太湖上游大溪水库流域营养盐输移时空特征分析

大溪水库位于太湖上游地区,是溧阳市的重要饮用水源地之一,近年来流域内湖（库）体水质有下降趋势。基于2008—2009年对入湖主要支流水质营养盐浓度监测数据,实地考察流域内的主要污染源以及耕作制度等因素,并以2009年航空遥感影像解译获得的土地利用数据为基础,结合季节气候变化以及农业活动等环境影响因子,分析流域内营养盐时空分异特征及原因,为改善和治理饮用水源地水质工作提供科学依据和保障。结果表明,大溪水库流域不同支流水质营养盐浓度空间差异显著,表现为临湖东岸的氮磷营养盐浓度普遍高于西岸及上游的洙漕河流域,是大溪水库流域氮磷营养盐主要的源;各流域的TN、DTN、NO3--N浓度逐月变化趋势基本一致,TP、DTP季节间浓度变化趋势不明显。进入大溪水库流域的氮素主要以可溶性氮素为主,TN平均浓度为1.82mg·L^-1;磷素主要以非溶解态磷素的形式输移,TP平均浓度为0.116mg·L^-1;总体水质属于Ⅳ水质。营养盐输移时空差异的原因与各小流域土地利用状况、农业活动及降雨季节变化关系密切。

Analysis on Temporal and Spatial Characteristics of Nutrient Export in Daxi Reservoir Watershed in the Upstream of Taihu Lake Area,China

Water quality is gradually declining in recent years in Daxi reservoir,which is located at the upstream of Taihu Lake area,and it is one of the important drinking water sources in Liyang City. Nutrient export concentrations of main tributary were monitored in 2008—2009. Main pollution sources and farming system were investigated on the spot. Land use data were interpreted from 2009 aviation images. Combined with the season climate change,land use and land cover and agricultural activities within the watershed,the characteristics and reasons temporal and spatial distribution of nutrients export in Daxi reservoir watershed were analyzed. Results show,the spatial difference of nutrient concentration in different branches of Daxi watershed was significant,and the nutrient concentration in the east coast of the lake was generally higher than that in the west coast and Zhucao River watershed; the various forms of nutrient concentrations in different sub-watersheds almost had the similar change by month. The concentrations of TP and DTP had no significant difference among the four seasons. DTN was the main part of TN of Daxi reservoir watershed,the average concentration of TN was 1.82 mg·L^-1. P mainly was in the form of non-dissolved phosphorus,the average concentration of TP was 0.116 mg·L^-1; the overall water quality water quality were level Ⅳ. The reasons of spatial and temporal differences of nutrients were closely related to the situation of land use in the watershed,agricultural activities and seasonal variation of rainfall.