Site, ground-water leaching

Silicate glasses, physical properties, 150-54 Single-phase reactions, ground-water 335-44 Site, ground-water leaching,... 

The general purpose of ultimate disposal of hazardous wastes is to prevent the contamination of susceptible environments. Surface water runoff, ground water leaching, atmospheric volatilization, and biological accumulation are processes that should be avoided during the active life of the hazardous waste. As a rule, the more persistent a hazardous waste is (i.e., the greater its resistance to breakdown), the greater the need to isolate it from the environment. If the substance cannot be neutralized by chemical treatment or incineration and still maintains its hazardous qualities, the only alternative is usually to immobilize and bury it in a secure chemical burial site. 

Waste, repository site-selection criterion, ground-water leaching. 335-36... 

There are presently over 26,000 uncontrolled waste sites in the United States as reported by the Environmental Protection Agency (EPA) (i). Of these sites, 951 are on the National Priority List (NPL) which makes these sites eligible for funds from the Superfimd. One common characteristic of the NPL sites is that the site ground water is contaminated by the leaching of pollutants from contaminated soil. Therefore, the task of cleaning up such a site involves the detoxification of both solid (soil) and liquid (water) matrices contaminated with a common pollutant. 

There may be other pesticide contaminants and ground water contamination sites yet to be discovered. Therefore, the 12 different pesticides found In a total of 18 different states, as listed In Table III, represents the minimum number of pesticides and their distribution. There have been several reports of plcloram In well water, most of them anecdotal. However, It cannot be substantiated that the contamination has been due to normal pesticide use and leaching throu the soil or due to spillage. 

Phenols are important industrial chemicals, for example, in the production of various plastics and resins, and may leach into surface and ground waters either during production or from the discharged products at landfill sites. Because of their ecological importance and their widespread use, methods for phenols and related compounds (e.g., anilines) were developed already at an early stage. Many of these methods rely on GC (or GC/MS), which normally requires derivatization prior to GC analysis. Standard methods for the derivatization of phenols are silylation, methylation, or acetylation.5 The last mentioned has the advantage that it can be carried out in the aqueous sample directly. The deriva-tized phenols can thus be extracted more easily and with a higher yield from the aqueous sample by... 

List three different household wastes that are commonly discarded and have the potential to contaminate ground water if rain leaches through your local landfill site. What chemi-cal(s) does each contain For each waste, identify an alternative to dumping it in a landfill site. 

Xenoestrogens, regardless of their molecular diversity, have the ability to leach into ground water and contaminate the water supply if not removed by various methods of water purification. Before 1973 when it was banned, DDT entered the air, water, and soil during its production and use as an insecticide. DDT is present at many waste sites, and releases from these sites may continue to contaminate the environment. Most of the DDT in the environment is a result of past use, but it still enters the environment because of its current use in other areas of the world where it is not banned. DDE is only found in the environment as a result of contamination or breakdown of DDT. 

Surface strip mining of coal destroys the native vegetation at the mine site. The topsoil is sufficiently disturbed that it is difficult to rehabilitate the site and re-start the native growth pattern. Oxidation of waste coal and mine residues produces sulfuric acid and releases toxic materials such as arsenic, selenium and beryllium. These leach into the ground water and drain into streams and lakes. At a minimum, these materials strongly alter the types of plant and animal life able to survive in their presence. At the worst, they kill all life near the mine. 

New information on the effects of chemicals has received widespread media attention. Bioconcentration of chemicals such as PCB and DDP in fish, new findings of carcinogenicity, and the occurrence of reproductive health effects, to name only a few, are topics which have been publicized in media of every type. Incidents ranging from transportation spills to the leaching of chemicals into ground water from waste disposal sites have... 

For a small-scale retrospective study, participants enter and study a field in which a pesticide has been used over a period of time. The purposes of small-scale retrospective studies are to determine whether the pesticide(s) in question has leached to ground water in certain fields, and to characterize the leaching pattern in the soil profile at a given point in time. This section contains discussions on site selection, site characterization, the number and location of observation wells, well construction and sampling, and soil sampling. 

The PRZM model was used to evaluate the potential of aldicarb to leach through soil and contaminate ground water in three use sites tobacco grown on a sandy loam soil in North Carolina and potatoes grown on a sandy loam and a loamy sand in Wisconsin. 

Subsurface soil samples are important, however, if soil disturbance is likely or if leaching of chemicals to ground water is of concern, or if the site has current or potential agricultural uses. For subsurface testing, depths of one to two feet can be used. Another item of concern is the determination of the types of samples to be collected. Basically, two types of samples may be collected at a site grab and composite. Grab samples represent a single part of a medium collected at a specific location and time. Composite samples (sometimes referred to as continuous samples for air) combine subsamples from different locations and/or times. Composite samples may misrepresent or dilute concentrations at specific points and, therefore, should be avoided as the only inputs to a risk assessment. 

In New Jersey, COPR exist at over 130 sites in Hudson Country, many of which are in urban residential areas. The waste is the result of 70 years of chromate and bichromate chemical manufacturing, and potentially can be leached into ground water. At least 15% of the sites have total chromium concentrations greater than... 

EXPOSURE ROUTES ambient air drinking water ground water air around factories where it is manufactured use of products containing the chemicals evaporation and leaching from waste disposal sites... 

Of particular concern is the contamination of ground-water (underground aquifers) by wastes leaching through soils from surface dump sites (Fig. 9). The removal of pollutants from such aquifers is difficult and expensive ... 

Once the Ca, Mg, K and Na cations have been displaced from the soil exchange sites into the soil water/ they are available to be leached down, through and out of the soil profile into ground-water etc. This movement requires mobile/ i.e. available/ anions to act as vehicles for cation transport. Much of the potential impact of acidic atmospheric deposition stems from the fact that it increases the supply of mobile anions/ i.e. dissociated anions such as S04 / to the soil. It has been shown that atmospheric H2SO4 inputs in some podsolic soils cause perhaps a threefold increase in the natural rate of cation leaching. 

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