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In cooperation with the U.S. Air Force

Distribution and Sources of Polychlorinated Biphenyls in Woods Inlet, Lake Worth, Fort Worth, Texas, 2003

By Richard E. Besse, Peter C. Van Metre, and Jennifer T. Wilson

U.S. Geological Survey
Scientific Investigations Report 2005–5064


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Contents

Abstract

Introduction

Approach

Watershed Characteristics

Collection and Processing of Bottom Sediment Samples

Collection and Processing of Suspended Sediment Samples

Collection and Processing of Streambed Sediment Samples

Analytical Methods

Quality Control

Age-Dating Cores

Distribution and Sources of Polychlorinated Biphenyls in Woods Inlet

Polychlorinated Biphenyls in Bottom Sediment

Polychlorinated Biphenyls in Suspended and Streambed Sediment

Source Identification Using Polychlorinated Biphenyl Congener Assemblages

Summary

References

Appendixes

1.   Core-specific and analytical polychlorinated biphenyl data from core, surficial bottom, suspended, and streambed sediment samples, Woods Inlet and tributaries, Lake Worth, Fort Worth, Texas
  1. 1.  Porosity, cesium-137 (137Cs) activity, mass accumulation rate (MAR), and deposition dates for gravity core samples, Woods Inlet, Lake Worth, Fort Worth, Texas, 2003
  1.2.   Selected polychlorinated biphenyl (PCB) Aroclor and PCB congener concentrations in core, surficial bottom, suspended, and streambed sediment samples, Woods Inlet and tributaries, Lake Worth, Fort Worth, Texas, 2003
2.   Analytical data for major and trace elements, selected polycyclic aromatic hydrocarbons, and selected organochlorine pesticides from core, surficial bottom, suspended, and streambed sediment samples, Woods Inlet and tributaries, Lake Worth, Fort Worth, Texas
  2. 1.  Selected major and trace element concentrations in surficial bottom, suspended, and streambed sediment samples, Woods Inlet and tributaries, Lake Worth, Fort Worth, Texas, 2003
  2.2.   Selected polycyclic aromatic hydrocarbon concentrations in surficial bottom, suspended, and streambed sediment samples, Woods Inlet and tributaries, Lake Worth, Fort Worth, Texas, 2003
  2.3.   Selected organochlorine pesticide concentrations in surficial bottom, suspended, and streambed sediment samples, Woods Inlet and tributaries, Lake Worth, Fort Worth, Texas, 2003

Figures

1–3.   Maps showing:
  1.   Location of study area and polychlorinated biphenyl (PCB) concentrations in surficial bottom sediment, Lake Worth, Fort Worth, Texas, 2000–2001
  2.   Sediment sampling sites for this study in Woods Inlet and tributaries, Lake Worth, Fort Worth, Texas
  3.   Watersheds of tributary streams to Woods Inlet, Lake Worth, Fort Worth, Texas
4.   Photograph showing passive suspended sediment sampler, Gruggs Park Creek (a tributary to Woods Inlet), Lake Worth, Fort Worth, Texas, 2003
5.   Graphs showing cesium-137 profiles in gravity cores used for age-dating, Woods Inlet, Lake Worth, Texas, 2003
6.   Graphs showing detection frequency by polychlorinated biphenyl (PCB) congener and sample type, Woods Inlet, Lake Worth, Fort Worth, Texas, 2003
7.   Map showing total polychlorinated biphenyl (PCB) concentrations (sum of PCB congeners) in surficial bottom sediment, Woods Inlet, Fort Worth, Texas, 2003
8.   Graphs showing trends in total polychlorinated biphenyl (PCB) concentrations (sum of PCB congeners) in sediment cores relative to (a) sediment depth and (b) date of sediment deposition, Woods Inlet, Lake Worth, Fort Worth, Texas, 2003
9.   Map showing total polychlorinated biphenyl (PCB) concentrations (sum of PCB congeners) in suspended and streambed sediment from tributary streams to Woods Inlet, Lake Worth, Fort Worth, Texas, 2003
10.   Graphs showing selected polychlorinated biphenyl (PCB) congener assemblages normalized (divided) by total PCB (sum of PCB congeners) for surficial bottom sediment in areas of Woods inlet and suspended and streambed sediment in tributary streams to Woods Inlet, Lake Worth, Texas, 2003
11.   Map showing results of cluster analysis using selected polychlorinated biphenyl (PCB) congeners, Woods Inlet and tributaries, Lake Worth, Fort Worth, Texas, 2003

Tables

1.   Sampling site descriptive information, Woods Inlet and tributaries, Lake Worth, Fort Worth, Texas, 2003
2.   Polychlorinated biphenyl congeners analyzed for this report
3.   Summary of median relative percent differences (RPDs) of duplicate samples from this study and other coring and suspended sediment studies done by the U.S. Geological Survey (USGS) in Texas
4.   Root mean squared difference (RMSD), from smallest to largest, between normalized concentrations of 17 polychlorinated biphenyl congeners in suspended and streambed sediment samples in tributaries and mean of all surficial bottom sediment sample concentrations of those congeners in Woods Inlet, Lake Worth, Fort Worth, Texas, 2003

Abstract

Woods Inlet is a flooded stream channel on the southern shore of Lake Worth along the western boundary of Air Force Plant 4 in Fort Worth, Texas, where elevated polychlorinated biphenyl (PCB) concentrations in sediment were detected in a previous study. In response, the U.S. Geological Survey, in cooperation with the U.S. Air Force, conducted a study in 2003 to map the extent of elevated PCB concentrations in Woods Inlet and to identify possible sources (or more specifically, source areas) of PCBs in the watershed of Woods Inlet. Three gravity cores (penetration to pre-reservoir sediment at three sites) and 17 box cores (surficial bottom sediment samples) were collected in Woods Inlet. Suspended sediment in stormwater runoff and streambed sediment were sampled in tributaries to Woods Inlet following storms. Assemblages of PCB congeners in surficial inlet sediments and suspended and streambed sediments were analyzed to indicate sources of PCBs in the inlet sediments on the basis of chemical signatures of PCBs. Woods Inlet receives runoff primarily from three tributaries: (1) Gruggs Park Creek, (2) the small unnamed creek that drains a Texas National Guard maintenance facility, called TNG Creek for this report, and (3) Meandering Road Creek. Twenty-seven of 209 possible PCB congeners were analyzed. The sum of the congeners was used as a measure of total PCB. The spatial distribution of total PCB concentrations in the inlet indicates that most PCBs are originating in the Meandering Road Creek watershed. Peak total PCB concentrations in the three gravity cores occurred at depths corresponding to sediment deposition dates of about 1960 for two of the cores and about 1980 for the third core. The magnitudes of peak total PCB concentrations in the gravity cores followed a spatial distribution generally similar to that of surficial bottom sediment concentrations. Total PCB concentrations in suspended and streambed sediment varied greatly between sites and indicated a likely source of PCBs associated with a sampling site that receives runoff from Air Force Plant 4. Three approaches to the analyses of congener assemblages indicate that PCBs in surficial bottom sediment of Woods Inlet primarily enter Lake Worth from Meandering Road Creek and that runoff from Air Force Plant 4 is a source of the PCBs in Meandering Road Creek. Although current (2003) transport of PCBs from Air Force Plant 4 to the creek is occurring, large decreases in PCB concentrations with decreasing age in two cores indicate that PCB loading to the inlet has decreased greatly since the 1960s. Because runoff entering Meandering Road Creek from some parts of Air Force Plant 4 was not measured or sampled in this study, it cannot be said with certainty that the Air Force Plant 4 site sampled is the only source of PCBs to Meandering Road Creek.

 


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