基于农业面源污染的三峡库区重庆段水质时空格局演变特征

农业面源污染已成为我国河流污染的主要来源。三峡库区是典型的生态脆弱区,水资源安全已越来越受到关注。以三峡库区重庆段21个区县为实例,在区县级尺度上,研究了2005—2011年农业面源污染化学需氧量(COD)、生化需氧量(BOD5)、全氮(TN)、全磷(TP)所导致的水质的变化。并借助地统计学中的空间插值方法,对30个水质监测站点的数据进行插值分析,最后利用内梅罗综合水质指数,通过核算和实测的数据来研究三峡库区重庆段水质的时空变化。结果表明:1)从库区平均水质浓度分析得出,2005、2008、2011年3个时间断面的TN、TP的浓度已经超过地表水环境质量三级标准。2)从核算数据所反映的水质综合指数的时空特征来看,2005、2008、2011年水质综合指数分别为2.48、2.51、2.88,均处于中度污染状态,而2011年甚至逼近严重污染状态。在空间分布上,三峡库区重庆段库中和库区腹地的区县整体的水质状况在下降,而位于库尾的核心都市区水质状况则有所提升。3)从监测数据所反映的水质综合指数的时空特征来看,2005、2008、2011年水质综合指数分别为1.26、1.38、2.14,2005和2008年属于轻污染状态,而2011年则为中度污染状态。在空间分布上,和核算数据的空间分布呈现出相似的地方。4)通过河流水体断面的监测数据与理论核算数据的对比看出,两者呈现出较好的吻合度。

Spatial and Temporal Variations of Water Resource Security Level in the Three Gorges Reservoir Area of Chongqing Based on Agricultural Non-Point Source Pollutant

Agricultural non-point source pollution (NPSP) is becoming an increasingly important eco-environmental problem, and it has become the major source of river basin pollution in China. It is difficult to control due to its dispersive and extensive characteristics. The Three Gorges Reservoir area is typical frangible ecotope. Therefore, water resource security is especially important. According to the investigation on the pollution sources of chemical fertilizer, organic manure, Crops straw, breeding, agriculture, dormitory sewage, dormitory wastes and soil erosion in the Three Gorges Reservoir Area (TGRA) of Chongqing, the Nemerow index was adopted to analyze the river basin water resource security level over the period 2005-2011. Spatial and temporal variations of water resource security level was analyzed by using geostatistical methods and Nemerow index based on theoretical data and monitoring data at the districts (counties) level. There were four major findings from the study. 1) From the judging the amount of water quality concentration in 2005, 2008 and 2011 in the TGRA of Chongqing, the concentration of TN, TP had exceeded the Surface Water Quality Standards III. 2) The results showed that the Nemerow index of theoretical data were 2.48, 2.51 and 2.88 in 2005, 2008 and 2011. Judging from the results of the spatial and temporal variations analysis of Nemerow index(theoretical data), with the completion of the reservoir water, the water resource security level of the hinterland and central of the TGRA (Chongqing section) has declined, whereas the metropolis’ core district of the end of the TGRA (Chongqing section) has improved. 3) The Nemerow index of monitoring data were 1.26, 1.38 and 2.14 in 2005, 2008 and 2011. The results of theoretical data and monitoring data showed that there was similarity in the spatial distribution. 4) The high coincidence was showed by comparing of the monitoring data and theoretical data in the TGRA of Chongqing.