Seasonal and latitudinal variability in the atmospheric concentrations of cyclic volatile methyl siloxanes in the Northern Hemisphere

Wania, Frank; Warner, Nicholas A.; McLachlan, Michael S.; Durham, Jeremy; Miøen, Merete; Lei, Ying Duan; Xu, Shihe

doi:10.1039/d2em00467d

Cited by 3 publications

(4 citation statements)

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“…Furthermore, the error of the regression slope provides an indirect estimate of the precision of sampling, extraction, and quantification. We also note that replicate precision of XAD-PAS deployments and analyses has been studied numerous times before. , …”

Section: Methodsmentioning

confidence: 82%

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Field Calibration and PAS-SIM Model Evaluation of the XAD-Based Passive Air Sampler for Semi-Volatile Organic Compounds

Zhan

Lei

et al. 2023

Environ. Sci. Technol.

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The use of passive air samplers (PAS) for semi-volatile organic compounds (SVOCs) continues to expand. To advance quantitative understanding of uptake kinetics, we calibrated the XAD-PAS, using a styrene–divinylbenzene sorbent, through a year-long side-by-side deployment with an active sampler. Twelve XAD-PASs, deployed in June 2020, were retrieved at 4-week intervals, while gas phase SVOCs were quantified in 48 consecutive week-long active samples taken from June 2020 to May 2021. Consistent with XAD’s high uptake capacity, even relatively volatile SVOCs, such as hexachlorobutadiene, displayed linear uptake throughout the entire deployment. Sampling rates (SRs) range between 0.1 and 0.6 m3 day–1 for 26 SVOCs, including brominated flame retardants, organophosphate esters, and halogenated methoxylated benzenes. SRs are compared with experimental SRs reported previously. The ability of the existing mechanistic uptake model PAS-SIM to reproduce the observed uptake and SRs was evaluated. Agreement between simulated and measured uptake curves was reasonable but varied with compound volatility and the assumed stagnant air layer boundary thickness. Even though PAS-SIM succeeds in predicting the SR range for the studied SVOCs, it fails to capture the volatility dependence of the SR by underestimating the length of the linear uptake period and by failing to consider the kinetics of sorption.

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Section: Methodsmentioning

confidence: 82%

“…We also note that replicate precision of XAD-PAS deployments and analyses has been studied numerous times before. 33,39 2.2. Sample Treatment.…”

Section: Methodsmentioning

confidence: 99%

Field Calibration and PAS-SIM Model Evaluation of the XAD-Based Passive Air Sampler for Semi-Volatile Organic Compounds

Zhan

Lei

et al. 2023

Environ. Sci. Technol.

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“…Data from our study site when combined with previous data in the literature show that there is a strong and statistically significant relationship ( R 2 = 0.59, p < 0.001) between log D5 concentrations and the log of average population density within 10 km of the location in which the measurements were conducted (Figure , Figure S3). ,,− ,− ,,, We selected 10 km because it was the strongest predictor out of the distances we tested between 1 and 20 km. Furthermore, the agreement between our data and the historical trend shows that the per capita emission rate of D5 in the United States has not significantly declined despite industry suggestions that EU restrictions may be causing a voluntary phase out of VMS in U.S. manufacturing. , However, comparisons between our data and previous VMS measurements also show that the relationship between concentration and population density is not as strong for all VMS congeners.…”

Section: Resultsmentioning

confidence: 99%

“…A number of previous studies employing field measurements and atmospheric models have provided estimates of atmospheric VMS concentrations in areas ranging from remote parts of the arctic to major cities, with the majority of work to date occurring in the United States, Western Europe, or Eastern Asia. ,,,− One trend consistently observed in these studies is that concentrations of all VMS congeners tend to be higher in densely populated urban areas. ,,,, This is unsurprising given that the primary emissions source of VMS is personal care products and other volatile chemical products. Even though the emissions and concentrations of VMS tend to be very high in these areas, measurements of VMS concentrations in large cities remain scarce.…”

Section: Introductionmentioning

confidence: 97%

Concentrations of Volatile Methyl Siloxanes in New York City Reflect Emissions from Personal Care and Industrial Use

Brunet,

Marek,

Stanier

et al. 2024

Environ. Sci. Technol.

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Volatile methyl siloxanes (VMS) are a group of organosilicon compounds of interest because of their potential health effects, their ability to form secondary organic aerosols, and their use as tracer compounds. VMS are emitted in the gas-phase from using consumer and personal care products, including deodorants, lotions, and hair conditioners. Because of this emission route, airborne concentrations are expected to increase with population density, although there are few studies in large urban centers. Here, we report summertime concentrations and daily variations of VMS congeners measured in New York City. Median concentrations of the 6 studied congeners, D3 (20 ng m–3), D4 (57 ng m–3), D5 (230 ng m–3), D6 (11 ng m–3), L5 (2.5 ng m–3), and L7 (1.3 ng m–3) are among the highest reported outdoor concentrations in the literature to date. Average congener ratios of D5:D4 and D5:D6 were consistent with previously reported emissions ratios, suggesting that concentrations were dominated by local emissions. Measured concentrations agree with previously published results from a Community Multiscale Air Quality model and support commonly accepted emissions rates for D4, D5, and D6 of 32.8, 135, and 6.1 mg per capita per day. Concentrations of D4, D5, D6, L5, and L7 and total VMS were significantly lower during the day than during the night, consistent with daytime oxidation reactivity. Concentrations of D3 did not show the same diurnal trend but exhibited a strong directional dependence, suggesting that it may be emitted by industrial point sources in the area rather than personal care product use. Concentrations of all congeners had large temporal variations but showed relatively weak relationships with wind speed, temperature, and mixing height.

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Rate Coefficients for the Cl Atom Gas‐Phase Reaction With Permethylsiloxanes (PMS): L₂, L₃, L₄, L₅, D₃, D₄, D₅, and D₆

Van Hoomissen,

Chattopadhyay,

Burkholder

2024

Int J of Chemical Kinetics

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Rate coefficients, k(T), for the gas‐phase Cl atom reaction with hexamethyldisiloxane ((CH3)3SiOSi(CH3)3, L2), k1; octamethyltrisiloxane ([(CH3)3SiO]2Si(CH3)2, L3), k2; decamethyltetrasiloxane ((CH3)3SiO[Si(CH3)2O]2Si(CH3)3, L4, k3; dodecamethylpentasiloxane ((CH3)3SiO[Si(CH3)2O]3Si(CH3)3, L5, k4; hexamethylcyclotrisiloxane ([‐Si(CH3)2O‐]3, D3), k5; octamethylcyclotetrasiloxane ([‐Si(CH3)2O‐]4, D4), k6; decamethylcyclopentasiloxane ([‐Si(CH3)2O‐]5, D5, k7), and dodecamethylcyclohexasiloxane ([‐Si(CH3)2O‐]6, D6, k8) were measured over a range of temperature (273–363 K) using a pulsed laser photolysis (PLP) – resonance fluorescence (RF) technique. The obtained k(296 K) and Arrhenius expressions with 2σ uncertainties including estimated systematic errors are (in units of 10−10 cm3 molecule−1 s−1): L2: k1(296 K) = (1.58 ± 0.07) k1(273–363 K) = (1.36 ± 0.10) exp((43 ± 249)/T) L3: k2(296 K) = (1.93 ± 0.09) k2(273–353 K) = (1.95 ± 0.18) exp((1 ± 632)/T) L4: k3(296 K) = (2.36 ± 0.12) k3(273–353 K) = (2.09 ± 0.16) exp((43± 522)/T) L5: k4(296 K) = (2.84 ± 0.19) k4(296–353 K) = (2.70 ± 0.18) exp((15 ± 490)/T) D3: k5(296 K) = (0.588 ± 0.028) k5(273–353 K) = (0.47 ± 0.03) exp((78 ± 470)/T) D4: k6(296 K) = (1.13 ± 0.06) k6(273–353 K) = (1.14 ± 0.07) exp((4 ± 432)/T) D5: k7(296 K) = (1.72 ± 0.09) k7(273–353 K) = (1.60 ± 0.10) exp((22 ± 432)/T) D6: k8(296 K) = (2.16 ± 0.14) k8(296–353 K) = (1.73 ± 0.14) exp((71 ± 562)/T) The cyclic permethyl siloxanes (cyclic PMS) were found to be less reactive than the analogous linear permethyl siloxane (linear PMS) with an equal number of CH3‐ groups. Both linear and cyclic compounds show a linear relationship between the measured rate coefficient and the number of CH3‐ groups in the molecule. A structure–activity relationship (SAR) is presented that reproduces the experimental data to within ∼10% at all temperatures. For [Cl] ≈ 104 atom cm−3, an approximate free troposphere abundance, the PMS loss due to Cl atom reaction leads to relatively short estimated lifetimes of 7, 6, 5, 4, 20, 10, 7, and 5 days for L2, L3, L4, L5, D3, D4, D5, and D6, respectively. Therefore, the PMSs included in this study are classified as atmospherically very short‐lived substances and Cl atom reaction represents a significant loss process.

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Seasonal and latitudinal variability in the atmospheric concentrations of cyclic volatile methyl siloxanes in the Northern Hemisphere

Abstract: The spatial and temporal patterns in the concentrations of D4, D5 and D6 in the atmosphere measured with passive samplers along a European and a Canadian transect are largely consistent with the current understanding of their atmospheric fate.

Cited by 3 publications

References 38 publications

Field Calibration and PAS-SIM Model Evaluation of the XAD-Based Passive Air Sampler for Semi-Volatile Organic Compounds

Field Calibration and PAS-SIM Model Evaluation of the XAD-Based Passive Air Sampler for Semi-Volatile Organic Compounds

Concentrations of Volatile Methyl Siloxanes in New York City Reflect Emissions from Personal Care and Industrial Use

Rate Coefficients for the Cl Atom Gas‐Phase Reaction With Permethylsiloxanes (PMS): L₂, L₃, L₄, L₅, D₃, D₄, D₅, and D₆

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Seasonal and latitudinal variability in the atmospheric concentrations of cyclic volatile methyl siloxanes in the Northern Hemisphere

Abstract: The spatial and temporal patterns in the concentrations of D4, D5 and D6 in the atmosphere measured with passive samplers along a European and a Canadian transect are largely consistent with the current understanding of their atmospheric fate.

Cited by 3 publications

References 38 publications

Field Calibration and PAS-SIM Model Evaluation of the XAD-Based Passive Air Sampler for Semi-Volatile Organic Compounds

Field Calibration and PAS-SIM Model Evaluation of the XAD-Based Passive Air Sampler for Semi-Volatile Organic Compounds

Concentrations of Volatile Methyl Siloxanes in New York City Reflect Emissions from Personal Care and Industrial Use

Rate Coefficients for the Cl Atom Gas‐Phase Reaction With Permethylsiloxanes (PMS): L2, L3, L4, L5, D3, D4, D5, and D6

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Rate Coefficients for the Cl Atom Gas‐Phase Reaction With Permethylsiloxanes (PMS): L₂, L₃, L₄, L₅, D₃, D₄, D₅, and D₆