宁夏引黄灌区农田面源氮磷迁移规律及其地表水水质响应机制

宁夏引黄灌区农业面源污染严重，灌区特殊的灌溉和排水特点导致典型种植体系下农田氮磷迁移、损失时空变异规律不清楚、损失量不确定性大，面源氮磷流失后在各级排水沟中的迁移路径、消纳过程、消纳规律和影响因素不明确，各级排水沟水质与农田氮磷损失之间的响应关系难以量化。基于上述科学问题，本项目拟通过布设典型种植体系农田和各级排水沟观测样带，利用膜进样质谱脱氮测定方法体系、氮氧双同位素分析和模型模拟等手段，开展以下三方面研究：1）通过田间观测实验，明确农田氮磷的损失途径和损失量及其对各级排水沟系氮磷负荷的贡献；2）利用遥感技术和脱氮过程原位测定方法，阐明面源氮磷沿各级排水沟的迁移路径和消纳规律；3）构建“农田氮磷排放-沟系沿程消纳-水质负荷”的全过程水质响应模型，明确各级排水沟水质对农田氮磷损失的响应机制。本项目的相关研究结果可为保障黄河流域宁夏段水质安全提供科学借鉴和理论依据。

Agricultural non-point source pollution is severe in the Ningxia irrigation region. Due to the irrigation and drainage characteristics therein, the nitrogen (N) and phosphorus (P) loss patterns as well as their spatial-temporal variations in cropland remain obscure, and the loss amounts are largely uncertain. Moreover, the transport pathways, removal processes, patterns and the associated influencing factors of NP in the different drainage ditches are unclear. Consequently, the quantitative response relationship between water quality in different drainage ditches and agricultural NP loss is hard to establish. To address the above questions, by choosing representative monitoring belt transects and using Geographic Information System (GIS), high precision N removal determination technique (i.e. Membrane Inlet Mass Spectrometer, MIMS), δ15N and δ18O analysis and model simulation, this project aims to perform the following investigations. Firstly, elucidating the NP loss pathways, and the contributions of NP loss to the water loading of different drainage ditches by intensive field experimental monitoring. Secondly, clarifying the transport pathways and ascertaining removal capacity of NP along different drainage by GIS and MIMS. Eventually, elucidating quantitative response relationship between drainage ditches water quality and agricultural NP loss by constructing a whole process model of “farmland NP loss-ditches removing-water loading”. Results of this project will deepen our understanding of NP pollution processes, and the relationship between surface water quality and agricultural NP loss, which will provide scientific basis for ensuring the safety of water quality in Ningxia irrigation region.