| 1. |
- Ghosh, Devanita, et al.
(author)
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Characterization and microbial utilization of dissolved lipid organic fraction in arsenic impacted aquifers (India)
- 2015
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In: Journal of Hydrology. - : Elsevier BV. - 0022-1694 .- 1879-2707. ; 527, s. 221-233
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Journal article (peer-reviewed)abstract
- The coupled role of organic matter (OM) and microbial activity is widely acknowledged in arsenic (As) biogeochemical cycling in sedimentary environments. However, little is known about OM characteristics particularly the dissolved fraction in the Bengal Delta Plain aquifers – one of the worst As impacted regions in the world. Ongoing investigations in As-rich aquifers in Nadia district (West Bengal, India) indicate presence of arsenite As(III) oxidizing bacterial communities in the Grey Sand Aquifers (GSA), but absent in Brown Sand Aquifers (BSA). In this study, we investigate the key differences in dissolved organic carbon (DOC) characteristics and its relationship with differences in elemental concentrations, distribution of biomarkers, and utilization of DOC by in situ microbial communities in BSA and GSA. We demonstrate a new approach using ENVI™ C-18 DSK discs to pre-concentrate DOC from large volumes of water, and further extract the OM and separate it into different lipid fractions using the solid phase extraction technique. The aquifers show marked heterogeneity in terms of their DOC characteristics and elemental profiles irrespective of their grey or brown color. DOC indicates variable inputs of terrestrial derived OM sources, and OM derived from decomposition and/or microbial cellular components. DOC in the aquifers consist of predominantly n-alkanoic acids (∌80%) followed by n-alkanes and n-alcohols. The GSAs indicate high iron (Fe) and manganese (Mn) concentrations, and presence of mature petroleum derived hydrocarbons in DOC. BSA has comparatively lower concentrations of Fe and Mn, and shows absence of mature hydrocarbons in DOC. Experiments in presence of indigenous bacteria from groundwater with DOC lipid extracts as the sole carbon source indicate higher growth in the GSA samples implying preferential use of DOC. The potential availability of DOC in these aquifers can influence the community composition of indigenous heterotrophic microbial flora, which in turn can affect elemental cycles including that of As.
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| 2. |
- Ghosh, Devanita, et al.
(author)
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Elemental and biomarker characteristics in a Pleistocene aquifer vulnerable to arsenic contamination in the Bengal Delta Plain, India
- 2015
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In: Applied Geochemistry. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0883-2927 .- 1872-9134. ; 61, s. 87-98
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Journal article (peer-reviewed)abstract
- An elevated level of arsenic (As) in the Indo-Gangetic delta plain aquifers has been reported since the 1990s. Organic matter (OM) present in groundwater and aquifer sediments supports the microbial communities in these aquifers. During installation of a drinking water well, 26 sediment intervals of 6 m each were retrieved up till 156 m from a Pleistocene brown sand aquifer (BSA). Grain size distribution, sequential extraction of metals and total extractable lipids were analyzed in each sample. These parameters were statistically correlated in order to establish relationship between the physical vs. inorganic and organic characteristics, and how these properties affected the distribution of As in BSAs. The aquifer sediments consisted of medium to coarse sand except the surface sediments and those at the bottom of the well, which had high clay and slit content. Arsenic (As) concentration in sediments ranged from 2 to 21 mg/kg and indicated a strong correlation with grain size. Arsenic was mostly associated with crystalline oxides and silicate-rich minerals. Arsenic showed significant correlation with Fe in all fractions, and suggests presence of pyrite bound As-bearing minerals in these sediments. The diagnostic sedimentary lipid biomarkers indicated presence of compounds derived from vascular plants and microbial cell wall. This inference was supported by various diagnostic lipid ratios. The biomarkers were abundant in surface and deeper layers, which had high clay and silt content. The BSA sediments indicated preferential preservation of n-alkanes over other functional compounds, which were more reactive and subject to degradation. The thick clay layer at 132-156 m contained visible plant fragments, and OM in this layer indicated preferential preservation of organic carbon most likely due to the absence of specific microbial communities that degraded these compounds and mobilized As. Statistical analyses indicated the influence of selective inorganic and organic components (As, Fe and fatty acids) controlling the co-distribution of various inorganic and organic components in the aquifer.
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| 3. |
- Shrivastava, Anamika, et al.
(author)
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Arsenic Contamination in Soil and Sediment in India : Sources, Effects, and Remediation
- 2015
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In: Current Pollution Reports. - : Springer. - 2198-6592. ; 1:1, s. 35-46
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Journal article (peer-reviewed)abstract
- Arsenic contamination is turning out to be a major problem these days with its area coverage and the number of people affected directly or indirectly. Now, the level of the contaminant has spread over the soil and sediments from groundwater and other natural sources. Arsenic poisoning in groundwater events is familiar to the world, but the consequences of soil contamination are still unrevealed to the community, specially the people of contaminated counties. Arsenic is a serious instantaneous concern for the people and other life forms regarding the poisoning through crops and vegetables. Many remediation technologies that mainly include physical, chemical, and a few biological methods have been evolved with time to check its effects. The physical and chemical methods for this purpose are often inefficient and/or very expensive, mainly limited to application in aqueous systems, and produce toxic sludge, which again becomes a matter of concern. But bioremediation relies on the fact that biological organisms have the ability to degrade, detoxify, and even accumulate harmful chemicals and offers attractive perspectives for biomonitoring (via biosensors), treatment of wastewater, and the recycling of polluted soils.
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