| Summary: | Current methodologies for microplastic detection in the environment, including surface freshwaters, are imperfect; no standardized methods for sampling and sample preparation are available. The paper discusses the issues of comparability of microplastic surveys conducted by different methods. An intercalibration experiment carried out on the Yenisei River by two research labs – Research Center ‘Microplastic Siberia’, Tomsk State University, and PlasticLab, Russian State Hydrometeorological University – is described in detail, including the laboratory protocols and QA/QC issues. Two different sampling techniques – Manta trawl and filtration pump – showed that the total microplastic content in trawl samples was significantly lower (p < 0.01) than that in pump samples (on average 30-fold lower): 2.04–4.85 and 93.0–107 items/m3, corre-spondingly. The problem of incomparability of the quantitative estimates obtained by different sampling methods was confirmed, suggesting their complementarity. At the same time, differences in the morphology of the detected particles sampled by different instruments suggest that river surface and subsurface layers transport different micro-plastics. The study showed that sampling methods but not different laboratory protocols for sample processing are primarily important for the consistency of the results of quan-titative analysis of riverine microplastics, which suggests relevance of harmonization of sampling methods.
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