氮、钾肥料对再生水灌溉土壤重金属运移特性的影响及调控机制

Growing water shortages pose a growing threat to agricultural production safety, and rapid urbanization and industrialization releases enormous volumes of reclaimed wastewater, which is increasingly utilized as a valuable resource for irrigation in agriculture. The impact of heavy metals on the food safety and soil ecological safety under the effect of treated municipal wastewater becomes one of hot topics of the safe use of reclaimed wastewater in agriculture. Nitrogen and potassium fertilizer has a significant impact on transfers and transformations of heavy metals irrigated with reclaimed wastewater, but the mechanism has yet to be completely defined and there is a need for further study on the regulatory mechanism. Our previous research had suggested that different nitrogen and potassium fertilizers affect the Cu and Cd concentrations in ryegrass significantly under the effect of treated municipal wastewater, but the exact mechanisms are still unclear. Micro field plot experiment and soil column will be used to study the effect of different nitrogen and potassium fertilizer on transfers and transformations of heavy metals, micro-ecological environment. The soil heavy metals dynamic process of migration and the vertical transport characteristics will be studied through soil column method, in order to expound the regulatory mechanism of nitrogen, potassium fertilizer and their interaction effect on transfers and transformations of heavy metals irrigated with reclaimed wastewater. This study will provide a solid new theoretical foundation for the safe use of reclaimed wastewater in agriculture and the eco-environmental protection.

随着水资源短缺矛盾不断加剧，作为替代水资源的再生水农业利用将日益受到重视。再生水灌溉重金属对食品和土壤生态安全的影响已成为研究热点。再生水灌溉下不同氮钾肥种类会影响重金属在土壤中的迁移转化，但其机理尚未明确，影响及调控机制也有待于深入研究。申请者前期研究发现施用不同氮钾再生水灌溉黑麦草对Cu、Cd吸收有显著差异，但机制尚不清楚。本研究将利用大田微区试验与土柱试验相结合的方法，以西红柿为研究对象，重点研究不同氮、钾肥种类及混施对再生水灌溉重金属在作物-土壤系统中赋存形态、迁转特性及对土壤微生态环境的影响，并通过土柱淋洗试验研究再生水灌溉重金属在土壤中迁移的动力学过程和其在土壤中的行为与归宿，阐明不同氮钾肥种类及交互作用对再生水重金属植物有效性的影响差异及机理，进而从理论上阐明施用氮钾肥对再生水灌溉土壤重金属迁移转化的调控机制。该研究将为再生水农业安全利用及生态环境保护提供新的理论基础。

本研究通过采用田间微区定位试验、桶栽试验与室内化验分析相结合，重点研究不同种类氮、钾肥料及其伴随离子对再生水灌溉植物根际非根际土壤重金属迁移转化、番茄生理响应过程和农产品品质的影响机理及差异性。1、短期施钾肥对再生水灌溉重金属迁移转化的影响研结果表明：（1）再生水灌溉条件下，配施K2CO3、KH2PO4可有效降低土壤pH、增加土壤氧化还原电位，并可增加0-10cm土层有机质含量；（2）再生水灌溉条件下，施加KH2PO4时不同土层、根际土和非根际土中Pb、Cu有效态含量和全量低于其他处理；施加K2CO3和K2SO4时根际土与非根际土中Cd、Zn全量累积和有效态含量低于其它处理；再生水灌溉条件番茄果实Pb、Cd含量均未超出《食品安全国家标准 食品中污染物限量》（GB 2762─2016）新鲜蔬菜Pb、Cd限值标准（0.1mg/kg、0.05mg/kg）；（3）再生水灌溉条件下，施加KH2PO4时蕃茄果实维生素C含量最高；施加K2CO3和K2SO4处理蕃茄果实蛋白质、有机酸含量较高；施加KH2PO4和K2SO4处理蕃茄果实可溶性糖、糖酸比含量较高；施加KH2PO4、KCl番茄单株产量较高。2、长期施钾肥对再生水灌溉重金属迁移转化的影响研结果表明：（1）再生水灌溉条件下，施加钾肥土壤Cd累积含量均远低于《土壤环境质量 农用地土壤污染风险管控标准》（GB 15618-2018）农用地土壤风险管控值，番茄果实均未超出新鲜蔬菜Cd限值标准；（2）再生水灌溉条件下，可通过选择施加适宜的钾肥种类，调控重金属Cd在土壤-作物系统的分布及其生物有效性，施加K2SO4较KCl相比，可一定程度降低土壤Cd全量及有效态Cd含量。3、长期施氮肥对再生水灌溉重金属迁移转化的影响研究结果表明：（1）再生水灌溉条件下，施加氮肥土壤及番茄果实中Cd含量均未超过国家标准；（2）再生水灌溉条件下，施加尿素可一定程度降低土壤Cd全量及有效态Cd含量，调控重金属Cd在土壤-作物系统的分布及其生物有效性。