해변 플라스틱 쓰레기의 크기 그룹간 관계를 이용한 미세 플라스틱 오염 평가

Abstract

Micro-plastic marine debris is an emerging marine environmental issue. These small particles of plastic debris can be widely distributed and be more likely ingested by marine life with decreasing size. Information about the abundance and spatiotemporal distribution of micro-plastics is essential for the development of management strategy. However, relevant data have not been well documented because micro-plastic surveys require much more time, labor, and technical support in comparison with surveys of larger debris. The purpose of this study is to determine relationships among the abundances of macro-, meso-, and micro-plastic debris size classes to provide insights for the development of efficient micro-plastic survey methods.

Plastic debris on six beaches near the Nakdong River Estuary and east coasts of Geoje island, Korea, was sampled in May and September 2012. Collected plastic debris was classified into four types, of intact plastic, Styrofoam, fragment, other foamed plastics and three size groups, of micro (1∼<5 mm), meso (5∼< 25 mm), and macro (≥25 mm). Abundance and weight were measured for each type and size group of plastic debris. Relationships between the abundances of size groups were statistically examined using Spearman's rank correlation coefficient.

Average abundances of macro-, meso-, and micro-plastics on six beaches in the first survey in May, 2012, were 1, 239, and 8,205 particles/㎡, respectively. Average weights were 11 g/㎡ for macro-, 16 g/㎡ for meso-, and 7 g/㎡ for micro-plastics. Average abundance of macro-plastics observed in the second survey in September, 2012, was 1 particles/㎡, that of meso-plastics 237 particles/㎡, and that of micro-plastics 27,606 particles/㎡. Average weights of macro-, meso-, and micro-plastics in the second survey were 15, 26, 32 g/㎡, respectively. Styrofoam was the most abundant plastic debris both in micro- and meso-size groups, while intact plastics were the most common item in macro-plastic debris. Composition of plastic debris was significantly different between the first and second surveys, while their abundance and weight were not.

The most strong correlation between size groups was found in the abundances of meso- and micro-plastics. Correlation between the abundances of macro- and meso-plastics was higher than that between macro- and micro-plastics. This study demonstrated that considering the difficulties involved in surveys of very small plastic debris, meso-size plastic debris could be used for rapidly assessing micro-plastic pollution on beaches in Korea.