Residues of Organochlorine Pesticides in Shallow Groundwater of Agricultural Region in Taihu Basin

Totally 56 shallow groundwater samples collected from agriculture region in Taihu basin were analyzed by using GC/ECD. Among the 14 compounds to be analyzed in those samples,13 components were detectable except p,p'-DDT. The highest detected rate was 39.29% for dieldrin,next to which was 33.93% for hexachlorobenze,and the lowest was 8.93% for r-HCH and endrin. The detectable concentrations of them ranged from 0.000 4 μg·L-1 to 1.37 μg·L-1 while the average concentration of each detected compounds ranged from 0.003 μg·L-1 to 0.144 μg·L-1. The concentrations of the total HCHs and endrin in some samples were above their corresponding water-quality standard for drinking while those of others were far lower than their standards for drinking. The distribution of detected organochlorine pesticides was related with soil cultivated style and water quality in rivers. The ratio of α-HCH to γ-HCH ranged from 0.10 to 0.36 with an average of 0.20,and the ratio of dieldrine to aldrin ranged from 0.17 to 36.14 with an average of 13.28. The ratio of heptachlor to heptachlor expoxite ranged from 17.52 to 83.42. The results indicated that HCHs,endrin and heptachlor might have other pollution sources in addition to these residues. The pollution source of endrin,HCB and so on in shallow groundwater were due to residue source.