The Plume Volume Molar Ratio Method for Determining NO2/NOx Ratios in Modeling-Part I: Methodology.

During New Source Review modeling of proposed major sources of oxides of nitrogen (NOx), maximum impacts are often predicted to occur very close to the source. At the same time, current modeling guidance recommends techniques that may be overly conservative in estimating the fraction of nitrogen dioxide (NO2) in these plumes. A new technique called the Plume Volume Molar Ratio Method (PVMRM) is being proposed that simulates both chemistry and dispersion to better estimate the fraction of NO2. This paper documents the methodology behind the technique. A follow-up pa-per1 will evaluate its performance against a number of databases. This method is designed to realistically predict NO2 fraction at close-in receptors yet still provide conservative estimates so that the air quality standards can be protected.