The influence of climate on average nitrogen export from large watersheds in the Northeastern United States
The influence of climate on average nitrogen export from large watersheds in the Northeastern United States
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DOI：
10.1007/s10533-006-9010-1
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发表时间：
2006-05-01
期刊：
影响因子：
4
通讯作者：
Goodale, C.
中科院分区：
文献类型：
--
作者：
Howarth, R. W.;Swaney, D. P.;Goodale, C.
北美和欧洲大河流中的氮通量可以很好地解释为景观中人为氮净输入的函数，平均20%至25%的这些输入在河流中输出，75%至80%的氮在景观中保留或反硝化。在这里，我们使用美国东北部 16 个主要流域 6 年期间（1988-1993 年）的平均河流氮通量和人为氮输入数据来研究气候是否对河流中的氮通量产生影响。先前的研究表明，对于任何给定的河流，氮通量在流量较高的年份更大，但这可以解释为在干旱年份景观中氮的储存和在潮湿年份这些储存的氮的涌出。我们的分析表明，气候对河流氮通量也有长期稳态影响。那些降水量和排放量较高的流域输出的氮的人为净输入的比例更大。在美国东北部较干燥的流域，该比例出口占氮输入量的 10% 至 15%，在较湿润的流域，占氮输入量的 35% 以上。我们认为，这是由于较湿润的流域反硝化率较低所致，也许是因为较短的水停留时间不允许河岸湿地和低阶溪流中进行尽可能多的反硝化。通过对未来气候变化对降水和排放影响的平均预测，我们估计，由于随着降水和排放的增加，人为净氮输入的比例增加，到 2030 年，萨斯奎哈纳河到切萨皮克湾的氮通量可能会增加 3% 至 17%，到 2095 年将增加 16% 至 65%。尽管这些预测具有很大的不确定性，但它们表明需要更好地考虑气候对河流氮通量的影响，作为控制沿海氮污染的管理工作的一部分。
The flux of nitrogen in large rivers in North America and Europe is well explained as a function of the net anthropogenic inputs of nitrogen to the landscape, with on average 20 to 25% of these inputs exported in rivers and 75 to 80% of the nitrogen retained or denitrified in the landscape. Here, we use data for average riverine nitrogen fluxes and anthropogenic inputs of nitrogen over a 6-year period (1988-1993) for 16 major watersheds in the northeastern United States to examine if there is also a climatic influence on nitrogen fluxes in rivers. Previous studies have shown that for any given river, nitrogen fluxes are greater in years with higher discharge, but this can be interpreted as storage of nitrogen in the landscape during dry years and.ushing of this stored nitrogen during wet years. Our analyses demonstrate that there is also a longer-term steady-state influence of climate on riverine nitrogen fluxes. Those watersheds that have higher precipitation and higher discharge export a greater fraction of the net anthropogenic inputs of nitrogen. This fractional export ranges from 10 to 15% of the nitrogen inputs in drier watersheds in the northeastern United States to over 35% in the wetter watersheds. We believe this is driven by lower rates of denitrification in the wetter watersheds, perhaps because shorter water residence times do not allow for as much denitrification in riparian wetlands and low-order streams. Using mean projections for the consequences of future climate change on precipitation and discharge, we estimate that nitrogen fluxes in the Susquehanna River to Chesapeake Bay may increase by 3 to 17% by 2030 and by 16 to 65% by 2095 due to greater fractional delivery of net anthropogenic nitrogen inputs as precipitation and discharge increase. Although these projections are highly uncertain, they suggest a need to better consider the influence of climate on riverine nitrogen fluxes as part of management efforts to control coastal nitrogen pollution.