School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou 510275, PR China; Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, Sun Yat-sen University, Guangzhou 510275, PR China.
School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou 510275, PR China; Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, Sun Yat-sen University, Guangzhou 510275, PR China.
Water Res. 2022 Aug 15;222:118877. doi: 10.1016/j.watres.2022.118877. Epub 2022 Jul 17.
The presence of heavy metals alters the colloidal stability and deposition of nanoplastics (NPs) in urban waters. Such processes are important to assess the mobility and fate of NPs and their associated heavy metals. Up to date, few studies have reported the impact of heavy metals on the colloidal behaviors of NPs and the involved mechanisms. In the study, time-resolved dynamic light scattering (DLS) and quartz crystal microbalance with dissipation (QCM-D) methods were used to assess the aggregation and deposition kinetics of polystyrene nanospheres with divalent heavy metals. For comparison, carboxyl-modified polystyrene nanospheres were used. Results reveal that heavy metals destabilized NPs more significantly than calcium ions. Spectroscopy and transmission electron microscopy analysis propose that heavy metals destabilized NPs via inner-sphere coordination with carboxyl groups and cation-π interactions, further leading to the formation of different dimensional aggregates. QCM-D results suggest that the deposition rate, irreversibility, and film compactness of NPs on silica surfaces first increased but further decreased as heavy metal concentration increased. Such deposition behaviors depended on the bridging effects between NPs and silica and aggregation-induced diffusion limitation. In that case, the destabilization and retention ability of heavy metals for NPs were related to their electronegativity and hydration shell thickness. In urban waters, the presence of natural organic matter (NOM) decreased the destabilization and retention ability of heavy metals, whereas heavy metals with environmentally relevant concentrations still enhanced the aggregation and deposition of NPs compared with other environmental cations. This study highlights the impact of heavy metal property on the colloidal behaviors of NPs, thus deepening our understanding of the mobility and fate of NPs associated with heavy metals in urban waters.
重金属的存在会改变纳米塑料（NPs）在城市水中的胶体稳定性和沉积。这些过程对于评估 NPs 及其相关重金属的迁移和归宿非常重要。迄今为止，很少有研究报道重金属对 NPs 胶体行为的影响及其相关机制。在这项研究中，使用时间分辨动态光散射（DLS）和石英晶体微天平耗散（QCM-D）方法来评估二价重金属与聚苯乙烯纳米球的聚集和沉积动力学。为了进行比较，还使用了羧基改性的聚苯乙烯纳米球。结果表明，重金属比钙离子更能使 NPs 不稳定。光谱和透射电子显微镜分析表明，重金属通过与羧基的内球配位和阳离子-π相互作用使 NPs 失稳，进一步导致不同维度的聚集体的形成。QCM-D 结果表明， NPs 在二氧化硅表面上的沉积速率、不可逆性和膜致密性最初随重金属浓度的增加而增加，但随后又降低。这种沉积行为取决于 NPs 和二氧化硅之间的桥接效应以及聚集诱导的扩散限制。在这种情况下，重金属对 NPs 的失稳和保留能力与其电负性和水合壳厚度有关。在城市水中，天然有机物（NOM）的存在降低了重金属的失稳和保留能力，而具有环境相关性浓度的重金属仍会增强 NPs 的聚集和沉积，与其他环境阳离子相比。这项研究强调了重金属性质对 NPs 胶体行为的影响，从而加深了我们对与重金属相关的 NPs 在城市水中的迁移和归宿的理解。
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