School of Chemistry and Environmental Engineering, Jiangsu University of Technology, 1801 Zhongwu Avenue, Changzhou, 213001, China.
Environ Res. 2022 Sep;212(Pt D):113548. doi: 10.1016/j.envres.2022.113548. Epub 2022 May 22.
The sorption behavior of single contaminant on microplastics (MPs) has been extensively studied; however, little is known about that in the more actual scenario containing multiple contaminants. In this study, the interaction between triclosan (TCS) and its primary metabolite, methyl triclosan (MTCS) on polyethylene (PE), polystyrene (PS), and soil was investigated. Results indicate that the more hydrophobic MTCS had much higher sorption capacity and affinity than TCS. Competitive sorption between them occurred in most cases and appeared to be concentration-dependent (in the range of 0.1-5 mg TCS/L and 0.01-≤0.05 mg MTCS/L of primary solutes, respectively): more pronounced at low concentrations of primary solute, while progressively weaker with the increase of concentrations. Among the sorbents, MTCS exhibited strong antagonistic effect on TCS sorption for MPs, especially PS, while significant suppression of MTCS sorption by TCS took place for soil and PS rather than PE. Additionally, it is interesting to observe that the presence of TCS substantially facilitated the sorption of MTCS exclusively at high concentrations on both PS and soil, presumably attributed to the solute-multilayer formation. Furthermore, the magnitude of the two effects varied with solution pH: TCS sorption at alkaline pH was the most suppressed by MTCS because the less hydrophobic dissociated TCS tended to be displaced, and the highest cooperative sorption of MTCS with TCS occurred at acidic pH because neutral TCS preferentially adsorbed on sorbent surface could provide additional sorption sites for MTCS. Both competitive and cooperative effects between multiple contaminants may affect their fate and transport, thereby these findings are helpful for assessing the environmental risk of MPs and TCS in soil.
单种污染物在微塑料（MPs）上的吸附行为已得到广泛研究，但对于包含多种污染物的更实际情况知之甚少。在本研究中，研究了三氯生（TCS）及其主要代谢物甲基三氯生（MTCS）在聚乙烯（PE）、聚苯乙烯（PS）和土壤之间的相互作用。结果表明，疏水性更强的 MTCS 具有比 TCS 更高的吸附容量和亲和力。在大多数情况下，它们之间存在竞争吸附，且似乎与浓度有关（在 0.1-5mg TCS/L 和 0.01-≤0.05mg MTCS/L 的主要溶质范围内）：在低浓度的主要溶质时更为明显，而随着浓度的增加逐渐减弱。在吸附剂中，MTCS 对 MPs 上 TCS 的吸附表现出强烈的拮抗作用，特别是 PS，而 TCS 对 MTCS 的吸附则显著受到抑制，主要发生在土壤和 PS 上，而不是 PE 上。此外，有趣的是观察到 TCS 的存在极大地促进了 MTCS 在 PS 和土壤上的高浓度吸附，可能归因于溶质多层形成。此外，这两种效应的大小随溶液 pH 值而变化：由于疏水性较小的游离 TCS 易于被取代，因此 MTCS 对碱性 pH 值下 TCS 吸附的抑制作用最大，而由于中性 TCS 优先吸附在吸附剂表面上，因此酸性 pH 值下 TCS 与 MTCS 的协同吸附作用最大，可为 MTCS 提供额外的吸附位点。多种污染物之间的竞争和协同效应可能会影响它们的归宿和传输，因此这些发现有助于评估 MPs 和 TCS 在土壤中的环境风险。
