农业面源污染中氮排放时空变化及其健康风险评价研究——以淮河流域为例

以保护淮河流域环境和居民健康为出发点,为揭示流域农业面源污染负荷时空分布特征,采用清单分析法和排污系数法核算了流域35个地级市的畜禽养殖、农村生活、农田种植3种污染源总氮(TN)的排放量和排放强度。利用GIS软件对氮素耕地、水体污染排放强度进行时空变化分析,分析出流域面源污染的重点污染源、污染类型及其空间分布特征,并根据健康风险评价模型估算流域内地下水中硝态氮对人体潜在的健康风险。结果表明:2015年淮河流域农村生活、化肥使用和畜禽粪便TN排放量分别为42.17万、644.44万t和213.86万t,排放比重分别为3.58%、72.39%和24.03%,化肥的施用仍是氮素污染的主要来源;耕地氮素污染负荷方面,农田种植畜禽养殖农村生活;地表水氮素污染负荷方面,农田种植≈畜禽养殖农村生活。流域内不同地区污染物负荷强度受耕地面积和水资源量的影响,分布存在一定区域空间分异现象,淮河流域西北部地区负荷强度高于东南部。地下水硝态氮健康风险指数在0.49~3.18之间,健康风险阈值超过"1"的城市数量占整个淮河流域的82.86%,应注意饮用水的安全问题。

Estimation of spatio-temporal variability and health risks of nitrogen emissions from agricultural non-point source pollution: A case study of the Huaihe River Basin, China

For the purposes of protecting the environment, human health of residents, and revealing the watershed agricultural non-point source pollution load distribution over time, this study adopts the inventory method and pollution discharge coefficient. It analyzes three kinds of pollution sources:livestock breeding, rural life and farmland cultivation, and contribution to total nitrogen(TN) emissions and emissions intensity in 35 cities of the Huaihe River Basin. The spatio-temporal variability of non-point pollution sources was presented based on geographic information system analysis. Furthermore, the potential health risks of nitrate/nitrogen in groundwater were estimated according to the health risk assessment model. The results showed that the TN emissions of rural life, farmland cultivation, and livestock breeding were 4.22×10⁵ t, 6.44×10⁶ t, and 2.14×10⁶ t, respectively, in the Huaihe River Basin in 2015. Rural life, farmland cultivation, and livestock breeding measured emissions were correspondingly 3.58%, 72.39%, and 24.03%. Fertilizer use was still the main source of nitrogen pollution. Farmland nitrogen pollution due to field fertilization was the greatest, but livestock and poultry farming also showed greater contributions than that of rural life. Farm field planting mainly contributed to surface water nitrogen pollution loads, but other sources contributed significantly to total loading rates and present significant regional spatial variability. The northwest area of the Huaihe River Basin showed higher nitrogen loading than the southeast. In terms of groundwater, nitrate health risk indexes ranged from 0.49 to 3.18, exceeding the health risk threshold "1", which accounts for 82.86% of the entire Huaihe River Basin. We proposed that it was necessary to pay more attention to the safety of drinking water.