厚包气带农田土壤硝酸盐污染反硝化自修复机理研究

Self-remediation through denitrification process plays an important role in removing accumulated nitrate in agricultural soil profile and decreasing the risk of groundwater nitrate contamination in thick vadose zones. So far, the capacities in denitrifying self-remediation of nitrate contamination in agricultural subsoils beneath root zones, have not yet been quantitatively evaluated. The involved mechanisms of environmental regulation and microbial driving have not been well understood. The project will be conducted in the typical agricultural filed in thick vadose zones. The denitrifying self-remediation of nitrate contamination in the whole soil profile (from topsoil to groundwater line) and its environmental regulation will be quantitatively investigated by incubating intact soil columns under the simulated in situ conditions, in situ monitoring the environmental parameters and analyzing the isotopic characteristics of soil N2O. The community structure, dominant population and function gene expression of soil denitrifying micro-organisms in the different soil layers of thick vadose zone will be explored using the techniques of soil molecular microbiology, such as PCR-DGGE, T-RFLP and RT-qPCR. The purposes of this proposal are to quantitatively evaluate the capacity in denitrifying self-remediation of agricultural soils in typical thick vadose zones and to illustrate the involved mechanisms on environmental regulation and microbial driving. The project will provide theoretical bases and potential techniques for removing the accumulated nitrate in agricultural soils and decreasing the risk of groundwater nitrate contamination in the thick vadose zones.

反硝化自修复作用在移除累积在厚包气带农田土壤剖面中的硝酸盐、降低地下水硝酸盐污染风险方面具有重要意义。目前对作物根系层以下厚包气带硝酸盐污染的反硝化自修复能力还缺乏定量评估，对其中的环境调控机制与微生物学驱动机制还缺乏深入研究。本项目以典型厚包气带农田为研究对象，采用原状土柱微环境模拟培养、环境要素原位动态监测、土壤N2O同位素自然丰度质谱分析等技术，定量研究典型厚包气带农田整个土壤剖面的反硝化自修复能力及其环境调控机制；利用高通量测序、定量PCR、PCR-DGGE、T-RFLP与RT-qPCR等土壤分子微生物学技术研究厚包气带农田剖面各层次土壤反硝化微生物群落结构、优势种群与反硝化功能基因表达规律，目的是定量评估典型厚包气带农田土壤剖面硝酸盐污染的反硝化自修复能力，阐明其中的环境调控机制与微生物驱动机理，为消减厚包气带农田土壤硝酸盐累积、降低地下水硝酸盐污染提供理论依据与潜在的技术支持。

反硝化自修复作用在移除累积在厚包气带农田土壤剖面中的硝酸盐、降低地下水硝酸盐污染风险方面具有重要意义。目前对作物根系层以下厚包气带硝酸盐污染的反硝化自修复能力还缺乏定量评估，对其中的环境调控机制与微生物学驱动机制还缺乏深入研究。本项目以典型厚包气带农田为研究对象，采用原状土柱微环境模拟培养、环境要素原位动态监测、土壤N2O同位素自然丰度质谱分析等技术，定量研究了典型厚包气带农田整个土壤剖面的反硝化自修复能力及其环境调控机制；利用分类学标记基因扩增子测序、宏基因组测序、定量PCR、稳定同位素示踪等土壤分子微生物学技术对厚包气带农田剖面各层次土壤反硝化微生物群落结构、优势种群与反硝化功能基因丰度分布规律进行了研究，定量评估了典型厚包气带农田土壤剖面硝酸盐污染的反硝化自修复能力，阐明了其中的环境调控机制与微生物驱动机理，研发了靶向移除深层土壤累积硝酸盐阻控地下水污染与温室气体排放的新技术。并以华北平原作为厚包气带的代表区域,实地取样分析了包气带硝态氮累积存储和分布特征，通过对华北山前平原区浅层地下水样品硝酸盐含量的测定, 结合水化学和硝酸盐氮同位素分析,在区域尺度全面解析浅层地下水硝酸盐污染分布的时空差异性特征和不同来源氮对地下水硝酸盐影响。为未来消减厚包气带农田土壤硝酸盐累积、降低地下水硝酸盐污染提供理论依据与潜在的技术支持。