Research On Characteristics And Mechanism Of Shallow Groundwater Organic Contamination In Eastern China

The study area is located in Yangtze River Delta. Many pollutants have been detected in surface water, drinking water and soil there. However, organic pollution status of groundwater is unknown yet. This dissertation aimed to analyze the pollution characteristics of shallow groundwater, evaluate its pollution status, and probe into its pollution sources and influence factors, and carried out further studies on the adsorption behaviors of phthalate esters on typical soils under different environment factors.44 organic pollutants in shallow groundwater were chose to be tested. The results showed most of those pollutants are detected, and their detected concentrations were relatively low with only some exceeding drinking water quality standards.The exceeding multiple of benzene, total DDT and dieldrin were 1.6, 1.37 and 7.0, respectively. The main organic pollutants are benzo (a) anthracene (66.07%), PCE (42.64%) and dieldrin (39.29%). The organic pollution characteristic of shallow groundwater was point distribution, and the groundwater samples gotten over 30m away from pollution source were hard to detect organic pollutants. The serious polluted points were mainly located in suburb and industrial region. The order of pollution degree in the three sub-study areas was C area > W area > S area.An organic pollution evaluation method was established and used to evaluate the organic pollution in study area. The results obtained from single factor pollution index method indicated that more than eighty percent of total indexes in both W area and S area lay in the uncontaminated level, and most of the rest were in the light contaminated level. The pollution degree in C area was relatively higher, and forty percent of most indexes were in the light contaminated level. The results gotten from general pollution index method demonstrated the shallow groundwater in the study area had been lightly polluted by halohydrocarbon and single-ring aromatics, and the chlorinated pesticide pollution in C area was heavier.Source identification showed that halohydrocarbon and single-ring aromatics were mainly related to the industrial pollution sources closely; the main source of PAHs in C area was fossil combustion fuel, and the main source of PAHs in W and S area were fossil fuel and oil pyrolysis; Some pollutants, including benzene hexachloride, dieldrin, aldrin and heptachlor epoxide, may be complemented by new sources besides its environmental residues. However, DDT, hexachlorobenzene and endrin mainly were orignated from their environmental residues.The lithology of unsaturated zone in the study area is fine with abundant organic matters, which can retard and adsorb a great number of organic pollutants. Furthermore, halohydrocarbon and single-ring aromatics are easy to evaporate. Therefore the pollution in the surface water was serious while that in the shallow groundwater was light.The results of the phthalate esters soil chromatographic column experiment showed that adsorption of phthalate esters on soil decreased with the temperature and pH increasing. But the intensity and type of the cation had different influences on adsorptions of phthalate esters which is hard to define.