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

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 O-3 being a major sink for O-3 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 similar to 64%, and the overall detection limit for monoalkenes was similar to 10 nmol m(-2). On average, painted walls and glass windows sampled across the University of Colorado Boulder campus were coated by similar to 4 nm thick films containing similar to 20% alkenes, and a simple calculation indicates that the lifetime for these alkenes due to reaction with O-3 is similar to 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.