Application of organic petrology and chemistry in forensic studies of solid waste sites

Solid waste disposal sites offer new opportunities for the application of organic petrology, organic geochemistry, palynology, and other tools developed in the studies of coals and organic-rich rocks. The disposal sites can contain complex mixtures of materials including organic-rich rocks, inorganic rocks, recent sediments, vegetation growing on the surface of the site, tars and other hydrocarbons, coke, coal combustion byproducts, slags, and metals from primary metal manufacturing. In the United States, many of these waste deposits would be among the Environmental Protection Agency's Superfund Sites or corresponding State programs. Most conventional site investigations and remediations rely on standardized engineering and chemistry methods but allow flexibility for non-standard forensic testing methods when contamination sources are difficult to ascertain or distinguish from many candidate sources or regional background. For example, the origin of sites with hydrocarbon impacts are typically characterized with methods that measure bulk hydrocarbons or a dozen individual chemicals that work well in remote areas without historical contamination; however, complex urban soil and sediment are potentially impacted by numerous sources, anthropogenic runoff, and fill that contain multiple hydrocarbon sources composed of thousands of individual chemicals. This paper demonstrates the utility of petrological and chemical techniques for waste characterization and delineation at complicated sites with numerous potential historical impacts. Presently, these techniques have been used at a limited number of hazardous wastes sites with highly contested boundaries and source attributions. However, this paper provides numerous microscopic images and chemical fingerprints that serve as references to help site investigators more accurately identify individual releases and remediate contaminated sites more broadly and efficiently in the future. The petrology and chemistry techniques used in these studies are reviewed with application notes concerning site-specific customization. In many cases, the traditional applications of coal and coke petrology and of organic geochemistry, among other tools, are essential in understanding the origin of the waste and its path to remediation.