有机氯农药在天津耕作土壤剖面中的分布

研究了天津耕作区典型土壤剖面中有机氯农药的分布特征,结果表明:在典型剖面的表层土壤中,六六六在菜地中的质量分数最高,其次是在高粱地、水稻田和玉米地;DDTs在菜地中的质量分数最高,其次是在高粱地,在水稻田与玉米地中的质量分数差别不大。有机氯农药质量分数在土壤剖面的纵向分布总体上是随着土壤剖面的加深而降低,有机氯农药的各个组分(α-HCH,β-HCH,γ-HCH,δ-HCH,DDE,DDD,DDT)质量分数也有类似的分布趋势。有机氯农药的物化性质、土壤黏粒含量、有机碳和微生物影响着它们在土壤剖面上的分布。六六六的4个异构体与原粉中各个异构体的质量分数相比有较大差异,这与4个异构体在土壤中的降解速度不同和各个异构体之间的转化有关。在表层土壤中w(DDT) w(DDTs)为0 033～0 188,远小于0 5,说明在这些耕作区中没有新的DDT污染。 

Vertical Distribution of Organochlorine Pesticides in Farming Soils in Tianjin Area

The distribution of organochlorine pesticides in soil profiles in the farming soils of Tianjin area was studied.The results showed that the highest concentration for hexachlorocyclohexance can be found in vegetable plot.Concentrations in the kaoliang field are the next,followed by paddy soil and corn field.For DDTs,the highest concentration is found in vegetable fields,followed by kaoliang field.No significant differences can be found for paddy soil and corn field.The concentrations of organochlorine pesticides decreased with depth,including all compounds of organochlorine pesticides such as α－HCH,β－HCH,γ－HCH,δ－HCH,DDE, DDD and DDT.The physical and chemical features of organochlorine pesticides,contents of clay minerals,organic carbon and microorganisms are major factors influencing the vertical distribution of the pesticides in soil.The percentages of four isomers of the hexachlorocyclohexance are significantly different from those in original pesticides.This can be explained by the fact that degradation speeds of the four isomers are different and transformation of these isomers existed in the soil.In the surface soil of the sampling sites,the values of w(DDT)/w(DDTs) range from 0.033 to 0.188,far below 0.5.It shows that no new contamination of DDT occurs in the sampling areas.