土壤中可离子化农药存在形式对其生物有效性的影响机制及表征

土壤中农药的生物有效性是其生态风险评估的关键。通常认为土壤孔隙水中农药是对土壤中生物体有效的部分,能表征农药的生物有效性。然而，可离子化农药的存在形式不但影响吸附，吸附平衡时孔隙水中的部分也具有不同的生物活性，两者共同作用对生物有效性的影响仍然是不清楚的。前期研究表明，当土壤中弱酸性除草剂烟嘧磺隆和弱碱性杀菌剂多菌灵的存在形式不同时，孔隙水浓度不能很好的评价其生物有效性。本研究将继续以烟嘧磺隆和多菌灵为研究对象，研究土壤和可溶性有机质对其不同存在形式吸附的影响，不同存在形式对农药生物毒性和生物富集的影响，动植物分泌物对土壤pH及孔隙水浓度的影响，土壤pH对可离子化农药生物有效性的影响，综合阐明土壤中可离子化农药不同存在形式对生物有效性的影响机制，并探索用固相微萃取、三油酸甘油酯-醋酸纤维素复合膜和中空纤维支载液膜微萃取等仿生技术来表征土壤中可离子化农药的生物有效性。

The bioavailability of pesticides in soil is the key in assessing the pesticide ecological risk. It is generally accepted that organisms can take up pesticide that are present in the pore water, and the pore water concentration has been used to estimate the bioavailability. However, for the pesticides which possess either an acidic or a basic functional group, they can be exist in neutral or ionic form in soil depending on soil pH. The influence of different speciation states not only on the adsorption by soil, but also the bioactivity of the pesticide presented in pore water at adsorption equilibrium. The influence of both the adsorption and bioactivity on bioavailability in soil is not clear. Our previous studies indicate when the weak acid herbicide nicosulfuron and weak base fungicide carbendazim exists as different species, the pore water can not estimate the bioavailability. In the present study, the nicosulfron and carbendazim will be studied as the mode ionizable pesticide, the influence of speciation states on adsorption by soil and dissolved organic matter, uptake by organism and the bioavailability in soil will be studied to understand the mechanism by which the bioavailability was affected by speciation states. In addition, the influence of the excreta from animal and plant on the soil pH and pore water concentration also be studied to understand the mechanism. Finally, the biomimetic method matrix solid-phase microextraction, triolein-embedded cellulose acetate membranes and hollow fiber based liquid phase microextraction will be used to estimate the bioavailability of ionizable pesticide in soil.