Multi-annual variability of pCO2(aq) and air-water CO2 flux in the mangrove-dominated Dhamra Estuary draining into the Bay of Bengal (India)

• Published in: Environmental science and pollution research international 2023-11, Vol.30 (51), p.111021-111038
• Main Authors: Swain, Sanhita, Pattanaik, Suchismita, Chanda, Abhra, Akhand, Anirban, Sahu, Rabi Narayan, Majhi, Arakshita, Panda, Chitta Ranjan, Satapathy, Deepty Ranjan, Sahoo, Ranajit Kumar, Roy, Rajdeep
• Format: Article
• Language: English
• Subjects: Alkalinity; Annual variations; Aquatic Pollution; Atmospheric Protection/Air Quality Control/Air Pollution; Biogeochemistry; Carbon; Carbon dioxide; Dissolved inorganic carbon; Earth and Environmental Science; Ecotoxicology; Empirical equations; Environment; Environmental Chemistry; Environmental Health; Estuaries; Fluctuations; Mathematical analysis; Monsoons; Research Article; Sampling; Waste Water Technology; Water Management; Water Pollution Control; Wind
• ISSN: 1614-7499; 0944-1344; 1614-7499
• DOI: 10.1007/s11356-023-29986-5

Small estuaries often remain neglected while characterizing air-water CO 2 flux dynamics. This study reports the seasonal, spatial, and multi-annual variability of carbon biogeochemistry, emphasizing air-water CO 2 flux from a small tropical mangrove-dominated estuary (Dhamra Estuary) of the Bay of Bengal, based on the 9-year-long sampling survey (2013 to 2021). The sampling covered twelve pre-fixed locations of this estuary. A suite of biogeochemical parameters was kept within the purview of this study to deliniate the interrelationship between CO 2 fluxes and potential factors that can regulate/govern pCO 2 (aq) dynamics. Air water CO 2 exchange rates were calculated using five globally accepted empirical gas transfer velocity equations and varied in a range of − 832.5 to 7904 μmol m –2 h –1 . The estuary was a sink for CO 2 in monsoon season, having the highest average flux rates of − 380.9 ± 125.5 μmol m –2 h –1 , whereas a source in pre-monsoon (38.29 ± 913.1 μmol m –2 h –1 ) and post-monsoon (91.81 ± 1009.8 μmol m –2 h –1 ). The significant factors governing pCO 2 were pH, salinity, total alkalinity and dissolved inorganic carbon (DIC). This long-term seasonal study emphasizes the need to include small regional estuaries for more accurate estimates of global CO 2 flux to upscale the global carbon budget and its controlling mechanism.