上海都市农业村域地表水非点源氮素的时空分异特征

为研究平原地区都市农业区域地表水非点源氮素的时空分异特征,揭示非点源氮污染对地表水环境的影响,连续监测了上海南汇新场镇果园村地表水中总氮和无机"三氮"(硝态氮、铵态氮和亚硝态氮)的含量.结果表明:①水文期和土地利用类型共同影响地表水中氮素的空间分布.受果园影响的地表水中硝态氮(NN)浓度较高,铵态氮(AN)浓度较低,各监测点氮素浓度在多雨期差异较大,在少雨期差异较小;受居民区和工厂影响的地表水中NN和AN浓度相差不大,各监测点氮素浓度在多雨期和少雨期差异都较大.②冬、夏季风风向可能影响果园村地表水中氮素的空间分布.③春雨期总氮(TN)、NN和AN的空间变异大,梅雨期和冬季少雨期略大于秋雨期和盛夏少雨期;亚硝态氮(SNN)与之相反.④5月溶解性有机氮(DON)是果园区地表水中氮素的主要存在形式,占TN的质量分数达到76.1%;其它季节则以溶解性无机氮(DIN)为主,占TN的质量分数平均达到83.2%.⑤果园区NN的季节变异比居民区大,居民区AN和TN的季节变异比果园区大.

Temporal and Spatial Variation of Non-Point Source Nitrogen in Surface Water in Urban Agricultural Region of Shanghai

To know the temporal and spatial variation characteristics of non-point source nitrogen in surface water in urban agricultural region, and reveal the effect of non-point source nitrogen pollution on the quality of surface water, the contents of total nitrogen and inorganic nitrogen species in surface water were continuously monitored in Orchard Village, Nanhui District, Shanghai. The results were obtained as follows: 1 Spatial distribution of nitrogen in surface water is affected by hydrological periods and land use type. Mass concentration of nitrate nitrogen (NN) is high and that of ammonium nitrogen (AN) is low in surface water affected by the orchard, and the discrepancy of nitrogen concentration is high in wet season and low in dry season. Mass concentrations of NN and AN in surface water affected by residential region and factories show little difference, and the discrepancy of nitrogen concentration is high both in wet season and in dry season. 2 Winter and summer monsoons may affect the spatial distribution of nitrogen in surface water in the studied area. 3 Spatial variation of total nitrogen (TN), NN and AN is the highest in spring rain period, and it is higher in plum rain period and winter brief rain period than that in autumn rain period and summer brief rain period. Nitrite nitrogen (SNN) shows contrary spatial variation. 4 Dissolved organic nitrogen (DON, mass fraction in TN is 76.1%) is the main species in surface water in orchard region in May, while the dissolved inorganic nitrogen (DIN, mass fraction in TN is 83.2%) in other months. 5 The temporal variation of NN in orchard region is higher than that in residential region, while that of AN and TN in residential region is higher than that in orchard region.