| 1. |
- Chatterjee, D., et al.
(författare)
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Groundwater arsenic in the fluvial Bengal plains : geochemistry and mitigation
- 2013
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Ingår i: PROCEEDINGS OF THE FOURTEENTH INTERNATIONAL SYMPOSIUM ON WATER-ROCK INTERACTION, WRI 14. - : ELSEVIER SCIENCE BV. ; , s. 143-146
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Konferensbidrag (refereegranskat)abstract
- The water quality and chemistry of the groundwater of the fluvial Bengal plains have been investigated. It has been found that shallow aquifers (< 50 m bgl) are contaminated in a few pockets, surrounded by areas with low arsenic (As)/As-free groundwater, while the deeper aquifer (> 100 m bgl) is generally free from As (< 10 mu g/L). It also reveals that multiple As mobilization processes are occurring simultaneously, rather than any single geochemical process. An attempt has been made to demonstrate the degree of As heterogeneity with groundwater quality, and this has been followed by a few local conditions. The study further suggests that the As distribution (spatio-vertical) helps to identify safe shallow aquifers, and several signatures (colour of the sediments /land use pattern/ geomorphological features /local recharge events) are apparent that can be useful for formulating long-term mitigation options.
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| 2. |
- Annaduzzaman, Md, et al.
(författare)
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Arsenic and manganese in shallow tubewells : validation of platform color as a screening tool in Bangladesh
- 2018
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Ingår i: Groundwater for Sustainable Development. - : Elsevier B.V.. - 2352-801X. ; 6, s. 181-188
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Tidskriftsartikel (refereegranskat)abstract
- This study aimed to evaluate the potential of handpump tubewell platform color as a low-cost, quick and convenient screening tool for As and Mn in drinking water tubewells. For this study, groundwater samples and corresponding tubewell platform pictures were collected from 272 shallow tubewells in Matlab Upazila of South-Eastern Bangladesh. The result shows that arsenic concentration within the surveyed (n = 272) tubewells, 99% (n = 269) exceeded the World Health Organization (WHO) guideline value of 10 µg/L, and 98% (n = 267) exceeded the Bangladesh drinking water standards (BDWS) of 50 µg/L. In relation to the platform color concept, within 233 (total 272) red colored platform tubewells, 230 (99%) exceeded the WHO guideline value of 10 µg/L, and 229 (98%) tubewells exceeded BDWS of 50 µg/L. This result shows a strong correlation between the development of red color stain on tubewell platform and As concentrations in the corresponding tubewell water. This study suggests that red-colored platform can be used for primary identification of tubewells with an elevated level of As and thus could prioritize sustainable As mitigation management in developing countries where water comes from reductive shallow aquifers. This study did not confirm the potential for Mn screening, as red discoloration by Fe oxides was found to mask the black discoloration of Mn oxides. It is recommended to further investigate this screening tool in regions with a higher well-to-well variability of As contaminations, as in the presented study As was found >10ug/L in 99% of the tubewells.
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| 3. |
- Annaduzzaman, Md., et al.
(författare)
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Tubewell platform color : A low-cost and rapid screening tool for arsenic and manganese in drinking water
- 2013
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Presence of high level of geogenic arsenic (As) in groundwater is one of the major and adverse drinking water quality problem all over the world, especially in Southeast Asia, where groundwater is the prominent drinking water source. Bangladesh is already considered as one of the most As affected territories, where As contamination in the groundwater is key environmental disasters. Recently besides As, presence of high level of manganese (Mn) in drinking water has also got attention due to its neurological effect on children. It becomes very essential to formulate a reliable safe drinking water management policy to reduce the health threat caused by drinking As and Mn contained groundwater. The development of a simple low cost technique for the determination of As and Mn in drinking water wells is an important step to formulate this policy. The aim of this study was to evaluate the potentiality of tubewell platform color as low-cost, quick and convenient screening tool for As and Mn in drinking water wells (n=272) in a highly arsenic affected area on Matlab, Southeastern Bangladesh.The result shows strong correlation between the development of red color stain on tubewell platform and As enrichment in the corresponding tubewell water compared to WHO drinking water guideline (10 μg/L) as well as Bangladesh drinking water standard (BDWS) (50 μg/L), with certainty values of 98.7% and 98.3% respectively. The sensitivity and efficiency of red colored platforms to screen high As water in tubewells are 98% and 97% respectively at 10 μg/L, whereas at cut-off level of 50μg/L both sensitivity and efficiency values are 98%. This study suggests that red colored platform could be potentially used for primary identification of tubewells with elevated level of As and thus could prioritise sustainable As mitigation management in developing countries. Due to lack of tubewells with black colored platform in the study area, the use of platform color concept for screening of Mn enriched water in the wells have not been tested significantly, which requires further study.Acknowledgements: This study was carried out with support from the Liuuaeus-Palme Academic Exchange Programme supported by International Programs Office (IPK) and the KTH led joint collaborative action research project on Sustainable Arsenic Mitigation- SASMIT (Sid Contribution 750000854).
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| 4. |
- Annaduzzaman, Md., et al.
(författare)
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Tubewell platform color as a screening tool for arsenic in shallow drinking water wells in Bangladesh
- 2016
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Ingår i: Arsenic Research and Global Sustainability - Proceedings of the 6th International Congress on Arsenic in the Environment, AS 2016. - : CRC Press/Balkema. - 9781138029415 ; , s. 632-633
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Konferensbidrag (refereegranskat)abstract
- The development of a simple and low cost technique for determination of arsenic (As) in drinking water wells is an urgent need to accelerate As mitigation policy. The aim of this study was to evaluate the potentiality of tubewell platform color as low-cost, quick and convenient screening tool for As. The result shows strong correlation between the development of red color stain on tubewells platform and As enrichment in the corresponding tubewells water compared to WHO (10 μg/L) and BDWS (50 μg/L), with 99% certainty. The red color stain in the platform indicates 98% sensitivity with WHO (10 μg/L) and BDWS (50 μg/L). With regard to WHO and BDWS, the corresponding efficiency of the platform color as screening tool for As are 97.3% and 97%. This study suggests that platform color can be potentially used for screening tubewells, help users switch to tube wells with low As and facilitate sustainable As mitigation efforts in developing countries.
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| 5. |
- Bhattacharya, Prosun, 1962-, et al.
(författare)
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Natural Arsenic in Coastal Groundwaters in the Bengal Delta Region in West Bengal, India
- 2010
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Ingår i: Management and Sustainable Development of Coastal Zone Environments. - Dordrecht : Springer Netherlands. - 9789048130672 ; , s. 146-160
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Bokkapitel (refereegranskat)abstract
- Bengal Delta region is currently confronted with largest groundwater arsenic calamity in history of human kind (BGS-DPHE, 2001; Mukherjee and Bhattacharya, 2001; Bhattacharya et al., 2002a; McArthur et al., 2001; Smedley and Kinniburgh, 2002; Mukherjee et al., 2006; Nath et al., 2005, 2007, 2008). Concentrations of arsenic in drinking water wells in the region often exceed the WHO drinking water guideline value (10 μg L-1) and the national safe limit of both India and Bangladesh for arsenic in drinking water (Smedley and Kinniburgh, 2002; RGNDWM, 2002; CGWB, 1999; Bhattacharya et al., 2002a). About one third (35 million) population inhabiting in this region (West Bengal and Bangladesh), currently at risk of long-term arsenic exposure (Bhattacharya et al., 2001; RGNDWM, 2002; Chakraborti et al., 2004; Kapaj et al., 2006), are being diagnosed with a wide spectrum of adverse health impacts including skin disorders such as hyper/hypo-pigmentation, keratosis and melanosis and are also in hot-spot areas of BDP which is reflected in a rise in the number of cancer cases (Guha Mazumdar et al., 1988). The distribution pattern of arsenic occurrence in BDP is patchy and there are numerous hotspots of arsenic contamination in the semi-confined shallow Holocene aquifer (Bhattacharya et al., 1997; Smedley and Kinniburgh, 2002). The scale of the problem is serious both in terms of hotspots and geographic area coverage (173 × 10 3 km2, eastern part of Hoogly-Bhagirathi/Western part of Ganga-Padma-lower Meghna flood plains).
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| 6. |
- Bhattacharya, Prosun, 1962-, et al.
(författare)
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Tubewell platform color : Assessment of a tool for rapid screening of arsenic and manganese in well water
- 2012
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Ingår i: UNDERSTANDING THE GEOLOGICAL AND MEDICAL INTERFACE OF ARSENIC, AS 2012. - : CRC PRESS-TAYLOR & FRANCIS GROUP. ; , s. 515-518
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Konferensbidrag (refereegranskat)abstract
- This study attempts to make a statistical comparison between Tubewell (TW) platform color and the level of Arsenic (As) and Manganese (Mn) concentration in groundwater abstracted from a set of 423 Tubewells (TWs) in Chakdaha Block of Nadia District, West Bengal, India to validate platform color as a screening tool for both As and Mn in groundwater. The results indicate that water extracted from TWs with black colored platform in 93% cases was safe for As while water extracted from TWs with red colored platform is contaminated with As with 38% certainty, compared to drinking water standard of India (50 mu g/L). At this standard the respective efficiency, sensitivity and specificity of the tool are 65, 85 and 59%. If WHO drinking water guideline (10 mu g/L) is considered, the certainty increases to 73% and 84% respectively for black and red colored platform with respective efficiency, sensitivity and specificity values of 79, 77 and 81%. Furthermore, the black colored platform with 78% certainty indicates well water is enriched with Manganese (Mn), while red colored platform indicates water is low in Mn with 64% certainty evaluated against Indian national standard of 300 mu g/L. This study demonstrates that platform color can be potentially used as an initial screening tool for As and Mn, to assess the safe water acess for drinking purposes.
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| 7. |
- Bhowmick, S., et al.
(författare)
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Arsenic mobilization in the aquifers of three physiographic settings of West Bengal, India : Understanding geogenic and anthropogenic influences
- 2013
-
Ingår i: Journal of Hazardous Materials. - : Elsevier BV. - 0304-3894 .- 1873-3336. ; 262, s. 915-923
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Tidskriftsartikel (refereegranskat)abstract
- A comparative hydrogeochemical study was carried out in West Bengal, India covering three physiographic regions, Debagram and Chakdaha located in the Bhagirathi-Hooghly alluvial plain and Baruipur in the delta front, to demonstrate the control of geogenic and anthropogenic influences on groundwater arsenic (As) mobilization. Groundwater samples (n=90) from tube wells were analyzed for different physico-chemical parameters. The low redox potential (Eh=-185 to -86mV) and dominant As(III) and Fe(II) concentrations are indicative of anoxic nature of the aquifer. The shallow (<100m) and deeper (>100m) aquifers of Bhagirathi-Hooghly alluvial plains as well as shallow aquifers of delta front are characterized by Ca2+HCO3 - type water, whereas Na+ and Cl- enrichment is found in the deeper aquifer of delta front. The equilibrium of groundwater with respect to carbonate minerals and their precipitation/dissolution seems to be controlling the overall groundwater chemistry. The low SO4 2- and high DOC, PO4 3- and HCO3 - concentrations in groundwater signify ongoing microbial mediated redox processes favoring As mobilization in the aquifer. The As release is influenced by both geogenic (i.e. geomorphology) and anthropogenic (i.e. unsewered sanitation) processes. Multiple geochemical processes, e.g., Fe-oxyhydroxides reduction and carbonate dissolution, are responsible for high As occurrence in groundwaters.
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| 8. |
- Biswas, Ashis, 1983-
(författare)
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Arsenic Geochemistry in the Alluvial Aquifers of West Bengal, India : Implications for targeting safe aquifers for sustainable drinking water supply
- 2013
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The natural occurrences of high (>10 μg/L) dissolved arsenic (As) in groundwater of Bengal Basin has put millions of people under the threat of chronic As exposure through drinking water. Present study has examined the processes that regulate As mobilization and its distribution in shallow aquifers and the potentiality of finding safe aquifers within shallow depth (<50 m) for drinking water supply. The results indicate that in terms of aquifer sediment colors and water quality two types of aquifer namely brown sand aquifer (BSA) and grey sand aquifer (GSA) can be distinguished within the depth, accessible by low-cost drilling. The redox condition in the BSA is delineated to be Mn oxyhydroxides reducing, not sufficiently lowered for As mobilization resulting in high Mn and low Fe and As in groundwater. While in GSA, currently the reductive dissolution of Fe oxyhydroxides is the prevailing redox process causing As mobilization into groundwater of this aquifer type. It is revealed that the vertical distribution of As and other aqueous redox parameters is related to the redox zonation within aquifer. The decoupling of As and Fe release into groundwater is evident in the shallowest part of aquifer because of Fe enrichment by weathering of silicate minerals especially of biotite, the precipitation of secondary mineral phases like siderite and vivianite and incomplete reduction of Fe oxyhydroxides. It is characterized that the seasonal variations of As and other aqueous solutes are limited within the upper portion of aquifer only (<30 m bgl) and can be related to seasonal cycling of redox status, aggregation and dispersion of As scavenging colloids, local groundwater abstraction and monsoonal recharge. The results of surface complexation modeling indicate that PO43- is the major competitor of As(III) and As(V) adsorption onto Fe oxyhydroxides. This study concludes that the reductive dissolution of Fe oxyhydroxides followed by competitive sorption reactions with the aquifer sediment is the process conducive for As enrichment in groundwater of Bengal Basin. Present study advocates that despite low concentration of As in groundwater, a rigorous assessment of attendant health risk for Mn is necessary prior to considering mass scale exploitation of the BSA for sustainable drinking water supply. This study also validates that TW platform colors can be used as a rapid screening tool for As and Mn in drinking water wells to prioritize As mitigation management.
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| 9. |
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| 10. |
- Biswas, Ashis, et al.
(författare)
-
Estimating the role of competing ions on the arsenic mobilization processes in the aquifers of Bengal Basin by surface complexation modeling
- 2013
-
Konferensbidrag (refereegranskat)abstract
- This study investigates the relative roles of the different competing ions on the arsenic (As) mobilization in the sedimentary aquifers of Bengal basin by surface complexation modeling of the temporal varaibility of As in shallow (<50 m) groundwater. Two sets of piezometers (2×5 = 10), installed at the two sites with relatively contrasting dissolved As concentration in groundwater, were monitored bi-weekly for As and other hydrogeochemical parameters over a period of 20 months. The estimation of the standard deviation (SD) for As(III) reflects strong temporal variation (SD ≥10 μg/L) in all the piezometers of two sites over the monitoring period. Particularly, the variation is more prominent in the shallowest part of the aquifer, where the site specific cyclic trends are evident. While, As(V) shows significant temporal variation in the piezometers of high As site only and no specific trend is reflected in the variation.Two different surface complexation models (SCMs), developed for ferrihydrite and goethite have been explored to account for the observed temporal variation in As(III) and As(V) concentrations. The SCM for ferrihydrite has provided the better estimation for both As(III) and As(V) variations.Among the different competing ions, PO43- appears as the major competitor of As(III) and As(V) adsorption onto ferrihydrite and the competition ability decreases in the order PO43- >> Fe(II) > H4SiO4 = HCO3-. It is further revealed that a small decrease in pH significantly increases the concentration of As(III) and decreases the As(V) concentration and vice versa. The present study suggests that the reductive dissolution of Fe oxyhydroxides alone cannot explain the observed high As concentration in groundwater of the sedimentary aquifers. Perhaps, the reductive dissolution of Fe oxyhydroxides followed by competitive sorption reactions with the aquifer sediment is the processes conducive for As enrichment in the groundwater of Bengal basin.
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| 11. |
- Biswas, Ashis, et al.
(författare)
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Groundwater chemistry and redox processes : Depth dependent arsenic release mechanism
- 2011
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Ingår i: APPLIED GEOCHEMISTRY. - : Elsevier BV. ; , s. 516-525
-
Konferensbidrag (refereegranskat)abstract
- Patchy occurrences of elevated As are often encountered in groundwater from the shallow aquifers (<50 m) of the Bengal Delta Plain (BDP). A clear understanding of various biogeochemical processes, responsible for As mobilization, is very important to explain this patchy occurrence and thus to mitigate the problem. The present study deals with the periodical monitoring of groundwater quality of five nested piezometeric wells between December 2008 and July 2009 to investigate the temporal changes in groundwater chemistry vis-a-vis the prevalent redox processes in the aquifer. Geochemical modeling has been carried out to identify key phases present in groundwater. A correlation study among different aqueous redox parameters has also been performed to evaluate prevailing redox processes in the aquifer. The long term monitoring of hydrochemical parameters in the multilevel wells together with hydrogeochemical equilibrium modeling has shown more subtle differences in the geochemical environment of the aquifer, which control the occurrence of high dissolved As in BDP groundwater. The groundwater is generally of Ca-HCO3 type. The dissolved As concentration in groundwater exceeded both WHO and National drinking water standard (Bureau of Indian Standards; BIS, 10 mu g L-1) throughout the sampling period. The speciation of As and Fe indicate persistent reducing conditions within the aquifer [As(III): 87-97% of As-T and Fe(II): 76-96% of Fe-T]. The concentration of major aqueous solutes is relatively high in the shallow aquifer (wells A and B) and gradually decreases with increasing depth in most cases. The calculation of SI indicates that groundwater in the shallow aquifer is also relatively more saturated with carbonate minerals. This suggests that carbonate mineral dissolution is possibly influencing the groundwater chemistry and thereby controlling the mobilization of As in the monitored shallow aquifer. Hydrogeochemical investigation further suggests that Fe and/or Mn oxyhydroxide reduction is the principal process of As release in groundwater from deeper screened piezometric wells. The positive correlations of U and V with As. Fe and Mn indicate redox processes responsible for mobilization of As in the deeper screened piezometric wells are possibly microbially mediated. Thus, the study advocates that mobilization of As is depth dependent and concentrations of As in groundwater depends on single/combined release mechanisms.
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| 12. |
- Biswas, Ashis, et al.
(författare)
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Hydrogeochemical contrast between brown and grey sand aquifers in shallow depth of Bengal Basin : consequences for sustainable drinking water supply
- 2012
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Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 431, s. 402-412
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Tidskriftsartikel (refereegranskat)abstract
- Delineation of safe aquifer(s) that can be targeted by cheap drilling technology for tubewell (TW) installation becomes highly imperative to ensure access to safe and sustainable drinking water sources for the arsenic (As) affected population in Bengal Basin. This study investigates the potentiality of brown sand aquifers (BSA) as a safe drinking water source by characterizing its hydrogeochemical contrast to grey sand aquifers (GSA) within shallow depth (<70 m) over an area of 100 km(2) in Chakdaha Block of Nadia district, West Bengal, India. The results indicate that despite close similarity in major ion composition, the redox condition is markedly different in groundwater of the two studied aquifers. The redox condition in the BSA is delineated to be Mn oxy-hydroxide reducing, not sufficiently lowered for As mobilization into groundwater. In contrast, the enrichments of NH4+, PO43-, Fe and As along with lower Eh in groundwater of GSA reflect reductive dis-solution of Fe oxy-hydroxide coupled to microbially mediated oxidation of organic matter as the prevailing redox process causing As mobilization into groundwater of this aquifer type. In some portions of GSA the redox status even has reached to the stage of SO42- reduction, which to some extent might sequester dissolved As from groundwater by co-precipitation with authigenic pyrite. Despite having low concentration of As in groundwater of the BSA the concentration of Mn often exceeds the drinking water guidelines, which warrants rigorous assessment of attendant health risk for Mn prior to considering mass scale exploitation of the BSA for possible sustainable drinking water supply.
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| 13. |
- Biswas, Ashis, et al.
(författare)
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Potentiality of shallow brown sand aquifers as an alternative safe drinking water source in Bengal Basin
- 2012
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Ingår i: Understanding the Geological and Medical Interface of Arsenic, As 2012 - 4th International Congress: Arsenic in the Environment. - 9780415637633 ; , s. 67-68
-
Konferensbidrag (refereegranskat)abstract
- The present study investigated the regional distribution of brown sand aquifers (BSA) as well as their hydrogeochemical contrast to grey sand aquifers (GSA). The data indicated that in BSA redox status is limited to the Mn oxides reduction stage, while in GSA, Fe oxides reduction to SO 4 2- reduction processes are prevalent. Though, the concentration of dissolved As was very low (<10 ÎŒg/L) in BSA, the concentration of Mn was very high (>400 ÎŒg/L). Whereas in GSA, the enrichment patterns of As and Mn were opposite to that of BSA. This study suggests that underlying health risk of Mn in drinking water needs to be addressed more rigorously before advocating for mass scale exploitation of BSA as an alternative drinking water source despite of significantly low As concentration in groundwater.
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| 14. |
- Biswas, Ashis, et al.
(författare)
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Role of competing ions in the mobilization of arsenic in groundwater of Bengal Basin : Insight from surface complexation modeling
- 2014
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Ingår i: Water Research. - : Elsevier. - 0043-1354 .- 1879-2448. ; 55, s. 30-39
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Tidskriftsartikel (refereegranskat)abstract
- This study assesses the role of competing ions in the mobilization of arsenic (As) by surface complexation modeling of the temporal variability of As in groundwater. The potential use of two different surface complexation models (SCMs), developed for ferrihydrite and goethite, has been explored to account for the temporal variation of As(III) and As(V) concentration, monitored in shallow groundwater of Bengal Basin over a period of 20 months. The SCM for ferrihydrite appears as the better predictor of the observed variation in both As(III) and As(V) concentrations in the study sites. It is estimated that among the competing ions, PO43- is the major competitor of As(III) and As(V) adsorption onto Fe oxyhydroxide, and the competition ability decreases in the order PO43- >> Fe(II) > H4SiO4 = HCO- (3.) It is further revealed that a small change in pH can also have a significant effect on the mobility of As(III) and As(V) in the aquifers. A decrease in pH increases the concentration of As(III), whereas it decreases the As(V) concentration and vice versa. The present study suggests that the reductive dissolution of Fe oxyhydroxide alone cannot explain the observed high As concentration in groundwater of the Bengal Basin. This study supports the view that the reductive dissolution of Fe oxyhydroxide followed by competitive sorption reactions with the aquifer sediment is the processes responsible for As enrichment in groundwater.
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| 15. |
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| 16. |
- Biswas, Ashis, et al.
(författare)
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Shallow hydrostratigraphy in an arsenic affected region of Bengal Basin : Implication for targeting safe aquifers for drinking water supply
- 2014
-
Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 485, s. 12-22
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Tidskriftsartikel (refereegranskat)abstract
- To delineate arsenic (As) safe aquifer(s) within shallow depth, the present study has investigated the shallow hydrostratigraphic framework over an area of 100 km(2) at Chakdaha Block of Nadia District, West Bengal. Drilling of 29 boreholes and subsequent hydrostratigraphic modeling has identified three types of aquifer within 50 m below ground level (bgl). Aquifer-1 represents a thick paleochannel sequence, deposited parallel to the River Hooghly and Ichamati. Aquifer-2 is formed locally within the overbank deposits in the central floodplain area and its vertical extension is strictly limited to 25 m bgl. Aquifer-3 is distributed underneath the overbank deposits and represents an interfluvial aquifer of the area. Aquifer-3 is of Pleistocene age (similar to 70 ka), while aquifer-1 and 2 represent the Holocene deposits (age <951 ka), indicating that there was a major hiatus in the sediment deposition after depositing the aquifer-3. Over the area, aquifer-3 is markedly separated from the overlying Holocene deposits by successive upward sequences of brown and olive to pale blue impervious clay layers. The groundwater quality is very much similar in aquifer-1 and 2, where the concentration of As and Fe very commonly exceeds 10 mu g/L and 5 mg/L, respectively. Based on similar sediment color, these two aquifers have jointly been designated as the gray sand aquifer (GSA), which constitutes 40% (1.84 x 10(9) m(3)) of the total drilled volume (4.65 x 10(9) m(3)). In aquifer-3, the concentration of As and Fe is very low, mostly <2 mu g/L and 1 mg/L, respectively. This aquifer has been designated as the brown sand aquifer (BSA) according to color of the aquifer materials and represents 10% (4.8 x 10(8) m(3)) of the total drilled volume. This study further documents that though the concentration of As is very low at BSA, the concentration of Mn often exceeds the drinking water guidelines.
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| 17. |
- Biswas, Ashis, et al.
(författare)
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Spatial, vertical and temporal variation of arsenic in shallow aquifers of the Bengal Basin : Controlling geochemical processes
- 2014
-
Ingår i: Chemical Geology. - : Elsevier BV. - 0009-2541 .- 1872-6836. ; 387, s. 157-169
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Tidskriftsartikel (refereegranskat)abstract
- A detailed understanding of the geochemical processes that regulate the spatial, temporal and vertical variation of dissolved arsenic (As) in shallow aquifers (<50 m) is a prerequisite for sustainable drinking water management in the Bengal Basin. The present study conducted at Chakdaha Block of the Nadia District, West Bengal, India, combined a high resolution hydrogeochemical monitoring study over 20 months from two sets of piezometers (2 x 5) to the sediment geochemistry at areas with high (average:146 mu g/L, n = 5) and relatively low (average: 53.3 mu g/L, n = 10) dissolved As concentrations in groundwater. The determination of the isotopic composition of delta H-2 and delta O-18 in groundwater of the two sites indicated the recharge of evaporative surface water to the aquifer. The concentrations of major aqueous solutes (Ca2+, Mg2+, Na+, K+, HCO3- and Cl-) and electrical conductivity were considerably higher in wells at the high As site compared to the low As site. Additionally, at the high As site, the major ions, Fe, SO42-, electrical conductivity, delta H-2 and delta O-18 showed markedly greater enrichment in the shallowest part (<24 m) of the aquifer compared to the deeper part, reflecting vertical layering of groundwater composition within the aquifer. The oxidation of pyrites has been attributed to the high rate of mineral dissolution resulting in such greater enrichments in this part of the aquifer. In addition, the anthropogenic input with recharge water possibly increased the concentrations of Cl- in this part of the aquifer. The vertical layering of groundwater was absent in the aquifer at the low As site. The absence of such layering and relatively low major ion concentrations and electrical conductivity could be linked to the enhanced aquifer flushing and decreased water-ediment interactions influenced by local-scale groundwater abstraction. The seasonal variations of As concentrations in groundwater were observed only in the shallowest part of the aquifers (<30 m). Furthermore, the As concentrations in groundwater at the uppermost part of the shallow aquifers (<21 m) increased continuously over the monitoring period at both sites. This study supports the view that the reductive dissolution of Fe oxyhydroxides coupled with competitive PO43- sorption reactions in the aquifer sediment enriches As in groundwater of the Bengal Basin. However, the additional Fe released by the weathering of silicate minerals, especially biotite, or the precipitation of Fe as secondary mineral phases such as siderite, vivianite and acid volatile sulfides may result in the decoupling of As and Fe enrichment in groundwater. The redox zonation within the aquifer possibly regulates the vertical distribution of As in the groundwater.
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| 18. |
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| 19. |
- Biswas, Ashis, et al.
(författare)
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Surface complexation modeling of temporal variability of arsenic in groundwater : Estimating the role of competing ions in the mobilization processes
- 2013
-
Konferensbidrag (refereegranskat)abstract
- This study investigates the relative roles of different competing ions on the mobilization of arsenic (As) by surface complexation modeling of As rich groundwater in the aquifer of Bengal Basin. Two sets of piezometers, installed at different depths of the shallow aquifer (<50 m), have been monitored for As and other relevant hydrogeochemical parameters over a period of 20 months. The potentiality of two different surface complexation models (SCM), developed for ferrihydrite and goethite has been explored to account for the observed temporal variation in As(III) and As(V) concentration in groundwater. The SCM for ferrihydrite appears as the better predictor for the observed variation in both As(III) and As(V) concentration. It is estimated that among the competing ions PO43- is the major competitor of As(III) and As(V) adsorption into Fe oxyhydroxide and competing ability of the ions decreases as PO43- >> Fe(II) > H4SiO4 = HCO3-. The result of sensitivity test indicates that the competition of PO43- with As for the adsorption sites might already reach nearly to the stage of maxima. It is also shown that a slight increase or decrease in pH can have overwhelming effect on the mobility of As(III) and As(V) by changing their concentration oppositely. It appears that only the reductive dissolution of Fe oxyhydroxide cannot explain the observed high As concentration in the groundwater of Bengal Basin. In absence of potential competition for the adsorption sites, As released due to reductive dissolution of Fe oxyhydroxide would have been re-adsorbed into the residual Fe phases. This study suggests that the reductive dissolution of Fe oxyhydroxide followed by competitive ion exchange with the aquifer sediment is the processes conducive for As enrichment in groundwater of the sedimentary aquifers.
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| 20. |
- Biswas, Ashis, et al.
(författare)
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Testing tubewell platform color as a rapid screening tool for arsenic and manganese in drinking water wells
- 2012
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 46, s. 434-440
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Tidskriftsartikel (refereegranskat)abstract
- A low-cost rapid screening tool for arsenic (As) and manganese (Mn) in groundwater is urgently needed to formulate mitigation policies for sustainable drinking water supply. This study attempts to make statistical comparison between tubewell (TW)platform color and the level of As and Mn concentration in groundwater extracted from the respective TW (n = 423), to validate platform color as a screening tool for As andMnin groundwater. The result shows that a black colored platform with 73% certainty indicates that well water is safe fromAs, while with 84% certainty a red colored platform indicates that well water is enriched with As, compared to WHO drinking waterguideline of 10 μg/L. With this guideline the efficiency, sensitivity, and specificity of the tool are 79%, 77%, and 81%, respectively.However, the certainty values become 93% and 38%, respectively, for black and redcolored platforms at 50 μg/L, the drinking water standards for India and Bangladesh. The respective efficiency, sensitivity, and specificity are 65%, 85%, and 59%. Similarly for Mn, black and red colored platform with 78% and 64% certainty, respectively, indicates that wellwater is either enriched or free from Mn at the Indian national drinking water standard of 300 μg/L. With this guideline the efficiency, sensitivity, and specificity of the tool are 71%, 67%, and 76%, respectively. Thus, this study demonstrates that TWplatform color can bepotentially used as an initial screening tool for identifying TWs with elevated dissolved As andMn, tomake further rigorous groundwater testing more intensive and implement mitigation options for safe drinking water supplies.
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| 21. |
- Chatterjee, Debashis, et al.
(författare)
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Assessment of arsenic exposure from groundwater and rice in Bengal Delta Region, West Bengal, India
- 2010
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Ingår i: Water Research. - : Elsevier BV. - 0043-1354 .- 1879-2448. ; 44:19, s. 5803-5812
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Tidskriftsartikel (refereegranskat)abstract
- Arsenic (As) induced identifiable health outcomes are now spreading across Indian subcontinent with continuous discovery of high As concentrations in groundwater. This study deals with groundwater hydrochemistry vis-a-vis As exposure assessment among rural population in Chakdaha block, West Bengal, India. The water quality survey reveals that 96% of the tubewells exceed WHO guideline value (10 mu g/L of As). The groundwaters are generally anoxic (-283 to -22 mV) with circum-neutral pH (6.3 to 7.8). The hydrochemistry is dominated by HCO3- (208 to 440 mg/L), Ca2+ (79 to 178 mg/L) and Mg2+ (17 to 45 mg/L) ions along with high concentrations of As-T (As total, below detection limit to 0.29 mg/L), Fe-T (Fe total, 1.2 to 16 mg/L), and Fe(II) (0.74 to 16 mg/L). The result demonstrates that Fe(II)-Fe(III) cycling is the dominant process for the release of As from aquifer sediments to groundwater (and vice versa), which is mainly controlled by the local biogeochemical conditions. The exposure scenario reveals that the consumption of groundwater and rice are the major pathways of As accumulation in human body, which is explained by the dietary habit of the surveyed population. Finally, regular awareness campaign is essential as part of the management and prevention of health outcomes. (c) 2010 Elsevier Ltd. All rights reserved.
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| 22. |
- Halder, Dipti, et al.
(författare)
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Arsenic exposure and health risk from consumption of brown rice in rural Bengal, India
- 2012
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Ingår i: Understanding the Geological and Medical Interface of Arsenic, As 2012 - 4th International Congress: Arsenic in the Environment. - : Taylor & Francis Group. - 9780415637633 ; , s. 505-507
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Konferensbidrag (refereegranskat)abstract
- This study investigates the Arsenic (As) concentration in different types of brown rice grain and assesses As exposure and non-cancer health risk from rice consumption. Daily Intake (DI rice) and Hazard Quotient (HQ) from rice were calculated for the people who are consuming these type of rice. Daily intake value of As from rice was compared with previous WHO recommended Provisional Tolerable Daily Intake value (PTDI) of 2.1 ÎŒg/day/kg bw to understand which kind of rice may pose potential health risk. Hazard quotient (HQ) was determined to understand the potential non-cancer health risk of the people who are consuming these rice. This study indicates that for SB brown rice consumer in 29% cases DI rice exceeds the previous PTDI value and 100% cases HQ value exceeds 1.
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| 23. |
- Halder, Dipti, et al.
(författare)
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Arsenic species in raw and cooked rice : Implications for human health in rural Bengal
- 2014
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Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 497, s. 200-208
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Tidskriftsartikel (refereegranskat)abstract
- This study compares the concentrations of total and different species of arsenic (As) in 29 pairs of raw and cooked rice samples collected from households in an area of West Bengal affected by endemic arsenicism. The aim is to investigate the effects of indigenous cooking practice of the rural villagers on As accumulation and speciation in cooked rice. It is found that inorganic As is the predominant species in both raw (93.8%) and cooked rice (88.1%). Cooking of rice with water low in As (<10 mu g L-1) significantly decreases the total and inorganic As content in cooked rice compared to raw rice. Arsenic concentration is mainly decreased during boiling of rice grains with excess water. Washing of rice grains with low As water has negligible effect on grain As concentration. The study suggests that rice cooking with low As water by the villagers is a beneficial risk reduction strategy. Despite reductions in As content in cooked rice because of cooking with low As water, the consumption of cooked rice represents a significant health threat (in terms of chronic As toxicity) to the study population.
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| 24. |
- Halder, Dipti, et al.
(författare)
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Assessment of arsenic exposure risk from drinking water and dietary component in West Bengal, India
- 2013
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Konferensbidrag (refereegranskat)abstract
- The current status of arsenic (As) exposure risk from drinking water and different dietary components in rural Bengal has been compared in the present study. This study shows that the consumption of rice is the major source of dietary intake of inorganic As among the population when they are drinking As safe water. Consumption of vegetables does not pose a significant health threat to the population independently; it nevertheless can increase the total daily intake of inorganic As (TDI-iAs). The results indicate that when people are drinking water with As concentration <10 μg L-1, in 35% of the cases the total daily intake of inorganic As (TDI-iAs) exceeds the previous provisional tolerable daily intake (PTDI) value of 2.1 μg day-1 kg-1 BW, recommended by World Health Organization (WHO). It should be mention here that the joint FAO/WHO expert committee on food additives (JECFA) has withdrawn the previous PTDI value in their 72nd meeting because PTDI value was in the lower range of bench mark dose level for 0.5% increased of lung cancer. However, Codex Committee on Contaminants in Foods (CCCF) has argued that TDI-iAs below BMDL0.5 does not indicates that there is no risk and this motivated us to compare TDI-iAs of the participants with the previous PTDI value of 2.1 μg day-1 kg-1 bw. At the As concentration level <10 μg L-1in drinking water, the consumption of rice is the major source of daily intake of inorganic As. When As concentration in drinking water exceeds 10 μg L-1, drinking water and rice consumption contributes almost equally (~40% from rice, ~50% from drinking water, and 10% from vegetables according to median DI-iAs) and TDI-iAs exceeds previous PTDI for all the participants. The relative contribution of daily intake of iAs from drinking water (DI-iAs-DW) largely predominates over daily intake of iAs from rice (DI-iAs-R) when As concentration in drinking water exceeds 50 μg L-1. This study implies that when consumption of rice contributes significantly to the TDI-iAs, supply of drinking water to the population considering national drinking water standard of India and Bangladesh as a safety measure for As might compound the As exposure largely by increasing TDI-iAs. Thus it can be concluded that any effort to mitigate the As poisoning of rural villagers in Bengal must look beyond the drinking water and consider all the routes of exposure.
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| 25. |
- Halder, Dipti, et al.
(författare)
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Consumption of Brown Rice : A Potential Pathway for Arsenic Exposure in Rural Bengal
- 2012
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 46:7, s. 4142-4148
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Tidskriftsartikel (refereegranskat)abstract
- This study assesses the arsenic (As) accumulation in different varieties of rice grain, that people in rural Bengal mostly prefer for daily consumption, to estimate the potential risk of dietary As exposure through rice intake. The rice samples have been classified according to their average length (L) and L to breadth (B) ratio into four categories, such as short-bold (SB), medium-slender (MS), long-slender (LS), and extra-long slender (ELS). The brown colored rice samples fall into the SB, MS, or LS categories; while all Indian Basmati (white colored) are classified as ELS. The study indicates that the average accumulation of As in rice grain increases with a decrease of grain size (ELS: 0.04; LS: 0.10; MS: 0.16; and SB: 0.33 mg kg(-1)), however people living in the rural villages mostly prefer brown colored SB type of rice because of its lower cost. For the participants consuming SB type of brown rice, the total daily intake of inorganic As (TDI-iAs) in 29% of the cases exceeds the previous WHO recommended provisional tolerable daily intake value (2.1 mu g day(-1) kg(-1) BW), and in more than 90% of cases, the As content in the drinking water equivalent to the inorganic As intake from rice consumption (C-W,C-eqv) exceeds the WHO drinking water guideline of 10 mu g L-1. This study further demonstrates that participants in age groups 18-30 and 51-65 yrs are the most vulnerable to the potential health threat of dietary As exposure compared to participants of age group 31-50 yrs, because of higher amounts of brown rice consumption patterns and lower BMI.
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| 26. |
- Halder, Dipti, et al.
(författare)
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Risk of arsenic exposure from drinking water and dietary components : Implications for risk management in rural Bengal
- 2013
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 47:2, s. 1120-1127
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Tidskriftsartikel (refereegranskat)abstract
- This study investigates the risk of arsenic (As) exposure to the communities in rural Bengal, even when they have been supplied with As safe drinking water. The estimates of exposure via dietary and drinking water routes show that, when people are consuming water with an As concentration of less than 10 μg L-1, the total daily intake of inorganic As (TDI-iAs) exceeds the previous provisional tolerable daily intake (PTDI) value of 2.1 μg day-1 kg-1 BW, recommended by the World Health Organization (WHO) in 35% of the cases due to consumption of rice. When the level of As concentration in drinking water is above 10 μg L-1, the TDI-iAs exceeds the previous PTDI for all the participants. These results imply that, when rice consumption is a significant contributor to the TDI-iAs, supplying water with an As concentration at the current national drinking water standard for India and Bangladesh would place many people above the safety threshold of PTDI. We also found that the consumption of vegetables in rural Bengal does not pose a significant health threat to the population independently. This study suggests that any effort to mitigate the As exposure of the villagers in Bengal must consider the risk of As exposure from rice consumption together with drinking water.
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| 27. |
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| 28. |
- Neidhardt, H., et al.
(författare)
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Influences of groundwater extraction on the distribution of dissolved As in shallow aquifers of West Bengal, India
- 2013
-
Ingår i: Journal of Hazardous Materials. - : Elsevier BV. - 0304-3894 .- 1873-3336. ; 262, s. 941-950
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Tidskriftsartikel (refereegranskat)abstract
- Here we report temporal changes of As concentrations in shallow groundwater of the Bengal Delta Plain (BDP). Observed fluctuations are primarily induced by seasonally occurring groundwater movement, but can also be connected to anthropogenic groundwater extraction. Between December 2009 and July 2010, pronounced variations in the groundwater hydrochemistry were recorded in groundwater samples of a shallow monitoring well tapping the aquifer in 22-25m depth, where Astot concentrations increased within weeks from 100 to 315μgL-1. These trends are attributed to a vertically shift of the hydrochemically stratified water column at the beginning of the monsoon season. This naturally occurring effect can be additionally superimposed by groundwater extraction, as demonstrated on a local scale by an in situ experiment simulating extensive groundwater withdrawal during the dry post-monsoon season. Results of this experiment suggest that groundwater extraction promoted an enduring change within the distribution of dissolved As in the local aquifer. Presented outcomes contribute to the discussion of anthropogenic pumping influences that endanger the limited and yet arsenic-free groundwater resources of the BDP.
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| 29. |
- Neidhardt, H., et al.
(författare)
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Organic carbon induced mobilization of iron and manganese in a West Bengal aquifer and the muted response of groundwater arsenic concentrations
- 2014
-
Ingår i: Chemical Geology. - : Elsevier BV. - 0009-2541 .- 1872-6836. ; 367, s. 51-62
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Tidskriftsartikel (refereegranskat)abstract
- The exact circumstances that cause the widespread enrichment of Mn and As in groundwater of the Bengal Delta Plain (BDP) and many other Asian delta areas still remain a matter of debate in the scientific community. We conducted an in situ field experiment in the central BDP region to investigate the influence of organic matter on the mobility of Fe, Mn and As in shallow aquifers. The groundwater at our study site was initially characterized by a circum-neutral pH, low concentrations of O2, NO3 - and SO4 2-, and increased Fe, Mn and As concentrations, reflecting reducing conditions in the aquifer. Since organic matter controls microbially mediated redox processes which are believed to result in the mobilization of Fe, Mn and As from Holocene aquifer sediments, an easily degradable carbon source (sucrose) was introduced into a shallow aquifer via four nested monitoring wells and distributed by circular pumping. Initial sucrose concentrations reached up to 2.55mM in the local groundwater and induced a strong increase in the activity of indigenous microbes that decomposed the sucrose within the following 14days stepwise into intermediate catabolic products (e.g., acetic acid), and finally to CO2/HCO3 -. The formation of organic acids was accompanied by a temporary decline in the pH and the redox potential, as well as an increase in the concentration of most major and trace elements in the groundwater by several times. While Mn concentrations rose up to 81.3μM (representing a 7.5 fold increase), Fe (on average 96.7% Fe(II)) concentrations reached a considerable transient maximum of 1390μM, which was 36 times higher than the initial baseline value. The most significant observation of this experiment is that the relative increments of dissolved As (on average 95.8% As(III)) reached between 19 and 49% only, which is in clear contrast to the pronounced mobilization of Fe, Mn and other trace elements. Changes in the groundwater composition during the experiment imply that the mobilization of Fe and Mn was primarily caused by a reductive dissolution of Mn-oxides and Fe-(oxyhydr)oxides, resulting from the stimulation of indigenous bacteria by the addition sucrose. In this context, the release of As can be attributed to the dissolution of Fe-(oxyhydr)oxides, which constitute the principal source of As in the aquifer sediments according to mineralogical and geochemical analyses. In contrast to the pronounced mobilization of Fe, the response of groundwater arsenic concentrations appeared to be muted, as indicated by subsequently declining As to Fe mol ratios that dropped one order in magnitude. The remarkable decoupling of As from Fe mobilization indicates that the aquifer sediments were apparently capable of compensating for the additional release of As. We attribute this As buffer potential to remaining Fe-minerals and potentially newly formed Fe(II)- and mixed Fe(II/III)-mineral phases, which were able to readily immobilize dissolved As. Sequential extraction results of the initial aquifer sediments further support this interpretation, revealing that up to 85% of the total As in the sediments was already present in adsorbed form, with Fe-minerals as principal hosts. Hence, the experimental data implies that a biogeochemically controlled environment of competing As release and retention arose after the addition of sucrose, where Fe-mineral phases played a key role in buffering the release of As. We further conclude that organic carbon limited aquifer systems in the BDP with increased As concentrations in groundwater may exhibit an unexpected buffer potential towards an additional As release, even when vast amounts of easily degradable organic carbon are introduced into the system.
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| 30. |
- Neidhardt, H., et al.
(författare)
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Reconstructing the sedimentation history of the Bengal Delta Plain by means of geochemical and stable isotopic data
- 2013
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Ingår i: Applied Geochemistry. - : Elsevier BV. - 0883-2927 .- 1872-9134. ; 36, s. 70-82
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of this study is to examine the sedimentation history of the central floodplain area of the Bengal Delta Plain in West Bengal, India. Sediments from two boreholes were analyzed regarding lithology, geochemistry and the stable isotopic composition of embedded organic matter. Different lithofacies were distinguished that reflect frequent changes in the prevailing sedimentary depositional environment of the study area. The lowest facies comprises poorly sorted fluvial sediments composed of fine gravel to clay pointing at high transport energy and intense relocation processes. This facies is considered to belong to an early Holocene lowstand systems tract that followed the last glacial maximum. Fine to medium sands above it mark a gradual change towards a transgressive systems tract. Upwards increasing proportions of silt and the stable isotopic composition of embedded organic matter both indicate a gradual change from fluvial channel infill sediments towards more estuarine and marine influenced deposits. Youngest sediments are composed of clayey and silty overbank deposits of the Hooghly River that have formed a vast low-relief delta-floodplain. Close to the surface, small concretions of secondary Mn-oxides and Fe-(oxyhydr) oxides occur and mark the fluctuation range of the unsaturated zone. These concretions are accompanied by relatively high contents of trace elements such as Zn, Ni, Cu, and As. To sum up, the outcomes of this study provide new insights into the complex sedimentation history of the barely investigated central floodplain area of West Bengal.
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| 31. |
- Zhu, Geyunjian H., et al.
(författare)
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Feasibility of Coacervate-Like Nanostructure for Instant Drug Nanoformulation
- 2023
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Ingår i: ACS Applied Materials and Interfaces. - : AMER CHEMICAL SOC. - 1944-8244 .- 1944-8252. ; 15:14, s. 17485-17494
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Tidskriftsartikel (refereegranskat)abstract
- Despite the enormous advancements in nanomedicine research, a limited number of nanoformulations are available on the market, and few have been translated to clinics. An easily scalable, sustainable, and cost-effective manufacturing strategy and long-term stability for storage are crucial for successful translation. Here, we report a system and method to instantly formulate NF achieved with a nanoscale polyelectrolyte coacervate-like system, consisting of anionic pseudopeptide poly(L-lysine isophthalamide) derivatives, polyethylenimine, and doxorubicin (Dox) via simple "mix-and-go" addition of precursor solutions in seconds. The coacervate-like nanosystem shows enhanced intracellular delivery of Dox to patient-derived multidrug-resistant (MDR) cells in 3D tumor spheroids. The results demonstrate the feasibility of an instant drug formulation using a coacervate-like nanosystem. We envisage that this technique can be widely utilized in the nanomedicine field to bypass the special requirement of large-scale production and elongated shelf life of nanomaterials.
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