中文摘要：

乐安江是影响鄱阳湖水质的一条重要河流,近年来非点源污染迅速增加,水质呈下降趋势。运用GIS手段建立了研究区非点源污染的基本空间信息库,在野外水样监测和土地利用调查的基础上,分析了乐安江流域非点源氮的时空变化特征。氮的流失主要以可溶态形式,TN和DTN全年变化剧烈,在12月份普遍较高,4月份次之,9月份最低。在监测各月份乐安江流域TN浓度的范围为0.09~1.359 mg/L,水质属中营养水平。NO-3-N浓度平均值为DTN的65%,是DTN流失的主要形态,其时空分布与TN具有明显的相似性;在丰水期4月份,NH3-N的平均浓度为全年最低水平,平水期9月份NH3-N平均浓度为三氮之首;NO-2-N全年含量最低。各种形态的氮浓度在空间上从上游向下游基本呈增加趋势;西南部地区各种形态的氮浓度普遍高于东北部地区,说明上游水质普遍好于下游水质。

英文摘要：

The rapid increase of non-point source pollution has made water quality of Le′an River decline in recent years.Water samples were taken in April,September and December 2009,and land use investigation was carried out in Le′an River watershed for non-point source nitrogen pollution study.Using GIS as a tool,spatial information was analyzed to demonstrate the temporal and spatial characteristics of non-point source nitrogen pollution of the study area.Results indicated that loss of nitrogen was mainly via the soluble form.TN and DTN changed rapidly throughout the year.Generally,they were highest in December,followed in April,and lowest in September.The range of TN concentration was 0.09~1.359mg/L,indicating that Le′an River was reaching to medium-eutrophication situation.The average concentration of NO-3-N was 65% of DTN.NO-3-N was the major form of DTN loss and had similar spatial and temporal distribution with TN.The average concentration of NH3-N was the highest among the forms of nitrogen in September.NO-2-N concentration was the lowest throughout the year.The research area was divided into two districts according to the physiognomy and the terrain：the northeast low mountains and the southwest hilly area.Various forms of nitrogen concentration in southwestern part were generally higher than those in the northeastern,and the water quality of the upstream was generally better than the downstream.