Seasonal and Spatial Variations of Chemical Weathering in the Mekong Basin: From the Headwaters to the Lower Reaches
Seasonal and Spatial Variations of Chemical Weathering in the Mekong Basin: From the Headwaters to the Lower Reaches
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DOI：
10.1007/s10498-020-09374-y
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发表时间：
2020-04-23
影响因子：
1.6
通讯作者：
Kawahata, Hodaka
中科院分区：
文献类型：
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作者：
Kajita, Hiroto;Ota, Yuki;Kawahata, Hodaka
喜马拉雅河流域的化学风化是世界上最高的地区之一，受到了与过去气候变化有关的广泛研究关注。许多化学风化的早期估计是基于少量的水属性数据，忽略了这些空间和季节变化。因此，本研究分析了湄公河流域化学风化的空间和季节变化，该流域的地质，气候和水文循环从下游到上游，从旱季到雨季变化显着。我们分别估计了溶解元素的来源和潜在的CO2消耗率使用的众多化学成分的河水在整个流域和两个季节。雨季的二氧化碳消耗率是旱季的三到五倍，这可能是由于高温和降水。尽管上游和中部盆地温度低、干燥，但CO2消耗率约为下游的两倍;这可归因于陡峭山区的积极物理剥蚀，增加了水-岩相互作用的表面积。通过结合每个季节和盆地获得的硅酸盐和碳酸盐风化的总CO2消耗量分别为48-70 x 10（9）mol/a和148-159 x 10（9）mol/a，几乎是以前估计值的一半。我们的研究结果表明，季节性和空间分离的评价是重要的，产生估计的化学风化在大型喜马拉雅河流。
Chemical weathering in the Himalayan river basins is among the highest in the world and has received vast research attention related to past climate change. Many early estimates of chemical weathering are based on a small number of water property data that ignore those spatial and seasonal variations. Therefore, this study analyzed spatial and seasonal variations in chemical weathering in the Mekong Basin, where the geology, climate, and hydrologic cycle of the basin vary significantly from the lower to upper reaches and from dry to rainy seasons. We separately estimated the origins of dissolved elements and potential CO2 consumption rates using the numerous chemical compositions of river water throughout the entire basin and in both seasons. The CO2 consumption rate in the rainy season is three to five times that in the dry season that may be due to the high temperature and precipitation. Despite the low temperatures and dryness of the upper and middle basins, the CO2 consumption rate is approximately twice that in the lower reaches; this can be attributed to active physical denudation in steep mountainous areas which increases the surface area for water-rock interactions. The total CO2 consumption obtained by combining each season and basin was 48-70 x 10(9) mol/a and 148-159 x 10(9) mol/a for silicate and carbonate weathering, respectively, which are almost half the values of previous estimates. Our results suggest that seasonally and spatially separated evaluations are important for generating estimates of chemical weathering in large Himalayan rivers.