Carbon dioxide emissions from Indian monsoonal estuaries

Sarma, V. V. S. S.; Viswanadham, R.; Rao, G. D.; Prasad, Vandana; Kumar, Birendra; Naidu, S. A.; Kumar, Naveen; Rao, Desiraju B.; Tallapragada, Sridevi; Krishna, M. S.; Reddy, N. P. C.; Sadhuram, Y.; Murty, T.V.R.

doi:10.1029/2011gl050709

Cited by 99 publications

(82 citation statements)

References 34 publications

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“…On the other hand, lower mean values of pH were found in the west coast estuaries (6.8290.52) than the east coast estuaries (7.6590.57), suggesting that further higher nutrients in the former are caused by higher rates of organic matter decomposition and it is consistent with DO saturation. Recently Sarma et al (2012) found higher pCO 2 levels in the Indian estuaries, which were attributed to organic matter decomposition. Nevertheless, the annual mean N 2 O saturation in the Indian estuaries (2049137%) was significantly less than the European (465%; Bange, 2006 and271% Barnes andUpstill-Goddard, 2011) and the American estuaries (165Á618% ; Table S1; supplementary information).…”

Section: Spatial and Temporal Variations In N 2 O Concentrations In Tmentioning

confidence: 95%

“…Hence, the biogeochemical processes in monsoonal estuaries during discharge period could be completely different from that of a dry period. Recently, Sarma et al (2012) estimated emissions of CO 2 from the Indian estuaries as Â2 )10 12 gC to the atmosphere annually, which is about 10 times less compared to European estuaries. Such low CO 2 fluxes from the Indian estuaries result from high flushing rates and less dense human settlements along the banks of estuaries.…”

Section: Introductionmentioning

confidence: 99%

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Contribution of N2O emissions to the atmosphere from Indian monsoonal estuaries

Gijjapu

Sarma

2013

Tellus B: Chemical and Physical Meteorology

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A B S T R A C T Estuaries are known to contribute a significant amount of nitrous oxide (N 2 O) to the atmosphere; however, the contribution from the Indian estuaries is unknown. We made an attempt to estimate emissions of N 2 O from the Indian estuaries by collecting samples from 28 major and minor estuaries along the Indian coast during the wet and dry periods. The N 2 O was mostly saturated in all measured Indian estuaries during the study period (72Á631%), with exceptionally high saturation in the Ponniyaar estuary (5902%) during the wet period. The N 2 O saturation displayed a strong relation with dissolved inorganic nitrogen (DIN; nitrate ' nitrite and ammonium), ammonium and dissolved oxygen saturation, suggesting that nitrification is the major source of N 2 O in the Indian estuaries. The negative relation between salinity and N 2 O saturation suggests inner estuaries are a strong source compared to outer estuaries. The annual mean N 2 O saturation (2049137%) and fluxes (1.3 mmol N 2 O m (2 d (1 ) in the Indian estuaries were significantly less than European estuaries (271% andThe estimation of flux of N 2 O from the European estuaries was also biased due to the inclusion of an exceptionally high supersaturation value from a small UK estuary, Colne (2645%). However, low N 2 O saturation and fluxes in the Indian estuaries were related to mean low concentration of DIN that led to low nitrification rates compared to world estuaries. Despite India ranking second in artificial fertilizers use, high flushing rates during the wet period reduce residence time leading to less modification within the estuary.

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Section: Spatial and Temporal Variations In N 2 O Concentrations In Tmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

Contribution of N2O emissions to the atmosphere from Indian monsoonal estuaries

Gijjapu

Sarma

2013

Tellus B: Chemical and Physical Meteorology

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“…The estimated carbon release to the atmosphere from Indian (inner) estuaries (1.9 Tg C yr −1 ; Sarma et al, 2012) is relatively small compared to the total river flux of South Asia region. The monsoonal discharge through these estuaries have a short residence time of OC, which helps the OC matters to be transported relatively unprocessed to the open/deeper ocean.…”

Section: Riverine Carbon Fluxmentioning

confidence: 97%

The carbon budget of South Asia

et al. 2013

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Abstract. The source and sinks of carbon dioxide (CO 2 ) and methane (CH 4 ) due to anthropogenic and natural biospheric activities were estimated for the South Asian region (Bangladesh, Bhutan, India, Nepal, Pakistan and Sri Lanka). Flux estimates were based on top-down methods that use inversions of atmospheric data, and bottom-up methods that use field observations, satellite data, and terrestrial ecosystem models. Based on atmospheric CO 2 inversions, the net biospheric CO 2 flux in South Asia (equivalent to the Net Biome Productivity, NBP) was a sink, estimated at −104 ± 150 Tg C yr −1 during [2007][2008]. Based on the bottom-up approach, the net biospheric CO 2 flux is estimated to be −191 ± 193 Tg C yr −1 during the period of 2000-2009. This last net flux results from the following flux components: (1) the Net Ecosystem Productivity, NEP (net primary production minus heterotrophic respiration) of −220 ± 186 Tg C yr −1 (2) the annual net carbon flux from land-use change of −14 ± 50 Tg C yr −1 , which resulted from a sink of −16 Tg C yr −1 due to the establishment of tree plantations and wood harvest, and a source of 2 Tg C yr −1 due to the expansion of croplands; (3) the riverine export flux from terrestrial ecosystems to the coastal oceans of +42.9 Tg C yr −1 ; and (4) the net CO 2 emission due to biomass burning of +44.1 ± 13.7 Tg C yr −1 . Including the emissions from the combustion of fossil fuels of 444 Tg C yr −1 for the 2000s, we estimate a net CO 2 landatmosphere flux of 297 Tg C yr −1 . In addition to CO 2 , a fraction of the sequestered carbon in terrestrial ecosystems is released to the atmosphere as CH 4 . Based on bottom-up and top-down estimates, and chemistry-transport modeling, we estimate that 37 ± 3.7 Tg C-CH 4 yr −1 were released to atmosphere from South Asia during the 2000s. Taking all CO 2 and CH 4 fluxes together, our best estimate of the net land-atmosphere CO 2 -equivalent flux is a net source of 334 Tg C yr −1 for the South Asian region during the 2000s. If CH 4 emissions are weighted by radiative forcing of molecular CH 4 , the total CO 2 -equivalent flux increases to 1148 Tg C yr −1 suggesting there is great potential of reducing CH 4 emissions for stabilizing greenhouse gases concentrations.

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“…Since then, CO 2 data coverage has tremendously increased with additional studies at subtropical and tropical latitudes (for example Sarma et al, 2012;Chen et al, 2012;Rao and Sarma, 2016) and in the large river-estuarine systems such as the Amazon (Lefèvre et al, 2017), the Mississippi , the Yangtze (Changjiang) (Zhai et al, 2007;Zhang et al, 2008), and the Pearl (Guo et al, 2009;Zhou et al, 2009). The number of studies on CH 4 in estuarine and coastal environments has not increased in recent years as spectacularly as those concerning CO 2 , attracting less research efforts because the marine source of CH 4 to the atmosphere (0.4-1.8 TgCH 4 yr −1 ; Bates et al, 1996;Rhee et al, 2009) is very modest compared to other natural and anthropogenic CH 4 emissions (Kirschke et al, 2013); however, continental shelves and estuaries are more intense sources of CH 4 to the atmosphere than the open ocean, in particular shallow and permanently well-mixed coastal zones (Borges et al, 2016.…”

Section: Introductionmentioning

confidence: 99%

Carbon dynamics and CO2 and CH4 outgassing in the Mekong delta

2018

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Abstract. We report a data set of biogeochemical variables related to carbon cycling obtained in the three branches (M y Tho, Hàm Luông, Có Chiên) of the Mekong delta (Bén Tre province, Vietnam) in December 2003, April 2004, and October 2004. Both the inner estuary (upstream of the mouth) and the outer estuary (river plume) were sampled, as well as side channels. The values of the partial pressure of CO 2 (pCO 2 ) ranged between 232 and 4085 ppm, O 2 saturation level (%O 2 ) between 63 and 114 %, and CH 4 between 2 and 2217 nmol L −1 , within the ranges of values previously reported in temperate and tropical meso-and macro-tidal estuaries. Strong seasonal variations were observed. In the upper oligohaline estuary, low pCO 2 (479-753 ppm) and high %O 2 (98-106 %) values were observed in April 2004 most probably related to freshwater phytoplankton growth owing to low freshwater discharge (1400 m 3 s −1 ) and increase in water residence time; during the two other sampling periods with a higher freshwater discharge (9300-17 900 m 3 s −1 ), higher pCO 2 (1895-2664 ppm) and lower %O 2 (69-84 %) values were observed in the oligohaline part of the estuary. In October 2004, important phytoplankton growth occurred in the offshore part of the river plume as attested by changes in the contribution of particulate organic carbon (POC) to total suspended matter (TSM) (%POC) and the stable isotope composition of POC (δ 13 C-POC), possibly related to low TSM values (improvement of light conditions for phytoplankton development), leading to low pCO 2 (232 ppm) and high %O 2 (114 %) values. Water in the side channels in the Mekong delta was strongly impacted by inputs from the extensive shrimp farming ponds. The values of pCO 2 , CH 4 , %O 2 , and the stable isotope composition of dissolved inorganic carbon (δ 13 C-DIC) indicated intense organic matter degradation that was partly mediated by sulfate reduction in sediments, as revealed by the slope of total alkalinity (TA) and DIC covariations. The δ 13 C-POC variations also indicated intense phytoplankton growth in the side channels, presumably due to nutrient enrichment related to the shrimp farming ponds. A data set in the mangrove creeks of the Ca Mau province (part of the Mekong delta) was also acquired in April and October 2004. These data extended the range of variability in pCO 2 and %O 2 with more extreme values than in the Mekong delta (Bén Tre), with maxima and minima of 6912 ppm and 37 %, respectively. Similarly, the maximum CH 4 concentration (686 nmol L −1 ) was higher in the Ca Mau province mangrove creeks than in the Mekong delta (Bén Tre, maximum 222 nmol L −1 ) during the October 2004 cruise (rainy season and high freshwater discharge period). In April 2004 (dry season and low freshwater discharge period), the CH 4 values were much lower than in October 2004 (average 19 ± 13 and 210 ± 158 nmol L −1 , respectively) in the Ca Mau province mangrove creeks, owing to the higher salinity (average 33.2 ± 0.6 and 14.1 ± 1.2, respectively) that probably led to higher sedim...

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Carbon dioxide emissions from Indian monsoonal estuaries

Cited by 99 publications

References 34 publications

Contribution of N<sub>2</sub>O emissions to the atmosphere from Indian monsoonal estuaries

Contribution of N<sub>2</sub>O emissions to the atmosphere from Indian monsoonal estuaries

The carbon budget of South Asia

Carbon dynamics and CO<sub>2</sub> and CH<sub>4</sub> outgassing in the Mekong delta

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Carbon dioxide emissions from Indian monsoonal estuaries

Cited by 99 publications

References 34 publications

Contribution of N<sub>2</sub>O emissions to the atmosphere from Indian monsoonal estuaries

Contribution of N<sub>2</sub>O emissions to the atmosphere from Indian monsoonal estuaries

The carbon budget of South Asia

Carbon dynamics and CO&lt;sub&gt;2&lt;/sub&gt; and CH&lt;sub&gt;4&lt;/sub&gt; outgassing in the Mekong delta

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Carbon dynamics and CO<sub>2</sub> and CH<sub>4</sub> outgassing in the Mekong delta