Groundwater Pollution in Bangladesh Essays

Groundwater Pollution in Bangladesh Essays Groundwater Pollution in Bangladesh Paper Groundwater Pollution in Bangladesh Paper 900 parcels of land each year. Contamination can occur from improper land-disposal techniques. Storage and Handling of Materials and Wastes Groundwater contamination as the result of storage and handling of materials includes leaks from both above-ground and underground storage tanks, as well as unintentional spills or poor housekeeping practices in the handling and transferring of materials on industrial and commercial sites. Aging underground Storage Tanks Possibly as many as 7 million steel tanks are used to store petroleum products, acids, chemicals, industrial solvents and other types of waste underground. The potential of these tanks to leak increases with age. About 20 percent of existing steel tanks are more than 16 years old, and estimates f the total number that presently leak petroleum products range from 25 to 30 percent. Underground storage tanks appear to be a leading source of benzene, toluene and Selene contami nants, all of which are organic compounds in diesel and gasoline fuels. Transporting and Stockpiling Many materials and wastes are transported and then temporarily stored in stockpiles before being used or shipped elsewhere. Precipitation can lea potential contaminants from such stockpile; storage containers can eroded and leak; and accidental spills mean occur as many as 10,000 to 16,000 per year, according to EPA estimates. Mining Practices Mining of coal, uranium and other substances and the related mine spoil can lead to groundwater contamination in several ways: * Shafts and tunnels can intersect aquifers. * Exposing coal to oxygen can form sulfuric acid, which can degrade water * Contaminants from tailings can leach into groundwater. Oil-Well quality. Bribes Since the asses, hundreds of thousands of exploratory and production wells have been drilled for oil and gas in the United States. During production, Oil wells produce bribes that are separated from the oil and stored in surface impoundments. EPA estimates that 1 25, 100 brine-disposal impoundments exist that might affect local groundwater supplies. Agricultural Activities Agriculture is one of the most widespread human activities that affects the quality of groundwater. In 1987, about 330 million acres were used for growing crops in the united States, of which 45 million acres were irrigated. Fertilizers During the 1 9605 and asses, nitrogen, phosphorus and potassium fertilizer use steadily increased to a peak of 23 million tons in 1981. By 1987, however, fertilizer use had declined to 19. Million tons, reflecting the large number of acres withdrawn from production as part of the Conservation Reserve Program and other government programs. If nitrogen supply exceeds nitrogen uptake by crops, excess nitrogen mean be leached to groundwater. In such areas, local nitrate-nitrogen concentrations may exceed the federa l drinking water standard of 10 MGM/L Pesticides Pesticides have been used since the asses to combat a variety of agricultural pests. Between 1 964 and 1 982, the amount of active ingredients applied to croplands increased 1 70 percent. Herbicide usage peaked in 1982, and since then has declined from about 500 million pounds of active ingredients per year to about 430 million pounds in 1987. In addition to crop applications, infiltration of spilled pesticides can cause contamination in locations where pesticides are stored, and where sprayers and other equipment used to apply pesticides are loaded and washed. Pesticides most frequently detected in groundwater are the fumigants ethylene debrief (DB) and 1 disproportional; the insecticides Aldrich, carbons and chlordane; and the herbicides alcohol and trainee. Feedlots Feedlots confine livestock and poultry and create problems of animal-waste disposal. Feedlot wastes often are collected in impoundments from which they might infiltrate to groundwater and raise nitrate concentrations. Runoff room farmyards may also directly enter an aquifer along the outside of a poorly sealed well easing. Irrigation Percolation of irrigation water into soils dissolves soil salts and transports them downward. Photoengravings of applied water from the root zone concentrates salts in the soil and increases the salt load to the groundwater. Checkmating, the practice of mixing and distributing pesticides and fertilizers with irrigation water, may cause contamination if more chemicals are applied than crops can use. It may also cause local contamination if chemicals back- siphon from the holding tank directly into the aquifer through an irrigation ell. Saline Water Intrusion The encroachment of saline water into the freshwater part of an aquifer is an ever-present threat when water supplies are developed from the highly productive coastal plain aquifers of the United States, or from aquifers underlain by saline water in the interior of the country. Local incidents Of saline water intrusion have occurred on all coasts of the United States. How Extensive is Groundwater Contamination Assessment of the extent of groundwater contamination is difficult, due to such factors as limited and inconsistent access to the water (usually pendent on wells and springs); the potential for bias in existing data (if originally collected to explore a particular water quality problem); incomplete information about the well (did the well draw from more than one aquifer? ; and inconsistent methods of sampling and analysis. It is also important to keep in mind that the trend of increasing reports of detections of contaminants in groundwater is largely due to the intensive search for contaminants now under way by many state agencies, as well as continued improvements in the sensitivity of analytical methods used to measure the concentration Of contaminants. The volume Of groundwater within 2500 feet of the surface has been estimated at 100 quadrillion gallons, or about 16 times the volume of the Great Lakes. Of this amount, at least half is too saline from natural causes to use for drinking water, although some of it may be suitable for other uses. The total amount of the remaining groundwater that is contaminated is unknown, although EPA estimates the amount contaminated by point sources to be 2-3 percent. Recent U. S. Geological Sunny studies have made the following assessments: * The United States has large amounts of potable water available for use. Locally, however, high concentrations of a variety of toxic metals, organic chemicals and petroleum products form plumes around such point sources as leaking underground storage tanks, waste disposal sites and chemical or waste handling areas. These types of problems generally occur in urban or industrialized areas, although they are found occasionally in rural areas. Large regions have been identified in which contaminants, derived from Nippon sources and often at minimum detectable levels, are present in many shallow wells throughout a given area. In a small percentage of wells, such contaminants as titrate may exceed drinking water standards or health advisories. Generally, s uch Nippon source contamination is associated with densely populated urban areas, agricultural land uses and concentrations of septic systems. Furthermore, such contamination commonly affects only the shallowest aquifers. * 20 percent of 124,000 wells sampled over the past 25 years contained a maximum nitrate-nitrogen concentration greater than 3 MGM/L, suggesting the effects of human activities. 6 percent of the samples exceeded the federal drinking water standard for nitrate-nitrogen of 10 MGM/L. Although 44 state summaries in the U. S. Geological Surreys 1 986 National Water Summary on groundwater quality mention detection of pesticides in groundwater, data are insufficient to draw conclusions about the extent of contamination. The state summaries do, however, express widespread concern that the frequency of detections and the concentrations of pesticides will increase over time. The U. S. EPA has compiled reports on the occurrence of 46 pesticides in groundwater. In 26 states, o ne or more pesticides have been tweeted in groundwater that mean be attributed to normal agricultural use. The most commonly detected pesticides are trainee and Aldrich. EPA currently is conducting its National Pesticide Survey to provide a nationwide estimate of the occurrence of pesticides in drinking water wells. The survey includes the collection of water samples from a statistically representative sample of community water system wells (600) and private wells (750). Interim results show that 6 of 180 community well samples collected thus far and 9 of 115 private well samples had detectable pesticide residues. Of the 15 wells that had detectable levels of pesticides,3 had concentrations that exceeded lifetime health advisory levels established by EPA. Of 295 wells ample thus far, samples from 8 wells had nitrate-nitrogen concentrations that exceeded the 10 MGM/L drinking water standard. All 8 samples were from private wells. Statistically reliable estimates of the percentage of wells contaminated will be available when the survey results are released in late 1990. Summary: How Contaminated is Groundwater? Although little systematic information exists on the extent and severity of groundwater contamination, available evidence suggests that * The shallowest aquifers generally are at greatest risk of contamination, especially those where the overlying unsaturated zone is thin and permeable. Contamination of shallow aquifers by nitrates and synthetic organic chemicals is widespread in many areas; * Shallow groundwater contamination can be related to land use. * As yet, deeper as fifers, which commonly are used for public drinking water supplies, are relatively free from contamination. Additional reports of groundwater contamination may be expected in the coming years, as federal, state and local agencies expand their groundwater quality monitoring programs using sophisticated analytical methods that can measure very small concentrations of contaminants. Groundwater moves very slowly, and it may be years after remedial actions re taken before improvements in water quality are obsessed. For this reason, the enhancement of the quality of the nation s groundwater requires a long- term commitment. More definitive assessments of groundwater quality will have to await the expansion of data-collection programs, the use of standard sampling and analytical procedures, research on the health risks associated with long-term exposure to very small concentrations of contaminants, and improvements in the computer models used to predict contaminant behavior.