苏南典型地区土壤中有机氯农药残留的空间分布及来源分析

本文研究了江苏张家港市土壤中有机氯农药六六六(HCH)和滴滴涕(DDT)的残留状况,用空间插值和GIS技术分析了其空间分布规律,探讨了潜在来源。结果表明,547个采样点中有21.94%的表层土壤样品中检出HCH,而DDT的检出率为96.16%。HCH在土壤表层的残留均低于《土壤环境质量标准》(GB 15618-1995)的二级标准(500 ng/g),超过一级标准(50ng/g)的也仅占1.46%,DDT则有0.55%的样品超过二级标准。HCH和DDT不同异构体的比值指示土壤中可能有新的来源,但主要还是与历史上的农药施用有关。空间上HCH在南部人为土区的含量要显著高于北部的雏形土区,DDT则相反,这一空间分布格局主要与不同地区的种植历史有关,HCH在人为土区的较高残留可能与历史上水稻种植有关,DDT在北部雏形土区的较高残留则与棉花种植关系较密切。

Distributions and Sources of Organochlorine Pesticides in the Soils of A Typical Area in the Southern Jiangsu Province

Total 547 topsoil samples(0-15cm in depth) have been systematically collected from the Zhangjiagang area of Jiangsu Province in this study,in order to investigate the concentrations of organochlorine pesticides(DDTs and HCHs) in soils and to discuss their spatial distribution patterns and possible sources by applying the technique of the inverse distance weighted interpolation in combination with GIS.The analytical results show that the HCHs have been detected in 21.9% of topsoil samples whereas the DDTs have been detected in 96.2% of topsoil samples.The HCH contents of all topsoil samples are lower than the stringent critical value(the 2nd grade value,500 ng/g) of Soil Environmental Quality Standard of China(SEQSC)(GB 15618-1995).Those of only 1.46% of topsoil samples exceeded the most stringent value(the first grade value,50 ng g-1).In contrast,the DDT contents of 0.6% and 49.5% of topsoil samples exceeded the 2nd and 1st critical values(500 ng/g and 50 ng/g) of SEQSC respectively.It is believed that the HCHs and DDTs in soils are mainly resulted from the residues of historical usage of organochlorine pesticides,though ratios of their different isomers indicate that a small part of organochlorine pesticides in soils could come from other sources.Generally,the HCH contents of the Anthrosols on flat fields in the southern part are obviously higher than those of the Cambisols in northern part,whereas the distribution of DDT has a controversial feature in comparison with the distribution of HCH.The different distribution patterns of HCHs and DDTs are mainly associated with the different soil utilization functions in history in these two parts of the area.The high contents of HCH residues in the Anthrosols could be resulted from the rice plantation,whereas high levels of DDT residues in the Cambisols could be closely associated with the cotton plantation.