AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
Coarse Particles in the Desert Southwest: Final Results and Policy Insights
ANDREA CLEMENTS, Matthew Fraser, Pierre Herckes, Kale Walch, Paul A. Solomon, Arizona state University
Abstract Number: 465 Working Group: Source Apportionment
Abstract Many arid regions of the desert Southwest have been designated non-attainment of the National Ambient Air Quality Standard (NAAQS) for PM10. Within this size range, coarse particle (PMc, particles with an aerodynamic diameter [AD] between 2.5 and 10microns) concentrations often exceed that of fine particles (PMf, particles with AD less than or equal to a nominal 2.5microns) and primarily drive exceedences. However, PMc has not been widely studied separately from the PMf fraction of PM10 and improved information about the spatial and temporal particle composition, source categories, and relative source strength can aide in improved PM10 control measures.
Pinal County, Arizona was chosen as an ideal study location to further our understanding of particle sources impacting arid environments. With population growth as a result of urban sprawl into the traditionally rural region, attainment of the PM10 standard is a pressing concern in Pinal County. A year-long characterization study was conducted at three different locations on a 1-in-6 day schedule yielding a rich dataset characterizing both fine and coarse particles in terms of mass, ions, elements, bulk elemental and organic carbon, and some organic species concentrations. These data were used for source appointment modeling of the aerosol.
Several metrics confirmed the dominance of crustal sources. Spatial analysis, temporal variation, and modeling results suggest variable influences from agricultural sources, road dust, and the cattle feedlots with more minor contributions from secondary aerosol formation and regionally-transported particles. Results indicate control of crustal sources may affect the greatest change in overall mass concentrations and that the close proximity of the cattle feeding operations greatly influences the mass measurements at one of the regional compliance monitors. Future policy implications insights are being discussed with the Pinal County Air Quality District and some proposals may be applicable to other counties within the desert Southwest currently in non-attainment of the federal NAAQS.