Lenz, Markus

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Markus
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Lenz, Markus

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2016 - 20202
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Autor:in: Eiche, Elisabeth ×

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    Publikation
    Tellurium and selenium sorption kinetics and solid fractionation under contrasting estuarine salinity and turbidity conditions
    (Elsevier, 2020) Gil-Díaz, Teba; Schäfer, Jörg; Keller, Virginia; Eiche, Elisabeth; Dutruch, Lionel; Mössner, Claudia; Lenz, Markus; Eyrolle, Frédérique [in: Chemical Geology]
    Tellurium (Te) is a Technology Critical Element (TCE) and a relevant product of nuclear fission. It has an unknown environmental biogeochemical cycle, mostly related to current analytical challenges in measuring its ultra-trace dissolved concentrations in complex environmental matrices. It is therefore generally compared to its geochemical pair selenium (Se), which shows a narrow range between diet essentiality and toxicity properties. Batch experiments using isotopically-labelled stable Te and Se were performed with fresh suspended particulate matter (SPM) from the fluvial part of the Gironde Estuary, simulating both estuarine salinity (S = 0 vs S = 32) and turbidity (100 mg L−1 vs 1000 mg L−1) gradients to understand the importance of the particulate phases in Te reactivity under estuarine conditions and verify the resemblance to Se behaviour. These experiments addressed sorption kinetics, sorption isotherms and fractionation from selective extractions of final equilibrated SPM. Results showed a strong, salinity-independent affinity of Te for the particulate phases (log10 Kd ~ 4.9 L kg−1), following a Langmuir-type isotherm. Contrastingly, Se adsorbs clearly less to estuarine SPM (log10 Kd ~ 2.5 L kg−1), following a Freundlich-type isotherm. Both isotherms and selective extractions highlighted differences between Te and Se sequestration. Selective extractions suggested higher mobility of particulate Se in contrast to Te. Based on these results the paper sets a first dispersion scenario on the environmental fate of radioactive Te and Se after hypothetical nuclear power plant accidental releases in coastal aquatic systems such as the Garonne-Gironde fluvial-estuarine system
    01A - Beitrag in wissenschaftlicher Zeitschrift
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    Publikation
    Arsenic Mobilization from Historically Contaminated Mining Soils in a Continuously Operated Bioreactor: Implications for Risk Assessment
    (Taylor & Francis, 2016) Rajpert, Liwia; Kolvenbach, Boris; Ammann, Erik; Hockmann, Kerstin; Nachtegaal, Maarten; Eiche, Elisabeth; Schäffer, Andreas; Corvini, Philippe; Sklodowska, Aleksandra; Lenz, Markus [in: Environmental Science & Technology]
    Concentrations of soil arsenic (As) in the vicinity of the former Złoty Stok gold mine (Lower Silesia, southwest Poland) exceed 1000 μg g–1 in the area, posing an inherent threat to neighboring bodies of water. This study investigated continuous As mobilization under reducing conditions for more than 3 months. In particular, the capacity of autochthonic microflora that live on natural organic matter as the sole carbon/electron source for mobilizing As was assessed. A biphasic mobilization of As was observed. In the first two months, As mobilization was mainly conferred by Mn dissolution despite the prevalence of Fe (0.1 wt % vs 5.4 for Mn and Fe, respectively) as indicated by multiple regression analysis. Thereafter, the sudden increase in aqueous As[III] (up to 2400 μg L–1) was attributed to an almost quintupling of the autochthonic dissimilatory As-reducing community (quantitative polymerase chain reaction). The aqueous speciation influenced by microbial activity led to a reduction of solid phase As species (X-ray absorption fine structure spectroscopy) and a change in the elemental composition of As hotspots (micro X-ray fluorescence mapping). The depletion of most natural dissolved organic matter and the fact that an extensive mobilization of As[III] occurred after two months raises concerns about the long-term stability of historically As-contaminated sites.
    01A - Beitrag in wissenschaftlicher Zeitschrift