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

Samanta, Saumik; Dalai, Tarun K.; Pattanaik, Jitendra Kumar; Santosh, K.; Mazumdar, Aninda

doi:10.1016/j.gca.2015.05.040

Cited by 104 publications

(75 citation statements)

References 76 publications

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“…Because of the diversity of landforms and geology covered, we believe these groundwater C values are likely substantially similar to the concentrations and distribution beneath other continents. Measurements of groundwater DOC (e.g., Huang et al 2015, Thayalakumaran et al 2015, Weigand et al 2017 and DIC (e.g., Chaillou et al 2014, Samanta et al 2015, Cao et al 2016) under other countries and continents, although rare, are in the same ranges as those in our survey. We determined the average C content at various depths by smoothing the depth versus groundwater age relationship using locally weighted sequential smoothing (Cleveland 1979) as described earlier.…”

Section: Introductionsupporting

confidence: 67%

Size, age, renewal, and discharge of groundwater carbon

Downing

Striegl

2018

Inland Waters

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Groundwater carbon (C) supply to lakes and streams is important to understanding the role of inland waters in global and regional cycles and in the functioning of aquatic ecosystems. We provide new estimates of the size and discharge of the groundwater C pool using data from a broad survey of groundwater C, information on the depth distribution of groundwater, and data on groundwater age. About 0.25 × 10 6 km 3 of the 8 × 10 6 km 3 of groundwater resource is within 100 m of the surface and 4.2 × 10 6 km 3 is above 2000 m. Ages show an average groundwater turnover time of 10 yr at 25 m, 350 yr at 100 m, increasing to about 100 000 yr at 600 m. Global groundwater discharge is 16 000 km 3 yr −1; >16% of precipitation passes through groundwater. Groundwater dissolved organic C (DOC) can be high in shallow groundwater but stabilizes at ~2-4 mg L −1 at 100 m. Average groundwater dissolved inorganic C (DIC) is ~30-43 mg L −1. Groundwater C content to 2000 m is ~145 Pg, about the same as all marine sediments and about one-sixth that of the surface ocean. Groundwater C discharge to continental waters is 0.68 Pg yr −1 , or 3.4 times that estimated from river base-flow and submarine groundwater discharge. This discharge is 68 times previous estimates, implying a total C flux from land of 3.6 Pg yr −1 ; 80% of discharge occurs from above 40 m and 99% from the upper 100 m.

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Section: Introductionsupporting

confidence: 67%

Size, age, renewal, and discharge of groundwater carbon

Downing

Striegl

2018

Inland Waters

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“…As summarized in Table 3, many studies of aquatic CO2 dynamics in India have been conducted in estuaries and coastal areas (e.g., Mukhopadhyay et al, 2002;Biswas et al, 2004;Gupta et al, 2009;Sarma et al, 2012;Samanta et al, 2015), except for the secondary data of pCO2 that can be estimated based on CO2 system calculations (Pierrot et al, 2006) and water quality data collected in various headwaters (Sarin et al, 1989;Bickle et al, 2003;Chakrapani and Veizer, 2005) and 440 lower reaches (Manaka et al, 2015) of the Ganges-Brahmaputra. The values of pCO2 estimated for some headwaters, lower reaches, and tributaries of the Ganges basin (mean: 891; range: 16-2,778 µatm) were relatively low compared to other Asian rivers (Table 3).…”

Section: Effects Of Increasing Water Pollution In Asian River Systemsmentioning

confidence: 99%

“…In a study of human impacts on C dynamics in the Cochin estuary, Southern India, Gupta et al (2009) ascribed monsoonal pCO2 increases up to 6,000 atm to the enhanced decomposition of 445 the OM released from anthropogenic sources upstream. A particular attention has been paid to the emission of CO2 and CH4 from the Indian part of the deltaic region of the Ganges-Brahmaputra system that includes estuaries with contrasting biogeochemical features: the anthropogenically impacted Hooghly estuary and the mangrove-dominated estuaries of Sundarbans, the world's largest mangrove ecosystem (Mukhopadhyay et al, 2002;Biswas et al, 2004;Biswas et al, 2007;Dutta et al, 2015Dutta et al, , 2017Samanta et al, 2015). The Hooghly estuary was found as net heterotrophic, with the fugacity of 450 CO2 (fCO2) and CH4 levels varying from ~ 400-700 µatm and 10.3-59.25 nM, respectively (Mukhopadhyay et al, 2002;Biswas et al, 2007).…”

Section: Effects Of Increasing Water Pollution In Asian River Systemsmentioning

confidence: 99%

“…Based on the mass balance between source and sink inventories, Dutta et al (2015) estimated that annually ~0.5 Gg of CH4 was exported from the estuaries of Sundarbans to the northern Bay of Bengal.) Although other components of the estuarine C biogeochemistry have not yet been studied comprehensively in these systems, Samanta et al (2015) reported a large annual DIC export [(3.1-3.7) x 10 12 g] from the Hooghly estuary to the Bay of Bengal, suggesting estuarine conservative mixing as well as in situ 460 biogeochemical processes such as OM biodegradation and carbonate dissolution as key controls on the export and isotopic composition of DIC. The saline estuarine zone functioned as an important source of DIC (up to 50% of the annual estuarine export to the bay), particularly in the monsoon periods.…”

Section: Effects Of Increasing Water Pollution In Asian River Systemsmentioning

confidence: 99%

“…The saline estuarine zone functioned as an important source of DIC (up to 50% of the annual estuarine export to the bay), particularly in the monsoon periods. Based on a few available data of wastewater discharge and DIC concentrations, direct anthropogenic sources of DIC within the Hooghly basin were estimated to account for only 2-3% of the river water DIC concentrations, although it remains unanswered how much the biodegradation of organic C released 465 from anthropogenic sources could contribute to DIC generation during the transport to the bay (Samanta et al, 2015). Large knowledge gaps still exist in understanding human influences on emissions of CO2 and other GHGs from the estuaries of the eastern India and associated river systems.…”

Section: Effects Of Increasing Water Pollution In Asian River Systemsmentioning

confidence: 99%

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Reviews and syntheses: Anthropogenic perturbations to carbon fluxes in Asian river systems: Concepts, emerging trends, and research challenges

Park¹,

Nayna²,

Begum³

et al. 2018

Preprint

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Abstract. Human activities are drastically altering water and material flows in river systems across Asia. These anthropogenic perturbations have rarely been linked to the carbon (C) fluxes of Asian rivers that may account for up to 40-20 50% of the global fluxes. The primary object of this review was to provide a conceptual framework for assessing human impacts on Asian river C fluxes, along with a latest update on anthropogenic alterations of riverine C fluxes, focusing on the impacts of water pollution and river impoundments on CO2 outgassing from the rivers draining South, Southeast, and East Asian regions that account for the largest fraction of river discharge and C exports from Asia and Oceania. Recent booms in dam construction across Asia have created a host of environmental problems; yet only a small number of studies have 25 explicitly investigated altered rates of greenhouse gas (GHG) emissions and organic C transport. There have been contrasting reports on impoundment effects: decreases in GHG emissions in the reservoirs exhibiting enhanced primary production vs. increased emissions from the flooded vegetation and soils in the early years following dam construction or from the impounded river reaches and downstream estuaries during the monsoon period. These contrasting results suggest that the rates of metabolic processes in the impounded and downstream reaches can greatly vary longitudinally over time, as 30 a combined result of diel shifts in the balance between autotrophy and heterotrophy, seasonal fluctuations between the dry and monsoon periods, and a long-term change from a leaky post-construction phase to a gradual C sink. Rapid pace of urbanization across southern and eastern Asian regions has dramatically increased municipal water withdrawal, generating annually 120.2 km 3 of wastewater in 24 countries, which comprises 38.6% of the global municipal wastewater production disproportionately affect the receiving river water, particularly downstream of rapidly expanding metropolitan areas, including eutrophication, increases in the amount and lability of organic C, and pulse emissions of CO2 and other greenhouse gases (GHGs). As reviewed for three representative rivers (the Ganges, Mekong, and Yellow River), the lower reaches of these rivers and their polluted tributaries tend to exhibit higher levels of organic C and the partial pressure of CO2 (pCO2) than the eutrophic reservoirs and less impacted upstream reaches. More field measurements of pCO2, together with accurate 40 flux calculations based on river-specific model parameters, are urgently required to provide more accurate estimates of GHG emissions from the Asian rivers that are now underrepresented in the global C budgets. Researchers working on individual river systems need to be linked to collaborative research networks to facilitate global synthesis of local field data. These synthesis efforts, combined with conceptual and mathematical models, will contribute to a better understanding of how anthropogenic perturbations in rapidly urb...

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A comparison of CO₂ dynamics and air‐water fluxes in a river‐dominated estuary and a mangrove‐dominated marine estuary

Akhand

Chanda

Manna

et al. 2016

Geophysical Research Letters

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The fugacity of CO2 (fCO2 (water)) and air‐water CO2 flux were compared between a river‐dominated anthropogenically disturbed open estuary, the Hugli, and a comparatively pristine mangrove‐dominated semiclosed marine estuary, the Matla, on the east coast of India. Annual mean salinity of the Hugli Estuary (≈7.1) was much less compared to the Matla Estuary (≈20.0). All the stations of the Hugli Estuary were highly supersaturated with CO2 (annual mean ~ 2200 µatm), whereas the Matla was marginally oversaturated (annual mean ~ 530 µatm). During the postmonsoon season, the outer station of the Matla Estuary was under saturated with respect to CO2 and acted as a sink. The annual mean CO2 emission from the Hugli Estuary (32.4 mol C m−2 yr−1) was 14 times higher than the Matla Estuary (2.3 mol C m−2 yr−1). CO2 efflux rate from the Hugli Estuary has increased drastically in the last decade, which is attributed to increased runoff from the river‐dominated estuary.

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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

Cited by 104 publications

References 76 publications

Size, age, renewal, and discharge of groundwater carbon

Size, age, renewal, and discharge of groundwater carbon

Reviews and syntheses: Anthropogenic perturbations to carbon fluxes in Asian river systems: Concepts, emerging trends, and research challenges

A comparison of CO₂ dynamics and air‐water fluxes in a river‐dominated estuary and a mangrove‐dominated marine estuary

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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

Cited by 104 publications

References 76 publications

Size, age, renewal, and discharge of groundwater carbon

Size, age, renewal, and discharge of groundwater carbon

Reviews and syntheses: Anthropogenic perturbations to carbon fluxes in Asian river systems: Concepts, emerging trends, and research challenges

A comparison of CO2 dynamics and air‐water fluxes in a river‐dominated estuary and a mangrove‐dominated marine estuary

Contact Info

Product

Resources

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A comparison of CO₂ dynamics and air‐water fluxes in a river‐dominated estuary and a mangrove‐dominated marine estuary