Total OH reactivity measurements aboard the Zeppelin NT during the PEGASOS campaign 2012: Contributions of substance classes to the total OH reactivity

The hydroxyl (OH) radical is the main oxidant of atmospheric traces gases. The quantification of its sources and sinks is necessary to fully comprehend the OH concentration. Due to difficulties quantifying all the individual compounds contributing to the OH loss, the direct quantification of the OH loss termed as the total OH reactivity is a crucial approach to establish the budget of OH. Especially in forested areas, where OH reactivity is dominated by highly reactive organic compounds, the directly measured total OH reactivity could not be explained by individual trace gas measurements in recent field campaigns. This difference is termed ‘missing reactivity’.