Resolving the Unresolved Complex Mixture in Petroleum Residues in Environmental Matrices

EPA Grant Number: R830393
Title: Resolving the Unresolved Complex Mixture in Petroleum Residues in Environmental Matrices
Investigators: Reddy, Christopher M.
Institution: Woods Hole Oceanographic Institution
EPA Project Officer: Carleton, James N
Project Period: September 1, 2002 through August 31, 2004
Project Amount: $224,955
RFA: Futures Research in Natural Sciences (2001) RFA Text |  Recipients Lists
Research Category: Ecological Indicators/Assessment/Restoration , Land and Waste Management , Hazardous Waste/Remediation


The unresolved complex mixture (UCM) of petroleum hydrocarbons is the most abundant, ubiquitous, and understudied class of organic contaminants in estuarine and coastal sediments. The term UCM is derived from traditional gas chromatography and refers to a hump of unresolved and, hence, unidentified hydrocarbons in gas chromatograms. Historically, UCM has been considered harmless but more recent studies suggest otherwise. Here, we plan to apply a novel and powerful analytical technique called comprehensive two dimensional gas chromatography (GCxGC) to provide a more detailed understanding of the molecular composition of UCM in order to better understand its source, transport, fate, and toxicity in the environment.


Preliminary investigations of GCxGC have shown that it is capable of resolving most of the components of UCM but additional experiments are necessary, especially pertaining to the selection of capillary columns. Hence, we will first develop and optimize GCxGC and GCxGC/MS methods for UCM component separation and identification. We then will determine the chemical class distributions (alkanes, branched alkanes, cycloalkanes, monoaromatics, polyaromatics, sulfur-containing aromatics) present in sediment samples obtained from different sources and compare these data to different neat and weathered petroleum products. These results will allow us to identify and apportion sources of UCM. Furthermore, we will assess the potential toxicological harm of UCM in different samples by identifying the most toxic components. In summary, the proposed research will provide detailed chemical analyses of UCM in aquatic sediments in order to assess its biogeochemistry.

Expected Results:

We anticipate that GCxGC will provide the necessary gas chromatographic resolution for analyzing UCM, which was previously unattainable. This novel study will: (i) allow for the first systematic investigation of the composition of UCM, (ii) deliver a more detailed means to source apportioning UCM, (iii) allow for a refined assessment of the toxic components of UCM, and (iv) offer a more accurate means of correlating laboratory and field studies on abiotic weathering of UCM. Overall, this project will lead to a further understanding of the sources and processes that deliver and control this important class of compounds. This project will also pave the way for more highly refined studies on the microbial degradation of UCM, which will be very beneficial for identifying or confirming natural attenuation. Last, we predict that, like the transition from packed to capillary GC columns or the advent of mass spectrometer detectors, GCxGC will be considered one of the major breakthroughs in analytical environmental chemistry and will be the tool of the future and a fixture in every laboratory.

Publications and Presentations:

Publications have been submitted on this project: View all 23 publications for this project

Journal Articles:

Journal Articles have been submitted on this project: View all 4 journal articles for this project

Supplemental Keywords:

sediment, environmental chemistry, analytical, and chemicals., RFA, Scientific Discipline, INTERNATIONAL COOPERATION, Waste, Water, Ecosystem Protection/Environmental Exposure & Risk, Contaminated Sediments, Environmental Chemistry, chemical mixtures, Fate & Transport, Hazardous Waste, Ecology and Ecosystems, Hazardous, biogeochemical partitioning, complex mixtures, fate, fate and transport, fate and transport , biodegradation, contaminated sediment, chemical contaminants, chemical transport, hazardous organic substances, environmental transport and fate, chemical kinetics, hydrocarbons, hazardous chemicals, molecular biology, unresolved complex mixture, contaminated soils, analytical models

Progress and Final Reports:

  • 2003 Progress Report
  • Final Report