Phthalic acid esters (phthalates) have been detected everywhere in the environment, but data on leaching kinetics and the governing mass transfer process into aqueous systems remain largely unknown. In this study, we experimentally determined time-dependent leaching curves for three phthalates di(2-ethylhexyl) phthalate, di(2-ethylhexyl) terephthalate, and diisononyl phthalate from polyvinyl chloride (PVC) microplastics and thereby enabled a better understanding of their leaching kinetics. This is essential for exposure assessment and to predict microplastic-bound environmental concentrations of phthalates. Leaching curves were analyzed using models for intraparticle diffusion (IPD) and aqueous boundary layer diffusion (ABLD). We show that ABLD is the governing diffusion process for the continuous leaching of phthalates because phthalates are very hydrophobic (partitioning coefficients between PVC and water log K_PVC/W were higher than 8.6), slowing down the diffusion through the ABL. Also, the diffusion coefficient in the polymer D_PVC is relatively high (∼8 × 10^–14 m² s^–1) and thus enhances IPD. Desorption half-lives of the studied PVC microplastics are greater than 500 years but can be strongly influenced by environmental factors. By combining leaching experiments and modeling, our results reveal that PVC microplastics are a long-term source of phthalates in the environment.

中文翻译：

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几十年来，聚氯乙烯微塑料将邻苯二甲酸盐浸出到水生环境中

邻苯二甲酸酯（邻苯二甲酸酯）在环境中随处可见，但关于浸出动力学和进入水系统的控制传质过程的数据仍然很大程度上未知。在本研究中，我们通过实验确定了聚氯乙烯 (PVC) 微塑料中三种邻苯二甲酸酯邻苯二甲酸二（2-乙基己基）酯、对苯二甲酸二（2-乙基己基）酯和邻苯二甲酸二异壬酯的时间依赖性浸出曲线，从而更好地了解它们的浸出动力学。这对于暴露评估和预测邻苯二甲酸盐的微塑料结合环境浓度至关重要。使用颗粒内扩散 (IPD) 和水边界层扩散 (ABLD) 模型分析了浸出曲线。K _PVC/W高于 8.6），减缓了通过 ABL 的扩散。_{此外，聚合物 D PVC}中的扩散系数相对较高（~8 × 10 ^–14 m ² s ^–1），因此提高了 IPD。所研究的 PVC 微塑料的解吸半衰期大于 500 年，但会受到环境因素的强烈影响。通过结合浸出实验和建模，我们的结果表明，PVC 微塑料是环境中邻苯二甲酸盐的长期来源。