三峡库区重庆段农村面源污染时空格局演变特征

论文以三峡库区重庆段21 个区县为实例,利用空间自相关及冷热点分析方法,在区县级尺度上,研究了化学肥料施用、有机肥施用、农作物秸秆、畜禽养殖、水产养殖、农村生活污水、生活垃圾和农田土壤侵蚀等8 个来源中农业面源污染化学需氧量(COD)、生化需氧量(BOD5)、全氮(TN)、全磷(TP)的时空变化特征,结果表明:① 从Moran's I 值判断,2005-2011年间,三峡库区重庆段的COD、BOD5、TN、TP在区域上一直处于较高的集聚状态,2005-2008年集聚减弱,2008-2011 年集聚增强。② 从COD、BOD5、TN、TP排放总量来看,由农业面源污染引起的COD、BOD5、TN、TP 绝对排放量,2005 年分别为15.85×10⁴、7.35×10⁴、5.50×10⁴ 和0.97×10⁴ t·a^-1;2008 年分别为10.93×10⁴、6.45×10⁴、5.60×10⁴ 和1.04×10⁴ t·a^-1;2011 年分别为14.67×10⁴、8.68×10⁴、6.94×10⁴和1.14×10⁴ t·a^-1。COD、BOD5 绝对排放总量经历了先降后升的趋势,TN和TP绝对排放总量则一直处于增长的态势。③ 从冷热点分析结果来看,三峡库区腹地是热点区域的集中区,而三峡库区库尾都市核心区是冷点区域集中区。

Spatial and Temporal Variations of Agricultural Non-point Source Pollution in the Three Gorges Reservoir Area of Chongqing

According to the investigation on the pollution sources of chemical fertilizer, organic manure, Crops straw, breeding, aquiculture, dormitory sewage, dormitory wastes and soil erosion in the Three Gorges Reservoir Area (TGRA) of Chongqing, the spatial and temporal features of agricultural non-point source pollution (NPSP) were analyzed with the ArcGIS software. Spatial and temporal variations of the absolute discharge amount of NPSP in the TGRA of Chongqing were analyzed at the districts (counties) level using the spatial cluster and hot and cold spots analysis methods. There were three major findings from the study: 1) Moran' s I Index values remained high from 2005 to 2011 (although with a downward trend in 2008). 2) The results showed that the absolute discharge amounts of COD, BOD5, TN and TP from NPSP were 158.5, 73.5, 55.0 and 9.7 thousand ton per year in 2005. The absolute discharge amounts of COD, BOD5, TN and TP from NPSP were 109.3, 64.5, 56.0 and 10.4 thousand ton per year in 2008. The absolute discharge amounts of COD, BOD5, TN and TP from NPSP were 146.7, 86.8, 69.4 and 11.4 thousand ton per year in 2011. The absolute discharge amount of COD, BOD5 experienced a trend of raise after a drop, but the absolute discharge amount of TN and TP always showed upward trend from 2005 to 2011.3) Judging from the results of the hot and cold spots analysis, the inner section of the TGRA of Chongqing was the hotspots, whereas the metropolis' core district at the end of the TGRA of Chongqing was the cold spots. The primary pollution districts (counties) were Yunyang, Wanzhou and Kaixian, which all locate in the inner section of the TRGA of Chongqing. The study provided the scientific basis for the evaluation of NPSP in Chongqing.