Scientific Investigations Report 2006-5262
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AbstractConcentrations, loads, and yields of particle-associated (hydrophobic) contaminants (PACs) in urban runoff in creeks in Austin, Texas, were characterized using an innovative approach: large-volume suspended-sediment sampling. This approach isolates suspended sediment from the water column in quantities sufficient for direct chemical analysis of PACs. During 1999–2004, samples were collected after selected rain events from each of five stream sites and Barton Springs for a study by the U.S. Geological Survey, in cooperation with the City of Austin. Sediment isolated from composited samples was analyzed for major elements, metals, organochlorine compounds, and polycyclic aromatic hydrocarbons (PAHs). In addition, at the Shoal Creek and Boggy Creek sites, individual samples for some events were analyzed to investigate within-event variation in sediment chemistry. Organochlorine compounds detected in suspended sediment included chlordane, dieldrin, DDD, DDE, DDT, and polychlorinated biphenyls (PCBs). Concentrations of PACs varied widely both within and between sites, with higher concentrations at the more urban sites and multiple nondetections at the least-urban sites. Within-site variation for metals and PAHs was smaller than between-site variation, and concentrations and yields of these and the organochlorine compounds correlated positively to the percentage of urban land use in the watershed. Loads of most PACs tested correlated significantly with suspended-sediment loads. Concentrations of most PACs correlated strongly with three measures of urban land use. Variation in suspended-sediment chemistry during runoff events was investigated at the Shoal and Boggy Creek sites. Five of the eight metals analyzed, dieldrin, chlordane, PCBs, and PAHs were detected at the highest concentrations in the first sample collected at the Shoal Creek site, a first-flush effect, but not at the Boggy Creek site. Temporal patterns in concentrations of DDT and its breakdown products varied from one event to the next. In spite of the first-flush effect in concentrations at the Shoal Creek site, most of the contaminant load was transported at peak discharge, when suspended-sediment concentration and load are maximum. |
Mahler, B.J., Van Metre, P.C., Wilson, J.T., Guilfoyle, A.L., and Sunvison, M.W., 2006, Concentrations, loads, and yields of particle-associated contaminants in urban creeks, Austin, Texas, 1999–2004: U.S. Geological Survey Scientific Investigations Report 2006–5262, 107 p.
Abstract
Introduction
Purpose and Scope
Site Selection
Acknowledgments
Methods of Sampling and Analysis
Approach
Sample Collection, Compositing, and Processing
Rainfall Data
Analytical Methods
Quality Assurance of Chemical Data
Laboratory Data
Routine Field Data
Methods-Development Test Data
Sample Concentrations, Loads, and Yields
Sample Concentrations
Major Elements
Trace Elements (Metals)
Organochlorine Compounds
Polycyclic Aromatic Hydrocarbons
Variation in Concentrations
Trends in Concentration
Loads and Yields
Explanatory Variables
Explanatory Variables and Concentrations
Relations Between Sediment Loads and Particle-Associated Contaminant Loads
Relation Between Contaminant Yields and Land Use
Evaluation of Relative Contamination
Contaminant Concentrations in Context of Local and Nationwide Data
The Barton Sites—Barton Creek and Barton Springs
Within-Event Variation in Concentrations and Loads—Case Studies for Shoal and Boggy Creeks
Temporal Patterns in Concentrations Over the Duration of the Storm
Temporal Patterns in Loads
Temporal Patterns in Contaminant Partitioning—Comparison of Particulate and Dissolved Metals Concentrations
Conclusions
References Cited
Appendix 1—Evaluation of the Large-Volume Suspended-Sediment Approach in Relation to Traditional Sampling Approaches
Appendix 2—Total Concentrations of Metals in Whole Water and Comparison to Concentrations in Large-Volume Suspended-Sediment Samples
Appendix 3—Concentrations Associated With Suspended Sediment in Composite Rain Event Samples
Appendix 4—Loads Associated With Suspended Sediment
Appendix 5—Yields Associated With Suspended Sediment
Appendix 6—Concentrations Associated With Suspended Sediment in Discrete Rain Event Samples at Shoal and Boggy Creeks
| For additional information contact: Director, Texas Water Science Center U.S. Geological Survey 8027 Exchange Drive Austin, Texas 78754-4733 World Wide Web: http://tx.usgs.gov/ |
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Last modified: Thursday, 01-Dec-2016 19:38:15 EST
