Delineating the controlling mechanisms of arsenic release into groundwater and its associated health risks in the Southern Loess Plateau, China

Xiao Zhang; Rong Zhao; Xiong Wu; Wenping Mu; Chu Wu

doi:10.1016/j.watres.2022.118530

Delineating the controlling mechanisms of arsenic release into groundwater and its associated health risks in the Southern Loess Plateau, China

Water Res. 2022 Jul 1:219:118530. doi: 10.1016/j.watres.2022.118530. Epub 2022 May 1.

Authors

Xiao Zhang¹, Rong Zhao¹, Xiong Wu², Wenping Mu³, Chu Wu⁴

Affiliations

¹ School of Water Resources and Environment, China University of Geosciences (Beijing), Beijing 100083, China.
² School of Water Resources and Environment, China University of Geosciences (Beijing), Beijing 100083, China. Electronic address: wuxiong@cugb.edu.cn.
³ School of Engineering and Technology, China University of Geosciences (Beijing), Beijing 100083, China.
⁴ Department of Water Resources, China Institute of Water Resources and Hydropower Research, Beijing 100083, China.

PMID: 35533622
DOI: 10.1016/j.watres.2022.118530

Abstract

The mechanisms controlling arsenic (As) enrichment and mobilization associated with human health risk assessment of groundwater in the Longdong Basin, located in the southern part of the Loess Plateau, China, have been yet unexplained. This uncertainty is partly attributed to a poor understanding of groundwater arsenic management. To address this problem, this study investigated the occurrence and spatial distribution of As in unconfined groundwater (UG) and confined groundwater (CG) in the study area, integrated Self-Organizing Maps (SOM) and geochemical modeling to elucidate the mechanisms controlling As release and mobilization in groundwater, and conducted a health risk assessment of groundwater As. The results showed that 13.6% of UG samples (n = 66) and 22.4% of CG samples (n = 98) exceeded the WHO guideline limit of As (10 μg/L). The detailed hydrogeochemical studies showed that As-enrichment groundwater is dominated by Cl-Na type, and Gaillardet diagram indicated that evaporites weathering may contribute to As mobilization in CG. The SOM analysis combined with Spearman's correlation coefficient quantified the negative correlation between As and redox potential, dissolved oxygen, SO₄^2-, NO₃^-, and the positive correlation between As and HCO₃^-, Mn in UG. In CG, As is positively correlated to pH and negatively to electrical conductivity, SO₄^2-, Fe and Mn. The saturation indices of the mineral phases indicates an insignificant relationship between As and Fe. We conclude that under oxidizing conditions, evaporative controls and the desorption of Fe-oxides under alkaline and high salinity conditions are the dominant mechanisms controlling As release and mobilization in groundwater. In addition, exposure to groundwater As through drinking water posed potential risk of carcinogenic and non-carcinogenic effects on children and adults. This study contributes to groundwater As management and sustainable safe groundwater supply.

Keywords: Arsenic; Geochemical modelling; Groundwater; Health risk assessment; Mobilization; Self-Organizing Maps.

MeSH terms

Arsenic* / analysis
Child
China
Drinking Water* / analysis
Environmental Monitoring
Groundwater* / analysis
Humans
Water Pollutants, Chemical* / analysis

Substances

Drinking Water
Water Pollutants, Chemical
Arsenic