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Emission rates of C8-C15 VOCs from seaweed and sand in the inter-tidal zone at Mace Head, Ireland.

Research output: Contribution to Journal/MagazineJournal articlepeer-review

Published
<mark>Journal publication date</mark>11/2002
<mark>Journal</mark>Atmospheric Environment
Issue number34
Volume36
Number of pages11
Pages (from-to)5311-5321
Publication StatusPublished
<mark>Original language</mark>English

Abstract

Emission fluxes for a range of C8–C15 volatile organic compounds (VOCs) were determined from the seaweed Fucus spiralis (spiral wrack) and an adjacent sand surface during low tide on the coastline of Mace Head, Ireland. These two surface types, assessed using dynamic flux chamber systems, are typical of the Mace Head inter-tidal zone. A range of n-alkanes and oxygenates were routinely identified in the measurement of chamber air. Examination of the odd/even n-alkane ratios and use of the carbon preference index (CPI) suggested a biogenic source for these compounds (CPIs >2 in for all samples). Fluxes of n-pentadecane, the most predominant n-alkane, ranged from 0.2 to 5.1 μg m−2 h−1 (0.9–24 nmol m−2 h−1), while oxygenates such as nonanal and decanal had fluxes ranging from <0.1 to 4.4 μg m−2 h−1 (<0.1–31 nmol m−2 h−1) and <0.1 to 4.6 μg m−2 h−1 (<0.1–30 nmol m−2 h−1), respectively. Seaweed emission rates for n-pentadecane were correlated with photosynthetically active radiation (PAR) (rs=0.94) while emissions from sand showed correlation with temperature (rs=0.85). This suggests a possible biochemical route controlling the release of n-pentadecane from spiral wrack, and temperature-driven volatilisation from sand. Volatilisation from residual seawater trapped in the sand may explain the comparable flux of both n-alkanes and oxygenates from this surface. Unlike the n-alkanes, oxygenate fluxes from sand correlate with PAR, suggesting a photodependent production from organic carbon residues present in seawater. Comparison with previous flux estimates from coastal seawater indicates that the two source types (Fucus spiralis and bare sand) are significant but not dominant sources of these VOCs.