污染土壤中六六六和DDT在温室中的分布特征及动态变化研究

应用PUF材料空气被动采样技术,研究了密闭温室条件下污染土壤中有机氯农药DDT和六六六（HCH）]含量的动态变化及其向空气中扩散的规律。结果表明：土壤中∑HCHs和∑DDTs总量随着培养时间的延长而降低;空气中HCH和DDT浓度在20d时达到峰值,20d以后浓度逐渐降低。培养60d后,土壤中∑HCHs的浓度随土层深度增加而增加,0~2cm土层中∑HCHs的浓度（9.4±0.69）mg·kg-1显著低于6~8cm土层中的浓度（12.11±0.83）mg·kg-1;∑DDTs在土壤中浓度随土壤层次呈现先升高后降低的变化趋势。在温室条件下有机氯农药的异构体和降解产物的组成也发生一定变化,土壤中HCHs和DDTs在一定程度上被激活,温室条件也可能促进HCHs和DDTs的土-气交换过程;温室环境促进了p,p′-DDT和o,p′-DDT向p,p′-DDD和p,p′-DDE转化,从而增大DDT和HCH的环境风险。

Spatial Distribution and Dynamic Change of the Organochlorine Pesticides DDTs and HCHs in Contaminated Soils Under Greenhouse Conditions

The spatial distribution and the dynamic change of the organochlorine pesticides（OCPs）including DDTs and Hexachlorocyclo- hexanes（HCHs）in greenhouse were studied by laboratory simulation method. Passive air samplers based on polyurethane foam（PUF）was used in the study. Results showed that the total concentration of OCPs decreased during the whole period of two months in plastic greenhouse soils, and that the concentration of HCHs and DDTs attained peak values with mean of 29.05 μg·m-3 and 78.90 μg·m-3, respectively, in air at the peroid of 10～20 d and decreased after 20 d and tend to balance gradually in air of plastic greenhouse. As for the concentrations of DDTs and HCHs in soils, an apparent difference of distribution among different soil layers was observed. After the test of 60 d, the concentrations of HCHs had a more decrease in the layer of 0～2 cm（9.4 mg·kg-1）than those of 6～8 cm（12.11 mg·kg-1）, while the concentrations of DDTs de- creased along with the soil depths and the concentrations in the layer of 0～2 cm were significantly lower than those in the other layers of 2～4 cm, 4～6 cm and 6～8 cm. This was partly interpreted by HCHs having a higher volatility than DDTs. The oblivious variation of composition of HCH isomers and DDT degradation products was observed in the different period. The results implied that there was an apparent trend of the activation of aging OCPs and the promotion of air-soil exchange process promoted in soils, therefore, the environmental risk of OCPs in closed conditions should be deserved more attention on plant growth and human health.