山地农业小流域非点源氮磷输出特征及来源

目的]分析非点源污染物输出特征及来源,为相似农业小流域水质研究以及非点源污染控制提供参照基础。方法]通过ArcGIS软件对集水流域划分,监测2014年断面及降雨水质,结合平均浓度法及输出系数法,建立考虑降雨携带输出的流域非点源负荷输出系数法计算模型,并进一步采用最优化数学方法对流域内污染物的来源进行分析。结果]核算得到耕地、林地、城镇村及工矿用地、农村生活和畜禽养殖的总氮输出系数分别为15.87,6.33,6.27kg/(hm~2·a),0.20kg/(人·a),0.83kg/(头·a),总磷输出系数分别为0.46,0.39,0.67kg/(hm~2·a),0.10kg/(人·a),0.16kg/(头·a)。该研究区域径流中NO_3~--N是氮流失的主要形式,降雨高峰期径流中颗粒态磷流失严重,NH_4~+-N及溶解态磷是该流域雨水中氮磷的主要存在形态。结论]该流域非点源污染输出以降雨、林地、农村生活输出为主。

Export Characteristics and Source Analysis of Non-point Source Nitrogen and Phosphorus in Mountain Agricultural Small Catchment

Objective] To analyze the export characteristics and source of non-point source in order to provide reference basis for the study of the similar agricultural watershed water quality and non-point source pollution control.Methods] This area was firstly divided into certain catchments with ArcGIS software. The water quality and precipitation was monitored across sections in 2014. Combined with the mean concentration method and export coefficient model, a calculation model was set up to estimate non-point source pollution export, and the sources for various non-point pollutants was analyzed with optimized mathematic method.Results] The total nitrogen export coefficients of agricultural land, woodland, residential land, domestics and livestock was 15.87 kg/(hm²·a), 6.33 kg/(hm²·a), 6.27 kg/(hm²·a), 0.20 kg/(person·a), 0.83 kg/(anamal·a), respectively, while the total phosphorus export coefficients was 0.46 kg/(hm²·a), 0.39 kg/(hm²·a), 0.67 kg/(hm²·a), 0.10 kg/(person·a), 0.16 kg/(anamal·a), respectively. Nitrate nitrogen was the main form of nitrogen loss in the runoff and a large amount of particulate phosphorus run off in the periods of peak rainfall. In the precipitation, ammonia nitrogen and dissolved phosphorus was main loss form.Conclusion] In this small catchment, precipitation, woodland and domestic waste are the main pollution sources.