Volatile Methyl Siloxanes as Potential Hazardous Air Pollutants

Gaj, Kazimierz; Pakuluk, Anna

doi:10.15244/pjoes/34668

Cited by 26 publications

(8 citation statements)

References 26 publications

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“…The degradation caused by siloxanes typically translates into a significant decrease in VOC sensitivity and a strong increase of response time, potentially caused by silicon dioxide (SiO 2 ) formation [ 6 , 29 ]. Unfortunately, silicon-containing compounds are found in many products used in everyday life such as cosmetics, cleaning agents or plastic parts [ 30 , 31 , 32 , 33 ] and, therefore, siloxanes are present in all relevant operational environments. In fact, recent studies have shown that siloxanes are the most abundant volatile organic compound (VOC) emitted by humans due to their extensive use in personal care products such as antiperspirants [ 34 ].…”

Section: Resultsmentioning

confidence: 99%

“…For this, the sensors are characterized in a GMS with clean zero air and a fixed concentration of a target gas, in this case ethanol at 10 ppm. Subsequently, the sensors are operated in an atmosphere containing an elevated concentration of 250 ppm of D5 for up to 200 h. D5 is chosen as it is the most abundant siloxane in most environments and commercial products [ 30 , 31 , 32 , 33 ]. Concentration and exposure time are chosen to approximate 10 years of operation in a background of 40 ppb of siloxanes [ 35 ].…”

Section: Resultsmentioning

confidence: 99%

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New Digital Metal-Oxide (MOx) Sensor Platform

Rüffer

Hoehne

Bühler

2018

Sensors

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The application of metal oxide gas sensors in Internet of Things (IoT) devices and mobile platforms like wearables and mobile phones offers new opportunities for sensing applications. Metal-oxide (MOx) sensors are promising candidates for such applications, thanks to the scientific progresses achieved in recent years. For the widespread application of MOx sensors, viable commercial offerings are required. In this publication, the authors show that with the new Sensirion Gas Platform (SGP) a milestone in the commercial application of MOx technology has been reached. The architecture of the new platform and its performance in selected applications are presented.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

New Digital Metal-Oxide (MOx) Sensor Platform

Rüffer

Hoehne

Bühler

2018

Sensors

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“…(3) surface reduction with the rate constant k red . This also accounts for the fact that the type of surface oxygen taking part in the reaction (which was stated above to be O − ) and specific reaction processes depend on the sensor temperature and are still discussed in the literature (Barsan and Weimar, 2001;Gurlo, 2006), so we want to emphasize that k ox and k red can also represent other reaction processes resulting in generation or reduction of surface charge.…”

Section: Sensor Modelmentioning

confidence: 98%

Siloxane treatment of metal oxide semiconductor gas sensors in temperature-cycled operation – sensitivity and selectivity

Schultealbert

Uzun

Baur

et al. 2020

J. Sens. Sens. Syst.

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Abstract. The impact of a hexamethyldisiloxane (HMDSO) treatment on the response of doped SnO2 sensors is investigated for acetone, carbon monoxide and hydrogen. The sensor was operated in temperature cycles based on the DSR concept (differential surface reduction). According to this concept, the rate constants for the reduction and oxidation of the surface after fast temperature changes can be evaluated and used for quantification of reducing gases as well as quantification and compensation of sensor poisoning by siloxanes, which is shown in this work. Increasing HMDSO exposure reduces the rate constants and therefore the sensitivity of the sensor more and more for all processes. On the other hand, while the rate constants for acetone and carbon monoxide are reduced nearly to zero already for short treatments, the hydrogen sensitivity remains fairly stable, which greatly increases the selectivity. During repeated HMDSO treatment the quasistatic sensitivity, i.e. equilibrium sensitivity at one point during the temperature cycle, rises at first for all gases but then drops rapidly for acetone and carbon monoxide, which can also be explained by reduced rate constants for oxygen chemisorption on the sensor surface when considering the generation of surface charge.

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“…However, more recent studies estimate a degradation rate constant of (2.6 + 0.3) Â 10 -12 cm 3 molecule -1 s -1 (Safron et al, 2015), the one considered in this study and in agreement with that found by Xiao et al (2015), 2.46 (2.74 -2.20, confidence interval [CI] 95%) Â 10 -12 cm 3 molecule -1 s -1 . The D5 reaction with OH accounts for the main transformations of siloxanes in the atmosphere, whereas other phenomena such as photochemical reactions with NO 3 radicals and ozone are minimal and can be considered negligible for our purpose (Gaj and Pakuluk, 2015). The activation energy suggested by Safron et al (2015) was used to correct the degradation rate constant for temperature (4.3 + 2.8 kJ mol -1 , approximately 1.02 kcal mol -1 ), which is also in the same range as the values found by Xiao et al (2015), 0.79 (1.38 -0.21, CI 95%) kcal mol -1 .…”

Section: Modeling Strategy and Parameterizationmentioning

confidence: 99%

Characterizing the regional concentrations and seasonality of the emerging pollutant decamethylcyclopentasiloxane (D5) using a WRF+CHIMERE modeling approach

Jiménez‐Guerrero

Ratola

2021

Elementa: Science of the Anthropocene

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In this study, the results from two passive air sampling campaigns (winter and summer) performed previously in 8 different urban sites allowed the inclusion of the volatile methyl siloxane (VMS) D5 in a chemistry transport model (WRF+CHIMERE modeling system) to assess its performance in describing the concentrations and seasonal distribution of this emergent contaminant in a domain covering the western Iberian Peninsula. The model estimations were evaluated using the available field-based data, and the WRF+CHIMERE approach showed, in general, errors under 50% for all sampling sites and seasons, with a slight tendency to underestimations of D5 concentrations when using the lowest emission factor among those selected from the literature and to very large overestimations when using the highest emission factor available. The greatest errors are found for remote sampling points (substantial overestimations of the models at Midões, by even a factor of 3) and for coastal ones (where population and therefore emissions exhibit strong seasonality). The results also indicate that the chemical sinks by OH degradation play a negligible role on the ground-level concentrations of D5 at the scale of the investigated domain, with average contributions under 0.5%. Despite the lack of data regarding D5 emissions in the area, which led to the assumption of emission rates taken from other countries (and a constant population in the domain), the results of this first study are excellent and highlight the skill of WRF+CHIMERE in reproducing D5 concentrations. Indeed, the nature of the proposed modeling tool is helpful for understanding the processes conditioning the present and future behavior of contaminants like D5. Moreover, the model is bound to allow the future inclusion of D5 (and other VMSs) in regulatory scenarios, since restrictions on the use of these chemicals have just started to be introduced.

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Volatile Methyl Siloxanes as Potential Hazardous Air Pollutants

Cited by 26 publications

References 26 publications

New Digital Metal-Oxide (MOx) Sensor Platform

New Digital Metal-Oxide (MOx) Sensor Platform

Siloxane treatment of metal oxide semiconductor gas sensors in temperature-cycled operation – sensitivity and selectivity

Characterizing the regional concentrations and seasonality of the emerging pollutant decamethylcyclopentasiloxane (D5) using a WRF+CHIMERE modeling approach

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