Seasonal riverine barium isotopic variation in the middle Yellow River: Sources and fractionation
Seasonal riverine barium isotopic variation in the middle Yellow River: Sources and fractionation
复制标题
黄河中游河流钡同位素季节性变化：来源与分馏
DOI：
10.1016/j.epsl.2019.115990
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发表时间：
2020-02-01
影响因子：
5.3
通讯作者：
Huang, Fang
中科院分区：
文献类型：
--
作者：
Gou, Long-Fei;Jin, Zhangdong;Huang, Fang
钡（Ba）同位素已被用于追踪海洋中的水团混合和输出生产力。然而，溶解钡在大江大河的来源，同位素特征和季节变化仍然缺乏约束。为了加深对黄河Ba同位素大陆尺度来源和分馏的认识，2013年在黄河中游进行了全水文年度的每周河水采样。在黄土覆盖的干旱-半干旱盆地，溶解钡主要来源于硅酸盐的溶解，其通量与物理侵蚀速率有关。在季风季节（6月至9月中旬），特别是在风暴事件期间（占4%的年度溶解钡通量在4天），每年溶解钡通量的一半以上的输送。溶解Ba同位素组成（δ（138）Ba-rw）范围为+0.17 ‰ ~+0.46 ‰，均高于黄土δ Ba-138（0.00 +/- 0.04 ‰）。在三角洲Ba-138（rw）的季节性变化是最好的解释，通过轻Ba同位素到固体在河流中，这是敏感的黄土侵蚀，特别是在风暴事件和春季融冰的间隔，在干旱季节地下水中的重晶石沉淀的潜在作用的吸附模型。在季风季节，黄河等河流的颗粒物通量高出1 ~ 3个数量级，Ba的解吸可能会导致沿岸环境中Ba浓度和同位素组成的强烈变化，这需要进一步研究。(C)2019 Elsevier B. V.版权所有。
Barium (Ba) isotopes have been used to trace water mass mixing and export productivity in the oceans. However, the sources, isotopic signature and seasonal variation of dissolved Ba in large rivers remain poorly constrained. In order to improve our understanding of sources and fractionation of riverine Ba isotopes at the continental scale, weekly sampling of river water was carried out in the middle Yellow River over the full hydrological year of 2013. Dissolved Ba was mainly sourced from silicate dissolution, whose flux was correlated with physical erosion rate in this arid to semi-arid basin, largely covered by loess. More than half of the annual dissolved Ba flux was transported during the monsoon season (June to mid-September), in particular during a storm event period (accounting for 4% of the annual dissolved Ba flux in 4 days). The dissolved Ba isotopic composition (delta (138) Ba-rw) ranged from +0.17 parts per thousand to +0.46 parts per thousand, all higher than delta Ba-138 of loess (0.00 +/- 0.04 parts per thousand). The seasonal variation in delta Ba-138(rw) is best explained via an adsorption model of light Ba isotopes onto solids in the river, which is sensitive to erosion of loess, in particular during the storm event and the spring-time ice melting intervals, with a potential role of barite precipitation in groundwater during the dry seasons. With one to three orders of magnitude higher particulate matter fluxes during the monsoon seasons in rivers such as the Yellow River, desorption of Ba could result an unaccounted strong variation of Ba concentration and isotopic composition in coastal environments, which further study requires. (C) 2019 Elsevier B.V. All rights reserved.