Guangdong Provincial Engineering Research Center of Public Health Detection and Assessment, School of Public Health, Guangdong Pharmaceutical University, Guangzhou 510310, China; State Key Laboratory of Ore Deposit Geochemistry, Research Center of Ecological Environment and Resource Utilization, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China.
State Key Laboratory of Ore Deposit Geochemistry, Research Center of Ecological Environment and Resource Utilization, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China.
Ecotoxicol Environ Saf. 2024 Jul 15;280:116533. doi: 10.1016/j.ecoenv.2024.116533. Epub 2024 Jun 7.
The widespread utilization of plastic products ineluctably leads to the ubiquity of nanoplastics (NPs), causing potential risks for aquatic environments. Interactions of NPs with mineral surfaces may affect NPs transport, fate and ecotoxicity. This study aims to investigate systematically the deposition and aggregation behaviors of carboxylated polystyrene nanoplastics (COOH-PSNPs) by four types of clay minerals (illite, kaolinite, Na-montmorillonite, and Ca-montmorillonite) under various solution chemistry conditions (pH, temperature, ionic strength and type). Results demonstrate that the deposition process was dominated by electrostatic interactions. Divalent cations (i.e., Ca, Mg, Cd, or Pb) were more efficient for screening surface negative charges and compressing the electrical double layer (EDL). Hence, there were significant increases in deposition rates of COOH-PSNPs with clay minerals in suspension containing divalent cations, whereas only slight increases in deposition rates of COOH-PSNPs were observed in monovalent cations (Na, K). Negligible deposition occurred in the presence of anions (F, Cl, NO, CO, SO, or PO). Divalent Ca could incrementally facilitate the deposition of COOH-PSNPs through Ca-assisted bridging with increasing CaCl concentrations (0-100 mM). The weakened deposition of COOH-PSNPs with increasing pH (2.0-10.0) was primarily attributed to the reduce in positive charge density at the edges of clay minerals. In suspensions containing 2 mM CaCl, increased Na ionic strength (0-100 mM) and temperature (15-55 C) also favored the deposition of COOH-PSNPs. The ability of COOH-PSNPs deposited by four types of clay minerals followed the sequence of kaolinite > Na-montmorillonite > Ca-montmorillonite > illite, which was related to their structural and surface charge properties. This study revealed the deposition behaviors and mechanisms between NPs and clay minerals under environmentally representative conditions, which provided novel insights into the transport and fate of NPs in natural aquatic environments.
塑料制品的广泛应用不可避免地导致了纳米塑料（NPs）的普遍存在，对水生环境造成了潜在的风险。NPs 与矿物表面的相互作用可能会影响 NPs 的迁移、归宿和生态毒性。本研究旨在系统研究在不同溶液化学条件（pH 值、温度、离子强度和类型）下，四种粘土矿物（伊利石、高岭石、钠蒙脱石和钙蒙脱石）对羧基化聚苯乙烯纳米塑料（COOH-PSNPs）的沉积和聚集行为。结果表明，沉积过程主要受静电相互作用控制。二价阳离子（如 Ca、Mg、Cd 或 Pb）更有效地屏蔽表面负电荷并压缩双电层（EDL）。因此，在含有二价阳离子的悬浮液中，COOH-PSNPs 与粘土矿物的沉积速率显著增加，而在单价阳离子（Na、K）中，COOH-PSNPs 的沉积速率仅略有增加。在阴离子（F、Cl、NO、CO、SO 或 PO）存在下，几乎没有沉积发生。二价 Ca 可以通过 CaCl 浓度（0-100mM）的增加来促进 COOH-PSNPs 的逐步沉积，从而促进 Ca 辅助桥接。随着 pH 值（2.0-10.0）的升高，COO-PSNPs 的沉积减弱，主要归因于粘土矿物边缘正电荷密度的降低。在含有 2mM CaCl 的悬浮液中，增加的 Na 离子强度（0-100mM）和温度（15-55°C）也有利于 COOH-PSNPs 的沉积。四种粘土矿物沉积的 COOH-PSNPs 能力顺序为高岭石>钠蒙脱石>钙蒙脱石>伊利石，这与它们的结构和表面电荷特性有关。本研究揭示了在具有代表性的环境条件下 NPs 与粘土矿物之间的沉积行为和机制，为 NPs 在自然水生环境中的迁移和归宿提供了新的见解。
