宁夏引黄灌区农业非点源污染评价

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

为了明确宁夏引黄灌区农业非点源污染情况,有针对性地采取合理的污染防治措施,本研究利用改进的输出系数法对宁夏灌区农业氮、磷污染负荷进行了估算。同时,采用等标污染负荷法和污染负荷比从污染负荷总量和污染结构特点两个方面对宁夏灌区所辖市区农业非点源污染情况进行分析。结果表明:从污染负荷总量方面,根据TN污染负荷分布情况,可将宁夏灌区分为3个区域;Ⅰ区,TN污染负荷总量>2500t.a-1,主要分布在吴忠市利通区;Ⅱ区,污染负荷总量在1500～2500t.a-1,包括平罗县、贺兰县、银川市区、永宁县、青铜峡市、中宁县和中卫市;Ⅲ区,TN污染负荷总量<1500t.a-1,包括石嘴山市和灵武市;按照TP污染负荷;Ⅰ区,TP负荷>130t.a-1,主要包括中卫市和中宁县;Ⅱ区,TP负荷在70～130t.a-1,包括平罗县、贺兰县、银川市区、永宁县、青铜峡市、吴忠市利通区和灵武市;Ⅲ区,TP负荷在70t.a-1以下,主要分布在石嘴山市;根据灌区各地区污染结构特点,可将灌区污染分为3种类型;综合污染Ⅰ型,主要包括中卫城区,该区域呈现农田种植、畜禽养殖和生活污染各占一定比例,影响程度相近的污染结构;综合污染Ⅱ型,主要包括银川市区、永宁县、贺兰县、灵武市、石嘴山市、青铜峡市和中宁县等7个区县;这些区县以种养殖业污染为主,生活污染影响较小;单一污染型,主要包括平罗县和利通区2个区县,平罗县农田种植污染负荷比达到52%,农田种植是其最主要污染源;利通区畜禽养殖污染负荷比达到58%,畜禽养殖是其最主要污染源。

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, Qil：lgtongxia 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 couldbe categorized into three types. Types I and Ⅱwere of comprehensive pollution, whereas type m 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 Ⅱincluded 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 m 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%.