An In Situ Laser-Induced Fluorescence System for Polycylic Aromatic Hydrocarbon-Contaminated Sediments

View the Report (Portable File Document ONLY) The Report [file size: 2,004kb] Appendix A: The total fluorescence–depth profiles collected during the course of this demonstration. [file size: 2,154kb] Appendix B: GC-MS Concentrations for all 43 Samples [file size: 64kb] Structures of Polycyclic Aromatic Hydrocarbons [file size 13kb] Appendix C: Plots of the Match Between Measured and Predicted Concentrations, along with the Associated Data Tables [file size: 117kb] Appendix D: Root Mean Square Error of Cross Validation (RMSECV) Completed Data Tables. [file size: 62kb] Appendix E: Depth profiles of all the stations. [file size: 34kb]

In the early 1970s the poor environmental health of the Great Lakes was recognized and both the United States and Canada banded together to form the International Joint Committee (IJC) in an effort to reverse a long trend of toxic pollutant discharge to the Great Lakes. The original Great Lakes Water Quality Agreement (GLWQA) between Canada and the Unites States was signed in 1972. Almost immediately, the IJC realized the importance of sediment-bound contamination. In 1975, the “International Working Group on the Abatement and Control of Pollution from Dredging Activities” was instituted. By 1978, a “Contaminated Sediment Task Force” was established to look at the assessment and remediation of contaminated sediments. In 1987, the United States demonstrated its support of the GLQWA by establishing, under the Clean Water Act, the “Assessment and Remediation of Contaminated Sediments” (ARCS) program. The ARCS program was specifically charged with assessing the nature and extent of sediment contamination and to demonstrate the effectiveness of selected remedial options at 5 different sites [¹]. The ARCS final report was issued in 1994 and immediately the IJC identified “remediation and management of sediments contaminated with persistent toxic substances” as one of its 1995-1997 program priorities [²].

This 20-year record of study has led to a consensus that contaminated sediments are a major cause of environmental problems in the Great Lakes. All of the original Areas of Concern (AOC) that were identified by the IJC as problem sites have contaminated sediment [²]. As such, contaminated sediments represent a universal obstacle to the environmental recovery of these areas. The GLWQA defines fourteen types of ecological impacts arising from contamination. Of these fourteen impacts, eleven are affected by the presence of sediment contamination. Table I lists these eleven impacts and the number of AOCs that display each type of impact.

One of the primary organic contaminants of concern in Great Lakes sediments are polycyclic aromatic hydrocarbons (PAHs). Table II lists three chemical characteristics of representative PAH compounds. For comparative purposes, the same characteristics are listed for the familiar compounds benzene and water. These characteristics define the environmental behavior of these compounds. Inspection of Table II reveals that PAH solubilities are very low and the hydrophobic sorptive capacity (Kow) is correspondingly high. This, coupled with low volatilities (Henry’s Law constant) and general chemical stability mean that PAHs are environmentally persistent compounds that are strongly held to solids, both suspended particles and bottom sediment. Relatively little transport via the dissolved phase is seen. Furthermore, the high partitioning to organic carbon (as reflected by high Kow) is the root cause behind the high rate of bioconcentration for these compounds and the ease with which they enter the food web. This illuminates the current dilemma facing Great Lakes managers. In spite of the fact that significant decreases in the discharge of these compounds to the Great Lakes has been achieved, a large pool exists in the bottom sediments and this pool is easily re-mobilized into the base of the food web by benthic organisms. Environmental managers cannot afford to ignore the existence of contaminated sediments.

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¹ Assessment and Remediation of Contaminated Sediment (ARCS) Program, Final Summary Report. EPA Report EPA-905-S94-001 (1994), 48 pp.

² Great Lakes Water Quality Board of the International Joint Commission. Position Statement on the Future of Great Lakes Remedial Action Plans (1996), 13 pp.

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