The concentration and composition of PM_(2.5) from May to September of 2000 and monthly trends in ambient fine-particulate material concentrations from october 1999 through December 2000 at the National Energy Tehcnology laboratory's airmonitoring site in pittsburgh are reported.Twenty four-hour integrated samples were collected using the Particle Concentrator-Brigham Young University Organic Sampling System(PC-B(OSS),a multichannel integrated diffusion denuder sampler designed for routine determination of the chemicla composition of ambient particulate matter.The fine-particulate pollutants determined were sulfate estimated as ammonium sulfate,nonvolatile organic material,semivolatile organic material lost from particles during sampling,elemental carbon,nitrate estimated as ammmonium nitrate,including ammonium nitrate lost from particles durign sampling adn elemental content determined by PIXE(for a limited number of samples).Episodes with elevated sulfate and organic material (both semivolatile and nonvolatile)concentratiosn were seen throughout this period.For the purpose of this discussion,an episode was defined as all times when 3h average TEOM monitor PM_(2.5) concentratios exceeded 30 mug/m~3.The use of estimated back-trajectories indicated that during the periods for which these elevated concentratiosn were observed,pollutants were transported predominantly from the Southwest from the Ohio River Valley to the samplign site.for days when fine particulate episodes occurred,back-trajectory computations were derived fro time intervals for which PM_(2.5) TEOM concentrations exceeded 30 mug/m~3.However,for nonepisode days,back trajectories were computed over a 24h period.Average PC-BOSS-constructed PM_(2.5) concentration(including semivolatile components lost from particles during samplign)for the period from October 1999 through December 2000 was 19 mug/m~3,excluding crustal material concentraiton.
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