Record Details

Dissolved inorganic carbon (DIC) and its δ13C in the Ganga (Hooghly) River estuary, India: Evidence of DIC generation via organic carbon degradation and carbonate dissolution

DRS at CSIR-National Institute of Oceanography

View Archive Info
 
 
Field Value
 
Title Dissolved inorganic carbon (DIC) and its δ13C in the Ganga (Hooghly) River estuary, India: Evidence of DIC generation via organic carbon degradation and carbonate dissolution
 
Creator Samanta, S.
Dalai, T.K.
Pattanaik, J.K.
Rai, S.K.
Mazumdar, A.
 
Subject CHEMISTRY AND BIOGEOCHEMISTRY
CHEMISTRY AND BIOGEOCHEMISTRY
 
Description In this study, we present comprehensive data on dissolved Ca, dissolved inorganic carbon (DIC) and its carbon isotope composition (δ13CDIC) of (i) the Ganga (Hooghly) River estuary water sampled during six seasons of contrasting water discharge over 2 years (2012 and 2013), (ii) shallow groundwater from areas adjacent to the estuary and (iii) industrial effluent water and urban wastewater draining into the estuary. Mass balance calculations indicate that processes other than the conservative mixing of seawater and river water are needed to explain the measured DIC and δ13CDIC. Results of mixing calculations in conjunction with the estimated undersaturated levels of dissolved O2 suggest that biological respiration and organic carbon degradation dominate over biological production in the estuary. An important outcome of this study is that a significant amount of DIC and dissolved Ca is produced within the estuary at salinity ⩾10, particularly during the monsoon period. Based on consideration of mass balance and a strong positive correlation observed between the “excess” DIC and “excess” Ca, we contend that the dominant source of DIC generated within the estuary is carbonate dissolution that is inferred to be operating in conjunction with degradation of organic carbon. Calculations show that groundwater cannot account for the observed “excess” Ca in the high salinity zone. Estimated DIC contributions from anthropogenic activity are minor, and they constitute ca. 2–3% of the river water DIC concentrations.The estimated annual DIC flux from the estuary to the Bay of Bengal is ca. (3–4) × 1012 g, of which ca. 40–50% is generated within the estuary. The monsoon periods account for the majority (ca. 70%) of the annual DIC generation in the estuary. The annual DIC flux from the Hooghly estuary accounts for ca. 1% of the global river DIC flux to the oceans. This is disproportionately higher than the water contribution from the Hooghly River to the oceans, which accounts for ca. 0.2% of the global river water flux. The results of this study suggest that estuaries in regions affected by tropical monsoon can be important in terms of their production of significant amounts of DIC and its delivery to the world’s oceans.
 
Date 2015-10-27T10:37:31Z
2015-10-27T10:37:31Z
2015
 
Type Journal Article
 
Identifier Geochimica et Cosmochimica Acta, vol.165; 2015; 226-248
http://drs.nio.org/drs/handle/2264/4832
 
Language en
 
Rights An edited version of this paper was published by Elsevier. Copyright [2015] Elsevier
 
Publisher Elsevier