Little is known about the potential ecotoxicity of engineered nanoparticles (NPs) to aquatic organisms. To carefully address this issue, we conducted a comprehensive toxicity assessment, including ...modified acute (72h) and chronic (21d) toxicity tests as well as nTiO(2) accumulation analysis using Daphnia magna as a model organism. We found that nTiO(2) exerted minimal toxicity to daphnia within the traditional 48h exposure time, but caused high toxicity when the exposure time was extended to 72h. This demonstrated that exposure duration may be a contributing factor in NP-mediated toxicity. Moreover, upon chronic exposure to nTiO(2) for 21d, daphnia displayed severe growth retardation and mortality, as well as reproductive defects. Interestingly, a significant amount of nTiO(2) was found accumulated in daphnia. However, these daphnia displayed difficulty in eliminating nTiO(2) from their body, presenting increased bioconcentration factor (BCF) values. This high level of bioaccumulation may interfere with food intake and ultimately affect growth and reproduction. In summary, long-term exposure of aquatic organisms to nTiO(2) may alter the growing status of these organisms at both individual and population levels, posing risks to aquatic ecosystems.
Iron oxide nanoparticles have been explored recently for their beneficial applications in many biomedical areas, in environmental remediation, and in various industrial applications. However, ...potential risks have also been identified with the release of nanoparticles into the environment. To study the ecological effects of iron oxide nanoparticles on aquatic organisms, we used early life stages of the zebrafish (Danio rerio) to examine such effects on embryonic development in this species. The results showed that ≥10 mg/L of iron oxide nanoparticles instigated developmental toxicity in these embryos, causing mortality, hatching delay, and malformation. Moreover, an early life stage test using zebrafish embryos/larvae is also discussed and recommended in this study as an effective protocol for assessing the potential toxicity of nanoparticles. This study is one of the first on developmental toxicity in fish caused by iron oxide nanoparticles in aquatic environments. The results will contribute to the current understanding of the potential ecotoxicological effects of nanoparticles and support the sustainable development of nanotechnology.
The sodium alginate-H3BO3 (SA-H3BO3) is traditionally used as bioremediation method for wastewater treatment in recirculating aquaculture system. Even though this method has many advantages (e.g., ...high cell loading) for immobilization, the remove of ammonium is not very effective. In this study, a modified method was built by adding polyvinyl alcohol and activated carbon into SA solution, and then crosslinked with saturated H3BO3–CaCl2 solution for creating new beads. Moreover, response surface methodology was utilized for optimizing the immobilization based on Box-Behnken design. The removal rate of ammonium in 96 h was taken as the primary performance criterion to characterize the biological activity of immobilized microorganisms (i.e., Chloyella pyrenoidosa, Spirulina platensis, Nitrifying bacteria, and Photosynthetic bacteria). Based on the results, the optimal parameter of immobilization as follows: the concentration of SA was 1.46%, the concentration of polyvinyl alcohol was 0.23%, the concentration of activated carbon was 0.11%, the crosslinking time was 29.33 h, and the pH was 6.6.
•A modified sodium alginate-H3BO3 method for creating new immobilized beads.•Box-Behnken design was employed to optimize immobilization.•New immobilized beads were useful for removing ammonium from wastewater.
Nanoscale titanium dioxide (nTiO2) has been widely used in cosmetics, catalysts, varnishes, etc., which is raising concerns about its potential hazards to the ecosystem, including the marine ...environment. In this study, the toxicological effect of nTiO2 on the marine phytoplankton Phaeodactylum tricornutum was carefully investigated. The results showed that nTiO2 at concentrations ≥20mg/L could significantly inhibit P. tricornutum growth. The 5-day EC50 of nTiO2 to P. tricornutum growth is 167.71mg/L. Interestingly, nTiO2 was found to exert its most severe inhibition effects on the first day of exposure, at a lower EC50 of 12.65mg/L. During the experiment, nTiO2 aggregates were found to entrap algae cells, which is likely responsible for the observed toxic effects. Direct physical effects such as cell wall damage from the algae entrapment were confirmed by flow cytometry and TEM imaging. Moreover, low indirect effects such as shading and oxidative stress were observed, which supported the idea that direct physical effects could be the dominant factor that causes nTiO2 toxicity in P. tricornutum. Our research provides direct evidence for the toxicological impact of nTiO2 on marine microalgae, which will help us to build a good understanding of the ecological risks of nanoparticles in the marine environment.
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•Toxicological effect of nTiO2 on the marine phytoplankton Phaeodactylum tricornutum was carefully investigated.•nTiO2 showed “high-low” two-step effects on the growth of Phaeodactylum tricornutum.•nTiO2 aggregates were found to entrap algae cells.•Direct physical effects were the dominant factor that caused nTiO2 toxicity on Phaeodactylum tricornutum.
A three‐terminal thin‐film transistor (TFT) architecture is essential for photodetectors to reach a good balance between high responsivity and fast response speed. Bottom‐gate amorphous Ga2O3 ...(a‐Ga2O3) TFTs are fabricated to boost their UV photodetection properties. During the device fabrication process, a simple chemical‐etching solution with the advantages of easy operation, low cost, and compatibility with traditional lithography process, is developed to selectively etch a‐Ga2O3 films. The a‐Ga2O3 channel etched device on Si manifests an effective suppression of the commonly observed gate leakage current. Meanwhile, a patterned a‐Ga2O3 TFT on quartz shows an excellent n‐type TFT performance with an on/off ratio as high as ≈107. It is further applied as a phototransistor, to diminish the persistent photoconductivity (PPC) effect while keeping a high responsivity (R) as well. Under the 254 nm UV illumination, the a‐Ga2O3 phototransistor demonstrates a high light‐to‐dark ratio of 5 × 107, a high responsivity of 5.67 × 103 A W−1, and a high detectivity of 1.87 × 1015 Jones. Remarkably, the PPC phenomenon in a‐Ga2O3 UV phototransistors is effectively suppressed by applying a positive gate pulse, which greatly shortens the decay time to 5 ms and offers a‐Ga2O3 possible inroads into imaging applications.
Amorphous Ga2O3 thin‐film transistors with on/off ratio of ≈107 are fabricated using a highly selective etching method utlitizing tetramethyl ammonium hydroxide solution. These devices are further applied as phototransistors, demonstrating a high light‐to‐dark ratio of 5 × 107, a high responsivity of 5.67 × 103 A W−1 and an effective suppression of persistent photoconductivity with a decay time as low as 5 ms.
The restoration of wetlands has attracted the attention in different countries. Restored coastal wetlands, especially urban wetlands, are sensitive to external pressures. Thus, it is necessary to ...evaluate the efficiency of the restoration of coastal wetlands, which benefits their management and functional maintenance. In this study, a restored mangrove-aquaculture system in Waterlands Resort at Shenzhen was selected for analysis. The distribution and ecological risk assessment of heavy metals in surface sediments were investigated. The results showed that restoration could effectively decrease the heavy metal concentrations in the sediment, while the restored mangrove posed a moderate ecological risk. Most of the heavy metal concentrations were higher during the dry season compared with the wet season. In addition, during the whole investigation, the sediment quality remained failed to achieve the marine sediment criteria required for aquaculture in China.
•Distribution and ecological risk of heavy metals in a restored mangrove-aquaculture system were analyzed.•Restoration effectively decreased most of the heavy metals concentrations in the sediment of the restored wetland.•A moderate ecological risk was determined in sediment of the restored mangrove.
The fast growing exotic Sonneratia apetala had been widely used to restore the mangroves in China. Planted mangroves play important roles in enhancing carbon sequestration and nutrient storage. The ...contents and pools of soil organic carbon (SOC), total nitrogen (TN) and total phosphorus (TP) of simultaneously planted exotic S. apetala and native mixing mangrove (Avicennia marina, accompanied by Aegiceras corniculatum and Kandelia obovata) were quantified to evaluate the ecological restoration effects. Comparing with unvegetated mudflat, the colonization of mangrove can increase the SOC content within 60 cm and total nitrogen contents within 40 cm. No significant differences existed between S. apetala and native mangrove communities for the SOC, TN and TP contents. The restoration of mangrove forests enhanced the soil carbon stock relative to mudflat but significant differences existed only between native mangrove and mudflat. The TN and TP pools were not impacted by the plantation of mangroves. Therefore, plantation of S. apetala less than two decades did not show any advantages on the stocks of organic carbon and nutrients. The mixing native mangrove community should be recommended to enlarge the area of mangrove and enhance the carbon stock capability in the future.
•Contents and pools of SOC, TN and TP in short-term planted exotic Sonneratia apetala and native mangroves were studied.•The mangrove can increase the SOC content within 60 cm and total nitrogen contents within 40 cm.•The mangrove forests increased soil carbon stock but significant difference exist only between native mangrove and mudflat.•The TN and TP pools were not impacted by the short-term plantation of mangroves.
The rapid growth of nanotechnology is stimulating research concerning the potential environmental impacts of manufactured nanomaterials. The present study summarizes, to our knowledge, the first ...examination regarding the potential effects of chronic exposure (32 d) of aquatic organisms (juvenile carp Carassius auratus) to sublethal concentrations (0.04-1.0 mg/L) of fullerene aggregates (nC60/aq; i.e., C60 suspended in water after long-term stirring) with average diameters of approximately 349 and/or 1,394 nm. The results demonstrated that the antioxidant enzymes superoxide dismutase and catalase were induced significantly in the gills and liver of C. auratus exposed to nC60/aq for 32 d, whereas a nonenzymatic antioxidant, glutathione, decreased in all tested tissues. In addition, lipid peroxidation (LPO) levels decreased in most cases, especially in the gills and brain, but exposure to 1.0 mg/L of nC60/aq led to a significant (p < 0.01) increase in the LPO level in the liver. This increase in LPO level in combination with the observed oxidative stress suggested that the liver might be the target of or most susceptible organ to nC60/ aq exposure. Furthermore, the body weight and total length of juvenile carp exposed to 1.0 mg/L of nC60/aq for 32 d decreased significantly (p < 0.05), indicating that nC60/aq had an inhibitory effect on fish growth. The present findings imply that the oxidative stress induced by long-term exposure could be the main mechanism of the toxicity of nC60/aq to juvenile carp. This important work contributes to a better understanding of the potential health effects of exposure to manufactured nanomaterials on species in aquatic ecosystems.
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