Comment on “Thioarsenite Detection and Implications for Arsenic Transport in Groundwater”

Planer-Friedrich, Britta

doi:10.1021/acs.est.0c01641

Cited by 4 publications

(1 citation statement)

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“…Thus, no clear mechanism can be easily extracted from the literature concerning As behaviour towards Fe-S surfaces in sulfidic conditions. This lack of consensus is probably related to the complex geochemical behaviour of As in such conditions because of the numerous possible, and still debated (Wilkin et al, 2019;Planer-Friedrich, 2020), chemical forms of this element (Couture and Van Cappellen, 2011).…”

Section: Matamorosmentioning

confidence: 99%

Influence of trace level As or Ni on pyrite formation kinetics at low temperature

Baya

Pape

Brest

et al. 2021

Geochimica et Cosmochimica Acta

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Pyrite formation at low temperature during early diagenesis in (sub-)surface sediments is an essential step of Fe and S biogeochemical cycles and the presence of this ubiquitous mineral of surface environments is often used as an indicator of paleo-redox conditions. Pathways of pyrite formation are usually discussed in environmental settings by involving a variety of nanosized Fe-S mineralogical precursors as a function of the local geochemical conditions. However, the influence of trace element impurities such as Ni and As in the solution at the time of pyrite formation has been poorly studied, whereas specific chemical signatures of trace elements are commonly observed in sedimentary pyrites.A better understanding of the impact of Ni and As incorporation at trace levels on pyrite formation is essential to help refining the use of these elements as paleo-redox indicators and to evaluate the role of pyrite as a sink regulating the biogeochemical cycle of potentially toxic trace elements. In this study, we have performed syntheses of pyrite at low temperature by the polysulfide pathway using aqueous Fe(III) and H 2 S in the presence of trace amounts of Ni(II) (0.001 mol%Fe) and As(III) (0.001 mol%Fe). Analysis of the solids collected at different time steps over the course of the experiments using X-Ray absorption spectroscopy at both the Fe and S K-edges shows that pyrite starts to precipitate within 5 days in presence of Ni(II) and within 32 days in presence of As(III), while the control experiment showed an intermediate precipitation rate of 14 days. Shell-by-shell analysis of Fe K-edge EXAFS data shows that the initial mineralogical precursors are the same whatever the experimental conditions and correspond to poorly-crystalline FeS (3.

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Section: Matamorosmentioning

confidence: 99%