Influence of monsoonal recharge on arsenic and dissolved organic matter in the Holocene and Pleistocene aquifers of the Bengal Basin

Kulkarni, Harshad Vijay; Mladenov, Natalie; Datta, Saugata; Chatterjee, Debashis

doi:10.1016/j.scitotenv.2018.05.009

Cited by 58 publications

(17 citation statements)

References 85 publications

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“…The five highly similar pairs include samples from drinking water (Shutova et al 2014), wetlands (Yamashita et al 2010), and Japan Sea (Tanaka et al 2014). Match-ups for components C 400 and C 310 are also found in 58 and 27 previous studies, respectively, from both natural waters (Yamashita et al 2010;Tanaka et al 2014;Kulkarni et al 2018) and wastewaters/drinking waters (Shutova et al 2014). However, both components did not seem to exhibit a high matchup (i.e., TCC ex,em > 0.99) with any previous reported components in the OpenFluor database.…”

Section: Major Fluorescent Dom Components Derived From Eem-parafac Analysissupporting

confidence: 72%

Dynamic changes in size‐fractionated dissolved organic matter composition in a seasonally ice‐covered Arctic River

Lin

Cai

et al. 2021

Limnology & Oceanography

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Arctic rivers are sensitive to climate and environmental change, but the biogeochemical response remains poorly understood. Monthly size-fractionated dissolved organic matter (DOM) samples from the lower Yukon River were characterized using UV-visible, fluorescence, and Fourier transform-infrared (FT-IR) spectroscopy techniques. The EEM-PARAFAC analysis revealed three major fluorescent DOM components, including two humic-like components (C 480 and C 400 ) and one protein-like component (C 310 ), with their relative importance following the order of C 480 ≥ C 400 > C 310 in the high-molecular-weight DOM (1 kDa-0.4 μm) and C 400 > C 480 > C 310 in the low-molecular-weight DOM pool (< 1 kDa). Transformation in DOM and change in sources were manifested in major fluorescent components and optical properties, including biological index (BIX), humification index (HIX), spectral slope (S 275-295 ) and specific UV absorbance at 254 nm (SUVA 254 ). These changes occurred within different DOM size-fractions and among ice-covered, spring freshet, and open seasons. Joint analysis of EEM and FT-IR spectra using a data fusion technique showed that humic-like DOM is mostly associated with C─H, C═C, and C─O bonds, while protein-like DOM is correlated more with C─N and N─H related structures. DOM aromaticity and the ratios of HIX to BIX and protein-like to humic-like components may be used as a compelling proxy to measure change in source waters and to infer permafrost dynamics. Our results provide insight into the seasonal variation in DOM composition for different size-fractions in the lower Yukon River, and a baseline dataset against which future changes can be understood in the context of arctic basin biogeochemical cycling.

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Section: Major Fluorescent Dom Components Derived From Eem-parafac Analysissupporting

confidence: 72%

Dynamic changes in size‐fractionated dissolved organic matter composition in a seasonally ice‐covered Arctic River

Lin

Cai

et al. 2021

Limnology & Oceanography

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“…Most notable were the spectral properties of component 1 at ex max 255–260 nm and em max at 448–480 nm are humic-like signatures found in forested systems and matched C2 from [80, 67]. Component 2 with spectral properties of Ex325/Em396 nm was compared to C6 from [81], C2 from [75] and C2 from [76] to an extent. This fluorescence signature is often referred to as the “M Peak” and is ubiquitous in a wide range of environments [68, 69].…”

Section: Resultsmentioning

confidence: 99%

DOC export is exceeded by C fixation in May Creek: A late-successional watershed of the Copper River Basin, Alaska

et al. 2019

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Understanding the entirety of basin-scale C cycling (DOC fluxes and CO2 exchanges) are central to a holistic perspective of boreal forest biogeochemistry today. Shifts in the timing and magnitude of dissolved organic carbon (DOC) delivery in streams and eventually into oceans can be expected, while simultaneously CO2 emission may exceed CO2 fixation, leading to forests becoming stronger CO2 sources than sinks amplifying rising trace gases in the atmosphere. At May Creek, a representative late-successional boreal forest watershed at the headwaters of the Copper River Basin, Alaska, we quantified the seasonality of DOC flux and landscape-scale CO2 exchange (eddy covariance) over two seasonal cycles. We deployed in situ fDOM and conductivity sensors, performed campaign sampling for water quality (DOC and water isotopes), and used fluorescence spectroscopy to ascertain DOC character. Simultaneously, we quantified net CO2 exchange using a 100 ft eddy covariance tower. Results indicate DOC exports were pulse-driven and mediated by precipitation events. Both frequency and magnitude of pulse-driven DOC events diminished as the seasonal thaw depth deepened, with inputs from terrestrial sources becoming major contributors to the DOC pool with decreasing snowmelt contribution to the hydrograph. A three-component parallel factorial analysis (PARAFAC) model indicated DOC liberated in late-season may be bioavailable (tyrosine-like). Combining Net Ecosystem Exchange (NEE) measurements indicate that the May Creek watershed fixes 142–220 g C m-2 yr-1 and only 0.40–0.57 g C m-2 yr-1 is leached out as DOC. Thus, the May Creek watershed and similar mature spruce forest dominated watersheds in the Copper River Basin are currently large ecosystem C sinks and exceeding C conservative. An understanding of DOC fluxes from Gulf of Alaska watersheds is important for characterizing future climate change-induced seasonal shifts.

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“…Besides the As content of the sediment, specific redox kinetics and microbial processes, as well as stoichiometry and chemical composition should be further investigated. 35 This is of special interest for assessing the potential vulnerability of the deep, Pleistocene aquifer to As mobilization, which is an important clean source of drinking water in the region.…”

Section: Perspectivesmentioning

confidence: 99%

“…33,34 Recent studies used fluorescence ratios, such as freshness and the humification index, as well as PARAFAC modeling to analyze shallow groundwater samples from West Bengal and have observed a link between humic-like DOM and high As concentrations. 8,32,35 However, a common caveat in PARAFAC modeling is that data sets must contain sufficient variability in fluorescent properties; therefore, large data sets (>100 samples) are preferable. 36 This represents a barrier preventing the widespread implementation of this method in practice, i.e., in field studies, as it is often not possible to collect such large data sets due both to financial and practical constraints.…”

Section: Introductionmentioning

confidence: 99%

Investigating Fluorescent Organic-Matter Composition as a Key Predictor for Arsenic Mobility in Groundwater Aquifers

Schittich

Wünsch

Kulkarni

et al. 2018

Environ. Sci. Technol.

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Dissolved organic matter (DOM) is linked to the heterogeneous distribution of elevated arsenic (As) in groundwater used for drinking and irrigation purposes, but the relationship between DOM characteristics and arsenic mobility has yet to be fully understood. Here, DOM from groundwater sampled in the Bengal Basin region was characterized using both conventional bulk emission-excitation (EEM) spectroscopy and high-performance size exclusion chromatography coupled to spectroscopy (HPSEC-EEM). Notably, application of the novel HPSEC-EEM approach permitted the total fluorescence of individual samples to be independently resolved into its underlying components. This allowed the external validation of the bulk-sample fluorescence decomposition and offered insight into the molecular size distribution of fluorescent DOM. Molecular size distributions were similar for the UVA fluorescent (C 310 , C 340) as well as the three visible fluorescent (C 390 , C 440 C 500) components. There was a greater visible fluorescence in shallow aquifer samples (10-33 m) with high As (SH, up to 418µg/L) than in samples from the same depth with lower As (up to 40µg/L). This indicated a link between DOM quality and As mobility within the shallow aquifer. The deep aquifer samples (170-200 m) revealed DOM characteristics similar to SH samples but had low As concentrations (<4µg/L), signifying that the deep aquifer is potentially vulnerable to As contamination. These findings pave the way for a more comprehensive assessment of the susceptibility of drinking water aquifers, thereby supporting the management of groundwater resources.

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Influence of monsoonal recharge on arsenic and dissolved organic matter in the Holocene and Pleistocene aquifers of the Bengal Basin

Cited by 58 publications

References 85 publications

Dynamic changes in size‐fractionated dissolved organic matter composition in a seasonally ice‐covered Arctic River

Dynamic changes in size‐fractionated dissolved organic matter composition in a seasonally ice‐covered Arctic River

DOC export is exceeded by C fixation in May Creek: A late-successional watershed of the Copper River Basin, Alaska

Investigating Fluorescent Organic-Matter Composition as a Key Predictor for Arsenic Mobility in Groundwater Aquifers

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