Photolysis of Atmospherically Relevant Carbonyl Compounds in Different Solutions
Stephanie H. Kim, Claire R. Engelmann
Mentor: Sergey Nizkorodov
Carbonyl compounds in the atmosphere, namely aldehydes and ketones, are involved in the formation of
tropospheric ozone and photochemical smog, and account for much of the chemical reactivity and toxicity of
secondary organic aerosols (SOA) and primary organic aerosols (POA). Therefore, it is important to study
their formation and removal mechanisms to better understand their active roles in atmospheric processes.
Carbonyl compounds are also known to readily photodegrade in the presence of solar radiation to give rise to
secondary products. However, condensed-phase photolysis of these carbonyl compounds in water and in
organic matrices (particulate matter) has not been extensively studied. (1R)-(+)-camphor and 1,2cyclohexanedione were selected to model the gas, liquid, and solid-phase photolysis of atmospherically
relevant carbonyl compounds using broadband 300–400 nm and 254 nm UV radiation. Solutions of
carbonyls were prepared in various organic solvents, then photolyzed in the gas or liquid-phase using a Teflon
bag or filtered lamp setup, respectively. Solid carbonyl compounds were photolyzed at different temperatures
using a custom-made photolysis setup. The gas-phase products were analyzed by proton transfer reactionmass spectrometry (PTR-MS), while the liquid and solid-phase products were analyzed by high performance
liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GCMS). Extinction coefficients
of (1R)-(+)-camphor and 1,2-cyclohexanedione were also experimentally derived using UV-Vis analysis. The
results revealed that camphor was highly resilient to photolysis compared to the fast photodegradation of 1,2cyclohexanedione; however, preliminary data indicated product formation from both compounds. Further
analysis will be done to identify these products.