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Indicies to Evaluate Air Quality Impacts on Vegetation
The scientific information underpinning the National Ambient Air Quality Standards is reviewed and updated every five years. This responsibility is led by The Environmental Protection Agency and involves scientists selected from federal, state, and private sectors. A State of the Science Criteria Document report is prepared that serves as the scientific basis for any proposed changes in the National Ambient Air Quality Standards. Robert Musselman and William Massman, RMRS, were invited to co-author with Allen Lefohn "Ozone exposure plant response relationships", Section 9.6 of Volume I; and "Effects-based air quality exposure indices", Section AX9.4 of Volume III of the Criteria Document chapters on "Environmental Effects of Ozone and Other Photochemical Oxidants". Availability of the report was published in the Federal Register on February 28, 2006 and is available online as "Air Quality Criteria for Ozone and Related Photochemical Oxidants (Final)",
U.S. Environmental Protection Agency, http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=149923. The Criteria Document details the latest state-of-the-art of scientific knowledge on ozone effects on vegetation, and has been extensively peer reviewed. The document is required by law of EPA to provide a sound scientific basis for establishing the National Ambient Air Quality Standard for ozone and any changes to this standard.
The synthesis of the literature on exposure and flux-based indicies was also published by Musselman and others as a critical review in a scientific journal. The authors concluded that the current concentration-based ozone standards do not adequately protect vegetation. Newer flux-based ozone metrics that include information on stomatal uptake of ozone into plant tissue have been proposed for use in air quality standards. The Musselman and others review concluded that if these flux-based ozone metrics do not include ozone detoxification, they will overestimate vegetation effects. They concluded that exposure-based ozone metrics that preferentially weight the higher concentrations and are cumulative over the growing season are currently the best alterative to the concentration-based metrics. The authors also recommended that ozone uptake at night should be included in the ozone metric used for an air quality standard.
Citation
Musselman, R.C.; Lefhon, A.S.; Massman, W.J.; Heath, R.L. 2006. A critical review and analysis of the use of exposure- and flux-based indices for predicting vegetation effects. Atmospheric Environment 40: 1869-1888.
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