Pirade Februriyana, Foppen Jan Willem, van der Hoek Jan Peter, Lompe Kim Maren
Department of Water Management, Faculty of Civil Engineering and Geosciences, Delft University of Technology, Stevinweg 1, 2628 CN Delft, Netherlands.
Department of Water Management, Faculty of Civil Engineering and Geosciences, Delft University of Technology, Stevinweg 1, 2628 CN Delft, Netherlands.
Environ Pollut. 2025 Feb 1;366:125393. doi: 10.1016/j.envpol.2024.125393. Epub 2024 Nov 23.
The fate and toxicity of nanoplastics (NPs) in the environment is largely determined by their stability. We explored how water composition, nanoplastic size, and surface carboxyl group density influenced the aggregation of polystyrene (PS) NPs in fresh water. Unfunctionalized 200, 300, 500, and 1000 nm PS NPs and 310 nm carboxylated PS NPs with carboxyl group densities of 0.35 and 0.6 mmol g were used to simulate pristine and aged NPs. Natural water matrices tested in this study include synthetic surface water (SSW), water from the Schie canal (Netherlands) and tap water. Suwannee River Natural Organic Matter (SRNOM) was included to mimic organic matter concentrations. In CaCl, we found PS NPs are more stable as their size increases with the increase of the critical coagulation concentration (CCC) from 44 mM to 59 mM and 77 mM for NP sizes of 200 nm, 300 nm and 500 nm. Conversely, 1000 nm PS NPs remained stable even at 100 mM CaCl. Increasing the carboxyl group density decreased the stability of NPs as a result of the interaction between Ca and the carboxyl group. These results were consistent with the mass of Ca adsorbed per mass of NPs. The presence of SRNOM decreased the stability of PS NPs via particle bridging facilitated by SRNOM. However, in SSW, Schie water and tap water with low divalent cation concentrations, the hydrodynamic size of PS NPs did not change, even at prolonged durations up to one week. We concluded that PS NPs are unlikely to aggregate in water with low divalent cation concentrations, like natural freshwater bodies. Ecotoxicologists and water treatment engineers will have to consider treating PS NPs as colloidally stable particles as the lack of aggregation in fresh surface water bodies will affect their ecotoxicity and may pose challenges to their removal in water treatment.
纳米塑料（NPs）在环境中的归宿和毒性很大程度上取决于其稳定性。我们探究了水的成分、纳米塑料尺寸和表面羧基密度如何影响淡水体系中聚苯乙烯（PS）纳米塑料的聚集。使用未功能化的200、300、500和1000纳米的PS纳米塑料以及羧基密度分别为0.35和0.6毫摩尔/克的310纳米羧化PS纳米塑料来模拟原始和老化的纳米塑料。本研究中测试的天然水基质包括合成地表水（SSW）、荷兰斯凯尔特运河的水和自来水。加入了苏万尼河天然有机物（SRNOM）以模拟有机物浓度。在氯化钙溶液中，我们发现随着PS纳米塑料尺寸增大其稳定性增强，对于尺寸为200纳米、300纳米和500纳米的纳米塑料，临界凝聚浓度（CCC）从44毫摩尔增加到59毫摩尔再到77毫摩尔。相反，即使在100毫摩尔氯化钙溶液中，1000纳米的PS纳米塑料仍保持稳定。由于钙与羧基之间的相互作用，羧基密度增加会降低纳米塑料的稳定性。这些结果与每质量纳米塑料吸附的钙质量一致。SRNOM的存在通过SRNOM促进的颗粒桥连作用降低了PS纳米塑料的稳定性。然而，在二价阳离子浓度低的SSW、斯凯尔特河水和自来水中，即使长达一周的长时间放置，PS纳米塑料的流体动力学尺寸也没有变化。我们得出结论，PS纳米塑料在像天然淡水水体这样二价阳离子浓度低的水中不太可能聚集。生态毒理学家和水处理工程师将不得不考虑把PS纳米塑料视为胶体稳定颗粒，因为在新鲜地表水体中缺乏聚集会影响它们的生态毒性，并且可能给其在水处理中的去除带来挑战。
