摘要:系统评估农业化肥过量施用对生态环境的潜在风险危害，可为制定下一阶段农业面源污染防治工作提供决策参考。本文基于2000-2015年化肥施用量和耕地面积等数据，采用化肥施用环境风险评价模型，探讨了四川省化肥施用及环境风险的时空变化特征；通过设置延续现状和政策干预两种情景，模拟了四川省2016-2018年执行化肥施用零增长行动期间的化肥施用环境风险变化趋势。结果表明：四川省化肥施用总量在2000-2015年间整体呈增加态势，2015年四川省化肥施用强度为376.63 kg·hm-2，超过了中国生态市建设的化肥施用强度250 kg·hm-2的生态标准。四川省2015年化肥施用的环境总风险指数为0.69，处于中等风险程度；氮、磷、钾肥施用的环境风险指数分别为0.69、0.72和0.46。钾肥施用的环境风险处于安全状态；氮肥和磷肥的环境风险区域集中在成都平原经济区、川南经济区和川东北经济区，呈现中等风险程度并有成片聚集特征。延续现状情景下，四川各地区化肥施用环境总风险指数处于0.48~0.69，存在不同程度增加。与延续现状情景相比，四川在完成化肥施用零增长行动的任务规划前提下，2016-2018年政策干预情景的化肥施用环境总风险呈现下降趋势。以关键时间点2018年来看，川东北经济区化肥施用环境总风险下降最明显，较2015年执行化肥零增长时下降4.24%。但四川省多数地区仍存在不同程度的化肥施用环境污染风险，当地生态环境具有明显压力。建议省级部门加强对成都平原经济区和川东北经济区的化肥面源污染监测，根据各地区差异特征制定不同施肥方案，协调粮食增产和生态保护间的关系。
Abstract:Fertilizer-based pollution has been an important part of agricultural non-point source pollution. Systematic assessment of potential risks and hazards of excessive application of chemical fertilizers to the ecological environment can provide the data base for decision-making of the prevention and control of agricultural non-point source pollution. Sichuan Province is not only a predominant grain production base, but also a region with severe agricultural non-point source pollution in China. Due to excessive long-term fertilizer application, the agro-ecological environment in Sichuan Province has had tremendous pressure. Based on data on fertilizer application, grain sowing and cultivated land area, the spatio-temporal variations in environmental risk due to fertilizer application were evaluated. In the adoption of environmental risk model for fertilizer application in Sichuan Province during 2000-2015, many factors were considered. These included fertilization intensity, environmental safety threshold, fertilization efficiency, multiple cropping index and fertilizer effect on the environment. Using two scenarios (extension and policy intervention), the variation trend in environmental risk associated with fertilizer application under zero-growth chemical fertilizer was simulated for Sichuan for the 2016-2018. The results showed that the total amount of chemical fertilizers in Sichuan Province increased during 2000-2015. The intensity of chemical fertilizer application in Sichuan Province was 376.63 kg·hm-2 in 2015, exceeding the ecological standard set for China's ecological city (250 kg·hm-2). Based on the application structures of nitrogen, phosphorus and potassium fertilizers in 2015, the application of nitrogen fertilizer in Sichuan Province accounted for 57% of the total amount of chemical fertilizers. In Chengdu, Mianyang and Zigong, the proportion of nitrogen fertilizer application was the highest in the whole province. The proportions of phosphate and potash fertilizers were low, accounting respectively for 28% and 15%. This indicated that nitrogen fertilizer still played a dominant role in agricultural production in the region. In 2015, total environmental risk index due to fertilizer use in Sichuan Province was 0.69, which was a medium risk level. Specifically, the environmental risk indexes of nitrogen, phosphate and potash applications were respectively 0.69, 0.72 and 0.46. Only potassium fertilizer application had a safe level of environmental risk. The environmental risk areas of nitrogen and phosphate fertilizers were concentrated in the Chengdu Plain Economic Zone, Southern Sichuan Economic Zone and Northeast Sichuan Economic Zone. Under the extension scenario, the environmental risk index of fertilizer application in various regions of Sichuan Province was in the range of 0.48-0.69, showing an increasing trend. Compared with the extension scenario, environmental risk due to fertilizer use under the policy intervention scenario declined across 2016-2018. In 2018, the environmental risk index of fertilizer application decreased most significantly in Northeast Sichuan Economic Zone, which was 4.24% lower than that in 2015. However, in most areas of Sichuan Province, there were still different levels of excessive chemical fertilizer application. The risk of environmental pollution caused by chemical fertilizer application had obvious pressure on the local ecological environment. We suggested that monitoring non-point source pollution of fertilizers should be improved in Chengdu Plain Economic Zone and Northeast Sichuan Economic Zone. Fertilization plan for each area should take the focus so as to ensure coordination between food production and ecological protection.
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