This project will use the physical and chemical analysis of the Deepwater Horizon in-situ burning samples as a focal point for comparisons to the analyses of other oil and residue samples of relevance to the spill response. In particular, the pre- and post-burn sample results will be compared to: Samples of Macondo well source oil and the same source oil burned under controlled conditions at the NOAA/LSU chemistry support lab in Baton Rouge, LA; Samples of tarballs trawled from depth by deepwater shrimp nets in late 2010 and early 2011 north of the blowout location; Other samples of Deepwater Horizon oil collected at-sea, in marshes, and from beaches. The results will provide insights into the changes that occur to oil when it is burned and how the physical and chemical characteristics compare to other forms of oil encountered during a spill (e.g., emulsified surface oil, beach- and marsh-stranded oil, etc.). Analysis of burn residues and comparison to deep-water tarballs will help obtain an understanding of the longer-term fate of burned oil and identify potential impacts to pelagic and benthic environments and human activities like mid-water and bottom trawling. In addition to the physics and chemistry of the different oil types, the work will also will examine candidate biomarkers used to fingerprint oil and residues to source materials and recommend those that appear to have the greatest utility for identifying the origins of burned and/or weathered oil.