River bank geomorphology controls groundwater arsenic concentrations in aquifers adjacent to the Red River, Hanoi Vietnam

Stahl, Mason; Harvey, Charles F.; Geen, Alexander van; Sun, Jing; Trang, Pham Thi Kim; Lan, Vi Mai; Phuong, Thao Mai; Viet, Pham Hung; Bostick, Benjamín C.

doi:10.1002/2016wr018891

Cited by 63 publications

(62 citation statements)

References 40 publications

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“…The increased As concentration in M2 relative to M1 ranged from 0 to 0.53 μmol/L, accounting for 0% to around 16% of the total As concentrations modeled in M1, illustrating that groundwater As concentration estimates should decrease when simultaneously considering the abiotic reduction of Fe (III) oxides by H 2 S and the coprecipitation/adsorption of As with/onto mackinawite. (Stahl et al, 2016), aquifer sediment from the Bengal Basin (Dowling et al, 2002), aquifer sediment from the Mekong Delta, Cambodia (B.D. Kocar et al, 2014), and aquifer sediments from this study with As release rates of 0.006-0.012 μmol/L/yr.…”

Section: Chemical Reduction Of Fe (Iii) Oxides By H 2 Smentioning

confidence: 88%

Quantifying Geochemical Processes of Arsenic Mobility in Groundwater From an Inland Basin Using a Reactive Transport Model

Gao

Jia

Guo

et al. 2020

Water Resources Research

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High arsenic (As) groundwater is frequently found in inland basins, yet the contributions of different processes to aqueous As distributions remain unresolved. In the Hetao Basin, a typical inland basin, groundwater As concentrations generally increased from the alluvial fan through the transition area to the flat plain. A geochemical process‐based reactive transport model was established to evaluate and quantify the processes of As mobilization in the northwestern Hetao Basin. Thirty‐six groundwater samples and eight sediment samples were collected from the alluvial fan to the flat plain to investigate the geochemical characteristics of the groundwater system. Along the approximate flow path, groundwater evolved from oxic‐suboxic conditions to anoxic conditions, with increasing concentrations of As, Fe (II), and NH4+, and decreasing Eh and SO42−/Cl−. Modeling results indicated that the observed concentrations of Fe (II) were caused by reductive dissolution of Fe (III) oxides and subsequent precipitation of mackinawite and siderite. Reductive dissolution of Fe (III) oxides was primarily driven by organic matter degradation (>75%), followed by H2S oxidation (<25%). More As was sequestered by mackinawite precipitation and adsorption than that released via abiotic reduction of Fe (III) oxides by H2S. Reductive dissolution of Fe (III) oxides was the dominant mechanism for liberating As in both the transition area and the flat plain (>70%), and As desorption under elevated pH and competitive adsorption by HCO3− and PO43− made an important contribution to As enrichment (up to 30%). Overall, this study provides an insight into the relative contributions of different geochemical processes to As enrichment in inland basins.

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Section: Chemical Reduction Of Fe (Iii) Oxides By H 2 Smentioning

confidence: 88%

Quantifying Geochemical Processes of Arsenic Mobility in Groundwater From an Inland Basin Using a Reactive Transport Model

Gao

Jia

Guo

et al. 2020

Water Resources Research

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“…Research into arsenic has been conducted at this site for more than 10 years . The aquifers at Van Phuc are shallow, and the lateral depositions of Holocene and Pleistocene sediments are generally not hydraulically separated by an Water Resources Research 10.1002/2017WR020551 aquitard [Stahl et al, 2016]. Similar to the situation in many delta regions of S/SE Asia, reductive dissolution of Fe-oxide minerals in the younger Holocene depositions at Van Phuc has resulted in the natural enrichment of arsenic in groundwater .…”

Section: Study Sitementioning

confidence: 98%

Processes governing arsenic retardation on Pleistocene sediments: Adsorption experiments and model‐based analysis

Rathi

Neidhardt

Berg

et al. 2017

Water Resources Research

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In many countries of south/south‐east Asia, reliance on Pleistocene aquifers for the supply of low‐arsenic groundwater has created the risk of inducing migration of high‐arsenic groundwater from adjacent Holocene aquifers. Adsorption of arsenic onto mineral surfaces of Pleistocene sediments is an effective attenuation mechanism. However, little is known about the sorption under anoxic conditions, in particular the behavior of arsenite. We report the results of anoxic batch experiments investigating arsenite (1–25 µmol/L) adsorption onto Pleistocene sediments under a range of field‐relevant conditions. The sorption of arsenite was nonlinear and decreased with increasing phosphate concentrations (3–60 µmol/L) while pH (range 6–8) had no effect on total arsenic sorption. To simulate the sorption experiments, we developed surface complexation models of varying complexity. The simulated concentrations of arsenite, arsenate, and phosphate were in good agreement for the isotherm and phosphate experiments while secondary geochemical processes affected the pH experiments. For the latter, the model‐based analysis suggests that the formation of solution complexes between organic buffers and Mn(II) ions promoted the oxidation of arsenite involving naturally occurring Mn‐oxides. Upscaling the batch experiment model to a reactive transport model for Pleistocene aquifers demonstrates strong arsenic retardation and could have useful implications in the management of arsenic‐free Pleistocene aquifers.

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“…Ferrihydrite and goethite were used in this study because both of them are environmentally important minerals in aquifers (Gimenez et al, 2007; Stahl et al, 2016; Sun et al, 2016d, 2018), which supposedly effectively dissolve in the presence of oxalate (Gadol et al, 2017; Lee et al, 2007; Sun et al, 2016c). In our columns, initially, the amount of substrate dissolution was linearly correlated to the amount of oxalic acid that was injected (Fig.…”

Section: Discussionmentioning

confidence: 99%

“…It is challenging to achieve 100% As removal where As is associated with crystalline minerals. Fortunately, residual As, in such a scenario, will be less likely to be a source for future contamination of the groundwater (Rawson et al, 2017; Stahl et al, 2016; Sun et al, 2016a), because oxalic acid would have removed the “vulnerable” fraction of the As in the sediments.…”

Section: Discussionmentioning

confidence: 99%

Arsenic mobilization from iron oxides in the presence of oxalic acid under hydrodynamic conditions

et al. 2018

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Oxalic acid potentially enhances pump-and-treat for groundwater As remediation by accelerating mobilization. This study examines how oxalic acid mobilizes As from Fe(III)-oxide coated sand under hydrodynamic conditions. Four columns were packed with metal-substituted ferrihydrite or goethite to 1% Fe, presorbed to 50% As surface coverage, and reacted with pH = 2.2 artificial groundwater amended with 10 mM oxalic acid at 1 m day. Arsenic elution was affected by both As and Fe speciation. Although the As(V) columns experienced faster substrate dissolution, As(V) elution was delayed by re-adsorption, whereas As(III) elution was rapid due to pH decrease that prevented re-adsorption. Cr-ferrihydrite and Ni-goethite dissolved both effectively initially but then diverged. The Cr-ferrihydrite columns experienced continuous stoichiometric Fe and Cr release, and As release could be sustained. The Ni-goethite columns initially experienced nonstoichiometric Fe and Ni release, and As release was extensive. Such release, however, was not sustained. We hypothesized that Ni-goethite contained sites with distinct reactivity, and oxalic acid targeted readily-dissolved, sorption-dense sites. Our data indicate that oxalic acid-enhanced pump-and-treat methods would be easier to apply to aquifers dominated by As(III), requiring less amendment to be injected; such oxalic acid-enhanced methods remove reactive sediment Fe and As, potentially preventing future groundwater contamination.

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River bank geomorphology controls groundwater arsenic concentrations in aquifers adjacent to the Red River, Hanoi Vietnam

Cited by 63 publications

References 40 publications

Quantifying Geochemical Processes of Arsenic Mobility in Groundwater From an Inland Basin Using a Reactive Transport Model

Quantifying Geochemical Processes of Arsenic Mobility in Groundwater From an Inland Basin Using a Reactive Transport Model

Processes governing arsenic retardation on Pleistocene sediments: Adsorption experiments and model‐based analysis

Arsenic mobilization from iron oxides in the presence of oxalic acid under hydrodynamic conditions

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