Residues of hexachlorocyclohexane isomers and their distribution characteristics in soils in the Tianjin area, China.

Hexachlorocyclohexane (HCH) has a history of use in China. This paper presents the results of an investigation of HCH residue isomers and their distribution characteristics in soils near Tianjin, China. One hundred eighty-eight soil samples were collected from the Tianjin area. Four HCH isomers-alpha-HCH, beta-HCH, gamma-HCH, and delta-HCH-were detected using gas chromatography for all samples. Concentrations of the sum HCH ranged from 1.3 to 1095 ng g(-1), among which beta-HCH accounted for 52.5%. In addition, residues of HCH within Tianjin's urban areas were found to be higher. No significant differences were found between the residues of HCH in soils from waste irrigation areas and those in other areas. Total organic carbon content was determined to impact the residue levels of HCH in soils, while pH value and clay content were not related to concentrations of HCH. In general, all HCH isomers in soil samples had abnormally high residue levels, possibly the result of continuous use of HCH in this area.