Several different halogenated organic compounds (HOCs) found in animal tissues have been suggested to have either industrial or natural sources, yet there is no conclusive evidence supporting either source. As a means to help identify the sources of these compounds in the ocean, researchers at the Woods Hole Oceanographic Institution will be supported in this project to continue development of a multi-isotopic tracer approach employing molecular-level radiocarbon (14C) and stable nitrogen isotope analysis. Radiocarbon is an ideal tracer for establishing the origin of these compounds since all recent natural products should be pre-labeled with at least some 14C. In contrast, industrial compounds, which are almost exclusively synthesized from petrochemical feedstock, contain no measurable 14C. Initial studies from previous support have shown that this is a viable approach. Many of these HOCs contain two atoms in each molecule. If the 14C data indicates a natural source, molecular-level stable nitrogen analyses will used to determine the trophic level of biosynthesis. Access to samples is now available and analytical methods have been well developed. Numerous halogenated bipyrroles will be the targeted compounds. The latter will be isolated from marine mammals found stranded along the Pacific and Atlantic coasts of North America.
In terms of broader impacts, it is clear that establishing the origin of these HOCs is of socioeconomic importance. For example, if some of these compounds indeed turn out to derive from anthropogenic activity, careful consideration would need to be given to their source and mode of production and to whether their emissions can or should be controlled. The PI is active in advising postdoctoral, graduate and undergraduate summer students. The proposed research program will form the foundation for two Ph.D. dissertations. Findings from this study will also be incorporated into the curriculum of the MIT-WHOI Joint Program in Oceanography.
