Tina Yan

With theincreasing applications of carbon nanotubes (CNTs) worldwide, considerableconcerns have been raised regarding their inevitable releases into naturalwaters and ecotoxicity. It was supposed that CNTs may interact with someexisting pollutants like zinc in aquatic systems and exhibit different effectswhen compared with their single treatments. However, data on their possiblecombined toxicity on aquatic species are still lacking. Moreover, the interactionsof Zn with different functionalized CNTs, may be distinct and thereby lead todiverse results. It is like that functional groups play a vital role inillustrating the differences in toxicity among various CNTs. In this study, thesingle and joint effects of multi-walled carbon nanotubes (MWCNTs) and twoMWCNTs functionalized with carboxylation (COOH-MWCNTs) or hydroxylation(OH-MWCNTs) in the absence or presence of zinc (Zn) on antioxidant status andhistopathological changes in Carassius auratus were evaluated. Synergisticeffect was tentatively proposed for joint-toxicity action, which was supportedby apparently observed oxidative stress and histopathological changes in jointexposure groups. The integrated biomarker response index was calculated to rankthe toxicity order, from which the conclusion of synergistic effect wasstrengthened. Regarding differences among various CNTs, our data showed thatOH-MWCNTs and COOH-MWCNTs were more stressful to fish than raw MWCNTs. Thisfinding sustained that functionalization is an important factor innanotoxicity, which may serve as clues for future design and application ofCNTs. Overall, these results provided some valuable toxicological data on thejoint effects of CNTs and heavy metals on aquatic species, which can facilitatefurther understanding on the potential impacts of other coexisting pollutantsin the culture of freshwater fish.

As one of thefirst generation of fluoroquinolone antibiotics, flumequine (FLU) has beendetected ubiquitously in surfacewaters and municipalwastewaters. In light ofFLU's possible adverse effects on aquatic species, the removal of thisantibiotic has received worldwide attention. In this study, the kinetics,transformation products,mechanisms and toxicity variations of the ozonationprocess for FLU were systematically determined. The possible effects ofsolution pH, addition of inorganic ions, dissolved organic matter, andtert-butyl-alcohol (a radical scavenger), as well as the type of water matriceson FLU removal by ozonation, were studied from the perspective of thedegradation kinetics. The data obtained suggested that ozone can be used as aneffective oxidant for the fast removal of FLU from natural waters. Using liquidchromatography-mass spectrometry, a total of thirteen transformation products ofFLU during ozonation were identified, and their specific reaction mechanismswere also proposed. The degradation pathways involving the hydroxylation,decarboxylation and defluorination were tentatively proposed. Meanwhile, thegeneration of three low-molecular-weight carboxylic acids was also observed. Inaddition, the potential toxicity of the transformationmixtures of FLU byozonewas evaluated. Overall, this paper can be a unique contribution to thesystematic elucidation of the ozonation process of this antibiotic in water.

Perfluorooctanesulfonate (PFOS) and zinc have been detected in aquatic environment widely. Inorder to study the combined effects of PFOS and Zn, a series of experiments wasconducted to explore the acute mortality, bioaccumulation and antioxidantstatus of Limnodrilus hoffmeisteri. The acute toxicity was evaluated bycalculating 24 h-EC50 values, and it was observed that 24 h-EC50 values insingle and joint treatments decreased with decreasing pH value or increasingexposure concentration. Toxic unit analysis suggested that the combined effectsof the PFOS + Zn binary mixture were mostly simple addition, with 8 groupsshowing synergism and only one group showing antagonism. The analysis ofinternal Zn and PFOS concentration showed that the possible interaction betweenZn and PFOS can affect the bioaccumulation of the two chemicals in L.hoffmeisteri. In addition, oxidative stress status was assessed by measuring oxidation-relatedbiochemical parameters such as superoxide dismutase, glutathione peroxidase andmalondialdehyde, and the integrated biomarker response index was estimated torank the toxicity order. Exposures to Zn and PFOS were found to evoke somechanges in the antioxidant defense system, and a strong self-adaptive abilitywas noticed for L. hoffmeisteri after 10 d exposure