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- Every, Hayley A, et al.
(författare)
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Room temperature fast-ion conduction in imidazolium halide salts
- 2001
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Ingår i: Journal of Materials Chemistry Articles. - : Royal Society of Chemistry (RSC). - 0959-9428 .- 1364-5501. ; 11:3031-6
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Tidskriftsartikel (refereegranskat)abstract
- Fast-ion conduction has been observed in the iodide and bromide salts of 1-methyl-3-ethylimidazolium at ambient temperatures. The melting point of these two compounds is above 350 K and even at 273 K the ionic conductivity in the solid-state is greater than 10–3S cm–1. Cation diffusion coefficients have been measured using fringe field gradient and/or pulse field gradient 1H NMR techniques, which indicated cation diffusion coefficients of the order of 10–10 m2 s–1 in the solid-state. Remarkably, these values are up to an order of magnitude higher than the cation diffusion coefficient in the supercooled liquid at 293 K. The activation energy for diffusion in the solid-state is extremely small, as is typical of solid-state fast-ion conductors and indicates a change in transport mechanism from the melt to the crystal. The inability to detect an 127I signal together with the modelling of the conductivity using the Nernst–Einstein equation suggests that the solid-state conduction is primarily due to cation diffusion. The solid-state fast-ion conduction is most likely related to vacancy diffusion along the cation layers in the crystal. The temperature dependence of the NMR signal intensity indicates that the number of mobile species is increasing with increasing temperature with an activation energy of approximately 20–30 kJ mol–1.
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| 4. |
- Landberg, Tommy, et al.
(författare)
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Differences in oxidative stress in heavy metal resistant and sensitive clones of Salix viminalis
- 2002
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Ingår i: Journal of plant physiology (Print). - : Elsevier BV. - 0176-1617 .- 1618-1328. ; 159:1, s. 69-75
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Tidskriftsartikel (refereegranskat)abstract
- Many stress mechanisms, such as antioxidative mechanisms, are known to be activated by heavy metals. The aim of this work was to investigate whether oxidative stress and related mechanisms were expressed differently in plants with different resistances to heavy metals. Different clones of Salix viminalis with different resistances to Cd, Cu, and Zn were cultivated hydroponically in the presence of 7 μmol/L Cd, 3 μmol/L Cu or 70 μmol/L Zn for 20 days. The clones were then compared with regard to the concentrations of free radicals, estimated by measuring thiobarbituric acid-reactive material (TBA-rm) and glutathione (GSH). The activity of the enzymes, aspartate peroxidase (APX), guaiacol peroxidase (GPX), superoxide dismutase (SOD), and catalase (CAT) was also analysed. Salicylic acid was also measured since it is known to be involved in antioxidative activities.The results showed that some differences could be observed between resistant and sensitive clones. The SOD activity was higher in untreated resistant clones compared with the sensitive ones. Under metal treatment, however, the SOD activity was similar. Furthermore, TBA-rm was higher in shoots of resistant clones compared to sensitive ones, while the opposite was found in roots.
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| 5. |
- Landberg, Tommy, et al.
(författare)
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Interclonal variation of heavy metal interactions inSalix viminalis
- 2002
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Ingår i: Environmental Toxicology and Chemistry. - : Wiley. - 0730-7268 .- 1552-8618. ; 21:12, s. 2669-2674
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Tidskriftsartikel (refereegranskat)abstract
- In the complex chemistry of soil, interactions between metals can be expected and these affect the uptake of the metals by the plants. The role of the metal–metal interaction may vary between different plants. This study was performed to investigate if variations exist in the interactions between Cd, Cu, and Zn on toxicity and accumulation of these metals in different clones of Salix viminalis. Two studies were performed. First, to study interaction at uptake, 10 clones with high or low accumulation capacity of Cd, Cu, and Zn, respectively, were treated with 0.3 μM Cd, 0.1 μM Cu, and 3 μM Zn (all three metals at the same time or separately). Second, to study the effect of one of the metals on the sensitivity of the plant to the other metals, three clones with high or low sensitivity to each of the three metals were used in a modified Weibull analysis. Examination of the results shows that interclonal variation exists in effects of metal interaction on metal accumulation and sensitivity exists. The uptake experiment showed that accumulation of Cu was decreased by the other metals, but only in clones with high Cu-accumulating properties because of decreased net uptake of Cu. The accumulation of Zn in roots was increased two- to threefold in all clones in the presence of the other metals because of a decreased translocation of Zn to the shoot. The accumulation of Cd was not changed by the presence of the other metals in any of the clones. The second experiment showed that the effect of interactions between the different metals on metal toxicity was present in all clones but appeared most frequently in the clone with high Zn resistance. Synergistic effects between Cu and Zn in the Zn-resistant clone suggested that this clone had evolved an additional site of toxic action that was absent in the other clones.
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| 6. |
- Landberg, Tommy, et al.
(författare)
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No phytochelatin (PC2 and PC3) detected in Salix viminalis
- 2004
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Ingår i: Physiologia Plantarum. - : Wiley. - 0031-9317 .- 1399-3054. ; 121:3, s. 481-487
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Tidskriftsartikel (refereegranskat)abstract
- Phytochelatins (PCs) have been detected in a large range of plant species, but their role in heavy-metal tolerance is unclear. Various clones of Salix viminalis are differently tolerant to heavy metals, and the aim of this work was to investigate whether PCs were differently expressed in tolerant compared with sensitive clones. In a long-term study, five clones with high or low metal tolerance were cultivated 21 days without or with Cd (1 or 10 µM), Cu (0.3 or 7 µM), Ni (15 µM), Pb (7 µM) or Zn (10 or 100 µM). Controls were further used in a short-term study where Cd (1 µM) was added and samples were collected 0, 15 and 30 min, 1, 3 and 24 h after start of treatment. PCs were analysed on high performance liquid chromatography (HPLC) using two different methods: post-column derivatization using Ellmans reagent and pre-derivatization with monobromobimane. Thlaspi caerulescens treated with Cd was used as internal PC standard. No PCs could be detected in Salix with either of the two methods in any of the treatments: different clones, metals, concentrations, plant parts or treatment time. The 16 thiol peaks shown were the same in both control and treated plants. Both HPLC methods showed PC peaks when Thlaspi was used but these peaks could not be associated with any of the 16 peaks. The amino acid composition of the 16 peaks was not the expected composition of that of PCs. Thus, Salix viminalis have no detectable levels of PCs, which in turn are not involved in heavy metal tolerance in Salix
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| 9. |
- Stoltz, Eva, 1973-
(författare)
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Phytostabilisation : use of wetland plants to treat mine tailings
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Mine tailings can be rich in sulphide minerals and may form acid mine drainage (AMD) through reaction with atmospheric oxygen and water. AMD contains elevated levels of metals and arsenic (As) that could be harmful to animals and plants. An oxygen-consuming layer of organic material and plants on top of water-covered tailings would probably reduce oxygen penetration into the tailings and thus reduce the formation of AMD. However, wetland plants have the ability to release oxygen through the roots and could thereby increase the solubility of metals and As. These elements are released into the drainage water, taken up and accumulated in the plant roots, or translocated to the shoots. The aim was to examine the effects of plant establishment on water-covered mine tailings by answering following questions: A) Is plant establishment on water-covered mine tailings possible? B) What are the metal and As uptake and translocation properties of these plants? C) How do plants affect metal and As release from mine tailings, and which are the mechanisms involved?Carex rostrata Stokes, Eriophorum angustifolium Honck., E. scheuchzeri Hoppe, Phragmites australis (Cav.) Steud., Salix phylicifolia L. and S. borealis Fr. were used as test plants. Influences of plants on the release of As, Cd, Cu, Pb, Zn and in some cases Fe in the drainage water, and plant element uptake were studied in greenhouse experiments and in the field. The results obtained demonstrate that plant establishment are possible on water-covered unweathered mine tailings, and a suitable amendment was found to be sewage sludge. On acidic, weathered tailings, a pH increasing substance such as ashes should be added to improve plant establishment. The metal and As concentrations of the plant tissue were found to be generally higher in roots than in shoots. The uptake was dependent on the metal and As concentrations of the tailings and the release of organic acids from plant roots may have influenced the uptake. The metal release from tailings into the drainage water caused by E. angustifolium was found to depend greatly on the age and chemical properties of the tailings. However, no effects of E. angustifolium on As release was found. Water from old sulphide-, metal- and As-rich tailings with low buffering capacity were positively affected by E. angustifolium by causing higher pH and lower metal concentrations. In tailings with relatively low sulphide, metal and As contents combined with a low buffering capacity, plants had the opposite impact, i.e. a reduction in pH and elevated metal levels of the drainage water. The total release of metal and As from the tailings, i.e. drainage water together with the contents in shoots and roots, was found to be similar for C. rostrata, E. angustifolium and P. australis, except for Fe and As, where the release was highest for P. australis. The differences in metal and As release from mine tailings were mainly found to be due to the release of O2 from the roots, which changes the redox potential. Release of organic acids from the roots slightly decreased the pH, although did not have any particular influence on the release of metal and As. In conclusion, as shown here, phytostabilisation may be a successful technique for remediation of mine tailings with high element and sulphide levels, and low buffering capacity.
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