The partial pressure of carbon dioxide and air-sea fluxes in the Changjiang River Estuary and adjacent Hangzhou Bay

The distributions of partial pressure of carbon dioxide (pCO2) in the surface waters of the Changjiang River Estuary and adjacent Hangzhou Bay were examined in the summer of 2010. Surface water pCO2 ranged from 751–2 095 µatm (1 atm=101 325 Pa) in the inner estuary, 177–1 036 µatm in the outer estuary, and 498–1 166 µatm in Hangzhou Bay. Overall, surface pCO2 behaved conservatively during the estuarymixing. In the inner estuary, surface pCO2 was relatively high due to urbanized pollution and a high respiration rate. The lowest pCO2 was observed in the outer estuary, which was apparently induced by a phytoplankton bloom because the dissolved oxygen and chlorophyll a were very high. The Changjiang River Estuary was a significant source of atmospheric CO2 and the degassing fluxes were estimated as 0–230 mmol/(m2·d) [61 mmol/(m2·d) on average] in the inner estuary. In contrast, the outer estuary acted as a CO2 sink.