Methyl-Nitrocatechols: Atmospheric Tracer Compounds for Biomass Burning Secondary Organic Aerosols

Detailed chemical analysis of wintertime PK10 collected at a rural village site in Germany showed the presence of a series of compounds that correlated very well with levoglucosan, a known biomass burning tracer compound. Nitrated aromatic compounds with molecular formula C7H7NO4 (M-w 169) correlated particularly well with levoglucosan, indicating that they originated from biomass burning as well. These compounds were identified as a series of methyl-nitrocatechol isomers (4-methyl-5-nitrocatechol, 3-methyl-5-nitrocatechol, and 3-methyl-6-nitrocatechol) based on the comparison of their chromatographic and mass spectrometric behaviors to those from reference compounds. Aerosol chamber experiments suggest that m-cresol, which is emitted from biomass burning at significant levels, is a precursor for the detected methyl-nitrocatechols. The total concentrations of these compounds in the wintertime PM10 were as high as 29 ng m(-3), indicating the secondary organic aerosol (SOA) originating from the oxidation of biomass burning VOCs contributed non-negligible amounts to the regional organic aerosol loading.