Department of Chemistry and Industrial Chemistry, University of Pisa, Pisa, Italy.
Department of Chemistry and Industrial Chemistry, University of Pisa, Pisa, Italy; National Interuniversity Consortium of Materials Science and Technology (INSTM), Florence, Italy.
Water Res. 2022 Jul 1;219:118521. doi: 10.1016/j.watres.2022.118521. Epub 2022 Apr 28.
Microplastics are the particulate plastic debris found almost everywhere as environmental contaminants. They are not chemically stable persistent pollutants, but reactive materials. In fact, synthetic polymers exposed to the environment undergo chemical and physical degradation processes which lead not only to mechanical but also molecular fragmentation, releasing compounds that are potentially harmful for the environment and human health. We carried out accelerated photo-oxidative ageing of four reference microplastics (low- and high-density polyethylene, polypropylene, and polystyrene) directly in artificial seawater. We then made a characterization at the molecular level along with a quantification of the chemical species leached into water. Gas chromatography/mass spectrometry analyses performed after selective extraction and derivatization enabled us to identify more than 60 different compounds. Analysis of the leachates from the three polyolefins revealed that the main degradation products were mono- and dicarboxylic acids, along with linear and branched hydroxy acids. The highest amount of leached degradation species was observed for polystyrene, with benzoic acid and phenol derivatives as the most abundant, along with oligomeric styrene derivatives. The results from reference microplastics were then compared with those obtained by analyzing leachates in artificial seawater from aged plastic debris collected in a natural environment. The differences observed between the reference and the environmental plastic leachates mainly concerned the relative abundances of the chemical species detected, with the environmental samples showing higher amounts of dicarboxylic acids and oxidized species.
微塑料是作为环境污染物在几乎所有地方都能发现的颗粒状塑料碎片。它们不是化学稳定的持久性污染物，而是反应性物质。事实上，暴露于环境中的合成聚合物会经历化学和物理降解过程，这不仅导致机械破碎，还导致分子碎片化，释放出可能对环境和人类健康有害的化合物。我们直接在人工海水中对四种参考微塑料（低密度和高密度聚乙烯、聚丙烯和聚苯乙烯）进行了加速光氧化老化。然后，我们进行了分子水平的表征，并对浸出到水中的化学物质进行了定量分析。经过选择性提取和衍生化的气相色谱/质谱分析使我们能够识别出 60 多种不同的化合物。对三种聚烯烃浸出物的分析表明，主要的降解产物是单羧酸和二羧酸，以及线性和支化羟基酸。从聚苯乙烯中观察到最多的浸出降解产物，苯甲酸和苯酚衍生物以及低聚物苯乙烯衍生物是最丰富的。然后将参考微塑料的结果与从自然环境中收集的老化塑料碎片的人工海水中浸出物的分析结果进行了比较。参考和环境塑料浸出物之间观察到的差异主要涉及检测到的化学物质的相对丰度，环境样品显示出更多的二羧酸和氧化物质。
