| Popis: |
The dark decay of nitrous acid gas (HONO), added to filtered outside air in a glass/pyrex smog chamber, was studied. For the concentrations used in the study, in the range of 1–10 ppmv, a decay with a half-life value of hours was found. Since the decay rate increased with HONG concentration and was quite reproducible, it was analyzed as a second-order reaction and a rate constant of (1.5 ± 0.3) 10 −19 cm 3 molec −1 s −1 was obtained. This is very similar to a value obtained in a previous study in a chamber with similar wall material. High concentrations of copper oxide aerosols and NaCl droplets did not measurably accelerate the decay. There was some removal of HONO by reaction with NaCl, as evidenced by the formation of aerosol-nitrate, but the contribution of this process to the total loss of HONO was negligible. Whereas initially only a limited amount of NO was formed as a result of the decay of HONO, the subsequent loss of HONG was via decomposition into NO and NO 2 (and H 2 O). The final concentrations of the gases were in accordance with the equilibrium values calculated with the equilibrium constant from an earlier study. The decay was also studied at relative humidities approaching saturation. It was found that the decay varied from experiment to experiment but that it was on average a factor of ten faster than at the standard relative humidity of 80%. The acceleration is ascribed to catalysis of the decay adsorbed water at the walls of the chamber. |
Full Text from ScienceDirect