废水中存在的二氧化钛纳米颗粒(TiO2-NP)被排放到淡水和盐水中(即,海洋)系统。TiO2-NP可以通过产生包括羟基自由基(·OH)的活性氧的紫外线(UV)光活化太阳能驱动。·OH是非选择性的,并且与水中的多种物质反应。在其他研究中,TiO2-NP的光活化与氧化应激和对动植物生物群的生态毒理学影响有关。这项研究检查了淡水和盐水系统中TiO2-NP的光活化,并使用亚甲基蓝(MB)作为反应探针对比了两个系统中的氧化电位。最大MB损失(51.9%,n=4;95%置信区间49.4-54.5)在无盐条件下测量,去离子水,其中·OH清除是可忽略的;最小的MB损失(1%)在盐水中测量,由于显著的·OH清除,表明MB损失与自由基清除之间的负相关。海水成分清除的动力学分析表明,由于高浓度和高反应速率常数,Cl-的影响最大。相对于海水中存在的其他侵蚀性较小的清除剂,在存在Br-的情况下发生了MB的显着损失(即,HCO3-,HSO4-).这一结果与溴酸盐的形成是一致的,随后与MB反应的强氧化剂。在从俄克拉荷马州不同水体收集的淡水样本中(n=12),平均MB损失为13.4%。相对于海洋系统,淡水系统中的MB损失更大,这是由于各种水质参数对·OH的清除作用较低。总的来说,淡水系统中的TiO2-NP光活化有可能引起更大的氧化应激和生态毒理学影响,而海洋系统中的·OH清除是主要反应。
Titanium dioxide nanoparticles (TiO2-NP) present in wastewater effluent are discharged into freshwater and saltwater (i.e., marine) systems. TiO2-NP can be solar-driven photoactivated by ultraviolet (UV)-light producing reactive oxygen species including hydroxyl radicals (·OH). ·OH are non-selective and react with a broad range of species in water. In other studies,
photoactivation of TiO2-NP has been correlated with oxidative stress and ecotoxicological impacts on plant and animal biota. This study examined the
photoactivation of TiO2-NP in freshwater and saltwater systems, and contrasted the oxidation potential in both systems using methylene blue (MB) as a reaction probe. Maximum MB loss (51.9%, n = 4; 95% confidence interval 49.4-54.5) was measured in salt-free, deionized water where ·OH scavenging was negligible; minimum MB loss (1%) was measured in saltwater due to significant ·OH scavenging, indicating the inverse correlation between MB loss and radical scavenging. A kinetic analysis of scavenging by seawater constituents indicated Cl- had the greatest impact due to high concentration and high reaction rate constant. Significant loss of MB occurred in the presence of Br- relative to other less aggressive scavengers present in seawater (i.e., HCO3-, HSO4-). This result is consistent with the formation of Bromate, a strong oxidant that subsequently reacts with MB. In freshwater samples collected from different water bodies in Oklahoma (n = 12), the average MB loss was 13.4%. Greater MB loss in freshwater systems relative to marine systems was due to lower ·OH scavenging by various water quality parameters. Overall, TiO2-NP
photoactivation in freshwater systems has the potential to cause greater oxidative stress and ecotoxicological impacts than in marine systems where ·OH scavenging is a dominant reaction.