Spatial and temporal variation, source identification, and toxicity evaluation of brominated/chlorinated/nitrated/oxygenated-PAHs at a heavily industrialized area in eastern China

Some derivatives of polycyclic aromatic hydrocarbons (PAHs) such as chlorinated and brominated PAHs (Cl/BrPAHs), nitrated and oxygenated PAHs (N/OPAHs) have attracted significant concern due to their high toxicity. Knowledge of the profiles, formation mechanisms, and potential sources of these toxic chemicals near the industrial complexes is essential for their pollution control and management. In this study, we monitored Cl/BrPAHs, N/OPAHs, and PAHs at 24 sampling sites near a heavily industrialized area (steel, chemical, and rubber plants) using passive air samplers during the heating period (7 December 2019 to 15 April 2020) and the non-heating period (2 June 2020 to 4 October 2020). The total average concentrations of 16 BrPAHs, 8 ClPAHs, 17 NPAHs, 6 OPAHs, and 18 PAHs during both sampling periods were 471 pg/m(3), 229 pg/m(3), 312 pg/m(3), 2120 pg/m(3), and 63.1 ng/m(3), respectively. Except for NPAHs, BrPAHs, ClPAHs, OPAHs, and PAHs all showed higher levels during the heating period. The spatial distributions of Cl/BrPAHs, N/OPAHs, and PAHs exhibited a similar pattern, with the highest concentrations detected in the vicinity of the steel industry. Congener profiles of PAH derivatives indicated that mono-substituted low molecular weight compounds (2-3 rings) were dominant. The major formation mechanisms of halogenated PAHs were discussed by correlation analysis and relative Gibbs free energies, and direct bromination of parent PAHs could be the major formation mechanism of BrPAHs in this study. Diagnostic ratios showed that NPAHs were mainly derived from primary emissions, but the contribution of secondary formation was increased at heavily contaminated sites. The positive matrix factorization model extracted four Cl/BrPAHs, three N/OPAHs, and four PAHs factors, and the result showed that PAHs and their derivatives mainly derived from industrial and combustion sources, photochemical reactions, vehicle emissions, and crude oil volatilization, etc.

Automated summary

The pollution levels and spatial distributions of derivatives of polycyclic aromatic hydrocarbons (PAHs) near industrial complexes were monitored and their formation mechanisms and sources were discussed. The concentrations of these toxic chemicals were higher during the heating period and mainly originated from industrial and combustion sources, with the steel industry being the major contributor.