Effects of benzophenone-3 and its metabolites on the marine diatom Chaetoceros neogracilis: Underlying mechanisms and environmental implications.

The wide application of benzophenones (BPs), such as benzophenone-3 (BP3), as an ingredient in sunscreens, cosmetics, coatings, and plastics, has led to their global contamination in aquatic environments. Using the marine diatom Chaetoceros neogracilis as a model, this study assessed the toxic effects and mechanisms of BP3 and its two major metabolites (BP8 and BP1). The results showed that BP3 exhibited higher toxicity on C. neogracilis than BP8 and BP1, with their 72-h median effective concentrations being 0.4, 0.8 and 4 mg/L, respectively. Photosynthesis efficiencies were significantly reduced after exposure to environmentally relevant concentrations of the three benzophenones, while cell viability, membrane integrity, membrane potential, and metabolic activities could be further impaired at their higher concentrations. Comparative transcriptomic analysis, followed by gene ontology and KEGG pathway enrichment analyses unraveled that all the three tested benzophenones disrupted photosynthesis and nitrogen metabolism of the diatom through alteration of similar pathways. The toxic effect of BP3 was also attributable to its unique inhibitory effects on eukaryotic ribosome biosynthesis and DNA replication. Taken together, our findings underscore that benzophenones may pose a significant threat to photosynthesis, oxygen production, primary productivity, carbon fixation, and the nitrogen cycle of diatom in coastal waters worldwide.

Interactive effects of temperature and salinity on toxicity of zinc oxide nanoparticles towards the marine mussel Xenostrobus securis.

Growing application of zinc oxide nanoparticles (ZnO-NPs) in global market has led to the concern over their potential environmental impacts. Filter feeders like mussels are prone to nanoparticles due to their superior filter-feeding ability. Temperature and salinity of coastal and estuarine seawaters often vary seasonally and spatially, and their changes may jointly influence physicochemical properties of ZnO-NPs and thus their toxicity. This study, therefore, aimed to investigate the interactive effect of temperatures (15, 25 and 30 °C) and salinities (12 and 32 PSU) on physicochemical properties and sublethal toxicity of ZnO-NPs towards a marine mussel Xenostrobus securis, and to compare that with the toxicity caused by Zn2+ ions (zinc sulphate heptahydrate). The results revealed increased particle agglomeration but decreased zinc ion release of ZnO-NPs at the highest temperature and salinity condition (30 °C and 32 PSU). After exposure, ZnO-NPs significantly reduced survival, byssal attachment rate and filtration rate of the mussels at high temperature and salinity (30 °C and 32 PSU). Glutathione S-transferase and superoxide dismutase activities in the mussels were suppressed at 30 °C. These aligned with the augmented zinc accumulation with increasing temperature and salinity which could likely be attributable to increased particle agglomeration of ZnO-NP and enhanced intrinsic filtration rate of the mussels under these conditions. Together with the observed lower toxic potency of Zn2+ compared to ZnO-NPs, our results suggested that the mussels might accumulate more zinc through particle filtration under higher temperature and salinity, eventually resulting in elevated toxicity of ZnO-NPs. Overall, this study demonstrated the necessity to consider the interactive effect of environmental factors such as temperature and salinity during the toxicity assessment of nanoparticles.

Joint effects of temperature and copper exposure on developmental and gene-expression responses of the marine copepod Tigriopus japonicus.

There is growing contamination of copper (Cu) in the marine environment, particularly after the ban of organotin compounds and the increase of the use of Cu-based antifouling paints. Although there are increasing research interests in temperature-dependent chemical toxicity to aquatic organisms, most existing studies focused on acute impacts of chemicals at high concentrations. This study aimed to investigate the interacting effect of temperature and copper exposure at environmentally relevant concentrations on survival and development in the marine copepod Tigriopus japonicus with a partial life-cycle toxicity test. Expressions of five stress response genes in the copepod, namely two glutathione S-transferases (GST-S and GST-O), two heat shock proteins (HSP70 and HSP90), and glutathione reductase (GR) were also investigated. The copepod's survival was significantly impaired at 15 °C after development to adult stage, while its developmental time reduced significantly with increasing temperature. Copper at the two environmentally relevant test concentrations had no significant impacts on these apical endpoints whereas the interaction between Cu and temperature was more significant in modulating gene expressions. GST-S, GST-O and HSP90 genes in copepods exposed to 100 µg Cu L-1 were significantly upregulated at 20 °C. At 32 °C, most genes were either insignificantly expressed or down-regulated, compared to the control, likely suggesting that thermal stress inhibited the copepod's antioxidative defense system. Overall, the results revealed that the joint Cu and thermal stresses have significantly elicited antioxidative system in the copepods. It clearly demonstrated the need for more fundamental studies about potential impacts of different environmental factors such as temperature on chemical toxicity under realistic scenario of marine pollution.

Contrasting toxicity of polystyrene nanoplastics to the rotifer Brachionus koreanus in the presence of zinc oxide nanoparticles and zinc ions.

Emerging contaminants such as nanoplastics and nanoparticles likely experience similar environmental behaviours, fate and effects but our knowledge of their combined toxicity is scanty. This study, therefore, investigated the joint toxicity of polystyrene nanoplastics (PNPs) and zinc oxide nanoparticles (ZnO-NPs) to an ecologically important rotifer Brachionus koreanus, and compared with the joint toxicity of PNPs and Zn ions (Zn-IONs from ZnSO4·7H2O). With increasing concentration, ZnO-NPs formed significant agglomeration with PNPs for up to 1.3 times of the original hydrodynamic size of ZnO-NPs, alongside doubling in their sedimentation and thereby losing 58% of their released Zn ions. In contrast, the availability of Zn-IONs was less affected by the agglomeration and sedimentation of PNPs, with only a loss of 18% of Zn ions at the highest concentration of PNPs. Consequently, as suggested by Concentration Addition and Independent Action models and the Model Deviation Ratios, ZnO-NPs and PNPs exerted an antagonistic interaction whereas Zn-IONs and PNPs exhibited an additive effect. We also advocate the use of the Nonparametric Response Surface method, which is more useful to predict the toxicity of chemical mixtures with interacting effects. Our findings suggested a potential difference between particle-particle and particle-ion interactions, especially at higher test concentrations, which may eventually affect their toxicity. We, therefore, call for a more systematic evaluation of commonly coexisting chemical mixtures which consist of nanoplastics and manufactured nanomaterials.

Spatiotemporal variations of retinoic acids and their metabolites in the marine environment of Hong Kong.

Excessive intake of retinoic acids (RAs) and the oxidative metabolites, 4-oxo-RAs, can lead to abnormal morphological development in animals. This study investigated spatiotemporal variations of concentrations and compositions of these compounds in Hong Kong's seawater and during algal blooms. Total concentrations of the studied compounds in seawater were up to 0.790 and 0.427 ng/L in dry and wet seasons, respectively, though no significant seasonal variation was observed. Spatially, the Deep Bay Water Control Zone was the most enriched area with the studied compounds owing to its semi-enclosed nature and influence from the Pearl River discharge. During algal blooms, the studied compounds were detected up to 4.74 ng/L. Based on calculated risk quotients, the ecological risk of the studied compounds to Hong Kong's marine ecosystems was low. Nevertheless, the occurrence and distribution of these chemicals in the marine environment should be closely monitored where algal blooms frequently occur.

Extreme cold or warm events can potentially exacerbate chemical toxicity to the marine medaka fish Oryzias melastigma.

Marine ecosystems are currently subjected to dual stresses of chemical pollution and climate change. Through a series of laboratory experiments, this study investigated the impact of exposure to chemical contaminant such as DDT or copper (Cu), in combination with cold or warm temperature extremes on the marine medaka fish Oryzias melastigma. The results showed that extreme seawater temperatures (i.e., 15 and 32 °C in sub-tropical Hong Kong) exacerbated adverse chemical impacts on the growth performance of O. melastigma, in particular at the high thermal extreme. This was likely associated with an interruption of oxygen consumption and aerobic scope. Most importantly, the results of acclimation experiments, as reflected by thermal tolerance polygons, showed that chemical exposure substantially narrowed the thermal tolerance of the medaka, making them more vulnerable to temperature changes and extreme thermal events. Under dual stresses of thermal extremes and chemical exposure, the medaka switched their metabolic pathway to anaerobic respiration that might deplete their energy reserve for chemical detoxification. Although stress proteins such as heat shock proteins (HSP90) were up-regulated for cellular protection in the fish, such a defensive mechanism was repressed with intensifying dual stresses at high temperature and high chemical concentration. Bioconcentration of DDT or Cu generally increased with increasing temperature and its exposure concentration. Overall, these complex chemical-temperature interactions concomitantly exerted a concerted adverse impact to O. melastigma. The temperature-dependent toxicity of DDT or Cu shown in this study clearly demonstrated the potential challenge brought by the risk of chemical pollution under the impact of global climate change.

Concentration-response of six marine species to all-trans-retinoic acid and its ecological risk to the marine environment.

Being a class of vitamin A's main derivatives, retinoic acids (RAs) are important to animals' growth and development. Previous studies demonstrated that exposure of excessive amounts of RAs would lead to malformation and abnormal development in aquatic animals such as amphibians and fishes. Currently, there are only limited toxicity data of RAs available for freshwater species, while those for marine species are seriously lacking. This study aimed to fill such data gap by conducting toxicity tests on six marine species (i.e., one microalga, four invertebrates and one fish) towards the exposure to all-trans-RA (at-RA), which is the most widely distributed RA in the environment. Results showed that the embryo of medaka fish Oryzias melastigma was the most sensitive towards the exposure of at-RA while the gastropod Monodonta labio was the least sensitive. A species sensitivity distribution (SSD) was constructed based on the experimental results generated from the present study. An interim marine-specific predicted no-effect concentration (PNEC) of at-RA was derived at 2300 ng/L. By computing the hazard quotients using the interim marine-specific PNEC and available measured and predicted concentrations of RAs, we found the current levels of RAs posed no immediate risks to the marine environment of Hong Kong. The interim marine-specific PNEC was more than 500-fold of freshwater-specific PNEC (i.e., 3.93 ng/L), indicating that marine species were generally less sensitive than their freshwater counterparts towards RAs. This was the first study to document the concentration-response of various marine species towards at-RA exposure and construct the marine-specific SSD for assessing the ecological risk of at-RA towards the marine environment. Since various forms of RAs and their metabolites often coexist in aquatic environments, further studies should investigate their combined toxicity to an array of marine species of different trophic levels with consideration of chronic exposure scenarios.

Hydrophobic Surface Coating Can Reduce Toxicity of Zinc Oxide Nanoparticles to the Marine Copepod Tigriopus japonicus.

Coated zinc oxide nanoparticles (ZnO-NPs) are more commonly applied in commercial products but current risk assessments mostly focus on bare ZnO-NPs. To investigate the impacts of surface coatings, this study examined acute and chronic toxicities of six chemicals, including bare ZnO-NPs, ZnO-NPs with three silane coatings of different hydrophobicity, zinc oxide bulk particles (ZnO-BKs), and zinc ions (Zn-IONs), toward a marine copepod, Tigriopus japonicus. In acute tests, bare ZnO-NPs and hydrophobic ZnO-NPs were less toxic than hydrophilic ZnO-NPs. Analyses of the copepod's antioxidant gene expression suggested that such differences were governed by hydrodynamic size and ion dissolution of the particles, which affected zinc bioaccumulation in copepods. Conversely, all test particles, except the least toxic hydrophobic ZnO-NPs, shared similar chronic toxicity as Zn-IONs because they mostly dissolved into zinc ions at low test concentrations. The metadata analysis, together with our test results, further suggested that the toxicity of coated metal-associated nanoparticles could be predicted by the hydrophobicity and density of their surface coatings. This study evidenced the influence of surface coatings on the physicochemical properties, toxicity, and toxic mechanisms of ZnO-NPs and provided insights into the toxicity prediction of coated nanoparticles from their coating properties to improve their future risk assessment and management.

Occurrence of retinoic acids and their metabolites in sewage and their removal efficiencies by chemically enhanced primary treatment and secondary biological treatment.

Sewage treatment plants (STPs) are important in densely populated megacities like Hong Kong to control the release of harmful pollutants from households and industries into the receiving water bodies and maintain water quality for supporting various beneficial uses. This study investigated the occurrence of the teratogenic retinoic acids (RAs) and their oxidative metabolites in sewage and sludge of six selected STPs that treat about 87% of all sewage in Hong Kong annually, and compared the removal efficiencies of these compounds from sewage between two major sewage treatment processes, i.e., chemically enhanced primary treatment (CEPT) and secondary (biological) treatment. The total concentrations of the studied RAs in influent, effluent and sludge from the six selected STPs were found between 21.5 and 33.1 ng/L, 12.0-20.4 ng/L, and 4.33-7.02 ng/g dry weight, respectively. The compounds were dominated by all-trans-RA and 13-cis-RA, together accounting for 46.9-65.6%, 38.4-56.7%, and 62.8-82.8% of the total RAs in influent, effluent and sludge, respectively. The studied RAs could not be satisfactorily removed by both treatment processes with removal efficiencies ranging from 25.4% to 47.4% only, without significant difference in their removal between CEPT and secondary treatment. Based on the calculated hazard quotients of all-trans-RA equivalents (0.248-0.521), the treated effluents from all the six STPs exhibited medium ecological risks to the receiving coastal environment. Therefore, continuous monitoring of these compounds and enhancement of treatment technologies of STPs shall be considered in the future to improve the removal efficiencies of these compounds.

Chronic oral administration of adipoRon reverses cognitive impairments and ameliorates neuropathology in an Alzheimer's disease mouse model.

Circulating adiponectin (APN) levels decrease with age and obesity. On the other hand, a reduction in APN levels is associated with neurodegeneration and neuroinflammation. We previously showed that aged adiponectin knockout (APN-/-) mice developed Alzheimer's like pathologies, cerebral insulin resistance, and cognitive impairments. More recently, we also demonstrated that APN deficiency increased Aß-induced microglia activation and neuroinflammatory responses in 5xFAD mice. There is compelling evidence that deregulated insulin activities or cerebral insulin resistance contributes to neuroinflammation and Alzheimer's disease (AD) pathogenesis. Here, we demonstrated that APN levels were reduced in the brain of AD patients and 5xFAD mice. We crossbred 5xFAD mice with APN-/- mice to generate APN-deficient 5xFAD (5xFAD;APN-/-). APN deficiency in 5xFAD mice accelerated amyloid loading, increased cerebral amyloid angiopathy, and reduced insulin-signaling activities. Pharmacokinetics study demonstrated adipoRon (APN receptor agonist) was a blood-brain barrier penetrant. AdipoRon improved neuronal insulin-signaling activities and insulin sensitivity in vitro and in vivo. Chronic adipoRon treatment improved spatial memory functions and significantly rescued neuronal and synaptic loss in 5xFAD and 5xFAD;APN-/- mice. AdipoRon lowered plaque and Aß levels in AD mice. AdipoRon also exerted anti-inflammatory effects by reducing microglial and astrocytes activation as well as suppressing cerebral cytokines levels. The microglial phagocytic activity toward Aß was restored after adipoRon treatment. Our results indicated that adipoRon exerts multiple beneficial effects providing important therapeutic implications. We propose chronic adipoRon administration as a potential treatment for AD.

Tissue distribution of triphenyltin compounds in marine teleost fishes.

Continuous release of the highly toxic triphenyltin compounds (TPT) from antifouling paints and fungicides has caused serious pollution to urbanized coastal marine environments worldwide since the 1960s. Using gas-chromatography mass-spectrometry (GC-MS), this study investigated the distribution profile of TPT in 15 types of tissues of four marine teleost fish species collected from Hong Kong waters. Concentrations of TPT in various tissues had a significant positive correlation with protein contents in the tissues (r = 0.346, p < 0.001) and, to a lesser extent with lipid contents (r = 0.169, p = 0.020). Highest concentrations of TPT were consistently found in liver, ranging from 1074.9 to 3443.7 ng/g wet weight; whereas fish scales always contained the least concentration of TPT in all species, ranging from 10.4 to 48.5 ng/g wet weight. Through mass balance models and regression analyses, muscle tissues were found to contribute most to the total TPT body burden, and the average TPT concentration of both dorsal and ventral muscles was identified as the best predictor for estimating TPT burden in the entire fish. Hence, further investigations of bioaccumulation and biomagnification of TPT in fishes should adopt this modelling approach in estimating its total body burden in individual fish.

Long-term impact of accidental pollution on the distribution and risks of metals and metalloids in the sediment of the Longjiang River, China.

In January 2012, a serious accident polluted the Longjiang River with high concentrations of cadmium (Cd) and other concomitant metals and metalloids in the water. After emergency treatment (i.e., the addition of coagulants), these metals and metalloids were transferred from the water into the sediment through precipitation of the flocculent materials produced. In this study, the long-term distribution of six metals and metalloids in the sediment of the Longjiang River was investigated and their ecological risks were assessed. Approximately 1 year after the accident (i.e., late 2012), the average Cd content in the sediment of the affected sites decreased to 25.6 ± 19.5 mg/kg, which was 8 times higher than that of 3.16 ± 3.18 mg/kg in the upstream reference sites. In 2016 and 2017, the average Cd content in the sediment of the affected sites further decreased to 4.91 ± 2.23 and 6.27 ± 4.27 mg/kg, respectively. Compared with late 2012, the amounts of Zn, Pb, and Cu obviously decreased in 2016 and 2017, whereas there were no obvious differences in the As and Hg amounts during 3 years considered. Among metals and metalloids, the average contribution of Cd to the potential ecological risk index (RI) was 90%, 69%, and 70% in the affected areas in 2012, 2016, and 2017, respectively, suggesting that Cd was the most important factor affecting the ecological risk of metals in the Longjiang River. It should be noted that the average contribution of Hg to RI in the affected areas increased from 8% in 2012 to 25% and 23% in 2016 and 2017, respectively. The sequence of contribution of six elements was Cd > Hg > As>Pb > Cu ≈ Zn. A high ecological risk of metals and metalloids was found in the sediments of two reservoirs, probably owing to the barrier effect of the dam. This study will be useful for the environmental management of rivers affected by accidental pollution of metals and metalloids.

Acute and chronic toxicity of nickel on freshwater and marine tropical aquatic organisms.

Water quality guidelines and ecological risk assessment of chemical substances like nickel (Ni) in tropical regions such as South East Asia and Melanesia are often based on temperate information as a result of fewer Ni ecotoxicity data available for tropical species. This leaves an unknown margin of uncertainty in the risk assessment in the tropics. In order to fill this data gap, this study was designed to conduct standard toxicity tests on Ni with two freshwater species (acute tests) and three marine species (acute and chronic tests) originated from tropical Hong Kong. All tests were carried out using measured concentrations of Ni with control mortality below 15%. The median lethal concentrations (LC50s) were determined as 2520 (95% confidence interval: 2210, 2860) and 426 (351, 515) µg Ni L-1 for the freshwater gastropods Pomacea lineata (48 h) and Sulcospira hainanensis (96 h), respectively, while 96 h LC50s of 4300 (3610, 5090), 18,200 (6470, 51,200), 62,400 (56,800, 68,500), and 71,700 (68,200, 75,400) µg Ni L-1 were derived for the marine copepod Tigriopus japonicus, the gastropod Monodonta labio, juvenile and adult of the marine fish Oryzias melastigma, respectively. The chronic effect concentration of 10% (EC10) based on the intrinsic rate of increase of the population of T. japonicus was 29 (12, 69) µg Ni L-1. In terms of growth inhibition, the chronic EC10 for M. labio was 34 (17, 67) µg Ni L-1. The results also indicated that T. japonicus in maturation stage (LC10: 484 (349, 919) µg Ni L-1) was less sensitive than its nauplii stage (LC10: 44 (27, 72) µg Ni L-1). This study represents an important addition of high-quality toxicity data to the tropical Ni toxicity database which can be used for future ecological risk assessment of Ni and derivation of its water quality guidelines in tropical regions.

Toward Sustainable Environmental Quality: Priority Research Questions for Asia.

Environmental and human health challenges are pronounced in Asia, an exceptionally diverse and complex region where influences of global megatrends are extensive and numerous stresses to environmental quality exist. Identifying priorities necessary to engage grand challenges can be facilitated through horizon scanning exercises, and to this end we identified and examined 23 priority research questions needed to advance toward more sustainable environmental quality in Asia, as part of the Global Horizon Scanning Project. Advances in environmental toxicology, environmental chemistry, biological monitoring, and risk-assessment methodologies are necessary to address the adverse impacts of environmental stressors on ecosystem services and biodiversity, with Asia being home to numerous biodiversity hotspots. Intersections of the food-energy-water nexus are profound in Asia; innovative and aggressive technologies are necessary to provide clean water, ensure food safety, and stimulate energy efficiency, while improving ecological integrity and addressing legacy and emerging threats to public health and the environment, particularly with increased aquaculture production. Asia is the largest chemical-producing continent globally. Accordingly, sustainable and green chemistry and engineering present decided opportunities to stimulate innovation and realize a number of the United Nations Sustainable Development Goals. Engaging the priority research questions identified herein will require transdisciplinary coordination through existing and nontraditional partnerships within and among countries and sectors. Answering these questions will not be easy but is necessary to achieve more sustainable environmental quality in Asia. Environ Toxicol Chem 2020;39:1485-1505. © 2020 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Occurrence, toxicity and ecological risk of larvicidal oil in the coastal marine ecosystem of Hong Kong.

Application of larvicidal oil (LO) is the most common practice in Hong Kong to control mosquitos, and hence prevent mosquito-borne diseases and protect human health. Globally, this study represented the first comprehensive assessment of toxicity and risk posed by LO to marine organisms. We found concentrations of LO ranged from 0.08 to 0.66 mg/L in coastal seawaters of Hong Kong. Waterborne exposure to water-accommodated fractions of LO resulted in growth inhibition to two microalgal species (72-h EC50: 1.92-2.90 mg/L) and acute mortality to three marine animals (96-h LC50: 3.41-8.10 mg/L). From these toxicity results, a concentration that considered to be hazardous to 5% of species (HC5) was predicted at 1.45 mg/L, while the predicted no-effect concentration was determined to be 0.29 mg/L. The hazard quotient of LO exceeded 1 at 9 out of 15 sites, indicating moderate-to-high ecological risk to exposure of LO in the marine environment of Hong Kong.

Sunscreens containing zinc oxide nanoparticles can trigger oxidative stress and toxicity to the marine copepod Tigriopus japonicus.

The study, for the first time, evaluated the leaching rate of zinc oxide nanoparticles (nZnO) from human skins which were applied with three commercial sunscreens containing nZnO as an active ingredient. The leaching rate of nZnO varied greatly among the sunscreens, with a range of 8-72% (mean ± SD: 45% ± 33%). We further investigated their toxicities to the marine copepod Tigriopus japonicus. We found that 96-h median lethal concentrations of the three sunscreens to T. japonicus were > 5000, 230.6, and 43.0 mg chemical L-1, respectively, equivalent to Zn2+ concentrations at >82.5, 3.2, and 1.2 mg Zn L-1, respectively. Exposure to the individual sunscreens at environmentally realistic concentrations for 96 h led to up-regulation of antioxidant genes in T. japonicus, while they triggered the release of reactive oxygen species based on the results of in vivo assays. Evidently, these nZnO-included sunscreens can cause oxidative stress and hence pose risk to marine organisms.

Occurrence, ecological and human health risks of phenyltin compounds in the marine environment of Hong Kong.

Triphenyltin (TPT) has been known as one of the most toxic compounds being released into the marine environment by anthropogenic means. This study assessed the contamination statuses of TPT and its two major degradants, i.e., monophenyltin and diphenyltin, in seawater, sediment and biota samples from marine environments of Hong Kong, a highly urbanized and densely populated city, and evaluated their ecological and human health risks. The results showed that the Hong Kong's marine environments were heavily contaminated with these chemicals, especially for TPT. Concentration ranges of TPT in seawater, sediment and biota samples were 3.8-11.7 ng/L, 71.8-91.7 ng/g d.w., and 9.6-1079.9 ng/g w.w., respectively. As reflected by high hazard quotients (1.7-5.3 for seawaters; 46.1-59.0 for sediments), TPT exhibited high ecological and human health risks. Our results are essential for the future management and control of anthropogenic TPT use in antifouling paints and as biocides in agriculture.

In vivo toxicities of nine engineered nano metal oxides to the marine diatom Skeletonema costatum and rotifer Brachionus koreanus.

This study compared in vivo acute toxicities of nine engineered nano metal oxides to the marine diatom Skeletonema costatum and rotifer Brachionus koreanus. The sequence of their toxicities to S. costatum, based on growth inhibition, was: nano zinc oxide (nZnO) > nTiO2 (rutile) > nMgO > Annealed nMgO > nTiO2 (anatase) > Î³-nAl2O3 > nIn2O3 > α-nAl2O3 > nSnO2. Similarly, nZnO was also the most toxic to B. koreanus, but the other nano metal oxides were non-lethal. nMgO and nZnO were confirmed to trigger reactive oxygen species (ROS) mediated toxicity to the two marine organisms, while nTiO2 (both anatase and rutile forms) likely induced oxidative stress as shown by their acellular ROS production. nZnO may also cause damage in the endocrine system of B. koreanus, as indicated by the increased transcription of retinoid X receptor. Annealed nMgO reduces its toxicity via removal of O2- and impurities from its surface.

Removal of emerging contaminants from wastewater during chemically enhanced primary sedimentation and acidogenic sludge fermentation.

A novel wastewater treatment process, which couples chemically enhanced primary sedimentation (CEPS) of sewage with acidogenic fermentation of sludge in tandem, has recently been developed to improve the removal of pollutants and nutrients, and recover valuable resources such as phosphorus and organics. This study represented the first laboratory-based examination on the level and removal of the emerging contaminants, including retinoids (i.e., retinoic acids (RAs) and their metabolites) and oestrogenic endocrine disrupting chemicals (EDCs; e.g., 4-nonylphenol, bisphenol A, etc.), in sewage, sludge and its supernatant during this novel wastewater treatment process. The results showed that 65% of retinoids and 73% of EDCs were removed from sewage after aluminum (Al) based CEPS, while 80% of retinoids and 72% of EDCs were removed after iron (Fe) based CEPS. After acidogenic fermentation of the CEPS sludge, 50% and 58% of retinoids, and 50% and 47% of EDCs were further removed in the supernatants of Al-sludge and Fe-sludge, respectively. While there were comparable removals for these two classes of emerging contaminants during Al- and Fe-based CEPS and sludge fermentation, Fe-based CEPS of sewage and sludge fermentation should be preferentially considered, given the relatively lower production of Fe-sludge and lower accumulation of retinoids in Fe-sludge. The levels of retinoids and EDCs in the supernatant and sludge changed during acidogenic fermentation of Fe-sludge. The removals of at-4-oxo-RA (i.e., the dominant retinoid) and bisphenol A (i.e., the dominant EDC) in the supernatant followed the pseudo first-order reaction model, with a half-life of 1.62 days (in the first two days) and 1.55 days (in the whole experiment of seven days), respectively. The results demonstrated the effective removal of emerging contaminants from the sewage and the supernatant during the CEPS and acidogenic sludge fermentation.

Occurrence and trophic magnification profile of triphenyltin compounds in marine mammals and their corresponding food webs.

The occurrence of triphenyltin (TPT) compounds, a highly toxic antifouling biocide, has been documented in marine environments and organisms all over the world. While some studies showed that marine mammals can be used as sentinel organisms to evaluate the pollution status of emerging contaminants in the environment because of their long lifespans and high trophic levels, information regarding the contamination status of TPT in marine mammal species has been limited over the past decade. More importantly, the primary bioaccumulation pathway of TPT in these long-lived apex predators and the corresponding marine food web is still uncertain. Therefore, this study aimed to evaluate the contamination statuses of TPT in two marine mammal species, namely the finless porpoise and the Indo-Pacific humpback dolphin, and assess the trophic magnification potential of TPT along the food webs of these two species, using stable isotope analysis, and chemical analysis with gas chromatography-mass spectrometry. The results showed that TPT is the predominant residue in majority of the analyzed individuals of two marine mammals, with concentrations ranging from 426.2 to 3476.6 ng/g wet weight in their muscle tissues. Our results also demonstrated an exponential increase in the concentration of TPT along the marine food web, indicating that trophic magnification occurs in the respective food webs of the two marine mammals. The range of trophic magnification factors of TPT in the food webs of finless porpoise and Indo-Pacific humpback dolphin was 2.51-3.47 and 2.45-3.39, respectively. These results suggest that high trophic organisms may be more vulnerable to the exposure of TPT-contaminated environments due to the high trophic magnification potential, and thus ecological risk of these compounds ought to be assessed with the consideration of their bioaccumulation potentials in these marine mammals.