The contribution of the ozonolysis of terpenes to tropospheric OH concentrations

The recent finding that OH is formed as a direct product of the ozonolysis of terpenes is used to investigate the influence of this new OH source on t he tropospheric OH budget applying model calculations. The results show tha t the OH production following UV photolysis of ozone leads to the main comp etition for ozonolysis at daytime. OH may increase considerably in its conc entration as a result of the ozonolysis of terpenes at low photolysis frequ encies, however, at high photolysis frequencies and moderate NOx concentrat ions this effect is reversed due to the fast reaction of OH with terpenes. At night ozone competes with NO3 in its reactions with the terpenes. Integr ated over a full day of 24 h the terpene reactions lead to a source of OH i n the troposphere.