MP3 Heterogeneous Chemistry of Atmospheric Particles and Trace Gases
Monday, 14 November 2005: 8:00 AM - 6:30 PM in Exhibit Hall

(CRI-1117-832055) Sources of Nitro-PAHs to the Baltimore, MD Atmosphere.

Crimmins, B¹, Baker, J¹, ¹ University of Maryland Center for Environmental Science/CBL, Solomons, MD, USA

ABSTRACT- Nitro-substituted polycyclic aromatic hydrocarbons (NPAHs) are of concern in the urban atmosphere due to their direct mutagenic properties. This class of contaminants has primary and secondary sources with specific isomeric compositions. Numerous chamber studies have elucidated the formation products and mechanisms of secondary NPAHs under a variety of conditions. During the Baltimore PM.2.5 Supersite intensives (spring summer and winter 2002-2003), bulk and size-resolved aerosol was collected and analyzed for NPAHs and parent polycyclic aromatic hydrocarbons (PAHs), hopanes and n-alkanes. Co-located measurements of elemental and organic carbon as well as NOx, O3 and PM2.5 were also performed. Six hour integrated bulk aerosol and 12 and 24 hr size resolved PAH and NPAH measurements are employed to assess the dominant sources of primary and secondary NPAHs to the Baltimore atmosphere. Preliminary results show total PAH concentrations (sum of 42) ranged 35 to 200 ng/m3 and with the greatest concentrations on the 0.14 − 0.49 m particle size class. NPAH concentrations ranged 10 to 1000 fold below parent PAH concentrations. The dominant NPAHs found in this study, 2-nitrofluoranthene, 1-ntropyrene and 9-nitroanthracene, exhibited a similar size distribution as the parent PAHs with an enhanced variability from sample to sample. Previously, we have found evidence of possible heterogeneous formation of 2-nitrofluoranthene using 12hr size-resolved analysis. This formation mechanism in the Baltimore samples was explored using 6 hr samples in conjunction with ancillary measurements mentioned above to describe the oxidative conditions, primary combustion sources and PAH distribution prior to photochemical NPAH formation.

Key words: nitrosubstituted polycyclic aromatic hydrocarbons, organic, photochemistry, aerosol