Light absorption of secondary organic aerosol: Composition and contribution of nitro-aromatic compounds
Citation:
Xie, M., X. Chen, M. Hays, M. Lewandowski, J. Offenberg, Tad Kleindienst, AND A. Holder. Light absorption of secondary organic aerosol: Composition and contribution of nitro-aromatic compounds. ENVIRONMENTAL SCIENCE & TECHNOLOGY. American Chemical Society, Washington, DC, 51(20):11607-11616, (2017).
Impact/Purpose:
Secondary organic aerosol may affect the atmospheric radiation balance through absorbing light in the short visible and UV wavelength range. However, the optical properties of secondary organic aerosol is poorly understood. This work seeks to identify the absorption properties of secondary organic aerosols from anthropogenic precursor volatile organic compounds and link these properties to the chemical composition of the aerosol.
Description:
Secondary organic aerosol (SOA) might affect the atmospheric radiation balance through absorbing light at shorter visible and UV wavelengths. However, the composition and optical properties of light-absorbing SOA is poorly understood. In this work, SOA filter samples were collected during individual chamber experiments with three biogenic and eight aromatic volatile organic compound (VOC) precursors in the presence of NOX and H2O2. Compared with the SOA generated using the aromatic precursors, biogenic SOA in general exhibits negligible light absorption above 350 nm; the aromatic SOA generated in the presence of NOX showed stronger light absorption than that generated with H2O2. Fifteen nitro-aromatic compound (NAC) chemical formulas were identified and quantified in SOA samples. Their contributions to the light absorption of sample extracts were also estimated. On average, the m-cresol/NOX SOA sample has the highest mass contribution from NACs (10.4 ± 6.73%, w/w), followed by naphthalene/NOX (6.41 ± 2.08%) and benzene/NOX (5.81 ± 3.82%) SOA. The average contributions of NACs to total light absorption were more than two times higher than their average mass contributions at 365 and 400 nm, revealing the potential application of NACs as brown carbon (BrC) tracers and chromophores in further source apportionment and air quality modeling studies.
