water Article River Water Quality of the Selenga-Baikal Basin: Part II—Metal Partitioning under Different Hydroclimatic Conditions Nikolay Kasimov 1, Galina Shinkareva 1,* , Mikhail Lychagin 1, Sergey Chalov 1 , Margarita Pashkina 1, Josefin Thorslund 2 and Jerker Jarsjö 2 1 Faculty of Geography, Lomonosov Moscow State University, 119991 Moscow, Russia;
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[email protected]; Tel.: +7-909-633-2239 Received: 4 July 2020; Accepted: 20 August 2020; Published: 26 August 2020 Abstract: The partitioning of metals and metalloids between their dissolved and suspended forms in river systems largely governs their mobility and bioavailability. However, most of the existing knowledge about catchment-scale metal partitioning in river systems is based on a limited number of observation points, which is not sufficient to characterize the complexity of large river systems. Here we present an extensive field-based dataset, composed of multi-year data from over 100 monitoring locations distributed over the large, transboundary Selenga River basin (of Russia and Mongolia), sampled during different hydrological seasons. The aim is to investigate on the basin scale, the influence of different hydroclimatic conditions on metal partitioning and transport. Our results showed that the investigated metals exhibited a wide range of different behaviors. Some metals were mostly found in the dissolved form (84–96% of Mo, U, B, and Sb on an average), whereas many others predominantly existed in suspension (66–87% of Al, Fe, Mn, Pb, Co, and Bi).