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 estuary mixing. 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. Key words:carbon dioxide, air-sea flux, Changjiang River Estuary, Hangzhou Bay.