Primary and secondary contributions to ambient PM in the midwestern United States.
Ambient PM2.5 samples were collected in five midwestern United States cities throughout 2004: East St. Louis, Illinois; Detroit Michigan; Cincinnati, Ohio; Bondville, Illinois; and Northbrook, Illinois. Monthly composites were analyzed using chemical derivatization coupled with GC-MS analysis to estimate the contributions of several sources to the total ambient organic carbon. A chemical mass balance (CMB) approach was used to estimate contributions from several primary sources. An additional, organic tracer-based technique was employed to estimate secondary contributions, including secondary organic carbon derived from isoprene, alpha-pinene, beta-caryophyllene, and toluene. The sum of these contributions was compared with the total organic carbon measured at each sampling site, and reasonable carbon mass balances were observed for four of the five sites. In Bondville, Northbrook, Cincinnati, and Detroit a strong correlation was observed between the sum of the estimated primary and secondary contributions and the measured organic carbon (R2 = 0.73). The estimated secondary organic carbon concentrations were observed to vary considerably with season, with the strongest contributions coming from isoprene and alpha-pinene during the summer. While further research is required, there is some evidence that the contribution estimates for alpha-pinene, beta-caryophyllene, and toluene SOC may to some degree represent the contributions from the broader classes of monoterpenes, sesquiterpenes, and aromatics.
National Exposure Research Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711, USA. lewandowski.michael@epa.gov
Michael
M
Lewandowski
Mohammed
M
Jaoui
John H
JH
Offenberg
Tadeusz E
TE
Kleindienst
Edward O
EO
Edney
Rebecca J
RJ
Sheesley
James J
JJ
Schauer
D000393:Air Pollutants / Q000032:analysis*; D000397:Air Pollution; D002244:Carbon / Q000032:analysis / Q000737:chemistry; D004784:Environmental Monitoring / Q000379:methods; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods; D015146:Midwestern United States; D015233:Models, Statistical; D008962:Models, Theoretical; D009930:Organic Chemicals / Q000032:analysis; D010316:Particle Size; D052638:Particulate Matter / Q000032:analysis*; D012621:Seasons; D013997:Time Factors
D000393:Air Pollutants; D009930:Organic Chemicals; D052638:Particulate Matter; D002244:Carbon