兴山县香溪河流域农业源氮磷排放估算及时空特征分析

Estimates and Spatio-Temporal Characteristics of Nitrogen and Phosphorus Discharges from Agricultural Sources in Xiangxi River Basin, Xingshan County

基于典型调查与统计分析,应用排污系数法估算了兴山县香溪河流域2007—2013年种植业源、畜禽养殖业源和农村生活源TN、TP污染物的排放量,并对排放量、排放强度及其时空格局进行了分析。结果表明,香溪河流域农业面源污染TN、TP年均排放量分别为1 145.2、56.5 t·a-1,排放强度分别为44.5、2.14 kg·hm-2·a-1。农业源TN和TP的年排放量逐年增加,2013年较2007年增幅分别为38.0%和85.1%,TN∶TP为21∶1,TN排放占主导,为香溪河流域兴山县段重点防控指标。从各类污染源贡献来看,畜禽养殖业源是TN的主要贡献源,占农业源污染总量的77.9%;种植业源是TP的主要贡献源,占55.4%。从不同源氮磷排放量空间格局来看,各乡镇中水月寺镇、黄粮镇和峡口镇的TN、TP排放量均最高。从氮磷排放强度空间格局来看,峡口镇、高桥乡和黄粮镇对TN排放强度最高;峡口镇、昭君镇和黄粮镇对TP排放强度最高。

Based on typical investigation and statistical analysis, the discharge loads of TN and TP from agricultural sources in the Xiangxi River basin, Xingshan County during 2007 to 2013 were estimated using pollutant discharge coefficient approach. The intensity and spatiotemporal pattern of three main types of agricultural non-point sources, rural domestic source, animal production and crop production, were also analyzed. The annual TN and TP discharges were 1 145.2 t·a-1and 56.5 t·a-1, and their discharge intensities were 44.5 kg·hm-2·a-1and2.14 kg·hm-2·a-1, respectively. The agricultural source percentage of TN and TP discharges respectively increased by 38.0% and 85.1%from 2007 to 2013. The ratio of mean annual TN/TP discharge was 21∶1, indicating that TN discharge was the main target of prevention and control in Xiangxi River basin. The animal production was the main source of TN discharges, accounting for 77.9% of TN discharges, while crop production was the main source of TP discharges, amounting to 55.4% of TP discharges. Shuiyuesi, Huangliang and Xiakou towns were the major sources of nitrogen and phosphorus discharges spatially. Xiakou, Gaoqiao and Huangliang towns had higher intensity of TN discharge among all the towns with Xiakou, Zhaojun and Huangliang towns being higher intensities of TP discharge.