خيارات البحث
النتائج 221 - 230 من 1,310
Oxidation of bisphenol F (BPF) by manganese dioxide النص الكامل
2011
Bisphenol F (BPF), an environmental estrogen, is used as a monomer in plastic industry and its environmental fate and decontamination are emerging concern. This study focused on the kinetics, influencing factors and pathways of its oxidation by MnO₂. At pH 5.5, about 90% of BPF was oxidized in 20min in a solution containing 100μM MnO₂ and 4.4μM BPF. The reaction was pH-dependent, following an order of pH 4.5>pH 5.5>pH 8.6>pH 7.5>pH 6.5>pH 9.6. Humic acids inhibited the reaction at low (≤pH 5.5) and high pH (≥pH 8.6) at high concentrations. In addition, metal ions and anions also suppressed the reaction, following the order Mn²⁺>Ca²⁺>Mg²⁺>Na⁺ and HPO₄ ²⁻>Cl⁻>NO₃ ⁻≈SO₄ ²⁻, respectively. A total of 5 products were identified, from which a tentative pathway was proposed.
اظهر المزيد [+] اقل [-]Reporting and evaluation criteria as means towards a transparent use of ecotoxicity data for environmental risk assessment of pharmaceuticals النص الكامل
2011
Ågerstrand, M. | Küster, A. | Bachmann, J. | Breitholtz, M. | Ėbert, I. | Rechenberg, B. | Rudén, C.
Ecotoxicity data with high reliability and relevance are needed to guarantee the scientific quality of environmental risk assessments of pharmaceuticals. The main advantages of a more structured approach to data evaluation include increased transparency and predictability of the risk assessment process, and the possibility to use non-standard data. In this collaboration, between the research project MistraPharma and the German Federal Environment Agency, a new set of reporting and evaluation criteria is presented and discussed. The new criteria are based on the approaches in the literature and the OECD reporting requirements, and have been further developed to include both reliability and relevance of test data. Intended users are risk assessors and researchers performing ecotoxicological experiments, but the criteria can also be used for education purposes and in the peer-review process for scientific papers. This approach intends to bridge the gap between the regulator and the scientist’s needs and way of work.
اظهر المزيد [+] اقل [-]Reproduction and biochemical responses in Enchytraeus albidus (Oligochaeta) to zinc or cadmium exposures النص الكامل
2011
Novais, Sara C. | Gomes, Susana I.L. | Gravato, Carlos | Guilhermino, Lúcia | Coen, Wim De | Soares, Amadeu M.V.M. | Amorim, Mónica J.B.
Reproduction and biochemical responses in Enchytraeus albidus (Oligochaeta) to zinc or cadmium exposures النص الكامل
2011
Novais, Sara C. | Gomes, Susana I.L. | Gravato, Carlos | Guilhermino, Lúcia | Coen, Wim De | Soares, Amadeu M.V.M. | Amorim, Mónica J.B.
To better understand chemical modes of action, emphasis has been given to stress responses at lower levels of biological organization. Cholinesterases and antioxidant defenses are among the most used biomarkers due to their crucial role in the neurocholinergic transmission and in cell homeostasis preventing DNA damage, enzymatic inactivation and lipid peroxidation. The main goal of this study was to investigate the effects of zinc and cadmium on survival and reproduction of E. albidus and to assess metals oxidative stress potential and neurotoxic effects at concentrations that affected reproduction. Both metals affected the enchytraeids’ survival and reproduction and induced significant changes in the antioxidant defenses as well as increased lipid peroxidation, indicating oxidative damage. This study demonstrates that determining effects at different levels of biological organization can give better information on the physiological responses of enchytraeids in metal contamination events and further unravel the mechanistic processes dealing with metal stress.
اظهر المزيد [+] اقل [-]Reproduction and biochemical responses in Enchytraeus albidus (Oligochaeta) to zinc or cadmium exposures النص الكامل
1000 | 2011
Novais, Sara C. | Gomes, Susana I. L. | Gravato, Carlos | Guilhermino, Lúcia | De Coen, Wim | Soares, Amadeu M. V. M. | Amorim, Mónica J. B.
To better understand chemical modes of action, emphasis has been given to stress responses at lower levels of biological organization. Cholinesterases and antioxidant defenses are among the most used biomarkers due to their crucial role in the neurocholinergic transmission and in cell homeostasis preventing DNA damage, enzymatic inactivation and lipid peroxidation. The main goal of this study was to investigate the effects of zinc and cadmium on survival and reproduction of E. albidus and to assess metals oxidative stress potential and neurotoxic effects at concentrations that affected reproduction. Both metals affected the enchytraeids' survival and reproduction and induced significant changes in the antioxidant defenses as well as increased lipid peroxidation, indicating oxidative damage. This study demonstrates that determining effects at different levels of biological organization can give better information on the physiological responses of enchytraeids in metal contamination events and further unravel the mechanistic processes dealing with metal stress. (C) 2011 Elsevier Ltd. All rights reserved.
اظهر المزيد [+] اقل [-]The application of zero-water discharge system in treating diffuse village wastewater and its benefits in community afforestation النص الكامل
2011
Wu, Yonghong | Xia, Lizhong | Hu, Zhengyi | Liu, Shuzhi | Liu, Hongbin | Nath, Bibhash | Zhang, Naiming | Yang, Linzhang
The proposed on-site zero-water discharge system was comprised of four main components: anaerobic tank, aerobic bioreactor, activated soil filter and water-collecting well. The results demonstrate that at 350 m³ day⁻¹ of hydraulic load, the system can effectively remove pollutants from the wastewater, e.g., 86% removal of COD; 87% removal of SS; 80% removal of TP and 71% removal of TN. The growth states of the grasses, macrophytes and arbors in the activated soil filter were better than the control. The life of the activated soil filter was estimated to be ∼12–15 yrs, based on the laboratory microcosm studies. However, humic acid contents and soil porosity have suggested that the activated soil filter was able to regenerate itself and thereby prolonging its life by reducing clogging of the pores. The results suggest that the zero-water discharge system was a promising bio-measure in treating diffuse village wastewater and benefiting community afforestation.
اظهر المزيد [+] اقل [-]Uptake and translocation of arsenite by Pteris vittata L.: Effects of glycerol, antimonite and silver النص الكامل
2011
Mathews, Shiny | Rathinasabapathi, Bala | Ma, Lena Q.
AsIII uptake in living cells is through aquaglyceroporin transporters, but it is unknown in arsenic-hyperaccumulator Pteris vittata. We investigated the effects of AsIII analogs glycerol and antimonite (SbIII) at 0–100 mM and aquaporin inhibitor AgNO₃ at 0–0.1 mM on the uptake of 0.1 mM AsIII or AsV by P. vittata over 1–2 h. Glycerol or SbIII didn’t impact AsIII or AsV uptake by P. vittata (p < 0.05), with As concentrations in the fronds and roots being 4.4–6.3 and 3.9–6.2 mg/kg. However, 0.01 mM AgNO₃ reduced As concentrations in the fronds and roots by 64% and 58%. Hence, AsIII uptake in P. vittata might be via an aquaporin transporter different from glycerol and SbIII transporters. Further as AsIII analogs and aquaporin inhibitor had no impact on AsV uptake, AsIII and AsV were likely taken up by different transporters in P. vittata. Our results imply a different AsIII transporter in P. vittata from other plants.
اظهر المزيد [+] اقل [-]Geographic variation in tissue accumulation of endocrine disrupting compounds (EDCs) in grazing sheep النص الكامل
2011
Rhind, S.M. | Kyle, C.E. | Mackie, C. | Yates, K. | Duff, E.I.
Muscle tissue was collected from ewes and lambs derived from farms throughout Scotland and sample concentrations of five endocrine disrupting compound groups were determined. Farms of origin were categorised according to geographic region. There were few statistically-significant differences with region or distance from cities. However, the magnitude of the difference between the highest and lowest mean values in ewe muscle from different regions exceeded 30% for 13 of the 15 compounds that were consistently detected in muscle, with animals derived from the industrialised region having the highest mean values for 11 of the 13 compounds. A less marked trend was apparent in the lamb muscle (8 of 13 highest were in the industrialised region). The physiological effects of such small differences in exposure to mixtures of pollutants remain to be determined.
اظهر المزيد [+] اقل [-]Polybrominated diphenyl ethers (PBDEs) in soils along a rural-urban-rural transect: Sources, concentration gradients, and profiles النص الكامل
2011
Gevao, Bondi | Ghadban, Abdul Nabi | Uddin, Saif | Jaward, Foday M. | Bahloul, Majed | Zafar, Jamal
This study reports concentrations of PBDEs in surface soil samples collected along a 140km transect across Kuwait to assess the role of urban centers as sources of persistent organic pollutants to the surrounding environment. The ΣPBDE concentrations varied by a factor of ∼250 and ranged from 289 to 80,078pgg⁻¹d.w. The concentrations of PBDEs in Kuwait City were significantly higher (p<0.01) than those collected from sites outside the city supporting the hypothesis that urban centers are sources of PBDEs. The congener profiles were dominated by BDE-209, accounting for 93% of the PBDEs in the soil samples. The concentrations of all congeners (except BDE-209) were highly correlated with percent organic carbon (%OC) (p>0.05) when the data from Kuwait City was omitted from the analysis. These findings suggest that soil concentrations outside the urban centers were close to equilibrium with the atmosphere.
اظهر المزيد [+] اقل [-]XAFS study of starch-stabilized magnetite nanoparticles and surface speciation of arsenate النص الكامل
2011
Zhang, Meiyi | Pan, Gang | Zhao, Dongye | He, Guangzhi
It has been shown that starch can effectively stabilize nanoscale magnetite particles, and starch-stabilized magnetite nanoparticles (SMNP) are promising for in situ remediation of arsenic-contaminated soils. However, a molecular level understanding has been lacking. Here, we carried out XAFS studies to bridge this knowledge gap. Fe K-edge XAFS spectra indicated that the Fe–O and Fe–Fe coordination numbers of SMNP were lower than those for bare magnetite particles, and these coordination numbers decreased with increasing starch concentration. The decrease in the average coordination number at elevated stabilizer concentration was attributed to the increase in the surface-to-volume ratio. Arsenic K-edge XAFS spectra indicated that adsorbed arsenate on SMNP consisted primarily of binuclear bidentate (BB) complexes and monodentate mononuclear (MM) complexes. More BB complexes (energetically more favorable) were observed at higher starch concentrations, indicating that SMNP not only offered greater adsorption surface area, but also stronger adsorption affinity toward arsenate.
اظهر المزيد [+] اقل [-]The effects of tertiary treated municipal wastewater on fish communities of a small river tributary in Southern Ontario, Canada النص الكامل
2011
Brown, Carolyn J.M. | Knight, Brendan W. | McMaster, Mark E. | Munkittrick, Kelly R. | Oakes, Ken D. | Tetreault, Grald R. | Servos, Mark R.
Fish community changes associated with a tertiary treated municipal wastewater effluent outfall in the Speed River, Ontario, Canada, were evaluated at nine sites over two seasons (2008) using standardized electrofishing. Habitat evaluations were conducted to ensure that the riffle sites selected were physically similar. The fish community was dominated by several species of darters that differed in their response to the effluent outfall. There was a significant decrease in Greenside Darter (Etheostoma blennioides) but an increase in Rainbow Darter (E. caeruleum) abundance directly downstream of the outfall. Stable isotope signatures (δ¹³C and δ¹⁵N), which indicate shifts in energy utilization and flow, increased in Rainbow Darter downstream, but showed no change in Greenside Darter. Rainbow Darter may be exploiting a food source that is not as available at upstream sites giving them a competitive advantage over the Greenside Darter immediately downstream of the outfall.
اظهر المزيد [+] اقل [-]Detection of fullerenes (C₆₀ and C₇₀) in commercial cosmetics النص الكامل
2011
Benn, Troy M. | Westerhoff, Paul | Herckes, Pierre
Detection methods are necessary to quantify fullerenes in commercial applications to provide potential exposure levels for future risk assessments of fullerene technologies. The fullerene concentrations of five cosmetic products were evaluated using liquid chromatography with mass spectrometry to separate and specifically detect C₆₀ and C₇₀ from interfering cosmetic substances (e.g., castor oil). A cosmetic formulation was characterized with transmission electron microscopy, which confirmed that polyvinylpyrrolidone encapsulated C₆₀. Liquid-liquid extraction of fullerenes from control samples approached 100% while solid-phase and sonication in toluene extractions yielded recoveries of 27–42%. C₆₀ was detected in four commercial cosmetics ranging from 0.04 to 1.1 μg/g, and C₇₀ was qualitatively detected in two samples. A single-use quantity of cosmetic (0.5 g) may contain up to 0.6 μg of C₆₀, demonstrating a pathway for human exposure. Steady-state modeling of fullerene adsorption to biosolids is used to discuss potential environmental releases from wastewater treatment systems.
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