Geochemical and hydrogeological contrasts between shallow and deeper aquifers in two villages of Araihazar, Bangladesh: Implications for deeper aquifers as drinking water sources

Zheng, Yan; Geen, Alexander van; Stute, M.; Dhar, Ratan; Mo, Zhengyu; Cheng, Zhongqi; Horneman, A.; Gavrieli, Ittai; Simpson, H. J.; Versteeg, Roelof; Steckler, Michael S.; Grazioli-Venier, A.; Goodbred, S. L.; Mohammad, Shahnewaz; Shamsudduha, Mohammad; Hoque, M. A.; Ahmed, Kazi Matin

doi:10.1016/j.gca.2005.06.001

Cited by 175 publications

(188 citation statements)

References 37 publications

(65 reference statements)

Supporting

Mentioning

175

Contrasting

Unclassified

Order By: Relevance

“…5). In the case of deep aquifers, such decoupling is consistent with low concentrations of mobilizable As in deep aquifer sediment (Zheng et al, 2005). In such conditions, even if microbially-mediated reduction of Fe oxyhydroxides occurred, the release of Fe could be decoupled from As due to either re-adsorption or the lack of a pool of mobilizable As in the sediment .…”

Section: Decoupling Between Variations In Redox-sensitive Constituentmentioning

confidence: 63%

“…At all but Site B (Fig. 1c), these deep wells tapped sandy aquifers with a characteristic orangebrown color that is typically associated with low sediment As concentrations (Horneman et al, 2004;Zheng et al, 2005). At Sites A, C, E, F, and G, the redox potential (ORP) of groundwater was less negative than in shallow aquifers (Table 1).…”

Section: Deep Aquifersmentioning

confidence: 96%

“…1c). At Site B, grey Holocene sediments were observed even to a depth of 91 m (Zheng et al, 2005). At each site, one or several layers of fine-grained sediment separate the shallow aquifers that are elevated in As from the deep aquifers that are low in As concentration (Fig.…”

Section: Monitoring Wellsmentioning

confidence: 99%

“…Groundwater ages in deep aquifers at sites A and B are 10-1000 times higher than in the corresponding shallow aquifers of Araihazar (Zheng et al, 2005;Stute et al, 2007). Radiocarbon ages of dissolved inorganic carbon from wells C-53 m, F-58 m, and G-52 m were 10700 ± 55, 6240 ± 30, and 3620 ± 35 years, respectively (Dhar, 2006).…”

Section: Fluctuations In Major Ion Compositions and Groundwater Agementioning

confidence: 99%

“…These observations not only fill a gap in our understanding of temporal variability in groundwater As concentrations, they also shed new light on the mechanisms of As mobilization and may help us anticipate future trends in affected areas. The monitoring wells tap aquifers from 5-91 m with a wide range of As concentrations from <5 to 600 µg/L in an area where previous studies have documented a spectrum of hydrogeological conditions that is representative of much of the Bengal Basin (Horneman et al, 2004;Zheng et al, 2005;van Geen et al, 2006). We describe the main temporal patterns in groundwater chemistry, including long-term trends, short-term excursions, and seasonal variations in both shallow and deep aquifers.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Temporal variability of groundwater chemistry in shallow and deep aquifers of Araihazar, Bangladesh

Dhar

Zheng

Stute

et al. 2008

Journal of Contaminant Hydrology

Self Cite

111

View full text Add to dashboard Cite

Samples were collected every 2-4 weeks from a set of 37 monitoring wells over a period of 2-3 years in Araihazar, Bangladesh, to evaluate the temporal variability of groundwater composition for As and other constituents. The monitoring wells are grouped in 6 nests and span the 5-91 m depth range. Concentrations of As, Ca, Fe, K, Mg, Mn, Na, P, and S were measured by high-resolution ICPMS with a precision of 5% or better; concentrations of Cl were measured by ion chromatography. In shallow wells <30 m deep, As and P concentrations generally varied by <30%, whereas concentrations of the major ions (Na, K, Mg, Ca and Cl) and the redox-sensitive elements (Fe, Mn, and S) varied over time by up to ± 90%. In wells tapping the deeper aquifers > 30 m often below clay layers concentrations of groundwater As were much lower and varied by <10%. The concentrations of major cations also varied by <10% in these deep aquifers. In contrast, the concentration of redox-sensitive constituents Fe, S, and Mn in deep aquifers varied by up to 97% over time. Thus, strong decoupling between variations in As and Fe concentrations is evident in groundwaters from shallow and deep aquifers.Comparison of the time series data with groundwater ages determined by 3 H/ 3 He and 14 C dating shows that large seasonal or inter-annual variations in major cation and chloride concentrations are restricted to shallow aquifers and groundwater recharged < 5 years ago. There is no corresponding change in As concentrations despite having significant variations of redox sensitive constituents in these very young waters. This is attributed to chemical buffering due to rapid equilibrium between solute and solid As. At two sites where the As content of groundwater in existing shallow wells averages 102 µg/L (range: < 5 to 648 µg/L; n=118) and 272 µg/L (range: 10 to 485 µg/L; n=65), respectively, a systematic long-term decline in As concentrations lends support to the notion that flushing may slowly deplete an aquifer of As. Shallow aquifer water with > 5 yr 3 H/ 3 He age show a constant As:P molar ratio of 9.6 over time, suggesting common mechanism of mobilization.Corresponding author, Y. Zheng,

show abstract

Section: Decoupling Between Variations In Redox-sensitive Constituentmentioning

confidence: 63%

Section: Deep Aquifersmentioning

confidence: 96%

Section: Monitoring Wellsmentioning

confidence: 99%

Section: Fluctuations In Major Ion Compositions and Groundwater Agementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Temporal variability of groundwater chemistry in shallow and deep aquifers of Araihazar, Bangladesh

Dhar

Zheng

Stute

et al. 2008

Journal of Contaminant Hydrology

Self Cite

111

View full text Add to dashboard Cite

show abstract

A generalized regression model of arsenic variations in the shallow groundwater of Bangladesh

2015

View full text Add to dashboard Cite

Localized studies of arsenic (As) in Bangladesh have reached disparate conclusions regarding the impact of irrigation‐induced recharge on As concentrations in shallow (≤50 m below ground level) groundwater. We construct generalized regression models (GRMs) to describe observed spatial variations in As concentrations in shallow groundwater both (i) nationally, and (ii) regionally within Holocene deposits where As concentrations in groundwater are generally high (>10 μg L−1). At these scales, the GRMs reveal statistically significant inverse associations between observed As concentrations and two covariates: (1) hydraulic conductivity of the shallow aquifer and (2) net increase in mean recharge between predeveloped and developed groundwater‐fed irrigation periods. Further, the GRMs show that the spatial variation of groundwater As concentrations is well explained by not only surface geology but also statistical interactions (i.e., combined effects) between surface geology and mean groundwater recharge, thickness of surficial silt and clay, and well depth. Net increases in recharge result from intensive groundwater abstraction for irrigation, which induces additional recharge where it is enabled by a permeable surface geology. Collectively, these statistical associations indicate that irrigation‐induced recharge serves to flush mobile As from shallow groundwater.

show abstract

Recharge of low‐arsenic aquifers tapped by community wells in Araihazar, Bangladesh, inferred from environmental isotopes

Mihajlov

Stute

Schlosser

et al. 2016

Water Resources Research

Self Cite

View full text Add to dashboard Cite

More than 100,000 community wells have been installed in the 150–300 m depth range throughout Bangladesh over the past decade to provide low-arsenic drinking water (<10 μg/L As), but little is known about how aquifers tapped by these wells are recharged. Within a 25 km2 area of Bangladesh east of Dhaka, groundwater from 65 low-As wells in the 35–240 m depth range was sampled for tritium (3H), oxygen and hydrogen isotopes of water (18O/16O and 2H/1H), carbon isotope ratios in dissolved inorganic carbon (DIC, 14C/12C and 13C/12C), noble gases, and a suite of dissolved constituents, including major cations, anions, and trace elements. At shallow depths (<90 m), 24 out of 42 wells contain detectable 3H of up to 6 TU, indicating the presence of groundwater recharged within 60 years. Radiocarbon (14C) ages in DIC range from modern to 10 kyr. In the 90–240 m depth range, however, only 5 wells shallower than 150 m contain detectable 3H (<0.3 TU) and 14C ages of DIC cluster around 10 kyr. The radiogenic helium (4He) content in groundwater increases linearly across the entire range of 14C ages at a rate of 2.5×10−12 ccSTP 4He g−1 yr−1. Within the samples from depths >90 m, systematic relationships between 18O/16O, 2H/1H, 13C/12C and 14C/12C, and variations in noble gas temperatures, suggest that changes in monsoon intensity and vegetation cover occurred at the onset of the Holocene, when the sampled water was recharged. Thus, the deeper low-As aquifers remain relatively isolated from the shallow, high-As aquifer.

show abstract

Geochemical and hydrogeological contrasts between shallow and deeper aquifers in two villages of Araihazar, Bangladesh: Implications for deeper aquifers as drinking water sources

Cited by 175 publications

References 37 publications

Temporal variability of groundwater chemistry in shallow and deep aquifers of Araihazar, Bangladesh

Temporal variability of groundwater chemistry in shallow and deep aquifers of Araihazar, Bangladesh

A generalized regression model of arsenic variations in the shallow groundwater of Bangladesh

Recharge of low‐arsenic aquifers tapped by community wells in Araihazar, Bangladesh, inferred from environmental isotopes

Contact Info

Product

Resources

About