State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering, Hohai University, Nanjing, China; College of Mechanics and Materials, Hohai University, Nanjing, China.
State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering, Hohai University, Nanjing, China; College of Mechanics and Materials, Hohai University, Nanjing, China.
Environ Res. 2023 Jul 1;228:115871. doi: 10.1016/j.envres.2023.115871. Epub 2023 Apr 11.
Contaminants can co-exist and migrate together in the environment, causing complex (and sometimes unexpected) transport dynamics which challenge the efficient remediation of individual contaminants. The co-transport dynamics, however, remained obscure for some contaminants, such as arsenic and micro/nano-plastics (MNPs). To fill this knowledge gap, this study explored the co-transport dynamics of arsenic and MNP particles in saturated soil by combining laboratory experiments and stochastic model analysis. Isothermal adsorption and sand column transport experiments showed that the adsorption of arsenic by MNP particles followed the Freundlich model, with a maximum adsorption of 2.425 mg/g for the MNP particles with a diameter of 100 nm. In the presence of MNP particles, the efflux concentration of arsenic ions declined due to adsorption, where the decline rate decreased with the increasing MNP size and increased with the increasing adsorption capacity. Experimental results also showed that the 100 nm nano-plastic particles prohibited arsenic transport in saturated sand columns, while the 5 μm microplastics enhanced arsenic transport due to electrostatic adsorption and media pore plugging. A tempered time fractional advective-dispersion equation was then proposed to quantify the observed breakthrough curves of arsenic. The results showed that this model can reliably capture the co-transport behavior of arsenic with MNPs in the saturated soil with all coefficients of determination over 0.97, and particularly, the small MNP particles facilitated anomalous transport of arsenic. This study therefore improved the understanding and quantification of the co-transport of arsenic and MNPs in soil.
污染物可以在环境中共存并一起迁移，导致复杂（有时是意外的）的传输动力学，这给单个污染物的有效修复带来了挑战。然而，对于一些污染物，如砷和微/纳米塑料（MNPs），其共迁移动力学仍然不清楚。为了填补这一知识空白，本研究通过结合实验室实验和随机模型分析，探讨了砷和 MNP 颗粒在饱和土壤中的共迁移动力学。等温吸附和砂柱运移实验表明，MNP 颗粒对砷的吸附符合 Freundlich 模型，对于直径为 100nm 的 MNP 颗粒，最大吸附量为 2.425mg/g。在 MNP 颗粒存在的情况下，由于吸附作用，砷离子的流出浓度下降，下降速率随着 MNP 尺寸的增加而减小，随着吸附容量的增加而增加。实验结果还表明，100nm 的纳米塑料颗粒阻止了砷在饱和砂柱中的运移，而 5μm 的微塑料由于静电吸附和介质孔隙堵塞而增强了砷的运移。随后提出了一个修正的时间分数对流-弥散方程来量化观察到的砷的穿透曲线。结果表明，该模型可以可靠地捕捉砷与 MNPs 在饱和土壤中的共输运行为，所有决定系数均超过 0.97，特别是小 MNP 颗粒促进了砷的异常输运。因此，本研究提高了对砷和 MNPs 在土壤中共输运的理解和量化。
