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A novel paper by Chalov et al. (2020) presents the fate of river-borne chemicals under control by changing flow conditions. The study which is based on the novel approach and combines together sampling and acoustic Doppler current profiler (ADCP) water velocity transects, allows to accurately estimate the depth-integrated instantaneous chemicals flux.

Chalov, S.; Moreido, V.; Sharapova, E.; Efimova, L.; Efimov, V.; Lychagin, M.; Kasimov, N. Hydrodynamic Controls of Particulate Metals Partitioning Along the Lower Selenga River—Main Tributary of The Lake Baikal. Water 2020, 12, 1345. https://doi.org/10.3390/w12051345

Downstream effects of pollutants spreading due to hydromorphological gradient and associated changes in sediment transport conditions along braided-meandering and deltaic distributary reach of the large river downstream section are discussed. We demonstrate the significance of the hydrodynamic control for sediment-associated metal partitioning along river. Typically, downward decline of the sediment and metals spreading towards the Lake is observed due to buffer effects in the delta. During peak flow, the longitudinal gradients in heavy metals’ concentration along distributary delta reach were neglected due to higher concentrations delivered from upper parts of the river. In particular, significant variation of heavy metals’ concentrations associated with the river depth were related to sediment concentration and flow velocity profiles. Various particulate metals’ behavior in silt-sand delta channel and sand-gravel Selenga main stem emphasize the importance of near-bottom exchange for particles spreading with the river flow. Using empirically derived Rouse numbers, we found quantitative relationships between ratio of particulate metals sorting throughout depth in a single river channel and hydrodynamic conditions of sediment transport.

Text by Dr. Sergey Chalov, PEEX-Moscow Office, Lomonosov Moscow State University

Fig 1. in Chalov et al. (2020) Water 2020, 12, 1345. https://doi.org/10.3390/w12051345

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