Impact/Purpose:

The main objective of this task is to provide the Agency with instrumentation to support its monitoring activities with respect to establishing the ambient air concentrations of ozone and ozone precursors such as nitrogen oxides and volatile organic compounds.

Description:

This task involves the development and testing of methods for monitoring ozone and compounds associated with the atmospheric chemistry of ozone production both as precursors and reaction products. Although atmospheric gases are the primary interest, separation of gas and particle phases followed by their speciation, e.g. as HNO3, HNO2, and particle nitrate, is also of interest under the revised mandate of NARSTO. This task supports the diagnostic testing of air quality simulation (AQS) models by providing instruments with sufficient time resolution (<1 hr) and sensitivity and range (typically 1 ppbv with 20% precision up to double or triple digit ppbv depending on the compound). An additional benefit of this task is that new methods can be used by other programs such as the PAMS program and the Air Toxics Program.

Ozone is a secondary pollutant that is produced in the ambient air through atmospheric photochemistry. In any given region, current air quality simulation models predict that the limitation on ozone production can be the concentration of either nitrogen oxides or volatile organic hydrocarbons. These in turn depend on the emission sources, the nature of long range transport in the region and the weather conditions. Characterization of the ambient concentrations of ozone and its precursors is essential to determine the accuracy of model predictions and ultimately to select the most effective control strategy for ozone precursors. Successful demonstrations of new instrumentation for monitoring ambient NO2, HCHO, HNO3 and HNO2 have been made while development plans for real-time monitoring instrumentation for nitrate and H2O2 are in progress. Instrument development initiatives for establishing vertical profiles of ozone concentrations, for measuring peroxy radical concentrations, and for measuring a broad range of individual species of nitrogen oxides and of volatile organic compounds are currently in place.

Record Details:

Record Type:PROJECT

Start Date:09/01/1998

Completion Date:09/01/2001

Record ID: 56145

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Project Information:

Progress :HCHO, H2O2, and Total Peroxides: The initial development and testing of a prototype real-time formaldehyde monitor was completed during FY-98 and has continued to the present. An initial report on an evaluation of the HCHO monitor is available as EPA Report EPA/600/R-98/139 or through NTIS (NTIS Accession No. PB99-118291). The prototype was redesigned based on the conclusions of this report and the redesigned instrument was tested as part of the 1999 summer field studies in Nashville (15 June - 15 July 1999) and in Atlanta (August 1999). Databases were constructed from the summer's data and included in the overall field study database. In July 2000, a further revision of the system was deployed in the Texas 2000 Field Study. In the current revision, the instrument needs no compressed zero air to operate and can be left to operate unattended for up to one week. A commercial version of the instrument is now available for HCHO. Hydrogen peroxide is being monitored with the same type of instrument in the Texas 2000 field study, and a monitor for total peroxides is in prospect.
NO, NO2, NOx, NOy, and Speciated NOz Compounds - A GPRA report (APM 442) entitled, "Recommended Methods for Ambient Air Monitoring of NO, NO2, NOy, and Individual NOz Species", has been prepared and was submitted as of September 2000. This report provides a survey of monitoring methods for reactive nitrogen oxides and identifies the methods that meet the criteria for diagnostic testing of air quality simulation models. Of particular interest are the methods for monitoring NO2 that improve on the chemiluminescence technique that is widely used for NAAQS monitoring but which is non-specific for NO2. Scientists from NOAA and the University of California contributed to the report and helped to formulate recommendations for program planning. One activity in preparation for writing the report was to operate different NO2 monitors as part of the 1999 Southern Oxidants Study held in Nashville, TN. These monitors included: (1) a chemiluminescence-based monitor with a thermal converter; (2) a chemiluminescence-based monitor with a photolytic converter; (3) a luminol-based monitor with chemical converter; and (4) an open path UV absorbance system. Monitoring results are included in the GPRA report.

Speciated VOCs - The Nashville study also provided an opportunity to operate EPA's autoGC system in the field to test for VOCs and to study the effect of ozone on the integrity of adsorbed VOCs during sample preconcentration prior to GC/MS analysis. In related laboratory studies sample integrity was observed to be compromised for certain types of compounds (aldehydes and alcohols) during sample preconcentration although no effect was observed for other compounds. Preparations for comparison of VOC monitoring techniques under different sample conditions are in place for a more thorough investigation beginning September 2000. This study includes the use of ozone scrubbers to eliminate the reaction of ozone with adsorbed organic compounds during sample preconcentration. Research planning on the use of two dimensional chromatography for better compound separation and identification has been initiated.


ABSTRACT/ORAL

Date Cleared - Citation

07-MAR-00 - Oliver, K.D., Jacumin, Jr., H.H., Kronmiller, K.G., Daughtrey, Jr., E.H., and McClenny, W.A. Preliminary results of VOC analyses by auto-GC/MS at Cornelia Fort Airpark June 15-July 15, 1999. Abstract presented at: SOS Data Analysis Workshop 2000, RTP, NC, March 6-10, 2000.

07-SEP-00 - Oliver, K.D., Jacumin, Jr., H.H., Daughtrey, Jr., E.H., and McClenny, W.A. Sample integrity of volatile organic compounds collected and stored on multiadsorbent tubes and analyzed using an auto GC-MS system. Abstract presented at: International Symposium on Measurement of Toxic and Related Air Pollutants, Research Triangle Park, NC, September 12-14, 2000.

07-MAR-00 - Kronmiller

Relevance : Research products being developed under this task include the GPRA report mentioned above which recommends monitoring methods to be used in evaluating the results of the NOx SIP Call of 1998 and the proposition that NOx emissions control can control ozone concentrations. If the modeling effort on which the SIP Call is based correctly accounts for the effect of reduction of NOx emissions on downwind O3 concentrations, then a cause and effect relationship will be demonstrated and the cost of emission control technology can be justified. This has major implications of Agency credibility.

The development of monitoring instruments for individual ozone precursors is also important to verify model predictions and to refine model mechanisms both in controlled experiments in smog chambers as well as in real world situations. In particular, the real time monitoring of compounds such as NO2, NOx, NOy, HCHO, H2O2, HNO3, HNO2 and speciated VOCs is being used for diagnostic testing of models, i.e. in comparing real world and simulated results. Another important aspect of NERL's support to modeling is the measurement of gas and particle concentrations in the vertical dimension; this activity is being sponsored through the U.S. Navy at the Penn State University.

Clients :Robin Dennis - NERL; David Mobley - OAQPS; Rich Sheffe - OAQPS; Deborah Luecken - NERL

Project IDs:

ID Code :3917

Project type :OMIS