School of Environmental Studies, China University of Geosciences, Wuhan 430074, Hubei, China; State Environmental Protection Key Laboratory of Source Apportionment and Control of Aquatic Pollution, Ministry of Ecology and Environment, Wuhan 430074, Hubei, China.
Key Laboratory of Cenozoic Geology and Environment, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China.
Sci Total Environ. 2022 Sep 10;838(Pt 2):155898. doi: 10.1016/j.scitotenv.2022.155898. Epub 2022 May 13.
Arsenic-affected aquifers are broadly found in floodplains of South Asia and Southeast Asia, which are supplied by rivers that originate from the Tibetan Plateau. Earlier investigations have ascertained the Arsenic (As) enrichment of river water in the Tibetan Plateau. However, the source, migration, and flux of As in catchment-scale have not been well constrained. In this study, determinations have been made of As and other chemical components in geothermal spring, rock, river water, and suspended particulate material in the Xiangqu River basin, a tributary of the Yarlung Tsangpo River. The study has shown that the main stream waters contain a high concentration of dissolved As (>10 μg/L), whereas the majority of tributaries present a relatively low dissolved concentration (<10 μg/L), with the highest dissolved As levels occurring during the low-flow period (April to June) and the lowest during the high-flow period (July to September). Moreover, the study has found that with the geothermal spring discharge in the upper reaches being the principal source of dissolved As, the proportion of As derived from rock weathering increases during the high-flow period, and the decrease of dissolved As concentration in the main stream is dominated by the adsorption process in the upper reaches and the mixing of tributary water in the lower reaches. The particulate As is temporally stable throughout the sampling period. Due to the high erosion rate during the high-flow period, the annual As flux is 76.8 t/yr and As is primarily transported as particulate (79%). Furthermore, the contribution of weathering (58-62%) is more than that of geothermal spring discharge (38-42%) to the total As in river water. Overall, this study has highlighted a non-conservative As behavior in the upper reaches of river flows in a geothermal field on the Tibetan Plateau.
砷污染含水层广泛分布于南亚和东南亚的冲积平原，这些平原由源自青藏高原的河流供水。早期的调查已经确定了青藏高原河流水中的砷（As）富集。然而，流域尺度上的 As 来源、迁移和通量尚未得到很好的限制。在这项研究中，对香曲河流域（雅鲁藏布江的一条支流）的温泉、岩石、河水和悬浮颗粒物中的 As 及其他化学成分进行了测定。研究表明，主流水中含有高浓度的溶解态 As（>10μg/L），而大多数支流的溶解浓度相对较低（<10μg/L），在低流量期（4 月至 6 月）溶解 As 浓度最高，在高流量期（7 月至 9 月）最低。此外，研究发现，上游温泉的排泄是溶解态 As 的主要来源，随着高流量期岩石风化产生的 As 比例增加，上游吸附过程和下游支流混合导致主流中溶解 As 浓度降低。颗粒态 As 在整个采样期间是稳定的。由于高流量期侵蚀率较高，年 As 通量约为 76.8 t/yr，As 主要以颗粒态（~79%）运输。此外，风化（58-62%）对河水总 As 的贡献大于温泉排泄（38-42%）。总体而言，本研究强调了青藏高原地热田河流上游非保守的 As 行为。
