摘要
Estuaries are often a significant source of atmospheric CO_(2).However,studies of carbonate systems have predominantly focused on large estuaries,while smaller estuaries have scarcely been documented.In this study,we collected surface and bottom seawater carbonate samples in the subtropical Jiulong River Estuary across different tidal levels from 2019 to 2021.The results showed that estuarine mixing of freshwater from the river with seawater was the dominant factor influencing the estuarine carbonate system.Moreover,estuarine mixing is concomitantly impacted by the net metabolism of biological production and decomposition,groundwater input,release of CO_(2)from the estuary,and precipitation or dissolution of calcium carbonate.The estuarine partial pressure of CO_(2)(pCO_(2))varied from 530μatm to 7715μatm,which represents a strong source of atmospheric CO_(2).The mean annual air-sea CO_(2)flux estimated from three different parameterized equations was approximately(25.63±10.25)mol/(m2·a).Furthermore,the annual emission to the atmosphere was approximately(0.031±0.012)Tg C,which accounts for a mere 0.0077%−0.015%of global estuarine emissions.Dissolved inorganic carbon(DIC),total alkalinity(TA)and the pCO_(2)exhibited high variability throughout the tidal cycle across all cruises.Specifically,the disparities observed between DIC and TA during low and high tides at identical stations during all cruises ranged from approximately 15%to 30%.The variance in the pCO_(2)was even more pronounced,ranging from approximately 30%to 40%.Thus,tidal discrepancies may need to be taken into consideration to estimate the CO_(2)flux from estuarine systems more accurately.
基金
The Scientific Research Foundation of Third Institute of Oceanography,MNR under contract Nos.2022001,2020017,2023008 and 2019018
the Natural Science Foundation of Fujian Province of China under contract No.2023J01209
the National Natural Science Foundation of China under contract No.4237061213
the Fujian Science and Technology Innovation Leader Project.
