Emission ratios and photochemical production efficiencies of nitrogen oxides, ketones, and aldehydes in the Lower Fraser Valley during the Summer Pacific 1993 oxidant study

Observations made at a ground site east of Vancouver, Canada, were used in a principal component analysis (PCA) to derive (1) the emission ratios (ER) SO2, NOx HNO2, HNO3, ketones, and aldehydes relative to CO and (2) the photochemical production efficiencies (PPE) of 03, HNO2, HNO3, PAN, and several ketones and aldehydes relative to the formation of NO2. It is shown that derived ER(SO2) and ER(NOx) are consistent with the mobile emission sources in the Greater Vancouver Regional District (GVRD) emission inventory. Combining the ER data for other species with the GVRD CO emission inventory, the daily emission rates for these species have been estimated, indicating significant sources for these species. The derived PPE values for 03, HNO2, HNO3, PAN, the ketones, and the aldehydes are as follows: PPE(O3) is approximately 8–11 depending on the time of day; PPE(acetone) is between 1 and 2; PPE(MVK), PPE(MACR), and PPE(MEK) are approximately the same between 0.1 and 0.2; PPE(HCHO) is between 1 and 2, but PPE(propanal) and PPE(butanal) are lower than PPE(HCHO) by a factor of 2–10. It is shown that the daily photochemical production rates of 03 and the carbonyl species are approximately linear functions of the NOx daily emission rates. When the photochemical production rates are compared with counterpart daily emission rates, it is shown that for the organic compounds, the contributions from photochemistry were more important than daytime emissions; for HNO2, there is more emission contribution than photochemistry, opposite to the case for HNO3.