可溶性有机碳下渗过程及其对根层以下土壤反硝化脱氮的强化机制

Nitrate accumulation in deep soil is one of the most serious environmental problems in the high-yielding intensive farmland in the North China Plain. Strengthening soil denitrification beneath the root zone is a significant way for decreasing the risk of nitrate contamination of groundwater in the area with high accumulation of nitrate. Thorough investigation on the infiltration prosess of dissolved organic carbon (DOC) in soil profile and its effects on soil denitrification will provide theoretical basis for removing the accumulated nitrate beneath the root zone and controlling nitrate contamination of groundwater. The purpose of the project is to illustrate the process of DOC infiltration and its mechanisms for strengthening deep soil denitrification. Based on the DOC in-situ infiltration experiment and the long-term residue retention field experiments,the emission rates of soil N2, N2O and NO will be directly determined by the soil gas automatically sampling and analyzing system under the same conditions of soil water content，temperature and oxgen content as in the field，the contribution of DOC infiltration to strengthening deep soil denitrification will be quantified. The project will provide theoretical basis and optional technological approaches for crop residue management and prevention of groundwater from nitrate contamination.

深层土壤硝态氮累积已成为华北平原高产集约农田最严重的环境问题之一，强化根层以下土壤反硝化脱氮是降低这一地区地下水硝态氮污染风险的重要途径。深入研究可溶性有机碳在土壤剖面的下渗过程及其对土壤剖面反硝化的强化机制可为移除根层以下土壤累积的硝态氮、阻控地下水硝态氮污染提供理论依据。本项目以华北平原硝态氮高积累农田为研究对象，以阐明田间条件下可溶性有机碳下渗过程以及根层以下土壤反硝化过程的响应机制为目标，依托可溶性有机碳裸地原位入渗实验与秸秆还田长期定位实验，利用土壤气体自动采集与分析系统，在与田间湿度、温度与氧气含量相同的条件下测定土壤氮气、氧化亚氮与一氧化氮的排放速率，定量研究可溶性有机碳下渗在强化根层以下土壤反硝化脱氮方面的贡献，为制定合理的作物秸秆田间管理措施、阻控地下水硝态氮污染提供理论依据与潜在的技术途径。

本项目以华北平原硝态氮高积累农田为研究对象，以阐明田间与室内控制条件下可溶性有机碳下渗过程以及根层以下土壤反硝化脱氮速率与反硝化气态产物构成的响应机制为目标，将可溶性有机碳裸地原位入渗实验与有机碳源室内添加实验相结合。利用土壤气体自动采集与分析系统（Robot系统），深入研究了深层土壤反硝化脱氮的限制因素与强化机制。主要研究成果包括：（1）探明了限制深层土壤反硝化脱氮的关键因素。（2）明确了室内人为引入可溶性有机碳源后深层土壤反硝化潜势、反硝化脱氮总量与反硝化气态产物构成的响应规律。（3）阐明了利用秸秆腐解产生可溶性有机碳源，原位灌溉可溶性有机碳源对深层土壤反硝化潜势与反硝化气态产物构成的影响机制。本项目初步揭示了可溶性有机碳源（如秸秆腐解液）作为反硝化电子供体强化深层土壤反硝化脱氮的机制，为制定合理的作物秸秆田间管理措施、消减作物根层以下植物难以吸收利用的硝酸盐、阻控地下水硝态氮污染与减少温室气体氧化亚氮排放提供新的理论依据与潜在的技术途径。核心数据已经发表项目标注SCI论文8篇（其中包括Soil Biology & Biochemistry 4篇），获得授权专利两项。在项目执行期间，项目主持人获得河北省杰出青年科学基金资助(D2015503012)，入选中国科学院青年创新促进会会员，入选福建省引进高层次人才与福建农林大学金山学者特聘教授。