Polycyclic aromatic hydrocarbons in biomass-burning emissions and their contribution to light absorption and aerosol toxicity

• Published in: The Science of the total environment 2016-10, Vol.568, p.391-401
• Main Authors: Samburova, Vera, Connolly, Jessica, Gyawali, Madhu, Yatavelli, Reddy L.N., Watts, Adam C., Chakrabarty, Rajan K., Zielinska, Barbara, Moosmüller, Hans, Khlystov, Andrey
• Format: Article
• Language: English
• Subjects: Absorption, Physicochemical; Aerosols - chemistry; Aerosols - toxicity; Air Pollutants - chemistry; Biomass; Biomass-burning; Bromus - chemistry; Bromus tectorum; Brown carbon; Fires; Light; Peat smoldering; Pinus ponderosa; Pinus ponderosa - chemistry; Plant Leaves - chemistry; Polycyclic aromatic hydrocarbons; Polycyclic Aromatic Hydrocarbons - chemistry; Potential carcinogen; Soil - chemistry; UV–vis spectra
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2016.06.026

In recent years, brown carbon (BrC) has been shown to be an important contributor to light absorption by biomass-burning atmospheric aerosols in the blue and near-ultraviolet (UV) part of the solar spectrum. Emission factors and optical properties of 113 polycyclic aromatic hydrocarbons (PAHs) were determined for combustion of five globally important fuels: Alaskan, Siberian, and Florida swamp peat, cheatgrass (Bromus tectorum), and ponderosa pine (Pinus ponderosa) needles. The emission factors of total analyzed PAHs were between 1.9±0.43.0±0.6 and 9.6±1.2–42.2±5.4mgPAHkg−1fuel for particle- and gas phase, respectively. Spectrophotometric analysis of the identified PAHs showed that perinaphthenone, methylpyrenes, and pyrene contributed the most to the total PAH light absorption with 17.2%, 3.3 to 10.5%, and 7.6% of the total particle-phase PAH absorptivity averaged over analyzed emissions from the fuels. In the gas phase, the top three PAH contributors to BrC were acenaphthylene (32.6%), anthracene (8.2%), and 2,4,5-trimethylnaphthalene (8.0%). Overall, the identified PAHs were responsible for 0.087–0.16% (0.13% on average) and 0.033–0.15% (0.11% on average) of the total light absorption by dichloromethane-acetone extracts of particle and gas emissions, respectively. Toxic equivalency factor (TEF) analysis of 16 PAHs prioritized by the United States Environmental Protection Agency (EPA) showed that benzo(a)pyrene contributed the most to the PAH carcinogenic potency of particle phase emissions (61.8–67.4% to the total carcinogenic potency of Σ16EPA PAHs), while naphthalene played the major role in carcinogenicity of the gas phase PAHs in the biomass-burning emission analyzed here (35.4–46.0% to the total carcinogenic potency of Σ16EPA PAHs). The 16 EPA-prioritized PAHs contributed only 22.1±6.2% to total particle and 23.4±11% to total gas phase PAH mass, thus toxic properties of biomass-burning PAH emissions are most likely underestimated. [Display omitted] •113 PAHs and PAH derivatives were analyzed in gas and particle phase combustion emissions of five different biomass fuels.•Light absorption properties of individual biomass-burning PAHs were analyzed.•Emission factors of the most effective light absorbing brown carbon PAHs were determined in biomass-emissions.•Benzo(a)pyrene and naphthalene contributed the most to the PAH carcinogenic potency of biomass-burning emissions.