First in situ estimates of the contribution of nitrated aromatics to wood-burning brown carbon light absorption

 

Authors

Joel Thornton — University of Washington
Claudia Mohr — University of Washington
Felipe Lopez-Hilfiker — University of Washington
Lu Xu — Georgia Institute of Technology
Nga Lee Ng — Georgia Institute of Technology
Scott C Herndon — Aerodyne Research, Inc.
Leah R Williams — Aerodyne Research Inc
Jonathan P Franklin — Aerodyne Research, Inc.
Mark Stuart Zahniser — Aerodyne Research, Inc.

Walter Berkett Knighton — Montana State University
Allison C Aiken — Los Alamos National Laboratory
Kyle Gorkowski — Los Alamos National Laboratory
Manvendra K. Dubey — Los Alamos National Laboratory

Category

Aerosol Properties

Description

We show for the first time quantitative in situ measurements of five nitrated aromatic (NA) compounds in ambient air (nitrophenol C6H5NO3, methylnitrophenol C7H7NO3, nitrocatechol C6H5NO4, methylnitrocatechol C7H7NO4, and dinitrophenol C6H4N2O5) measured with a micro-orifice volatilization impactor (MOVI) high-resolution chemical ionization mass spectrometer in Detling, UK, during winter time. NA absorb radiation in the near-ultraviolet (UV) range of the electromagnetic spectrum and thus are among the high number of poorly constrained compounds of light-absorbing organic matter (“brown carbon”), affecting climate and air quality. Total concentrations varied between less than 1 and 98 ng m-3, with a mean value of 20 ng m-3. We conclude that NA measured in Detling have a significant contribution from biomass burning with an estimated emission factor of 0.2 ng (ppb CO)-1. Particle light absorption measurements by a 7-wavelength aethalometer in the near-UV (370 nm) and literature values of molecular absorption cross sections are used to estimate the contribution of NA to wood-burning brown carbon UV light absorption. We show that these five NA are potentially important contributors to absorption at 370 nm measured by an aethalometer and account for 6±3% of UV light absorption by brown carbon. They can thus affect atmospheric radiative transfer and photochemistry and with that climate and air quality.