ESTIMATION OF THE RATE-CONSTANT FOR THE REACTION OF ACID SULFATE AEROSOL WITH NH3 GAS FROM ATMOSPHERIC MEASUREMENTS

Horizontal gradients in atmospheric aerosol strong acidity have been interpreted in terms of the rate of neutralisation of aerosol H+ by gaseous ammonia. The results indicate a pseudo-first-order rate constant for this reaction within the range 4 x 10(-6) s-1 to 4.1 x 10(-4) s-1 consistent with model results and experimental data derived by other methods. The rate constant is reduced as the aerosol becomes less acidic, which is reflected in a positive correlation between rate constant and aerosol H+/NH4+ ratio.