Advances in Earth Science
• Articles •
Lin Yunping, Zhao Chunsheng
Lin Yunping, Zhao Chunsheng. The Oxidation in the Troposphere: A Review[J]. Advances in Earth Science, 2009, 24(5): 488-496.
The tropospheric oxidation is an important indicator of the cleansing capacity of the atmosphere. Most trace gases emitted into the atmosphere are removed by oxidizing chemical reactions involving ozone and the hydroxyl free radical. The research history of tropospheric OH including the fundamental reactions, measurement techniques and the long-term trend is reviewed in this paper. Due to the increased emissions of CO, NOx(=NO+NO2) and hydrocarbons by human activities, global mean OH concentrations have decreased since pre-industrial times, and the future trend of tropospheric OH still depends on the emissions of CO, NOx(=NO+NO2) and hydrocarbons. Using a 3-D global chemistry and transport model (MOZART), the distributions and trend of tropospheric OH over China and its neighborhood are studied. The results show that, consistent with variations in sunlight and water vapor, the concentrations of tropospheric OH over China increase gradually from winter to summer. In addition, by reason of the various emissions strength of OH precursors or sinks, such as ozone, CO and NOx, the highest concentrations of OH in July arise in North China and Pearl River Delta, while the lowest concentrations occur in those plateau areas in West China. Analysis of the impacts of various emissions of air pollutants on tropospheric OH in East China reveals a significant increase of tropospheric OH as a result of the pronounced increase of NOx emissions in China. Looking to the future, there is urgent need for more observations of tropospheric OH to improve and ultimately validate models and further understand the oxidation processes in our atmosphere.