First Name | Robert |
---|---|
Last Name | Harley |
Email Address | harley@ce.berkeley.edu |
Affiliation | UC Berkeley |
Subject | NO2 measurement methods |
Comment | The staff report discusses the accuracy and precision of chemiluminescent methods for measuring NO2. Accurate measurement methods for NO2 are available (Ryerson et al., 2000, JGR, vol 105, pp. 26447-26461; Thornton et al., 2000, Analytical Chemistry, vol 72, pp. 528-539), but these are methods are not routinely used in ambient air monitoring networks. I recommend inclusion of these newer measurement methods in Chapter 3 of the technical support document. It is known (e.g., Winer et al., 1974, ES&T, vol 8, pp. 1118-1121) that chemiluminescent analyzers respond not only to NO2 but also to other nitrogen-containing air pollutants including peroxyacyl nitrates. This could be a significant source of positive bias in ambient NO2 measurements. PANs are one example, but are not the only class of pollutants for which interferences with the NO2 measurement may occur. Nitrous and nitric acids may also get reported as NO2, assuming they are not lost in air sampler inlet lines. This could be important in comparing clinical studies where the exposure is presumably to pure & well-characterized levels of NO2, and the real atmosphere where exposures include not only NO2 but also other pollutants that may have different types and/or severity of health effects. In summary, I disagree with the characterization of routine NO2 measurements as being accurate, in the sense of being free of significant interferences. This issue may be deserving of further consideration. |
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Date and Time Comment Was Submitted | 2007-02-19 15:16:47 |
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