Source differences in the components and cytotoxicity of PM_2.5 from automobile exhaust, coal combustion, and biomass burning contributing to urban aerosol toxicity

Abstract. The combustions of fuels, including oil, coal, and biomass, are main anthropogenic sources of atmospheric fine particulate matters (PM_2.5), however, their discrepant contributions to health toxicity risks of mixed ambient aerosol pollution dominated by respective emission intensity and chemical compositions are still unclear. In order to explore the quantitative differences of these combustion emissions, ten typical types of each source PM_2.5, i.e., vehicle exhaust, coal combustion, and biomass burning, were collected by laboratory simulated combustion and dilution channel sampler. Totally thirty type combustion samples were compared with monthly urban air PM_2.5 samples, which chemical characteristics and biological effects were investigated by component analysis and in vitro toxicity assays of human lung epithelial cells (A549). Heavy metals are more plentiful in PM_2.5 from coal combustion and automobile exhaust, while carbonaceous fraction was plenteous in biomass burning. The overall cytotoxicity of PM_2.5 was automobile exhaust > coal combustion > biomass burning, with different toxicity pathways and triggers. The toxicity of PM_2.5 from gasoline/diesel and biomass combustion was relevant to the combination of carbonaceous and water-soluble components, but the toxicogenic capacity of coal combustion PM_2.5 was mainly related to the high content of heavy metals. All these three emission categories of anthropogenic combustion sources were more toxic than ambient PM_2.5 and should be the main independent contributors to the cytotoxicity of mixed urban air PM_2.5. Associated with the source apportionment results of positive matrix factorization (PMF) model that automobile exhaust, coal and biomass combustion contributed 27.7 %, 25.2 % and 13.1 % of ambient air PM_2.5, respectively, the toxicological results suggest automobile exhaust and coal combustion are priority emissions with higher toxic pollutants to be reduced preferentially for precise urban PM_2.5 pollution control ensuring public health safety.