Evidence of coal combustion contribution to ambient VOCs during winter in Beijing

Volatile organic compounds （VOCs） play ,an important role in ozone and secondary organic aerosol （SOA） formation, but VOCs sources during winter are not fully understood. To investigate VOCs sources during winter, mixing ratios of C2-C12 VOCs were measured at an urban site in Beijing from December 29, 2011 to January 17, 2012. Correlation analysis of toluene to benzene and i-pentane to n-pentane suggest that coal combustion could also be an important source for VOCs besides vehicular emissions. Source apportionment results show that coal combustion and vehicular emissions contributed 28%-39% and 31%-45% to ambient VOCs during winter, respectively. Backward trajectory analyses demonstrated that contributions from the burning of coal were higher when air masses came from southern regions outside Beijing. Close attention should be paid to VOCs emissions from coal combustion in Beijing city and the vicinity to the South.

PM_(2.5)-bound polyhalogenated carbazoles(PHCZs)in urban Beijing,China:Occurrence and the source implication

Polyhalogenated carbazoles(PHCZs)are recently raising much attention due to their toxicity and ubiquitous environmental distribution.However,little knowledge is known about their ambient occurrences and the potential source.In this study,we developed an analytical method based on GC-MS/MS to simultaneously determine 11 PHCZs in PM_(2.5) from urban Beijing,China.The optimized method provided low method limit of quantifications(MLOQs,1.45–7.39 fg/m^(3))and satisfied recoveries(73.4%–109.5%).This method was applied to analyze the PHCZs in the outdoor PM_(2.5)(n=46)and fly ash(n=6)collected from 3 kinds of surrounding incinerator plants(steel plant,medical waste incinerator and domestic waste incinerator).The levels of Σ_(11)PHCZs in PM_(2.5) ranged from 0.117 to 5.54 pg/m^(3)(median 1.18 pg/m^(3)).3-chloro-9H-carbazole(3-CCZ),3-bromo-9H-carbazole(3-BCZ),and 3,6-dichloro-9Hcarbazole(36-CCZ)were the dominant compounds,accounting for 93%.3-CCZ and 3-BCZ were significantly higher in winter due to the high PM_(2.5) concentration,while 36-CCZ was higher in spring,which may be related to the resuspending of surface soil.Furthermore,the levels of11PHCZs in fly ash ranged from 338 to 6101 pg/g.3-CCZ,3-BCZ and 36-CCZ accounted for 86.0%.The congener profiles of PHCZs between fly ash and PM_(2.5) were highly similar,indicating that combustion process could be an important source of ambient PHCZs.To the best of our knowledge,this is the first research providing the occurrences of PHCZs in outdoor PM_(2.5).