滨海河口潮滩中微塑料的表面风化和成分变化

Microplastics have received increasing attention as emerging environmental pollutants. However, little is known about the surface morphology, composition and their changes of different types of microplastics in the real environment, and the corresponding methodological research is mostly in the exploratory stage. In this study, the estuarine tidal flats along the Yellow Sea and Bohai Sea, which are strongly affected by human activities, were taken as the object. Various microscopic techniques and microanalysis methods were used to study the types, surface morphology and composition changes of microplastics. The analysis using an optical microscope and a scanning electron microscope (SEM) showed that in addition to morphological types such as fragments, fibers and films, there are also foamed and resin particles among the microplastics in the tidal flat environment. The surface presents wrinkles, micropores, cracks or protrusions of different shapes and sizes, which may have been affected by mechanical friction, chemical oxidation or biological erosion. Using an attenuated total reflection Fourier transform infrared spectrometer (ATR - FT - IR), on the basis of analyzing the polymer composition of microplastics, oxygen - containing functional groups such as carboxylic acids, aldehydes, esters or ketones on the surface of microplastics in the tidal flat environment were identified. Through pyrolysis gas chromatography - mass spectrometry (pyr - GC - MS), it was not only identified that the fibrous microplastics are a blend of polyethylene and polypropylene polymers, but also the compositional differences between the weathered surface layer of the foamed type and the interior after the weathered surface layer was peeled off were observed. Among them, oxygen - containing and nitrogen - containing chemicals such as oleonitrile, erucamide, a - N - demethylmethadol, methyl 1,1 - diphenyl - spiro - hexane - 5 - carboxylate, octadecyl palmitate and hexadecyl palmitate are unique to the weathered surface layer, further confirming the existence of oxygen - containing substances on the surface of microplastics in the estuarine tidal flat environment. It can be seen that the surface of microplastics in the environment undergoes compositional changes while being weathered. In the future, attention should be paid to the research on the surface change process and ecological environmental effects of microplastics in the coast and ocean.

微塑料作为新兴环境污染物日益受到关注,但对真实环境中不同类型微塑料的表面形貌、成分及其变化了解甚少,相应的方法学研究多处于探索阶段.本研究以受人类活动强烈影响的黄渤海沿岸河口潮滩为对象,运用多种显微技术和微分析方法,研究了微塑料类型、表面形貌及其成分变化.采用光学显微镜和扫描电子显微镜(scanning electron microscope, SEM)分析表明,潮滩环境中微塑料除了碎片、纤维、薄膜等形貌类型外,还存在发泡类和树脂类颗粒.表面呈现不同形状和大小的皱褶、微孔、裂纹或凸起等,可能受到了机械摩檫、化学氧化或生物侵蚀等作用.运用衰减全反射傅里叶变换红外光谱仪(attenuated total reflection Fourier transform infrared spectroscopy, ATR-FT-IR),在分析微塑料聚合物成分的基础上,鉴定出潮滩环境中微塑料表面具有羧酸、醛、酯或酮类等含氧官能团.通过裂解气相色谱-质谱(pyrolysis gas chromatography-mass spectrometry, pyr-GC-MS)不仅鉴定出纤维类微塑料是聚乙烯与聚丙烯共混聚合物,还观测到发泡类风化表层与剥离风化表层后的内部之间的成分差异,其中,油酸腈、芥酸酰胺、a-N-去甲基美沙醇、1,1-二苯基-螺-己烷-5-羧酸甲酯、棕榈酸十八酯和棕榈酸十六酯等含氧、含氮化学物为风化表层特有,进一步证实了河口潮滩环境中微塑料表面含氧物质的存在.由此可见,环境中微塑料表面在风化的同时还发生了成分的变化.未来应关注海岸和海洋中微塑料的表面变化过程和生态环境效应研究.