Crude oil spillages are a major ecological threat, exposing aquatic wildlife to high concentrations of toxic organic pollutants. This study by Van Scoy et al. demonstrates the potential usefulness of semi-permeable membrane devises (SPMDs) in monitoring the exposure of aquatic organisms to dissolved hydrocarbons from crude oil, and in assessing the toxic effects that these compounds may exert.
Oil spills and their environmental impacts are frequently in the public and media spotlight. In order to adequately address this issue it is essential to establish the most effective way to limit exposure to the toxic compounds released. It is common for chemical dispersants to be used following spillages. These accelerate the natural dispersion of oil by reducing the interfacial surface tension. While these are considered to be an effective treatment method, the ecological impact of dispersed oil needs to be considered.
In this study SPMDs were used to extract the bioavailable fraction of dissolved hydrocarbons present in both ‘undispersed’ and ‘chemically dispersed’ crude oil. SPMDs mimic the action of biological membranes by allowing passive diffusion of aqueous compounds through the lipid membrane. Here, this technique was used to monitor levels of key polycyclic aromatic hydrocarbons (PAHs), a class of pollutants shown to display toxic and bioaccumulative properties in aquatic organisms.
The use of SPMDs is favourable compared to living models in bioavailability studies, providing a relatively quick, economical and efficient method and also avoids biotransformation of compounds during the experiment. In this study, ultra high purity triolein (C57H104O6) was used to extract 7 PAHs, monitoring accumulation over a 24hr exposure time to simulate the initial period after a spillage. Concentrations of 7 PAHs were measured using gas chromatography with mass spectrometry (GC-MS).
It was shown that, while the initial crude oil loading was 8 times higher for the undispersed oil (2 g L-1) compared to the dispersed oil (0.25 g L-1), accumulation of PAHs was greater for the dispersed oil. This was attributed to the micelles, formed upon dispersant application, weathering over time. This would suggest the use of chemical dispersants as a remediation measure may increase the risk of exposure of aquatic organisms to toxic hydrocarbons.
The study demonstrates the usefulness of SPMDs in measuring concentrations of dissolved organic pollutants present in crude oil. Data from this technique, in combination with metabolomic data, could be a valuable tool in better understanding the bioavailability of dissolved hydrocarbons in crude oil and the possible toxic effects this can have on aquatic wildlife. The paper would therefore be of interest to ecotoxicologists investigating aquatic organisms in both saltwater and freshwater environments.
Use of semipermeable membrane devices (SPMDs) to characterize dissolved hydrocarbon fractions of both dispersed and undispersed oil by April R. Van Scoy, Jennifer Voorhees, Brian S. Anderson, Bryn M. Philips and Ronald S. Tjeerdema.
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