Residues of Organochlorine Pesticides (OCPs) in Agricultural Soils of Zhangzhou City, China

A soil survey was conducted in Zhangzhou City, an important agricultural region in south of the Fujian Province, China. 93 surface soil samples were collected in the paddy fields, vegetable lands, orchards and tea plantations from Zhangzhou City. An additional soil profile was sampled in a paddy field as previous research had indicated high concentrations of organochlorine pesticides (OCPs) in the paddy fields. Dichlorodiphenyltrichloroethanes (DDTs) ranged from 0.64–78.07 ng g−1 dry weight and hexachlorocyclohexanes (HCHs) ranged from 0.72–30.16 ng g−1 dry weight in the surface soil of the whole study region. Ratios of α-HCH/γ-HCH < 4 and o, p′-DDT/p, p′-DDT > 1 in all soil samples suggested that lindane and dicofol were widely applied in this region in the past. Concentrations of HCHs and DDTs in soils from the four land use types followed the orders: paddy fields > vegetable lands > tea plantations > orchards and tea plantations > orchards > paddy fields > vegetable lands, respectively. Analyses of the data showed no correlation (r < 0.1) between elevation and OCPs contents in paddy fields, orchards and vegetable lands, indicated no significantly different features in distribution of HCHs and DDTs in the soils from low lying plains and mountains and the unsystematic usage of OCPs, and highlighted the fragmented nature of agricultural production in Zhangzhou, as well as the reemission of OCPs from the soils, where high OCPs concentrations were found, in Longhai of Zhangzhou. In addition, no obvious relationship between the OCPs and total organic carbon (TOC) (r < 0.3) was observed in the soil profile. The mean contribution of dicofol in total DDTs was 66% in the whole Zhangzhou region. The approximate burdens of HCHs and DDTs in the surface layer of 0–20 cm were 0.44 and 1.55 t, respectively. The storage of both HCHs and DDTs in soil surface layer (0–20 cm) accounts for 40% burden of the soil layer of 0–50 cm (1.10 t HCHs and 3.87 t DDTs), in which the highest concentrations of OCPs were observed in soil profile.