State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, 100871 Beijing, China;
Beijing Innovation Center for Engineering Science and Advanced Technology, Peking University, 100871 Beijing, China.
Proc Natl Acad Sci U S A. 2021 Feb 9;118(6). doi: 10.1073/pnas.2018140118.
Outdoor ozone transported indoors initiates oxidative chemistry, forming volatile organic products. The influence of ozone chemistry on indoor air composition has not been directly quantified in normally occupied residences. Here, we explore indoor ozone chemistry in a house in California with two adult inhabitants. We utilize space- and time-resolved measurements of ozone and volatile organic compounds (VOCs) acquired over an 8-wk summer campaign. Despite overall low indoor ozone concentrations (mean value of 4.3 ppb) and a relatively low indoor ozone decay constant (1.3 h), we identified multiple VOCs exhibiting clear contributions from ozone-initiated chemistry indoors. These chemicals include 6-methyl-5-hepten-2-one (6-MHO), 4-oxopentanal (4-OPA), nonenal, and C8-C12 saturated aldehydes, which are among the commonly reported products from laboratory studies of ozone interactions with indoor surfaces and with human skin lipids. These VOCs together accounted for ≥12% molecular yield with respect to house-wide consumed ozone, with the highest net product yield for nonanal (≥3.5%), followed by 6-MHO (2.7%) and 4-OPA (2.6%). Although 6-MHO and 4-OPA are prominent ozonolysis products of skin lipids (specifically squalene), ozone reaction with the body envelopes of the two occupants in this house are insufficient to explain the observed yields. Relatedly, we observed that ozone-driven chemistry continued to produce 6-MHO and 4-OPA even after the occupants had been away from the house for 5 d. These observations provide evidence that skin lipids transferred to indoor surfaces made substantial contributions to ozone reactivity in the studied house.
室外臭氧传入室内会引发氧化反应，形成挥发性有机产物。臭氧化学对室内空气成分的影响尚未在通常有人居住的住宅中直接量化。在这里，我们在加利福尼亚州的一所住宅中探索了室内臭氧化学。这所住宅有两名成年居民居住。我们利用在 8 周的夏季活动中采集的臭氧和挥发性有机化合物（VOC）的时空分辨测量结果进行研究。尽管室内臭氧浓度总体较低（平均值为 4.3 ppb），且室内臭氧衰减常数相对较低（1.3 h），但我们还是在室内识别出了多种明显受到臭氧引发的化学反应影响的 VOC。这些化学物质包括 6-甲基-5-庚烯-2-酮（6-MHO）、4-氧代戊醛（4-OPA）、壬醛和 C8-C12 饱和醛，这些物质都是实验室研究臭氧与室内表面以及与人体皮肤脂质相互作用时通常会报告的产物。这些 VOC 加起来占室内消耗臭氧的 12%以上的分子产率，其中正壬醛的净产物产率最高（≥3.5%），其次是 6-MHO（2.7%）和 4-OPA（2.6%）。尽管 6-MHO 和 4-OPA 是皮肤脂质（特别是角鲨烯）的重要臭氧分解产物，但这所住宅中两名居住者的身体包裹物与臭氧的反应不足以解释所观察到的产率。相关地，我们观察到即使在居住者离开房屋 5 天后，臭氧驱动的化学过程仍在继续产生 6-MHO 和 4-OPA。这些观察结果提供了证据，表明转移到室内表面的皮肤脂质对所研究住宅中臭氧的反应性做出了重大贡献。
