畜禽粪便热解生物炭内源重金属在酸性土壤中的迁移转化机制研究

Animal manure is one of the main causes of agricultural non-point source pollution, the pathogenic bacteria and antibiotics in animal manure presented threat for environment and human health. Pyrolysis provides a safe method for the management and utilization of animal manure due to the complete destruction of pathogens, thorough decomposition of antibiotics and additional gain of clean energy under high temperature. However, the gathering of heavy metals in animal manure biochar during pyrolysis limits its application for farmland. In this project, pig and chicken manure will be chosen as representative animal manure to studies the influence of pyrolysis conditions on the basic physicochemical characteristics, the heavy metals speciation and bioavailability of animal manure biochar. Meanwhile, to interpret the migration and transformation behaviors of heavy metals in acid soil, the interfacial behavior and molecular mechanism of heavy metals at the surface of biochar and soil particles, the leachability of the heavy metals in animal manure biochar and the accumulation of heavy metals in plants will be explored. Moreover, the correlations between the characteristics of soil and animal manure biochar and the availability of heavy metals in soil will be developed to obtain the main factors affecting the migration and transformation of heavy metals in animal manure biochar in acid soil. A comprehensive study on the migration and transformation mechanism of heavy metals in animal manure biochar produced in various pyrolysis conditions would be conducted, which is expected to provide theoretical supports to the safe and efficient management and utilization of animal manure.

畜禽粪便是农业面源污染的主要原因之一，其携带的大量致病菌和抗生素，对生态安全和人类健康构成巨大威胁。热解因可高温杀灭病原菌，彻底分解抗生素，获得清洁能源，为畜禽粪便无害化处理和利用提供了一条安全绿色的途径。但热解过程使得畜禽粪便重金属在生物炭中富集，限制了生物炭的农田应用。本项目以猪粪和鸡粪为研究对象，研究热解条件对生物炭基础理化特性及重金属形态和生物有效性的影响规律；探究生物炭内源重金属在酸性土壤中的界面过程及分子机理、淋溶特性和对作物重金属积累的影响，揭示重金属在酸性土壤中的迁移规律；分析土壤和生物炭理化性质与土壤重金属生物有效性之间的相关关系，确定生物炭内源重金属在酸性土壤中迁移转化的主控因子。在此基础上，全面系统地阐明不同热解条件下畜禽粪便生物炭内源重金属迁移转化机制，该研究结果可为畜禽粪便无害化处理和资源化利用提供理论依据。

畜禽粪便是农业面源污染的主要原因之一，其携带的大量致病菌和抗生素，对生态安全和人类健康构成巨大威胁。热解因可高温杀灭病原菌，彻底分解抗生素，获得清洁能源，为畜禽粪便无害化处理和利用提供了一条安全绿色的途径。但热解过程使得畜禽粪便重金属在生物炭中富集，限制了生物炭的农田应用。针对上述问题，本项目研究不同热解温度（300-700℃）畜禽粪便生物炭内源重金属的含量、富集系数、形态分布及生物有效性，明确提出热解可促使畜禽粪便重金属由弱酸提取态与还原态转化为氧化态与残渣态，钝化重金属；结合不同热解温度畜禽粪便生物炭生态环境风险评价，提出500℃为畜禽粪便适宜的热解温度。基于实验室土壤培养实验、土柱淋溶实验及盆栽实验，成功揭示畜禽粪便生物炭施入酸性土壤后重金属的迁移转化规律，结果显示以磷酸盐形态存在的重金属Cu可与酸性土壤中H+发生中和反应，释放并进入土壤溶液，而Zn不会释放，氧化态Cu与Zn在酸性土壤中可向弱酸提取态及还原态转变，生物有效性增强；基于畜禽粪便生物炭对酸性土壤特性、作物生长状况及作物重金属积累影响规律，提出1%生物炭添加比例可作为畜禽粪便生物炭农田推广应用适宜的添加量。基于多区域酸性土壤样本的土壤培养实验，明确了酸性土壤pH是影响畜禽粪便生物炭内源重金属释放和迁移的主要因素。研究科学阐述了畜禽粪便生物炭内源重金属在生物炭-酸性土壤-作物系统中的迁移转化机制，研究结果可为畜禽粪便生物炭安全高效的农田推广应用提供理论指导。