| Carbonaceous aerosol is an important part of particles in the atmosphere.A detailed emission inventory of carbonaceous aerosols in China and a comprehensive analysis on sources,levels,and spatial and temporal distribution of carbonaceous aerosols based on ground observation are helpful to understand the pollution characteristics and to make appropriate control measures for carbonaceous aerosols.To gain a better understanding of the levels and trends of carbonaceous aerosol emissions and the resulting ambient concentrations at the national scale,we update an emission inventory of anthropogenic organic carbon(OC)and elemental carbon(EC),and employ existing observational studies to analyze temporal and spatial distributions of these aerosols.We further use ground observations to test the levels and inter-annual trends of the calculated national and provincial emissions of carbonaceous aerosols,and propose possible improvements in emission estimation for the future.Due to the economic and energy consumption growth,the national OC emissions are estimated to grow by 29%from 2000 to 2012,while elemental carbon EC emission by 37%.The residential sector is the largest emissions department,which contribute about 76%and 52%of total OC and EC emissions.Compiling observational data across the country,high OC and EC concentrations are found in northern and inland cities,while higher OC/EC and secondary organic carbon(SOC)in total OC are found in the southern cities.Clear differences are found in urban,rural and remote sites,implying the contribution of anthropogenic sources.In northern cities,OC comes largely from anthropogenic emissions.Due to the large use of biomass fuels,natural source emissions and aged aerosols,SOC/OC at rural and remote sites are significantly higher than that in urban areas.For most sites,OC,EC and SOC concentrations show much higher concentrations in winter compared to that in summer,while the seasonal variation of SOC/OC is smaller,particularly at rural/remote sites,attributed partly to stronger atmospheric oxidation and SOC formation in summer.During 2000-2010,the emissions of OC and EC are estimated to increase and this is inconsistent of the trends of observed concentrations.The inconsistence might be attributed to insufficient consideration of changed emission factors of residential sector,as well as the uncertainty from different analytical methods in carbonaceous aerosols and inter-annual variability of meteorology.Combining the results of emission estimation and observations,the improvement over prior emission inventories is indicated by inter-annual comparisons and correlation analysis.It is also indicated,however,that some sources with high primary OC/EC like burning of biomass are still underestimated in rural area.Based on the analysis of carbonaceous aerosols pollution characteristics and evaluation of the emissions on the national scale,continuous measurements of carbonaceous aerosols are conducted in a highly polluted city caused by economic development-Nanjing.The measurement provides long-term data of carbonaceous aerosol concentrations with high temporal resolution,and the pollution characteristics during typical periods and transport mechanisms are further analyzed.The sampling and analytical methods have influence on the measured carbonaceous levels.Thermal EC is clearly higher than that of optical EC,but good correlation is found for the two datasets.The OC/EC ratio from thermal analytical method is significantly lower than those of most other cities across the country.Carbonaceous aerosol concentrations are higher during winter than those in summer,indicating the emission and meteorology changes.Both OC and EC concentrations are higher at night compared to that in daytimes,attributed to the changed anthropogenic activities and height of boundary layer.Clear morning peak in OC and EC is found for all the seasons expect summer.Diurnal variation of OC/EC and the correlation between carbonaceous aerosols and other gaseous pollutants suggest that traffic sector is a major source of local carbonaceous aerosols.The contribution of SOC to OC is not significant with an average value at 28%.The highest SOC/OC is found in summer reaching 43%.Biomass burning are estimated to have an impact on seasonal OC-EC correlations.Analysis for typical periods also implies that human activities and emission controls have a significant impact on the carbonaceous aerosol concentrations.For example,biomass burning is estimated to account for 49.1%of total OC emissions during harvest time.Due to specific emission controls,the OC and EC concentrations during Youth Asian Games(16-24,Aug,2013)decreased by 21%and 10%compared to rest days in August 2013,respectively.Increased OC/EC as PM2.5 level rose implies that SOC formation has an important influence on the heavy pollution days. |
PDF Full Text Request