Comparison of measured wintertime CO/NOX and VOC/CO ratios to emission inventories in Boise, Idaho

We report analysis of measurements made during the Treasure Valley PM2.5 Study for a 2 month period from December 1, 2008 to January 31, 2009. Treasure Valley is a rapidly growing area of Idaho comprising several towns and cities including Boise. In wintertime frequent stagnation events associated with temperature inversions cause poor air quality. Measurement of NO, NO2, NOy, CO and volatile organic compounds were made in addition to a suite of aerosol measurements. VOC measurements were made with a proton transfer reaction mass spectrometer (PTR-MS). Ratios of CO/NOx and VOC/CO were examined for comparison with the emissions inventory used in this area to better understand the role of roadway emissions as sources of CO, NOx, and VOCs, including the air toxics benzene, formaldehyde, and acetaldehyde. Mixing ratios of these species displayed lognormal distributions as did the ratios. The CO/NOx ratio was found to 6.5 ± 7% and the benzene / CO ratio 0.001 ± 7.5%. Comparison of the data to model output and emission inventories used by the regional AIRPACT-3 chemical forecast model will be presented.