Reaction of N2O5 on tropospheric aerosols: Impact on the global distributions of NO x , O3, and OH

TLDR: In this paper, a three-dimensional global model of the troposphere is used to show that the heterogeneous reactions of NO 3 and N205 on aerosol particles have a substantial influence on the concentrations of NOx; 03, and OH.

Abstract: Using a three-dimensional global model of the troposphere, we show that the heterogeneous reactions of NO 3 and N205 on aerosol particles have a substantial influence on the concentrations of NOx; 03, and OH. Due to these reactions, the modeled yearly average global NOx burden decreases by 50% (80% in winter and 20% in summer). The heterogeneous removal of NOx in the northern hemisphere (NH) is dominated by reactions on aerosols; in the tropics and southern hemisphere (SH), with substantial smaller aerosol concentrations, liquid water clouds can provide an additional sink for N205 and NO 3. During spring in the NH subtropics and at mid-latitudes, O3-concentrations are lowered by 25%. In winter and spring in the subtropics of the NH calculated OH concentrations decreased by up to 30%. Global tropospheric average 03 and OH burden (the latter weighted with the amount of methane reacting with OH) can drop by about 9% each. By including reactions on aerosols, we are better able to simulate observed nitrate wet deposition patterns in North America and Europe. 03 concentrations in springtime smog situations are shown to be affected by heterogeneous reactions, indicating the great importance of chemical interactions resulting from NOx and SO2 emissions. However, a preliminary analysis shows that under present conditions a change in aerosol concentrations due to limited SO2 emission control strategies (e.g., reductions by a factor of 2 in industrial areas) will have only a relatively minor influence on 03 concentrations. Much larger reductions in SO2 emissions may cause larger increases in surface 03 concentrations, up to a maximum of 15%, if they are not accompanied by a reductio!a in NOx or hydrocarbon emission.