Trace-Metal Chemistry of Galveston Bay - Water, Sediments and Biota

Galveston Bay is the second largest estuary in Texas. It receives major urban runoff from the Houston area, its major river drains the Dallas-Ft Worth Metroplex, and the area surrounding the Bay is intensely industrialized, with chemical and petroleum production being especially prominent. Consequently, there are serious concerns about the possible contamination of the Bay and previous studies have indicated toxic metals at elevated concentrations (e.g. NOAA, 1989a). We have conducted an extensive investigation of Galveston Bay trace metals, in which their distribution in the water column, oysters and sediments were determined. Results of the water column and oyster analyses indicate that metal levels in open areas of Galveston Bay are currently similar to those in more pristine bays elsewhere. Industrial metal inputs to the Bay have not led to greatly increased concentrations in water, sediments and biota. However, the sediment analyses indicated that such inputs may have been significant in the past. Total Cu, Zn, Pb, and Ag concentrations in the waters, determined by state-of-the-art clean techniques, are 1, 2.7, 0.3, and 0.006 mug liter-1, respectively, and are mostly regulated by the dynamics of sediment suspension and settling. This leads to a correlation of particulate trace metal concentration with the suspended particulate matter (SPM) concentrations, and trace metal enrichment in particles at low SPM concentrations. Forty-four percent of the individual sediment sampling sites exhibited an 'anomalous' concentration with respect to at least one of the metals studied and about half of these sites were directly associated with dredge spoils. The study also indicated that many of the metals are significantly converted to a coprecipitate with pyrite in the top 10 cm of sediment