The Treasure Valley secondary aerosol study I: measurements and equilibrium modeling of inorganic secondary aerosols and precursors for southwestern Idaho

The SCAPE2 aerosol equilibrium model was applied to measured concentrations of PM2.5 aerosol and precursor gases. Ambient measurements in the Treasure Valley, Idaho were collected during stagnation episodes between December 1999 and March 2000 when conditions were favorable for the formation of secondary inorganic aerosol. SCAPE2 results agreed well with measurements for the episodes tested; Monte Carlo simulation using the uncertainties of the model input variables indicated that discrepancies between measured and modeled results were within the range of analytical precision. Air pollution control strategies were evaluated by perturbing the model input concentrations of total sulfate, nitrate, and ammonium. The largest reductions in secondary aerosol concentrations occurred when total nitrate was reduced, indicating that the formation of ammonium nitrate was limited by the availability of nitrate.