Quantification of alkenes on indoor surfaces and implications for chemical sources and sinks: Fid-Bau Portal

Quantification of alkenes on indoor surfaces and implications for chemical sources and sinks

Deming, Benjamin L. / Ziemann, Paul J.

Indoor surfaces are known to support organic films, but their thickness, composition, and variability between environments remain poorly characterized. Alkenes are expected to be a significant component of these films, with the reaction with O₃ being a major sink for O₃ and source of airborne chemicals. Here, we present a sensitive, microscale, nanospectrophotometric method for quantifying the alkene (C=C bond) content of surface films and demonstrate its applicability in five studies relevant to indoor air chemistry. Collection efficiencies determined for a filter wipe method were ~64%, and the overall detection limit for monoalkenes was ~10 nmol m⁻². On average, painted walls and glass windows sampled across the University of Colorado Boulder campus were coated by ~4 nm thick films containing ~20% alkenes, and a simple calculation indicates that the lifetime for these alkenes due to reaction with O₃ is ~1 hour, indicating that the films are highly dynamic. Measurements of alkenes in films of skin oil, pan‐fried cooking oils, a terpene‐containing cleaner, and on various surfaces in a closed classroom overnight (where carboxyl groups were also measured) provided insight into the effects of chemical and physical processes on film and air composition.