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

Area of Science:

• Environmental Chemistry
• Atmospheric Science
• Toxicology

Background:

• Nitrated aromatic compounds (NACs) are key components of brown carbon (BrC) with significant health and climate implications.
• Biomass burning is a primary source of atmospheric NACs, but their emission profiles remain poorly understood.
• Particulate NACs from agricultural waste burning require detailed characterization for accurate risk assessment.

Purpose of the Study:

• To characterize the composition, light absorption, and toxic potential of particulate NACs from open corn straw burning.
• To evaluate the abundance of specific NACs, including nitropolycyclic aromatic hydrocarbons (NPAHs) and nitrophenols (NPs).
• To assess the contribution of primary NACs to brown carbon light absorption and compare their toxic equivalency to polycyclic aromatic hydrocarbons (PAHs).

Main Methods:

• Analysis of particulate matter collected from open corn straw burning.
• Quantification of various NAC species, including NPAHs and NPs, using analytical techniques.
• Measurement of light absorption properties of the emitted BrC.
• Calculation of toxic equivalents (TEQs) for NACs and PAHs using benzo(a)pyrene as a reference.

Main Results:

• 1,6-dinitropyrene was the most abundant NPAH (13.4%), and 4-nitrocatechol was the most abundant NP (25.4%).
• 2-nitropyrene, often considered a marker for secondary formation, was abundant (13.3%), questioning its use as a solely secondary indicator.
• Primary NACs contributed minimally (0.2%) to the light absorption of BrC.
• Despite lower concentrations than PAHs, NACs exhibited benzo(a)pyrene toxic equivalency quotients approximately 10 times higher than PAHs.

Conclusions:

• NACs emitted from corn straw burning are significant and possess high toxicity.
• The abundance of 2-nitropyrene suggests primary emission, challenging its role as a secondary formation marker.
• NACs represent a critical toxicological concern from biomass burning, potentially exceeding that of PAHs.