RISING AND SETTLING PROPERTITY OF MICROPLASTICS IN RIVERS

Abstract

 We found double peaks in a vertical profile of microplastic concentration in rivers by conducting the field surveys for observing the vertical distribution of microplastic concentration in the Edo River. The first and second peaks appeared in the surface and bottom layer, respectively. The vertical profile was dependent on the specific gravity of microplastics, and the specific gravity found in bottom layer was significantly greater than that found in the surface layer. Furthermore, the settling velocity of microplastics was larger than their rising velocity according to their specific gravity. These indicate that the microplastics having greater specific gravity can concentrate regardless of vertical mixing in a river.