Sewage and Organic Pollution Compounds in Nairobi River Urban Sediments Characterized by Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT–ICR–MS)

Downham, Rory P.; Vane, Christopher H. ORCID: https://orcid.org/0000-0002-8150-3640; Gannon, Benedict; Olaka, Lydia A.; Barrow, Mark P.. 2024 Sewage and Organic Pollution Compounds in Nairobi River Urban Sediments Characterized by Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT–ICR–MS). Journal of the American Society for Mass Spectrometry. https://doi.org/10.1021/jasms.4c00229

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Abstract/Summary

Nairobi River sediments from locations adjacent to the Kawangware and Kiambio slums were analyzed via Fourier transform ion cyclotron resonance mass spectrometry with atmospheric pressure photoionization (APPI–FT–ICR–MS). The data from these ultrahigh resolution, untargeted measurements provided new insights into the impacts of local anthropogenic activity, which included likely benzo- and dibenzothiophene pollution with a suspected petrogenic origin, and prominent surfactant-like compositions. Other features in the data included highly abundant tetra-oxygenated compounds, and oxygenated nitrogen compounds with sphingolipid interpretations. Most notably, several hydrocarbon and oxygenated compound classes in the sediment data featured intensity patterns consistent with steroid molecular formulas, including those associated with sewage contamination investigatory work. In support of this interpretation, standards of cholesterol, β-sitosterol, stigmasterol, coprostanol, cholestanol, and 5α-sitostanol were analyzed via APPI, to explore steroid ionization behavior. Generally, these analytes produced radical molecular ions ([M]•+), and water-loss pseudo molecular ion species ([M–H2O]•+ and [M+H–H2O]+), among various other less intense contributions. The absence of pseudo molecular protonated species ([M+H]+) was notable for these compounds, because these are often assumed to form with APPI. The standard measurements demonstrated how steroids can create the observed intensity patterns in FT–ICR–MS data, and hence these patterns have the potential to indicate sewage contamination in the analysis of other complex environmental samples. The steroid interpretation for the Kawangware and Kiambio data was further verified by subjecting the steroid standard radical molecular ions to collision-induced dissociation and comparing the detected fragments to those for the corresponding isolated ions from a Kawangware sediment sample.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	https://doi.org/10.1021/jasms.4c00229
Additional Keywords:	IGRD
Date made live:	13 Sep 2024 11:44 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/538016

Item Type:

Publication - Article

Digital Object Identifier (DOI):

https://doi.org/10.1021/jasms.4c00229

Additional Keywords:

IGRD

Date made live:

13 Sep 2024 11:44 +0 (UTC)

URI:

https://nora.nerc.ac.uk/id/eprint/538016