USGS_LOGO

In cooperation with the U.S. Air Force

Spatial Distribution and Trends in Trace Elements, Polycyclic Aromatic Hydrocarbons, Organochlorine Pesticides, and Polychlorinated Biphenyls in Lake Worth Sediment, Fort Worth, Texas

By Glenn R. Harwell, Peter C. Van Metre, Jennifer T. Wilson, and Barbara J. Mahler

U.S. GEOLOGICAL SURVEY
Water-Resources Investigations Report 03–4269


Document Accessibility: Adobe Systems Incorporated has information about PDFs and the visually impaired. This information provides tools to help make PDF files accessible. These tools convert Adobe PDF documents into HTML or ASCII text, which then can be read by a number of common screen-reading programs that synthesize text as audible speech. In addition, an accessible version of Acrobat Reader 5.0 for Windows (English only), which contains support for screen readers, is available. These tools and the accessible reader may be obtained free from Adobe at http://access.adobe.com/.

pdf (10.2 MB)


Contents

Abstract

Introduction

Purpose and Scope

Study Area

Acknowledgments

Methods and Preliminary Computations/Analyses

Collection of Bottom Sediment Samples

Analytical Methods

Age Dating and Mass Accumulation Rates

Normalization Techniques and Statistical Tests

Grain Size and Organic Carbon

Spatial Distribution and Historical Trends of Selected Hydrophobic Contaminants

Trace Elements

Regression Results

Spatial Distribution of Trace Elements

Historical Trends in Trace Elements

Polycyclic Aromatic Hydrocarbons

Spatial Distribution of PAHs

Historical Trends in PAHs

PAH Assemblage

Organochlorine Pesticides

Polychlorinated Biphenyls

Spatial Distribution of PCBs

Historical Trends in PCBs

Possible Sources of PCBs

Summary

References Cited

Figures

1. 
Map showing location of study area and approximate sampling locations in Lake Worth, Fort Worth, Texas, 2000–2001
2–9. 
Graphs showing:
 
2a–e. 
Cesium-137 profiles in gravity core samples from Lake Worth, Fort Worth, Texas, 2000–2001
 
3. 
Depth versus cesium-137 date in gravity core sample from background site upstream from IH–820 bridge in Lake Worth, Fort Worth, Texas, 2000–2001
 
4a–x. 
Sediment characteristics and selected major elements in gravity core samples from Lake Worth, Fort Worth, Texas, 2000–2001
 
5. 
Comparison of cadmium concentrations in lake sediment from selected areas of Lake Worth, Fort Worth, Texas, 2000–2001
 
6a–f. 
Regression analyses to describe spatial distribution of trace elements in sediment from Lake Worth, Fort Worth, Texas, 2000–2001
 
7a–g. 
Historical trends of trace elements in gravity core samples from Lake Worth, Fort Worth, Texas, 2000–2001
 
8. 
Comparison of total polycyclic aromatic hydrocarbon (PAH) and total combustion PAH concentrations in lake sediment from selected areas of Lake Worth, Fort Worth, Texas, 2000–2001
 
9a–i. 
Historical trends of total polycyclic aromatic hydrocarbon (PAH) and total combustion PAH concentrations, PAH source ratios, and organic carbon in gravity core samples from Lake Worth, Fort Worth, Texas, 2000–2001
 
10. 
Map showing spatial distribution of total polychlorinated biphenyls (PCBs) in surficial sediment samples from Lake Worth, Fort Worth, Texas, 2000–2001
 
11a–d. 
Graphs showing historical trends of polychlorinated biphenyls (PCBs) in gravity core samples from Lake Worth, Fort Worth, Texas, 2000–2001

Tables

1. 
Descriptive information for sediment sampling locations in Lake Worth, Fort Worth, Texas, 2000–2001
2. 
Mass accumulation rates computed from cesium-137 concentrations in gravity core sediment samples from Lake Worth, Fort Worth, Texas, 2000–2001
3. 
Concentrations of selected major and trace elements, grain size, and forms of carbon in sediment samples from Lake Worth, Fort Worth, Texas, 2000–2001
4. 
Kendall's tau correlation coefficients between trace elements and potential normalizing variables in sediments from Lake Worth, Fort Worth, Texas
5. 
Linear regression equations used to estimate background trace element concentrations and anthropogenic contributions in sediment from Lake Worth, Fort Worth, Texas
6. 
Concentrations of selected polycyclic aromatic hydrocarbons (PAHs) in sediment samples from Lake Worth, Fort Worth, Texas, 2000–2001
7. 
Concentrations of selected organochlorine pesticides and polychlorinated biphenyls (PCBs) in sediment samples from Lake Worth, Fort Worth, Texas, 2000–2001

Abstract

In spring 2000, the Texas Department of Health issued a fish consumption advisory for Lake Worth in Fort Worth, Texas, because of elevated concentrations of polychlorinated biphenyls (PCBs) in fish. In response to the advisory and in cooperation with the U.S. Air Force, the U.S. Geological Survey collected 21 surficial sediment samples and three gravity core sediment samples to assess the spatial distribution and historical trends of selected hydrophobic contaminants, including PCBs, and to determine, to the extent possible, sources of hydrophobic contaminants to Lake Worth. Compared to reference (background) concentrations in the upper lake, elevated PCB concentrations were detected in the surficial sediment samples collected in Woods Inlet, which receives surface runoff from Air Force facilities and urban areas. Gravity cores from Woods Inlet and from the main part of the lake near the dam indicate that the concentrations of PCBs were three to five times higher in the 1960s than in 2000. A regression method was used to normalize sediment concentrations of trace elements for natural variations and to distinguish natural and anthropogenic contributions to sediments. Concentrations of several trace elements—cadmium, chromium, copper, lead, and zinc—were elevated in sediments in Woods Inlet, along the shoreline of Air Force facilities, and in the main lake near the dam. Concentrations of these five trace elements have decreased since 1970. Polycyclic aromatic hydrocarbons also were elevated in the same areas of the lake. Concentrations of total polycyclic aromatic hydrocarbons, normalized with organic carbon, were mostly stable in the upper lake but steadily increased near the dam, except for small decreases since 1980. The Woods Inlet gravity core showed the largest increase of the three core sites beginning about 1940; total polycyclic aromatic hydrocarbon concentrations in post-1940 sediments from the core showed three apparent peaks about 1960, 1984, and 2000. The concentrations of organochlorine pesticides were low relative to consensus-based sediment-quality guidelines and either decreased or remained constant since 1970. The two likely sources of hydrophobic contaminants to the lake are urban areas around the lake and the drainage area of Meandering Road Creek that contributes runoff to Woods Inlet and includes Air Force facilities.




U.S. Department of the Interior, U.S. Geological Survey
Persistent URL: http://pubs.water.usgs.gov/wri034269
Page Contact Information: GS Pubs Web Contact
Last modified: Friday, September 16 2005, 04:23:49 PM
FirstGov button  Take Pride in America button