Poster Communications Year : 2017

Interfacial photochemistry of biogenic surfactants: estimating abiotic isoprene production on a global scale

Abstract

Life on Earth is a constant and versatile source for surface-active compounds in the ambient environment. Biogenic surfactants are, therefore, ubiquitously found on surfaces exposed to the open atmosphere, ranging from oceans, lakes, and rivers to cloud droplets and even aerosol particles. In the past, it was shown that irradiation of such surfactants present at air/water interfaces can lead to a significant production of unsaturated and functionalized VOCs, such as isoprene, possibly acting as precursors for organic aerosol formation and growth.[1,2,3] However, up to now, atmospheric chemistry models solely account for direct biological VOC emissions, typically resulting in large underestimations of ambient VOC levels and organic aerosol concentrations.[3,4] Thus, the implementation of abiotic photochemical VOC production might aid in closing current gaps and in reducing uncertainties of such models. In this work, we estimated isoprene fluxes over the oceans from abiotic interfacial photochemistry of biogenic surfactants. Following the approach of Wurl et al.,[5] we inferred surfactant enrichment in surface microlayers (SMLs) using satellite data for biological activity, water temperatures, and wind speeds. Monthly averages on global solar irradiation in the wavelength region of 280–420 nm were obtained from climatology data of the Tropospheric Ultraviolet and Visible (TUV) radiation model.[6] Isoprene production rates were taken from existing literature1 and from laboratory experiments, in which biofilms were used as source for surfactants. Our results indicate that especially in less biologically-active regions of the oceans isoprene production from abiotic photochemistry might have a substantial contribution to atmospheric VOC levels. Calculated global fluxes are in the range of current estimates for direct marine biological emissions, therefore, significantly increasing expected global isoprene levels in the marine boundary layer. Similar to the estimated isoprene fluxes, we further claim that abiotic photochemical production of other functionalized and unsaturated VOCs is neglected by current models, leading to an underestimation of their ambient concentrations and, thus, impacts on atmospheric chemistry and aerosol formation processes, especially in, but not limited to, the marine environment. References: 1 Ciuraru et al., Envrion. Sci. Technol., 2015, 49, 13199–13205. 2 Bernard et al., Envrion. Sci. Technol., 2016, 50, 8678–8686. 3 Brüggemann and Hayeck et al., Faraday Discuss., 2017, in press. 4 Arnold et al., Atmos. Chem. Phys., 2009, 9, 1253–1262. 5 Wurl et al., Biogeosciences, 2011, 8, 121–135. 6 Lee-Taylor and Madronich, NCAR Technical Note series, 2007, TN-474+STR.

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Dates and versions

hal-01529684 , version 1 (31-05-2017)

Identifiers

  • HAL Id : hal-01529684 , version 1

Cite

M. Bruggemann, N. Hayeck, C. George. Interfacial photochemistry of biogenic surfactants: estimating abiotic isoprene production on a global scale. Atmospheric Chemistry in the Anthropocene: Faraday Discussion, May 2017, York United Kingdom. ⟨hal-01529684⟩
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