我国西南地区森林土壤中有机氯农药和多氯联苯残留的初步研究

A Preliminary Study on Residues of Organochlorine Pesticides and Polychlorinated Biphenyls in Forest Soils of Southwest China

对西南地区森林土壤中有机氯农药和多氯联苯的分布和剖面进行了区域尺度分析。相比较发达国家和地区,我国西南地区森林土壤中有机氯农药含量水平较高,多氯联苯则相对较低。这与我国此类持久性有机污染物历史使用情况吻合。多氯联苯和有机氯农药在腐殖质层的含量一般高于表层土壤中,说明淋溶作用导致污染物向下移动。DDTs和HCHs是土壤样品中有机氯农药的主要成分,说明我国历史上长期施用农药对森林土壤农药的组成有显著影响。环境参数(包括TOC、降雨量和海拔高度)对大多数有机氯农药的区域空间分布的作用并不显著,周边污染源是控制有机氯农药在腐殖质层土壤中分布的关键因素;尤其是DDTs,比值分析结果显示仍有新鲜的工业滴滴涕输入。多氯联苯在腐殖质层中的含量明显要高于其在表层土壤中的含量,多氯联苯在土壤中的空间分布和土层中的垂直分布主要受土壤TOC含量的控制。以大气干湿沉降来源贡献为主的多氯联苯与土壤中的有机质有效结合会降低它们的再挥发过程,表明西南地区山地森林对多氯联苯具有一定森林过滤效应。

The regional distributions and profiles of organochlorine Pesticides(OCPs)and Polychlorinated biphenyls(PCBs)in forest soils from southwest China were analyzed.The concentrations of OCPs in the study area were at a higher level compared with those in background areas,which is consistent with the heavily application of OCPs in China,but concentrations of PCBs were relatively lower.The concentrations of PCBs and OCPs in the humus layer soil were generally higher than those in the surface soil,partly due to the leaching effect.DDTs and HCHs were the main components of OCPs in soil samples,indicating that the long-term application of pesticides in China had a significant impact on the composition of OCPs in forest soils.Environmental parameters(including TOC,rainfall and altitude)have no significant effect on the regional spatial distribution of most OCPs.The distribution of OCPs in the humus layer soil was mainly controlled by surrounding pollutions of pesticides.The DDTs ratio analysis indicated that fresh industrial DDT inputs still existed.The concentrations of PCBs in humus layer soils were significantly higher than those in surface soils,and the spatial distribution and vertical distribution of PCBs in soils were mainly controlled by the TOC content.PCBs,mainly derived from atmospheric dry/wet depositions,can effectively combine with organic matter in soils and reduce their re-volatilization.The result also suggests that mountain forests in southwest China have a certain cold trapping effect on PCBs.