广东工业大学环境健康与污染控制研究院、环境科学与工程学院安太成教授团队青年百人副教授姬越蒙老师的论文《Reassessing the atmospheric oxidation mechanism of toluene》被《Proceedings of the National Academy of Sciences of The United States of America (PNAS,美国科学院院报)》杂志接受发表。众所周知，大气污染物甲苯的光化学反应可导致臭氧和二次气溶胶的产生，其对空气质量、人类健康和气候变化都有着至关重要的影响。目前普遍认为甲苯的光化学反应主要是由羟基自由基引发加成反应形成初级产物RO₂自由基，而该自由基进一步搭桥开环生成臭氧和二次气溶胶。然而对于其光化学产物的产率不同实验得到的结果出现很大差异，无法用上述机理进行合理解释。因此迄今为止，对于甲苯的大气光化学反应仍然存在很多不确定性。该论文通过理论和实验相结合的手段，首次揭示了和以往结果不同的甲苯光化学反应机理，发现甲苯首先和羟基自由基反应生成苯甲酚，其很容易进一步和氧气发生氢提取反应生成二级产物RO₂自由基，进而生成开环产物（图1）。研究表明大气中甲苯的光化学反应及其对臭氧和二次气溶胶的贡献需要重新评估，这将对当前大气科学研究重新评估相关大气模型的应用结果和准确测量其对臭氧和二次气溶胶的形成具有非常重要的意义。该论文主要与美国德州农工大学张人一教授等一起合作完成，也是我校首次以第一单位在该杂志上发表的研究性论文。下附图1和英文摘要：

图1

Abstract:Photochemical oxidation of aromatic hydrocarbonsleads totropospheric ozone and secondary organic aerosol (SOA) formation, with profound implications for air quality, human health, and climate. Toluene is the most abundant aromatic compound under urban environments, but itsdetailed chemical oxidation mechanism remains uncertain. From combined laboratory experiments and quantum chemical calculations, we show a toluene oxidation mechanism that is different from the one adopted in current atmospheric models. Our experimental work indicatesa dominant branching ratio for cresols, but a negligible formation of ring-opening products (e.g., methylglyoxal). Quantum chemical calculations also demonstrate that cresols are much more stable than their corresponding peroxy radicals and for the most favorable OH (ortho) addition the pathway of H-extraction by O₂to form the cresol proceeds with a smaller barrier than O₂-addition to form the peroxy radical. Our results reveal that phenolic formationrepresents the dominant pathway for toluene oxidation, highlighting the necessity to reassess its role in ozone and SOA formationin the atmosphere.

PNAS杂志主页请参见：http://www.pnas.org/,IF₂₀₁₆=10.414