生物炭影响稻田土壤中酰胺类农药吸附、降解行为的生物化学机制

The chloroacetanilide herbicides contamination has received increasing attentions in recent years. Biochars, as new soil amendments, have been proved to increase atrazine adsorption and promote the reductive degradation of pentachlorophenol in soil. However its mechanism is still not very clear. The objects of this project were to study: the effects of biochar on adsorption and degradation behaviors of chloroacetanilide herbicides in paddy soil, and its mechanism. Biochars derived from different materials and produced under different temperatures will be used to study the effects of different biochar on adsorption and reduction behaviors of chloroacetanilide herbicides in paddy soil in this research. The batch experiments will be conducted to investigate the kinetics of homogeneous adsorption and reduction processes of chloroacetanilide herbicides in aqueous solution. The difference in surface characterization, structure and functional groups of different biochar will be determined to evaluate the structure effect on adsorption of chloroacetanilide herbicides. The soluble organic carbon materials of different biological components and electron shuttling ability will be determined to reveal the electron shuttling mechanism of biochar accelerated degradation of pesticides in soil. Based on these simulation experiments, paddy soil incubation with adding different biochar will be conducted to research the effect of biochar on adsorption, degradation behavior of chloroacetanilide herbicides in paddy soil. The relationship between soil properties, biochar characteristics and chloroacetanilide herbicides behaviors in paddy soil will be studied with the aim to reveal the key factor control the herbicides adsorption and degradation. It will be very important to more in-depth understand of the microscopic mechanisms of biochar affect soil contaminant migration transformed and to provide a theoretical basis for the control of paddy soil organic pollutants in soil environment.

酰胺类农药是重要的环境污染物，如何降低其在稻田土壤中的生态风险是环境科学研究的热点。有研究表明生物炭可以增加土壤对阿特拉津等农药的吸附，促进五氯酚等农药的还原降解，但作用机制并不清楚。本项目模拟体系下，利用批处理试验研究不同来源、不同温度制备的生物炭对典型酰胺类农药吸附、降解行为的影响，并分析生物炭结构、表面基团差异对酰胺类农药吸附动力学和热力学影响，揭示生物炭吸附有机污染物的结构-效应机制；测定不同生物炭材料可溶性有机质组分及其电子穿梭能力，分析与酰胺类农药降解速率之间的关系，揭示生物炭加速土壤酰胺类农药降解的电子穿梭机制。在此基础上研究稻田土壤-生物炭体系中酰胺类农药的吸附、降解行为，探讨生物炭、土壤性质与酰胺类农药土壤环境行为的关系，揭示其关键影响因子。这对深入理解生物炭影响土壤有机污染物迁移转化的微观作用机制具有重要的理论意义，并可为土壤有机污染物控制提供技术支撑。

本项目采用酰胺类农药异丙甲草胺为主要目标污染物，取得的重要结果如下：（1）采用模拟体系和批处理试验研究了不同来源、不同温度制备的生物炭（水稻壳生物炭和中药渣生物炭）对典型酰胺类农药异丙甲草胺吸附行为的影响。不同热解温度下制备的生物炭都对异丙甲草胺有较好的吸附作用，其中biochar-750的效果为最好，其吸附机理主要都与孔隙填充有关。而低温制备的水稻壳生物炭吸附机理主要与表面氢键充有关，水稻壳生物炭RH-300其表面的基团特别是Si–O–Si可能在其吸附异丙甲草胺中起到主要作用。低温制备的中药渣生物炭中biochar-300的吸附能力强于biochar-500，可能与其含有较多的有机质和低温热解后有机质残留的基团较多有关。（2）在生物炭菌体存在的模拟体系下，分析了生物炭和酰胺类农药降解速率之间的关系，揭示生物炭加速土壤酰胺类农药降解的电子穿梭机制。实验结果表明，不同的生物炭加入体系后均可以加快异丙甲草胺的降解。牛粪制备的生物炭无论高温还是低温对异丙甲草胺的降解速率的提高差异均不显著，尤其是NF-800，可能与其极强的吸附能力有关。水稻壳制备的生物炭加入体系以后，与铁氧化物和菌作用加快农药降解效果显著，低温制备的SDK-300效果更好。低温制备的水稻壳生物炭可以与铁氧化物和菌共同作用加速体系中农药的降解，利用低温制备的生物炭作为介体是一种经济有效的加速土壤中有机物污染物降解的方法。（3）研究稻田土壤-生物炭体系中酰胺类农药的吸附、降解行为，探讨生物炭、土壤性质与酰胺类农药土壤环境行为的关系，揭示其关键影响因子。这对深入理解生物炭影响土壤有机污染物迁移转化的微观作用机制具有重要的理论意义，并可为土壤有机污染物控制提供技术支撑。