Synchronous evaporation and aquatic primary production in tropical river networks.
Synchronous evaporation and aquatic primary production in tropical river networks.
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DOI：
10.1016/j.watres.2021.117272
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发表时间：
2021-05
期刊：
影响因子：
12.8
通讯作者：
J. Zhong;M. Wallin;Wanfa Wang;Si‐Liang Li;Laodong Guo;K. Dong;R. Ellam;Cong-Qiang Liu;Sheng Xu
中科院分区：
文献类型：
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作者：
J. Zhong;M. Wallin;Wanfa Wang;Si‐Liang Li;Laodong Guo;K. Dong;R. Ellam;Cong-Qiang Liu;Sheng Xu
河流在全球水和碳循环中发挥着重要作用，但在蒸发和水生光合作用方面仍存在很大的不确定性。本文结合水化学、同位素组成（δ DW、δ 18 O W、δ 13 C DIC和δ 14 C DIC）和地理特征（河流宽度）的测量结果，阐明了海南岛河流的水文和地球化学过程。结果表明，河流沃茨中溶解无机碳（DIC）主要是现代来源的，约95%来自现代生物来源的同位素质量平衡的基础上的14 C DIC。在这些热带河流中，大量的水和DIC在水柱中迅速翻转，改变了水循环和碳平衡，同时发生了显著的蒸发和水生初级生产。高速率的蒸发和水生初级生产在源头段，狭窄的河流宽度，但广泛的可用反应表面积在空气-水界面。不同河段水体光合作用的不对称性导致了溶解性溶质的空间异质性。结果表明，在水-气界面的有效反应面积负责同步水分流失和溶解碳的演变在平坦的热带河流。这项研究提供的证据表明，强烈的蒸发和水生光合作用主要发生在源头段，这对理解全球碳循环具有重要意义。
Rivers play an important role in global water and carbon cycling, but there are still large uncertainties concerning evaporation and aquatic photosynthesis. Here we combined measurements of water chemistry, isotopic compositions (ie, δ D w, δ 18 O w, δ 13 C DIC and▵ 14 C DIC) and geographic characteristics (ie, river width) to elucidate in-stream hydrological and biogeochemical processes across rivers in Hainan Island, China. The results showed that dissolved inorganic carbon (DIC) in river waters was largely of modern origin, with about 95% from contemporary biogenic sources based on an isotopic mass balance of▵ 14 C DIC. Significant evaporation and aquatic primary production co-occurred in these tropical rivers with large amounts of water and DIC being rapidly turned over in the water column, altering the water cycle and the carbon balance. High rates of evaporation and aquatic primary production were observed in the headwater segments, with narrow river width but broad available reactive surface area at the air-water interface. The asymmetric aquatic photosynthesis at different river segments caused the spatial heterogeneities of dissolved solutes. The results suggest that the available reactive area at the water-air interface is responsible for synchronous water loss and dissolved carbon evolution in flat tropical rivers. This study provides evidence that intense evaporation and aquatic photosynthesis mainly occurred in headwater segments, which has implications for understanding global carbon cycling.