Atmospheric emission and cycling of carbonmonoxide in the Scheldt Estuary

Axial profiles of dissolved carbon monoxide(CO) from four surveys of the Scheldt estuaryconfirmed that the estuary is a source ofatmospheric CO, with an emission range of 4-404nmol m^sup -2^ h^sup -2^. Surface water COconcentration and atmospheric emission werespatially variable, with an order of magnitudedifference between the upper and lower estuaryin spring, and seasonally variable with highestlevels in spring and lowest in winter. AnnualCO emission was estimated to be 700 (396-1032)× 10^sup 3^ mol, equivalent to 0.02-0.05% ofdissolved organic carbon (DOC) input to theestuary. CO photoproduction rates were an orderof magnitude greater in the upper estuary inspring and correlated with DOC concentration.Total CO production from DOC photodegradationwas estimated to be 8.5-18 × 10^sup 3^ mol COd^sup -1^, equivalent to 0.21-0.44% of riverineDOC input in spring. The deficit betweenproduction and emission suggests that microbialCO oxidation accounts for 68% of photoproducedCO, with highest oxidation rates at lowsalinities. The results indicate that suspendedparticulate material indirectly influencesestuarine CO distribution and emission.Assuming that the Scheldt is representative, estuaries do notcontribute significantly to the oceanic or global CO budgets.[PUBLICATION ABSTRACT]