农田排水沟渠水体-底泥中溶质氮分布特征试验研究

沟渠系统"过程拦截"是现阶段农业非点源污染控制和管理的重要手段.针对当前农田排水沟渠水体-底泥-植物系统内各介质间非点源溶质迁移转化机制不清的现状,本研究以天然沟渠为对象,以非点源溶质氮为例,通过2014年3月~2015年2月现场监测试验,分析了农田排水沟渠水体及底泥中非点源溶质氮的分布特征.结果表明,沿沟渠纵向,试验沟渠水体中总氮质量浓度、底泥中总氮含量均呈现一定程度递减趋势,表现出沟渠系统对非点源溶质的净化作用;水体中总氮质量浓度、底泥中总氮含量在沟渠横断面分布存在较大不均匀性,其分布特征与断面形态、流量变化过程、流速分布等因素有关,其中水体中总氮质量浓度均衡度为76.89%,底泥中总氮含量均衡度为57.04%;试验期内,水体中总氮质量浓度呈"凹"形变化、底泥中总氮含量呈"凸"形变化,二者表现出相逆的变化趋势.

Distribution Characteristics of Solute Nitrogen in the Water-Sediment of Farmland Drainage Ditch

Along with the highlighted water environmental issues and the gradual effective renovation of the point source pollution (PSP) such as industrial waste, the agricultural non-point source pollution (AGNSP) caused by the non-scientific application of fertilizers and pesticides has attracted more and more attention. On the basis of strengthening the field "source control", making the best use of agricultural drainage ditch (pond) system "intercepting process" is a vital means of agriculture non-point source pollution control and management at the present stage. Ditch system is not only an important part of the farmland irrigation and drainage engineering, but also a vital corridor of AGNSP of solute transport. The unique farmland drainage ditch water-sediment-plant system in ecology and physics is similar to linear wetland function,and has effect of interception and purification on non-point source solute in farmland drainage. Non-point source solute transformation mechanism of each medium in the farmland drainage ditch water-sediment-plant system is unclear, in view of the current situation, the study took the natural channel as the object. Taking the non-point source solute nitrogen as an example, by field monitoring test during March 2014-February 2015, the distribution characteristics of non-point solute nitrogen in the water-sediment of the farmland drainage ditch were analyzed. The results indicated that the concentration of total nitrogen in water and the total nitrogen content in the sediment of the experimental ditches both showed a certain degree of decreasing trend along the longitudinal ditch, which represented a purification effect of the ditch system on the non-point source solute. The concentration of total nitrogen in water and the total nitrogen content in the sediment had big inhomogeneity in the ditch cross-sectional distribution, and its distribution characteristics were related to the shape of the cross-section, flow variation process, flow velocity distribution and other factors. The balance of the total nitrogen concentration was 76.89%, and the total nitrogen content in the sediment was 57.04%. During the trial period, the total nitrogen concentration in the water was "concave" shape, while in the sediment it was "convex" shape, showing opposite changing trends.