Details:

Journal Title:
ACS Environmental Au
Personal Author:
Alton, Mitchell W. ; Browne, Eleanor C.
Alton, Mitchell W. ; Browne, Eleanor C. Less -
NOAA Program & Office:
CIRES (Cooperative Institute for Research in Environmental Sciences)
Description:
Cyclic volatile methyl siloxanes (cVMS) are anthropogenic chemicals that have come under scrutiny due to their widespread use and environmental persistence. Significant data on environmental concentrations and persistence of these chemicals exists, but their oxidation mechanism is poorly understood, preventing a comprehensive understanding of the environmental fate and impact of cVMS. We performed experiments in an environmental chamber to characterize the first-generation oxidation products of hexamethylcyclotrisiloxane (D3), octamethylcyclotetrasiloxane (D4), and decamethylcyclopentasiloxane (D5) under different peroxy radical fates (unimolecular reaction or bimolecular reaction with either NO or HO2) that approximate a range of atmospheric compositions. While the identity of the oxidation products from D3 changed as a function of the peroxy radical fate, the identity and yield of D4 and D5 oxidation products remained largely constant. We compare our results against the output from a kinetic model of cVMS oxidation chemistry. The reaction mechanism used in the model is developed using a combination of previously proposed cVMS oxidation reactions and standard atmospheric oxidation radical chemistry. We find that the model is unable to reproduce our measurements, particularly in the case of D4 and D5. The products that are poorly represented in the model help to identify possible branching points in the mechanism, which require further investigation. Additionally, we estimated the physical properties of the cVMS oxidation products using structure–activity relationships and found that they should not be significantly partitioned to organic or aqueous aerosol. The results suggest that cVMS first-generation oxidation products are also long-lived in the atmosphere and that environmental monitoring of these compounds is necessary to understand the environmental chemistry and loading of cVMS.
Keywords:
[+]
Environmental Engineering Environmental Science (miscellaneous) Water Science And Technology
Source:
ACS Environmental Au, 2(3), 263-274
DOI:
https://doi.org/10.1021/acsenvironau.1c00043
ISSN:
2694-2518;2694-2518;
Format:
PDF
Publisher:
American Chemical Society (ACS)
Document Type:
Journal Article
License:
https://creativecommons.org/licenses/by-nc-nd/4.0/
Rights Information:
CC BY-NC-ND
Compliance:
Submitted
Main Document Checksum:
[+]
urn:sha256:eaf79a4cb601f070af44a908ff2ba83b3ad78071838c66e591f409b16b2cf252
Download URL:
https://repository.library.noaa.gov/view/noaa/51854/noaa_51854_DS1.pdf
File Type:

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