High atmospheric NO(x) levels and multiple photochemical steady states

The rate of removal of atmospheric NO(x) compounds at different NO(x) levels is estimated using a one-dimensional photochemical model. NO(x) removal by wet deposition, surface deposition, and thermochemical processes is examined. NO(x) removal rates at different surface NO mixing ratios are calculated and the data are analyzed. It is revealed that at low NO(x) levels NO(x) is photochemically converted to HNO3 by either wet or dry deposition; however, at high NO(x) levels formation of HNO3 is inhibited due to the disappearance of tropospheric ozone and OH, and the NO(x) is removed by rainout of N2O4 and N2O5, surface deposition of NO and NO2, and direct dissolution of NO and NO2 in rainwater. The effects of NO(x) mixing ratios greater than 10 to the -7th on the ozone and climate are investigated.