稻改草后土壤中DDT及其代谢产物的动态变化

用盆栽方法研究了DDT及其主要降解产物在水稻土改种草后土壤中的残留动态，比较了植黑麦草土壤与未植草土壤中DDT残留的差异。盆栽试验设计3种DDT处理浓度，分别为0、0．5、5．0mg kg^-1，每处理4次重复。研究表明，DDT的残留量随着时间的增加而不断减少，且前期降解速率比后期快。在试验的第81天，DDT浓度为0．5、5．0mg kg^-1的植草土壤中，DDT分别减少了27．24％、20．50％。比较植黑麦草和未植黑麦草土壤，p，p′-DDT残留量在试验的16d、32d、64d、81d均出现显著性差异。这可能与植物释放到根际的酶和有机分泌物能有效地促进农药降解有关。同时，DDT的代谢产物DDE随着时间的增加而逐渐增加。

DYNAMIC CHANGES OF DDT AND ITS METABOLITES IN PADDY FIELDS SHIFTED TO GRASSLAND

A pot experiment was conducted with different DDT concentration,i.e.0,0.5,5.0 mg kg^-1 respectively,to study residue dynamics of DDT and its main metabolites in paddy soils with and without ryegrass growing.The total growth period was 81 days.The results indicated that the residue of DDTs decreased steadily with the time and at a greater rate in the earlier stage.Compared to the soils without ryegrass growing,DDTs in the soils under ryegrass growing decreased by 27.26% and 20.50% respectively by the end of the experiment,for the 0.5 and 5.0 mg kg^-1 treatments,and significant differences in p,p DDT residue were observed on the 16th,32th,64th and 81th day.It could be contributed to the release of enzyme and other organic secretions from plant root systems,which could effectively stimulate degradation of DDT.Additionally,DDE in creased gradually along with the time.