Surface complexation modeling of groundwater arsenic mobility: Results of a forced gradient experiment in a Red River flood plain aquifer, Vietnam

Jessen, Søren; Postma, Dieke; Larsen, Flemming; Nhân, Phạm Quý; Hoa, Le Quynh; Trang, Pham Thi Kim; Long, Tran Vu; Viet, Pham Hung; Jakobsen, Rasmus

doi:10.1016/j.gca.2012.07.014

Cited by 52 publications

(60 citation statements)

References 48 publications

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“…Some shorter time series have shown significant seasonal variability in groundwater composition, particularly in shallow aquifers, but by and large variations in groundwater As have been much more limited (BGS/DPHE, 2001; Cheng et al, 2005; Dhar et al, 2008; Bhattacharya et al, 2011; Planar-Friedrich et al, 2012; Neidhardt et al, 2013; Radloff et al, this volume). Only for large perturbations induced by local pumping in the vicinity of a spatial gradient have larger variations in groundwater As concentrations been reported (McArthur et al, 2010; Jessen et al, 2012; Neidhardt et al, 2013). The muted response of As concentrations relative to other groundwater constituents reported in the present study over a period of two years is therefore consistent with previous findings.…”

Section: Discussionmentioning

confidence: 99%

Evidence of decoupling between arsenic and phosphate in shallow groundwater of Bangladesh and potential implications

Aziz

Bostick

Zheng

et al. 2017

Applied Geochemistry

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Reductive dissolution of iron oxyhydroxides and reduction of arsenic are often invoked as leading causes of high dissolved As levels in shallow groundwater of Bangladesh. The second of these assumptions is questioned here by comparing the behavior As and phosphate (P), a structural analogue for As (V) which also adsorbs strongly to Fe oxyhydroxides but is not subject to reduction. The first line of evidence is provided by a detailed groundwater time-series spanning two years for three wells in the 6–9 m depth range showing removal of As(III) from shallow groundwater during the monsoon without of loss of P. The data indicate a loss of ~90% of the dissolved As from groundwater in the intermediate well relative to a level of 3 μmol/L As predicted by conservative mixing between groundwater sampled from the shallower and the deeper well. In contrast, P concentrations of ~30 μmol/L in the intermediate well closely match the prediction from conservative mixing. Reduction therefore appears to inhibit the release of As to groundwater at this site relative to P instead of enhancing it. A re-analysis of existing groundwater As and P data from across the country provides a broader context for this finding and confirms that, without reduction, elevated concentrations of As would probably be even more widespread in shallow aquifers of Bangladesh. Without providing definite proof, X-ray absorption spectroscopy of sediment from the time-series site and elsewhere suggests that the loss of As from groundwater may be coupled to precipitation of As sulfide. Further study is needed to assess the implications of these observations for shallow aquifers that have been subjected to increased withdrawals for irrigation in recent decades.

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Section: Discussionmentioning

confidence: 99%

Evidence of decoupling between arsenic and phosphate in shallow groundwater of Bangladesh and potential implications

Aziz

Bostick

Zheng

et al. 2017

Applied Geochemistry

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“…Surface complexation modeling (SCM) techniques such as the charge distribution multi-site complexation (CD-MUSIC) [76,95,[98][99][100][101][102][103][104][105][106], the extended triple-layer model [107], isotherm modeling [108,109], and the ligand and charge distribution model (LCD) [110,111] have been used to model As species in solution and adsorbed to mineral surfaces. In general, SCM models use experimental data or quantum mechanics results such as equilibrium constants, bond lengths, and surface charges to calculate the adsorption isotherms of As on Fe mineral surfaces.…”

Section: Studying As Adsorption With Mathematical Modelsmentioning

confidence: 99%

Arsenic Adsorption onto Minerals: Connecting Experimental Observations with Density Functional Theory Calculations

2014

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A review of the literature about calculating the adsorption properties of arsenic onto mineral models using density functional theory (DFT) is presented. Furthermore, this work presents DFT results that show the effect of model charge, hydration, oxidation state, and DFT method on the structures and adsorption energies for As (oxyhydr)oxide cluster models were calculated using planewave and cluster-model DFT methods.

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“…Without retardation, attributable to As adsorption onto aquifer sands, the entire Pleistocene aquifer of Van Phuc would already be contaminated. The retardation is derived from several decades of perturbation and is at the low end of previous estimates by other methods, typically measured within days to weeks (17–22), and therefore predicts greater As mobility than most previous studies. The retardation measured in Van Phuc integrates the effect of competing ions typically present at higher concentrations in the Holocene aquifer (Fig.…”

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confidence: 99%

Retardation of arsenic transport through a Pleistocene aquifer

Geen

Bostick

Trang

et al. 2013

Nature

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147

120

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Groundwater drawn daily from shallow alluvial sands by millions of wells over large areas of South and Southeast Asia exposes an estimated population of over 100 million to toxic levels of arsenic (1). Holocene aquifers are the source of widespread arsenic poisoning across the region (2, 3). In contrast, Pleistocene sands deposited in this region more than ~12,000 years ago mostly do not host groundwater with high levels of arsenic. Pleistocene aquifers are increasingly used as a safe source of drinking water (4) and it is therefore important to understand under what conditions low levels of arsenic can be maintained. Here we reconstruct the initial phase of contamination of a Pleistocene aquifer near Hanoi, Vietnam. We demonstrate that changes in groundwater flow conditions and the redox state of the aquifer sands induced by groundwater pumping caused the lateral intrusion of arsenic contamination over 120 m from Holocene aquifer into a previously uncontaminated Pleistocene aquifer. We also find that arsenic adsorbs onto the aquifer sands and that there is a 16–20 fold retardation in the extent of the contamination relative to the reconstructed lateral movement of groundwater over the same period. Our findings suggest that arsenic contamination of Pleistocene aquifers in South and Southeast Asia as a consequence of increasing levels of groundwater pumping have been delayed by the retardation of arsenic transport.

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Surface complexation modeling of groundwater arsenic mobility: Results of a forced gradient experiment in a Red River flood plain aquifer, Vietnam

Cited by 52 publications

References 48 publications

Evidence of decoupling between arsenic and phosphate in shallow groundwater of Bangladesh and potential implications

Evidence of decoupling between arsenic and phosphate in shallow groundwater of Bangladesh and potential implications

Arsenic Adsorption onto Minerals: Connecting Experimental Observations with Density Functional Theory Calculations

Retardation of arsenic transport through a Pleistocene aquifer

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