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Treatment of polluted soil with lead by Bio-phytoremediation

technique

Treatment of polluted soil with lead by Bio-phytoremediation

technique

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• Dr. Mohammed Elanwar Osman Professor of Plant Physiology, Botany Department,

Faculty of Science, Tanta University

• Dr. Mohammed Ismail Elshahawy Professor of Soil, Water and Environment, Research

Department, Agricultural Research Sakha Station

• Dr. Soad El-Feky A. Professor of Plant Physiology, Botany

Department, Faculty of Science, Tanta University

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• studying the effect of different pb levels on growth and some stress markers and metabolic activities in flax tissues.

• Studying the ability of flax plant to accumulate and tolerate high concentrations of pb which are often associated in polluted areas.

• Studying the ameliorative effect of some biofeltilizers on growth, metabolic activities and yield of flax grown under high concentrations of pb.

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• The objectives are to discuss the potential of phytoremediation technique on treating heavy metal-contaminated side, to provide a brief view about heavy metals uptake mechanisms by plant, to give some description about the performance of several types of plants to uptake heavy metals and to describe the fate of absorbed pb metal in plant tissue.

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• Since the dawn of the Industrial revolution, mankind has been introducing numerous hazardous compounds into the environment at an exponential rate.

• These hazardous pollutants consist of a variety of organic compounds and heavy metals, which pose serious risks to human health.

• Heavy metals are primarily a concern because they cannot be destroyed by degradation. Frequently, the remediation of contaminated soils, groundwater, and surface water requires the removal of toxic metals from contaminated areas .

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Heavy metals

• In an ecological research, any metal or metalloid that causes environmental problem which cannot be biologically degraded should be considered as a heavy metal. several HMs has reached toxic levels due to consequence of anthropogenic activities. (Padmavathiamma and Loretta, 2007)

• Fifty three elements fall into the category of heavy metal till date and

defined as the group of elements whose densities are higher than 5 g cm3 and recognized as ubiquitous environmental contaminants in industrialized societies . (Padmavathiamma and Loretta, 2007)

• The most common heavy metal contaminants are: Cadmium (Cd), Chromium (Cr), Copper (Cu) Mercury (Hg), Lead (Pb), Nickel (Ni) and Zinc (Zn). (Lasat et al., 2001)

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Lead

• lead represent one of the most frequently distributed heavy metal pollutants on agriculturally exploited soils. ( Miroslav, et al., 2005)

• Among heavy metals, lead is considered one of the dangerous environmental pollutants in soil, sediments, air and water and considered one of the most difficult pollutants to control. Over recent decades, the annual worldwide release of lead 783,000 t . (Abdul Ghani, 2010)

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Sources of Lead

• Frequent use in many industrial processes is the main reason for lead contamination of the environment such as mining, smelting, manufacture of pesticides and fertilizers, dumping of municipal sewage and the burning of fossil fuels that contain a lead additive.

• Many commercial products and materials also contain lead including

paints, ceramic glazes, television glass, batteries, medical and electrical equipment .

• The uses of lead for roofing and the production of ammunition has increased from previous years .

• Total annual emission of lead by motor vehicles & industrial plants alone throughout the world amounts more than half a million ton.

(Sharma and Dubey, 2005).

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Health Effects

• Lead is not only a toxic element but also can be accumulated in plant organs and agricultural products. (El-Beltagy, 1998)

• Also, introduction of this metal to man and animals through drinking water or food will help in occurring many diseases to them such as renal failure, brain and liver damage. (Abdul Ghani, 2010)

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The effect of pb on plants has been studied by several workers:-

• Soils contaminated with Pb cause sharp decreases in crop productivity thereby posing a serious problem for agriculture. (Johnson and Eaton,1980)

• At a high Pb content in soil, photosynthesis can also be reduced due to both a lower carboxylase activity and the effects on metabolites of the carbon reduction cycle. (Carlson et al., 1995)

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• Enhanced level of lead in soil caused significant reduction in plant height, root-shoot ratio, dry weight, nodule per plant, chlorophyll content in Vigna radiata. (Bekiaroglou and Karatagli, 2002)

• Pb toxicity leads to decreases germination percent, length and dry mass of root and shoots, disturbed mineral nutrition and reduction in cell division. (Paivoke, 2002)

• Exposure of maize varieties to excess Pb resulted in a significant root growth inhibition though shoot growth remained less affected. (Abdul Ghani, 2010)

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• Several methods are already being used to clean up the environment from contaminants such as heavy metals, but most of them are costly and far away from their optimum performance such as chemical and thermal methods. Both technically difficult and expensive that all of these methods can also degrade the valuable component of soils .

• In recent years, scientists and engineers have started to generate cost effective technologies which includes use of microorganisms/ biomass or live plants for cleaning of polluted areas called phytoremidiation.

(Qui et al., 2006)

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phytoremediation

• Phytoremediation is the use of plants to clean up a contamination from soils, sediments, and water. Plants with exceptional metal-accumulating capacity are known as hyperaccumulator plants. (Tangahu, 2011)

The hyperaccumulators

• Hyperaccumulators are model plants for phytoremediation as they are tolerant to heavy metals. Metals hyperaccumulation and tolerance are genetically inherited traits. Plants possess a range of potential cellular mechanisms that may be involved in the detoxification of heavy metals and thus tolerance to metal stress. (Sarma , 2011)

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Types of phytoremediation technology

Each having a different mechanism of action for remediating metal-polluted soil, sediment or water:

1) Phytoextraction: Plants absorb metals from soil through the root system and translocate them to harvestable shoots where they accumulate. Pollutants accumulated in stems and leaves are harvested with accumulating plants and removed from the site.

2) Phytovolatilization: In this process, the soluble contaminants are taken up with water by the roots, transported to the leaves, and volatized into the atmosphere through the stomata.

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3) Phytostabilization: In this process, the plant roots and microbial interactions can immobilized organic and some inorganic contaminants by binding them to soil particles and as a result reduce migration of contaminants to grown water.

4) Phytofiltration: Phytofiltration is the use of plants roots (rhizofiltration) or seedlings (blastofiltration) to absorb or adsorb pollutants, mainly metals, from water and aqueous waste Streams.

5) Phytodegradation: contaminants are taken up from soil/water, metabolized in plant tissues and broken up to less toxic or non-toxic compounds within the plant by several metabolic processes via the action of compounds produced by the plant.

(Sarma , 2011 )

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The mechanisms of heavy metals uptake by plant through phytoremediation technology. (Tangahu, 2011)

18Advantages of phytoremediation technology. (Tangahu, 2011)

19The limitation of phytoremediation technology. (Tangahu, 2011)

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The presented project is focused on utilization of some industrial crops as models for phytoremediation problems

• Fiber crops are suitable for phytoremediation studies because they easily accumulate heavy metals, and, in addition, they need not necessarily to be processed in food chain, but they can be used for production of textile, paper, paints or as a substitute of synthetic materials in car and aviation industry as well as for non-woven textile production. There is a possibility to use these plants as a fuel for energy production. (Bjelkova, 1999)

• Fiber crops represent a promising group of plant species in phytoremediation of heavy metals due to the possibility of the use of contaminated biomass for a plethora of industrial products. (Bjelkova, 2003)

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Flax: (also known as common flax or linseed)

Botanicalname: Linumu sitatissimu Family: Linaceae (Linseed family)

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• Flax is suitable for growing in industrially polluted regions. They remove considerable quantities of heavy metals from the soil with their root system and can be used as potential crops for cleaning the soil from heavy metals. (Angelova, et al., 2004)

• Flax as an industrial crop utilized mainly for technical purposes is a good candidate for heavy metal phytoextraction from polluted soils. (Griga, et al., 2009)

• Flax which is a culture plant, is grown in order to benefit from fiber and fat . Flax production is done approximately 5-6 million hectares in the world .70% of this production is to produce oil and the rest is to produce fiber. (Tulukcu and Akay, 2010)

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Flax as hyperaccumulator are represented by several reserches:

• In the uptake and accumulation of Cd and Pb. both fiber flax and linseed well tolerated elevated heavy metal soil concentrations without dramatic effect on the plant growth and development. ( Miroslav, et al., 2005)

• Significant differences in Cd accumulation and tolerance were found among commercial flax cultivars as phytoremediation potential. (Hradilova, et al., 2010)

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• Even high soil Cd concentrations (1000 mg Cd kg−1 soil) had not dramatic negative effect on plant growth and development in flax. (Bjelkova, et al., 2011)

• Flax and linseed varieties variously accumulated particular metallic elements, the highest concentrations were recorded for Zn, followed by the Pb and Cd.

( Bjelkova, et al., 2011)

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Biofertilizers

• Biofertilizers are compounds that enrich the nutrient quality of soil by the use of microorganisms which have a symbiotic relationship with the plants. The main sources of biofertilizers are bacteria, fungi, and cynobacteria (blue-green algae).

• Biofertilizers are cost effective and renewable source of plant nutrients to supplement the chemical fertilizers for sustainable agriculture.

(Mishra and Dadhich, 2010)

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Compost

• Composting is a biological process in which organic biodegradable wastes are converted into hygienic, hums rich product (compost) for use as a soil conditioner and an organic fertilizer. (Popkin, 1995)

• The addition of municipal solid waste compost to agricultural soils has beneficial effects on crop development and yields by improving soil physical and biological properties. (Zheljazkov and Warman, 2004)