BOOK OF ABSTRACTS 239 IHSS&IWA26 / BRNO / CZECHIA / 23–28 August 2026 Hall A Poster Session / Environment, Agriculture, and Forestry P4.14 Speciation and Seasonal Dynamics of Dissolved Germanium, Arsenic, and Antimony in Contrasting Czech Freshwater Reservoirs Jana Šišková1, Tomáš Matoušek2, Michaela Prokopová1, Martin Pivokonský1 1 Institute of Hydrology of the Czech Academy of Sciences, Department of Hydrochemistry and Technology, Pod Paťankou 30/5, 160 00 Prague, Czech Republic, siskova@ih.cas.cz 2 Institute of Analytical Chemistry of the Czech Academy of Sciences, Veveří 97, 602 00 Brno, Czech Republic Although the elements germanium (Ge), arsenic (As), and antimony (Sb) play a key role in modern technologies such as electronics, photovoltaics, and semiconductor devices, and are subsequently released into the environment, their environmental behaviour remains poorly understood. In freshwaters, germanium occurs mainly as inorganic species (iGe), typically exhibiting vertical stratification similar to silicon and occurring at ng.L-1 concentrations, or as organic methylated forms that are apparently biologically and chemically inert and detectable at sub ng.L-1 levels [1], such as monomethylgermanium and dimethylgermanium. Toxic arsenic is present mainly as inorganic arsenite and arsenate, as well as in methylated forms. The environmental behaviour of antimony is less well understood due to its lower abundance in aquatic systems. These elements originate from natural geochemical processes, such as weathering, and anthropogenic activities, and their seasonal dynamics are controlled by chemical and biological factors. In this study, two contrasting Czech drinking water reservoirs in the Elbe River basin were selected to investigate the seasonal speciation of dissolved elements: the eutrophic Vrchlice reservoir located near the town of Kutná Hora in a lowland catchment area heavily influenced by agriculture, and the oligotrophic Souš reservoir located on the Černá Desná River in a forested mountain catchment in the Jizerské Mountains historically affected by acid deposition. The speciation of dissolved Ge, As, and Sb was monitored monthly for one year. Sample collection was performed throughout the water column at the deepest points of water reservoirs. Several physical and hydrochemical parameters were analysed. Elemental species were determined by hydride generation-cryotrapping-inductively coupled plasma-tandem mass spectrometry (HG-CT-ICP-MS/MS) following a previously reported method [2]. Different behaviour of each element and its species in the vertical stratification was observed. Methylated Ge species maintained constant
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