Presence of siloxanes in the ambient air of urban Paris during the ACROSS field campaign
- 1Univ. Lyon, Université Claude Bernard Lyon1, CNRS, IRCELYON, 69626 Villeurbanne, France
- 2Université Paris Cité and Univ Paris Est Creteil, CNRS, LISA, F-75013 Paris, France
- 3Department of Chemistry, Harvey Mudd College, 301 Platt Blvd, Claremont, California 91711, United States
- 4Aix Marseille Université, CNRS, LCE, Marseille, France
- 5Univ Paris Est Creteil and Université Paris Cité, CNRS, LISA, F-94010 Créteil, France
Cyclic volatile methyl Siloxanes (cVMS) are a group of silicon-based organic compounds of anthropogenic origin that are found ubiquitously in the ambient air. They find wide application in many industrial, automotive products, consumer, and personal care products such as paints, solvents, adhesives, cosmetics, polymers, etc. About 90% of the environmentally released cyclic siloxanes diffuse directly into the atmosphere. They are high–production volume chemicals with some having an annual production rate of 45 to 227 thousand tons worldwide. Siloxanes have been observed in both urban and rural areas. Among the different siloxanes emitted into the atmosphere hexamethylcyclotrisiloxane (D3), octamethylcyclotetrasiloxane (D4), and decamethylcyclopentasiloxane (D5) are of great importance due to their subsequent concentrations. It should be mentioned that siloxanes are not readily biodegradable which means they can persist in the environment for a long duration. The D4 species has already been identified as a potential persistent organic pollutant (PoPs). D4 and D5 are very persistent and bioaccumulative and have evinced or potential hazards to both humans and the environment.
Taking advantage of the Vocus proton-transfer-reaction time-of-flight mass spectrometer (VOCUS PTR–TOF–MS) the D3, D4, and D5 species were measured in real-time downtown Paris in the June–July 2022 period. The measurements were performed during the ACROSS (Atmospheric ChemistRy Of the Suburban foreSt) field campaign at the urban site located at Université Paris Cité (48.83°N, 2.38°E) sampling at about 25 m above the ground level. The data collected during the summer 2022 showed that the mean concentrations were 0.099±0.009, 0.045±0.009, and 0.131±0.089 ppb for D3, D4, and D5, respectively. A strong diurnal cycle was observed for the different siloxanes. Concentrations for the D5 siloxane peaked in the morning with an averaged maximum of 0.298± 0.119 ppb while the 25th and the 75th quantile are 0.221 and 0.377 ppb, respectively. In the afternoon concentrations show a minimum value, followed by a slight increase during the night. The D5 is the most abundant siloxane species and shows the strongest diurnal cycle compared to the other two identified siloxanes. Observations during the campaign and the potential reaction products and sources of siloxanes will be discussed in this work.
KEYWORDS: Siloxanes; Cyclic Siloxanes; D3,D4 and D5; Ambient Air; PoPs; ACROSS; HR- Mass Spectrometry; VOCUS PTR-Tof
How to cite: Verma, R., Perrier, S., Michoud, V., Di Biagio, C., Gratien, A., Hawkins, L., D'Anna, B., Kammer, J., Monod, A., Cantrell, C., George, C., and Riva, M.: Presence of siloxanes in the ambient air of urban Paris during the ACROSS field campaign, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17469, https://doi.org/10.5194/egusphere-egu23-17469, 2023.
