【作者】 吴雪；

【导师】 迟杰；

【作者基本信息】 天津大学 ， 环境科学， 2009， 硕士

【摘要】 本文选择美国环保局(EPA)和我国优先控制的持久性有机污染物有机氯农药为代表化合物,选取六六六(HCH)异构体α-HCH和γ-HCH这两种典型的有机氯农药为研究对象,在实验室模拟有机氯农药从沉积物向上覆水的释放,进一步探索沉积物-水界面物质交换规律,并且通过逸度模型对有机氯农药在沉积物-水界面的迁移释放进行了模拟。这对我们深入认识有机氯农药在沉积物-水界面的迁移释放行为具有十分重要的研究价值,为研究有机氯农药在多介质环境中的分布与归趋提供理论依据。实验结果显示,有机氯农药α-HCH和γ-HCH存在甁壁吸附现象,且在实验浓度范围内瓶壁吸附百分率呈指数形式下降。有机氯农药的挥发速率与其在水体环境中的浓度、温度等密切相关。有机氯农药在水体和沉积物中降解速度都很快,而且沉积物中有机氯农药含量较高时生物降解速度较快。研究还发现γ-HCH比α-HCH更容易降解转化。生物降解是水体和沉积物中的有机氯农药减少的主要原因,而且在进行模型计算时,需要得知有机氯农药的生物降解速率常数。有机氯农药从沉积物向上覆水中释放,初始阶段释放速度较快,而后释放速度减慢,最终达到稳定状态,这证明两相间的浓度差是有机氯农药从沉积物向上覆水释放的主要驱动力。纵向分布上,除了表层(0~2 cm)沉积物外,各层沉积物中有机氯农药含量变化不大。由于沉积物和间隙水之间浓度梯度的拉动,使得沉积物中的α-HCH和γ-HCH逐渐向间隙水中溶解和迁移,最终影响上覆水,从而表现出向上迁移的趋势。以α-HCH和γ-HCH为例建立III级逸度模型,计算出三组对比实验中沉积物-水界面迁移参数DSW和总水相扩散系数KT,这两个参数在不同环境条件下数值大小顺序为:厌氧组>好氧组>灭菌组。通过对本次实验模型参数的灵敏度分析发现,有机氯农药本身物理化学性质和环境条件是影响其从沉积物向上覆水中释放的主要因素。另外,环境温度会间接影响模型计算结果,因此在建立模型时要充分考虑温度的影响。更多还原

【Abstract】 In this paper,α-HCH andγ-HCH, two kinds of organochlorine pesticides (OCPs), which were listed as‘priority persistent organic pollutants’by the US EPA and China, were selected as typical contaminations. The diffusive release of OCPs from sediment to water in Haihe River was measured in laboratory, and the transport behaviors were revealed by using a multimedia (including water and sediment) fugacity model for the steady state conditions. It’s important to study the transport behaviors of OCPs between water and sediment, which can provide the theory basis for studying the distribution and fate in the multimedia environment.The results showed that the adsorption curves of OCPs declined of exponential form. The volatizing rate of OCPs was related to temperature and its concentration in the water. OCPs were degraded quickly in water and sediment, especially in sediment with high OCPs concentration. Besides,γ-HCH degraded more easily thanα-HCH. Decreasing of OCPs in water and sediment was mainly caused by biodegradation, and the biodegradation rate was a parameter of the multimedia fugacity model.The diffusive rate of OCPs from sediment to water decreased gradually, and finally reached a steady state. It showed that the concentration difference between water and sediment was the main driving force for OCPs releasing into overlaying water.In the vertical profile, except for the surface sediment (0~2 cm), the concentrations of OCPs in other layers showed little changes. The release ofα-HCH andγ-HCH from sediment to water was caused by the concentration difference between water and porewater.A fugacity model (Level III) for the steady state conditions was established and successfully applied to calculating the transport parameters (DSW, KT) ofα-HCH andγ-HCH, and the transport parameters were different under different environmental conditions consequently: anaerobic group> aerobic group> disinfection group. Sensitivity analysis showed that the physicochemical properties of OCPs and environmental conditions played important roles in transport of pollutants between water and sediment. Besides, the effect of temperature on transport of pollutants between water and sediment should be considerated.更多还原