The chemistry of Offatts Bayou, Texas: A seasonally highly sulfidic basin


1996 Sep


Cooper DC
Morse JW

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Offatts Bayou basin was created by use of this area as a borrow pit for landfill by the city of Galveston, Texas, in the first half of this century. Restricted exchange of water with the adjacent West Bay results in this basin changing, on a seasonal time scale, between oxic winter and highly sulfidic summer (greater than 500 mu M capital sigma H sub(2)S) bottom water conditions. It is, therefore, a 'natural laboratory' for the investigation of the behavior of toxic metals in an estuarine environment where redox conditions undergo major variations. Here we report the first study of the chemistry of Offatts Bayou's waters and sediment-associated trace metals. The high concentrations of dissolved sulfide in bottom water during summer cause a loss of macrofauna from most of the water deeper than about 4 m and the bottom of the basin. The potential exists for major mortality of organisms living in the oxic surface waters if rapid mixing of waters were to occur during the summer. Reactions of toxic metals with sulfides are probably the dominant influence on their potential bioavailability in this type of environment, as evidenced by large seasonal changes in concentrations of sedimentary sulfide minerals and associated trace metals. The trace metals As, Cu, and Hg are dominantly found in the pyrite phase (greater than 75% pyritization), Ag and Mn are moderately pyritized (40% to 60%), and Zn is not strongly associated with pyrite (less than 20% pyritization)




ASW,USA,Texas,Galveston Bay,Offatts Bayou, basins, bayous, Behavior, Brackishwater pollution, Coastal lagoons, Dissolved, estuarine environment, macrofauna, Metals, mineral, Mortality, oxidation-reduction potential, P 1000 MARINE POLLUTION, pyrite, Q5 01503 Characteristics,behavior and fate, seasonal variations, sediment concentration, Sediment pollution, speciation, sulfides, sulphides, Surface water, SW 0890 Estuaries, Texas, Trace metals, Trace-metal, USA, USA,Texas,Galveston,Offatts Bayou, USA,Texas,Offatts Bayou, water, Water analysis, winter