大气中过氧化氢的生成、污染特征及其影响因素

过氧化氢(H₂O₂)是自由基的源和汇,是对流层大气中重要的氧化剂. 采用文献研究法对1990年以来H₂O₂的文献进行搜集整理,对其生成途径、污染特征及其影响因素进行了研究. 结果表明:H₂O₂在大气、云水和颗粒物中均有存在,大气中的H₂O₂主要通过O₃和甲醛光解、VOC同OH·/O₃等反应生成. 大气中φ(H₂O₂)一般在nd～8×10-9内波动,晴天φ(H₂O₂)呈早晚低、午后高的日变化特征；φ(H₂O₂)随φ(O₃)、太阳辐射和气温的增加而升高,随φ(NO_x)、φ(VOCs)和相对湿度的升高而降低；H₂O₂氧化SO₂为SO₄2-是液相化学中最重要的反应,可以导致酸沉降以及二次气溶胶浓度的升高. 在气相光化学反应中,H₂O₂/HNO₃(体积分数比)可以指示O₃生成是VOCs控制还是NO_x控制. 今后需对OH·浓度、NO₂和O₃的光解速率等影响H₂O₂关键因素开展监测研究,此外,还需对我国特殊大气环境下H₂O₂对SO₄2-生成的贡献、不同地区H₂O₂/HNO₃指示O₃生成对NO_x或VOCs敏感性等方面开展更多的研究. 

Pollution Characteristics and Chemical Behaviors of Atmospheric Hydrogen Peroxide

Hydrogen peroxide (H₂O₂) is a reservoir and sink of free radicals, and also an important oxidant in the tropospheric atmosphere. Research into the literature was conducted to summarize publications about H₂O₂ since 1990s, including the formation route, pollution characteristics and the effect factors. The results showed that H₂O₂ exists in the atmosphere, cloud drops and particles. In the atmosphere, H₂O₂ is generated mainly through photolysis of O₃ and formaldehyde, reactions of VOCs and OH·/O₃, etc. Atmospheric concentrations of H₂O₂ range from nd to 8×10-9, with high concentrations around noon and low concentrations in the morning and in the evening on clear days. H₂O₂ concentrations increase with the increase of O₃ concentration and the decrease of NO_x and VOCs concentration. The increase of solar radiation and temperature or the decrease of relative humidity causes the increase of H₂O₂ concentration. The reaction in which H₂O₂ oxidizes sulfur dioxide to sulfuric acid is one of the most important reactions in aqueous-phase chemistry, leading to the formation of acid rain and the increase of secondary aerosol concentrations. In addition, the ratio of H₂O₂/HNO₃ indicates the limitation of VOC or NO_x in the O₃ formation. In the future, more work on the measurement of key factors such as OH· concentration and photolysis rate of NO₂ and O₃ that influence H₂O₂ formation should be carried out. More studies on H₂O₂′s contribution to SO₄2- formation and on the ratio of H₂O₂/HNO₃ as an indicator to ozone-NO_x-VOCs sensitivity in different regions under the special atmospheric environment in China should be carried out as well.