Oxidative stress and lipid peroxidation in the earthworm Eisenia fetida induced by low doses of fomesafen

Formesafen is a diphenyl ether herbicide that has adverse effects on non-target animals. However, knowledge about the effect of fomesafen on the antioxidant defense system in earthworms is vague. Thus, it is essential to investigate the effects of fomesafen on the antioxidant defense system in earthworms as a precautionary method. In the present study, earthworms (Eisenia fetida) were exposed to artificial soil treated with a range of concentrations of fomesafen (0, 10, 100, and 500 μg kg^?1) and were collected on the 3rd, 7th, 14th, 21st, and 28th days of exposure. Subsequently, the antioxidant enzyme activities (superoxide dismutase (SOD); catalase (CAT); and guaiacol peroxidase (POD)), reactive oxygen species (ROS) level, and malondialdehyde (MDA) content due to fomesafen treatment were examined in earthworms. Compared with the control, the SOD activity increased on the third and seventh days but decreased on the 14th day due to treatment with 100 and 500 μg kg^?1 of fomesafen. The activities of CAT and POD increased significantly on the third, seventh, and 14th days of exposure. In addition, the ROS level was significantly enhanced throughout the entire experimental period and showed a statistically dose-dependent relationship on the seventh and 14th days. The MDA content markedly increased on the seventh day of exposure; however, obvious changes were not detected at other exposure period. Low doses of fomesafen (≤500 μg kg^?1) may result in oxidative damage and lipid peroxidation in E. fetida by inducing the generation of ROS at short exposure periods (14 days). However, the adverse effects of fomesafen gradually disappear as the cooperation of antioxidant enzymes and exposure time are prolonged. This result may be helpful for further studies on the toxicological mechanisms of fomesafen to earthworms.     

Impact of molybdenum nanoparticles on survival,activity of enzymes,and chemical elements in <Emphasis Type="Italic">Eisenia fetida</Emphasis> using test on artificial substrata

The influence of molybdenum oxide nanoparticles (MoO₃) on the growth and survival of Eisenia fetida was established. The activity of antioxidant enzymes and changes in concentration of molybdenum in the body of E. fetida were determined. The degree of bacterial bioluminescence inhibition in extracts of substrates and worm was studied using luminescent strain Escherichia coli K12 TG1. The enzymatic activity of substrates before and after exposure with nanoparticles and worms was assessed. Nanoparticles have concentrations of 10, 40, and 500 mg/kg of dry matter, and substrata are made of artificial soil (substrate A) and microcrystalline cellulose (substrate B). Spherical nanoparticles MoO₃, yellow in color, with size 92?±?0.3 nm, Z-potential 42?±?0.52 mV, molybdenum content 99.8 mass/%, and specific area 12 m²/g were used in the study. A significant decrease by 23.3 % in weight was registered (for MoO₃ NPs at 500 mg/kg) on substrate A (p?≤?0.05). On substrate B, the maximum decrease in weight by 20.5, 33.3, and 16.9 % (p?≤?0.05) was registered at a dose of 10, 40, and 500 mg/kg, respectively; mortality was from 6.6 to 73 %. After the assessment of bacterial bioluminescence inhibition in substrates A and B (extracts) and before worms were put, the toxicity of substrates was established at doses of 40 and 500 mg/kg, expressed in inhibitory concentration (IC) 30 and IC 50 values. Comparatively, on days 7 and 14, after exposure in the presence of E. fetida, no inhibition of bioluminescence was registered in extracts of substrates A and B, indicating the reduction in toxicity of substrates. The initial content of molybdenum in E. fetida was 0.9?±?0.018 mg/kg of dry matter. The degree of molybdenum accumulation in worm tissue was dependent on the dose and substrate quality. In particular, 2–7 mg/kg of molybdenum accumulated from substrate A, while up to 15 kg/kg of molybdenum accumulated from substrate B (day 7). Molybdenum concentration decreased by 64.8 and 57.4 % at doses 40 and 500 mg/kg, respectively, on day 14. The reaction of antioxidant enzymes was shown in an insignificant increase of glutathione reductase (GSR) and catalase (CAT) at concentrations of 10 and 40 mg/kg in substrate A, followed by the subsequent reduction of their activity at the dose of 500 mg/kg MoO₃. The activity of GSR in substrate B against the presence of MoO₃ nanoparticles decreased, with significant difference of 33.5 % (p?≤?0.05) at the dose of 500 mg/kg compared with untreated soil. In experiments with substrate A, an increase of catalase activity was registered for the control sample. The presence of MoO₃ nanoparticles at the concentration of 10 mg/kg in the environment promoted enzymatic activity on days 7 and 14, respectively. A further increase of nanoparticle concentration resulted in the decrease of catalase activity with a minimum value at the concentration of MoO₃ of 500 mg/kg. In the experiment with substrate B at the concentration of MoO₃ nanoparticles of 40 mg/kg, enzymatic activity increases on day 7 of exposure. However, the stimulating effect of nanoparticles stops by day 14 of the experiment and further catalase activity is dose dependent with the smallest value in the experiment with MoO₃ having the concentration of 500 mg/kg.     

Influence of earthworm Eisenia fetida on removal efficiency of N and P in vertical flow constructed wetland

This study investigates biomass, density, photosynthetic activity, and accumulation of nitrogen (N) and phosphorus (P) in three wetland plants (Canna indica, Typha augustifolia, and Phragmites austrail) in response to the introduction of the earthworm Eisenia fetida into a constructed wetland. The removal efficiency of N and P in constructed wetlands were also investigated. Results showed that the photosynthetic rate (P _n), transpiration rate (T _r), and stomatal conductance (S _cond) of C. indica and P. austrail were (p?<?0.05) significantly higher when earthworms were present. The addition of E. fetida increased the N uptake value by above-ground of C. indica, T. augustifolia, and P. australis by 185, 216, and 108 %, respectively; and its P uptake value increased by 300, 355, and 211 %, respectively. Earthworms could enhance photosynthetic activity, density, and biomass of wetland plants in constructed wetland, resulting in the higher N and P uptake. The addition of E. fetida into constructed wetland increased the removal efficiency of TN and TP by 10 and 7 %, respectively. The addition of earthworms into vertical flow constructed wetland increased the removal efficiency of TN and TP, which was related to higher photosynthetic activity and N and P uptake. The addition of earthworms into vertical flow constructed wetland and plant harvests could be the significantly sustainable N and P removal strategy.     

Responses of earthworm to aluminum toxicity in latosol

Excess aluminum (Al) in soils due to acid rain leaching is toxic to water resources and harmful to soil organisms and plants. This study investigated adverse impacts of Al levels upon earthworms (Eisenia fetida) from the latosol (acidic red soil). Laboratory experiments were performed to examine the survival and avoidance of earthworms from high Al concentrations and investigate the response of earthworms upon Al toxicity at seven different Al concentrations that ranged from 0 to 300 mg kg^?1 over a 28-day period. Our study showed that the rate of the earthworm survival was 100 % within the first 7 days and decreased as time elapsed, especially for the Al concentrations at 200 and 300 mg kg^?1. A very good linear correlation existed between the earthworm avoidance and the soil Al concentration. There was no Al toxicity to earthworms with the Al concentration ≤50 mg kg^?1, and the toxicity started with the Al concentration ≥100 mg kg^?1. Low Al concentration (i.e., <50 mg kg^?1) enhanced the growth of the earthworms, while high Al concentration (>100 mg kg^?1) retarded the growth of the earthworms. The weight of earthworms and the uptake of Al by earthworms increased with the Al concentrations from 0 to 50 mg kg^?1 and decreased with the Al concentrations from 50 to 300 mg kg^?1. The protein content in the earthworms decreased with the Al concentrations from 0 to 100 mg kg^?1 and increased from 100 to 300 mg kg^?1. In contrast, the catalase (CAT) and superoxide dismutase (SOD) activities in the earthworms increased with the Al concentrations from 0 to 100 mg kg^?1 and decreased from 100 to 300 mg kg^?1. The highest CAT and SOD activities and lowest protein content were found at the Al concentration of 100 mg kg^?1. Results suggest that a high level of Al content in latosol was harmful to earthworms.     

Effect of heavy metals on tissue-specific antioxidant response in Indian major carps

Concentrations of heavy metals (Cu, Ni, Zn, Cd and Pb) were measured in sediments, water and liver and kidney tissues of three Indian major carps (Labeo rohita, Catla catla and Cirrhinus cirrhosus), belonging to two different weight groups (250 and 500 g), collected from ponds at two different sites (Nalban bheri and Diamond Harbour). The tissues were analysed for the levels of different antioxidant defence systems such as superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GRd), glutathione S-transferase (GST), glutathione (GSH) and malondialdehyde (MDA). Concentrations of all the metals were significantly higher (P < 0.05) in sediment, water and the tissues from Nalban bheri compared to those in Diamond Harbour. Metal concentrations were the lowest in C. cirrhosus, which increased with an increase in fish weight, and the liver accumulated higher amount of metals than the kidney. Activities of all enzymatic and non-enzymatic antioxidant parameters except GPx and GRd were significantly higher (P < 0.05) in the tissues from Nalban bheri than those in Diamond Harbour. Significant multicollinearity was found in the values of SOD, CAT, GST, GRd, GPx and MDA with Pb, Cu and Ni in all three fish species at Nalban and with Cd in L. rohita and C. catla. Principal component analysis results revealed that stress response in a polluted site was directly regulated by an amalgamation of GSH profile and the levels of MDA in a synchronized manner. The study indicated a tissue-specific and species-specific difference for heavy metal-induced oxidative stress response in fish and a correlation between different heavy metals and individual oxidative stress markers.     

Correlations of Eisenia fetida metabolic responses to extractable phenanthrene concentrations through time

Eisenia fetida earthworms were exposed to phenanthrene for thirty days to compare hydroxypropyl-β-cyclodextrin (HPCD) extraction of soil and ¹H NMR earthworm metabolomics as indicators of bioavailability. The phenanthrene 28-d LC₅₀ value was 750 mg/kg (632-891, 95% confidence intervals) for the peat soil tested. The initial phenanthrene concentration was 319 mg/kg, which biodegraded to 16 mg/kg within 15 days, at which time HPCD extraction suggested that phenanthrene was no longer bioavailable. Multivariate statistical analysis of ¹H NMR spectra for E. fetida tissue extracts indicated that phenanthrene exposed and control earthworms differed throughout the 30 day experiment despite the low phenanthrene concentrations present after 15 days. This metabolic response was better correlated to total phenanthrene concentrations (Q² = 0.59) than HPCD-extractable phenanthrene concentrations (Q² = 0.46) suggesting that ¹H NMR metabolomics offers considerable promise as a novel, molecular-level method to directly monitor the bioavailability of contaminants to earthworms in the environment.     

Vermiremediation of dyeing sludge from textile mill with the help of exotic earthworm Eisenia fetida Savigny

The aim of present study was for the vermiremediation of dyeing sludge from textile mill into nutrient-rich vermicompost using earthworm Eisenia fetida. The dyeing sludge was mixed with cattle dung in different ratios, i.e., 0:100 (D₀), 25:75 (D₂₅), 50:50 (D₅₀), 75:25 (D₇₅), and 100:0 (D₁₀₀) with earthworms, and 0:100 (S₀), 25:75 (S₂₅), 50:50 (S₅₀), 75:25 (S₇₅), and 100:0 (S₁₀₀) without earthworms. Minimum mortality and maximum population build-up were observed in a 25:75 mixture. Nitrogen, phosphorus, sodium, and pH increased from the initial to the final products with earthworms, while electrical conductivity, C/N ratio, organic carbon, and potassium declined in all the feed mixtures. Vermicomposting with E. fetida was better for composting to change this sludge into nutrient-rich manure.     

Impact of Parthenium weeds on earthworms (Eudrilus eugeniae) during vermicomposting

The aim of this work is to evaluate the effect of Parthenium-mediated compost on Eudrilus eugeniae during the process of vermicomposting. Nine different concentrations of Parthenium hysterophorus and cow dung mixtures were used to assess toxicity. The earthworms’ growth, fecundity and antioxidant enzyme levels were analysed every 15 days. The antioxidant activities of enzymes [superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx)], considered as biomarkers, indicate the biochemical and oxidative stresses due to the toxin from Parthenium weeds. The earthworms’ growth, biomass gain, cocoon production and antioxidant enzymes were in a low level in a high concentration of P. hysterophorus (without cow dung). The results clearly indicated that appropriate mixing of P. hysterophorus quantity is an essential factor for the survival of earthworms without causing any harm.     

Physiological and molecular responses of the earthworm <Emphasis Type="Italic">Eisenia fetida</Emphasis> to polychlorinated biphenyl contamination in soil

Polychlorinated biphenyls (PCBs) are a class of man-made organic compounds ubiquitously present in the biosphere. In this study, we evaluated the toxic effects of different concentrations of PCBs in two natural soils (i.e. red soil and fluvo-aquic soil) on the earthworm Eisenia fetida. The parameters investigated included anti-oxidative response, genotoxic potential, weight variation and biochemical responses of the earthworm exposed to two different types of soils spiked with PCBs after 7 or 14 days of exposure. Earthworms had significantly lower weights in both soils after PCB exposure. PCBs significantly increased catalase (CAT), superoxide dismutase (SOD), and guaiacol peroxidase (POD) activity in earthworms exposed to either soil type for 7 or 14 days and decreased the malondialdehyde (MDA) content in earthworms exposed to red soil for 14 days. Of the enzymes examined, SOD activity was the most sensitive to PCB stress. In addition, PCB exposure triggered dose-dependent coelomocyte DNA damage, even at the lowest concentration tested. This response was relatively stable between different soils. Three-way analysis of variance (ANOVA) showed that the weight variation, anti-oxidant enzyme activities, and MDA contents were significantly correlated with exposure concentration or exposure duration (P < 0.01). Furthermore, weight variation, CAT activity, and SOD activity were significantly affected by soil type (P < 0.01). Therefore, the soil type and exposure time influence the toxic effects of PCBs, and these factors should be considered when selecting responsive biomarkers.     

Spatial and temporal variations of nitrous oxide flux between coastal marsh and the atmosphere in the Yellow River estuary of China

To investigate the spatial and seasonal variations of nitrous oxide (N₂O) fluxes and understand the key controlling factors, we explored N₂O fluxes and environmental variables in high marsh (HM), middle marsh (MM), low marsh (LM), and mudflat (MF) in the Yellow River estuary throughout a year. Fluxes of N₂O differed significantly between sampling periods as well as between sampling positions. During all times of day and the seasons measured, N₂O fluxes ranged from ?0.0051 to 0.0805 mg N₂O m^?2 h^?1, and high N₂O emissions occurred during spring (0.0278 mg N₂O m^?2 h^?1) and winter (0.0139 mg N₂O m^?2 h^?1) while low fluxes were observed during summer (0.0065 mg N₂O m^?2 h^?1) and autumn (0.0060 mg N₂O m^?2 h^?1). The annual average N₂O flux from the intertidal zone was 0.0117 mg N₂O m^?2 h^?1, and the cumulative N₂O emission throughout a year was 113.03 mg N₂O m^?2, indicating that coastal marsh acted as N₂O source. Over all seasons, N₂O fluxes from the four marshes were significantly different (p?<?0.05), in the order of HM (0.0256?±?0.0040 mg N₂O m^?2 h^?1)?>?MF (0.0107?±?0.0027 mg N₂O m^?2 h^?1)?>?LM (0.0073?±?0.0020 mg N₂O m^?2 h^?1)?>?MM (0.0026?±?0.0011 mg N₂O m^?2 h^?1). Temporal variations of N₂O emissions were related to the vegetations (Suaeda salsa, Phragmites australis, and Tamarix chinensis) and the limited C and mineral N in soils during summer and autumn and the frequent freeze/thaw cycles in soils during spring and winter, while spatial variations were mainly affected by tidal fluctuation and plant composition at spatial scale. This study indicated the importance of seasonal N₂O contributions (particularly during non-growing season) to the estimation of local N₂O inventory, and highlighted both the large spatial variation of N₂O fluxes across the coastal marsh (CV?=?158.31 %) and the potential effect of exogenous nitrogen loading to the Yellow River estuary on N₂O emission should be considered before the annual or local N₂O inventory was evaluated accurately.     

Ecotoxicological responses of the earthworm Eisenia fetida exposed to soil contaminated with HHCB

Although polycyclic musks have been shown to cause lethal and sub-lethal effects on organisms, their biochemical toxicity to earthworms is not well understood. In the current study, we investigated the responses of antioxidant systems and lipid peroxidation after exposing Eisenia fetida to soil contaminated with 1,3,4,6,7,8-hexahydro-4,6,6,7,8,8-hexamethyl-cyclopenta-γ-2-benzopyran (HHCB). Significant increase in lipid peroxidation level was observed on day 14 at two high concentrations, 50 and 100 mg kg⁻¹. Among antioxidant enzymes, the primary response to chronic HHCB exposure can be attributed to superoxide dismutase (SOD) and catalase (CAT). Of the two enzymes, SOD exhibited more sensitive response to HHCB stress. In addition, these two enzymes could have a combined effect on fighting damage by reactive oxygen species, evidenced by a marked relationship between lipid peroxidation and enzyme activity. On the other hand, dose-dependent inhibition of peroxidase (POD) activity has been observed throughout the test. The results suggest that the variations in investigated parameters of E. fetida could be used as responsive biomarkers for oxidative stress caused by HHCB in a soil environment.     

Influence of plant-earthworm interactions on SOM chemistry and p,p'-DDE bioaccumulation

Laboratory experiments assessed how bioaccumulation of weathered p,p′-DDE from soil and humic acid (HA) chemistry are affected by interactions between the plants Cucurbita pepo ssp. pepo and ssp. ovifera and the earthworms Eisenia fetida, Lumbricus terrestris, and Apporectodea caliginosa. Total organochlorine phytoextraction by ssp. pepo increased at least 25% in the presence of any of the earthworm species (relative to plants grown in isolation). Uptake of the compound by ssp. ovifera was unaffected by earthworms. Plants influenced earthworm bioaccumulation as well. When combined with pepo, p,p′-DDE levels in E. fetida decreased by 50%, whereas, in the presence of ovifera, bioconcentration by L. terrestris increased by more than 2-fold. Spectral analysis indicated a decrease in hydrophobicity of HA in each of the soils in which both pepo and earthworms were present. However, HA chemistry from ovifera treatments was largely unaffected by earthworms. Risk assessments of contaminated soils should account for species interactions, and SOM chemistry may be a useful indictor of pollutant bioaccumulation.     

Ecotoxicological effects on the earthworm Eisenia fetida following exposure to soil contaminated with imidacloprid

Imidacloprid, a neonicotinoid insecticide, has been used widely in agriculture worldwide. The adverse effects of imidacloprid on exposed biota have brought it increasing attention. However, knowledge about the effects of imidacloprid on antioxidant defense systems and digestive systems in the earthworm is vague and not comprehensive. In the present study, the changes in the activity of superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), cellulase, reactive oxygen species (ROS), and malondialdehyde (MDA) in the earthworm Eisenia fetida exposed to artificial soil treated with imidacloprid were examined systematically. The results showed that the activity of these biomarkers was closely related to the dose and duration of the exposure to imidacloprid. The activity of SOD was stimulated significantly at doses of 0.66 and 2 mg kg^?1 imidacloprid but markedly inhibited at a dose of 4 mg kg^?1 imidacloprid with prolonged exposure. The activities of CAT and POD increased irregularly at 0.2–4 mg kg^?1 imidacloprid over different exposure times. The level of ROS at a dose of 2 or 4 mg kg^?1 imidacloprid was significantly increased over the entire exposure period. When the concentration of imidacloprid was above 0.66 mg kg^?1, the balance of the activity of the antioxidant enzymes and ROS level was interrupted. The activity of cellulase decreased significantly with prolonged exposure. At the stress of 4 mg kg^?1 imidacloprid, the content of MDA was significantly increased with increasing exposure time. The results of the present study suggest that imidacloprid has a potentially harmful effect on E. fetida and may be helpful for assessment of the risk of imidacloprid to the soil ecosystem environment. However, to obtain more comprehensive toxicity data, it is necessary to investigate the effects of imidacloprid on earthworm using native soils in the future work.     

Influence of short-time imidacloprid and acetamiprid application on soil microbial metabolic activity and enzymatic activity

The influence of two neonicotinoids, i.e., imidacloprid (IMI) and acetamiprid (ACE), on soil microbial activities was investigated in a short period of time using a combination of the microcalorimetric approach and enzyme tests. Thermodynamic parameters such as Q _T (J g^?1 soil), ?H _met (kJ mol^?1), J _Q/S (J g^?1 h^?1), k (h^?1), and soil enzymatic activities, dehydrogenase, phosphomonoesterase, arginine deaminase, and urease, were used to evaluate whole metabolic activity changes and acute toxicity following IMI and ACE treatment. Various profiles of thermogenic curves reflect different soil microbial activities. The microbial growth rate constant k, total heat evolution Q _T (expect for IMI), and inhibitory ratio I show linear relationship with the doses of IMI and ACE. Q _T for IMI increases at 0.0–20 μg g^?1 and then decreases at 20–80 μg g^?1, possibly attributing to the presence of tolerant microorganisms. The 50 % inhibitory ratios (IC₅₀) of IMI and ACE are 95.7 and 77.2 μg g^?1, respectively. ACE displays slightly higher toxicity than IMI. Plots of k and Q _T against microbial biomass-C indicate that the k and Q _T are growth yield-dependent. IMI and ACE show 29.6; 40.4 and 23.0; and 23.3, 21.7, and 30.5 % inhibition of dehydrogenase, phosphomonoesterase, and urease activity, respectively. By contrast, the arginine deaminase activity is enhanced by 15.2 and 13.2 % with IMI and ACE, respectively. The parametric indices selected give a quantitative dose-response relationship of both insecticides and indicate that ACE is more toxic than IMI due to their difference in molecular structures.     

Kinetics of phenol biodegradation at high concentration by a metabolically versatile isolated yeast Candida tropicalis PHB5

A highly tolerant phenol-degrading yeast strain PHB5 was isolated from wastewater effluent of a coke oven plant and identified as Candida tropicalis based on phylogenetic analysis. Biodegradation experiments with C. tropicalis PHB5 showed that the strain was able to utilize 99.4 % of 2,400 mg l^?1 phenol as sole source of carbon and energy within 48 h. Strain PHB5 was also observed to grow on 18 various aromatic hydrocarbons. Haldane model was used to fit the exponential growth data and the following kinetic parameters were obtained: μ _max?=?0.3407 h^?1, K _S?=?15.81 mg l^?1, K _i?=?169.0 mg l^?1 (R ²?=?0.9886). The true specific growth rate, calculated from μ _max, was 0.2113. A volumetric phenol degradation rate (V _max) was calculated by fitting the phenol consumption data with Gompertz model and specific degradation rate (q) was calculated from V _max. The q values were fitted with Haldane model, yielding following parameters: q _max?=?0.2766 g g^?1 h^?1, K _S ′?=?2.819 mg l^?1, K _i ′?=?2,093 (R ²?=?0.8176). The yield factor (Y _X/S ) varied between 0.185 to 0.96 g g^?1 for different initial phenol concentrations. Phenol degradation by the strain proceeded through a pathway involving production of intermediates such as catechol and cis,cis-muconic acid which were identified by enzymatic assays and HPLC analysis.     

Photodegradation of the novel fungicide fluopyram in aqueous solution: kinetics,transformation products,and toxicity evolvement

The aqueous photodegradation of fluopyram was investigated under UV light (λ?≥?200 nm) and simulated sunlight irradiation (λ?≥?290 nm). The effect of solution pH, fulvic acids (FA), nitrate (NO₃ ^?), Fe (III) ions, and titanium dioxide (TiO₂) on direct photolysis of fluopyram was explored. The results showed that fluopyram photodegradation was faster in neutral solution than that in acidic and alkaline solutions. The presence of FA, NO₃ ^?, Fe (III), and TiO₂ slightly affected the photodegradation of fluopyram under UV irradiation, whereas the photodegradation rates of fluopyram with 5 mg L^?1 Fe (III) and 500 mg L^?1 TiO₂ were about 7-fold and 13-fold faster than that without Fe (III) and TiO₂ under simulated sunlight irradiation, respectively. Three typical products for direct photolysis of fluopyram have been isolated and characterized by liquid chromatography tandem mass spectrometry. These products resulted from the intramolecular elimination of HCl, hydroxyl-substitution, and hydrogen extraction. Based on the identified transformation products and evolution profile, a plausible degradation pathway for the direct photolysis of fluopyram in aqueous solution was proposed. In addition, acute toxicity assays using the Vibrio fischeri bacteria test indicated that the transformation products were more toxic than the parent compound.     

Single and combined effects of aluminum (Al<Subscript>2</Subscript>O<Subscript>3</Subscript>) and zinc (ZnO) oxide nanoparticles in a freshwater fish, <Emphasis Type="Italic">Carassius auratus</Emphasis>

The increasing use of nanoparticles (NPs) worldwide has raised some concerns about their impact on the environment. The aim of the study was to assess the toxicity of metal oxide nanoparticles, singly or combined, in a freshwater fish (Carassius auratus). The fish were exposed for 7, 14, and 21 days to different concentrations of NPs (10 μg Al₂O₃.L^?1, 10 μg ZnO.L^?1, 10 μg Al₂O₃.L^?1 plus 10 μg ZnO.L^?1, 100 μg Al₂O₃.L^?1, 100 μg ZnO.L^?1, and 100 μg Al₂O₃.L^?1 plus 100 μg ZnO.L^?1). At the end of each exposure period, antioxidant enzyme activity (catalase, glutathione-S-transferase, and superoxide dismutase), lipid peroxidation, and histopathology were assessed in the gills and livers of C. auratus. The results show an increase in catalase (CAT) and superoxide dismutase (SOD) activity in the gills and livers of fish, especially after 14 days of exposure to single and combined NPs, followed by a reduction at 21 days. An increase in glutathione S-transferase (GST) was observed in gills after 7 days for all tested NP concentrations (single and combined); while in livers, a significant increase was determined after 14 days of exposure to 100 μg.L^?1 of both single ZnO and Al₂O₃ NPs. Lipid peroxidation (LPO) significantly increased in gills after 7 days of exposure to 100 μg.L^?1 Al₂O₃ NPs (single or combined). In livers, LPO increased significantly after 7 days of exposure to all tested concentrations of both single ZnO and Al₂O₃ (except for 10 μg Al₂O₃.L^?1), and after 14 days of exposure to ZnO (10 and 100 μg.L^?1) and Al₂O₃ (100 μg.L^?1)_. The results from histological observations suggest that exposure to metal oxide NPs affected both livers and gills, presenting alterations such as gill hyperplasia and liver degeneration. However, the most pronounced effects were found in gills. In general, this study shows that the tested NPs, single or combined, are capable of causing sub-lethal effects on C. auratus, but when combined, NPs seem to be slightly more toxic than when added alone.     

Degradation of methylparaben in water by corona plasma coupled with ozonation

The degradation of methylparaben (MeP) in water was investigated using a pulsed corona discharge generated in oxygen, above the liquid. A comparison was made between results obtained in semi-batch corona (SBC) configuration (stationary solution, continuous gas flow) and results obtained in a semi-batch corona with recirculation combined with ozonation (SBCR?+?O₃), where the liquid is continuously circulated between a solution reservoir and the plasma reactor and the effluent gas containing ozone is bubbled through the solution in the reservoir. It was found that MeP was completely degraded after 10–15 min of treatment in both configurations. Oxidation by ozone alone, in the absence of plasma, was a slower process. The energy efficiency for MeP removal (Y _MeP) and for mineralization (Y _TOC) was significantly higher in the SBCR?+?O₃ configuration (Y _MeP?=?7.1 g/kWh at 90 % MeP removal and Y _TOC?=?0.41 g/kWh at 50 % total organic carbon (TOC) removal) than in the SBC configuration (Y _MeP?=?0.6 g/kWh at 90 % MeP removal and Y _TOC?=?0.11 g/kWh at 50 % TOC removal).     

Influence of environmental factors on net N2 and N2O production in sediment of freshwater rivers

Denitrification is an important N removal process in aquatic systems but is also implicated as a potential source of global N₂O emissions. However, the key factors controlling this process as well as N₂O emissions remain unclear. In this study, we identified the main factors that regulate the production of net N₂ and N₂O in sediments collected from rivers with a large amount of sewage input in the Taihu Lake region. Net N₂ and N₂O production were strongly associated with the addition of NO₃ ^?-N and NH₄ ⁺-N. Specifically, NO₃ ^?-N controlled net N₂ production following Michaelis–Menten kinetics. The maximum rate of net N₂ production (V _max) was 116.3 μmol N₂-N m^?2 h^?1, and the apparent half-saturation concentration (k _m) was 0.65 mg N L^?1. N₂O to N₂ ratios increased from 0.18?±?0.03 to 0.68?±?0.16 with the addition of NO₃ ^?-N, suggesting that increasing NO₃ ^?-N concentrations favored the production of N₂O more than N₂. The addition of acetate enhanced net N₂ production and N₂O to N₂ ratios, but the ratios decreased by about 59.5 % when acetate concentrations increased from 50 to 100 mg C L^?1, suggesting that the increase of N₂O to N₂ ratios had more to do with the net N₂ production rate rather than acetate addition in this experiment. The addition of Cl^? did not affect the net N₂ production rates, but significantly enhanced N₂O to N₂ ratios (the ratios increased from 0.02?±?0.00 to 0.10?±?0.00), demonstrating that the high salinity effect might have a significant regional effect on N₂O production. Our results suggest that the presence of N-enriching sewage discharges appear to stimulate N removal but also increase N₂O to N₂ ratios.