Clay-plug sediment as the locus of arsenic pollution in Holocene alluvial-plain aquifers

Investigation of Potential Drivers of Elevated Uranium Prevalence in Indian Groundwaters with a Unified Speciation Model

“…The shaded region within the solid lines indicates 1σ variation of the means. The total adsorbent mass concentrations of ferrihydrite (F), goethite (G), and manganese dioxide (M) were assumed to be 454, 378, and 1.3 g L –1 , respectively, based on the reported literature. − IGP stands for the Indo-Gangetic Plain.…”

“…A three-plane CD-MUSIC model for ferrihydrite and goethite and a diffuse layer model for manganese dioxide , were used to quantify the surface charge and its electrostatics. The average bulk density (2.07 g cm –3 ), porosity (0.44), and concentrations of Fe (64.2 mg g –1 ) and Mn (221.1 μg g –1 ) from reported total elemental concentrations in Indian aquifer sediments − were used to make estimates of the average concentrations (±1σ) of ferrihydrite as 123 ± 69 g kg –1 , goethite as 102 ± 57 g kg –1 , and of manganese dioxide as 350 ± 401 mg kg –1 . The estimated phase concentrations were conservative upper limits, given that measurements in sediments sampled from the Bengal delta have suggested only ∼27% of total Fe as ferrihydrite and ∼21% of total Fe as goethite .…”

Predictive geospatial model for arsenic accumulation in Holocene aquifers based on interactions of oxbow-lake biogeochemistry and alluvial geomorphology

“…Upon microbial mobilization in the clay-plug sediment, (pathways indicated in Fig. 8), the dissolved arsenic migrates along the porosity-permeability gradient and accumulates in juxtaposed porous and permeable point-bar and levee sands by the processes of gravitational, compaction-driven diffusion in the clay plug, and transport-driven advection past the permeability boundaries at the interface of clay-plug to point-bar, and clay-plug to levee (Kumar et al, 2021a).…”

“…Ever since, research into the occurrence of toxic natural arsenic levels above the recommended upper limit of 10 μg/L (World Health Organization (WHO), 2011) in food, drinking and irrigation water from groundwater sources has greatly advanced our knowledge of all aspects of the arsenic issue, from its provenance to transport modes and deposition in sedimentary basins, uptake by humans and its severe health impact for many millions of people around the world (Guha Mazumder, 2003;Saha, 2003;Chikkanna et al, 2019;Kavil et al, 2020). The wide range of natural-arsenic studies deals with: (1) Identification of the provenance of natural arsenic in orogenic mountain belts (Göd and Zemann, 1999;Horton et al, 2001;Campbell et al, 2004;Mukherjee et al, 2014Mukherjee et al, , 2019Tapia et al, 2019, among others), (2) The accumulation of geogenic arsenic in Holocene floodbasins as solid-state arsenic iron-oxyhydroxides, arsenopyrites, biotite (Bhattacharya et al, 2006;Bundschuh et al, 2004;Berg et al, 2007;Huang et al, 2011;Ramos et al, 2014;Kumar et al, 2021a; among others), (3) The role of microbial metabolism processes in the mobilization of arsenic from its solid state and subsequent accumulation in alluvial-plain aquifers (Nickson et al, 1998(Nickson et al, , 2000Acharyya et al, 2000;Acharyya and Shah, 2007;Seddique et al, 2008;Lawson et al, 2013;Sahu and Saha, 2015;Donselaar et al, 2017;Ghosh et al, 2021), (4) The health risks of arsenic uptake by food, water consumption and irrigation (Islam et al, 2000;Zhao et al, 2010;Rahman et al, 2018;Roychowdhury et al, 2018;Kavil et al, 2020;Zhao and Wang, 2020;Kumar et al, 2021b;…”

“…Studies with focus on the abundance of arsenic concentration in the Holocene lithostratigraphy and the drop of concentrations in underlying Pleistocene stratigraphy have yielded a generalized perspective of stratigraphic control on arsenic distribution in shallow aquifers of alluvial floodbasins (e.g., Bhattacharya et al, 2006;Berg et al, 2007;Aziz et al, 2008;Guo et al, 2008;Van Geen et al, 2008, 2013Weinman et al, 2008;Hoque et al, 2009Hoque et al, , 2014McArthur et al, 2011;Robinson et al, 2011;Postma et al, 2012Postma et al, , 2016Sahu and Saha, 2015;Stopelli et al, 2020;Wallis et al, 2020;Kazmierczak et al, 2022). Mukherjee et al (2010), Donselaar et al (2017), Cao et al (2018), Trung et al (2020), Das and Mondal (2021), Ghosh et al (2021), and Kumar et al (2021a) have taken the concept of lithostratigraphic control one step further by relating porosity and permeability anisotropy in genetically-related, juxtaposed (1) clayey floodplain and oxbow-lake, and…”