Quantitative analysis of polyethylene terephthalate and polycarbonate microplastics in sediment collected from South Korea, Japan and the USA

Microplastics (MPs) have emerged as contaminants of public health and environmental concern. Although studies have reported the occurrence of MPs in sediment, quantitative determination of polyethylene terephthalate (PET) and polycarbonate (PC) concentrations is limited. In this study, marine coastal and freshwater sediment collected from various locations in South Korea, Japan and the United States were analyzed for PET and PC MPs using a depolymerization method of sample preparation followed by high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) detection. PET MPs were found in surface sediments from South Korea (n = 20), Japan (n = 4) and the United States (n = 43) at concentrations (dry weight) in the ranges of <MQL-13,000,000 ng/g (median: 6600 ng/g), 3600-5400 ng/g (4400 ng/g) and <MQL-10,000 ng/g (<MQL), respectively. Similarly, PC MPs were found in the concentration ranges of <MQL-140,000 ng/g (median: 290 ng/g, South Korea), 150-510 ng/g (100 ng/g, Japan) and <MQL-110,000 ng/g (160 ng/g, the United States). Spatial analysis of concentrations of PET and PC MPs in sediment from Lake Shihwa watershed in South Korea showed a decreasing trend with increasing distance from inland point source areas (Ansan industrial area). No distinct vertical profiles were recorded for PET or PC MPs in sediment cores collected from Tokyo Bay (Japan) or inland lakes in Michigan (the United States). The measured concentrations of MPs in sediment provide baseline data to evaluate future trends and for ecological risk assessment.