Spatiotemporal Distribution and Annual Load of >20 &micro m Microplastics in the Nakdong River, South Korea

Abstract

River is an important pathway for transporting microplastics to the ocean. Nevertheless, the information of riverine microplastics, especially less than 300 &#61549 m in size, is limited. Nakdong River, the second largest river, in SouthKorea was investigated spatiotemporally. The abundance of microplastic increased toward the downstream, and was relatively high in February and August. Fragment type was dominant, and polypropylene or polyester was the most abundant polymer type. The abundance of microplastic in surface water was three times higher than bottom water in downstream. The composition of microplastic was similar in surface and bottom regardless of polymer density. Less than 300 &#61549 m sizerange accounted for 74% of the total abundance. The annual flux of microplastic was estimated as 5.4×1012 n/y and 53.3 ton/y in 2017. The proportion of load through the surface and subsurface water was 8% and 92%, respectively.hKorea was investigated spatiotemporally. The abundance of microplastic increased toward the downstream, and was relatively high in February and August. Fragment type was dominant, and polypropylene or polyester was the most abundant polymer type. The abundance of microplastic in surface water was three times higher than bottom water in downstream. The composition of microplastic was similar in surface and bottom regardless of polymer density. Less than 300 &#61549 m sizerange accounted for 74% of the total abundance. The annual flux of microplastic was estimated as 5.4×1012 n/y and 53.3 ton/y in 2017. The proportion of load through the surface and subsurface water was 8% and 92%, respectively.