摘要

纳米塑料（NPs）的聚集是理解环境中NP的动态性质的关键问题。 NPs在各种环境条件下的聚集尚未研究。我们研究了无机离子和天然有机物质（NOM）对溶液中聚苯乙烯（PS）NPs聚集的影响。结果表明，PS NPs在NaCl（1-100mM）和CaCl2（0.1-15mM）的宽离子强度溶液中保持稳定，仅在低离子强度的FeCl3溶液（0.01mM）中保持稳定。然而，在FeCl3溶液中观察到明显的PS NPs聚集，离子强度增加（0.1和1mM）。此外，在NaCl和CaCl2溶液的所有离子强度和低离子强度的FeCl3溶液（0.01mM）中，NOM对PS NPs聚集的影响可忽略不计。然而，NOM降低了中间离子强度FeCl3（0.1mM）溶液中的PS NPs聚集，并且在高离子强度的FeCl 3（1mM）溶液中增加了聚集。基于PS NPs之间相互作用力的理论分析，Derjaguin-Landau-Verwey-Overbeek力是在NOM缺席或存在的情况下控制PS NPs聚集的贡献者。此外，其他因素，包括PS NPs表面的静电异质性，NOM诱导的空间排斥，以及在NOM存在下通过桥接效应形成的簇也在选定的条件下导致PS NPs聚集的改变。使用低温扫描电子显微镜直接观察PS NPs-NOM簇。

The aggregation of nanoplastics (NPs) is a key issue in understanding the dynamic nature of NPs in the environment. The aggregation of NPs under various environmental conditions has not yet been studied. We investigated the influences of inorganic ions and natural organic matter (NOM) on polystyrene (PS) NPs aggregation in solutions. Results showed that PS NPs remained stable in wide ionic strength solutions of NaCl (1-100 mM) and CaCl2 (0.1-15 mM), and only in low ionic strength FeCl3 solutions (0.01 mM). However, obvious PS NPs aggregation was observed in FeCl3 solutions with an increase in ionic strength (0.1 and 1 mM). Moreover, NOM had a negligible effect on PS NPs aggregation in all ionic strengths of NaCl and CaCl2 solutions and in low ionic strength FeCl3 solutions (0.01 mM). However, NOM reduced PS NPs aggregation in an intermediate ionic strength FeCl3 (0.1 mM) solution and increased aggregation in a high ionic strength FeCl3 (1 mM) solution. Based on the theoretical analysis of interaction forces among PS NPs, the Derjaguin-Landau-Verwey-Overbeek force was a contributor governing PS NPs aggregation either in the absence or presence of NOM. In addition, other factors, including electrostatic heterogeneity of PS NPs surfaces, steric repulsion induced by NOM, and clusters formed via bridging effect in the presence of NOM also contributed to altered PS NPs aggregation under selected conditions. The PS NPs-NOM clusters were directly observed using a cryogenic scanning electron microscope.

https://www.ncbi.nlm.nih.gov/pubmed/29348047