Secondary organic aerosol formation from the oxidation of decamethylcyclopentasiloxane at atmospherically relevant OH concentrations

Abstract. Decamethylcyclopentasiloxane (D5, C10H30O5Si5) is measured at parts per trillion (ppt) levels outdoors and billion (ppb) indoors. Primarily used in personal care products, its outdoor concentration correlated to population density. Since understanding the aerosol formation potential of volatile chemical products critical particulate matter urban areas, secondary organic yield D5 was studied under a wide range OH concentrations and, correspondingly, exposures using both batch-mode chamber continuously run flow tube experiments. These results were comprehensively analyzed compared two other (SOA) datasets from literature. It found that SOA oxidation extremely dependent on either or exposure. For ≲ 107 molec.cm-3 2 × 1011 molec.scm-3, largely < 5 % usually ∼ 1 %. This significantly lower than yields previously reported. Using two-product absorptive partitioning model for upper bound yields, stoichiometric mass fraction coefficients are, first product, α1 = 0.056 KOM,1 0.022 m3 µg−1; second they are α2 7.7 KOM,2 4.3 10−5 µg−1. Generally, there high (> 90 %) mixing ratios 109 above 1012 molec.scm-3.