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.
Soil samples collected from several sites along an altitudinal transect on the eastern slope of the Tibetan Plateau were analyzed for hexachlorobenzenes(HCHs) and dichlorodiphenyltrichloroethanes(DDTs).The results showed that HCHs and DDTs were found in the soil samples from the remote high altitude areas away from source regions,which confirmed the long-range atmospheric transport phenomenon of these organochlorine pesticides(OCPs) insecticides.The OCP concentrations in the soils had a significant negative correlation with altitude;they showed a trend to increase with decreasing altitude,but the increase was not continuous,being interrupted at some moderate-altitude sites on the transect.The distances from the source region,landforms,soil properties,and physical-chemical properties of OCPs were more important than total organic carbon content to the distribution of OCPs in soils disturbed by human activities.An analysis of the compositions of HCH isomers and DDTs revealed predominantly low ratios of α-HCH to γ-HCH,ranging from 0.06 to 4.79,which suggested current lindane inputs.On the other hand,low p,p-DDT/p,p-DDE and o,p-DDT/p,p-DDT ratios were observed,indicating mainly aged historical DDT residues in the study area.
XING Xin-LiQI Shi-HuaZHANG YuanYANG DanJ. O. ODHIAMBO
