Distribution, Flux And Biological Consumption Of Carbon Monoxide In The Eastern Continental Seas Of China

Carbon monoxide (CO), one of the most important prevalent trace gases in the troposphere, can participate in many atmospheric reactions and plays an important role in the global warming and atmospheric chemistry. The ocean has long been recognized as an important natural source of atmospheric CO, especially in coastal waters. Therefore, the study of CO biogeochemical cycle in the ocean will be very useful in estimating CO emissions and plays a significant role in understanding CO migration and transformation in marine environment.In the dissertation, we selected the East China Sea (ECS), Bohai Sea (BS) and Yellow Sea (YS) as study areas. The CO distribution, sea-to-air fluxes and biological consumption were studied.1. The distributions of CO were studied in the ECS and south YS during July 2013. The main conclusions were drawn as flows:(1) Atmospheric CO mixing ratios varied from 68 ppbv-448 ppbv, with an average of 117 ppbv. Overall, under the influence of terrestrial inputs, the concentrations of atmospheric CO presented a reduce trend from the inshore stations to the offshore stations. Comparing with the results of investigation of the other seasons in the ECS and south YS, the atmospheric CO concentration displayed seasonal variation. The surface water CO concentrations in the investigated area ranged from 0.23-7.10 nmol·L-1, with an average of 2.49 nmol·L-1 (SD=2.11. n=36). The surface water CO concentrations were affected significantly by sunlight and the terrestrial inputs. The concrete manifestation was:surface water CO concentrations presented a reduce trend from the inshore stations to the offshore stations; the surface water had obvious diurnal variation, the maximum concentration of CO was observed in the early afternoon and the minimum concentration of CO was observed before dawn. Comparing with the results of investigation of the other seasons in the ECS and south YS, the surface water CO concentration displayed seasonal variation. Vertical profiles in the surveys showed that CO concentration declined with depth rapidly, with the maximum values appearing in the surface water. CO concentration changes did not show the correlation with chlorophyll-a.(2) Surface water CO was oversaturated in the ECS and south YS. The ocean was a source of atmospheric CO, with the average oversaturation factors were 29.36. Comparing with the results of investigation of the other seasons, oversaturation factors displayed seasonal variation. The sea-to-air fluxes of CO in the ECS and south YS were estimated by the arithmetic of W92, with an average of 12.73 umol·(m2·d)-1. The sea-to-air fluxes were influenced significantly by wind speeds and oversaturation level, which also displayed seasonal variation.(3) Microbial consumption of CO in surface seawater in the ECS and south YS, with the results showed that CO concentrations decreased exponentially with incubation time and the processes conformed to the first order reaction characteristics. The microbial CO consumption rate constants in the surface water (kbio) ranged from 0.12 to 1.45 h-1, with an average of 0.47 h-’. A negative correlation between microbial consumption rate constants and salinity was observed in the study. But the relationship between microbial consumption rate constants and chlorophyll-a was not obivious.2. The distribution of CO were studied in the YS and BS during November,2013. The main conclusions were drawn as flows:(1) Atmospheric CO mixing ratios varied from 125 ppbv to 2128 ppbv, with an average of 460 ppbv. Overall, under the influence of terrestrial inputs, the concentrations of atmospheric CO presented a reduce trend from the inshore stations to the offshore stations. Comparing with the results of investigation of the other seasons in the YS and BS, the atmospheric CO concentration displayed seasonal variation. This phenomenon is consistent with the results of the ECS and south YS. The surface water CO concentrations in the investigated area ranged from 0.34 to 6.26 nmol·L-1. with an average of 1.34 nmol·L-1 The investigation of diurnal variation also indicated the CO concentration also influenced by the sunlight. Vertical profiles in the surveys showed that CO concentration declined with depth rapidly, with the maximum values appearing in the surface water. While there were also individual positions, the maximum values appearing in the subsurface water (10 m). CO concentration changes did not show the correlation with chlorophyll-a.(2) Undersaturation was observed at 9 of the 28 stations measured and the average saturation factor was 6.37. Overall, the study area was a source of atmospheric CO. The sea-to-air fluxes of CO in the YS and BS were estimated by the arithmetic of W92, with an average of 12.73 μmol·(m2·d)-1. The sea-to-air fluxes were also influenced significantly by wind speeds and oversaturation level, which displayed seasonal variation.(3) In the incubation experiments, CO concentrations decreased exponentially with incubation time and the processes conform to the first order reaction characteristics. The microbial CO consumption rate constants in the surface water (kbio) ranged from 0.10 to 0.31 h-1,with an average of 0.20 h-1. The relationship between microbial consumption rate constants and chlorophyll-a was not obivious.