Thermochemical formation of multiple unintentional persistent organic pollutants on metallurgical fly ash and their correlations

摘要

Metallurgical processes are currently the predominant anthropogenic sources of multiple unintentional persistent organic pollutants (POPS), including polycyclic aromatic hydrocarbons (PAHs), chlorinated and brominated PAHs (Cl-PAHs and Br-PAHs), polychlorinated biphenyls (PCBs), polychlorinated naphthalenes (PCNs), and polybrominated diphenyl ether (PBDEs). Understanding the formation of multiple POPs is important for source control. These POPs could be formed through fly ash-mediated heterogeneous reactions. In this study, we comprehensively investigated the thermochemical (150-450 degrees C) formation of these POPs on fly ash samples collected from a secondary aluminum smelter, secondary lead smelter, and iron ore sintering plant. The maximum concentrations of PCNs and PCBs were 154.5 and 181.3 times those in the original fly ash, respectively. Formation variations of PAHs, Cl-PAHs and Br-PAHs, and PBDEs were different from that of PCBs and PCNs. The PAHs concentration, which was the highest among the POPs in the original fly ash, decreased sharply by 95% at 150 degrees C. The Sigma Cl-19-PAHs and Sigma Br-19-PAHs increased marginally at 250 degrees C before decreasing slightly at 350 degrees C. The PBDE concentrations decreased under 250 degrees C and increased at 350 degrees C. PCNs, PCBs, and PCDD/Fs showed good correlations, all of which had a negative relationship with the PAHs. There were no significant correlations between PAHs and Cl/Br-PAHs. Low brominated congeners could be formed by destruction of higher brominated congeners because of thermal instability of the PBDEs. (C) 2019 Elsevier Ltd. All rights reserved.