土壤有机磷农药/重金属复合污染的微界面行为机制与模拟

Combined pollution of organophosphorus pesticides and heavy metal was commonly found in agricultural soil. However, little information is available on the micro-interfacial interaction between these combined contaminants of glyphosate, chlorpyrifos, heavy metals and the soil solid composition of soil colloids and mineral. In this project, we are going to investigate the cosorption, desorption of these contaminants on soil solid surface and the interactions, competitions between the organic and the inorganic parts, by using surface analytical methods, Fourier transform infrared spectroscopy, Isothermal titration Calorimetry and X-ray photoelectron spectroscopy along with surface complexation model. We also design a series of soil column experiments to observe the mobility and co-migration of organophosphorus pesticides and heavy metals in soil solid phase and a batch of biodegradation experiments to analysis the hydrolysis of organophosphate in the presence of heavy metal. These investigations are prone to provide useful data on the toxicity and bioavailability of combined pollution and give practical information for accurate assess and remediation of soil pollution.

农业土壤常常受到有机磷农药与重金属的复合污染，而有机磷农药与Pb、Zn和Cd复合污染的土壤微界面行为还缺乏系统深入的研究。本项目拟采用农业用量较大的农药草甘膦、毒死蜱与常见重金属Cd、Zn、Pb为对象，借助表面复合物理论、土柱运移与降解实验，并结合表面分析技术、红外光谱、X射线光电子能谱和滴定微量热等现代仪器分析手段,研究有机磷农药、重金属与土壤胶体/矿物的共吸附的配位结合机理,系统分析有机无机复合污染物环境界面行为间的耦合机制，获取共存体系中，界面吸附反应的优化模型，阐明有机磷农药-重金属共存体系中，污染物的迁移及有机污染组分的生物降解规律。为预测pH和离子等因素发生变化环境中污染物的界面行为打下理论基础，为准确评价农业土壤复合污染提供科学参考。

选取典型土壤矿物高岭石、蒙脱石和针铁矿及代表性有机磷农药草甘膦和重金属镉、铅为研究对象，借助表面分析、红外光谱、X射线光电子能谱和等温微量热技术，研究了有机磷农药、重金属与土壤矿物共吸附的配位结合机理。在实验研究的基础上，构建土壤矿物和污染物共存的结构模型，运用密度泛函理论和分子动力学模拟，对复合污染体系中，草甘膦、甲基对硫磷与重金属共存时的微界面反应机制进行了模拟。取得如下主要研究结果：1）土壤腐殖酸的存在显著降低矿物对草甘膦的吸附；2）草甘膦的存在可促进土壤矿物对重金属Cd的吸附；对于重金属铅，草甘膦可通过磷酸基团与针铁矿配位，再通过氨基、羧基与Pb(II)形成螯合环。3）三种矿物对草甘膦的吸附均为放热过程，矿物对铅的吸附受焓驱动。复合污染体系，针铁矿对草甘膦-铅复合体的吸附主要是焓熵共驱动。4）密度泛函计算结果显示，草甘膦主要通过膦羟基与高岭石的铝羟基形成氢键而吸附。甲基对硫磷与高岭石铝氧八面体面形成氢键，而与硅氧四面体面通过范德华力吸附。5）分子动力学模拟发现，草甘膦磷酸根去质子化的双齿双核和磷酸根质子化的单齿单核构型是草甘膦在针铁矿界面吸附的主要形式。上述研究结果为有机磷农药-重金属复合污染土壤的风险评估以及土壤修复措施的制订提供了科学依据。项目已发表 SCI论文2篇，在投在审2篇，参加国内外学术会议5次，做口头报告2次，墙报3次。培养硕士研究生4名。