In September 1994 the chemical and physical properties of aerosol particles over southern California were characterized. Concentrations of particle chemical species were higher near the surface than at higher altitudes. In these particles, measured organic and inorganic water soluble masses were 7 +/- 1% and 75 +/- 12%, respectively, of the dried total particle mass (TPM). Non-sea-salt (nss) SO4=, NO3-, NH4+, and H+ were the major contributors to the mass and ionic equivalence of the particles, The ratio of the soluble organics (SumOrg) to nss SO4= was found to be a function of the TPM, which was similar to the simple relationship found over the northwestern Atlantic Ocean for altitudes <3 km. When the H+ ion was included, there was a good ionic balance between the cations and anions in the particles, The pH of the particles ranged from -2.4 to 0.20 (averaging -0.85). The particle volume size distribution dV/d log D shows distinct features according to the altitude and location of sample collection, In urban plumes, dV/d log D was significantly higher than at high altitudes and had a consistent accumulation mode peaking at 0.24 mu m. For all samples, nss SO4= and NH4+ comprised 59% of the accumulation mode particle mass on average. Samples showed two groups with high and low NH4+/nss SO4= ratios of 0.85 and 0.01, respectively. For the first group the low ambient relative humidities indicate that NH4+ and nss SO4= were in crystallized ammonium sulfate and letovicite in equilibrium with solution, while the second group was probably close to H2SO4 droplets. On the basis of these compositions the refractive index eta was found to be about 1.5 for the first group and <1.4 for the second group. The water contents of the NH4+ - nss SO4= particles were estimated to be 35 +/- 24%, leading to an average ratio of H2O/nss SO4= = 0.9 +/- 1.2.
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 O-3, HNO2, HNO3, PAN, and several ketones and aldehydes relative to the formation of NOz. 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 O-3, HNO2, HNO3, PAN, the ketones, and the aldehydes are as follows: PPE(O-3) 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 O-3 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. (C) 1997 Elsevier Science Ltd.