Due to their widespread use, silver (Ag) and titanium dioxide (TiO2) nanoparticles (NPs) are commonly discharged into aquatic environments via wastewater treatment plants. The study was aimed to assess the effects of wastewater-borne AgNPs (NM-300 K; 15.5 ± 2.4 nm; 25-125 μg L-1) and TiO2NPs (NM-105; 23.1 ± 6.2 nm; 12.5-100 μg L-1), from a laboratory-scale wastewater treatment plant, on Daphnia magna, at individual and subcellular level. For effect comparison, animals were also exposed to ASTM-dispersed NPs at the same nominal concentrations. The behaviour of D. magna was evaluated through monitoring of swimming height and allocation time for preferred zones after 0 h and 96 h of exposure. Biochemical markers of neurotransmission, anaerobic metabolism, biotransformation, and oxidative stress were subsequently determined. No 96-h EC50 (immobilization ≤ 4 %) could be obtained with wastewater-borne NPs and ASTM-dispersed TiO2NPs, whereas the ASTM-dispersed AgNPs resulted in an immobilization 96-h EC50 of 113.8 μg L-1. However, both wastewater-borne and ASTM-dispersed TiO2NPs, at 12.5 μg L-1, caused immediate (0 h) alterations on the swimming height. Allocation time analyses showed that animals exposed to ASTM-dispersed AgNPs spent more time on the surface and bottom at 0 h, and in the middle and bottom at 96 h. This pattern was not observed with ASTM-dispersed TiO2NPs nor with wastewater-borne AgNPs and wastewater-borne TiO2NPs. At the biochemical level, the more pronounced effects were observed with wastewater-borne AgNPs (e.g. induction of lactate dehydrogenase and glutathione S-transferase activities, and inhibition of catalase activity). This integrative approach showed that: (i) the behavioural and biochemical response-patterns were distinct in D. magna exposed to environmentally relevant concentrations of wastewater-borne and ASTM-dispersed NPs; (ii) the most pronounced effects on allocation time were induced by ASTM-dispersed AgNPs; and (iii) at the subcellular level, wastewater-borne AgNPs were more toxic than wastewater-borne TiO2NPs. This study highlights the need for the assessment of the effects of wastewater-borne NPs under realistic exposure scenarios, since processes in wastewater treatment plants may influence their toxicity.

中文翻译：

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废水中的银和二氧化钛纳米颗粒对水蚤的游泳行为和生化标志物的影响：一种综合方法。

由于它们的广泛使用，银（Ag）和二氧化钛（TiO2）纳米颗粒（NPs）通常通过废水处理厂排放到水生环境中。该研究旨在评估废水中的AgNPs（NM-300 K; 15.5±2.4 nm; 25-125μgL-1）和TiO2NPs（NM-105; 23.1±6.2 nm; 12.5-100μgL-）的影响。 1）来自大型蚤（Daphnia magna）上实验室规模的废水处理厂，在个体和亚细胞水平上。为了进行效果比较，动物还以相同的标称浓度暴露于ASTM分散的NP。通过监测0和96小时暴露后首选区域的游泳高度和分配时间，来评估D. magna的行为。随后确定了神经传递，厌氧代谢，生物转化和氧化应激的生化标志物。废水中的NPs和ASTM分散的TiO2NPs不能获得96h EC50（固定化≤4％），而ASTM分散的AgNPs的固定化96h EC50为113.8μgL-1。但是，废水中和ASTM分散的TiO2NPs浓度为12.5μgL-1时，都导致游泳高度立即（0 h）改变。分配时间分析表明，暴露于ASTM分散的AgNPs的动物在0小时的表面和底部以及在96小时的中部和底部花费更多的时间。使用ASTM分散的TiO2NP或废水中的AgNP和废水中的TiO2NP都没有观察到这种模式。在生化水平上，废水中的AgNPs产生了更明显的影响（例如，乳酸脱氢酶和谷胱甘肽S-转移酶活性的诱导，以及过氧化氢酶活性的抑制）。这种综合方法表明：（i）D. magna在暴露于环境相关浓度的废水中和ASTM分散的NPs的行为和生化反应模式是不同的；（ii）分配时间最明显的影响是由ASTM分散的AgNP引起的；（iii）在亚细胞水平上，废水中的AgNP比废水中的TiO2NP具有更高的毒性。由于废水处理厂的过程可能会影响其毒性，因此本研究强调了在实际暴露情况下需要评估废水中NP的影响的必要性。（ii）分配时间最明显的影响是由ASTM分散的AgNP引起的；（iii）在亚细胞水平上，废水中的AgNP比废水中的TiO2NP具有更高的毒性。由于废水处理厂的过程可能会影响其毒性，因此本研究强调了在实际暴露情况下需要评估废水中NP的影响的必要性。（ii）分配时间最明显的影响是由ASTM分散的AgNP引起的；（iii）在亚细胞水平上，废水中的AgNP比废水中的TiO2NP具有更高的毒性。由于废水处理厂的过程可能会影响其毒性，因此本研究强调了在实际暴露情况下需要评估废水中NP的影响的必要性。