Tracking riverborne sediment and contaminants in Commencement Bay, Washington, using geochemical signatures

Open-File Report 2017-1124
By: , and 

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Abstract

Large rivers carry terrestrial sediment, contaminants, and other materials to the coastal zone where they can affect marine biogeochemical cycles and ecosystems. This U.S. Geological Survey study combined river and marine sediment geochemistry and organic contaminant analyses to identify riverborne sediment and associated contaminants at shoreline sites in Commencement Bay, Puget Sound, Washington, that could be used by adult forage fish and other marine organisms. Geochemical signatures distinguished the fine fraction (<0.063 millimeter, mm) of Puyallup River sediment—which originates from Mount Rainier, a Cascade volcano—from glacial fine sediment in lowland bluffs that supply sediment to beaches. In combination with activities of beryllium-7 (7Be), a short-lived radionuclide, geochemical signatures showed that winter 2013–14 sediment runoff from the Puyallup River was transported to and deposited along the north shore of Commencement Bay, then mixed downward into the sediment column. The three Commencement Bay sites at which organic contaminants were measured in surface sediment did not have measurable 7Be activities in that layer, so their contaminant assemblages were attributed to sources from previous years. Concentrations of organic contaminants (the most common of which were polycyclic aromatic hydrocarbons, polychlorinated biphenyls, and fecal sterols) were higher in the <0.063-mm fraction compared to the <2-mm fraction, in winter compared to summer, in river suspended sediment compared to river bar and bank sediment, and in marine sediment compared to river sediment. The geochemical property barium/aluminum (Ba/Al) showed that the median percentage of Puyallup River derived fine surface sediment along the shoreline of Commencement Bay was 77 percent. This finding, in combination with higher concentrations of organic contaminants in marine rather than river sediment, indicates that riverborne sediment-bound contaminants are retained in shallow marine habitats of Commencement Bay. The retention of earlier inputs complicates efforts to identify recent inputs and sources. Understanding modern sources and fates of riverborne sediment and contaminants and their potential ecological impacts will therefore require a suite of targeted geochemical studies in such marine depositional environments.

Suggested Citation

Takesue, R.K., Conn, K.E., and Dinicola, R.S., 2017, Tracking riverborne sediment and contaminants in Commencement Bay, Washington, using geochemical signatures: U.S. Geological Survey Open-File Report 2017–1124, 31 p., https://doi.org/10.3133/ofr20171124.

ISSN: 2331-1258 (online)

Study Area

Table of Contents

  • Abstract
  • Introduction
  • Site Description
  • Methods
  • Results
  • Discussion
  • Summary
  • Acknowledgments
  • References Cited
  • Appendix 1
  • Appendix 2
  • Appendix 3
  • Appendix 4

Additional publication details

Publication type Report
Publication Subtype USGS Numbered Series
Title Tracking riverborne sediment and contaminants in Commencement Bay, Washington, using geochemical signatures
Series title Open-File Report
Series number 2017-1124
DOI 10.3133/ofr20171124
Year Published 2017
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) Pacific Coastal and Marine Science Center
Description vii, 31 p.
Country United States
State Washington
Other Geospatial Puyallup River
Online Only (Y/N) Y