基于冰微结构的湖库冰生、消过程中有机氯农药的多介质迁移机理及模拟研究

During ice-on period of lake and reservoir, the material exchange in the air-water interface is stopped and the energy exchange is weakened. In addition, the light transmittance and heat conductivity among air-ice-water-sediment system are also changed. So the migration process of organochlorine pesticides(OCPs) during ice-on period must be different from that of during the ice-free period. The Menlou Reservoir in Yantai is selected for study object. The level of OCPs pollution of Menlou Reservoir will be studied to analyze the migration and distribution law of typical OCPs among air-ice-water-sediment system from the incisiveness of ice microstructure using thermodynamic and crystal chemistry theory. The indoor stimulation experiment will be carried out to reveal the effect of the ice microstructure on the migration behavior of OCPs and further to elucidate the migration mechanism of typical OCPs among air-ice-water-sediment system also from the incisiveness of ice microstructure. The migration processes of OCPs among air-ice-water-sediment system will be simulated through introducing the main environment phase of ice into fugacity model which is based on MATLAB. The research results can provide new thinking for studying on environmental behavior of organic pollutants during ice-on period, and also can provide data support for building the distribution model in a large range.

湖泊和水库冰封期冰层的存在几乎切断了大气-水体间物质交换，削弱了两者间的能量交换，进而改变了整个体系的透光性和热传导性，因此，湖库冰封期有机氯农药（OCPs）的迁移过程必有其特殊性。该项目以门楼水库为研究对象，从冰微结构切入，通过对冰生、消过程进行现场观测，分析OCPs在气-冰-水-沉积物多相介质间的迁移、分配规律；通过开展室内物理模拟实验，运用热力学和结晶化学理论揭示冰微结构对OCPs迁移行为的影响，进而阐明OCPs在多相介质间的迁移机理；将冰这一环境主相引入到逸度模型中，运用MATLAB等手段，实现OCPs在气-冰-水-沉积物多相介质间迁移过程的模拟。该研究以期为水体冰封期有机污染物环境行为的研究提供新的思路，为建立较大范围的OCPs分布预测模型提供数据支持。

冰封期长是我国北方和高纬度地区重要的水文特征。冰封期冰层的存在几乎切断了大气-水体间物质交换，削弱了两者间的能量交换，进而改变了整个体系的透光性和热传导性，因此，结冰和融冰过程中有机氯农药的迁移过程必有其特殊性。该项目在农药使用现状调查的基础上，确定以阿特拉津、α-HCH、o,p'-DDT等有机氯农药为目标污染物；以阿特拉津为例，从冰微结构切入，探明结冰过程中阿特拉津的污染特征和迁移过程，进而阐明阿特拉津在冰-水体系的迁移机理；通过室内模拟实验研究了结冰厚度、冻结温度、初始浓度对阿特拉津在冰-水体系中分布的影响；以去除α-HCH、o,p'-DDT等有机氯农药为目标，设置了喷雾结冰和自上而下结冰两种结冰方式，探索了该机理在去除水中有机氯农药应用的可行性；通过联合运行VB与MATLAB程序，对三级和四级逸度模型进行稳态和非稳态的计算，完成了逸度模型程序的构建；由于仪器故障，还开展了铁、锰、钙、镁等金属元素和氨氮、硝酸盐、磷酸盐等营养元素迁移规律和效应的研究。研究结果表明：结冰过程中阿特拉津、α-HCH、o,p'-DDT等有机氯农药均由冰体向冰下水体迁移，并运用冰体的微观结构和温度-浓度相平衡图进行了解释；有机氯农药在冰相中的浓度分布为由上到下逐渐增大，结冰厚度、结冰温度、溶液初始浓度对冰相中阿特拉津的分布没有明显影响，但pH的影响较为显著，表现为由上到下逐渐减小；冰体在融化过程中，各类有机氯农药均在融冰初期大量释放，而后少量均匀的释放；该机理可以作为应用于去除水体中有机氯农药的水处理方法，该方法具有处理效果好、流程简单、操作方便，无需添加任何药剂，耗能低或可直接采用自然冷能和太阳能，无二次污染等优点；结冰过程中铁、锰、钙、镁等金属元素和氨氮、硝酸盐、磷酸盐等营养元素均向冰下水体迁移，加速了冰下水体水环境的恶化。该研究可为水体冰封期污染物环境行为的研究提供新的思路，为水中污染物质的去除提供了新的方法，为水体冰封期水环境管理提供借鉴。