Sources of and processes controlling CO2 emissions change with the size of streams and rivers
Sources of and processes controlling CO2 emissions change with the size of streams and rivers
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DOI：
10.1038/ngeo2507
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发表时间：
2015-09-01
影响因子：
18.3
通讯作者：
Karlsson, J.
中科院分区：
文献类型：
--
作者：
Hotchkiss, E. R.;Hall, R. O., Jr.;Karlsson, J.
二氧化碳（CO2）从溪流和河流逃逸到大气中代表了全球碳循环中的一个重要通量（1-3）。溪流和河流排放的CO2中，陆地来源的CO2或淡水生态系统通过水生代谢产生的CO2所占的比例尚未得到很好的量化。在这里，我们估计二氧化碳排放量从运行沃茨在美国本土，淡水的化学和物理特性和模拟的气体传输速度在1463美国地质调查局监测站点的基础上。然后，我们评估了水生代谢产生的二氧化碳，从以前发表的测量净生态系统生产的187个溪流和河流横跨美国本土。我们发现，水代谢产生的CO2约占流量在0.0001和19，000 m（3）s（-1）之间的溪流和河流的CO2排放量的28%。我们数学模拟CO2通量从地下水到运行沃茨沿着河流-河流连续体，以评估流大小和CO2源之间的关系。陆源CO2占小溪流排放量的主导地位，水生代谢产生的CO2排放量的百分比随着溪流的大小而增加。我们认为，河流作为陆地CO2排放的管道和矿化陆地有机碳的反应器的相对作用是其大小和与景观的连通性的函数。
Carbon dioxide (CO2) evasion from streams and rivers to the atmosphere represents a substantial flux in the global carbon cycle(1-3). The proportions of CO2 emitted from streams and rivers that come from terrestrially derived CO2 or from CO2 produced within freshwater ecosystems through aquatic metabolism are not well quantified. Here we estimated CO2 emissions from running waters in the contiguous United States, based on freshwater chemical and physical characteristics and modelled gas transfer velocities at 1463 United States Geological Survey monitoring sites. We then assessed CO2 production from aquatic metabolism, compiled from previously published measurements of net ecosystem production from 187 streams and rivers across the contiguous United States. We find that CO2 produced by aquatic metabolism contributes about 28% of CO2 evasion from streams and rivers with flows between 0.0001 and 19,000 m(3) s(-1). We mathematically modelled CO2 flux from groundwater into running waters along a stream-river continuum to evaluate the relationship between stream size and CO2 source. Terrestrially derived CO2 dominates emissions from small streams, and the percentage of CO2 emissions from aquatic metabolism increases with stream size. We suggest that the relative role of rivers as conduits for terrestrial CO2 efflux and as reactors mineralizing terrestrial organic carbon is a function of their size and connectivity with landscapes.