Review of hexachlorocyclohexane (HCH) and dichlorodiphenyltrichloroethane (DDT) contamination in Chinese soils

Despite a ban on the production and use of organochlorine pesticides (OCPs) after 1983, serious OCP pollution still exists in the soil in certain areas of China because OCPs degrade very slowly. Based on a systematic review, we identified 136 relevant papers focusing on soil contamination from hexachlorocyclohexane (HCH) and dichlorodiphenyltrichloroethane (DDT) in China (published from 2001 to 2019). We compiled scientific data, extracted and analyzed relevant information, and summarized the pollution characteristics of HCH and DDT in Chinese soils found in two land use types: agricultural land and land for construction. Related studies on HCH and DDT in Chinese soils focus on the Beijing-Tianjin-Hebei region and the Yangtze and Pearl River Deltas, where agricultural soils are predominant. The average concentrations of both HCH and DDT in agricultural soils were generally lower than the risk screening value (100 mu g/kg) in most provinces in China, except for DDT concentrations in the Inner Mongolia autonomous region. However, in certain central and eastern regions, mean or maximum recorded DDT concentrations approaching or exceeding 100 mu g/kg were recorded. Regarding land for construction, soils with excessive concentrations of HCH and DDT were primarily observed at sites of operational or defunct pesticide factories. According to isomer and metabolite compositions, HCH and DDT at most sites originated from historical residues, but others may have been new inputs after 1983. Since 2015, the concentrations of HCH and DDT in agricultural soils in China have been decreasing, and those in the soils of land for construction (except for sites of operational or defunct pesticide factories) have not exceeded the standard after 2005. This indicates that the measures to prohibit the production and use of OCPs in China have been effective. However, the management of operational or defunct pesticide factories polluted by OCPs requires further improvement. (C) 2020 Published by Elsevier B.V.