基于LUCC的南四湖流域面源污染输出风险评估

基于1990-2015年土地利用和统计数据,运用输出风险模型、CA-Markov模型及回归模型,结合GIS技术,对南四湖流域的1990-2015年间土地利用覆盖变化情况和面源污染输出风险空间变化情况进行分析,模拟了2020年土地利用变化和输出风险空间分布。结果表明：研究期间,南四湖流域主要的土地利用类型为耕地和建设用地,共占总研究面积的85%以上;TN、TP有明显的风险变化对比,TN风险值分布在0~0.65,TP风险值约在0~0.12之间,氮为流域内主要污染物;在1990-2005年间,TN风险呈先增加后减少的趋势,2010年之后急剧增大。TP风险随着时间的增加一直下降;从空间分布上来看,风险较高的污染区多位于南四湖区以西的平原地带,南四湖东部的山地地区污染风险型较低,多为低风险污染区。较2015年,2020年的未利用地面积变化不大,除建设用地数量增加外,其他用地面积均有不同幅度的减少,TN风险略有减小,TP风险变化不大。为了控制研究区域面源污染的发展,相关部门需把提高农业科技、减少肥料施用作为当下的工作重心,从源头上控制污染发生。

Risk assessment of non-point source pollution output in Nansihu Lake Basin based on LUCC

The land cover change and the non-point source pollution output risk in Nansihu Lake Basin during 1990-2015 were analyzed based on the land use data and statistical data. The method of output risk model, CA-Markov model and Regression Model were used, and combined with GIS technology, the land use pattern and the export risk distribution in 2020 were simulated. The results were as follows. In the 25 years, farmland and arable land were the main land use types in the study area, accounting for more than 85% of the total area. The TN and the TP risk changes were significantly different. The TN output risk value ranged between 0-0.65, and the TP output risk value was 0-0.12. N was the main pollutant. The TN risk increased gradually from 1990 to 2005, decreased significantly during 2005-2005, and increased sharply during 2010-2015. The TP risk decreased gradually during the 25 years. The low risk areas were mainly distributed in the eastern part of Nansihu Lake basin, while the high risk areas were mainly in the west part of the lake basin. The land use change in 2020 was predicted. Compared with 2015, the arable land is increasing, the area of unused land is unchanged, and the other types are reducing to different degrees. The TN risk is reducing slightly. TP risk is unchanged. It is necessary for the local government to focus on improving the agricultural science and technology and reducing fertilizer use so as to control the status quo of non-point source pollution in Nansihu Lake Basin.