PT05 Atmospheric Transport and Fate
Exhibit Hall
8:00 AM - Tuesday
(PT065) Nitro-substituted polycyclic aromatic hydrocarbons as probes of atmospheric photochemistry.
Crimmins, B1, Baker, J1, 1 Chesapeake Biological Laboratory, University of Maryland Center for Environmental Science, Solomons, Maryland, USA
ABSTRACT- Nitro-substituted polycyclic aromatic hydrocarbons (NPAHs) are mutagenic compounds observed in rural and urban environments. Unlike their parent unsubstituted polycyclic aromatic hydrocarbons (PAHs), NPAHs have primary and secondary sources to the ambient atmosphere. Specific NPAH isomers are formed during primary electrophilic nitration post combustion and secondary formation in the gas phase through direct or hydroxy radical initiated nitrate substitution. The NPAH contribution to particulate matter mutagenicity has been the major focus of current research. In addition to the health effects associated with NPAHs, the isomeric composition depends on the formation pathway. Therefore, NPAHs can be used to assess the importance of photochemistry on the composition of ambient particulate matter and are an alternative marker for the primary and secondary sources of ambient particulate matter. We have determined the diurnal concentrations and size distribution of PAHs and NPAHs in the Baltimore atmosphere using a hi-volume bulk sampler and a Berner low-pressure impactor, respectively. 1-nitropyrene, a proposed diesel marker, concentrations were elevated during the night (day and night, 15 ± 1 pg/m3 and 27 ± 6 pg/m3, respectively) and 2-nitrofluoranthene concentrations, the dominant secondary NPAH, were greater in the day (120 ± 20 pg/m3 and 200 ± 110 pg/m3 during the day and night, respectively). The ratio of these two isomers was used as an indicator of secondary formation on the various size cuts in successive day/night samples between April 15 − 18, 2002. Evidence of gas phase and particle phase formation of 2-nitrofluoranthene was found in the day and night, respectively. Ancillary parameters, such as, NO, O3, OC, EC, and particulate nitrate are employed as correlation parameters to elucidate the NPAH relationship to secondary organic aerosol products.
Key words: photochemistry, nitro-substituted polycyclic aromatic hydrocarbons, size-resolved, secondary organic aerosol