Abstract:

X-ray techniques to measure the heavy metal tracers in oil, vanadium and also nickel. This research project directly addresses (1) the fate and transport of oil and dispersants (2) the biological and ecological impacts of oil and dispersants and (3) spill remediation and recovery by providing an elementally resolved study of the chemistry of the oil as it progresses from the riser to the shore. By understanding the details of the composition of the various compounds within the oil and dispersants, including the elemental valence states taken by the metals within these compounds, we will be able to better understand the solubility, toxicity and bioavailability, and thereby the impact on the Gulf Coast. Spatially-resolved studies of these materials and uptake within the flora and fauna of the region will further our understanding of the impact on the Gulf Coast. Crude oil contains several heavy metals such as vanadium, nickel, chromium, cadmium, and lead with vanadium and nickel usually in highest concentrations. About half the vanadium in crude oil is present as porphyrins (ring-like structures) with concentrations as high as 1600 parts per million (ppm). Toxicological studies have suggested that vanadium is embryo-toxic to ducks. The nickel concentration is generally less than that of vanadium and even though more than half of these metals are not associated with porphyrins the local structure of the metals is very similar. The porphyrins usually do not decompose below 400? to 500?C when heated. The techniques that were used in this study involved the use of synchrotron light produced at the J. Bennett Johnston, Sr., Center for Advanced Microstructures and Devices (CAMD), Louisiana State University, Baton Rouge. This electron storage ring produces an intense, tunable spectrum from the infrared to X-rays providing analytical techniques that cannot be performed elsewhere. Many of the techniques are X-ray based, they require little or no sample preparation, and are non-destructive. In addition, measurements on the crude oil are made on the whole sample without any separation into individual fractions. All fractions are also equally amenable to detection. The X-ray techniques used were X-ray absorption spectroscopy which provides information about speciation, that is, how an element is present rather than total concentration; X-ray diffractometry which identifies the phases present; small and wide angle X-ray scattering which determines structures ranging from nanometers to hundreds of nanometers in dimension; and X-ray tomography, a non-invasive technique for studying three-dimensional morphology of a material at a few micrometer resolution. Infrared spectro-microscopy was also used.