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1.
The main objective of this study was to investigate the degradation mechanism, the reaction kinetics, and the evolution of toxicity of naproxen in waters under simulated solar radiation. These criteria were investigated by conducting quenching experiments with reactive oxygen species (ROS), oxygen concentration experiments, and toxicity evaluations with Vibrio fischeri bacteria. The results indicated that the degradation of naproxen proceeds via pseudo first-order kinetics in all cases and that photodegradation included degradation by direct photolysis and by self-sensitization via ROS; the contribution rates of self-sensitized photodegradation were 1.4 %, 65.8 %, and 31.7 % via ·OH, 1O2 and O2 ??, respectively. Furthermore, the oxygen concentration experiments indicated that dissolved oxygen inhibited the direct photodegradation of naproxen, and the higher the oxygen content, the more pronounced the inhibitory effect. The toxicity evaluation illustrated that some of the intermediate products formed were more toxic than naproxen.  相似文献   

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3.
Trichoderma species, the causal agents of green mould disease, induce great losses in Agaricus bisporus farms. Fungicides are widely used to control mushroom diseases although green mould control is encumbered with difficulties. The aims of this study were, therefore, to research in vitro toxicity of several commercial fungicides to Trichoderma isolates originating from Serbian and Bosnia-Herzegovina farms, and to evaluate the effects of pH and light on their growth. The majority of isolates demonstrated optimal growth at pH 5.0, and the rest at pH 6.0. A few isolates also grew well at pH 7. The weakest mycelial growth was noted at pH 8.0–9.0. Generally, light had an inhibitory effect on the growth of tested isolates. The isolates showed the highest susceptibility to chlorothalonil and carbendazim (ED50 less than 1 mg L?1), and were less sensitive to iprodione (ED50 ranged 0.84–6.72 mg L?1), weakly resistant to thiophanate-methyl (ED50 = 3.75–24.13 mg L?1), and resistant to trifloxystrobin (ED50 = 10.25–178.23 mg L?1). Considering the toxicity of fungicides to A. bisporus, carbendazim showed the best selective toxicity (0.02), iprodione and chlorothalonil moderate (0.16), and thiophanate-methyl the lowest (1.24), while trifloxystrobin toxicity to A. bisporus was not tested because of its inefficiency against Trichoderma isolates.  相似文献   

4.
Global warming has become a source of awareness regarding the potential deleterious effects of extreme abiotic factors (e.g., temperature, dissolved oxygen (DO) levels) and also their influence on chemicals toxicity. In this work, we studied the combined effects of nickel and temperature (low and high levels) and nickel and low levels of DO to Daphnia magna, and concentration addition and independent action concepts as well as their deviations for synergism/antagonism, dose ratio and dose level dependency, were applied to survival and feeding rate data. Nickel single exposure showed an LC50 value for 48 h of 7.36 mg l−1 and an EC50 value for feeding impairment at 2.41 mg l−1. In the acute exposures to high and low temperatures, 50% of mortality was observed, respectively, at 30.7°C and 4.2°C whereas 50% reduction on the feeding activity was recorded at 22.6°C and 16.0°C. Relatively to low DO levels, a LC50 value for 48 h of 0.5 mg l−1 was obtained; feeding activity EC50 value was 2 mg l−1. On acute combined experiments, antagonism was observed for the combination of nickel and extreme temperatures, whereas a synergistic behaviour was observed in the combined exposure of nickel and low DO levels. At sublethal levels, nickel showed to be the main inducer of toxicity at high and low temperatures but not at low levels of dissolved oxygen. Toxicokinetics and toxicodynamics modelling studies should be made in the future to understand the toxicological pathways involved on complex combinations of stressors and to validate any conclusions.  相似文献   

5.
We conducted acute toxicity tests and sediment toxicity tests for copper pyrithione (CuPT) and a metal pyrithione degradation product, 2,2′-dipyridyldisulfide [(PS)2], using a marine polychaete Perinereis nuntia. The acute toxicity tests yielded 14-d LC50 concentrations for CuPT and (PS)2 of 0.06 mg L−1 and 7.9 mg L−1, respectively. Sediment toxicity tests resulted in 14-d LC50 concentrations for CuPT and (PS)2 of 1.1 mg kg−1 dry wt. and 14 mg kg−1 dry wt., respectively. In addition to mortality, sediment avoidance behavior and decreases in animal growth rate were observed; growth rate was the most susceptible endpoint in the sediment toxicity tests of both toxicants. Thus, we propose lowest observed effect concentrations of 0.3 mg kg−1 dry wt. and 0.2 mg kg−1 dry wt. for CuPT and (PS)2, respectively, and no observed effect concentrations of 0.1 mg kg−1 dry wt. for both CuPT and (PS)2. The difference in the toxicity values between CuPT and (PS)2 observed in the acute toxicity test was greater than the difference in these values in the sediment toxicity test, and we attribute this to (PS)2 being more hydrophilic than CuPT. In addition to the toxicity tests, we analyzed conjugation activity of several polychaete enzymes to the toxicants and marked activity of palmitoyl coenzyme-A:biocides acyltransferase and UDP-glucuronosyl transferase was observed.  相似文献   

6.
Surface oxygen functional groups can affect the morphological characteristics, aggregation kinetics, and adsorption capacity of multi-walled carbon nanotubes (MWCNTs). However, little is known about the quantitative relationship between oxygen content and the dispersion stability of MWCNTs. To investigate the effects of surface oxidization, MWCNTs were oxidized using concentrated H2SO4/HNO3 acids for 0, 1, 2, 4, and 8 h, respectively. Experimental results showed that the oxygen content of MWCNTs increased with surface oxidization time. Linear correlations were found to exist between the oxygen content, critical coagulation concentration (CCC) for NaCl, and critical coagulation pH values of MWCNTs detected by optical density at 800 nm. The CCC values for CaCl2 increased with oxygen contents for unmodified MWCNTs and lowly oxidized MWCNTs, while which decreased after further increasing the surface oxidization. CCC ratios in the presence of Ca2+ to Na+ were consistent with the empirical Schulze–Hardy rule for unmodified MWCNTs and lowly oxidized MWCNTs; however, which were much lower than the expected values for highly oxidized MWCNTs. Fulvic acid can clearly increase the stability of MWCNT suspension with unmodified MWCNTs and lowly oxidized MWCNTs, while it cannot affect the dispersion of highly oxidized MWCNTs. This study implied that the oxidation and presence of fulvic acid will possibly increase the mobility, exposure, bioavailability, and toxicity of MWCNTs.  相似文献   

7.
利用MATLAB/SIMULINK对序批式生物膜反应器内的氨氧化细菌与亚硝酸盐氧化菌的生化反应进行仿真预测。模型的验证结果表明,适当的选择模型中的溶解氧浓度、碱度以及温度3种参数,SIMULINK仿真动力学模型能够比较准确地对氨氧化细菌与亚硝酸氧化细菌处理生活污水的过程进行仿真和预测.NH4+-N、NO2--N和NO3--N 3种基质仿真值的绝对平均误差最大为15.88,最小为1.13;NH4+-N、NO2--N和NO3--N的Nash.Suttcliffe模拟效率系数分别为99.36%、98.64%和99.25%;此外,还对SIMULINK仿真动力学模型中的溶解氧浓度、碱度以及温度进行了灵敏度分析,结果表明,温度的灵敏度最大、溶解氧次之、碱度灵敏度相对最小。  相似文献   

8.
The influence of soil properties on the bioavailability and toxicity of Co to barley (Hordeum vulgare L.) root elongation was investigated. Ten soils varying widely in soil properties were amended with seven doses of CoCl2. Soil properties greatly influenced the expression of Co toxicity. The effective concentration of added Co causing 50% inhibition (EC50) ranged from 45 to 863 mg kg−1, representing almost 20-fold variation among soils. Furthermore, we investigated Co toxicity in relation to Co concentrations and free Co2+ activity in soil solution. The EC50 values showed variation among soils of 17- and 29-fold, based on the Co concentration in soil solution and free Co2+ activity, respectively. Single regressions were carried out between Co toxicity threshold values and selected soil properties. Models obtained showed that soil effective cation exchange capacity (eCEC) and exchangeable calcium were the most consistent single predictors of the EC50 values based on soil added Co.  相似文献   

9.
Sulfonamides (SAs), the oldest chemotherapeutic agents used for antimicrobial therapy, still play an important role in veterinary mass treatments. Consequently, traces of these compounds, alone or in combinations, have been repeatedly detected in the environment. Sulfamethazine (SMZ) deserves particular attention not only because it is the most used veterinary SA, but also due to its proven effects on fertility in mice and on thyroid hormone homeostasis in rats. In this study, after evaluating the acute toxicity to Daphnia magna of six veterinary SAs and trimethoprim (TMP), the additivity of SMZ to each other compound was tested using the isobologram method. Two reproduction tests on the same biological model were also performed in order to derive LOEC and NOEC of SMZ. The acute EC50 was in the range 131–270 mg L−1 for all the compounds tested with the exception of sulfaguanidine (EC50 = 3.86 mg L−1). In acute binary tests SMZ showed a complex interaction with sulfaquinoxaline (superadditivity, additivity or subadditivity) at the three different combination ratios tested, simple additivity to TMP and less than additive interaction when paired to the other SAs. LOEC and NOEC of SMZ obtained from reproduction tests were 3.125 and 1.563 mg L−1, respectively. In conclusion, SMZ should not harm the crustacean population at environmentally realistic concentrations. Its toxicity is comparable to that of other systemic SAs, and their binary interactions are less than additive. The same can not be entirely said for enteric SAs, and considering that these compounds are administered at high doses and mostly excreted in unmetabolised form, further evaluation of their impact to the aquatic environment seems advisable.  相似文献   

10.
To document the toxicity of copper and nickel in binary mixtures, freshwater amphipods Gammarus pulex were exposed to the metals given independently or as mixtures. Toxicity to Cu alone was relatively high: 96-h LC10 and LC50 were found at 91 and 196 μg L?1, respectively. Toxicity to Ni alone was very low, with 96-h LC10 and LC50 of 44,900 and 79,200 μg L?1, respectively. Mixture toxicities were calculated from single toxicity data using conventional models. Modeled toxicity was then compared with the measured toxicity of the binary mixture. Two kinds of mixtures were tested. Type I mixtures were designed as combinations of Cu and Ni given at the same effect concentrations, when taken independently, to identify possible interactions between copper and nickel. In type II mixtures, Cu concentrations varied from 0 to 600 μg L?1 while the nickel concentration was kept constant at 500 μg L?1 to mimic conditions of industrial wastewater discharges. Ni and Cu showed synergic effects in type I mixtures while type II mixtures revealed antagonistic effects. Low doses of Ni reduced Cu toxicity towards G. pulex. These results show that even for simple binary mixtures of contaminants with known chemistry and toxicity, unexpected interactions between the contaminants may occur. This reduces the reliability of conventional additivity models.  相似文献   

11.
人工湿地植物泌氧与污染物降解耗氧关系研究   总被引:7,自引:0,他引:7  
实验采用静态水培方法研究了香蒲(Typha orientalis)、芦苇(Phragmites australis)和水葱(Scirpus validus)3种常见湿地水生植物潜在泌氧能力、去污效果,并对水生植物泌氧量与污染物降解耗氧量进行了计算分析,从而阐明湿地植物泌氧与污染物降解耗氧之间的关系。结果表明,3种植物泌氧能力由大到小依次为:芦苇香蒲水葱,其中,芦苇比放氧速率、面积泌氧率均最高,分别为3.36 mg O2/(g.d)和4.35 g O2/(m2.d)。植物对湿地系统中污染物的去除有重要影响,各植物系统COD去除速率在3.46~3.77 g/(m2.d)之间;NH4+-N去除速率在0.07~0.13 g/(m2.d);TN去除速率在0.25~0.27 g/(m2.d);TP去除速率均为0.09 g/(m2.d);均好于无植物空白系统。计算表明,各植物体系泌氧量在0.48~0.55 g O2/d之间;各植物体系COD、NH4+-N耗氧量在0.41~0.46 g O2/d之间;植物净泌氧量在0.02~0.12 g O2/d之间。植物泌氧量与COD、NH4+-N耗氧量呈显著正相关关系。若应用人工湿地处理城镇生活污水,各植物体系COD最大去除负荷在3.81~4.35 g/(m2.d)之间,NH4+-N最大去除负荷在0.83~0.95 g/(m2.d)之间,最大水力负荷在1.65~1.89 cm/d之间。  相似文献   

12.
Photochemical advanced oxidation processes have been considered for the treatment of water and wastewater containing the herbicide atrazine (ATZ), a possible human carcinogen and endocrine disruptor. In this study, we investigated the effects of the photon emission rate and initial concentration on ATZ photolysis at 254 nm, an issue not usually detailed in literature. Moreover, the role of reactive oxygen species (ROS) is discussed. Photon emission rates in the range 0.87?×?1018–3.6?×?1018 photons L?1 s?1 and [ATZ]0?=?5 and 20 mg L?1 were used. The results showed more than 65 % of ATZ removal after 30 min. ATZ photolysis followed apparent first-order kinetics with k values and percent removals decreasing with increasing herbicide initial concentration. A fivefold linear increase in specific degradation rate constants with photon emission rate was observed. Also, regardless the presence of persistent degradation products, toxicity was efficiently removed after 60-min exposure to UV radiation. Experiments confirmed a noticeable contribution of singlet oxygen and radical species to atrazine degradation during photolysis. These results may help understand the behavior of atrazine in different UV-driven photochemical degradation treatment processes.  相似文献   

13.
Han SK  Hwang TM  Yoon Y  Kang JW 《Chemosphere》2011,84(8):1095-1101
The generation of reactive species in an aqueous goethite suspension, under room light and aeration conditions, was investigated using the electron paramagnetic resonance (EPR) technique employing spin trap agents. The trap reagents, including 5,5-dimethylpyrroline N-oxide (DMPO) and 2,2,6,6-tetramethylpiperidine (TEMP), were used for the detection of OH radicals (OH) and singlet oxygen (1O2), respectively. On the addition of DMPO to the goethite suspended solution, a DMPO-OH adduct was formed, which was not decreased, even in the presence of the OH scavenger, mannitol. This result implied a false positive interpretation from the DMPO-OH EPR signal. In the presence of TEMP reagent, a TEMP-O signal was detected, which was completely inhibited in the presence of the singlet oxygen scavenger, sodium azide. With both DMPO-OH and TEMP-O radicals in the presence and absence of radical scavengers, singlet oxygen was observed to be the key species formed in the room-light sensitized goethite suspension. In the goethite/H2O2 system; however, both OH and singlet oxygen were generated, with significant portions of DMPO-OH resulting from both OH and singlet oxygen. In fact, the DMPO-OH resulting from OH should be carefully calculated by correcting for the amount of DMPO-OH due to singlet oxygen. This study reports, for the first time, that the goethite suspensions may also act as a natural sensitizer, such as fulvic acids, to form singlet oxygen.  相似文献   

14.
The quantification of oxygen release by plants in different stages of wetland plant life cycle was made in this study. Results obtained from 1 year measurement in subsurface wetland microcosms demonstrated that oxygen release from Phragmites australis varied from 108.89 to 404.44 mg O2/m2/d during the different periods from budding to dormancy. Plant species, substrate types, and culture solutions had a significant effect on the capacity of oxygen release of wetland plants. Oxygen supply by wetland plants was estimated to potentially support a removal of 300.37 mg COD/m2/d or 55.87 mg NH4-N/m2/d. According to oxygen balance analysis, oxygen release by plants could provide 0.43–1.12 % of biochemical oxygen demand in typical subsurface-flow constructed wetlands (CWs). This demonstrates that oxygen release of plants may be a potential source for pollutants removal especially in low-loaded CWs. The results make it possible to quantify the role of plants in wastewater purification.  相似文献   

15.
Limited information is available on the environmental behavior and associated potential risk of manufactured oxide nanoparticles (NPs). In this research, toxicity of nanoparticulate and bulk ZnO, Al2O3 and TiO2 were examined to the nematode Caenorhabditis elegans with Escherichia coli as a food source. Parallel experiments with dissolved metal ions from NPs were also conducted. The 24-h median lethal concentration (LC50) and sublethal endpoints were assessed. Both NPs and their bulk counterparts were toxic, inhibiting growth and especially the reproductive capability of the nematode. The 24-h LC50 for ZnO NPs (2.3 mg L−1) and bulk ZnO was not significantly different, but significantly different between Al2O3 NPs (82 mg L−1) and bulk Al2O3 (153 mg L−1), and between TiO2 NPs (80 mg L−1) and bulk TiO2 (136 mg L−1). Oxide solubility influenced the toxicity of ZnO and Al2O3 NPs, but nanoparticle-dependent toxicity was indeed observed for the investigated NPs.  相似文献   

16.
Cadmium (Cd) toxicity in plants leads to serious disturbances of physiological processes, such as inhibition of chlorophyll synthesis, oxidative injury to the plant cells and water and nutrient uptake. Response of Matricaria chamomilla L. to calcium chloride (CaCl2) enrichment in growth medium for reducing Cd toxicity were studied in this study. Hydroponically cultured seedlings were treated with 0, 0.1, 1, and 5 mM CaCl2, under 0, 120, and 180 μM CdCl2 conditions, respectively. The study included measurements pertaining to physiological attributes such as growth parameters, Cd concentration and translocation, oxidative stress, and accumulation of phenolics. Addition of CaCl2 to growth media decreased the Cd concentration, activity of antioxidant enzymes, and reactive oxygen species accumulation in the plants treated with different CdCl2, but increased the growth parameters. Malondialdehyde and total phenolics in shoots and roots were not much affected when plants were treated only with different CaCl2 levels, but it showed a rapid increase when the plants were exposed to 120 and 180 CdCl2 levels. CaCl2 amendment also ameliorated the CdCl2-induced stress by reducing oxidative injury. The beneficial effects of CaCl2 in ameliorating CdCl2 toxicity can be attributed to the Ca-induced reduction of Cd concentration, by reducing the cell-surface negativity and competing for Cd2+ ion influx, activity enhancement of antioxidant enzymes, and biomass accumulation.  相似文献   

17.
Fe2O3 and CeO2 modified activated coke (AC) synthesized by the equivalent-volume impregnation were employed to remove elemental mercury (Hg0) from simulated flue gas at a low temperature. Effects of the mass ratio of Fe2O3 and CeO2, reaction temperature, and individual flue gas components including O2, NO, SO2, and H2O (g) on Hg0 removal efficiency of impregnated AC were investigated. The samples were characterized by Brunauer–Emmett–Teller (BET), X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). Results showed that with optimal mass percentage of 3 % Fe2O3 and 3 % CeO2 on Fe3Ce3/AC, the Hg0 removal efficiency could reach an average of 88.29 % at 110 °C. Besides, it was observed that O2 and NO exhibited a promotional effect on Hg0 removal, H2O (g) exerted a suppressive effect, and SO2 showed an insignificant inhibition without O2 to some extent. The analysis of XPS indicated that the main species of mercury on used Fe3Ce3/AC was HgO, which implied that adsorption and catalytic oxidation were both included in Hg0 removal. Furthermore, the lattice oxygen, chemisorbed oxygen, and/or weakly bonded oxygen species made a contribution to Hg0 oxidation.  相似文献   

18.
Understanding oxygen release by plants is important to the design of constructed wetlands for wastewater treatment. Lab-scale systems planted with Phragmites australis were studied to evaluate the amount of oxygen release by plants using electrode techniques and oxygen consumption model. Oxygen release rate (0.14 g O2/m2/day) measured using electrode techniques was much lower than that (3.94–25.20 gO2/m2/day) calculated using the oxygen consumption model. The results revealed that oxygen release by plants was significantly influenced by the oxygen demand for the degradation of pollutants, and the oxygen release rate increased with the rising of the concentration of degradable materials in the solution. The summary of the methods in qualifying oxygen release by wetland plants demonstrated that variations existed among different measuring methods and even in the same measuring approach. The results would be helpful for understanding the contribution of plants in constructed wetlands toward actual wastewater treatment.  相似文献   

19.
Among the emerging literature addressing the biological effects of nanoparticles, very little information exists, particularly on aquatic organisms, that evaluates nanoparticles in comparison to non-nanocounterparts. Therefore, the potential effects of nano-scale and non-nano-scale TiO2 and ZnO on the water flea, Daphnia magna, were examined in 48-h acute toxicity tests using three different test media, several pigment formulations – including coated nanoparticles – and a variety of preparation steps. In addition, a 21-d chronic Daphnia reproduction study was performed using coated TiO2 nanoparticles. Analytical ultracentrifugation analyses provided evidence that the nanoparticles were present in a wide range of differently sized aggregates in the tested dispersions. While no pronounced effects on D. magna were observed for nano-scale and non-nano-scale TiO2 pigments in 19 of 25 acute (48-h) toxicity tests (EC50 > 100 mg L−1), six acute tests with both nano- and non-nano-scale TiO2 pigments showed slight effects (EC10, 0.5–91.2 mg L−1). For the nano-scale and non-nano-scale ZnO pigments, the acute 48-h EC50 values were close to the 1 mg L−1 level, which is within the reported range of zinc toxicity to Daphnia. In general, the toxicity in the acute tests was independent of particle size (non-nano-scale or nano-scale), coating of particles, aggregation of particles, the type of medium or the applied pre-treatment of the test dispersions. The chronic Daphnia test with coated TiO2 nanoparticles demonstrated that reproduction was a more sensitive endpoint than adult mortality. After 21 d, the NOEC for adult mortality was 30 mg L−1 and the NOEC for offspring production was 3 mg L−1. The 21-d EC10 and EC50 values for reproductive effects were 5 and 26.6 mg L−1, respectively. This study demonstrates the utility of evaluating nanoparticle effects relative to non-nano-scale counterparts and presents the first report of chronic exposure to TiO2 nanoparticles in D. magna.  相似文献   

20.

Pharmaceuticals reach terrestrial environments through the application of treated wastewaters and biosolids to agricultural soils. We have investigated the toxicity of 15 common pharmaceuticals, classified as nonsteroidal anti-inflammatory drugs (NSAIDs), blood lipid-lowering agents, β-blockers and antibiotics, in two photosynthetic organisms. Twelve pharmaceuticals caused inhibitory effects on the radicle and hypocotyl elongation of Lactuca sativa seeds. The EC50 values obtained were in the range of 170–5656 mg L−1 in the case of the radicle and 188–4558 mg L−1 for the hypocotyl. Propranolol was the most toxic drug for both root and hypocotyl elongation, followed by the NSAIDs, then gemfibrozil and tetracycline. Other effects, such as root necrosis, inhibition of root growth and curly hairs, were detected. However, even at the highest concentrations tested (3000 mg L−1), seed germination was not affected. NSAIDs decreased the photosynthetic yield of Chlamydomonas reinhardtii, but only salicylic acid showed EC50 values below 1000 mg L−1. The first effects detected at low concentrations, together with the concentrations found in environmental samples, indicate that the use of biosolids and wastewaters containing pharmaceuticals should be regulated and their compositions assessed in order to prevent medium- and long-term impacts on agricultural soils and crops.

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