scholarly journals Reconciling drainage and receiving basin signatures of the Godavari River system

2018 ◽  
Author(s):  
Muhammed O. Usman ◽  
Frédérique M. S. A. Kirkels ◽  
Huub M. Zwart ◽  
Sayak Basu ◽  
Camilo Ponton ◽  
...  
Keyword(s):  
Grain Size ◽  
Organic Carbon ◽  
Surface Area ◽  
Continental Margin ◽  
Bay Of Bengal ◽  
River Sediments ◽  
River System ◽  
Peninsular India ◽  
Godavari River ◽  
Godavari Basin

Abstract. The modern-day Godavari River transports large amounts of sediment (170 Tg per year) and terrestrial organic carbon (OCterr; 1.5 Tg per year) from peninsular India to the Bay of Bengal. The flux and nature of OCterr is considered to have varied in response to past climate and human forcing. In order to delineate the provenance and nature of organic matter (OM) exported by the fluvial system and establish links to sedimentary records accumulating on its adjacent continental margin, the stable and radiogenic isotopic composition of bulk OC, abundance and distribution of long-chain fatty acids (LCFA), sedimentological properties (e.g. grain size, mineral surface area etc.) of fluvial (riverbed and riverbank) sediments and soils from the Godavari basin were analysed and these characteristics were compared to those of a sediment core retrieved from the continental slope depocenter. Results show that river sediments from the upper catchment exhibit higher total organic carbon (TOC) contents than those from the lower part of the basin. The general relationship between TOC and sedimentological parameters (i.e., mineral-specific surface area and grain size) of the sediments suggests that sediment mineralogy, largely driven by provenance, plays an important role in the stabilization of OM during transport along the river axis, and in preservation of OM exported by the Godavari to the Bay of Bengal. The stable carbon isotopic (δ13C) characteristics of river sediments and soils indicate that the upper mainstream and its tributaries drain catchments exhibiting more 13C enriched carbon than the lower stream resulting from the regional vegetation gradient and/or net balance between the upper (C4-dominated plants) and lower (C3-dominated plants) catchments. The radiocarbon contents of organic carbon (Δ14COC) in deep soils and eroding riverbanks suggests these are likely sources of “old” or pre-aged carbon to the Godavari River that increasingly dominates the late Holocene portion of the offshore sedimentary record. Reduced monsoonal rainfall and sediment transport impeded by recent dam constructions have drastically impacted the flux, loci and composition of OC exported from the modern Godavari basin, rendering it challenging to reconcile modern-day river geochemistry with that recorded in continental margin sediments.

scholarly journals Reconciling drainage and receiving basin signatures of the Godavari River system

2018 ◽  
Vol 15 (11) ◽  
pp. 3357-3375 ◽  
Author(s):  
Muhammed Ojoshogu Usman ◽  
Frédérique Marie Sophie Anne Kirkels ◽  
Huub Michel Zwart ◽  
Sayak Basu ◽  
Camilo Ponton ◽  
...  
Keyword(s):  
Grain Size ◽  
Organic Carbon ◽  
Surface Area ◽  
Continental Margin ◽  
Bay Of Bengal ◽  
River Sediments ◽  
Mineral Surface ◽  
Godavari River ◽  
Mineral Surface Area ◽  
Godavari Basin

Abstract. The modern-day Godavari River transports large amounts of sediment (170 Tg per year) and terrestrial organic carbon (OCterr; 1.5 Tg per year) from peninsular India to the Bay of Bengal. The flux and nature of OCterr is considered to have varied in response to past climate and human forcing. In order to delineate the provenance and nature of organic matter (OM) exported by the fluvial system and establish links to sedimentary records accumulating on its adjacent continental margin, the stable and radiogenic isotopic composition of bulk OC, abundance and distribution of long-chain fatty acids (LCFAs), sedimentological properties (e.g. grain size, mineral surface area, etc.) of fluvial (riverbed and riverbank) sediments and soils from the Godavari basin were analysed and these characteristics were compared to those of a sediment core retrieved from the continental slope depocenter. Results show that river sediments from the upper catchment exhibit higher total organic carbon (TOC) contents than those from the lower part of the basin. The general relationship between TOC and sedimentological parameters (i.e. mineral surface area and grain size) of the sediments suggests that sediment mineralogy, largely driven by provenance, plays an important role in the stabilization of OM during transport along the river axis, and in the preservation of OM exported by the Godavari to the Bay of Bengal. The stable carbon isotopic (δ13C) characteristics of river sediments and soils indicate that the upper mainstream and its tributaries drain catchments exhibiting more 13C enriched carbon than the lower stream, resulting from the regional vegetation gradient and/or net balance between the upper (C4-dominated plants) and lower (C3-dominated plants) catchments. The radiocarbon contents of organic carbon (Δ14COC) in deep soils and eroding riverbanks suggests these are likely sources of “old” or pre-aged carbon to the Godavari River that increasingly dominates the late Holocene portion of the offshore sedimentary record. While changes in water flow and sediment transport resulting from recent dam construction have drastically impacted the flux, loci, and composition of OC exported from the modern Godavari basin, complicating reconciliation of modern-day river basin geochemistry with that recorded in continental margin sediments, such investigations provide important insights into climatic and anthropogenic controls on OC cycling and burial.

scholarly journals Relationships between grain size and organic carbon 14C heterogeneity in continental margin sediments

2019 ◽  
Vol 505 ◽  
pp. 76-85 ◽  
Author(s):  
Rui Bao ◽  
Thomas M. Blattmann ◽  
Cameron McIntyre ◽  
Meixun Zhao ◽  
Timothy I. Eglinton
Keyword(s):  
Grain Size ◽  
Organic Carbon ◽  
Continental Margin

scholarly journals Multiple Ecological Parameters Affect Living Benthic Foraminifera in the River-Influenced West-Central Bay of Bengal

2021 ◽  
Vol 8 ◽  
Author(s):  
Thejasino Suokhrie ◽  
Rajeev Saraswat ◽  
Rajiv Nigam
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Dissolved Oxygen ◽  
Bay Of Bengal ◽  
Benthic Foraminifera ◽  
Coarse Fraction ◽  
Godavari River ◽  
West Central ◽  
Ecological Parameters ◽  
Chemical Conditions

The huge riverine influx and associated processes decrease the ambient salinity, stratify the water column, modulate the oxygen-deficient zone, and are also responsible for the recent acidification in the Bay of Bengal. Here, we have studied the effect of these riverine influx-dominated ecological parameters on living benthic foraminifera in the west-central Bay of Bengal. We report that the pH below 7.6 in front of the Krishna river, reduces the diversity and the richness of living benthic foraminifera on the adjacent shelf and the slope. A similar decreased diversity and richness is also observed in front of the Godavari River. We delineate three prominent assemblages, representing different depth zones with associated distinct physico-chemical conditions. The shallow water assemblage (∼27–100 m) is represented by Nonionella labradorica, Hanzawaia nipponica, Brizalina dilatata, Ammonia tepida, and Nonionella limbato-striata. These species are adapted to relatively warmer temperatures and more oxygenated waters. The deepwater assemblage (∼1,940–2,494 m) includes Bulimina cf. delreyensis, Bulimina marginata, Hormosinella guttifera, Cassidulina laevigata, and Gyroidinoides subzelandica and can tolerate a relatively colder temperature. The intermediate-depth assemblage (∼145–1,500 m) dominated by Eubuliminella exilis, Bolivinellina earlandi, Fursenkoina spinosa, Bolivinellina lucidopunctata, Globobulimina globosa, Fursenkoina spinosa, Eubuliminella cassandrae, Uvigerina peregrina, Rotaliatinopsis semiinvoluta, and Cassidulina laevigata, represents oxygen-deficient and organic carbon-rich environment. Besides the pH, temperature, dissolved oxygen and organic matter, we also report a strong influence of bathymetry, coarse fraction (CF) and the type of organic matter on a few living benthic foraminifera. The ecological preferences of 40 such dominant living benthic foraminifera, each representing a specific environment, have also been reported for site-specific proxy. We conclude that although the huge riverine influx affects living benthic foraminifera on the shelf, the dissolved oxygen and organic carbon mostly control benthic foraminiferal distribution in the deeper west-central Bay of Bengal.

scholarly journals Effect of calcination temperature on neptunium dioxide microstructure and dissolution

2020 ◽  
Vol 7 (12) ◽  
pp. 3869-3876
Author(s):  
Kathryn M. Peruski ◽  
Brian A. Powell
Keyword(s):  
Grain Size ◽  
Free Energy ◽  
Surface Area ◽  
Calcination Temperature ◽  
Surface Free Energy ◽  
Neptunium Dioxide

Solubility of neptunium dioxide decreases as microstructure grain size increases, likely due to decreasing surface free energy and surface area.

Organic carbon oxidation and preservation in NW Atlantic continental margin sediments

1987 ◽  
Vol 31 (1) ◽  
pp. 215-236 ◽  
Author(s):  
D. Heggie ◽  
C. Maris ◽  
A. Hudson ◽  
J. Dymond ◽  
R. Beach ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Continental Margin ◽  
Carbon Oxidation ◽  
Organic Carbon Oxidation

scholarly journals Presence of continental and Bay of Bengal moisture in rainfall at Kolkata, revealed through simultaneous observation from land and sea during South-West monsoon of 2004

2016 ◽  
Author(s):  
Shaakir Shabir Dar ◽  
Prosenjit Ghosh
Keyword(s):  
Isotopic Composition ◽  
Bay Of Bengal ◽  
Indian Subcontinent ◽  
Isotopic Signature ◽  
Peninsular India ◽  
Gangetic Plain ◽  
Prevailing Wind Direction ◽  
South West Monsoon ◽  
Continental Source ◽  
Sw Monsoon

Abstract. The backward air mass trajectory analysis (HYSPLIT) during the summer monsoon suggests that the rain which precipitates at Kolkata is generated from a moisture parcel which originates from the Arabian Sea and moves inland over the dry Indian subcontinent or over the Bay of Bengal. We used monthly satellite and ground based measurements of the hydro-meteorological variables together with isotope data from Bangalore, Bay of Bengal and Kolkata and other locations to quantify the contribution of different moisture sources during the SW Monsoon. The vapor mass as it moves under the prevailing wind direction was subjected to isotopic modification due to addition of evaporated moisture from Bay of Bengal and rainout process. This was simulated using Craig and Gordon model and Rayleigh fractionation model respectively. The moisture generated during the process of evaporation from Bay of Bengal surface ocean gets advected towards the continent and precipitates as rainfall or snowfall over the Indo-Gangetic plain. We assumed based on our observation that the initial isotopic composition of vapor originating from the peninsular continental source is similar to our observation recorded at Bangalore station. It is found that the isotopic signature of Bangalore is completely lost albeit the significant contribution of the moisture from Bay of Bengal. To explain the isotopic composition of precipitation at Kolkata during the SW-Monsoon, it was necessary to invoke 75–80 % moisture contribution from the Bay of Bengal whereas the evaporated moisture parcel from the Peninsular India contribute 25 %–35 %.

scholarly journals Geochemistry and mineralogy of recent sediments of Guanabara Bay (NE sector) and its major rivers - Rio de Janeiro State - Brazil

2001 ◽  
Vol 73 (1) ◽  
pp. 121-133 ◽  
Author(s):  
MARCIA DE MELO FARIA ◽  
BRAZ A. SANCHEZ
Keyword(s):  
Heavy Metal ◽  
Grain Size ◽  
Clay Minerals ◽  
Bottom Sediments ◽  
River Sediments ◽  
Size Fraction ◽  
River Mouth ◽  
Guanabara Bay ◽  
Metal Contents ◽  
Recent Sediments

Geochemical and clay mineralogical studies of bottom sediments collected along the Macacu and Caceribu rivers and Guanabara Bay were carried out in order to investigate the relationship between major source areas and recent sediments of the bay. Clay mineralogy includes different groups with selective distribution conditioned by geomorphic features and depositional settings. Micaceous clay minerals are abundant near parent rock in the upper course, whereas kaolinite derived from varied sources is gradually concentrated towards the estuary. In the Guanabara Bay, kaolinite accumulates near river mouths, while micaceous clay minerals are converted into mixed layers in the estuary. Analyses of heavy metal contents reveal higher levels of Zn and Cu in sediments of the bay than in river sediments. Profiles along rivers indicate a downstream decrease of heavy metals, whereas in the bay geochemical trends display greater variations. In general river mouth sediments present the lowest concentrations. At the north and east of Paquetá Island anomalous areas with the highest heavy metal contents occur. Cu tends to concentrate in < 2mum grain-size fraction and indicates an association with micaceous clay minerals in the upper river course. However, Cu retention seems to be further controlled by other components of bottom sediments due to changes in physical and chemical conditions of the estuarine environment. Zn shows unstable behavior along the rivers and concentrates in the bay. Pb displays small variations from river to bay sediments, and accumulates mainly in the < 63mum grain-size fraction without any association with clay mineral. Geoaccumulation indexes of Cu, Pb and Zn classify the study area as unpolluted in both studied rivers and in the NE sector of the bay, though the enrichment factors are higher in the bay. The study does not indicate those rivers as major sources of heavy metal pollution to the bay.

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