Hydrogeochemical evidences for targeting sources of safe groundwater supply in arsenic-affected multi-level aquifer systems

Yao Du; Yamin Deng; Teng Ma; Zongjie Lu; Shuai Shen; Yiqun Gan; Yanxin Wang

doi:10.1016/j.scitotenv.2018.07.173

Hydrogeochemical evidences for targeting sources of safe groundwater supply in arsenic-affected multi-level aquifer systems

Sci Total Environ. 2018 Dec 15:645:1159-1171. doi: 10.1016/j.scitotenv.2018.07.173. Epub 2018 Jul 21.

Authors

Yao Du¹, Yamin Deng², Teng Ma³, Zongjie Lu⁴, Shuai Shen⁵, Yiqun Gan¹, Yanxin Wang¹

Affiliations

¹ School of Environmental Studies, China University of Geosciences, Wuhan 430074, China; Laboratory of Basin Hydrology and Wetland Eco-restoration, China University of Geosciences, Wuhan 430074, China.
² Geological Survey, China University of Geosciences, Wuhan 430074, China. Electronic address: yamin.deng@cug.edu.cn.
³ School of Environmental Studies, China University of Geosciences, Wuhan 430074, China; Laboratory of Basin Hydrology and Wetland Eco-restoration, China University of Geosciences, Wuhan 430074, China. Electronic address: mateng@cug.edu.cn.
⁴ Geological Survey, China University of Geosciences, Wuhan 430074, China.
⁵ School of Environmental Studies, China University of Geosciences, Wuhan 430074, China.

PMID: 30248841
DOI: 10.1016/j.scitotenv.2018.07.173

Abstract

Delineation of safe aquifers becomes highly imperative and challenging to ensure sustainable drinking water supply in rural areas of multi-level aquifer systems with complex water circulation under the impact of both geogenic and anthropogenic contamination. This work characterized hydrogeological and hydrogeochemical features of a multi-level Quaternary aquifer system of the central Yangtze River Basin to search for evidences of locating aquifers least contaminated. The results indicate modern hydrologic cycling is active in shallow phreatic aquifer (SPA) and in upper part of middle confined aquifer (MCA-1). The lower part of middle confined aquifer (MCA-2) and deep confined aquifer (DCA) have ages ranging from 200 to 2000 years and 4000 to >20,000 years, respectively. Vertical variations of hydrochemical compositions and Cl/Br ratios suggest the gradually decreasing and increasing contribution with depth from anthropogenic activities and natural water-mineral interactions, respectively. The SPA is characterized by high levels of anthropogenic components (Cl^-, SO₄^2-, NO₃^-, organic pesticides and antibiotics). The MCA-1 is the main aquifer where most private tube wells were installed, typically contains geogenic As, Fe, Mn and NH₄⁺ at concentration levels several hundred times higher than the national drinking water standard values. Organic-abundant geochemical and stagnant hydrogeological conditions favor their enrichment. Both MCA-2 and DCA are slightly influenced by geogenic contamination and groundwater pumping from public wells screened in MCA-2 does not or slightly perturbs the groundwater flow condition in MCA-2 and DCA. The cost-effective water supply strategy is either to maintain safe yield of groundwater from public wells screened in MCA-2, or to use the groundwater after simple filtration and aeration treatment in case that groundwater pumping in MCA-2 were over a "safe yield" or induced leakage of groundwater containing As, Fe, Mn and NH₄⁺ from the overlying MCA-1. And DCA could serve as a source for water supply under emergency circumstances.

Keywords: Anthropogenic activities; Geogenic contamination; Groundwater; Jianghan Plain; Water quality.