Sources of groundwater salinity and potential impact on arsenic mobility in the western Hetao Basin, Inner Mongolia

Yongfeng Jia; Huaming Guo; Beidou Xi; Yonghai Jiang; Zhuo Zhang; Rongxiao Yuan; Weixiong Yi; Xiaolei Xue

doi:10.1016/j.scitotenv.2017.05.196

Sources of groundwater salinity and potential impact on arsenic mobility in the western Hetao Basin, Inner Mongolia

Sci Total Environ. 2017 Dec 1:601-602:691-702. doi: 10.1016/j.scitotenv.2017.05.196. Epub 2017 May 31.

Authors

Yongfeng Jia¹, Huaming Guo², Beidou Xi³, Yonghai Jiang³, Zhuo Zhang⁴, Rongxiao Yuan⁴, Weixiong Yi⁵, Xiaolei Xue⁶

Affiliations

¹ State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Beijing 100083, China; State Environmental Protection Key Laboratory of Simulation and Control of Groundwater Pollution, Chinese Research Academy of Environmental Sciences, Beijing 100012, China; School of Water Resources and Environment, China University of Geosciences (Beijing), Beijing, 100083, China.
² State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Beijing 100083, China; School of Water Resources and Environment, China University of Geosciences (Beijing), Beijing, 100083, China. Electronic address: hmguo@cugb.edu.cn.
³ State Environmental Protection Key Laboratory of Simulation and Control of Groundwater Pollution, Chinese Research Academy of Environmental Sciences, Beijing 100012, China.
⁴ State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Beijing 100083, China; School of Water Resources and Environment, China University of Geosciences (Beijing), Beijing, 100083, China.
⁵ State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Beijing 100083, China; China Urban Construction Design &Research Institute, Changsha 410000, China.
⁶ State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Beijing 100083, China.

PMID: 28577404
DOI: 10.1016/j.scitotenv.2017.05.196

Abstract

The quality of groundwater used for human consumption and irrigation in the Hetao Basin of Inner Mongolia, China is affected by elevated salinity as well as high arsenic (As) concentrations. However, the origin of high salinity and its potential impact on As mobility in the Basin remain unclear. This study explores both issues using stable isotopic compositions and Cl/Br ratios of groundwater as well as the major ions of both groundwater and leachable salts in aquifer sediments. Limited variations in δ¹⁸O and δ²H (-11.13 to -8.10, -82.23 to -65.67) with the wide range of Total Dissolved Solid (TDS, 351-6734mg/L) suggest less contribution of direct evaporation to major salinity in groundwater. Deuterium excess shows that non-direct evaporation (capillary evaporation, transpiration) and mineral/evaporite dissolution contribute to >60% salinity in groundwater with TDS>1000mg/L. Non-direct evaporation, like capillary evaporation and transpiration, is proposed as important processes contributing to groundwater salinity based on Cl/Br ratio and halite dissolution line. The chemical weathering of Ca, Mg minerals and evaporites (Na₂SO₄ and CaSO₄) input salts into groundwater as well. This is evidenced by the fact that lacustrine environment and the arid climate prevails in Pleistocene period. Dissolution of sulfate salts not only promotes groundwater salinity but affects As mobilization. Due to the dissolution of sulfate salts and non-direct evaporation, groundwater SO₄^2- prevails and its reduction may enhance As enrichment. The higher As concentrations (300-553μg/L) are found at the stronger SO₄^2- reduction stage, indicating that reduction of Fe oxide minerals possibly results from HS^- produced by SO₄^2- reduction. This would have a profound impact on As mobilization since sulfate is abundant in groundwater and sediments. The evolution of groundwater As and salinity in the future should be further studied in order to ensure sustainable utilization of water resource in this water scarce area.

Keywords: Cl/Br ratio; Evaporation; Groundwater arsenic; Hetao Basin; Salinization; Sulfate reduction.