Temperature dependence of the uptake coefficients of nitric acid, hydrochloric acid and nitrogen oxide (N2O5) by water droplets

Abstract

The uptake of HNO3, HCl, and N2O5 by aq. surface was measured as a function of temp. over the range from 268 to 294 K. The exptl. method employs a monodisperse train of droplets of 200-.mu.m diam. in a low-pressure flow reactor. The value of the uptake coeff. increases with decreasing temp. for each of these species. The similarity in the abs. values of .gamma. at all temps. for HNO3, HCl, and H2O2 (previously reported) suggests that the uptake coeff. is a measure of the rate of phys. solvation and is therefore identified as the mass accommodation coeff. Under tropospheric cloud conditions these large values of .gamma. indicate that gas-liq. mass-transfer rates will be limited by gas diffusion rather than mass accommodation. Therefore, the tropospheric cloud chem. of these species will be detd. by their soly. and aq.-phase reactivity.