| 1. |
- Mahanta, C., et al.
(författare)
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Evaluation of arsenic removal potential of few indigenous materials through batch study
- 2012
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Ingår i: Understanding the Geological and Medical Interface of Arsenic, As 2012 - 4th International Congress: Arsenic in the Environment. - : CRC Press. - 9780415637633 ; , s. 289-290
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Konferensbidrag (refereegranskat)abstract
- Adsorption potential and characteristics of the four different indigenous materials i.e. Naturally Oxidized Iron Scrap (NOIS) sand, red soil and murum, (a type of lateritic soil which is a mix of finer and coarser grained sized particle and available in some parts of eastern India; for experimental purpose the coarser particles were used) were investigated with different operating parameters like pH, contact time, temperature, adsorbent dose and initial arsenic concentration in batch mode. From the pH study, it was found that the adsorbents were efficient in adsorbing Arsenic (As) in acidic media. Adsorption kinetics of arsenic sorption on the selected adsorbents followed Lagergren pseudo second order reaction model. The thermodynamic study evaluated that the adsorption processes of all adsorbents were exothermic in nature. The experimental equilibrium data obtained were applied to several isotherm models. Results revealed that the Freundlich isotherm was the best-fit model. The maximum adsorption capacity (q m) was found to be highest for NOIS [156 %mu;g/g for As (III) and 245 %mu;g/g for As (V)]. The batch studies ensured that the NOIS can be used as a promising adsorbent for arsenic remediation in developing indigenous treatment technologies.
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| 2. |
- Mahanta, C., et al.
(författare)
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Geochemical evidences in the release processes of Arsenic into the groundwater in a part of Brahmaputra Floodplains
- 2012
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Ingår i: METALS AND RELATED SUBSTANCES IN DRINKING WATER. - : IWA PUBLISHING. ; , s. 268-271
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Konferensbidrag (refereegranskat)abstract
- To understand the sources and mobilization processes responsible for arsenic enrichment in groundwater in the Brahmaputra Basin where higher arsenic concentration have been reported, the geochemical features of the aquifer sediments were studied. Six boreholes were drilled near the tubewells (1 and 2) where aqueous arsenic concentration varies between 250 - 350 mu g/l. The soil sediment was collected at 3 m (10 ft) interval and it was drilled to the depth of 45 m (150 ft) which is the common depth of the tubewell installed in the study area. The bulk chemical studies on the sediments show that the pH of soils varies from 4.2 to 5.2 with a mean value of 4.75. The groundwater composition in the study area is of Na-HCO3-. The major anions HCO3- is likely from the decomposition of organic matter and originates from weathering of silicate and calcite minerals by atmospheric or respired CO2. Selective sequential extraction (SSE) method proposed by Wenzel et al., (2001) for extraction of arsenic from soil was used. Results of sequential extraction experiment show that solid-phase arsenic is present predominantly in the reducible fraction (Ext_5 and Ext_6), and residual fraction (Ext_7) contributes to highest fraction in many soil sediment. The major processes of arsenic mobilization probably linked to desorption of As from Fe oxides/oxyhydroxides and the reductive dissolution of Fe rich phases in the aquifers sediments under reducing and alkaline conditions.
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| 3. |
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| 4. |
- Mahanta, C., et al.
(författare)
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Hydrogeochemical controls on mobilization of arsenic in groundwater of a part of Brahmaputra river floodplain, India
- 2015
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Ingår i: Journal of Hydrology: Regional Studies. - : Elsevier BV. - 2214-5818.
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Tidskriftsartikel (refereegranskat)abstract
- Study region: Arsenic enriched groundwater regime within low-industrialized Brahmaputra floodplains in Assam, NE India. Study focus: We examined the origin, distribution and processes of As release by investigating the salient groundwater chemistry and subsurface sedimentological characteristics. Besides collection of groundwater samples from domestic and public water supply wells, sediment samples from boreholes were investigated for textural and colour linkages. New hydrological insights for the region: Arsenic concentrations above the WHO guideline value of 10. μg/L were present in 33 wells and above the previous Indian national drinking standard of 50. μg/L were present in 15 wells. The green-olive colour sediments were more likely to yield As-enriched groundwater. The supersaturation of groundwater with respect to Fe(II) minerals, such as siderite and vivianite, explained the poor correlation between dissolved As and Fe. The result reinforced the phenomenon of reductive dissolution of Fe(III) oxyhydroxides releasing As to groundwater. This study throws light on the processes and mechanisms involved with As release in groundwater. The homogenous floodplain terrain makes the hydrological As imprint unambiguous and the hydrogeological signatures untarnished. Considering the absence of anthropogenic sources in the study area, the conclusions on the nature and causes for As release to groundwater looked dependable although the final contamination at specific subsurface sites would be influenced by advection-dispersion of groundwater flow accompanied by retardation, ion exchange, surface complexation and possible biodegradation.
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| 5. |
- Mahanta, C., et al.
(författare)
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Preliminary assessment of arsenic distribution in brahmaputra river basin of India based on examination of 56,180 public groundwater wells
- 2015
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Ingår i: Safe and Sustainable Use of Arsenic-Contaminated Aquifers in the Gangetic Plain: A Multidisciplinary Approach. - Cham : Springer. - 9783319161242 ; , s. 57-64
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Arsenic (As) rich groundwater in alluvial aquifers is a worldwide problem (Nriagu JO, Bhattacharya P, Mukherjee AB, Bundschuh J, Zevenhoven R, Loeppert RH, Arsenic in soil and groundwater: an introduction. In: Bhattacharya P, Mukherjee AB, Bundschuh J, Zevenhoven R, Loeppert RH (eds) Arsenic in soil and groundwater environment: biogeochemical interactions, health effects and remediation. Trace metals and other contaminants in the environment, vol 9 (Ser Ed Nriagu JO). Elsevier, Amsterdam, 2007). Elevated arsenic concentrations have long been detected in Southeast Asia (e.g. Thailand, Myanmar, Vietnam, Cambodia and Lao), India, Bangladesh, China, Mongolia, Nepal and Pakistan (Smedley PL, Kinniburgh DG, Appl Geochem 17:517-568, 2002). Recent reports of discovery of arsenic (As) enrichment in groundwater of the Brahmaputra river basin (Bhattacharya P, Mukherjee A, Mukherjee AB, Arsenic contaminated groundwater of India. In: Nriagu J (ed) Encyclopedia of environmental health. Elsevier B.V, Amsterdam, 2011) has exposed a significantly large population inhabiting in the river valley to serious health threats, although the actual distribution and extent of the As affected groundwater in the aquifers are yet to be established. Because of its vicinity to the highly As rich groundwater regions of Bengal basin (Bangladesh and West Bengal state of India), the extent of the polluted areas within the Brahmaputra basin may be much wider than what is initially understood. Groundwater arsenic contamination in the Brahmaputra basin aquifers in Assam, a state in the northeastern part of India, has started gaining attention relatively recently. Singh (Arsenic contamination in groundwater of North Eastern India. In: Proceedings of 11th national symposium on hydrology with focal theme on water quality. National Institute of Hydrology, Roorkee, 2004) reported maximum groundwater arsenic concentrations in Jorhat district (Fig. 4.1), located in the southern bank of the Brahmaputra river in Assam (maximum groundwater As concentration ranges between 194 and 657 μg/L), with relatively lower concentrations in the northern bank like Lakhimpur district (50-550 μg/L). Based on studies conducted in Darrang and Bongaigaon districts located in the northern bank (Fig. 4.1) of the Brahmaputra river in Assam, Enmark and Nordborg (Arsenic in the groundwater of the Brahmaputra floodplains, Assam, India-Source, distribution and release, mechanisms. Retrieved from the url: www2.lwr.kth.se/Publikationer/PDF_Files/MFS_2007_131.pdf, 2007) reported the concentration of arsenic in the two districts between 5 and 606 μg/L. In a study conducted in 2010 (Mahanta C, Pathak N, Bhattacharya P, Enmark G, Nordborg D, Source, distribution and release mechanisms of arsenic in the groundwater of Assam floodplains of Northeast India. In: Proceedings of the World Environmental and Water Resources Congress sponsored by Environmental and Water Resources Institute (EWRI) of the American Society of Civil Engineers, 2008), concentrations beyond 50 μg/L have been confirmed in 72 blocks out of 214 blocks in 22 districts of Assam. A study by Chetia M, Chatterjee S, Banerjee S, Nath MJ, Singh D, Srivastava RB, Sarma HP (Environ Monit Assess 173:1393-1398, 2011) in the Golaghat district reported As concentration ranging between 1 and 128 μg/L in six blocks of the district. These studies so far have remained spatially limited and a comprehensive picture is yet to emerge. To comprehensively evaluate the extent of As contamination in the region, a blanket rapid assessment study was undertaken in large parts of the Brahmaputra basin in Assam. This paper reports the preliminary assessment of arsenic distribution in the Brahmaputra basin in Assam based upon results from 56,180 public groundwater wells, tested during the rapid assessment programme.
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| 6. |
- Mahanta, C., et al.
(författare)
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Source, distribution and release mechanisms of arsenic in the groundwater of Assam floodplains of Northeast India
- 2008
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Ingår i: World Environmental and Water Resources Congress 2008: Ahupua'a - Proceedings of the World Environmental and Water Resources Congress 2008. - Reston, VA : American Society of Civil Engineers. - 9780784409763
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Konferensbidrag (refereegranskat)abstract
- This study conducted in Bongaigaon and Darrang districts of Assam, India is based upon water chemistry and sediment characteristics investigation in an reportedly arsenic infested belt. Of total 50 sampled wells, 15 had arsenic concentration above national drinking water standard of 50 μg/l, and 33 had As concentrations above the WHO guideline of 10 μg/l. However no distinct zones or depths with specific sedimentological features could be identified. Sediments with colour on green-olive scale are probably more likely to bear As contaminated water than white sediments. Sand filters used to reduce high iron content seem to reduce As content of water effectively. Arsenic rich water is also partly avoided since drillers seek water low in iron, which is often also low in arsenic content. Reductive dissolution of Ferric hydroxides is believed to be the release mechanism controlling the mobility of arsenic, rather than oxidation of arsenopyrite or pH induced desorption.
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| 7. |
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| 8. |
- Verma, S., et al.
(författare)
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Solute chemistry and groundwater arsenic enrichment in southern part of Brahmaputra River Basin, India, adjacent to Indo-Burmese ranges
- 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. 62-63
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Konferensbidrag (refereegranskat)abstract
- The present study examines the groundwater chemistry, hydrogeochemical evolution and Arsenic (As) enrichment in shallow aquifers in the southern Brahmaputra river basin situated close to Naga-thrust belt. The major-ion composition dominated by a Na‒Ca‒HCO3 and Ca‒Na‒HCO3 hydro-chemical facies. Groundwater composition influenced by silicates weathering in S-region of Brahmaputra basin aquifers. The aquifers of S-region are severely contaminated with As (max 0.45 mg/L), nearly 92% collected groundwater sample are enriched with As. As show poor and negative correlation with various redox—sensitive solutes. It suggests that not a single process is controlling factor, although multiple biogeochemical mechanisms might influence As liberation and fate in groundwater of S-region. The geologic explanation for high arsenic in the southern region of Brahmaputra basin (upper Assam) is probably the crustal recycling of arsenic as an incompatible element during tectonic activity.
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