Pollution Characteristics And Source Analysis Of VOCs In The Yellow Sea Atmosphere In Winter

Volatile organic compounds（VOCs）are trace gases that are ubiquitous in the atmosphere.As important precursors of O₃ and secondary organic aerosols（SOA）,not only can they endanger human health but they also have a particularly prominent impact on air pollution.The Yellow Sea is one of the largest fringe seas in China,it is an important offshore fishing ground and shipping channel;the coastal areas are densely populated and have developed industries.At present,there is a lack of research on VOCs in the YS atmosphere in China,and the pollution characteristics and sources of VOCs in the marine atmosphere are different from those in land areas.Therefore,effective research on VOCs in the marine atmosphere will provide reliable data support and targeted control measures for the prevention and control of atmospheric VOCs pollution in the ocean and coastal areas.In this study,it is the first time to conduct a long-distance ship-based measurement to characterize ambient VOC speciesover the YS by SUMMA canisters sampling,and 103 VOCs were analysed and determined by GC-MS.The pollution level and characteristics of VOCs in the YS atmosphere in winter were analyzed;The ozone formation potential（OFP）and secondary organic aerosol formation potential（SOAp）of VOCs wereestimated by Maximum Incremental Reactivity（MIR）and Fractional Aerosol Coefficient（FAC）;The ratio method and the Positive matrix factorization（PMF）were used to determine the sources of VOCs in the YS atmosphere.The main findings are as follows:（1）The mixing ratio of VOCs in the YS atmosphere was 8.68±6.88 ppbv,the level of VOCs over YS was significantly lower than those in other land areas,of which themixing ratio of alkanes,halogenated hydrocarbons,aromatics,alkenes,and OVOCs were 40.69%,27.17%,22.78%,7.88%,and 0.34%,respectively.The most VOC species in the YS atmosphere was propane;The source of air masses and heavily polluted weather have a significant role in promoting the concentration of VOCs in the YS atmosphere;The VOCs in Dalian Port were mainly affected by the surrounding man-made emissions;The ship emissions make an important contribution to the VOCs in the YS atmosphere;The concentration of VOCs in the atmosphere near the Jiangsu sea is slightly higher than that in north YS.（2）The OFP of VOCs in the YS atmosphere was 71.6μg/m³,the proportion of aromatics,alkanes,alkenes,OVOCs,and halogenated hydrocarbons were 66.35%,21.02%,11.62%,0.52%,and 0.5%,respectively;The top five VOCs contributing to OFP were propylene,1,2,4-trimethylbenzene,m,p-xylene,toluene,and o-xylene;The SOAp of VOCs in YS atmosphere was 0.47μg/m³,aromatics were the main contributors to SOAp in the atmosphere,which accounted for 99.996%of the total contribution rate of the YS atmosphere;The top five VOCs contributing to SOAp in the YS atmosphere were toluene,o-xylene,1,2,4-trimethylbenzene,m,p-xylene,and ethylbenzene;Controlling ship emissions will have a good inhibitory effect on O₃pollution and particulate pollution.（3）The comparative analysis between the ship emissions and the YS atmospheric monitoring showed that the VOCs in the YS atmosphere weremainly dominated by ship emissions;The ratio method showed that the VOCs in YS mainly came from nearby ship emissions;the PMF model was applied to quantitatively analyze the pollution sources of VOCs in the YS atmosphere,a total of 4 pollution factors were distinguished,of which fuel use and volatilization contributed the most to VOCs concentration,which was 43.54%,followed by Ship exhaust emissions（21.92%）,marine emissions and refrigerant use sources（21.52%）and industrial emissions（13.01%）,ship exhaust emissions and fuel use and volatilization can be classified as ship emissions,accounting for approximately 65.46%;The combination of prevention,treatment,management and coordinated control of land and sea arethe key to solving atmospheric VOCs and other pollution problems in oceans and coastal areas.