非点源污染输出对土地利用和社会经济变化响应的案例研究

为研究三峡库区(重庆段)自2006年10月蓄水(156m)以来,非点源污染输出对土地利用及社会经济背景变化响应的时空分异特征,综合考虑库区典型土地利用变化模式及社会经济背景,选取三峡库区腹地奉节县、忠县、库尾江津区及主城沙坪坝区为研究对象,使用动态输出系数模型法,以2007年、2010年和2013年3期遥感影像为数据源,分析了研究区2007年到2013年非点源污染TN、TP负荷量随土地利用类型改变及社会经济的发展而产生的时空变化特征。研究表明,6年间,研究区污染物TN从2007年的12126.9t上升到2013年的12692.3t,TP从2007年的394.6t上升到2013年的407.2t。就各典型区县而言,城市发展新区江津区非点源污染负荷呈上升趋势,TN、TP负荷量涨幅分别达到了28.6%和24.1%;而库尾城市快速扩展的沙坪坝区则呈现下降趋势,非点源污染TN、TP负荷量分别下降了48.8%和68.9%;仍保持传统农业的奉节县和忠县变化不大。

A study on the response of non-point source pollution to the variation of land use and social economy

The challenges associated with the ecological security and aquatic environment of the Three Gorges Reservoir Area are of domestic and international concern. This study aimed to examine the spatial variation characteristics of non-point source pollution output effected by changes in land use and the socio-economic background in the Chongqing section of this reservoir area, since the 156 m water level impoundment in 2006. The following four sites of the Three Gorges Reservoir Area were selected on the basis of typical land use variation model and socio-economic background:Fengjie and Zhongxian counties in the hinterland, Jiangjin district located at the end of the reservoir Area, and Shapingba district in the main urban area. The effects of land-use changes and the social-economic development between 2007 and 2013 on spatial variation of non-point source pollutants such as total nitrogen (TN) and total phosphorus (TP) were analyzed. The land-use types were analyzed using remote-sensing images of 2007, 2010, and 2013. The dynamic export coefficient model was used, and the output coefficient of farmland was amended by varying the amount of fertilizer applied. The results show that during the study period (2007-2013), the output of TN increased from 12126.6 t in 2007 to 12692.3 t in 2013, and the output of TP increased from 394.6 t in 2007 to 407.2t in 2013. Non-point source pollution in Jiangjin district continually increased, and the TN and TP output increased by 28.6% and 24.1%, respectively; the increase could be because of the increasing urbanization in this district. The non-point source pollution declined in Shapingba district over the study period, with rapid expansion of the city, and the TN and TP output decreased by 48.8% and 68.9%, respectively. However, non-point source pollution in Fengjiexian and Zhongxian counties showed little variation across the study period, which could be attributable to the maintenance of traditional agricultural practices. Collectively, these results suggest that different land-use types contribute differently to the total amount of non-point source pollutants:for example, farmland has the biggest impact on the TN and TP load, followed by woodland, grassland, construction land, and unused land.