Edward Lu

Liwei Yang

Ground Water

ABE 325 Soil & Water Conservation Engineering• Water quality lab site:http://pasture.ecn.purdue.edu/~eql/WaterQuality

• Lecture site:http://pasture.ecn.purdue.edu/~abe325/syllabus.html

For Oct. 24 groundwater.pdf

Ground water is the water below the land surface that completely fills (saturates) the pore spaces in the subsurface materials.

Ground water is a vital part of rural life.

Nearly 95 percent of rural families in the United States rely on ground water as their source of drinking water.

Many agricultural uses for ground water such as irrigation and livestock watering.

The quality of life in the rural community depends on an abundant and dependable supply of potable ground water (i.e. suitable for drinking).

About 70 percent of the Earth surface is covered by water. But more than 97 out of every 100 drops of water on earth are saline and, therefore, not potable

The largest storage of fresh water on earth are the ice caps. But they are not easily accessible sources of drinking water.

Ground water is the premier source of readily available fresh water for human consumption.

Compared to other fresh water sources, ground water is 25 times more abundant than all the lakes, reservoirs and rivers of the world combined!

Data from World Water Balance and Water Resources of the Earth, Copyright, UNESCO, 1978

The ground water system is poorly understood by most people.

People need to have:

• An appreciation of the benefits of ground water

• an understanding of the basics of ground water movement

• an understanding of the cause-effect link between our actions on the land surface and ground water quality

Water Quality

• Biological water quality– Microorganisms, pathogen contamination – Macroorganisms, fish and plant

• Chemical water quality– Farm chemicals, fertilizer and pesticide– Heavy metal, mercury– Discharge from sewage, septic tanks, and waste

water treatment plant

"It isn't pollution that's harming the environment. It's the impurities in our air and water that are doing it."

-- Vice President J. Danforth ("Dan") Quayle's, 1988http://www.realchange.org/quayle.htm

CHEMICALS IN THE FARM WATER CYCLEThe most effective approach to protect ground water quality: Appropriate management at the land surface

Land surface or uppermost few tens of feet of the subsurface arethe focus:

• The entry ways for most ground water contaminants.

• The area that land owners can control directly.

Examples of Best Management Practices (BMP) on Farms:

• inspecting fuel storage tanks

• soil testing for fertilizer application rates

• sealing abandoned wells

Chemical Application, Contaminant & Pollutant DefinitionsChemical application

spreading of a chemical on the land surface or incorporating it into the plow layer of a field.

Examples of chemical applications

• spraying a weed killer on your lawn,

• spraying a road surface to reduce dust

• incorporating anhydrous ammonia as a nitrogen fertilizer.

A contaminant or pollutant isany chemical within the farm-water cycle that has moved away from

the area of its intended use and is present in water in concentrations defined as unacceptable for the water’s intended use.

Pollutionany reduction of the quality of water bevond levels established as

safe for the intended use.

Sources Of Concentrated Chemical Pollutants In

Ground Water

• Business and industrial activities:

dry cleaners, paper processors, metal coating companies, and gas stations.

• Farm operations

farm chemical spills during mixing and loading, excessive fertilizer and pesticide applications, inappropriate manure storage techniques, and improper disposal of farm chemical residuals and containers.

• Household activities:

improper use or disposal of chemicals include: paint thinners, used motor oil, drain openers and discharge of water softeners.

Chemical Transport

Focus: movement with water away from the unsaturated zone

Process overview:•Rain or irrigation

•Dissolve with the water and begin to travel

•Infiltration to the unsaturated zone

•Surface runoff will begin

•Travel toward surface waters (e.g. streams, ponds, or lakes).

•Downward movement of chemicals toward the saturated zone

• Plant uptake

• Broken down by chemical or microbial action

• Volatilization

• Adsorbed (i.e. chemically bonded) by soil particles (clays and organic matter)

Flow with groundwater

Mixing

Spread

Removal impossible

Remediation only solution (point-of-entry/point-of-use)

http://www.geo.utexas.edu/courses/302P/Fall%202001%20stuf/Lectures%20by%20topic/FreshwaterImpact/Images/mac9.8.jpg

ImpossibleRelatively easy but costlyRemediation

Difficult even with safe practiceSafe practicePrevention

Effectively intentionalAccidentalCauseChronicAcuteHealth riskLowHighConcentration

Over large area, unidentifiableSingle, indentifiableSource

Non-point source pollution

Point source pollution

The region of point source pollutant concentration within an aquifer zone is called a plume. The plume describes a three-dimensional zone of contamination, at some specified level of concentration(s), which moves with the ground water.

Pollutants enter aquifer

1) a continuous release over a long period of time

2) as a concentrated slug of pollutant that is released, more or less all at once

Point source contaminant plume is easiear to cleanup (than NPS), but the costs are great. Prevention is the most economical approach.

A pumped well which taps a contaminated region of an aquifer has the potential to pull either high-concentration pollutants (typical of point sources) or lower-concentration contaminants (typical of nonpoint sources) directly into the well

Contaminated water in the aquifer zone travels by the same mechanisms for confined and unconfined aquifers.

Methods for groundwater quality protection

Identify potential sources of contamination at the farm site and in the surrounding area and learn about water supply source location

Point sources:

fuel storage tanks, pesticide and fertilizer storage facilities and animal waste storage structures.

Non-point sources:

Septic systems and the chemicals applied to farm fields or lawns.

Questionnaire such as the Water Quality Serf-Help Checklist published by the American Farm Bureau Federation can help.

The key is to choose the correct TIMING and AMOUNT of application

* soil testing and establishing realistic yield goals to set fertilizer requtrements

* taking credits for nutrients from legume crops and animal manure

* timing/split applications to meet crop needs

• Soil conditions:

-- Texture: sandy or clay-rich, ease of drainage

-- Amount of organic matter

-- Chemical adsorption capability (persistence of chemical applied)

• Site conditions:

-- Depth to water table

-- Abandoned wells nearby

-- Fractured or soluble bedrock in the area

* Management

-- Tillage method

-- Application techniques

-- Disposal of containers and remainder

-- Integrated Pest Management (IPM) alternatives

Nutrient and pesticide management (cont’d)

You can always consult the local office of Soil Conservation Service and your county Extension Service to help you plan a nutrient and pesticide management system.

Limiting the use of the land immediately around the well and ensuring proper maintenance and security of the well is called well head protection

Risky activities: mixing and loading of chemicals or rinsing of equipment in the area immediately surrounding a well, improper construction or direct injection into the well.

A spill in the well head zone could quickly contaminate well water and result in the loss of the well and permanent damage to the aquifer.

The need for extreme care around wells can not be overemphasized.

Management for the well-head area includes many simple precautions:* ensure the well head is properly sealed to avoid direct injection

* inspect the well-head casing for cracks that might allow contaminants to enter

* mix and load chemicals at least 100 feet from the well

* install a check valve on filling lines to prevent back-siphoning while filling a spray tank

* ensure that all abandoned wells are properly sealed

Consult your local health department for information on well-water testing and proper well construction and abandonment standards and methods.

Units:

ppb: part per billion, i.e. µg/L

ppm: part per million, I.e. mg/L

http://www.epa.gov/safewater/mcl.html#mcls

Important: get a “clean” sample, minimize secondary contamination

E. Coli is non pathogenic

More abundant than other pathogenic microorganisms

Use the concentration of coliform and E. coli as indication of potential presence of other pathogenic microorganisms

Definition:

Coliform: relating to, resembling, or being E. coli

CFU: coliform forming unit

Chemical water quality parameters

• pH

• Electrical conductivity

• nitrate and phosphorus levels (concentrations)

pH

- expression of [H+] of water

Autoionization:

H2O + H2O <--> H3O+(aq) + OH-(aq)

- life (mostly) depends on waters that are neutral in acidity (pH 7-8)

- convert [H+] from 10-1M ~ 10-14M to 1~14 via: - log10[H+]

pH will have negative value if [H+] > 1.0 M,such as for strong acid, sulfuric acid

1 2 3 4 5 6 7 8 9 10 11 12 13 14

Neutral

Acidic Basic

Water Electrical Conductivity – Total Dissolved Solids Measurement

Total dissolved solids (TDS) refers to total concentration of inorganic solids. (mg/L)

TDS refers to ions like calcium, magnesium, sodium bicarbonate, nitrogen, phosphorous, iron and sulfur

The presence of these chemical constituents gives water the ability to conduct electricity, hence, electrical conductivity (EC) of water is an indirect measure of its dissolved constituents

EC is expressed in terms of the specific electrical conductivity, which is defined as the reciprocal of electrical resistance in ohm (Ω), in relation to a water cube of edge length 1 cm at 20 0C

The specific EC unit is given in siemens per cm (S.cm-1), where S = Ω-1

It has been found that 0.67 mg/L TDS contribute to 1 µS.cm-1

EC gives a determination of TDS, which is an acceptable indicator for water quality.

Some numbers to remember:

• A distilled water should typically have an EC of less than 0.3 µS.cm-1.

• For ground water, an EC of 500 µS.cm-1 suggests a pollution problem, while values as high as 2000 µS.cm-1 may be acceptable for irrigation water.

• Drinking water has a secondary MCL of 500 mg/L TDS.

• Apply electrical charge

• record conductivity

• relate to TDS concentration

• Conductivity / TDS meter.

• Water samples

• Deionized water

ANION DETERMINATION OF WATER BY ION CHROMATOGRAPHY

Speed1 = d1/time

Speed2 = d2/time

http://www.childrenswholesale.com/images/girl-dress-sizes-ruler.jpg

ION CHROMATOGRAPHY Application

www.pnl.gov/aoam/research/ lmw2.htm

IC Chromatogram of LMM acids in HanfordTank Waste (Tank ID AN-107) using AS-11 Column

• Take a whirlpak water sample bag

• Bring sample to school next Tuesday, put in frig

• On sample bag, record:

• sampling location

• date and time

• Your name and group

Point Source Pollution:A single, identifiable source that discharges (empties) pollutants into the environment. Point source pollution is characterized by high concentrations over a small area or at a point. It causes acute problems because their high concentrations. Point source pollution is generally accidental. Through increased awareness and safer practices, the number of point source pollution problems could be reduced.

Non-point Source Pollution: A more difficult source of pollution to pinpoint because this pollution type enters the environment from a widespread land area. It is characterized by low concentrations over a large area. This is considered a chronic (as opposed to acute) problem because of the characteristic low concentration of the chemical that persists over a long time period. It is effectively intentional and can occur even with safe application practice is in place.