Microbial Mobilization of Arsenic from Sediments of the Aberjona Watershed

• Published in: Environmental science & technology Vol. 31; no. 10; pp. 2923 - 2930
• Main Authors: Ahmann, Dianne, Krumholz, Lee R, Hemond, Harold F, Lovley, Derek R, Morel, François M. M
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 01-10-1997
• Subjects: Animal, plant and microbial ecology; Applied ecology; ARSENIC; ARSENICO; BASSIN VERSANT; Biological and medical sciences; Chemistry; CUENCAS HIDROGRAFICAS; Ecotoxicology, biological effects of pollution; Environmental impact; Fresh water environment; Freshwater; Fundamental and applied biological sciences. Psychology; Microbiology; SEDIMENT; SEDIMENTO; Sediments; Water pollution; WATERSHEDS; United States; North America; Massachusetts; America; Microbial activity; Ecotoxicology; Arsenic; Sediments; Dissolution; Freshwater environment; Chemical reduction; Pollutant; Mobilization; Watershed; Lakes; Bacteria; Water pollution; Stream; Chemical contamination
• ISSN: 0013-936X; 1520-5851
• DOI: 10.1021/es970124k

Arsenic mobilization from aquatic sediments is an issue of concern, as water-borne arsenic can migrate into pristine areas, endangering aquatic organisms and people. Such mobilization in the Aberjona Watershed has distributed nearly 20 t of arsenic throughout river and lake sediments. To gain an understanding of possible biological mechanisms contributing to this transport, mobilization of solid-phase arsenic was investigated in upper Aberjona sediment microcosms. Microcosms catalyzed rapid dissolution of arsenic from iron arsenate, a solid-phase surrogate for sedimentary arsenic, mobilizing 20−28% of the arsenic present. Sterilization prevented this transformation. Reduction of arsenate to arsenite accompanied iron arsenate dis solution, suggesting that reduction was driving dissolution. Sediment-conditioned, filter-sterilized medium showed no arsenic-transforming activity. A native enrichment culture of sulfate-reducing bacteria possessed one-fifth of the microcosm activity, while strain MIT-13, a native arsenate-reducing microorganism, showed much greater activity, dissolving 38% of the arsenic present. Furthermore, strain MIT-13 mobilized arsenic from presterilized, unamended upper Aberjona sediments. These observations indicate that a direct microbial arsenic-mobilizing activity exists in the sedi ments, show that strain MIT-13 is a strong arsenic-transforming agent native to the sediments, and suggest that dissimilatory arsenic reduction may contribute to arsenic flux from anoxic sediments in the most arsenic-contaminated region of the Aberjona Watershed.