Marine Debris Polymers on Main Hawaiian Island Beaches, Sea Surface, and Seafloor

Polymeric differences of plastic debris were assessed across four compartments of the Main Hawaiian Islands (sea surface, windward beaches, leeward beaches, and seafloor) to better describe sources and fate. Plastic debris pieces (n = 4671) were collected from 11 beaches, three sea surface tows, and three seafloor dives. Fourier transform infrared spectroscopy identified the polymers of 3551 pieces. Significant differences (p 2) than leeward beaches, despite smaller human populations on windward sides. Sea surface and windward beaches were dominated by severely weathered, less dense floating polymers (polyethylene and polypropylene comprised 92.7 and 93.5% on average, respectively, of the total debris mass), while leeward beaches and the seafloor debris consisted of less weathered and more dense sinking polymers (e.g., 41.0 and 44.7% of total mass consisted of the sum of polystyrene, nylon, cellulose acetate, polyethylene terephthalate, and additive-masked debris). These results are some of the first to provide evidence of polymeric stratification in the marine environment and emphasize that the majority of marine debris in Hawaii is floating in from distant sources rather than from Hawaii’s residents or tourists.为更精准阐释塑料垃圾的来源与归趋，本研究针对夏威夷主群岛的四类环境介质（海表、向风海滩、背风海滩与海底）开展了塑料垃圾的聚合物组成差异分析。研究共采集塑料垃圾样本4671件，采样覆盖11处海滩、3次海面拖网作业以及3次海底潜水探查。采用傅里叶变换红外光谱（Fourier Transform Infrared Spectroscopy）对其中3551件样本的聚合物类型完成鉴定。结果显示，向风海滩的聚合物组成与其余三类环境介质存在显著差异；尽管向风区域常住人口规模更小，但向风海滩的低密度聚合物占比显著高于背风海滩。海表与向风海滩的塑料垃圾以严重老化的低密度漂浮型聚合物为主：聚乙烯与聚丙烯的平均总质量占比分别达92.7%与93.5%；而背风海滩与海底的塑料垃圾则以老化程度更低的高密度沉降型聚合物为主，其中聚苯乙烯、尼龙、醋酸纤维素、聚对苯二甲酸乙二酯以及添加剂遮蔽型垃圾的总质量占比分别为41.0%与44.7%。本研究结果为海洋环境中聚合物分层分布现象提供了首批实证之一，同时证实夏威夷海域的绝大多数海洋塑料垃圾均来自域外输入，而非本地居民或游客产生的垃圾。