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| Abstract Submission No. | ABS-2022-07-0400 |
| Title of Abstract | Spatial and seasonal variation of pCO2 and air-sea CO2 flux in the Devi estuary, east coast of India |
| Authors | Shaheen Akhtar*, Sk. Md. Equeenuddin, Fakira Bastia |
| Organisation | National Institute of Technology, Rourkela |
| Address | Department of Earth and Atmospheric Sciences, National Institute of Technology Rourkela, Odisha, India Pincode: 769008 Mobile: 8596054544 E-mail: shaheen.nitrkl@gmail.com |
| Country | India |
| Presentation | Oral |
| Abstract | Estuaries act as an important land-ocean transition zone where complex biogeochemical processes commonly lead to a super-saturation of CO2. The CO2 super-saturation makes them significant emitters of this trace gas to the atmosphere via air-sea exchange. Globally, total CO2 emission from estuaries is estimated to be in the range of 0.27 to 0.50 Pg C yr-1. This counteracts for about 21% of the total uptake of CO2 by the continental shelf. Thus, the large estuarine emission or efflux rates of CO2 cause them to play a significant role in the global carbon budget. Moreover, the rate of CO2 flux mostly depends on temperature, wind speed and depth of water. Therefore, a wide variability in CO2 flux has been observed depending on the environmental setup in an estuary. To address this inconsistency, it is important to estimate the pCO2 and CO2 fluxes in different major and minor estuaries on a spatial and temporal scale. Also, the dynamic nature of these coastal areas challenges the accurate estimation of pCO2 and CO2 flux. Considering this variability, a complete database of representative estuaries is necessary for the accurate estimation of the global estuarine CO2 emission and net carbon budget evaluation. This study aims to present data on the spatial and seasonal variability of pCO2 and CO2 flux along with their various controlling factors in the Devi river estuary formed by a major distributary of the Mahanadi River draining into the Bay of Bengal. The average surface water pCO2 in the Devi river estuary is estimated to be 1565 ± 782 μatm, which is higher than that of the atmosphere (400 μatm). Such a high pCO2 is attributed to intense organic matter decomposition that suggests a net heterotrophic environment prevailing in the estuary. Seasonal variation of pCO2 is significant having the highest pCO2 in winter (2071 ± 828 μatm) and lowest during monsoon (951 ± 316 μatm). This super-saturation of pCO2 makes this estuary a significant source of CO2 to the atmosphere with an annual flux of 40.1 ± 7.5 mol C m-2 yr-1. A contrast in seasonal variation of CO2 flux is observed in the estuary as a result of differences in wind speed and temperature of water. These variables have led to higher CO2 flux in the summer season (126±69 mmol C m-2 d-1) in comparison to that of the winter (112±64 mmol C m-2 d-1) in spite of having lower pCO2. The net annual flux from the estuary contributes about 0.003 to 0.006% of the global estuarine CO2 emission. Therefore, this study shows the importance of small-scale estuaries in the global carbon budget, and highlights the role of various local-scale atmospheric factors in controlling the pCO2 and its flux to the atmosphere. |