Evidence and evolution of Criegee intermediates, hydroperoxides and secondary organic aerosols formedviaozonolysis of α-pinene

Abstract

The first experimental evidence of Criegee intermediates formed via α-pinene ozonolysis and the formation of secondary organic aerosols is reported using a rapid scan time-resolved FTIR spectrometer coupled with a long-path aerosol cooling chamber.

Infrared detection of Criegee intermediates

“…To study ozonolysis of monoterpenes under atmospherically relevant conditions, an aerosol cooling chamber has been constructed, which is comprised of three major compartments, including (a) a main investigation chamber in which ozonolysis of alkenes takes place; (b) a cooling agent chamber, which is filled with cooling agent during operation to modulate the temperature of the main chamber, such as liquid nitrogen, or other cooling agents; and (c) a vacuum chamber, which is used to prevent the heat exchange between the main chamber and the surrounding. [ 23 ] The main chamber is equipped with three Au‐coated mirrors installed in a multipass, White‐optics based configuration so that the path length can be readily adjusted up to tens of meters. The temperature and pressure in the aerosol cooling chamber were continuously monitored by a silicon diode (Sensor type DT 470, LakeShore Cryotronics) and a diaphragm gauge (Sensor type CDG025D, INFICON), respectively.…”

“…Schematics of the aerosol cooling chamber coupled to the rapid‐scan FTIR spectrometer [ 23 ] (Reproduced from Reference [22] with permission from the Royal Society of Chemistry)…”

“…Temporal evolution of the measured infrared spectra during ozonolysis of α‐pinene at 298 K. The tilted baselines shown with increasing time is an indication of aerosol growth [ 23 ] (Reproduced from Reference [22] with permission from the Royal Society of Chemistry)…”

“…Despite their atmospheric significance, however, due to the high reactive nature of CIs, the direct experimental observation of gas‐phase CIs produced from ozonolysis of alkenes is technically challenging. [ 20–23 ] For example, the experimental study of chemical ionization mass spectrometry estimated that the steady‐state concentration of the simplest CI, CH 2 OO, from ozonolysis reaction is only within 10 8 molecule cm −3 . [ 21 ] In 2012, Taatjes and co‐workers demonstrated that stabilized CH 2 OO can be produced efficiently, up to 10 14 molecule cm −3 , by utilizing the reaction of CH 2 I + O 2 → CH 2 OO + I, where the CH 2 I radical was produced from the ultraviolet (UV) photolysis of diiodomethane (CH 2 I 2 ).…”

Recent studies on pinene and its biological and pharmacological activities

“…α-pinene, the most abundant monoterpene in the atmosphere, accounts for more than 50 % of global monoterpene emissions and is a major component of phytoncides (Bagchi et al, 2020[ 2 ]; Li et al, 2009[ 27 ]). Phytoncides are antimicrobial allelochemical volatile organic compounds that are related to forest healing and activation of recreational forests.…”