Effects of bottom water dissolved oxygen variability on copper and lead fractionation in the sediments across the oxygen minimum zone, western continental margin of India

Chakraborty, Parthasarathi; Chakraborty, Sucharita; Jayachandran, Saranya; Madan, R.D.; Sarkar, Arindam; Linsy, P.; Nath, B. Nagender

doi:10.1016/j.scitotenv.2016.05.125

Cited by 45 publications

(21 citation statements)

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“…The impacts of changing DO concentrations of the overlying bottom water on Cr association with Fe/Mn‐oxyhydroxide and sedimentary organic binding phases are discussed below. There was significant variation in Cr concentration associated with Fe/Mn‐oxyhydroxide phase in the sediment (like Cu and Pb as found in our previous study; Chakraborty et al, 2016a). A positive correlation existed between the fraction of the nonresidual Cr content in Fe/Mn‐oxyhydroxide binding phase (Cr Fr.…”

Section: Resultssupporting

confidence: 80%

“…The closed northern side with no subtropical convergence or deep water formation leads to a unique thermohaline formation and circulation pattern in the Arabian Sea (Morrison et al, ). The detailed description of the study area and the general methodology has been reported in our previous study (Chakraborty, Mason, et al, ; Chakraborty, Ramteke, et al, ).…”

Section: Methodsmentioning

confidence: 99%

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Chromium speciation in the sediments across the oxygen minimum zone, western continental margin of India

2018

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This study suggests that varying concentration of dissolved oxygen of overlying bottom water influences geochemical fractionation, speciation, and oxidation state of sedimentary Cr in a marine system. The nature of sedimentary organic matter (labile or nonlabile) and Fe speciation also controls the geochemical fractionation and oxidation state of Cr in the sediment from the continental margin across the oxygen minimum zone of the Arabian Sea. Increasing concentration of sedimentary organic matter (under hypoxic conditions) increased association of Cr with sedimentary organic binding phases. The association of Cr with Fe‐Mn‐oxyhydroxide phase gradually decreased with decreasing dissolved oxygen concentration due to the reduction and dissolution of Fe (III). The sedimentary organic matter was found to be the major hosting phase for Cr (VI) in the shelf sediments. The decrease in sedimentary Fe (III) concentration under hypoxic conditions also prevented Cr (VI) reduction. This study suggests that the type of sedimentary organic matter and Fe (III) concentration may influence benthic exchange fluxes of Cr under variable redox conditions in many coastal/margin systems.

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Section: Resultssupporting

confidence: 80%

Section: Methodsmentioning

confidence: 99%

Chromium speciation in the sediments across the oxygen minimum zone, western continental margin of India

2018

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“…The precision of the analysis was within ±5%. The NC reference soil sample (containing 3.5% C) was used as the certified reference material (CRM; P. Chakraborty, Chakraborty, Jayachandran, et al, ; Halvorson, Gonzalez, & Hagerman, ). TIC was determined by coulometry (UIC Coulometrics, Illinois).…”

Section: Methodsmentioning

confidence: 99%

Distribution and geochemical fractionation of lead in the continental shelf sediments around India

Chakraborty

Sarkar

et al. 2018

Geological Journal

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This study provides the first, preliminary data on geochemical distribution and fractionation of Pb (a toxic heavy metal) in continental shelf sediments around India and identifies the factors that control geochemical fractionation processes of Pb in convoluted coastal marine sediments. For the sake of clarity, the long coastline (~7,000 km) of India was divided into 6 coastal regions in this study. The total concentration of sedimentary Pb showed regional variation along the coast. The highest median concentration of Pb was found in the sediments collected from the north‐east region (26.5 mg/kg) followed by the north‐west (21.4 mg/kg) > central‐east (20.6 mg/kg) > south‐west (13.7 mg/kg) > south‐east (13.3 mg/kg) > central‐west (12.5 mg/kg) regions. Geochemical fractionation study suggested that the concentration of sedimentary Fe–Mn in oxyhydroxide form and the nature of sedimentary organic matters determined the geochemical distribution and fractionation of Pb in the shelf sediments. The major Pb hosting phases in the shelf sediments were the Fe–Mn oxyhydroxide phase followed by the sedimentary organic matter binding phases. The concentration of nonresidual Pb complexes in the shelf sediment was found to depend on the total sedimentary Pb loading. This study suggests that increase of anthropogenic Pb input and expansion of reduced oxygen levels in the coastal marine environment may have detrimental effects on the increasing mobility and bioavailability of Pb in the coastal areas around India.

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“…High sulphate reduction rates (sulphate consumption) also reiterate the extent of organic matter oxidation and the associated diagenetic processes in the Bay of Bengal compared to the Arabian Sea 32 . The Fe-oxides which are utilized for organic matter degradation release reduced Fe and P to pore waters from Fe-reduction zone 33 . Both Fe and P diffuse towards the sediment surface.…”

mentioning

confidence: 99%

“…On the other hand, P Fe is released to pore water due to wide and intense mid-depth OMZ in the Arabian Sea. Due to dissolution of Fe (oxy)hydroxides in sediments underlying the OMZ 33 , the dissolved phosphate either accumulates in pore waters or diffuses to the overlying water column. The pore-waterdissolved phosphate upon reaching saturation precipitates as solid phase P aut mineral, CFA.…”

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confidence: 99%

Phosphorus Accumulation Associated with Intense Diagenetic Metal-Oxide Cycling in Sediments along the Eastern Continental Margin of India

Babu

Ramaswamy

2017

Current Science

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Effects of bottom water dissolved oxygen variability on copper and lead fractionation in the sediments across the oxygen minimum zone, western continental margin of India

Cited by 45 publications

References 50 publications

Chromium speciation in the sediments across the oxygen minimum zone, western continental margin of India

Chromium speciation in the sediments across the oxygen minimum zone, western continental margin of India

Distribution and geochemical fractionation of lead in the continental shelf sediments around India

Phosphorus Accumulation Associated with Intense Diagenetic Metal-Oxide Cycling in Sediments along the Eastern Continental Margin of India

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