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U.S. GEOLOGICAL SURVEY
Open-File Report 02-453

NEAR FIELD RECEIVING WATER MONITORING OF TRACE METALS IN CLAMS (MACOMA BALTHICA) AND SEDIMENTS  NEAR THE PALO ALTO WATER QUALITY CONTROL PLANT IN SOUTH SAN FRANCISCO BAY, CALIFORNIA: 1999-2001

Prepared in cooperation with the
CITY OF PALO ALTO, CALIFORNIA

By Carlos Primo C. David, Samuel N. Luoma, Cynthia L. Brown, Daniel J. Cain, Michelle I. Hornberger
and Irene R. Lavigne
 

ABSTRACT

This report presents trace element concentrations analyzed on samples of fine-grained sediments and clams (Macoma balthica) collected from a mudflat one kilometer south of the discharge of the Palo Alto Regional Water Quality Control Plant in South San Francisco Bay. This report serves as a continuation of the Near Field Receiving Water Monitoring Study which was started in 1994. The data for 1999-2001 are interpreted within that context. Generally, metal concentrations in both sediments and clam tissue samples have been within the range of values produced by seasonal variability. Copper and zinc, however, display a continued decrease, recording the lowest winter maxima concentrations in both sediment and tissue samples in 2001. Yearly average of bioavailable copper, zinc and silver concentrations in 1999-2001 are some of the lowest recorded since monitoring began in 1975. A slight increase in mercury in sediments and selenium in tissue in early 2001 are also observed. These enrichments are believed to be mainly caused by hydrogeologic processes affecting the area although only continued sampling will confirm whether anthropogenic sources influence the concentrations of these elements.
 

CONTENTS

Abstract
Introduction
Purpose
Study Site
Methods
Results and Discussion
References Cited
Appendix 1: Palo Alto Sediments Data
Appendix 2: Palo Alto Clams Data
 
 

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Download the Report (PDF, 1.6 MB)
 
Link to Appendix 1 & 2 (raw data)
 

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Send questions or comments about this report to Stacey Andrews (sandrews@usgs.gov) (650) 329-4468

For more information about USGS activities concerning Ecology and Contaminants in San Francisco Bay, visit the USGS Ecology and Contaminants Website.

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