Chlorinated and brominated polycyclic aromatic hydrocarbons (Cl/Br-PAHs) are halogenated derivatives of polycyclic aromatic hydrocarbons (PAHs). They have the similar structures with dioxins, and have been identified to have toxicities. Cl/Br-PAHs are ubiquitous in the environment. Studies on the characteristics of Cl/Br-PAHs in the
environment are still lacking, one of the reasons is that there are still limitations on the analytical methods. Atmosphere is the major matrice through which Cl/Br-PAHs could transport from one place to another. There are studies on characteristics of Cl/Br-PAHs in atmosphere, but the gas-particle partition and particle size distribution of Cl/Br-PAHs under haze days have not been studied yet. In addition, Cl/Br-PAHs could easily form during thermal processes of industries, but limited studies have identified the sources of Cl/Br-PAHs. With the aim to solve these problems, we established the new method for analysis of Cl/Br-PAHs, studied the characteristics and gas-particle partitions of Cl/Br-PAHs in haze days, and identified new sources of Cl/Br-PAHs. Specific results of the studies are listed as belows:
1. This study established a new isotopic dilution high resolution gas chromatography coupled with high resolution mass spectrometry method for analysis of 19 Cl-PAHs and 19 Br-PAHs in complex environmental samples. The detection limits Cl/Br-PAHs of the method established in this study were two to three orders of magnitude lower than previous method which used the gas chromatography coupled with low resolution mass spectrometry for analysis of Cl/Br-PAHs. A quantitative method for the Cl/Br-PAH homologues was also established in this method. This isotopic dilution GC-HRMS method was applied to analyze 38 Cl/Br-PAHs in air samples and stack gas samples from waste incinerators, recoveries and repeatabilities could meet the requirement for analysis of Cl/Br-PAHs in complex environmental matrices. Among the congeners, 19 Cl/Br-PAH congeners were detected for the first time.
2. Air samples in heating and non-heating period in Beijing were collected and analyzed for the Cl/Br-PAHs. This is the first study which reported the levels, gas-particle distributions and particle size distributions of Cl/Br-PAHs in atmosphere in heating and non-heating period. Concentrations of atmospheric Cl/Br-PAHs in heating period were 3–9 times of those in non-heating period, and the increase of the Cl/Br-PAH concentrations in heating period was mainly brought by the particulate phase. Previous studies reported that Cl/Br-PAHs mainly existed in the gaseous phase,however, in our study, we found the fractions of Cl/Br-PAHs in particulate phase were higher than gas phase in heating period. Particles with sizes of <1 μm, 1–2.5 μm, 2.5–10 μm and >10 μm were collected and analyzed for Cl/Br-PAHs. More than 80% of Cl-PAHs and 70% of Br-PAHs were associated with particles with size lower than 2.5 μm.In addition, Cl/Br-PAHs tended to exist in finer particles in heating period than in non-heating period. Temperature and physicochemical properties of the Cl/Br-PAHs were important influencing factors of the gas-particle distributions and particle size distributions of Cl/Br-PAHs. With the decrease of the temperature and the decrease of vapor pressures, Cl/Br-PAHs tended to be associated with particles of lower diameters.
3. In this study, we analyzed the Cl/Br-PAHs in stack gas and fly ash samples from different stages of secondary cooper smelting processes and cement kiln co-processing solid wastes processes, and identified the secondary cooper smelting and cement kiln co-processing solid wastes as new emission sources of Cl/Br-PAHs. In the stack gases of secondary cooper smelting processes, the concentrations of Cl-PAHs and Br-PAHs were 5.8–271 ng m−3 and 0.59–52.4 ng m−3, respectively. The congener distributions of Cl/Br-PAHs in stack gases from secondary cooper smelting processes were also analyzed, and could be used for establishment of the fingerprints of Cl/Br-PAHs. In addition, we found the chlorination and bromination were not the major formation pathways for Cl/Br-PAHs during secondary cooper smelting processes. In the stack gases of cement kiln co-processing solid wastes, the concentrations of Cl-PAHs and Br-PAHs were 15.6–94.1 ng m–3 and 1.04–4.28 ng m–3, respectively. Kiln end is the major formation zone for Cl/Br-PAHs during cement kiln co-processing solid wastes. Based on the emission factors of Cl/Br-PAHs during secondary cooper smelting and cement kiln co-processing solid wastes, we evaluated the annual emission of Cl/Br-PAHs from these industries. This data was helpful for establishment of the emission inventory of Cl/Br-PAHs.