Contribution of clay-aquitard to aquifer iron concentrations and water quality

Yanjun Liu; Teng Ma; Juan Chen; Cong Xiao; Rui Liu; Yao Du; Scott Fendorf

doi:10.1016/j.scitotenv.2020.140061

Contribution of clay-aquitard to aquifer iron concentrations and water quality

Sci Total Environ. 2020 Nov 1:741:140061. doi: 10.1016/j.scitotenv.2020.140061. Epub 2020 Jun 8.

Authors

Yanjun Liu¹, Teng Ma², Juan Chen³, Cong Xiao³, Rui Liu³, Yao Du³, Scott Fendorf⁴

Affiliations

¹ School of Environmental Studies, China University of Geosciences, Wuhan 430074, China; Department of Earth System Science, Stanford University, Stanford 94305, USA.
² School of Environmental Studies, China University of Geosciences, Wuhan 430074, China; State Key Laboratory of Biogeology and Environmental Geology, Wuhan 430074, China. Electronic address: mateng@cug.edu.cn.
³ School of Environmental Studies, China University of Geosciences, Wuhan 430074, China.
⁴ Department of Earth System Science, Stanford University, Stanford 94305, USA.

PMID: 32603935
DOI: 10.1016/j.scitotenv.2020.140061

Abstract

The contribution of aquitards to aquifer water quality can be pronounced but is rarely considered. The aims of this study were to delineate the spatial distribution of iron in a shallow aquitard-aquifer system within Jianghan Plain (JHP) of central China and to identify the origin of high iron within aquifers. Infiltration, hydraulic gradients and sediment chemistry influence the distribution of iron in the aquitard pore water which has a significant effect on the underlying aquifer. Chemical equilibrium modeling of pore water was used to simulate chemical processes influencing aquifer chemistry and determined the possible precipitation of FeCO₃, FeS minerals (FeSx) and Fe-oxides (representing hydroxides, oxyhydroxides, and oxides of ferric iron). We presented a conceptual chemical-physical scenario to explain the observed Fe distributions: (1) Increasing iron concentrations with low-level sulfide in aquitard pore water. (2) Increasing iron concentrations with low-level sulfide in aquitard pore water underlying ponded water. (3) Decreasing iron concentrations with high-level sulfide in aquitard pore water. In combination, our findings illustrate the influence of aquitards on aquifer chemistry using Fe within the Jianghan Plain as an example.

Keywords: Aquifer; Aquitard; Iron; Pore water.