Seasonal and Spatial Variability of Dissolved Carbon Concentration and Composition in Lake Michigan Tributaries
Seasonal and Spatial Variability of Dissolved Carbon Concentration and Composition in Lake Michigan Tributaries
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DOI：
10.1029/2021jg006449
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发表时间：
2021-10
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影响因子：
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通讯作者：
Stephanie M. Berg;R. Mooney;Megan B. McConville;P. McIntyre;Christina K. Remucal
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文献类型：
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作者：
Stephanie M. Berg;R. Mooney;Megan B. McConville;P. McIntyre;Christina K. Remucal
溶解有机物（DOM）是许多化合物的复杂混合物，其组成决定了环境中的许多反应。大型湖泊和海洋海岸线从不同土地覆盖范围的流域接收DOM，这对碳输入的数量和组成都有潜在影响。不同支流间DOM数量和组成的季节变化也可能不同，并受土地覆盖的调节。在这里，我们使用天气抽样方法，量化了世界最大湖泊之一密歇根湖101条支流的DOM浓度、DOM组成（基于紫外-可见光谱）和碱度的空间（即各支流之间）和季节变化。湿地覆盖对DOM的影响最大，产生的DOM浓度较高，芳香性更强，表观分子量更大。季节变化也很明显，大多数支流的DOM浓度和芳香性在秋季达到峰值。流域岩性和土地覆盖对碱度均有影响，且与碳酸盐基岩和城市化流域地理有关。流域土地覆被对各有机碳参数的影响大于季节。然而，季节变化对DOM的组成尤其重要。这种差异表明，河道内DOM的环境处理对其组成的调节作用大于其浓度。考虑到密歇根湖和其他大型水体周围广泛的土地覆盖和岩性，考虑空间和季节动态对于理解DOM释放的控制至关重要。
Dissolved organic matter (DOM) is a complex mixture of many compounds and its composition dictates numerous reactions in the environment. Large lakes and marine coastlines receive DOM from watersheds that differ widely in their land cover, with potential implications for both the quantity and composition of carbon inputs. Seasonal variation in DOM quantity and composition may also differ among tributaries and be mediated by land cover. Here, we quantify spatially (i.e., among tributary) and seasonal variation in DOM concentration, DOM composition based on ultraviolet‐visible spectroscopy, and alkalinity across 101 tributaries of Lake Michigan, one of the world's largest lakes, using a synoptic sampling approach. Wetland land cover has the largest effect on DOM, producing high concentrations of DOM that are more aromatic and larger in apparent molecular weight. Seasonal variation is also pronounced, with concentrations and aromaticity of DOM peaking in fall across most tributaries. Watershed lithology and land cover both affect alkalinity, with higher values associated with the geography of carbonate bedrock and urbanized watersheds. Watershed land cover has a larger effect than season on all organic carbon parameters. However, seasonal variation is especially important for DOM composition. This disparity suggests that the environmental processing of DOM within river channels mediates its composition more than its concentrations. Considering the wide range of land cover and lithology around Lake Michigan and other large water bodies, accounting for both spatial and seasonal dynamics is essential for understanding controls on DOM delivery.