PDF(Pubmed)
Abstract：
The negative effects of nutrient pollution in streams, rivers, and downstream waterbodies remain widespread global problems. Understanding the cost-effectiveness of different strategies for mitigating nutrient pollution is critical to making informed decisions and defining expectations that best utilize limited resources, which is a research priority for the US Environmental Protection Agency. To this end, we modeled nutrient management practices including residue management, cover crops, filter strips, grassed waterways, constructed wetlands, and reducing fertilizer in the upper East Fork of the Little Miami River, an 892 km2 watershed in southwestern Ohio, United States. The watershed is 64% agriculture with 422 km2 of row crops contributing an estimated 71% of the system\'s nutrient load. The six practices were modeled to treat row crop area, and among them, constructed wetlands ranked highest for their low costs per kilogram of nutrient removed. To meet a 42% phosphorus (P) reduction target for row crops, the model results suggested that the runoff from 85.5% of the row crop area would need to be treated by the equivalent of 3.61 km2 of constructed wetlands at an estimated cost of US$2.4 million annually (or US$48.5 million over a 20-year life cycle). This prompted a series of projects designed to understand the feasibility (defined in terms of build, treatment, and cost potential) of retrofitting the system with the necessary extent of constructed wetlands. The practicalities of building this wetland coverage into the system, while leading to innovation in unit-level design, has highlighted the difficulty of achieving the nutrient reduction target with wetlands alone. Approximately US$1.2 million have been spent on constructing 0.032 km2 of wetlands thus far and a feasibility analysis suggests a cost of US$38 million for an additional 0.409 km2. However, the combined expenditures would only achieve an estimated 13% of the required treatment. The results highlight the potential effectiveness of innovative design strategies for nutrient reduction and the importance of considering realistic field-scale build opportunities, which include accounting for acceptance among landowners, in watershed-scale nutrient reduction simulations using constructed wetlands.
摘要：
溪流中营养污染的负面影响，河流,下游水体仍然是普遍存在的全球性问题。了解减轻养分污染的不同策略的成本效益对于做出明智的决策和定义最佳利用有限资源的期望至关重要。这是美国环境保护局的研究重点。为此,我们对营养素管理实践进行了建模，包括残留物管理，覆盖农作物，过滤条,草地水道，人工湿地,减少小迈阿密河上游东叉的肥料，俄亥俄州西南部892平方公里的分水岭，美国。分水岭是64％的农业，其中422km2的农作物贡献了该系统养分负荷的71％。这六种做法被建模为处理行作物面积，其中,人工湿地因其每公斤养分去除成本低而排名最高。为了实现农作物磷（P）减少42％的目标，模型结果表明，85.5％的行作物面积的径流需要用相当于3.61km2的人工湿地进行处理，估计每年的成本为240万美元（或20年生命周期内的4850万美元）。这促使一系列旨在理解可行性的项目(定义为构建，治疗,和成本潜力）用必要的人工湿地改造系统。将这种湿地覆盖纳入系统的实用性，在导致单元级设计创新的同时，强调了仅靠湿地实现养分减排目标的难度。到目前为止，大约有120万美元用于建造0.032平方公里的湿地，可行性分析表明，额外的0.409平方公里的成本为3800万美元。然而,综合支出估计只能达到所需治疗的13%。结果突出了减少养分的创新设计策略的潜在有效性，以及考虑现实的现场规模构建机会的重要性。其中包括土地所有者之间的接受会计，在使用人工湿地的流域尺度养分减少模拟中。
