摘要

在水生环境中越来越多地检测到微塑料（<5mm），其中含有的高含量溴化阻燃剂（BFRs）可能会影响水质。该研究表征了多溴联苯醚（PBDEs）和1,2-双（2,4,6-三溴苯氧基）乙烷（BTBPE）在环境相关温度下在水中的毫米级微塑料颗粒的释放动力学。发现由丙烯腈丁二烯苯乙烯（ABS）制成的微塑料颗粒的BFR浸出率受塑料基体内扩散的控制，塑料基质中的扩散系数（D）范围为10-28.30-10-20.84m2。 S-1。基于它们的温度依赖性和Arrhenius方程，BFRs扩散系数的表观活化能估计在64.1-131.8kJmol-1的范围内。 BFRs的扩散系数随其分子直径而减小，而扩散的活化能随着分子直径的增加而增加，这表明塑料基质中BFR扩散的显着空间位阻。在Log10D和塑料的玻璃化转变温度（Tg）之间观察到半经验线性关系，这允许预测BFR在海洋环境中常见的其他类型的微塑料中的扩散系数。如果微粒弹丸的物理和化学结构可以保持完整，则在微环境温度下BFR浸出（即50％耗尽）的半衰期将在数万至数千亿年的范围内。尽管在模型条件下来自微塑料的BFR的释放通量极低，但是天然环境中的一系列物理和化学过程以及摄入它们的生物体的消化系统可能通过引起塑料基质的破坏和膨胀而加速其浸出。 

Microplastics (<5 mm) are increasingly detected in aquatic environment, and the high levels of brominated flame retardants (BFRs) contained in them can potentially impact water quality. This study characterized the release kinetics of polybrominated diphenyl ethers (PBDEs) and 1,2-bis(2,4,6-tribromophenoxy)ethane (BTBPE) from millimeter-sized microplastic pellets in water at environmentally relevant temperatures. Leaching rates of BFRs from the microplastic pellets made of acrylonitrile butadiene styrene (ABS) were found to be controlled by their diffusion within the plastic matrix, and their diffusion coefficients (D) in the plastic matrices ranged from 10-28.30 to 10-20.84 m2 s-1. The apparent activation energies of the BFRs' diffusion coefficients were estimated to be in the range of 64.1-131.8 kJ mol-1 based on their temperature dependence and the Arrhenius equation. The diffusion coefficients of the BFRs decrease with their molecular diameters, while the activation energies for diffusion increase with the molecular diameters, which are indicative of significant steric hindrance for BFR diffusion within the plastic matrices. A semi-empirical linear relationship was observed between Log10D and the glass transition temperature (Tg) of plastics, which allows prediction of the diffusion coefficients of BFRs in other types of microplastics commonly found in marine environment. The half-lives of BFR leaching (i.e., 50% depletion) from the microplastic pellets would range from tens of thousands to hundreds of billions of years at ambient temperatures if their physical and chemical structures could remain intact. Although the release fluxes of BFRs from microplastics are extremely low under the model conditions, a range of physical and chemical processes in the natural environment and the digestive systems of organisms that ingested them could potentially accelerate their leaching by causing breakdown and swelling of the plastic matrices.

https://www.ncbi.nlm.nih.gov/pubmed/30597444