Unresolved complex mixture
In attempting to determine "the processes that regulate the fate of petroleum following release to the environment,” geochemist Christopher M. Reddy of Woods Hole Oceanographic Institution invented an application of comprehensive two-dimensional gas chromatography (GCxGC) that resolves UMPs[2] and that he patented.
[5] These residues form the majority of the unresolved complex mixture (UCM) resulting from the breakdown of crude oils that GC had previously been unable to resolve but which Reddy’s novel GCxGC application has made accessible, enabling determination of “the underlying processes controlling petroleum fate” as it degrades in a marine environment.
[2] The technique Reddy invented is now widely applied in the characterization of petroleum in environmental samples as well as in analyses of other complex organic mixtures, and, because of it, GCxGC has transitioned from “a niche qualitative analysis tool to a robust quantitative technique.” [2] For this innovative work, Reddy was awarded the Clair C. Patterson Award in 2014 by the Geochemical Society for "an innovative breakthrough in environmental geochemistry of fundamental significance within the last decade, particularly in service to society.
To be viewed as innovative, the work must show a high degree of creativity and/or be a fundamental departure from usual practice while contributing significantly to understanding in environmental geochemistry.
Gas chromatograms of mature oils have prominent n-alkane peaks which distract attention from the underlying unresolved complex mixture (UCM) of hydrocarbons often referred to as the ‘hump’.
[25] In a study of the potential for UCM-dominated oil to be further degraded, it was concluded that even using bacteria specifically adapted for complex UCM hydrocarbons in conjunction with nutrient enrichment, biodegradation rates would still be relatively slow.
[30] Most research into petrochemical hydrocarbons using GC×GC has utilised flame ionisation detection (FID) but mass spectrometry (MS) is necessary to obtain the structural information necessary to identify unknown compounds.
[11] Laboratory toxicity tests using both commercially available and specially synthesised compounds revealed that such branched alkylated structures were capable of producing the observed poor health of the mussels.
[11][14] The reversible effects observed in mussels following exposure to the UCM hydrocarbons identified to date are consistent with non-specific narcosis (also known as baseline) mode of action of toxicity.
[15] Within marsh sediments still contaminated with high concentrations of UCM hydrocarbons from the Florida barge oil spill in 1969 (see above,) the behaviour and feeding of fiddler crabs (Uca pugnax) was reported to be affected.
