Chesapeake legacies: the importance of legacy nitrogen to improving Chesapeake Bay water quality
Chesapeake legacies: the importance of legacy nitrogen to improving Chesapeake Bay water quality
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DOI：
10.1088/1748-9326/ac0d7b
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发表时间：
2021-08-01
影响因子：
6.7
通讯作者：
Van Meter, K. J.
中科院分区：
文献类型：
--
作者：
Chang, S. Y.;Zhang, Q.;Van Meter, K. J.
在切萨皮克湾，几十年来，来自景观和大气来源的过量氮（N）助长了藻类生长，破坏了水生生态系统，并对沿海经济产生了负面影响。自20世纪80年代以来，切萨皮克湾计划的合作伙伴一直致力于在整个地区实施广泛的措施，从废水处理厂的升级到农场级最佳管理实践的实施，以减少氮通量到海湾。尽管这些措施得到了广泛实施，氮素投入也显著减少，但整个地区的水质改善缓慢。这种缺乏反应，在某些情况下，已被归因于氮的遗产-剩余的氮在土壤和地下水中的积累-这可能有助于保护措施的实施和改善水质之间的时间滞后。在这里，我们使用ELEMeNT-N建模框架来探索遗留氮在减缓氮负荷减少到海湾中的作用，并提供在九个主要支流流域达到水质目标所需的时间估计。我们的研究结果首先表明，最近水质的改善可以归因于20世纪70年代和80年代开始出现的N盈余幅度的减少，这种改善将在未来几十年继续下去。未来的模拟表明，即使在目前的管理实践中没有额外的变化，在未来20年内，该地区减少25%的氮负荷的目标几乎可以实现。目前的研究结果还表明，时间滞后，以实现水质可能会有很大的不同，在个别研究流域，最长的滞后时间被发现在高度农业Choptank流域，N盈余幅度仍然很高，遗留N仍然是一个主要的控制水质。
In the Chesapeake Bay, excess nitrogen (N) from both landscape and atmospheric sources has for decades fueled algal growth, disrupted aquatic ecosystems, and negatively impacted coastal economies. Since the 1980s, Chesapeake Bay Program partners have worked to implement a wide range of measures across the region-from the upgrading of wastewater treatment plants to implementation of farm-level best management practices-to reduce N fluxes to the Bay. Despite widespread implementation of such measures and notable reductions in N inputs, water quality across the region has been slow to improve. Such lack of response has in some cases been attributed to N legacies-accumulations of surplus N in soils and groundwater-that can contribute to time lags between implementation of conservation measures and improvements in water quality. Here, we use the ELEMeNT-N modeling framework to explore the role of legacy N in slowing reductions in N loading to the Bay, and to provide estimates of the time required to meet water quality goals in nine major tributary watersheds. Our results first show that recent improvements in water quality can be attributed to decreases in N surplus magnitudes that began to occur in the 1970s and 1980s, and that such improvements will continue in the coming decades. Future simulations suggest that, even with no additional changes in current management practices, goals to reduce N loads across the region by 25% can nearly be met within the next two decades. The present results also suggest that time lags to achieving water quality may vary considerably in the individual study watersheds, with the longest lag times being found in the highly agricultural Choptank watershed, where N surplus magnitudes remain high and where legacy N remains a major control on water quality.