三峡库区农业面源污染风险评估及治理清单

针对三峡库区农业面源污染风险评估指标体系不完善、个别指标计算时基础数据获取难度大的问题,该研究充分考虑农业面源污染产生、形成及调控全过程因素,构建了基于层次分析法的三峡库区面源污染风险评价指标体系,以更易获取的数据为基础参数、应用韦伯-费希纳定律克服个别风险指标过大的问题,给定了三峡库区面源污染风险评估指标计算方法,评估了三峡库区农业面源污染风险,并提出了三峡库区县域单元的纵向和横向污染治理清单。研究结果表明,三峡库区各县域农业面源污染总体处于中风险,库区内湖北省夷陵区、重庆市南岸区风险值最高,其次是重庆市大渡口区、沙坪坝区等市辖区、巫溪县以及湖北省兴山县和秭归区,之后是开州区、万州区、丰都县、云阳县等区域;化肥强度指数、畜禽养殖强度指数、降雨侵蚀指数、环保投资指数是三峡库区农业面源污染风险的主要影响指标;三峡库区各县域化肥强度指数以及畜禽养殖强度指数风险值之和占总压力指数风险值的比例平均为79%,巫溪县、巴东县、巫山县甚至达到90%;重庆市南岸区、大渡口区以及湖北省各县域化肥施用强度较高,建议开展茶果树施肥技术提升,畜禽养殖强度相对较大的区域主要集中在重庆市云阳县、开州区、巫溪县、巫山县以及湖北省各县区,建议更多开展猪和羊畜禽废污处理能力提升,此外还应加大环保投入以及合理调整种植结构;从纵向管控来看,三峡库区农业面源污染治理应以南岸区和夷陵区为优先管控区域,河流水质优先治理区域为大渡口区、九龙坡区以及湖北省的各县区,从横向管控来看,大部分县域的主要污染防控因素为化肥减量和畜禽养殖治理,其中三峡库区上游和下游地区应当更多关注化肥减量,中游则更多关注畜禽养殖的污染防控,该研究成果可为三峡库区农业面源污染政策制定提供有力参考。

Assessing risk and governing of agricultural non-point source pollution in Three Gorges Reservoir Areas

Non-point source pollution is required to consider the whole process factors of generation, formation, and regulation. In this study, the risk assessment system was constructed to evaluate the non-point source pollution in the Three Gorges Reservoir Area using an analytic hierarchy process. Taking the availability of data as an essential source, an operable index system was then proposed to overcome the excessive indicators of individual risk using Weber-Fechner. Finally, the horizontal and vertical lists of pollution control were determined for the decision-making. The result showed that agricultural non-point source pollution was predicted as the middle-risk level in the study area. The higher scores of risks were found in the Yiling District in Hubei Province and Nanan District in Chongqing Municipality. The next high-risk scores were distributed in Dadukou District, Shapingba District, Wuxi County in Chongqing Municipality and Xingshan County, Zigui County in Hubei Province, and the following were Kaizhou District, Wanzhou District, Fengdu County, and Yunyang County in Chongqing Municipality. The influencing indexes were obtained as fertilizer intensity, livestock/poultry breeding intensity, rainfall erosion, and environmental protection investment index in the risk system of agricultural non-point source pollution. The ratio between the risk scores of fertilizer intensity and livestock/poultry breeding intensity index accounted for 79% of the total risk scores of press indexes. By contrast, the ratios were more than 90% in Wuxi, Badong, and Wushan County. The average ratios of risk score were 32%, 25%, 24%, and 19%, respectively, for the stress, transformation, state, and governance index to the comprehensive one. Among them, the stress index still occupied the largest proportion of the risk score. Fertilizer intensity was higher in Nanan District, Dadukou District of Chongqing Municipality, and the counties in Hubei Province. Some suggestions were then proposed to improve the fertilization of fruit trees. The relatively high intensity of livestock and poultry breeding was concentrated mainly in Yunyang County, Kaizhou District, Wuxi County, Wushan County in Chongqing Municipality, and the counties in Hubei Province. Particularly, it was necessary to improve the waste treatment of pigs and sheep. In addition, the planting structure was required to adjust reasonably to increase the investment in environmental protection. In the vertical lists of pollution control, Yiling and Nanan District should be given priority to the agricultural non-point source pollution control, where the priority areas of river water quality control were Dadukou, Jiulongpo District, and the counties in Hubei Province. In the horizontal lists of pollution control, the pollution control factors in most counties were fertilizer reduction and livestock breeding control. More attention should be paid to fertilizer reduction in the upstream and downstream areas, while the pollution prevention and control caused by livestock and poultry breeding in the middle reaches. Furthermore, the slope length index of each county was evaluated, according to the average value of 0.026. Soil erodibility of each county was chosen from 0.015 to 0.019 ·hm²·h/(MJ·mm·hm²) for the better performance of risk assessment. This finding can provide a strong reference for the policy formulation of agricultural non-point source pollution in the Three Gorges reservoir area.