This report describes the results of work performed under the abovementioned activity in 2017 and during biennium of 2018-2019, and follows findings indicated in previous POMRAC technical report #13. Specific objective of this activity is to trace possible impact of rivers on microplastics quantity and composition in the coastal waters within the Russian part of the NOWPAP region and to obtain background information on the distribution of different kinds of microplastics in these rivers. We also try to reveal possible impact of seasonal factor on river discharge and distribution of the contaminant in the coastal marine environment and geographical peculiarities of such distribution.