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Evaluation and Comparison of Methods for Measuring Ozone and NO2 Concentrations in Ambient Air during DISCOVER-AQ
Citation:
Long, R., M. Beaver, R. Duvall, Jim Szykman, S. Kaushik, K. Kronmiller, M. Wheeler, S. Garvey, AND J. Crawford. Evaluation and Comparison of Methods for Measuring Ozone and NO2 Concentrations in Ambient Air during DISCOVER-AQ. EM Magazine. Air and Waste Management Association, Pittsburgh, PA, , 1-11, (2016).
Impact/Purpose:
Under the Clean Air Act, the U.S. EPA has established National Ambient Air Quality Standards (NAAQS) for six “criteria” pollutants (carbon monoxide, nitrogen dioxide, ozone, sulfur dioxide, lead and particulate matter) that are set forth in Title 40, Part 50 of the Code of Federal Regulations (40 CFR Part 50). The EPA and the States are jointly responsible for monitoring the ambient air for these pollutants. This monitoring is carried out as part of a national network of monitoring sites, called the State and Local Air Monitoring Stations (SLAMS). The air quality data obtained from these sites are reported to EPA’s Air Quality System (AQS) database, along with other information, and are used for 1) determining compliance with the NAAQS, 2) assessing effectiveness of State Implementation Plans (SIPs) in addressing NAAQS nonattainment areas, 3) characterizing local, state, and national air quality status and trends, 4) and associating health and environmental damage with air quality levels/concentrations.
Description:
Ambient evaluations of the various ozone and NO2 methods were conducted during field intensive studies as part of the NASA DISCOVER-AQ project conducted during July 2011 near Baltimore, MD; January – February 2013 in the San Juaquin valley, CA; September 2013 in Houston, TX; and July – August 2014 near Denver, CO. During field intensive studies, instruments were calibrated according to manufacturers’ operation manuals and in accordance with FRM requirements listed in 40 CFR 50. During the ambient evaluation campaigns, nightly automated zero and span checks were performed to monitor the validity of the calibration and control for drifts or variations in the span and/or zero response. Both the calibration gas concentrations and the nightly zero and span gas concentrations were delivered using a dynamic dilution calibration system (T700U/T701H, Teledyne API). The analyzers were housed within a temperature-controlled shelter during the sampling campaigns. A glass inlet with sampling height located approximately 5 m above ground level and a subsequent sampling manifold were shared by all instruments. Data generated by all analyzers were collected and logged using a field deployable data acquisition system (Envidas Ultimate). A summary of instruments used during DISCOVER-AQ deployment are listed in Table 1. Figure 1 shows a typical DISCOVER-AQ site (Houston 2013) where EPA (and others) instrumentation was deployed.
