We summarize the results from the various measurements and the inter-sampler comparisons from Southeastern Aerosol and Visibility Study (SEAVS), a study with one of its objectives to test for closure among chemical, gravimetric and optical measurements of atmospheric aerosol particles. Sulfate and organics are the dominant components of the SEAVS fine particles (nominally, particles with aerodynamic diameter ≤2.5 μm) but between 28 and 42% (range over various samplers) of the gravimetrically measured total fine particle concentration is unidentified by the chemical measurements. Estimates of water associated with inorganic components and measurement imprecision do not totally explain the observed difference between gravimetric and chemical measurements. We examine the theoretical and empirical basis for assumptions commonly made in the published literature to extrapolate total fine particle concentration on the basis of chemical measurements of ions, carbon and elements. We then explore the more general question of closure using the SEAVS data as well as data from other, similar studies reported in the literature. In so combining the SEAVS measurements with other similar studies, we find a strong association between organic carbon and the unidentified component, that is, the fraction of the total fine particle concentration not identified by chemical measurements. We offer several tenable hypotheses for the relationship between the organic and unidentified components that deserve to be tested in future work. Specifically, we hypothesize that (1) errors in the sampling and analysis of organic carbon; (2) estimates of organic mass from measurements of organic carbon; and/or (3) water absorption by organics may all contribute to the observed relationship.
|Original language||English (US)|
|Number of pages||17|
|Journal||Journal of the Air and Waste Management Association|
|State||Published - May 2000|
Bibliographical noteFunding Information:
We thank Thomas Cahill (UC Davis), Derek Day (NPS), and William C. Malm (NPS), for providing us the IMPROVE measurements discussed in this paper and for their comments as the paper evolved; Mary Ann Allan, EPRI Project Manager for reviewing the manuscript and coordinating SEAVS measurements and data analysis. This work was supported by EPRI, American Electric Power, Duke Power, Oglethorpe Power, South Carolina Electric and Gas, Southern Company and Tennessee Valley Authority. In addition to these organizations, the National Park Service and U.S. Department of Energy supported SEAVS. Readers can contact Ms. Mary Ann Allan for other SEAVS reports and papers.