EXPERIMENTAL-DETERMINATION OF HONO MASS ACCOMMODATION COEFFICIENTS USING 2 DIFFERENT TECHNIQUES

The mass accommodation coefficient alpha(HONO) of gaseous nitrous acid on water surfaces has been determined in a cooperation between the Universities of Strasbourg and Bonn. The droplet train technique (Strasbourg) yielded 0.04 < alpha(HONO) < 0.09 for an estimated surface temperature of 245 K, while the liquid jet technique (Bonn) yielded 0.03 < alpha(HONO) < 0. 15 for a surface temperature of 297 K. The uncertainty ranges allow for experimental scatter and estimated uncertainties in diffusion coefficients. The same HONO source and analytical equipment were used for both experiments, which were run in parallel. The results indicate that the exchange rate of HONO between atmospheric water droplets and interstitial air is not inhibited by interfacial resistance.