Abstract
Personal care products can release decamethylcyclopentasiloxane (D(5)) to the atmosphere, where it oxidizes to form 1-hydroxynonamethylcyclopentasiloxane (D(4)TOH). This oxidation product subsequently can partition to the particle-phase to form secondary organic aerosol (SOA). The gas-particle distribution of D(4)TOH has been studied in the laboratory but has yet to be established in ambient air. This study examines the gas-particle distribution of D(4)TOH and related oxidation products in New York City during the summertime of 2022 using medium volume air samplers, solvent extraction, and gas and liquid chromatography mass spectrometry methods. Positive sampling artifacts constituted the majority of D(4)TOH observed on quartz fiber filters (54-100%, averaging 86%, n = 12), indicating the high potential for particle-phase D(4)TOH to be overestimated. After artifact correction, D(4)TOH was observed in fine particles in 5 of the 12 sampling periods, with its particle-phase fraction averaging 13%. Because D(4)TOH is predominantly in the gas phase, it makes a minor contribution to D(5)-derived SOA during summertime. Further oxidation products of D(5), including di, and tetrasiloxanols are predominantly in the particle-phase (>77%, n = 4) during summertime and have relatively small positive artifacts. These polysiloxanols provide evidence of D(5)-derived SOA in the urban aerosols and are more suitable tracers for D(5)-derived SOA than D(4)TOH in summertime because of their higher particle-phase fractions.