Particulate nitrated aromatic compounds from corn straw burning: Compositions, optical properties and potential health risks

Nitrated aromatic compounds (NACs) are important components of brown carbon (BrC), and their health and climate effects are of wide concern. Biomass burning is a major contributor to NACs in the atmosphere, yet NACs emitted from biomass burning are poorly constrained. In this study particulate NACs from open burning of corn straws were characterized in terms of their compositions, light absorption and toxic equivalents. 1, 6-dinitropyrene was the most abundant species among the measured nitropolycyclic aromatic hydrocarbons (NPAHs) with a share of 13.4% in total NPAHs, while 4-nitrocatechol was the most abundant nitrophenol (NP) species and accounted for 25.4% of measured NPs. 2-nitropyrene, widely used as a marker of secondary formation of NPAHs, was found to be the second most abundant NPAHs (13.3% of the total NPAHs) in the particulate matter (PM) primarily emitted from corn straw burning, and thus is inappropriate to be an indicator of the secondary formation. The measured primary NACs could only explain a negligible part (0.2%) of the light absorption by BrC. Although the concentrations of 9 toxic NACs were less than one-third of the 16 USEPA priority PAHs, their benzo(a)pyrene toxic equivalency quotients however were approximately 10 times that of the 16 PAHs. This study suggests that in comparison of PAHs from straw burning, NACs should be given greater attention due to their potentially higher toxic effects.