摘要
Mianzhu--Aba profile, east of the Tibetan Plateau, was selected to study the occurrence of organo- chlorine pesticides （OCPs） along an altitudinal gradient. Dichlorodiphenyltrichloroethanes （DDTs）, hexachlorocy- clohexanes （HCHs） and Aldrin, Dieldrin and Endrin （Drins） in surface soils were detected in winter （March） and summer （July）. Soil concentrations （ng.g-1, dw） in winter and summer ranged as follws： DDTs, 0.37-179.16 and 0.32-42.57; HCHs, 0.14-10.76 and 0.55-32.71; Drins, N.D-3.99 and 0.02-6.93, respectively. Main soil OCPs were p,p＇-DDT, p,p＇-DDE, fl-HCH and Drins, among which Drins were rarely reported in current literature of the Tibetan Plateau. Higher OCP concentra- tions in the profile were attributed close to the agricultural fields of the Sichuan Basin, current lindane and non- dicofol DDTs inputs, and also long-range atmospheric transport from abroad. Soil OCP concentrations underwent obvious seasonal variation, with higher DDTs in winter and higher HCHs and Drins in summer. It may be caused by climatic conditions, summer monsoon type, and physico-chemical properties of such contaminants. Though ＂rest＂ phenomenon occurred in some sampling sites, HCHs and Drins showed an increasing trend with increasing altitude, while DDTs showed an evident decrease with increasing altitude. The altitudinal distribu- tions of OCPs were all consistent with previous findings in other mountainous regions. A primary fugacity analysis on OCPs soil-air exchange indicated that the profile may be secondary sources for HCHs and Endrin. As with Aldrin,Dieldrin, and DDTs, the profile may be both secondary sources and sinks.
Mianzhu--Aba profile, east of the Tibetan Plateau, was selected to study the occurrence of organo- chlorine pesticides （OCPs） along an altitudinal gradient. Dichlorodiphenyltrichloroethanes （DDTs）, hexachlorocy- clohexanes （HCHs） and Aldrin, Dieldrin and Endrin （Drins） in surface soils were detected in winter （March） and summer （July）. Soil concentrations （ng.g-1, dw） in winter and summer ranged as follws： DDTs, 0.37-179.16 and 0.32-42.57; HCHs, 0.14-10.76 and 0.55-32.71; Drins, N.D-3.99 and 0.02-6.93, respectively. Main soil OCPs were p,p＇-DDT, p,p＇-DDE, fl-HCH and Drins, among which Drins were rarely reported in current literature of the Tibetan Plateau. Higher OCP concentra- tions in the profile were attributed close to the agricultural fields of the Sichuan Basin, current lindane and non- dicofol DDTs inputs, and also long-range atmospheric transport from abroad. Soil OCP concentrations underwent obvious seasonal variation, with higher DDTs in winter and higher HCHs and Drins in summer. It may be caused by climatic conditions, summer monsoon type, and physico-chemical properties of such contaminants. Though ＂rest＂ phenomenon occurred in some sampling sites, HCHs and Drins showed an increasing trend with increasing altitude, while DDTs showed an evident decrease with increasing altitude. The altitudinal distribu- tions of OCPs were all consistent with previous findings in other mountainous regions. A primary fugacity analysis on OCPs soil-air exchange indicated that the profile may be secondary sources for HCHs and Endrin. As with Aldrin,Dieldrin, and DDTs, the profile may be both secondary sources and sinks.
