| Summary: | The difference in concentration of filterable trace metals, macro ions, nitrate and dissolved organic carbon (DOC) after capsule and membrane 0.45 µm filters was studied at the seasonal sampling of the typical medium size boreal Razdolnaya River, Far East of Russia. Trace metals showed notable decrease after membrane filtration compared with capsules, though concentrations of macro ions, nitrates and DOC were equal. Clogging of membranes with subsequent retention of coarse colloids was suggested as a reason for this difference. In summer the dissimilarity in concentration grew in order Cu < Zn < Ni, Cd < Mn < Fe reflecting a significant role of coarse colloids in the pool of filterable forms for Fe and Mn. In winter, retention of Mn was declined due to input of ionic forms from redox cycle. Floods are the periods with the most notable increase of coarse colloids content and maximum bias in the determination of filterable trace metals if frontal membrane filtration is being used.
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