农药生产场地DDTs纵向迁移及蓄积层形成机理研究

It is widely believed, and supported by a large number of studies, that the hydrophobic organic pollutants, such as DDTs, are generally difficult to migrate into deep soil strata. However, our previous studies have found that there existed high concentrations of DDTs underneath more than ten meters in some pesticides producing sites where high concentrations of BTEX coexist with DDTs. Both DDTs and BTEX could accumulate in the silt zone and near the saturation zone. The same case was also reported in other sites of other countries. However, the cause for DDTs migration and accumulation in deep soil strata remains unknow. According to our previous study and investigation, we suspect that the distribution and migration of DDTs in the soils was closely related to the coexistence of DDTs and BTEX. Currently, little research has been carried out to investigate the leakage and deep migration of DDTs in different soil types. Especially, studies on the controlling factors of DDTs migration and diffusion in soil, and the influence of organic solvent coexistence, are greatly needed. A combined research of in situ site investigation and laboratory soil column leaching experiment are helpful. An integrated selection of clay, silt, sand, and other soil matrix are useful for exploring the dominant factors influencing DDTs diffusion and migration in the soil. The effects of organic solvent coexist on DDTs migration to deep soil layers will be helpful to reveal the mechanisms for DDTs diffusion and migration in the deep soil.

大量研究显示，疏水性有机污染物滴滴涕(DDTs)，在土壤中难于扩散和迁移。但是我们野外探测发现，生产场地十几米深处有较高的DDTs蓄积，粉土层和近饱水带为富集区，并发现高浓度的苯系物(BTEX)共存其中，国外一些实际探测也发现类似现象，但是深层蓄积的原因还不清楚。经过分析，我们怀疑BTEX对DDTs的迁移扩散起了一定作用。目前，DDTs在土壤中的残留和环境行为的研究主要集中在农田浅层土壤，关于生产场地DDTs泄露并迁移到土壤深层的研究较少，尤其是DDTs在土壤中迁移扩散的主导因素研究和有机溶剂共存影响的研究尚未报道。本项目将场地探测与实验室土柱淋溶实验相结合，采用黏土、粉土、沙土为介质控制土壤性质的影响，通过DDTs和BTEX在不同岩性土层迁移的动力学研究，探寻DDTs在土壤中迁移的有机溶剂影响，研究促进DDTs在不同土质中扩散迁移的主导因子，揭示农药生产场地DDTs蓄积层形成的机理。

在国家自然科学基金的资助下，承担了“农药生产场地DDTs纵向迁移及蓄积层形成机理研究”(2014-2017)项目。研究内容是将场地探测与实验室土柱淋溶实验相结合，采用黏土、粉土、沙土为介质控制土壤性质的影响，通过DDTs和BTEX在不同岩性土层迁移的动力学研究，探寻DDTs在土壤中迁移的有机溶剂影响，研究促进DDTs在不同土质中扩散迁移的主导因子，拟揭示农药生产场地DDTs蓄积层形成的机理。在该基金资助下，开展了创新性研究，发现了一些有意义的现象，并得到创新性结论。2篇研究论文在ES&T上发表。.DDT很容易富集在粘土层和含水层底板，甚至浓度比其上层还高。Dicofol生产场地不可用DDE/DDD判断降解条件，也不可用(DDE +DDD)/DDT 评估土壤中残留时间。长期以来，用“新”和“旧”判断残留DDTs来源的模棱两可概念已经解释清楚。在去除dicofol-type DDT的影响的DDT在土壤中的持久性和归趋得到详细分析和研究。DDT在表层土壤和深层土壤的降解率有显著差异。并给出表层土壤中DDT的半衰期为14.2±0.9年。