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SEMI-CONTINUOUS AEROSOL CARBON MEASUREMENTS: COMPARISON OF ATLANTA SUPERSITE MEASUREMENTS
Citation:
Lim, H. J., B. Turpin, E. Edgerton, S. Hering, G. Allen, H. Maring, AND P A. Solomon. SEMI-CONTINUOUS AEROSOL CARBON MEASUREMENTS: COMPARISON OF ATLANTA SUPERSITE MEASUREMENTS. JOURNAL OF GEOPHYSICAL RESEARCH: ATMOSPHERES 108(D7):SOS7-1 to SOS7-12, (2003).
Impact/Purpose:
The core aerosol research for FY01 includes evaluation of newly developed and developing methods for the chemical analysis and sampling of PM in ambient air, especially state-of-the-art continuous and non-invasive aerosol measurement methods, and the study of the aerosol sampling processes to better assess the true aerosol concentration and size distributions observed in the ambient environment. An additional emphasis is placed on integrated sampling for stable and semi-volatile organic aerosol species. This latter area addresses the state-of-the-art in this measurement area. This program supports Title I of the Clean Air Act in its mandate for performing research to support the NAAQS, GPRA goal 1.1.5, and ORD's main research objective on PM.
Much of this work directly supports OAQPS and may be applied within the Supersites Program managed jointly by OAQPS and ORD. This research also will support many of ORD's long-term research goals by providing more reliable information (decrease uncertainty) on ambient aerosols that can be utilized for characterizing risk.
Finally, an APM, has been established to develop measurement methods for causal factors, due in 2004. Currently, there are a number of causal factor hypotheses, but none have sufficient evidence to support developing one measurement/analytical method over another. The PM methods team will support and work with Joellen Lewtas on methods for the collection and analysis of semi-volatile and aerosol phase organic species to help address this APM. The PM methods team will continue to work within the Supersites program and with OAQPS and their new partners in ORIA to further evaluate continuous species specific methods and aerosol physical property measurement methods.
Description:
An intensive field campaign of the Atlanta Supersite Experiment was carried out at a ground-based measurement site on Jefferson Street in midtown Atlanta, GA, from 3 August to 1 September, 1999. This paper examines the semi-continuous particulate organic and elemental measurements that were made as a part of the experiment. Measurements were made using a Rutgers University/Oregon Graduate Institute in situ thermal-optical carbon analyzer, Rupprecht and Patashnick 5400 ambient carbon particulate monitor, Radiance Research particle soot absorption photometer, Aerosol Dynamics flash vaporization carbon analyzer, and Magee Scientific AE-16 aethalometer. The "intersampler precision" with which semi-continuous particulate TC, OC, and EC were measured is 7, 13 and 26%, expressed as pooled coefficients of variation of 2, 3, and 4 instruments, respectively. Correlations between pairs of OC measurements are moderate (R2 = 54-73%) and correlations between pairs of EC measurements are high (R2= 74-97%). Differences in reported OC concentrations are small compared to differences in EC concentrations; intersampler EC concentration differences result from differences 1) in the operational definitions of OC and EC, 2) in the calibration of optical instruments, and 3) because EC values are closer to limits of detection. This agreement between semi-continuous samplers is quite good, especially in light of previous particulate carbon comparisons. Reasons for measurement differences and benefits of automated, time-resolved measurements are discussed.
This publication was funded in part by the Electric Power Research Institute. The United States Environmental Protection Agency through its Office of Research and Development partially funded and collaborated in the research described here under assistance agreement number CR824849 to Georgia Institute of Technology. It has been subject to Agency review and approved for publication.