USGS
cover of ofr 01-089

Benthic Flux of Dissolved Nickel into the Water Column of South San Francisco Bay

Open File Report 01-89

By Brent R.Topping, James S. Kuwabara, Francis Parchaso, Stephen W. Hager, Andrew J. Arnsberg, Fred Murphy

 


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CONTENTS

Executive Summary

Background

Results and Discussion

Study Design and Methods

Bibliography

Acknowledgements

Appendix 1: Comments on the Report Structure

Appendix 2: List of Figures

Appendix 3: List of Tables

 

Abstract

Field and laboratory studies were conducted between April, 1998 and May, 1999 to provide the first direct measurements of the benthic flux of dissolved (0.2-micron filtered) nickel between the bottom sediment and water column at three sites in the southern component of San Francisco Bay (South Bay), California. Dissolved nickel and predominant ligands (represented by dissolved organic carbon, and sulfides) were the solutes of primary interest, although a variety of ancillary measurements were also performed to provide a framework for interpretation.

Results described herein integrate information needs identified by the State Water Resources Control Board and local stakeholders with fundamental research associated with the U.S. Geological Survey Toxic Substances Hydrology Program. Dissolved-Ni concentrations in the bottom water over the three sampling dates ranged from 34 to 43 nanomoles per liter. Dissolved-macronutrient concentrations in the bottom water were consistently higher (frequently by orders of magnitude) than surface-water determinations reported for similar times and locations (Regional Monitoring Program, 2001). This is consistent with measured positive benthic fluxes for the macronutrients.

Benthic-flux estimates for dissolved nickel from core-incubations, when areally averaged over the South Bay, were significant (that is, of equivalent or greater order of magnitude) relative to previously reported freshwater point and non-point sources. This observation is consistent with previous determinations for other metals, and with the potential remobilization of sediment-associated metals that have been ubiquitously distributed in the South Bay. Similar to dissolved-nickel results, benthic flux of macronutrients was also consistently significant relative to surface-water inputs. These results add to a growing body of knowledge that strongly suggests a need to consider contaminant transport across the sediment-water interface when establishing future management strategies for the watershed.

 


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POINTS OF CONTACT AND ADDITIONAL INFORMATION

Brent R. Topping
James S. Kuwabara
U.S. Geological Survey
345 Middlefield Road, MS 439
Menlo Park, CA 94025
Copies of this report may be purchased from:
U.S. Geological Survey
Information Services
Box 25286 Federal Center
Denver, CO 80225
Or call: 1-888-ASK-USGS



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