摘要

基于球形几何形状的简单模型应用于描述来自纳米和微塑料颗粒的金属物质的释放动力学。汇编的文献数据表明，塑料聚合物体内金属物质的有效扩散系数D eff比适用于大量水介质中金属离子的有效扩散系数D eff低许多个数量级。因此，金属离子在水性介质中的扩散比塑料颗粒体内的扩散快得多。只要任何内球金属配合物的解离速率大于颗粒体内的扩散速率，后一工艺就是吸附在塑料体内的金属物质的总体释放动力学的限制步骤。粒子。吸附在颗粒/介质界面和/或与表面吸附配体相关的金属离子不需要穿过颗粒体，因此在扩散限制的情况下，它们的释放速率将对应于扩散速率。含水介质。无论颗粒内金属形态如何，对于给定的扩散系数，随着颗粒尺寸的减小，在给定时间范围内从塑料颗粒释放的金属物质的比例显着增加。通过实际例子讨论并说明了与水生系统中的塑料微米和纳米颗粒相关的金属物种的化学动力学和生物利用度的后续后果。

A simple model, based on spherical geometry, is applied to the description of release kinetics of metal species from nano- and micro-plastic particles. Compiled literature data show that the effective diffusion coefficients, D eff, for metal species within plastic polymer bodies are many orders of magnitude lower than those applicable for metal ions in bulk aqueous media. Consequently, diffusion of metal ions in the aqueous medium is much faster than that within the body of the plastic particle. So long as the rate of dissociation of any inner-sphere metal complexes is greater than the rate of diffusion within the particle body, the latter process is the limiting step in the overall release kinetics of metal species that are sorbed within the body of the plastic particle. Metal ions that are sorbed at the very particle/medium interface and/or associated with surface-sorbed ligands do not need to traverse the particle body and thus in the diffusion-limiting case, their rate of release will correspond to the rate of diffusion in the aqueous medium. Irrespective of the intraparticulate metal speciation, for a given diffusion coefficient, the proportion of metal species released from plastic particles within a given time frame increases dramatically as the size of the particle decreases. The ensuing consequences for the chemodynamics and bioavailability of metal species associated with plastic micro- and nano-particles in aquatic systems are discussed and illustrated with practical examples.

https://www.ncbi.nlm.nih.gov/pubmed/30631763