Biogeochemistry of metalliferous peats: Sulfur speciation and depth distributions of dsrAB genes and Cd, Fe, Mn, S, and Zn in soil cores

Martinez, Carmen Enid; Yanez, Carolina; Yoon, Soh-joung; Bruns, Mary Ann

Abstract

Spatial relationships between concentrations of Cd, Fe, Mn, S, and Zn and bacterial genes for dissimilatory sulfate reduction were studied in soils of the Manning peatland region in western New York. Peat cores were collected within a field exhibiting areas of Zn phytotoxicity, and pH and elemental concentrations were determined with depth. The oxidation states of S were estimated using S-XANES spectroscopy. Soil microbial community DNA was extracted from peat soils for ribosomal RNA intergenic spacer analysis (RISA) of diversity profiles with depth. To assess the presence of sulfate-reducing microorganisms (SRM), DNA extracts were also used as templates for PCR detection of dsrAB genes coding for dissimilatory (bi)sulfite reductase. Elemental distributions, S redox speciation, and detection of dsrAB genes varied with depth and water content. The pH of peat soils increased with depth. The highest concentrations of Zn, Cd, and S occurred at intermediate depths, whereas Mn concentra tions were highest in the topmost peat layers. Iron showed a relatively uniform distribution with depth. Concentrations of redox sensitive elements, S and Mn, but not Fe, seemed to respond to variations in water content and indicated vertical redox stratification in peat cores where topmost peats were typically acidic and oxidizing and deeper peats were typically circumneutral and reducing. Even then, S-XANES analyses showed that surface peats contained > 50% of the total S in reduced forms while deep peats contained generally 5% of the total S in oxidized forms. While bacterial RISA profiles of the peats were diverse, dsrAB gene detection followed redox stratification chemistry closely. For the most part, dsrAB genes were detected in deeper peats, where S accumulation was evident, while they were not detected in topmost peat layers where Mn accumulation indicated oxic conditions. Combined chemical, spectroscopic, and microbiological analyses indicated that prolonged exposure to dry-wet cycles resulted in the formation of two redox-stratified zones with distinct chemical and microbiological signatures within peat cores of the Manning peatland region. As illustrated in this study, changes in redox conditions affect bacterial community composition and downward mobility of toxic elements, which has implications for water contamination and the design of metal remediation strategies.

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Título según WOS: ID WOS:000248343600021 Not found in local WOS DB
Título de la Revista: ENVIRONMENTAL SCIENCE & TECHNOLOGY
Volumen: 41
Número: 15
Editorial: AMER CHEMICAL SOC
Fecha de publicación: 2007
Página de inicio: 5323
Página final: 5329
DOI:

10.1021/es070555v

Notas: ISI