Spatial and temporal variations in copper speciation in San Diego Bay |
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Authors: | Email author" target="_blank">A?C?BlakeEmail author D?B?Chadwick A?Zirino I?Rivera-Duarte |
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Institution: | 1.Space and Naval Warfare Systems Center,Marine Environmental Quality Branch,San Diego;2.Scripps Institution of Oceanography,La Jolla |
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Abstract: | Copper in estuaries has been an issue of concern for its toxicity to marine organisms. The ability to understand the processes
that control copper speciation is a key factor towards achieving an improved assessment of the ecological risk it poses in
the marine environment. Field measurements were made in August 2000, January 2001, May 2001, and September 2001 to provide
a comprehensive view of circulation and water quality both spatially and temporally for the entire San Diego Bay. Rapid, underway,
analysis of copper provided a unique, high-resolution view of total and labile copper species. The data show that total copper
concentrations in San Diego Bay have been close to or above water quality criteria, increasing gradually from the lowest values
in the mouth region (8 nM) to the innermost region (approximately 55 nM) with elevated concentrations existing in the Shelter
Island and Commercial Basins. This work indicates that free copper activity lies between 10−11 and 10−13, and declines from the entrance to the head of San Diego Bay, even though the total copper concentration increases, a likely
result of complexation with organic and particulate matter. Free copper measurements also show a seasonal dependence with
the highest concentrations occurring 2 wk after a winter rain event in January 2001, reaching close to or above toxic levels
in some locations. |
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