Volume 200, 2017

Interfacial photochemistry of biogenic surfactants: a major source of abiotic volatile organic compounds

Abstract

Films of biogenic compounds exposed to the atmosphere are ubiquitously found on the surfaces of cloud droplets, aerosol particles, buildings, plants, soils and the ocean. These air/water interfaces host countless amphiphilic compounds concentrated there with respect to in bulk water, leading to a unique chemical environment. Here, photochemical processes at the air/water interface of biofilm-containing solutions were studied, demonstrating abiotic VOC production from authentic biogenic surfactants under ambient conditions. Using a combination of online-APCI-HRMS and PTR-ToF-MS, unsaturated and functionalized VOCs were identified and quantified, giving emission fluxes comparable to previous field and laboratory observations. Interestingly, VOC fluxes increased with the decay of microbial cells in the samples, indicating that cell lysis due to cell death was the main source for surfactants and VOC production. In particular, irradiation of samples containing solely biofilm cells without matrix components exhibited the strongest VOC production upon irradiation. In agreement with previous studies, LC-MS measurements of the liquid phase suggested the presence of fatty acids and known photosensitizers, possibly inducing the observed VOC production via peroxy radical chemistry. Up to now, such VOC emissions were directly accounted to high biological activity in surface waters. However, the results obtained suggest that abiotic photochemistry can lead to similar emissions into the atmosphere, especially in less biologically-active regions. Furthermore, chamber experiments suggest that oxidation (O3/OH radicals) of the photochemically-produced VOCs leads to aerosol formation and growth, possibly affecting atmospheric chemistry and climate-related processes, such as cloud formation or the Earth’s radiation budget.

Associated articles

Supplementary files

Article information

Article type
Paper
Submitted
17 Jan 2017
Accepted
01 Mar 2017
First published
01 Mar 2017

Faraday Discuss., 2017,200, 59-74

Interfacial photochemistry of biogenic surfactants: a major source of abiotic volatile organic compounds

M. Brüggemann, N. Hayeck, C. Bonnineau, S. Pesce, P. A. Alpert, S. Perrier, C. Zuth, T. Hoffmann, J. Chen and C. George, Faraday Discuss., 2017, 200, 59 DOI: 10.1039/C7FD00022G

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