Laboratory studies of sources of HONO in polluted urban atmospheres

Laboratory studies reported here and in previous work show that the reactio n of NO(g) with surface adsorbed HNO3 may be a significant source of HONO i n polluted urban atmospheres. If these laboratory studies can be extrapolat ed to ambient conditions, this heterogeneous reaction may generate HONO to about the same extent as the hydrolysis of NO2 on surfaces, which is greate r than the heterogeneous reaction of NO, NO2 and water. It may also be invo lved in generating HONO In snowpacks, and important in reconciling the disc repancy between measured and modeled HNO3/NOx ratios in the troposphere.