Groundwater most common contaminants found

A possible source for much of the groundwater contamination is landfill leachate containing trichloroethylene. Trichloroethylene was the most commonly found chemical at NPL sites in New York State (Mumtaz et al. 1994). The compound was detected in leachate samples from Minnesota municipal solid waste landfills at levels ranging from 0.7 to 125 pg/L (0.7-125 ppb) and in groundwater near landfills at levels ranging from 0.2 to 144 pg/L (0.2-144 ppb) (Sabel and Clark 1984). Trichloroethylene was also detected in landfill leachate from a landfill in New Jersey at concentrations of up to 7,700 pg/L (7,700 ppb) (Kosson et al. 

Many groundwaters are contaminated with the cleaning solvents trichloroethylene (TCE) and perchloroethylene (PCE). They are two of the most common organochlorine compounds found in Superfund sites. Radiation-induced decomposition of TCE in aqueous solutions has been the subject of several recent studies [15-20]. In most of the referenced studies, the complete destruction of TCE was observed. Dechlorination by a combination of oxidative and reductive radiolysis was stoichiometric. Gehringer et al. [15] and Proksch et al. [18] have characterized the kinetics and mechanism of OH radical attack on TCE and PCE in y-ray-irradiated aqueous solution. Trichloroethylene was readily decomposed in exponential fashion, with a reported G value of 0.54 pmol J-1. A 10 ppm (76 pM) solution was decontaminated with an absorbed dose of less than 600 Gy. For each OH captured, one C02 molecule, one formic acid molecule and three Cl- ions were generated. These products were created by a series of reactions initiated by OH addition to the unsaturated TCE carbon, which is shown in Eq. (45) ... 

Herbicides are sometimes also used in urban areas for control of weeds on railway lines and roadside verges, and around areas of hard standing. Some of the herbicides used are sufficiently persistent to be able to be washed into drains or soil, and possibly percolate into groundwater. One of the most common of these herbicides is atrazine, which has been found in the groundwater of many countries. Awareness of the potential for contaminating groundwater and careful selection of herbicides, where they are required, has significantly decreased contamination in many of the areas where it was common. 

The monoaromatic compounds benzene, toluene, ethylbenzene and xylene, commonly found in crude oil, are often jointly called BTEX compounds. The most harmful of these compounds is benzene, which is a known carcinogen. BTEX compounds occur naturally near natural gas and petroleum deposits and are detected in the fumes of forest fires. Most of the highly volatile BTEX compounds released by human activity originate from fuel use and end up as pollutants in the air. Inhaling BTEX-polluted air is also the greatest hazard to humans by these compounds. BTEX compounds are water-soluble, and therefore, improper handling can also cause groundwater contamination. 

Surface water was determined to be more vulnerable than groundwater for most contaminants. SOCs were more common in surface waters, and most of the contaminants that exceeded the MCLs were in surface waters. For VOCs, however, no signihcant difference was found in the number of contaminants exceeding MCLs in ground or surface waters. lOCs were found to be equally common in both ground and surface waters. Many SOCs (pesticides, in particular) were seasonally present. 

Universal across-the-board cleanup criteria are not commonly used as end points for soil and groundwater cleanup, because of the wide range of risks found at these sites. However, two classes of contaminants have been subject to universal action levels for cleanup petroleum and polychlorinated biphenyls (PCBs). Most petroleum hydrocarbon action levels are regulated by state and local agencies the parameters used and their corresponding action levels vary widely from state to state. The specific petroleum parameters that are regulated include total petroleum hydrocarbon— gasoline fraction (TPH-G) total petroleum hydrocarbon—diesel component (TPH-D) ... 

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