The Bohai Sea, a semi-enclosed marginal sea under intense anthropogenic pressure, represents a critical yet dynamic component of the regional carbon cycle. However, understanding its fine-scale carbon dynamics has been limited by a lack of long-term, high-frequency observations. This study deployed a moored buoy system in the central Bohai Sea from September 2020 to December 2021 to obtain continuous, high-temporal-resolution measurements of surface seawater pCO2 and key ancillary environmental parameters. An annual stepwise linear regression model (R2 = 0.793, p

Municipal wastewater treatment plants (WWTPs) are important components of urban carbon cycling and have been proposed as potential platforms for ocean alkalinity enhancement (OAE). However, carbonate-system transformations across full-scale treatment processes remain poorly constrained. Here, we present a process-resolved snapshot of total alkalinity (TA), dissolved inorganic carbon (DIC), pH, pCO2, dissolved CH4, and dissolved N2O across five sequential treatment units at a full-scale coastal WWTP in Taiwan. From the influent channel to the chlorination unit, TA and DIC decreased by 94.5% and 84.0%, respectively, accompanied by acidification and persistent CO2 supersaturation. These patterns were consistent with alkalinity consumption during nitrification and DIC transformation associated with aeration and other internal treatment processes. Dissolved CH4 declined markedly following aeration, whereas N2O reached its maximum concentration in the aeration basin and remained elevated in the final effluent. CO2 exchange estimates obtained using conventional wind-based and limited-fetch parameterizations differed substantially from apparent DIC balances between consecutive treatment stages. This divergence highlights the strong methodological uncertainty associated with estimating CO2 exchange in confined and mechanically aerated treatment units. Accordingly, the results are interpreted primarily in terms of observed concentration changes and carbonate-system transformations rather than as definitive emission estimates. The marked chemical differences among treatment stages provide empirical constraints for evaluating where and how alkalinity addition might interact with wastewater treatment processes. Repeated observations, direct gas-flux measurements, and alkalinity mass balances will be required to determine the net carbon-removal potential of wastewater-based OAE.

Miocene Climatic Optimum proxies record high temperatures at moderate pCO2; this cannot be replicated with existing climate models Either previously published records underestimate pCO2 or climate ...