged from (7-8) because of the high percent of CaCO3 and

CaSO4.H2O existing in Iraqi soil. Also, the measured pH values are close to

those measured by (Al-Kindy, 2005; Mohammed, 2006; Sahib, 2007),

which ranged from (6.9-8.2), (7.31-7.56) and (6.8-8.2), respectively.

Figs.(4-17) to (4-24) depict the relationship between the heavy

metals level and pH. It’s obvious that the accumulation of heavy metals on

soil solids increases with pH increasing except Cd.


85

Fig.(4-17) pH Values Relationship with Zinc Concentration at Top soil for

all the Testing Locations

Fig.(4-18) pH Values Relationship with Zinc Concentration at 60 cm depth


0

20

40

60

80

100

120

140

6.8 7 7.2 7.4 7.6 7.8 8 8.2

Zn

con

. µ

g/g

pH

0

20

40

60

80

100

120

6.8 6.9 7 7.1 7.2 7.3 7.4 7.5 7.6 7.7 7.8 7.9

Zn

con

. µ

g/g

pH


86

Fig.(4-19) pH Values Relationship with Nickel Concentration at Top soil


Fig.(4-20) pH Values Relationship with Nickel Concentration at 60 cm

depth for all the Testing Locations

0

20

40

60

80

100

120

140

6.8 7 7.2 7.4 7.6 7.8 8 8.2

Ni

con

. µ

g/g

pH

0

20

40

60

80

100

120

140

160

6.8 6.9 7 7.1 7.2 7.3 7.4 7.5 7.6 7.7 7.8 7.9

Ni

con

. µ

g/g

pH


87

Fig.(4-21) pH Values Relationship with Lead Concentration at Top soil for

all the Testing Locations

Fig.(4-22) pH Values Relationship with Lead Concentration at 60 cm depth


0

10

20

30

40

50

60

70

6.8 7 7.2 7.4 7.6 7.8 8 8.2

Pb

con

. µ

g/g

pH

0

2

4

6

8

10

12

14

16

6.8 6.9 7 7.1 7.2 7.3 7.4 7.5 7.6 7.7 7.8 7.9

Pb

con

. µ

g/g

pH


88

Fig.(4-23) pH Values Relationship with Cadmium Concentration at Top


Fig.(4-24) pH Values Relationship with Cadmium Concentration at 60 cm

depth for all the Testing Locations

0

0.05

0.1

0.15

0.2

0.25

6.8 7 7.2 7.4 7.6 7.8 8 8.2

Cd

con

. µ

g/g

pH

0

0.5

1

1.5

2

2.5

6.8 6.9 7 7.1 7.2 7.3 7.4 7.5 7.6 7.7 7.8 7.9

Cd

con

. µ

g/g

pH


89

These results manifested that there is a weak direct correlation

between Zn, Ni and Pb, and pH value; but there is a weak inverse

correlation between the Cd and pH, and this fact agrees with (Kabata-


4.4.3 Clay Percent Results

All the results of soil properties are given in table (4-9) for each

testing location.

The relationship between the heavy metals concentrations in the

study area and soil type showed that most of the highly polluted location

soils contain a high percent of clay in their compositions. The overall

behavior of heavy metals in soil is said to be governed largely by their

sorption and desorption reactions with different soil constituents, especially

clay components (Appel and Ma, 2002).

Figs.(4-25) to (4-28) illustrate the relationship between the heavy metals

level and clay percent.


90

Table (4-9) Characteristics of Soil Sample.

Sample

no. G% S% M% C% Organic% Gs L.L% P.L%

Unified

class.

1 0 2 77.5 20.5 9.76 2.52 44.65 24.19 Cl

2 0 0.5 87.2 12.3 7.22 2.63 45.61 23.15 Cl

3 0.4 4.8 92.65 2.15 6.62 2.52 42.12 23.13 Cl

4 2.9 9.6 72 15.5 5.52 2.75 33.3 20.1 Cl

5 0.4 11 75.6 13 5.9 2.66 40.1 19.87 Cl

6 22.75 8.25 51 18 5.06 2.67 37.3 22.1 Cl

7 0.24 81.76 16.3 1.7 1.52 2.63 Np. Np. SP.

8 1.56 17.44 79.15 1.85 5.98 2.67 32.14 21.13 Cl

9 13 13.5 59.2 14.3 6.08 2.52 35.95 20.84 Cl

10 23.35 16.8 50.85 9 4.12 2.67 32.9 19.3 Cl

11 0.02 5.98 50 43 4.94 2.74 31.8 19.8 Cl

12 0.32 7.68 72 20 5.86 2.74 34.1 20.1 Cl

13 0.88 25.12 66 8 8.84 2.75 31.6 19.27 Cl

14 0.22 2.78 94.8 2.2 9.16 2.54 45.2 23 Cl

15 1.3 29.7 47 22 4.26 2.65 31.68 16.62 Cl

16 2.34 8.9 55.76 33 4.64 2.71 35.3 21.1 Cl

17 2 14.15 48.85 35 3.96 2.70 31.8 18.8 Cl


91

Fig.(4-25) Clay Percent Relationship with Zinc Concentration

Fig.(4-26) Clay Percent Relationship with Nickel Concentration

0

20

40

60

80

100

120

140

0 5 10 15 20 25 30 35 40 45 50

Zn

con

. µ

g/g

Clay %

0

20

40

60

80

100

120

140

0 5 10 15 20 25 30 35 40 45 50

Ni

con

. µ

g/g

Clay %


92

Fig.(4-27) Clay Percent Relationship with Lead Concentration

Fig.(4-28) Clay Percent Relationship with Cadmium Concentration

0

10

20

30

40

50

60

70

0 5 10 15 20 25 30 35 40 45 50

Pb

con

. µ

g/g

Clay %

0

0.05

0.1

0.15

0.2

0.25

0 5 10 15 20 25 30 35 40 45 50

Cd

con

. µ

g/g

Clay %


93

These previous figures showed that there is a weak direct correlation;

therefore, one can’t estimate the heavy metals concentration in soil

depending on the clay percentage in the soil.

4.5 Heavy Metals Concentration Results in Plants

The concentrations of plants heavy metals suggest that the plant

factors, differences in metal characteristics and differences in soil physical

and chemical properties can influence the variations of metals in plants.

The results of heavy metals concentration of the plants (seasonal

vegetable) in the study area are listed in table (4-10). Generally, these

results show a high concentration of Pb in the study area for many samples.

The permissible value of heavy metals in the plant for the WHO standards

is (Zn=100; Ni=67; Pb=0.3; Cd=0.1 µg/g). The mean value of Pb is (8.12

µg/g), the increases in the Pb concentrations might be resulted from the

growth of the plants in the polluted soil with Pb even when the

concentration in the soil is within permissible limits; these facts show a

high ability for the plants to absorb the Pb from soil, and there is a danger

when the agriculture in the area is polluted with Pb.

Lead is one of the hazardous metals that can transport to the humans

and animals through the chain food and accumulate in the body, causing a

physiological damage.

The mean value of Zn is (44.4 µg/g), and this value is less than the

WHO standards value. Zn is needed by plants as principle micro essential

elements. This may be the reason for their high level of accumulation by

plant species. According to Cunningham and Saigo (2001), plant cells have

mechanisms for bioaccumulation, selective absorption and storage of a


94

great variety of molecules. This allows them to accumulate nutrients and

essential minerals. Apart from being a cytochrome constituent, Zn is

associated with the auxin which is a plant growth hormone (Humphreys,

1987).

Table (4-10) The Results of Heavy Metals Concentration in the Plants at

Study Area Locations.

Sa

mp

le

No

.

Position Zn con.

(µg/g) [Permis. Val.

(100 µg/g)]

Ni con.


(67 µg/g)]

Pb con.


(0.3 µg/g)]

Cd con.


(0.1 µg/g)] East North

1 447921.8 3681095 8.6 0.85 15 0.008

2 447640.5 3681216 10.71 0.8 0.23 0.003

3 448271.5 3682971 38.2 0.5 14.1 0.005

4 447674.1 3683174 35.8 0.62 0.15 0.001

5 446309.7 3682524 2.57 0.52 0.05 0.004

6 446695.6 3682706 32.16 0.58 0.07 0.003

7 444986 3682242 26.75 0.1 0.1 0.001

8 445361.1 3681741 13.11 0.34 0.3 0.008

9 445429.1 3680757 24.37 0.45 5.254 0.001

10 445146.1 3680584 29.5 0.64 4.955 0.01

11 446569.8 3682261 29.2 0.93 24.01 0.04

12 447027.4 3682652 50.6 0.86 0.2 0.01

13 447144.6 3682469 47.7 0.15 9.7 0.008

14 447567.7 3681528 99.9 0.21 0.03 0.006

15 447075.4 3681779 99.9 0.9 29.6 0.009

16 447048.9 3682156 77.9 0.78 19.5 0.007

17 446751.8 3681911 127.9 0.87 14.8 0.002


95

4.6 Summary of the Results Analysis

In general, most of the heavy metals in soil accumulate from the

deposition of atmospheric heavy metals on top soil, and its mobility inside

the soil will depend upon the characteristics of soil itself.

From the results obtained in this research, most concentrations of

heavy metals are decreased with the depth of sampling point (except

cadmium). That means the heavy metals accumulates at the top layers of

soil, and this accumulation is due to the heavy metals in its immobile phase

at the measured value of pH (6.9-8.1). These are the values, at which the

soil particles act as adsorbents for heavy metals; because of the heavy rain

during the last winter, the Cd goes readily into solution and, although

known to occur Cd+2

during the weathering.

The organic content has a significant effect on the heavy metals

accumulation in soil. The complexation and chelating reactions occur

between the organic matters and heavy metals in neutral values of pH due

to the formation of bonds between the heavy metals and organic matters,

and hence the heavy metals movement will be very slow in soil.

Increasing and decreasing soil pH influence the chemical reactions in

the soil. Chemical elements in the soil are more adsorbed on the finest soil

particles (colloids) which are clay and humus. Although they are small in

size, colloids play a major influence in soil properties. They are

electronegative and have a large surface area. These two properties make

them highly reactive and adsorptive, and therefore, greatly influence the

cation exchange capacity of the soil. Soil acidification tends to increase the

desorption of basic cations (calcium, magnesium, potassium, sodium and

heavy metals) from the colloids, as they are replaced by hydrogen ions.

From table (4-9), the hydrometer test shows a high percent of silt in

the soil composition, but the results obtained from the Unified

classification, that depended on liquid limits (L.L) and plasticity index


96

(P.I), indecate a high percent of clay; these differences are because the

heavy metals bond with clay particles and make them coarser particles that

precipitate faster than clay particles.

In the plants, the heavy metals concentration reveals a trace concentration

of Ni and Cd; high concentrations of Pb with moderate levels of Zn. The

high levels of Pb mean the study area is not suitable for agriculture food

crops because the adverse effect of lead to the human and animals.

Chapter Five: Conclusions and Recommendations

97

Chapter Five

Conclusions and Recommendations

5.1 Conclusions

Based on the results, the conclusions from this work can be

summarized in the following items:

1. Zn, Ni and Pb concentrations are accumulated in the top soil

and decreased with the depth inside the soil (except Cd).

2. This study indicates that (64.7%), (100%), (6%) and (20.6%)

of all soil samples contain zinc, nickel, lead and Cadmium

concentration (respectively) greater than the standard limit of

their concentrations in soil.

3. This study, also indicates that (100%), (100%), (97%) and

(82.35%) of all soil samples contain zinc, nickel, lead and

Cadmium concentration (respectively) greater than their

concentrations in soil sample from the rural area.

4. The highest concentrations value of zinc and nickel were in

the center of the refinery; and the highest lead concentration

were near the power former unit; and the cadmium highest

value was near the flare.

5. The pH values are neutral in general, and hence the mobility

of the heavy metals will be limited at these values of pH.

6. The heavy metals make the clay particles coarser because of

the bonding between them.

7. The seriousness of food crops, including seasonal vegetables

because of lead pollution.


98

5.2 Recommendations

Results of the study are useful to the Ministry of Environment, Al-

Daura refinery and researchers and recommended that:

1. Carrying out further researches on the pollutant identification and

quantification and bio remediation of polluted lands, such as the use

of bacterial transformations of polluted.

2. Soil amendment programs by emphasizing on the increased use of

plant nutrients, like the organic manure, should be established in Al-

Daura, especially in areas around the refinery. The use of manure is

known for correction of soil acidity and firmly binding of metals

within the soil colloids, barring them from being readily available to

the plants and water pollution through a leaching process. Lime

application is useful in raising the soil pH which reduces the metal

availability and hence toxicity.

3. Immediate medical intervention measures should be thought in order

to determine the extent and effects of human diseases associated with

refining pollution in all over the areas surrounding the refining

activities.

4. Maintenance of all the refinery units that cause emissions.

5. Add treatment materials to refining operations for the purpose of

reducing the emissions of heavy metals from the refinery.

6. Compulsion the maintenance on the automobile to reduce the

emissions from it.

5.3 Recommendations for Future Works

1. Further investigations are required on the impact assessment of

heavy metals in Tigers River and the groundwater of the surrounding

region.


99

2. Carrying out a study on air pollution of the same study area.

3. Studying the concentration of heavy metals in the same study area at

different times of the year to determine seasonal variation.

4. Using the Geographic Information System (ArcGIS) software in the

environmental analysis and modeling, because the GIS has become a

very powerful tool for environmental science and engineering.

chapter one: introductionuotechnology.edu.iq/dep-building/aldrassat_alaleaa/alatareah... · chapter...

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