流域尺度氮流失的环境风险评价

采用故障树及概率分析方法,对九龙江流域氮的流失风险进行定性与定量评价.通过建立故障树定性分析了九龙江流域氮流失的主要风险来源.结果表明,氮流失风险大小主要与肥料施用、畜禽养殖废物的处置及农田耕作有关.在GIS技术支持下,通过土地利用、土壤等数据的计算,结合田间调查结果与专家意见,确定故障树基本故障事件概率,继而对氮流失风险进行定量评价.最佳管理措施模拟评价结果表明,降低施肥水平,在养殖场周边建立植被过滤带,增加河岸林截留入河沉积物等措施可以有效降低氮流失风险,在九龙江流域可以考虑优先实施. 

Watershed Level Risk Assessment of Nitrogen Discharge Using Probabilistic Risk Assessment Tools

Probabilistic risk assessment(PRA) for the discharge of excess nitrogen was conducted for Jiulong River watershed,an agricultural watershed in Southeast China.Using fault tree analysis,the probability of occurrence for excessive nitrogen discharge to the river during a runoff event was qualitatively evaluated.It was showed that the risk of excess nitrogen discharge was mainly related to crop and livestock practices in the watershed.Under the support of GIS,land use,soil type,management practices and expert opinions were used to determine probabilities of individual events within the fault tree and to calculate the overall probability of excess nitrogen discharge during a runoff event.The results of simulation and assessment of optimal management measurements indicated that alternative practices,such as reducing fertilization,installing vegetative strip buffer around the pig farms,and installing more riparian buffers,have a greater potential of reducing the risk of excess nitrogen discharge during a runoff event and can be implemented in priority in Jiulong River watershed.