Publications by authors named "Alexander Leven"

Article Synopsis
  • The study explored how adding Mn(IV)-oxide phases like pyrolusite or birnessite could help remediate mercury-contaminated sediments by affecting redox potential and reducing mercury methylation.
  • In tank experiments, changes in the mineral forms and oxidation states of manganese were tracked over 4 to 15 months, revealing differing rates of reduction between the two compounds, with birnessite showing quicker conversion to Mn(II) carbonate.
  • The findings indicated that the effectiveness and longevity of manganese amendments in controlling sediment redox conditions depend on the type of manganese oxide used, along with its physical properties, suggesting different strategies may be needed for optimal treatment depending on the conditions at specific sites.
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Manganese(iv) oxide (pyrolusite, birnessite) mineral amendments can reduce dissolved MeHg concentrations in sediment theoretically by inhibiting microbial sulfate reduction, which is a major methylation pathway in sediments. Anaerobic sediment slurry microcosms in which Hg methylation was stimulated by addition of labile organic carbon (acetate) and HgCl2 showed that manganese(iv) oxide reduced the percent MeHg in slurry porewater (filtered), by 1-2 orders of magnitude relative to controls. Sediment-water mesocosms with pyrolusite or birnessite either directly mixed into the top 5 cm or applied in a thin (5 cm) sand layer over sediment showed reductions in percent MeHg in porewater of 66-69% for pyrolusite and 81-89% for birnessite amendment.

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