The photochemical formation and gas–particle partitioning of oxidation products of decamethyl cyclopentasiloxane and decamethyl tetrasiloxane in the atmosphere

Chandramouli, B.; Kamens, Richard M.

doi:10.1016/s1352-2310(00)00289-2

Cited by 37 publications

(35 citation statements)

References 16 publications

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“…These ions may correspond to [M – 31] + and [M – 47] + fragment ions of a silanol that would be called D 5 TOH according to the abbreviated siloxane nomenclature. A previous study identified the analogous silanol D 4 TOH as a product of the reaction of D 5 with OH, and major fragments in the spectra of D 4 TOH are the [M – 31] + and [M – 47] + ions. Another study identified D 3 TOH as a degradation product of D 4 .…”

Section: Resultsmentioning

confidence: 99%

Rate Constants and Activation Energies for Gas‐Phase Reactions of Three Cyclic Volatile Methyl Siloxanes with the Hydroxyl Radical

Safron

Strandell

Kierkegaard

et al. 2015

Int J of Chemical Kinetics

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Reaction with hydroxyl radicals (OH) is the major pathway for removal of cyclic volatile methyl siloxanes (cVMS) from air. We present new measurements of second‐order rate constants for reactions of the cVMS octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), and dodecamethylcyclohexasiloxane (D6) with OH determined at temperatures between 313 and 353 K. Our measurements were made using the method of relative rates with cyclohexane as a reference substance and were conducted in a 140‐mL gas‐phase reaction chamber with online mass spectrometry analysis. When extrapolated to 298 K, our measured reaction rate constants of D4 and D5 with the OH radical are 1.9 × 10−12 (95% confidence interval (CI): (1.7–2.2) × 10−12) and 2.6 × 10−12 (CI: (2.3–2.9) × 10−12) cm3 molecule−1 s−1, respectively, which are 1.9× and 1.7× faster than previous measurements. Our measured rate constant for D6 is 2.8 × 10−12 (CI: (2.5–3.2) × 10−12) cm3 molecule−1 s−1 and to our knowledge there are no comparable laboratory measurements in the literature. Reaction rates for D5 were 33% higher than for D4 (CI: 30–37%), whereas the rates for D6 were only 8% higher than for D5 (CI: 5–10%). The activation energies of the reactions of D4, D5, and D6 with OH were not statistically different and had a value of 4300 ± 2800 J/mol.

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Section: Resultsmentioning

confidence: 99%

Rate Constants and Activation Energies for Gas‐Phase Reactions of Three Cyclic Volatile Methyl Siloxanes with the Hydroxyl Radical

Safron

Strandell

Kierkegaard

et al. 2015

Int J of Chemical Kinetics

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“…Because of the method of collection (the product was collected from rinsing the environmental chamber walls with solvent) confirmation of secondary aerosol production from D 4 oxidation was not possible from Sommerlade et al (1993). Chandramouli and Kamens (2001) reacted D 5 in a smog chamber, with separate analysis of gas and aerosol products, confirming the presence of D 4 TOH in the GS/MS analysis of the condensed aerosol phase.…”

Section: Introductionmentioning

confidence: 99%

Comprehensive atmospheric modeling of reactive cyclic siloxanes and their oxidation products

2017

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Abstract. Cyclic volatile methyl siloxanes (cVMSs) are important components in personal care products that transport and react in the atmosphere. Octamethylcyclotetrasiloxane (D 4 ), decamethylcyclopentasiloxane (D 5 ), dodecamethylcyclohexasiloxane (D 6 ), and their gas-phase oxidation products have been incorporated into the Community Multiscale Air Quality (CMAQ) model. Gas-phase oxidation products, as the precursor to secondary organic aerosol from this compound class, were included to quantify the maximum potential for aerosol formation from gas-phase reactions with OH. Four 1-month periods were modeled to quantify typical concentrations, seasonal variability, spatial patterns, and vertical profiles. Typical model concentrations showed parent compounds were highly dependent on population density as cities had monthly averaged peak D 5 concentrations up to 432 ng m −3 . Peak oxidized D 5 concentrations were significantly less, up to 9 ng m −3 , and were located downwind of major urban areas. Model results were compared to available measurements and previous simulation results. Seasonal variation was analyzed and differences in seasonal influences were observed between urban and rural locations. Parent compound concentrations in urban and peri-urban locations were sensitive to transport factors, while parent compounds in rural areas and oxidized product concentrations were influenced by large-scale seasonal variability in OH.

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“…Atmospheric measurements of cyclic siloxanes have been performed in ambient air (McLachlan et al, 2010;Genualdi et al, 2011;Yucuis et al, 2013;Ahrens et al, 2014;Kierkegaard and McLachlan, 2013;Krogseth et al, 2013b, a;Buser et al, 2013a;Companioni-Damas et al, 2014). Higher concentration microenvironments have also been surveyed through measurement (wastewater treatment plants, landfills, and indoor air) (Krogseth et al, 2013b;Cheng et al, 2011;Wang et al, 2001;Pieri et al, 2013;Yucuis et al, 2013;Companioni-Damas et al, 2014;Tang et al, 2015). In several instances, model-measurement comparison has been conducted and, to a large extent, confirmed our understanding of emissions, fate and transport.…”

Section: Introductionmentioning

confidence: 86%

Authors’ Response

Janechek¹

2017

Preprint

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Cyclic volatile methyl siloxanes (cVMSs) are important components in personal care products that transport and react in the atmosphere. Octamethylcyclotetrasiloxane (D 4), decamethylcyclopentasiloxane (D 5), dodecamethylcyclohexasiloxane (D 6), and their gas-phase oxidation products have been incorporated into the Community Multiscale Air Quality (CMAQ) model. Gas-phase oxidation products, as the precursor to secondary organic aerosol from this compound class, were included to quantify the maximum potential for aerosol formation from gas-phase reactions with OH. Four 1-month periods were modeled to quantify typical concentrations, seasonal variability, spatial patterns, and vertical profiles. Typical model concentrations showed parent compounds were highly dependent on population density as cities had monthly averaged peak D 5 concentrations up to 432 ng m −3. Peak oxidized D 5 concentrations were significantly less, up to 9 ng m −3 , and were located downwind of major urban areas. Model results were compared to available measurements and previous simulation results. Seasonal variation was analyzed and differences in seasonal influences were observed between urban and rural locations. Parent compound concentrations in urban and peri-urban locations were sensitive to transport factors, while parent compounds in rural areas and oxidized product concentrations were influenced by large-scale seasonal variability in OH.

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The photochemical formation and gas–particle partitioning of oxidation products of decamethyl cyclopentasiloxane and decamethyl tetrasiloxane in the atmosphere

Cited by 37 publications

References 16 publications

Rate Constants and Activation Energies for Gas‐Phase Reactions of Three Cyclic Volatile Methyl Siloxanes with the Hydroxyl Radical

Rate Constants and Activation Energies for Gas‐Phase Reactions of Three Cyclic Volatile Methyl Siloxanes with the Hydroxyl Radical

Comprehensive atmospheric modeling of reactive cyclic siloxanes and their oxidation products

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