Abstract
Abstract. Pollution events extracted from the in situ observations of atmospheric CO2 and O2 mixing ratios at Hateruma Island (HAT, 24° N, 124° E) during the period from October 2006 and December 2008 are examined. The air mass origins for the pollution events are categorized by using back trajectory analysis, and the oxidative ratios (OR = −O2:CO2 molar exchange ratio) for selected pollution events are calculated. We find that there is a significant difference in the average oxidative ratios between events from China (OR = 1.14 ± 0.12, n = 25) and Japan/Korea (OR = 1.37 ± 0.15, n = 16). These values are in a good agreement with the national average oxidative ratios for the emissions from fossil fuel burning and cement production (FFBC) in China (ORFFBC = 1.11 ± 0.03) and Korea/Japan (ORFFBC = 1.36 ± 0.02). Compared with the observation, simulations of the atmospheric O2 and CO2 mixing ratios using Lagrangian particle dispersion models do a good job in reconstructing the average oxidative ratio of the pollution events originating in China but tend to underestimate for events originating in Japan/Korea. A sensitivity test suggests that the simulated atmospheric oxidative ratios at HAT are especially sensitive to changes in Chinese fuel mix.
Highlights
There is a tight negative stoichiometric coupling between oxygen (O2) flux and carbon dioxide (CO2) flux of land biotic respiration and photosynthesis processes and burning processes of fossil fuels and biomass
Japan/Korea events is affected by the national ORFFBC of China while it is insensitive to the value of the land biotic exchange ratio
It is consistent with the rather low value of the predicted OR for Japan/Korea. It suggests that the contribution of emissions from China to the pollution events assigned as Japan/Korea is overestimated in the model simulations and about 50 % of fossil fuel burning and cement production (FFBC) CO2 contribution on average comes from China
Summary
There is a tight negative stoichiometric coupling between oxygen (O2) flux and carbon dioxide (CO2) flux of land biotic respiration and photosynthesis processes and burning processes of fossil fuels and biomass. In order to express the quantitative coupling between O2 and CO2, the oxidative ratio is defined as the −O2:CO2 molar exchange ratios: OR = − O2[mol]/ CO2[mol]. Keeling (1988) estimated the oxidative ratios for coal, liquid fuel, and natural gas burning to be 1.17 ± 0.03, 1.44 ± 0.03 and 1.95 ± 0.04, respectively. The estimated global average oxidative ratio for land biotic processes is 1.10 ± 0.05 (Severinghaus, 1995). An analogous stoichiometric coupling between O2 and CO2 fluxes for air-sea gas exchange processes does not exist because oceanic CO2 flux is significantly suppressed by a chemical equilibrium between dissolved CO2, bicarbonate and carbonate ions
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