中文摘要：

对流层大气氧化性是对流层大气自我清洁能力的一个重要指标，对流层中大多数痕量气体都是通过氧化过程清除的。回顾近半个世纪以来对流层大气氧化性的研究历史，对流层大气氧化性的研究无论是从测量技术还是模式研究方面都已取得了一定的进展。工业革命以来，由于人类活动的影响，CO、NOx和碳氢化合物等大气污染物排放增多，使得全球对流层大气OH浓度呈下降趋势，未来对流层大气氧化性的变化很大程度上也取决于这些气体的排放情况。利用全球三维大气化学传输模式MOZART研究中国地区对流层大气OH自由基的分布和变化趋势表明，与全球OH自由基变化趋势不同，近10年来中国东部地区OH自由基浓度趋于增加。未来对流层大气氧化性研究的关键问题仍是OH自由基测量技术的提高问题，OH自由基观测结果是完善对流层光化学机制和改进大气化学模式的先决条件。

英文摘要：

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 hy- drocarbons. 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 Noah 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.