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).