Submitted on August 12, 2008
Accepted on May 21, 2009

Amplified Trace Gas Removal in the Troposphere

¹ Forschungszentrum Jülich, Institut ICG-2: Troposphäre, 52425 Jülich, Germany.
² Forschungszentrum Jülich, Institut ICG-2: Troposphäre, 52425 Jülich, Germany.; College of Environmental Sciences and Engineering, Peking University, Beijing 100871, China.
³ Research Center for Environmental Changes (RCEC), Academic Sinica, Taipei, China.
⁴ Forschungszentrum Jülich, Institut ICG-2: Troposphäre, 52425 Jülich, Germany.; Present address: Earth System Research Laboratory (ESRL), NOAA, Boulder, CO, USA, and Cooperative Institute for Research in the Environmental Sciences (CIRES), University of Colorado, Boulder, CO, USA.
⁵ Faculty of Science, Ibaraki University, Ibaraki 310-8512, Japan.
⁶ Research Center for Advanced Science and Technology, University of Tokyo, Tokyo 153-8904, Japan.
⁷ Forschungszentrum Jülich, Institut ICG-2: Troposphäre, 52425 Jülich, Germany.; School of Environmental Science and Technology, Shanghai Jiaotong University, Shanghai 200240, China.
⁸ College of Environmental Sciences and Engineering, Peking University, Beijing 100871, China.

^* To whom correspondence should be addressed.
Franz Rohrer , E-mail: f.rohrer{at}fz-juelich.de
Yuanhang Zhang , E-mail: yhzhang{at}pku.edu.cn

The degradation of trace gases and pollutants in the troposphere is dominated by their reaction with hydroxyl radicals, OH. The importance of OH rests on its high reactivity, its ubiquitous photochemical production in the sunlit atmosphere, and, most importantly, on its regeneration in the oxidation chain of the trace gases. In the current understanding, the recycling of OH proceeds through HO₂ reacting with NO, thereby forming ozone. A recent field campaign in the Pearl River Delta, China, quantified the OH-, HO₂-concentrations, and turnover rates by direct measurements. We report concentrations of OH being 3 to 5 times greater than expected and propose the existence of a pathway for regeneration of OH independent of NO, which amplifies the degradation of pollutants without producing ozone.