Distribution, Flux, Biological Consumption And Photoproduction Of Carbon Monoxide In The East China Sea

Carbon monoxide (CO) can participate in many atmospheric reactions and isconsidered to be a kind of indirect greenhouse gas, which plays an important role inthe global warming and atmospheric chemistry. CO in the surface ocean has beendemonstrated to be supersaturated and the ocean has long been recognized as a naturalsource of atmospheric CO. Although coastal regions only occupy a small part of theworld ocean, they have significant contributions to the atmospheric CO. Therefore,studying the CO biogeochemistry in these areas will be very helpful in estimating COemissions and will be very helpful in understanding CO migration and transformationin marine environment.In this essay, we selected the East China Sea as study areas. The distributions ofCO, sea-to-air fluxes, biological consumption and photoproduction were studied. Themain conclusions were drawn as follows:(1) The distributions of CO were investigated in the East China Sea during June-Julyand October,2012. Atmospheric CO concentrations in summer (87ppbv) weresignificantly lower than those in autumn (146ppbv). Due to the influence ofterrestrial inputs, atmospheric CO concentrations displayed a decreasing trendfrom the coastal stations to the offshore stations. The surface seawater COconcentrations in summer (1.48nmol·L-1) were close to those in autumn (1.68nmol·L-1), and no obvious seasonal variation was showed. The surface water COconcentrations were affected significantly by sunlight. Vertical profiles in thesurveys showed that CO concentrations declined with depth rapidly, with themaximum values appearing in the surface water. Diurnal variation of surfaceseawater CO concentrations was studied at an anchor station in the autumninvestigation. The surface water CO concentrations exhibited obvious diurnalvariation, with the maximum value34folds higher than the minimum value. The maximum concentration of CO was observed in the early afternoon (about14:00)and the minimum concentration of CO was observed before dawn.(2) Sea-surface CO was oversaturated in the East China Sea in summer and autumn.The ocean was a source of atmospheric CO. The oversaturation level in summerwas higher than that in autumn, with the average oversaturation factors were23.63in summer and16.83in autumn. The sea-to-air fluxes of CO in the East China Seawere estimated by the arithmetic of W92. The average flux in summer (9.97μmol·m-2·d-1) was much higher than that in autumn (2.90μmol·m-2·d-1), mainlydue to the higher wind speeds and the higher oversaturation level in summer.(3) Microbial consumption of CO in surface seawater in the East China Sea wasstudied in summer and autumn. The results showed that CO concentrationsdecreased exponentially with incubation time and the processes conformed to thefirst order reaction characteristics. Overall, microbial consumption rates of CO inthe coastal regions were higher than those in the open sea. The average microbialconsumption rate constant of CO in summer (0.18h-1) was higher than that inautumn (0.12h-1). A negative correlation between microbial consumption rateconstants and salinity was observed in the present study.(4) The study of CO photoproduction was conducted in autumn. The apparentquantum yields of CO decreased with increasing wavelength. Using SMARTS2spectral irradiance model, the photoproduction of CO-C in the East China Sea wasestimated to be35.90Gg in autumn.