College of Environmental Science and Engineering, Ministry of Education Key Laboratory of Pollution Processes and Environmental Criteria, Tianjin Key Laboratory of Environmental Remediation and Pollution Control , Nankai University , Tianjin 300350 , P. R. China.
State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment , Nanjing University , Nanjing 210023 , P. R. China.
Environ Sci Technol. 2019 May 21;53(10):5805-5815. doi: 10.1021/acs.est.9b00787. Epub 2019 May 1.
Plastic debris, in particular, microplastics and nanoplastics, is becoming an emerging class of pollutants of global concern. Aging can significantly affect the physicochemical properties of plastics, and therefore, may influence the fate, transport, and effects of these materials. Here, we show that aging by UV or O exposure drastically enhanced the mobility and contaminant-mobilizing ability of spherical polystyrene nanoplastics (PSNPs, 487.3 ± 18.3 nm in diameter) in saturated loamy sand. Extended Derjaguin-Landau-Verwey-Overbeek calculations and pH-dependent transport experiments demonstrated that the greater mobility of the aged PSNPs was mainly the result of surface oxidation of the nanoplastics, which increased not only the surface charge negativity, but more importantly, hydrophilicity of the materials. The increased mobility of the aged PSNPs significantly contributed to their elevated contaminant-mobilizing abilities. Moreover, aging of PSNPs enhanced the binding of both nonpolar and polar contaminants, further increasing the contaminant-mobilizing ability of PSNPs. Interestingly, aging enhanced binding of nonpolar versus polar compounds via distinctly different mechanisms: increased binding of nonpolar contaminants (tested using pyrene) was mainly the result of the modification of the polymeric structure of PSNPs that exacerbated slow desorption kinetics; for polar compounds (4-nonylphenol), aging induced changes in surface properties also resulted in irreversible adsorption of contaminants through polar interactions, such as hydrogen bonding. The findings further underline the significant effects of aging on environmental fate and implications of nanoplastics.
塑料碎片，特别是微塑料和纳米塑料，正成为全球关注的新兴污染物。老化会显著影响塑料的物理化学性质，因此可能会影响这些材料的归宿、迁移和效应。在这里，我们表明，通过紫外线或臭氧暴露进行的老化会极大地增强球形聚苯乙烯纳米塑料（PSNP，直径为 487.3±18.3nm）在饱和壤土中的迁移性和污染物迁移能力。扩展的德加古因-兰德劳-韦尔拜克（Derjaguin-Landau-Verwey-Overbeek）计算和 pH 依赖的迁移实验表明，老化 PSNP 的更高迁移性主要是由于纳米塑料的表面氧化，这不仅增加了表面电荷的负电性，而且更重要的是增加了材料的亲水性。老化 PSNP 的更高迁移性显著促进了它们对污染物的更高迁移能力。此外，PSNP 的老化增强了非极性和极性污染物的结合，进一步增加了 PSNP 的污染物迁移能力。有趣的是，老化通过明显不同的机制增强了非极性和极性化合物的结合：非极性污染物（通过芘测试）的结合增加主要是由于 PSNP 聚合结构的改性，加剧了缓慢解吸动力学；对于极性化合物（4-壬基酚），老化引起的表面性质变化也导致通过氢键等极性相互作用不可逆地吸附污染物。这些发现进一步强调了老化对纳米塑料环境归宿和影响的重要影响。
