Spatial and seasonal variations of dissolved arsenic in the Yarlung Tsangpo River, southern Tibetan Plateau

Jun-Wen Zhang; Ya-Ni Yan; Zhi-Qi Zhao; Xiao-Dong Li; Jian-Yang Guo; Hu Ding; Li-Feng Cui; Jun-Lun Meng; Cong-Qiang Liu

doi:10.1016/j.scitotenv.2020.143416

Spatial and seasonal variations of dissolved arsenic in the Yarlung Tsangpo River, southern Tibetan Plateau

Sci Total Environ. 2021 Mar 15:760:143416. doi: 10.1016/j.scitotenv.2020.143416. Epub 2020 Nov 17.

Authors

Jun-Wen Zhang¹, Ya-Ni Yan², Zhi-Qi Zhao³, Xiao-Dong Li¹, Jian-Yang Guo⁴, Hu Ding¹, Li-Feng Cui¹, Jun-Lun Meng⁴, Cong-Qiang Liu⁵

Affiliations

¹ Institute of Surface-Earth System Science, School of Earth System Science, Tianjin University, Tianjin 300072, China.
² School of Earth Science and Resources, Chang'an University, Xi'an 710054, China.
³ School of Earth Science and Resources, Chang'an University, Xi'an 710054, China. Electronic address: zhaozhiqi@chd.edu.cn.
⁴ State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China.
⁵ Institute of Surface-Earth System Science, School of Earth System Science, Tianjin University, Tianjin 300072, China. Electronic address: liucongqiang@tju.edu.cn.

PMID: 33246731
DOI: 10.1016/j.scitotenv.2020.143416

Abstract

High levels of dissolved arsenic (As) have been reported in many rivers running though the Tibetan Plateau (TP), the "Water Tower of Asia". However, the source, spatiotemporal variations, and geochemical behavior of dissolved As in these rivers remain poorly understood. In this study, hot spring, river water, and suspended particulate material samples collected from the Yarlung Tsangpo River (YTR) (upper reaches of the Brahmaputra River) system in 2017 and 2018 were analyzed. Spatial results shown that the upper reaches of YTR (Zone I) have comparatively high levels of dissolved As ([As]_dissolved: mean 31.7 μg/L; 4.7-81.6 μg/L; n = 16), while the tributaries of the lower reaches (Zone II) have relatively low levels (mean 0.54 μg/L; 0.11-1.3 μg/L; n = 7). Seasonal results shown that the high [As]_dissolved (6.1-22.4 μg/L) were found in September to June and low [As]_dissolved (1.4-3.7 μg/L) were observed in July to August. Geothermal water is suspected as the main source of the elevated As levels in YTR due to the extremely high [As]_dissolved in hot springs (1.13-9.76 mg/L) and abundance of geothermal systems throughout TP. However, the seasonal results suggested that weathering of As-containing rocks and minerals is also a key factor affecting the [As]_dissolved in the river water in July to August (wet-season). Natural attenuation of As in main channel is dominated by dilution process due to the lower As concentrations in tributaries, but mostly occurred by both dilution and adsorption (or co-precipitation) processes in tributaries. This work highlights that the weathering process may have an important contribution to the dissolved As in the river waters in wet-season, and the geochemical behavior of As is largely transported conservatively in the main channel and relative non-conservatively in the tributaries in YTR system.

Keywords: Arsenic; Hot spring; Hydrochemistry; Residence time; Yarlung Tsangpo River.