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| Texas Water Science Center |
By Peter C. Van Metre, Jennifer T. Wilson, and Briant A. Kimball
U.S. Geological Survey
Scientific Investigations Report 2006–5301
In cooperation with the U.S. Environmental Protection Agency
Devils Swamp Lake near Baton Rouge, Louisiana, created in 1973 by dredging in Devils Swamp along the Mississippi River, is contaminated with polychlorinated biphenyls (PCBs) from historical industrial discharges. This study involved the investigation of the occurrence, distribution, and sources of PCBs in the lake, including the possible historical contribution of PCBs from a hazardous-chemical disposal facility by way of a wastewater drainage ditch that was used from 1971 to 1993. Six bed sediment cores from the lake and three bed sediment grab samples from the drainage ditch were collected; 61 subsamples from selected intervals in five of the six cores and the three grab samples from the ditch were analyzed for PCBs using an immunoassay screening method. Sixteen of the core subsamples and one ditch sample were analyzed for organochlorine pesticides, PCBs, polycyclic aromatic hydrocarbons (PAHs) (15 samples), and major and trace elements. PCB congener profiles and a factor analysis of congener composition indicate that PCBs in sediment from the drainage ditch and in lake sediment deposited near the canal since the mid-1980s are similar, which indicates the disposal facility, by way of the wastewater drainage ditch, is the source of the PCBs. Sediment from several hundred meters down the lake to the west, near where Bayou Baton Rouge enters the lake, had a different PCB composition and in a sample deposited in the early 1980s, a much higher concentration, indicating a second source of PCBs in the watershed of Bayou Baton Rouge. Large differences in PAHs and metals between sediment near the ditch and sediment near Bayou Baton Rouge support this conclusion. The identity of the Bayou Baton Rouge source(s) cannot be established using available data. The short duration and relatively high concentrations of PCBs from the bayou source indicate either a spill or a flood-related release—there was a large flood on the Mississippi River in 1983. Older (deeper) samples from cores near the drainage ditch (dated as deposited before the mid-1980s) had PCB compositions that indicate a mixture of sources (Bayou Baton Rouge and the drainage ditch). Elevated PCB concentrations in sediment from the drainage ditch and cores from near the mouth of the ditch in recent (post-2000) samples indicate that some PCB inputs from the ditch might still be occurring.
Abstract
Introduction
Methods
Core Collection
Chemical Analysis
Quality Assurance
Sources of Polychlorinated Biphenyls
Concentrations and Trends
Polychlorinated Biphenyl Congener Patterns
Multivariate Analysis of Polychlorinated Biphenyls
Metals and Polycyclic Aromatic Hydrocarbons as Source Indicators
Historical Data Regarding a Second Source
Summary
Selected References
Appendixes
1. Analytical Results for Selected Chlorinated Hydrocarbon Compounds
2. Analytical Results for Polycyclic Aromatic Hydrocarbons
3. Analytical Results for Major and Trace Elements
| 1. | Aerial images of Devils Swamp Lake near Baton Rouge, Louisiana, showing (A) lake in relation to surrounding features and (B) approximate locations of sites sampled October 5, 2004 | |
| 2. | Photograph showing core DSL.5 collected from Devils Swamp Lake, Louisiana, October 5, 2004, split lengthwise for description and subsampling | |
| 3–7. | Graphs showing: | |
| 3. | Concentrations of polychlorinated biphenyls (PCBs) in Devils Swamp Lake, Louisiana, cores—comparison of immunoassay screening results and laboratory analyses using gas chromatography with electron capture detection (GC–ECD) | |
| 4. | Polychlorinated biphenyl (PCB) congener patterns in various groups of bed sediment samples collected in and near Devils Swamp Lake, Louisiana | |
| 5. | Temporal shifts in relative concentrations (to total) of polychlorinated biphenyl (PCB) Aroclors in Devils Swamp Lake, Louisiana, bed sediments | |
| 6. | Factor loadings determined using proportions of polychlorinated biphenyl (PCB) congeners in samples from Devils Swamp Lake, Louisiana | |
| 7. | Temporal trends in concentrations of selected metals, the sum of polychlorinated biphenyl congeners (SPCBC), the sum of selected polycyclic aromatic hydrocarbons (SPAHSQG), and the PAH source ratio (PAH 2+3/comb ratio) in cores DSL.2, DSL.4, and DSL.5, Devils Swamp Lake, Louisiana | |
| 8. | Aerial images of Devils Swamp Lake, Louisiana, showing concentrations of (A) the sum of polychlorinated biphenyl Aroclors (SPCBC) and (B) the sum of 13 polycyclic aromatic hydrocarbon compounds used for the probable effects concentration (SPAHSQG) in U.S. Geological Survey (USGS) core samples dated as mid-1980s and in grab samples collected in 1992 by PRC Environmental Management, Inc. | |
| 1. | Compound type, common name, abbreviation, and registry number for chlorinated hydrocarbon compounds |
| 2. | Scores for factors representing three end-members determined using EQ-mode factor analysis of polychlorinated biphenyl (PCB) congener concentrations in sediment from Devils Swamp Lake, Louisiana |
| 3. | Compositional loadings of three end-members based on EQ-mode factor analysis for sediment samples from Devils Swamp Lake, Louisiana |
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U.S. Department of the Interior | U.S. Geological Survey
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