Spatiotemporal Distribution and Characteristic of > 20 ㎛ Microplastics and Annual Load on Nakdong River in South Korea

Abstract

River is an important pathway for transporting plastics to the oceans. Nevertheless, abundance, composition and load of riverine microplastics, especially less than 300 &#61549 m in m in m in m in size, is limited. The Nakdong River, the second largest river, in Korea was investigated spatially and seasonally. Surface water sampling was done in upstream (US), midstream (MS) and downstream (DS) in February (dry season), May (intermediate) and August (wet). Bottom water (DB) was also sampled in downstream. Each 100 L of river water was analyzed in triplicate and >20 &#61549 m microplastics was identified using micro m microplastics was identified using micro m microplastics was identified using microm microplastics was identified using micro m microplastics was identified using micro m microplastics was identified using microm microplastics was identified using micro m microplastics was identified using micro m microplastics was identified using micro m microplastics was identified using micro m microplastics was identified using micro m microplastics was identified using micro m microplastics was identified using microm microplastics was identified using micro m microplastics was identified using microm microplastics was identified using micro -FTIR. FTIR. FTIR. FTIR. FTIR. Mean abundance of microplastic on Nakdong River was in range of 293 (US, February)-4,760 (DS, August) n/m3. Abundance of microplastic on surface increased downstream in February and August, and DS > US > MS in May. Microplastic abundance was 1.8-3.7 times higher in surface than bottom water in all seasons. Microplastic less than 300 &#61549 m accounted for 66%, 81%, 72% of the total abundance in February, May and August, respectively. Dominant polymer type was polyester in February (32%), polypropylene in May (66%) and in August (38%). Fragment was most abundant shape (62-80%), and it was followed by fiber (20-38%). The annual microplastic load was estimated as 1.2×1013 n/y in Nakdong River. Top 20 cm surface water transported 9.9×1011 n/y, 1.1×1013 n/y was discharged by subsurface water.