Evaluation of Heavy Metals Accumulation in Corbicula fluminea in Manadas Creek, Laredo, Texas

Addo-Mensah Alfred, Vaughan Thomas and Anaya Eduardo

Background and Objective: The Manadas Creek in Laredo, Texas is a tributary of the Rio Grande which is the source of drinking water for the city of Laredo as well as many communities downstream. Portions of the creek were sunk to runoff from a decommissioned antimony smelter plant operated by Anzon America Inc. This project was designed to study the bioavailability of trace metals to flora and fauna in the creek. Materials and Methods: Corbicula fluminea (Asiatic clam) was used as a biomarker to determine bioaccumulation. Clams were placed in cages on three sites along Manadas Creek in Laredo, Texas. Concentrations of heavy metals (As, Cd, Ni, Pb and Sb) in the soft tissues of the Asiatic clam. Corbicula fluminea (C. fluminea) and water samples from Manadas Creek were determined to assess the bioaccumulation of metals. Results: This study shows aqueous Ni (7.90-16.57 μg L^–1) and Cd (1.04-2.52 μg L^–1) concentration levels below the maximum contaminant level throughout Manadas Creek, whereas portions of the creek, close to the Anzon smelting plant recorded as 47.99 μg L^–1, Pb (53.86 μg L^–1) and Sb (22.80 μg L^–1) concentrations higher than background concentrations of unpolluted waters. Metal accumulation in C. fluminea (dry weight) by as 16.20 mg kg^–1, Pb (16.31 mg kg^–1) and Sb (16.43 mg kg^–1) were higher than the maximum allowable limit set by the US Food and Drug Administration. Conclusion: This study showed that metal concentrations in the creek are available for bio uptake.

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