| Based on two types of Cavity Ring-Down Spectrometers(CRDS),a ship-based continuous observation system was integrated for the first time measurement of atmospheric carbon dioxide(CO2),methane(CH4),carbon monoxide(CO)and nitrous oxide(N2O)during a cruise of the survey vessel Dongfanghong II on the Yellow Sea and the East China Sea in the spring of 2017,to make up the gap in atmospheric trace gses observed over China Seas,and it makes significant sense for greenhouse gases observation research over China Seas.The results of laboratory tests showed that the accuracies of CO2,CH4,CO and N2 O were better than 0.13 ?mol·mol-1?0.24 nmol·mol-1?1.4 nmol·mol-1?1.4 nmol·mol-1 respectively and the precision of them was better than 0.07 ?mol·mol-1?0.12 nmol·mol-1?1.7 nmol·mol-1?0.2 nmol·mol-1.The practice has proved that the system is stable and easy to operate.The high-frequency and high-precision atmospheric CO2,CH4,CO and N2 O mole fraction data in sea surface have been obtained during the survey voyage.A set of ship-based protocols for system operation and data processing were preliminarily developed for obtaining internationally comparable data.The range of atmospheric CO2,CH4,CO and N2 O mole fraction over the Yellow Sea and the East China Sea in spring were(409.5-526.9)?mol·mol-1,(1885.9-2085.6)nmol·mol-1,(111.2-607.6)nmol·mol-1,(332.1-342.7)nmol·mol-1,with averages of(421.7 ± 5.6)?mol·mol-1,(1954.4 ± 2.1)nmol·mol-1,(247.0 ± 13.3)nmol·mol-1,(333.5 ± 0.2)nmol·mol-1 respectively.The spatial variations of the mole fraction of the four trace gases were very similar.During the 2017 spring campaign,the mole fraction of sulfur hexafluoride(SF6)was measured as a tracer by discrete air samples collection and gas chromatography in the laboratory,totally 20 samples.The range of the mole fraction of SF6 was(9.5—14.0)×10-12 mol·mol-1,with an average value of(10.5 ± 1.3)×10-12 mol·mol-1,and showed significant variations with the distance away from the land,with higher value closer to the land.There were two areas with high mole fraction of SF6,respectively the northeast and southeast of East China Sea.However,the low mole fraction of SF6 was observed in the south of the Yellow Sea,the northwest and southeast of East China Sea.The distribution characteristics of the mole fraction of SF6 was similar with that of CO2,CH4,CO and N2 O.Based on the back trajectory simulations,the high mole fraction of SF6 may be induced directly by short distance and low altitude land-sea air transport from Korea and southeast part of China mainland where the human activities are intensive.The emission sources of these gases were divided into ten regions by using the NOAA HYSPLIT model.The distribution of the mole fractions of atmospheric CO2,CH4,CO and N2 O over the Yellow Sea and the East China Sea in the spring was mainly caused by the emissions from Eastern China,then the ratios of the mole fraction enhancements between every pair of trace gases downwind of these source areas were calculated to understand the distribution characteristics.The much higher enhancement ratio of ?CO/?CO2 and the lower ratio of ?CH4/?CO observed in the air parcels from big cities like Beijing and Shanghai indicated high CO emission from the cities during our time of observation.Compared with the values of NOAA's Marine Boundary Layer(MBL),the ratios of the averages in the air that stayed over the Yellow Sea and the East China Sea was a mixture of emissions from wide regional areas.The highly variable N2 O data of the air from Qingdao and Shanghai showed much more fluctuation.In the future,survey voyages in different seasons could be carried out for more systematic and in-depth analysis and reseach. |
PDF Full Text Request