Determination of Benzo[a]pyrene Diones in Air Particulate Matter with Liquid Chromatography Mass Spectrometry

The formation of the benzo[a]pyrene (B[a]P) diones (B[a]P-1,6-dione, B[a]P-3,6-dione, B[a]P-6,12-dione) as the main products of oxidative degradation of B[a]P has been observed under atmospheric conditions in air particulate matter. Samples were collected at two different sites in Munich, Germany. Total B[a]P dione concentrations were determined by APCI/LC-MS and ranged between 8 and 605 pg m-3. The formation of the direct mutagen B[a]Pepoxide was not observed. B[a]P dione concentrations did not correspond with B[a]P and total carbon concentrations, but showed a correlation with solar irradiation. B[a]P dione concentrations were higher on daytime filters compared to filters collected during the night. Lower concentrations of B[a]P diones were observed at the site with higher traffic contributions, suggesting a major role of atmospheric transport. Rapid, high-volume sampling indicates that the B[a]P dione formation is not dependent on B[a]P concentrations, but on photochemical conditions.