Microplastics pollution on soft shores in Hong Kong

Abstract

Microplastics (< 5 mm) in sediments from eastern waters and western waters in Hong Kong were investigated to evaluate the significance of the Pearl River in microplastic pollution. Sediments and microplastics were collected from four sandy beaches in Hong Kong. They were Luk Keng Tsuen (LKT) and Sha Lo Wan (SLW) in the western part of Hong Kong in close proximity to the Pearl River estuary and Sha Tsui (ST) and To Tei Wan (TTW) in the eastern waters. Microplastics were extracted from sediments by density separation using zinc chloride solution (d > 1.6 g cm−3). 47.8 ± 12.1 particles per kilogram in ST, 5.0 ± 1.3 particles per kilogram in TTW, 29.0 ± 17.7 particles per kilogram in LKT and 8.5 ± 0.5 particles per kilogram in SLW were found under an optical microscope, respectively. These microplastics were identified by attenuated total reflectance Fourier-transform infrared (ATR-FTIR) spectroscopy. Polyethylene, nylon66, polyester (alkyd resin), polystyrene, polypropylene and poly (methyl methacrylate) were characterized to be major types of the microplastics. Results reported herein showed that the amount of microplastics at ST were significantly higher than at TTW and SLW. The results also indicated that instead of the Pearl River, local sources, which were mainly from various anthropogenic activities, were the major contributors of microplastics pollution. The results, however should interpret with caution due to limited number of sampling sites. A more comprehensive study involving more beaches is recommended if time is allowed.