Does Photomineralization of Dissolved Organics Matter in Temperate Rivers?
Does Photomineralization of Dissolved Organics Matter in Temperate Rivers?
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DOI：
10.1029/2021jg006402
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发表时间：
2021-07
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通讯作者：
T. Maavara;L. Logozzo;A. Stubbins;K. Aho;C. Brinkerhoff;J. Hosen;P. Raymond
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作者：
T. Maavara;L. Logozzo;A. Stubbins;K. Aho;C. Brinkerhoff;J. Hosen;P. Raymond
日光可将淡水中的溶解性有机碳（DOC）氧化为溶解性无机碳（DIC）。完整的光氧化，或光矿化，作为一个汇DOC的重要性仍然不清楚，在温带河流，因为大多数估计仅限于湖泊，高纬度河流，沿海河流羽流。在这项研究中，我们构建了一个模型，代表超过75,000条河流到达康涅狄格河流域（CRW），美国，计算光谱分辨光矿化。我们测试的假设，光矿化是一个可以忽略不计的DOC汇在所有达到和流动条件相对于DOC通量。我们的模型量化的反应速率和运输驱动程序内的河流达到的范围内的流动条件，传入的太阳辐照度，和冠层覆盖遮蔽全年观察。我们的模型预测的平均日面积光矿化率范围从1.16 mg-C m-2天-1在低流量的河流河段在冬季，到18.33 mg-C m-2天-1在高流量的河流河段在夏季。即使对于高的光矿化通量，相应的光矿化吸收速度通常至少比其他瞬时过程报道的小一个数量级。我们计算DOC的光矿化相对于DOC通量通过个别流达到以及整个河流部分的CRW消除。我们发现，相对光矿化通量是最高的夏季干旱条件下，在低位流。在中值流量和平均光照强度，平均流域的行程距离，3%-5%的DOC通量被淘汰，表明光矿化是一个小DOC汇在温带河流。
Sunlight can oxidize dissolved organic carbon (DOC) to dissolved inorganic carbon (DIC) in freshwaters. The importance of complete photooxidation, or photomineralization, as a sink for DOC remains unclear in temperate rivers, as most estimates are restricted to lakes, high latitude rivers, and coastal river plumes. In this study, we construct a model representing over 75,000 river reaches in the Connecticut River Watershed (CRW), USA, to calculate spectrally resolved photomineralization. We test the hypothesis that photomineralization is a negligible DOC sink across all reaches and flow conditions relative to DOC fluxes. Our model quantifies reaction rates and transport drivers within the river reaches for the ranges of flow conditions, incoming solar irradiance, and canopy cover shading observed throughout the year. Our model predicts average daily areal photomineralization rates ranging from 1.16 mg‐C m−2 day−1 in low flow river reaches in the winter, to 18.33 mg‐C m−2 day−1 in high flow river reaches during the summer. Even for high photomineralization fluxes, corresponding photomineralization uptake velocities are typically at least an order of magnitude smaller than those reported for other instream processes. We calculate DOC elimination by photomineralization relative to DOC fluxes through individual stream reaches as well as the entire riverine portion of the CRW. We find that relative photomineralization fluxes are highest in summer drought conditions in low order streams. In median flows and mean light intensities, for an average watershed travel distance, 3%–5% of the DOC fluxes are eliminated, indicating that photomineralization is a minor DOC sink in temperate rivers.