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An assessment of agricultural non-noint source pollution in Ningxia irrigation region, Northwest China.

ZHANG Ai-ping**   

  1. (Institute of Environment and Sustainable Development in Agriculture, Chinese Academy of Agricultural Sciences, Beijing 100081, China)
  • Online:2013-01-10 Published:2013-01-10

Abstract: In order to clarify the agricultural non-point source pollution in Yellow River irrigation region of Ningxia and to take relevant reasonable pollution prevention measures, an improved export coefficient method was used to estimate the agricultural nitrogen and phosphorus pollution loads in the region. Meanwhile, the equal standard pollution load and the effluent load ratio were adopted to evaluate the agricultural non-point source pollution in the irrigation region from the aspects of total pollution load and pollution structural features. According to the pollution load of total nitrogen, the irrigation region could be divided into three areas, i.e., Litong District of Wuzhong City with a pollution load over 2500 t, Pingluo County, Helan County, Yinchuan City, Yongning County, Qingtongxia City, Zhongning County, and Zhongwei City with a pollution load of 1500-2500 t, and Shizuishan City and Lingwu City with a pollution load below 1500 t. According to the pollution load of total phosphorous, the irrigation region could be classified into three areas, i.e., Zhongwei City and Zhongning County with a pollution load over 130 t, Pingluo County, Helan County, Yinchuan City, Yongning County, Qingtongxia City, Litong District of Wuzhong City, and Lingwu City with a pollution load of 70-130 t, and Shizuishan City with a pollution load below 70 t. Based on the structural features of pollution, the irrigation region could be categorized into three types. Types I and Ⅱ were of comprehensive pollution, whereas type Ⅲ was of single pollution. Type I was mainly in central Zhongwei City, in which, crop farming, livestock, and residential pollution took up a certain proportion of pollution load, and had similar pollution structure. Type Ⅱ included Yinchuan City, Yongning County, Helan County, Lingwu City, Shizuishan City, Qingtongxia City, and Zhongning County, in which, the pollution was mainly caused by livestock and less caused by residents. Type Ⅲ mainly included Pingluo County and Litong County, with the pollution load of crop farming in Pingluo County occupied 52% and that of livestock in Litong County reached 58%.