جستجوی مقالات مرتبط با کلیدواژه "دافنیا مگنا" در نشریات گروه "پزشکی"

Nanoparticles (NPs) are used in different industries, including electronics, pharmaceuticals, cosmetics, healthcare, and environmental processes. Therefore, it is necessary to evaluate their toxicity in the aquatic environment.

The acute toxicity of six different kinds of nano-sized particulates (SiO2, Fe2O3, Al2O3, TiO2, ZnO, and MgO) to Daphnia Magna were evaluated using the acute toxicity test, according to the U.S EPA method at various exposure times in different concentrations. The LC50 values and their corresponding 95% confidence intervals were calculated using the EPA Probit analysis program.

The highest to lowest LC50 of mortality of the NPs studied were as follows: Al2O3>Fe2O3>SIO2>TiO2>MgO>ZnO. At 96 hours of exposure time, NPs caused morphological change in the gut tract of D. Magna.

In this study, all physiochemical properties of the NPs were similar to those reported in previous studies. Among these properties, chemical composition and purity of NPs are the major factors that could influence the toxicity of NPs to D.Magna.

Background and Textile dye effluents have some potential risks which require effective treatment before discharging into the environment. Advanced oxidation processes can remove pollutants faster than other processes due to active hydroxyl radical production; therefore, increase the efficiency of dye removal. This study was aimed at investigating dye removal process using UVA/ZnO and UVA/TiO2 nanocatalysts.
This study was done in a batch reactor on synthetic and real samples and the effects of initial dye concentrations, TiO2 and ZnO nanoparticles dosage, time, pH and interference compounds on efficiency of dye removal was investigated. The Daphnia Magna was used for bioassay test.
The removal rates of dye in optimum conditions were 69% and 95.5% by UVA/ZnO and UVA/TiO2 processes, respectively and the optimum pH in the process was 9 and 2, respectively. In this study, the initial concentration of dye and COD were found to have adverse relation with removal rate of dye in two processes (p The current study showed that TiO2/UVA process with effective optimization of operational factors, has high performance in R.B 86 dye decolorization and reducing toxicity.

Metronidazole, as one of the most widely used antibiotics in the world, in addition to various benefits, has significant adverse effects on the environment and animals. The catalytic ozonation process is one of the most successful methods for antibiotics removal. However, it should be noted that this process, like other oxidation processes, has some byproducts that can be toxic in the process effluent.
Under optimum conditions for catalytic ozonation in the presence of MgO nanoparticles, 1 sample was obtained from a reactor after 10 minutes of ozonation. The sample was analyzed by gas chromatography–mass spectrometry (GS-MS) and the intermediates were identified. The mineralization rate was determined using TOC analysis and the toxicity changes were calculated through bioassay with Daphnia magna.
Findings: In the present study, 4 compositions were identified as oxidation intermediates. The mineralization rate was about 93.5% and the 48-hour toxicity unit decreased from 1.24 in the influent to 0.32 in the effluent.
A high mineralization rate was obtained in the process. Nevertheless, it was not complete, and thus, the influent solution was converted from toxic to slightly toxic. In conclusion, we can say that catalytic ozonation process in the presence of MgO nanoparticles can be acceptable for metronidazole removal.

In Iran, due to vast development of different chemical and petrochemical industries and water resource pollution to refractory organic matters, using a costeffective method for the removal of those pollutant from drinking water. The aim of this study was to evaluate the performance of magnetic-multiwalled carbon nanotube for the removal of 2,4- dinitrophenol from aquoeous solutions and deteremining toxicity reduction of the effluent.
Adsorption experiments were conducted in a batch system. Magnetic-multiwalled carbon nanotubes were synthesized by co-precipitation method. Variables of contact time (0-90 min), pH (3,5, 7, 9, 11), pollutant concentration (10-100 mg/L) and adsorbent concentration (1-2.5 g/L) were considered. For the determination of toxicity reduction of the effluent, the Bioassay tests were applied by using Daphnia magna which toxicity of 48h and 96 h were obtained.
Results were showed that the maximum removal of 92.97% in the contact time of 90 min were obtained in pH=7, pollutant concentration of 10 mg/L and adsorption concentration of 2.5 g/L. The adsorption process was in accordance with Freundlich isotherm which showed non-uniform and multi-layered adsorption on the surface of the adsorbent and heterogeneous adsorption. The results of the toxicity of 2,4-DNP, before the adsorption process, on the Daphnia magna organism showed that the lethal concentration (LC50) 48h and 96 h of the raw wastewater was 42 and 38 percent (4.2 and 3.8 mg/L), respectively.
The magnetic-multiwalled carbon nanotube adsorbent could be a proper choice for removal of 2,4-DNP, due to high removal efficiency, recyclability, reusability and activity in neutral pH.

Perchloroethylene is a chlorinated hydrocarbon used as a solvent in many industries and services activities such as dry cleaning and auto industry as degreasing. We carried out a bioassay using Daphnia Magna in order to determine the ecological effects of wastewater treatment through applying advanced oxidation processes (ultrasonic, ultraviolet irradiation and hydrogen peroxide processes) for removal of perchloroethylene. Due to the sensitivity of Daphnia and reports indicating this species is the most sensitive aquatic invertebrate to a variety of organic compounds, toxicity of perchloroethylene and its intermediate degradation products during applying different processes was tested using Daphnia. Lethal concentration (LC50) and toxic units (TU) were determined. In to determine toxicity of perchloroethylene, its stock solution was prepared at a concentration of 100 mg/L. Then, nine samples each containing 0 (control), 5, 10, 20, 30, 40, 50, 75, and 100% by volume of the primary stock solution were prepared. To determine the toxicity of the intermediate products of perchloroethylene by ultrasonic, photolysis, photolysis with hydrogen peroxide and photosonic processes, an initial concentration of perchloroethylene for each reactor (100 mg/L) was taken. All experiments were carried out at the Laboratory of Microbiology, Faculty of Health, Tehran University of Medical Sciences, Iran. It was found that the 24 h LC50 for perchloroethylene on Daphnia Magna was 35.51 mg /L. The 48 h, 72 h and 96 h LC50 of perchloroethylene were 28.058, 21.033, and 19.27 mg/L respectively. Toxicity of perchloroethylene was decreased after oxidation processes. The toxicity after hybrid processes was lower than the single processes. The toxicity reduction was the same during all time period. Hence, the hypothesis of reducing toxicity of the intermediate products of perchloroethylene degradation after the abovementioned processes is acceptable. It is noteworthy that although there are different intermediate compounds in the effluent of various chemical oxidation processes,, but they are less toxic compared with the original perchloroethylene; this may be due to the partially concentration of intermediate products that will decrease toxicity.

The contamination of water resources resulting from industrial output discharge is a serious threat to the water-living organisms. Chemical and physical examinations are not enough to evaluate the potential effects of these pollutants on aquatic life. Biological tests can provide appropriate and direct measure of toxicity as a complete physicochemical criterion of wastewater quality. The requierd Daphnia was provided in fish breeding centers of Esfahan and after preparing different concentrations of raw wastewater and decolorated samples in eight percent of the differents volume, 10 Daphnia was added to all containers containing samples of raw wastewater, decolorated and control samples rinsed with diluted water. All samples were observed after 48 hours and the number of dead animals in each test container was counted. In the final experiments, acute toxicity units, LC50 - 48h and efficiency of toxicity removal on the optimum conditions of Electro Fenton process were calculated. Based on the results of toxicity tests it was determined that LC50 - 48h in synthetic wastewater samples with dye concentration in 40mg/L increased from 18% before decoloration reached 70% after decoloration, samples of wastewater synthetic concentrations dye 100 mg/L from 14 to 50%, wastewater synthetic with concentrations dye of 200mg/L from 10 to 35 % and in samples containing of 300 mg/L the dye concentrations of 6.8 reached 20 % respectively. The efficiency of toxicity removal for different dye concentrations reached 76, 72, 71 and 66 % respectively. According to the results obtained, it can be stated that to evaluate the potential toxicity of colored wastewaters discharged into surface waters and to determine the quality criteria for contaminant permissible concentrations, bioassay is a simple, quick and effective procedure.

Bioassay is necessary for assessment of pollution. Because physical and chemical taste are not enough for assessment of potential effects on water ecosystem. Bioassay tests have alot of scientific value inanition doing of them is easy and need less time, also need less space, laboratory equipment’s and expenditure. Therefor such tests have found special attention in water pollution control measure. So whit determine of effluent toxicity and survey of its effects on water ecosystem by bioassay method, can determine the degree and the kind of treatment that are necessary to having optimum condition for water ecosystem. In this research survey of indicator toxicity of Isfahan south wastewater treatment by daphnia magna has been studied. In this study experiments were done on samples of wastewater that has been taken from Isfahans south wastewater treatment (samples has been taken from four place, influent raw wastewater, before and after primary settling tank and after secondary settling tank). Primary daphnia were couch from there living sites, then one of them were cultured alone, after infants of primary daphnia were used for culture in large amount. After prepering necessary dilution of wastewater samples by doing necessary experiments LC50-48-h toxic unit, efficiency of different units and total of wastewater treatment plant were determined. Results reveal that LC50-48-h of influent wastewater is 30%(v/v) and toxic unit is 3.33 and LC50-48-h of wastewater before primary (after preliminary treatment) settling tank, after primary settling tank and after secondary settling tank was determined 32%, 85% and 32% (v/v) respectively, that was on the basis acute toxic unit (ATU) 3.125, 1.92, and 1.76 respectively, efficiency of preliminary treatment in reducing toxicity were determined 6% and efficiency of primary treatment secondary treatment and whole of treatment plant in reducing toxicity were determined 38.4%, 8% and 50% respectively. Data of this research show that bioassay are necessary for assessment of wastewater and control of water pollution. So bioassay can be used as a suitable method for assessment of effect and efficiency of different treatment units and control of toxicity as base information for monitoring of effluent and due to increasingly developing of wastewater treatment systems in Iran, that is necessary appropriate strategy be under taken to monitoring the effluent. The result of this research and same research can be useful.