China is experiencing severe carbonaceous aerosol pollution driven mainly bylarge emissions resulting from intensive use of solid fuels. To gain abetter understanding of the levels and trends of carbonaceous aerosolemissions and the resulting ambient concentrations at the national scale, weupdate an emission inventory of anthropogenic organic carbon (OC) andelemental carbon (EC) and employ existing observational studies to analyzecharacteristics of these aerosols including temporal, spatial, and sizedistributions, and the levels and shares of secondary organic carbon (SOC)in total OC. We further use ground observations to test the levels andinter-annual trends of the calculated national and provincial emissions ofcarbonaceous aerosols, and propose possible improvements in emissionestimation for the future. The national OC emissions are estimated to haveincreased 29 % from 2000 (2127 Gg) to 2012 (2749 Gg) and EC by 37 %(from 1356 to 1857 Gg). The residential, industrial, and transportationsectors contributed an estimated 74–78, 17–21, and 4–6 % of thetotal emissions of OC, respectively, and 49–55, 30–34, and 14–18 %of EC. Updated emission factors (EFs) based on the most recent local fieldmeasurements, particularly for biofuel stoves, led to considerably loweremissions of OC compared to previous inventories. Compiling observationaldata across the country, higher concentrations of OC and EC are found innorthern and inland cities, while higher OC / EC ratios are found in southernsites, due to the joint effects of primary emissions and meteorology.Higher OC / EC ratios are estimated at rural and remote sites compared tourban ones, attributed to more emissions of OC from biofuel use, morebiogenic emissions of volatile organic compound (VOC) precursors to SOC,and/or transport of aged aerosols. For most sites, higher concentrations ofOC, EC, and SOC are observed in colder seasons, while SOC / OC is reduced,particularly at rural and remote sites, attributed partly to weakeratmospheric oxidation and SOC formation compared to summer. Enhanced SOCformation from oxidization and anthropogenic activities like biomasscombustion is judged to have crucial effects on severe haze eventscharacterized by high particle concentrations. Several observational studiesindicate an increasing trend in ambient OC / EC (but not in OC or ECindividually) from 2000 to 2010, confirming increased atmospheric oxidationof OC across the country. Combining the results of emission estimation andobservations, the improvement over prior emission inventories is indicatedby inter-annual comparisons and correlation analysis. It is also indicated,however, that the estimated growth in emissions might be faster thanobserved growth, and that some sources with high primary OC / EC, such as burningof biomass, are still underestimated. Further studies to determine changingEFs over time in the residential sector and to compare to othermeasurements, such as satellite observations, are thus suggested to improveunderstanding of the levels and trends of primary carbonaceous aerosolemissions in China.
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