Methyl-nitrocatechols: atmospheric tracer compounds for biomass burning secondary organic aerosols.

Detailed chemical analysis of wintertime PM₁₀ 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 PM₁₀were 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.