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Sulfidization of Organic Freshwater Flocs from a Minerotrophic Peatland : Speciation Changes of Iron, Sulfur, and Arsenic

Titelangaben

Thomas Arrigo, Laurel K. ; Mikutta, Christian ; Lohmayer, Regina ; Planer-Friedrich, Britta ; Kretzschmar, Ruben:
Sulfidization of Organic Freshwater Flocs from a Minerotrophic Peatland : Speciation Changes of Iron, Sulfur, and Arsenic.
In: Environmental Science & Technology. Bd. 50 (2016) Heft 7 . - S. 3607-3616.
ISSN 0013-936X
DOI: https://doi.org/10.1021/acs.est.5b05791

Abstract

Iron-rich organic flocs are frequently observed in surface waters of wetlands and show a high affinity for trace metal(loid)s. Under low-flow stream conditions, flocs may settle, become buried, and eventually be subjected to reducing conditions facilitating trace metal(loid) release. In this study, we reacted freshwater flocs (704–1280 mg As/kg) from a minerotrophic peatland (Gola di Lago, Switzerland) with sulfide (5.2 mM, S(-II)spike/Fe = 0.75–1.62 mol/mol) at neutral pH and studied the speciation changes of Fe, S, and As at 25 ± 1 °C over 1 week through a combination of synchrotron X-ray techniques and wet-chemical analyses. Sulfidization of floc ferrihydrite and nanocrystalline lepidocrocite caused the rapid formation of mackinawite (52–81% of Fesolid at day 7) as well as solid-phase associated S(0) and polysulfides. Ferrihydrite was preferentially reduced over lepidocrocite, although neoformation of lepidocrocite from ferrihydrite could not be excluded. Sulfide-reacted flocs contained primarily arsenate (47–72%) which preferentially adsorbed to Fe(III)-(oxyhydr)oxides, despite abundant mackinawite precipitation. At higher S(-II)spike/Fe molar ratios (≥1.0), the formation of an orpiment-like phase accounted for up to 35% of solid-phase As. Despite Fe and As sulfide precipitation and the presence of residual Fe(III)-(oxyhydr)oxides, mobilization of As was recorded in all samples (Asaq = 0.45–7.0 μM at 7 days). Aqueous As speciation analyses documented the formation of thioarsenates contributing up to 33% of Asaq. Our findings show that freshwater flocs from the Gola di Lago peatland may become a source of As under sulfate-reducing conditions and emphasize the pivotal role Fe-rich organic freshwater flocs play in trace metal(loid) cycling in S-rich wetlands characterized by oscillating redox conditions.

Weitere Angaben

Publikationsform: Artikel in einer Zeitschrift
Begutachteter Beitrag: Ja
Zusätzliche Informationen: BAYCEER134608
Institutionen der Universität: Fakultäten > Fakultät für Biologie, Chemie und Geowissenschaften > Fachgruppe Geowissenschaften > Professur Umweltgeochemie
Fakultäten > Fakultät für Biologie, Chemie und Geowissenschaften > Fachgruppe Geowissenschaften > Professur Umweltgeochemie > Professur Umweltgeochemie - Univ.-Prof. Dr. Britta Planer-Friedrich
Forschungseinrichtungen
Forschungseinrichtungen > Forschungszentren
Forschungseinrichtungen > Forschungszentren > Bayreuther Zentrum für Ökologie und Umweltforschung - BayCEER
Fakultäten
Fakultäten > Fakultät für Biologie, Chemie und Geowissenschaften
Fakultäten > Fakultät für Biologie, Chemie und Geowissenschaften > Fachgruppe Geowissenschaften
Titel an der UBT entstanden: Ja
Themengebiete aus DDC: 500 Naturwissenschaften und Mathematik
Eingestellt am: 16 Aug 2016 06:39
Letzte Änderung: 16 Aug 2016 06:39
URI: https://eref.uni-bayreuth.de/id/eprint/33944