Temporal trends and identification of the sources of volatile organic compounds in coastal seawater

Abstract

Volatile Organic Compounds (VOCs) in the marine environment are produced by biogenic sources (marine macroalgae, phytoplankton, sediments, etc.) as well from anthropogenic sources. The temporal variation of such VOCs was studied together with their relationship to biological, meteorological and physico-chemical factors. Sixty four different VOCs were quantified including halogenated (<LoD to 906 ng L(-1)), non-methane hydrocarbons (NMHC) (<LoD to 1539 ng L(-1)), mono-aromatics (<LoD to 4232 ng L(-1)), oxygenated (<LoD to 1539 ng L(-1)) and sulfur containing compounds (<LoD to 160 ng L(-1)). The analyses were performed employing solid phase microextraction (SPME) coupled to gas chromatography/mass spectrometry (GC/MS) analysis. Pigments such as chlorophyll a correlated with halogenated compounds (e.g. chloroform and dichloromethane) and dimethylsulfide (DMS) was maximal during the spring bloom. Multivariate statistical analyses demonstrated seasonal changes in the VOC signature (more mono-aromatics and alkanes in the winter and halocarbons in the summer). Principal component analysis (PCA) demonstrated that physico-chemical and meteorological factors such as wind speed and water temperature can influence the detection of VOCs in surface waters as well their productions. Partial least squares (PLS) modelling highlighted the importance of the microalgae signature in spring while macroalgae and sediments dominated at other times. Short term variability in concentrations and fluxes was due to such factors as tidal state, wind speed and seawater temperature. The atmospheric concentrations were significantly less than any regulatory values although no measurements were made in eutrophic conditions.

Rapid identification of volatile compounds in fresh seaweed

“…These results are that the major volatile compounds found in seaweeds are hydrocarbons, terpenes, phenols, alcohols, aldehydes, ketones, esters, fatty acids and halogen or sulfur-containing compounds [4,22] and that marine macroalgae can produce a broad variety of volatile organic compounds [16]. They are also consistent with those found in other algae, among the volatile components observed in Palmaria palmata, the halogenated compounds were the most characteristic, followed by the aldehydes [8].…”

“…These methods present several disadvantages as use of expensive and hazardous organic solvents, lose analytes during extraction and high time consuming. Headspace-solid phase microextraction (HS-SPME) [16][17][18] are simple and solvent free methods, although presenting the risk of possible artefact generation and occasionally, poor reproducibility.…”

Sources of short-lived bromocarbons in the Iberian upwelling system

“…Class and Ballschmiter (1988) were one order of magnitude lower than in other productive coastal areas (e.g. Jones et al, 2009;Bravo-Linares and Mudge, 2009), contradicting the assumption that upwelling regions are pronounced "hot spots" for halocarbon formation (Quack et al, 2004). The relatively low bromocarbon concentrations measured in different upwelling areas question the importance of phytoplankton as a significant halocarbon source, in marked contrast with studies showing correlations between high concentrations of various halocarbons and the growth of microalgae (Krysell, 1991;Hughes et al, 2009;Klick and Abrahamsson, 1992;Moore and Tokarczyk, 1993).…”

Sources of short-lived bromocarbons in the Iberian upwelling system

“…Integrated values of CHBr 3 for the entire upwelling (30 pmol L −1 ) were one order of magnitude lower than for other productive coastal areas (e.g. Jones et al, 2009;Bravo-Linares and Mudge, 2009) and hence do not support the fact that upwelling regions are pronounced "hot spots" for halocarbon formation, as previously assumed (Quack et al, 2004). However, sources for the Iberian upwelling seem to be higher than those for the Mauritanian upwelling since CH 2 Br 2 and CHBr 3 values were significantly lower the off Mauritania coast.…”