IHSS&IWA26 / BRNO / CZECHIA / 23–28 August 2026 BOOK OF ABSTRACTS 240 Poster Session / Environment, Agriculture, and Forestry Hall A behaviour in both reservoirs, consistent with previous findings from Lake Geneva [3]. These organic species are not produced by biological activity in reservoirs, and their origin remains unknown. According to iGe, in Vrchlice, concentration was influenced throughout the year by the diatom life cycle, with a decrease in the epilimnion from May to September due to incorporation into diatom frustules, and an increase in the hypolimnion from July to November due to cell autolysis. In contrast, no such cycle is present in Souš due to absence of diatoms. Arsenate is reduced to arsenite throughout the vegetative season of phytoplankton in the epilimnion and subsequently methylated; in the hypolimnion, arsenic remains in its oxidised form. Indications of accumulation of arsenic and germanium in the sediment were observed. Vertical stratification of antimony is likely affected by bacterial activity, with no influence from phytoplankton. Methylated forms of antimony were detected at very low levels. References 1. T. Matoušek, M. Prokopová, M. Pivokonský, M. Filella, Environmental Science: Processes & Impacts (2026) DOI:10.1039/d6em00068a 2. T. Matoušek, S. Adamová, M. Prokopová, M. Pivokonský, S. Musil, M. Filella, Spectrochimica Acta Part B 240 (2026) 107501. 3. M. Filella, T. Matoušek, Applied Geochemistry 143 (2022) 105352. Acknowledgement This work was supported by project Strategy AV21 – Water for Life and Czech Academy of Sciences Praemium Academiae.
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