خيارات البحث
النتائج 1681 - 1690 من 1,955
Effects of cadmium exposure on digestive enzymes, antioxidant enzymes, and lipid peroxidation in the freshwater crab Sinopotamon henanense النص الكامل
2013
Wu, Hao | Xuan, Ruijing | Li, Yingjun | Zhang, Xiaomin | Wang, Qian | Wang, Lan
In this study, the effects of cadmium (Cd) stress on the activities of disaccharidases (sucrase, lactase, and maltase), amylase, trypsin, pepsase, superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and malondialdehyde (MDA) content in the alimentary system of freshwater crabs Sinopotamon henanense were studied. Results showed that the enzyme activities in the stomach, intestine, and hepatopancreas changed with Cd concentration. In terms of digestive enzymes, Cd exposure had an inhibitory effect on the activities of the disaccharidases, amylase, and pepsase (only in the stomach). Significant induction of trypsin activity by Cd at a lower concentration was observed, but as Cd concentration increased, trypsin activity decreased. Maltase activity showed a slight recovery after inhibition by Cd. The activities of SOD and CAT increased initially and decreased subsequently. Cd significantly inhibited the activity of GPx. MDA content increased with increasing concentration of Cd. These results showed that acute Cd exposure led to harmful effects on the alimentary system of crabs, which are likely linked to Cd induced oxidative stress.
اظهر المزيد [+] اقل [-]The influence of copper on tebuconazole sorption onto soils, humic substances, and ferrihydrite النص الكامل
2013
Čadková, Eva | Komárek, Michael | Kaliszová, Regina | Száková, Jiřina | Vaněk, Aleš | Bordas, François | Bollinger, Jean-Claude
The aim of this study is to investigate how the presence of Cu influences tebuconazole (Teb) sorption onto contrasting soil types and two important constituents of the soil sorption complex: hydrated Fe oxide and humic substances. Tebuconazole was used in commercial form and as an analytical-grade chemical at different Teb/Cu molar ratios (1:4, 1:1, 4:1, and Teb alone). Increased Cu concentrations had a positive effect on tebuconazole sorption onto most soils and humic substances, probably as a result of Cu−Teb tertiary complexes on the soil surfaces. Tebuconazole sorption increased in the following order of different Teb/Cu ratios 1:4 > 1:1 > 4:1 > without Cu addition, with the only exception for the Leptosol and ferrihydrite. The highest K f value was observed for humic substances followed by ferrihydrite, the Cambisol, the Arenosol, and the Leptosol. The sorption of analytical-grade tebuconazole onto all matrices was lower, but the addition of Cu supported again tebuconazole sorption. The Teb/Cu ratio with the highest Cu addition (1:4) exhibited the highest K f values in all matrices with the exception of ferrihydrite. The differences in tebuconazole sorption can be attributed to the additives present in the commercial product. This work proved the importance of soil characteristics and composition of the commercially available pesticides together with the presence of Cu on the behavior of tebuconazole in soils.
اظهر المزيد [+] اقل [-]Assessment of natural sepiolite on cadmium stabilization, microbial communities, and enzyme activities in acidic soil النص الكامل
2013
Sun, Yuebing | Sun, Guohong | Xu, Yingming | Wang, Lin | Liang, Xuefeng | Lin, Dasong | Hu, Fazhi
A pot trial was conducted to assess the efficiency of sepiolite-induced cadmium (Cd) immobilization in ultisoils. Under Cd concentrations of 1.25, 2.5, and 5 mg kg⁻¹, the available Cd in the soil after the application of 1–10 % sepiolite decreased by a maximum of 44.4, 23.0, and 17.0 %, respectively, compared with no sepiolite treatments. The increase in the values of soil enzyme activities and microbial number proved that a certain metabolic recovery occurred after sepiolite treatment. The dry biomass of spinach (Spinacia oleracea) increased with increasing sepiolite concentration in the soil. However, the concentration (dry weight) of Cd in the spinach shoots decreased with the increase in sepiolite dose, with maximum reduction of 92.2, 90.0, and 84.9 %, respectively, compared with that of unamended soils. Under a Cd level of 1.25 mg kg⁻¹, the Cd concentration in the edible parts of spinach at 1 % sepiolite amendment was lower than 0.2 mg kg⁻¹ fresh weight, the maximum permissible concentration (MPC) of Cd in vegetable. Even at higher Cd concentrations (2.5 and 5 mg kg⁻¹), safe spinach was produced when the sepiolite treatment was up to 5 %. The results showed that sepiolite-assisted remediation could potentially succeed on a field scale by decreasing Cd entry into the food chain.
اظهر المزيد [+] اقل [-]Polyaromatic hydrocarbon exposure: an ecological impact ambiguity النص الكامل
2013
Ball, Andrew | Truskewycz, Adam
Polyaromatic hydrocarbons (PAHs) represent a fraction of petroleum hydrocarbons and are currently one of the foremost sources of generating energy in today’s contemporary society. However, evidence highlighted in this review show that PAH pollution, as a result of oil spills, hazardous PAH-contaminated working environments and technologies which do not efficiently utilise fuels, as well as natural sources of emissions (e.g. forest fires) may have significant health implications for all taxa. The extent of damage to organisms from PAH exposure is dependent on numerous factors including degree and type of PAH exposure, nature of the environment contaminated (i.e. terrestrial or aquatic), the ability of an organism to relocate to pristine environments, type and sensitivity of organism to specific hydrocarbon fractions and ability of the organism to metabolise different PAH fractions. The review highlights the fact that studies on the potential damage of PAHs should be carried out using mixtures of hydrocarbons as opposed to individual hydrocarbon fractions due to the scarcity of individual fractions being a sole contaminant. Furthermore, potential damage of PAH-contaminated sites should be assessed using an entire ecological impact outlook of the affected area.
اظهر المزيد [+] اقل [-]Modelling the phytoplankton dynamics in a nutrient-rich solar saltern pond: predicting the impact of restoration and climate change النص الكامل
2013
Khemakhem, Hajer | Elloumi, Jannet | Ayadi, Habib | Aleya, Lotfi | Moussa, Mahmoud
An ecological model for the solar saltern of Sfax (Tunisia) was established and validated by comparing simulation results to observed data relative to horizontal distributions of temperature, nutrients and phytoplankton biomass. Sensitivity analysis was performed in order to assess the influence of the main ecological model parameters. First applied at the saltern's pond A1, the model was calibrated with field data measured over 4 years of study (from 2000 to 2003), which allowed an evaluation of parameters such as maximum growth rate of phytoplankton, optimal growth temperature and constant of half saturation for P/N assimilation by phytoplankton. Simulation results showed that the model allowed us to predict realistic phytoplankton variations of the study area, though we were unable to accurately reproduce the nutrient variation. The model was then applied to simulations of the impact of changes in phytoplankton biomass through scenarios such as hypothetic climate changes and saltern restoration.
اظهر المزيد [+] اقل [-]River water quality assessment using environmentric techniques: case study of Jakara River Basin النص الكامل
2013
Mustapha, Adamu | Ahmad Zaharin Aris, | Juahir, Hafizan | Ramli, Mohammad Firuz | Kura, Nura Umar
Jakara River Basin has been extensively studied to assess the overall water quality and to identify the major variables responsible for water quality variations in the basin. A total of 27 sampling points were selected in the riverine network of the Upper Jakara River Basin. Water samples were collected in triplicate and analyzed for physicochemical variables. Pearson product-moment correlation analysis was conducted to evaluate the relationship of water quality parameters and revealed a significant relationship between salinity, conductivity with dissolved solids (DS) and 5-day biochemical oxygen demand (BOD5), chemical oxygen demand (COD), and nitrogen in form of ammonia (NH4). Partial correlation analysis (r p) results showed that there is a strong relationship between salinity and turbidity (r p = 0.930, p = 0.001) and BOD5 and COD (r p = 0.839, p = 0.001) controlling for the linear effects of conductivity and NH4, respectively. Principal component analysis and or factor analysis was used to investigate the origin of each water quality parameter in the Jakara Basin and identified three major factors explaining 68.11 % of the total variance in water quality. The major variations are related to anthropogenic activities (irrigation agricultural, construction activities, clearing of land, and domestic waste disposal) and natural processes (erosion of river bank and runoff). Discriminant analysis (DA) was applied on the dataset to maximize the similarities between group relative to within-group variance of the parameters. DA provided better results with great discriminatory ability using eight variables (DO, BOD5, COD, SS, NH4, conductivity, salinity, and DS) as the most statistically significantly responsible for surface water quality variation in the area. The present study, however, makes several noteworthy contributions to the existing knowledge on the spatial variations of surface water quality and is believed to serve as a baseline data for further studies. Future research should therefore concentrate on the investigation of temporal variations of water quality in the basin.
اظهر المزيد [+] اقل [-]Mercury, methylmercury, and selenium in blood of bird species from Doñana National Park (Southwestern Spain) after a mining accident النص الكامل
2013
Alvárez, C Rodríguez | Moreno, M Jiménez | Alonso, L López | Gómara, B. | Bernardo, F. J Guzmán | Martín-Doimeadios, R. C Rodríguez | González, M. J.
Mercury, methylmercury, and selenium in blood of bird species from Doñana National Park (Southwestern Spain) after a mining accident النص الكامل
2013
Alvárez, C Rodríguez | Moreno, M Jiménez | Alonso, L López | Gómara, B. | Bernardo, F. J Guzmán | Martín-Doimeadios, R. C Rodríguez | González, M. J.
Total mercury (Hg), monomethylmercury (MeHg), and selenium (Se) were determined in blood of 11 bird species living in Doana National Park (DNP, Southwestern Spain) and the surrounding area in 1999 and 2000 after a mine spill accident. The total Hg contents found varied from 1.00 to 587 ng/mL, with an MeHg percentage higher than 80 %, except in mallard species. In all the cases, the concentrations found were below the threshold of high risk for the bird populations. The parameters which most affected the accumulation of Hg and MeHg in the birds studied were, first, species, or trophic position, and second sampling area. Age does not seem to have a great influence on the content of Hg in the blood of these birds. The levels of Se found ranged from 108 to 873 ng/mL, and they were not affected by species, trophic level, age, or sampling area. The blood Hg concentrations of birds living in the area directly affected by the toxic mud, outside the park, were higher than those found in the other birds, and this could be explained by the mine spill accident happened in 1998.
اظهر المزيد [+] اقل [-]Mercury, methylmercury, and selenium in blood of bird species from Doñana National Park (Southwestern Spain) after a mining accident النص الكامل
2013
Rodríguez Álvarez, Carolina | Lopez Alonso, Laura | Gomara Moreno, Belen | Gonzalez Carlos, Maria Jose | Jiménez Moreno, María | Guzmán Bernardo, Francisco Javier | Rodríguez Martín-Doimeadios, Rosa del Carmen
Total mercury (Hg), monomethylmercury (MeHg), and selenium (Se) were determined in blood of 11 bird species living in Doñana National Park (DNP, Southwestern Spain) and the surrounding area in 1999 and 2000 after a mine spill accident. The total Hg contents found varied from 1.00 to 587 ng/mL, with an MeHg percentage higher than 80 %, except in mallard species. In all the cases, the concentrations found were below the threshold of high risk for the bird populations. The parameters which most affected the accumulation of Hg and MeHg in the birds studied were, first, species, or trophic position, and second sampling area. Age does not seem to have a great influence on the content of Hg in the blood of these birds. The levels of Se found ranged from 108 to 873 ng/mL, and they were not affected by species, trophic level, age, or sampling area. The blood Hg concentrations of birds living in the area directly affected by the toxic mud, outside the park, were higher than those found in the other birds, and this could be explained by the mine spill accident happened in 1998.
اظهر المزيد [+] اقل [-]A detailed investigation of ambient aerosol composition and size distribution in an urban atmosphere النص الكامل
2013
Kuzu, S Levent | Saral, Arslan | Demir, Selami | Summak, Gülsüm | Demir, Göksel
This research was executed between March 2009 and March 2010 to monitor particulate matter size distribution and its composition in Istanbul. Particulate matter composition was determined using ion chromatography and inductively coupled plasma optical emission spectrometry. The sampling point is adjacent to a crowded road and the Bosporus Strait. Two prevailing particulate modes are found throughout PM₁₀ by sampling with a nine-stage low-volume cascade impactor. First mode in the fine mode is found to be between 0.43 and 0.65 μm, whereas the other peak was observed between 3.3 and 4.7 μm, referring to the coarse mode. The mean PM₁₀ concentration was determined as 41.2 μg/m³, with a standard deviation of 16.92 μg/m³. PM₀.₄₃ had the highest mean concentration value of 10.67 μg/m³, making up nearly one fourth of the total PM₁₀ mass. For determining the effect of traffic on particulate matter (PM) composition and distribution, four different sampling cycles were applied: entire day, nighttime, rush hour, and rush hour at weekdays. SO ₄ ⁻² and organic carbon/elemental carbon proportions are found to be lower in night samples, representing a decrease in traffic. The long-range transports of dust storms were observed during the sampling periods. Their effects were determined analytically and their route models were run by the HYSPLIT model and validated through satellite photographs taken by the NASA Earth Observatory.
اظهر المزيد [+] اقل [-]Synergistic effects caused by atrazine and terbuthylazine on chlorpyrifos toxicity to early-life stages of the zebrafish Danio rerio النص الكامل
2013
Pérez, Joanne | Domingues, Inês | Monteiro, Marta | Soares, Amadeu M. V. M. | Loureiro, Susana
Synergistic effects caused by atrazine and terbuthylazine on chlorpyrifos toxicity to early-life stages of the zebrafish Danio rerio النص الكامل
2013
Pérez, Joanne | Domingues, Inês | Monteiro, Marta | Soares, Amadeu M. V. M. | Loureiro, Susana
This study examined the effects of three widely used pesticides that have been previously detected in aquatic systems neighbouring agricultural fields on the early-life stages of the zebrafish Danio rerio. Tests involving single exposures and binary combinations of the s-triazine herbicides (atrazine and terbuthylazine) and the organophosphate insecticide chlorpyrifos were performed. Several endpoints, such as swimming behaviour, morphological abnormalities and mortality, were studied. In addition, the inhibition of acetylcholinesterase (AChE) activity was investigated in order to evaluate the mode of action and toxicity of chlorpyrifos in the presence of these herbicides. Results indicate that both binary mixtures elicited synergistic responses on the swimming behaviour of zebrafish larvae. Moreover, although the herbicides were not effective inhibitors of the AChE on their own, a synergistic inhibition of the enzyme activity was obtained by exposure to mixtures with chlorpyrifos. We observed a correlation between impairment of swimming behaviour of the larvae and inhibition of AChE activity. This study supports previous studies concerning the risk assessment of mixtures since the toxicity may be underestimated when looking only at the single toxicants and not their mixtures.
اظهر المزيد [+] اقل [-]Synergistic effects caused by atrazine and terbuthylazine on chlorpyrifos toxicity to early-life stages of the zebrafish Danio rerio النص الكامل
2013
Pérez, Joanne | Domingues, Inês | Monteiro, Marta | Soares, Amadeu M. V. M. | Loureiro, Susana
This study examined the effects of three widely used pesticides that have been previously detected in aquatic systems neighbouring agricultural fields on the early-life stages of the zebrafish Danio rerio. Tests involving single exposures and binary combinations of the s-triazine herbicides (atrazine and terbuthylazine) and the organophosphate insecticide chlorpyrifos were performed. Several endpoints, such as swimming behaviour, morphological abnormalities and mortality, were studied. In addition, the inhibition of acetylcholinesterase (AChE) activity was investigated in order to evaluate the mode of action and toxicity of chlorpyrifos in the presence of these herbicides. Results indicate that both binary mixtures elicited synergistic responses on the swimming behaviour of zebrafish larvae. Moreover, although the herbicides were not effective inhibitors of the AChE on their own, a synergistic inhibition of the enzyme activity was obtained by exposure to mixtures with chlorpyrifos. We observed a correlation between impairment of swimming behaviour of the larvae and inhibition of AChE activity. This study supports previous studies concerning the risk assessment of mixtures since the toxicity may be underestimated when looking only at the single toxicants and not their mixtures. | This study was supported by a PhD grant (SFRH/BD/62818/2009) attributed to Joanne Rodríguez Pérez and by the Pos-Doc grants attributed to Marta Monteiro (SFRH/BPD/45911/ 2008) and Inês Domingues (SFRH/PPD/31752/2006) by the Portuguese Science and Technology Foundation (FCT), funding by FEDER through COMPETE e Programa Operacional Factores de Competitividade and by National funding through Fundação para a Ciência e Tecnologia (FCT), within the research project FUTRICA—Chemical Flow in an Aquatic TRophic Chain (FCOMP-01-0124-FEDER008600; Ref. FCT PTDC/AAC-AMB/104666/2008). Theauthors would like to acknowledge Ana Catarina Bastos for the revision of the English language. | published
اظهر المزيد [+] اقل [-]Distribution and accumulation of elements (As, Cu, Fe, Hg, Mn, and Zn) in tissues of fish species from different trophic levels in the Danube River at the confluence with the Sava River (Serbia) النص الكامل
2013
Subotić, S. | Višnjić Jeftić, Ž | Spasić, S. | Hegediš, A. | Krpo-Ćetković, J. | Lenhardt, M.
Pikeperch (Sander lucioperca), European catfish (Silurus glanis), common carp (Cyprinus carpio), and gobies (Neogobius gymnotrachelus, Neogobius melanostomus) were collected from the Danube River (Belgrade section), and samples of liver, muscle, or whole-body composites (in the case of gobies) were analyzed for As, Cu, Fe, Hg, Mn, and Zn with inductively coupled plasma optical spectrometry to find out if there was a correlation between accumulation of these elements in predatory and prey species, as well as in pairs of species with overlapping diets. Concentrations of all analyzed elements were either higher (Cu, Fe, Mn, Zn) in liver than in muscle, or equal (As, Hg), except for Hg in carp, which was higher in muscle. Mercury concentration in liver and muscle of predators (catfish, pikeperch) was significantly (<10⁻⁴) higher than in prey fishes (carp and gobies). The results indicate that Hg concentration was biomagnified through the food chain. Concentrations of As, Fe, and Hg in carp liver and gobies whole-body composite were similar, but carp had significantly (<10⁻⁴) higher values of Zn and Cu in liver. The regression analysis and trendline equations indicate that the concentrations of all tested elements, except for As in liver, and Mn and Fe in muscle, were similar in predatory fish (pikeperch and catfish), on one hand, and in prey fish (carp and gobies), on the other hand. Distinctly high Zn concentration in carp is very common in this species due to its physiology. Concentrations of Hg and Zn were higher than the maximum acceptable concentration due to the high pollution level in this section of the Danube River, accordingly posing a risk for the human consumption of these fish species.
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