Heavy Metal Geochemistry of Sediments and Oysters from Galveston Bay, Texas

Date

2021-05

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Abstract

Galveston Bay is an anthropogenic estuary, where industrial runoff, wastewater, and shipping vessel oil enter the bay via incoming freshwaters and atmospheric deposition. Lead isotope ratios and heavy metal concentrations of Galveston sediments and oysters are presented here to explore the sources, fluxes, and toxicity of heavy metals in this estuary. Lead isotopes are established as tracers of environmental pollution that allow the Pb sources within a sample to be identified. The sediments and oysters display similar spatial metal variation trends with elevated metal contents in eastern Galveston Bay. Eastern bay sediments have higher metal concentrations than western bay sediments due to the flocculation of dissolved metals where the Trinity River, the largest freshwater inflow, enters Galveston Bay. Spatially, oyster metal concentrations are most likely influenced by proximity to anthropogenic metal inputs and nearby sediment metal contents. Temporal variation in sediment and oyster metal contents is significantly and positively correlated with riverine input to the bay. Sediment core data does not demonstrate a decrease in sediment metal concentrations over the past 30 years, rather Fe, Pb Ni, Cd and Hg levels are stable, and Cu and Zn levels increase. Galveston Bay sediments may be toxic for As, Cd, Cr, Cu, Hg, Ni, Sb, and Zn, while oysters are potentially toxic for Cd, Pb and Zn. Nickel and Cr in the bay likely originate from natural sources, while anthropogenic sources supply As, Cd, Hg, Ni, Pb, Sb, Zn and maybe Cu. Lead isotope modeling confirms the presence of anthropogenic Pb, and by extension other metals, in Galveston Bay sediments and oysters. An estimated 75% of the Pb in Galveston Bay bulk sediments is natural and 25% is anthropogenic. Oyster sample Pb isotope modeling results approximate 80% of the Pb in oyster tissues naturally derived and about 20% is anthropogenic. The findings presented here demonstrate that Galveston Bay sediment and oyster metal concentrations are shaped by riverine input and flocculation dynamics. However, a substantial portion of the metals present in Galveston Bay sediments and oysters are attributed to anthropogenic activity, which highlights the prevalent human influence on this natural system.

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Keywords

marine biogeochemistry, lead isotope tracing, marine pollution, heavy metal contaminants

Citation

Portions of this document appear in: Lopez, Amanda M., Alan D. Brandon, Frank C. Ramos, Jessica N. Fitzsimmons, Timothy M. Dellapenna, and Hannah M. Adams. "Lead geochemistry of sediments in Galveston Bay, Texas." Environmental Advances 4 (2021): 100057; and in: Lopez, Amanda M., Jessica N. Fitzsimmons, Hannah M. Adams, Timothy M. Dellapenna, and Alan D. Brandon. "A time-series of heavy metal geochemistry in sediments of Galveston Bay estuary, Texas, 2017-2019." Science of The Total Environment 806 (2022): 150446.