The Influence Of Gas Flaring On Black Carbon In The Arctic And Its Implication For Radiative Effect

Black carbon（BC）aerosol can either directly absorb solar radiation or change surface albedo after deposited onto snow and contribute to arctic warming.However,the current researches have great uncertainties on the source,emissions and climate effects of Arctic BC,and the uncertainty of BC inventory emissions is one of the main uncertainties.For example,the gas flaring emission,which is a way to treat extra gas by high temperature oxidation.Its contribution to global BC emissions is very low（3%）,but its contribution to BC in the arctic is significant.Gas flaring was not included in emission inventory for BC until 2010.Based on these problems,the goal of this research is to explore the sources and the associated seasonality of BC concentration in the arctic,estimate the contribution of gas flaring to arctic BC,and estimate BC deposition on to the arctic snow and its implications for climatic effects in the arctic.We used the GEOS-Chem（a global chemical transport model）to interpret long-term surface observations of BC concentrations at 4 arctic sites（Alert,Barrow,Zeppelin and Tiksi）in 2013-2015.Biomass burning inventory（QFED）and different anthropogenic inventory（HTAP,ECLIPSE and ECLIPSE+flr）were used for the simulation.By comparison,the simulation result of ECLIPSE+flr was found to the best emission inventory to reproduce surface observations in the arctic.In the results of ECLIPSE+flr,the main source of BC on the arctic surface is Russia anthropogenic in winter,Russia anthropogenic and open fire in spring,open fire in summer,and Russia anthropogenic in autumn.The main sources of column BC in the arctic are Asia anthropogenic and Russia anthropogenic in winter,open fire and Asia anthropogenic in spring,open fire in summer,and Asia anthropogenic and open fire in autumn.Due to anthropogenic emissions in Russia and Europe,the largest deposition area of BC in the arctic winter is the Eurasian area.BC deposition in spring and autumn is mainly from the European anthropogenic emissions,Russian anthropogenic emissions and open fire emissions.While in summer,it is mainly from the open fire.The average snow albedo of the arctic region reduced by BC deposited in snow and ice was 0.4%in winter and0.6%in spring from 2013 to 2015,resulting in surface radiation forcing of 0.1 W m^-2in winter and 1.3 W m^-2 in spring.In the arctic,gas flaring is an important source for BC.In winter,the relative contributions of gas flaring to surface BC in arctic station were 19%at Alert,25%at Barrow,22%at Zeppelin and 25%at Tiksi,respectively.The relative contribution of gas flaring to surface BC in the whole arctic domain is 18-22%in the whole year,and in winter is 26-30%,in spring is 18-23%,in autumn is 26-30%.The contribution of gas flaring to Russian anthropogenic sources is significant,about 34-45%.In the spring,the snow albedo decreased by 0.1%due to the BC emitted by the gas flaring in the arctic,resulting in a surface radiation forcing of 0.1 W m^-2.