Ni Concentration (ni + concentration)

Distribution by Scientific Domains


Selected Abstracts


Uptake and depuration of cadmium, nickel, and lead in laboratory-exposed Tubifex tubifex and corresponding changes in the concentration of a metallothionein-like protein

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 1 2004
Patricia L. Gillis
Abstract Based on weight loss in water, 2 4h is recommended for Tubifex tubifex gut clearance. Biota-to-sediment accumulation factors (BSAFs) in gut-cleared T. tubifex following six weeks of exposure to Cd-, Ni-, and Pb-spiked sediment were 12.4, 3.0, and 19.0, respectively. Tissue Ni concentrations peaked after 12 h, whereas Cd and Pb were accumulated for the duration of the exposure. Tubifex tubifex were transferred to either water (24 h) or sediment (10 weeks) to monitor changes in internal metal concentrations. After 24 h in water, only Ni concentration had declined significantly (p < 0.05), suggesting that the majority of Ni was associated with the gut content, while Cd and Pb were accumulated in the tissues. Metal depuration in sediment was described with two-compartment, first-order kinetic models (r2 = 0.7,0.8; p < 0.001), indicating that T. tubifex has both a quickly depurated and a more tightly bound pool of accumulated metal. Tubifex tubifex were also exposed to sediment spiked with just Cd (3.66 ,mol/g). Cadmium uptake and induction of metallothionein-like protein (MTLP) were rapid; both parameters were significantly elevated within 24 h of exposure. Metallothionein-like protein (8.7 ± 1.8 nmol/g) and Cd (60.8 ± 11.0 ,mol/g) reached maximum concentrations after 96 h and four weeks, respectively. [source]


High-nickel insects and nickel hyperaccumulator plants: A review

INSECT SCIENCE, Issue 1 2009
Robert S. Boyd
Abstract Insects can vary greatly in whole-body elemental concentrations. Recent investigations of insects associated with Ni hyperaccumulator plants have identified insects with relatively elevated whole-body Ni levels. Evaluation of the limited data available indicates that a whole-body Ni concentration of 500 ,g Ni/g is exceptional: I propose that an insect species with a mean value of 500 ,g Ni/g or greater, in either larval/nymphal or adult stages, be considered a "high-Ni insect". Using the 500 ,g Ni/g criterion, 15 species of high-Ni insects have been identified to date from studies in Mpumalanga (South Africa), New Caledonia and California (USA). The highest mean Ni concentration reported is 3 500 ,g Ni/g for nymphs of a South African Stenoscepa species (Orthoptera: Pyrgomorphidae). The majority of high-Ni insects (66%) are heteropteran herbivores. Studies of high-Ni insect host preference indicate they are monophagous (or nearly so) on a particular Ni hyperaccumulator plant species. Much of the Ni in bodies of these insects is in their guts (up to 66%,75%), but elevated levels have also been found in Malpighian tubules, suggesting efficient elimination as one strategy for dealing with a high-Ni diet. Tissue levels of Ni are generally much lower than gut concentrations, but up to 1200 ,g Ni/g has been reported from exuviae, suggesting that molting may be another pathway of Ni elimination. One ecological function of the high Ni concentration of these insects may be to defend them against natural enemies, but to date only one experimental test has supported this "elemental defense" hypothesis. Community-level studies indicate that high-Ni insects mobilize Ni into food webs but that bioaccumulation of Ni does not occur at either plant-herbivore or herbivore-predator steps. Unsurprisingly, Ni bioaccumulation indices are greater for high-Ni insects compared to other insect species that feed on Ni hyperaccumulator plants. There is some evidence of Ni mobilization into food webs by insect visitors to flowers of Ni hyperaccumulator plants, but no high-Ni insect floral visitors have been reported. [source]


Metal concentrations of insects associated with the South African Ni hyperaccumulator Berkheya coddii (Asteraceae)

INSECT SCIENCE, Issue 2 2006
ROBERT S. BOYD
Abstract The high levels of some metals in metal hyperaccumulator plants may be transferred to insect associates. We surveyed insects collected from the South African Ni hyperaccumulator Berkheya coddii to document whole-body metal concentrations (Co, Cr, Cu, Mg, Mn, Ni, Pb, Zn). We also documented the concentrations of these metals in leaves, stems and inflorescences, finding extremely elevated levels of Ni (4 700,16 000 ,g/g) and high values (5,34 ,g/g) for Co, Cr, and Pb. Of 26 insect morphotypes collected from B. coddii, seven heteropterans, one coleopteran, and one orthopteran contained relatively high concentrations of Ni (> 500 ,g/g). The large number of high-Ni heteropterans adds to discoveries of others (from California USA and New Caledonia) and suggests that members of this insect order may be particularly Ni tolerant. Nymphs of the orthopteran (Stenoscepa) contained 3 500 ,g Ni/g, the greatest Ni concentration yet reported for an insect. We also found two beetles with elevated levels of Mg (> 2 800 ,g/g), one beetle with elevated Cu (> 70 ,g/g) and one heteropteran with an elevated level of Mn (> 200 ,g/g). Our results show that insects feeding on a Ni hyperaccumulator can mobilize Ni into food webs, although we found no evidence of Ni biomagnification in either herbivore or carnivore insect taxa. We also conclude that some insects associated with hyperaccumulators can contain Ni levels that are high enough to be toxic to vertebrates. [source]


Ni clay neoformation on montmorillonite surface

JOURNAL OF SYNCHROTRON RADIATION, Issue 2 2001
Rainer Dähn
Polarized extended X-ray absorption fine structure spectroscopy (P-EXAFS) was used to study the sorption mechanism of Ni on the aluminous hydrous silicate montmorillonite at high ionic strength (0.3 M NaClO4), pH 8 and a Ni concentration of 0.66 mM. Highly textured self-supporting clay films were obtained by slowly filtrating a clay suspension after a reaction time of 14 days. P-EXAFS results indicate that sorbed Ni has a Ni clay-like structural environment with the same crystallographic orientation as montmorillonite layers. [source]


Thermal histories of IVA iron meteorites from transmission electron microscopy of the cloudy zone microstructure

METEORITICS & PLANETARY SCIENCE, Issue 3 2009
J. I. GOLDSTEIN
Thin sections for TEM analysis were produced by a focused ion beam instrument. Use of the TEM allowed us to avoid potential artifacts which may be introduced during specimen preparation for SEM analysis of high Ni particles <30 nm in size and to identify microchemical and microstructural changes due to the effects of shock induced reheating. No cloudy zone was observed in five of the eight moderately to highly shocked (>13 GPa) IVA irons that were examined in the TEM. Shock induced reheating has allowed for diffusion from 20 nm to 400 nm across kamacite/taenite boundaries, recrystallization of kamacite, and the formation, in Jamestown, of taenite grain boundaries. In the eleven IVA irons with cloudy zone microstructures, the size of the high-Ni particles in the cloudy zone increases directly with increasing bulk Ni content. Our data and the inverse correlation between cooling rate and high-Ni particle size for irons and stony-irons show that IVA cooling rates at 350-200 °C are inversely correlated with bulk Ni concentration and vary by a factor of about 15. This cooling rate variation is incompatible with cooling in a metallic core that was insulated with a silicate mantle, but is compatible with cooling in a metallic body of radius 150 ± 50 km. The widths of the tetrataenite regions next to the cloudy zone correlate directly with high-Ni particle size providing another method to measure low temperature cooling rates. [source]


Transfer of Cd, Cu, Ni, Pb, and Zn in a soil-plant-invertebrate food chain: A microcosm study,

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 3 2006
Renaud Scheifler
Abstract The transfer of Cd, Cu, Ni, Pb, and Zn was evaluated in a soil-plant (lettuce, Lactuca sativa),invertebrate (snail, Helix aspersa) food chain during a microcosm experiment. Two agricultural soils, polluted and unpolluted, were studied. Lettuce was cultivated for eight weeks before introduction of snails into the microcosms (M-snails). In a parallel experiment, snails were exposed to lettuce only (i.e., without soil) in simpler exposure devices called containers (C-snails). Snail exposure duration was eight weeks for both M- and C-snails. No effects on snail survival were found. Both M- and C-snails exposed to polluted soil showed a growth reduction, but only after two weeks of exposure. Time-dependent accumulation in M-snails exposed to the polluted environment showed a regular increase of Cd and Zn concentrations over time and a rapid increase of Pb concentrations within the first two weeks, which then remained stable. Copper and Ni concentrations did not increase during any of the experiments. Concentrations in M- and C-snails were compared to estimate the relative contribution of soil and plant to the total bioaccumulation. The results suggest that the soil contribution may be higher than 80% for Pb, from 30 to 60% for Zn, and from 2 to 40% for Cd. [source]


Uptake and depuration of cadmium, nickel, and lead in laboratory-exposed Tubifex tubifex and corresponding changes in the concentration of a metallothionein-like protein

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 1 2004
Patricia L. Gillis
Abstract Based on weight loss in water, 2 4h is recommended for Tubifex tubifex gut clearance. Biota-to-sediment accumulation factors (BSAFs) in gut-cleared T. tubifex following six weeks of exposure to Cd-, Ni-, and Pb-spiked sediment were 12.4, 3.0, and 19.0, respectively. Tissue Ni concentrations peaked after 12 h, whereas Cd and Pb were accumulated for the duration of the exposure. Tubifex tubifex were transferred to either water (24 h) or sediment (10 weeks) to monitor changes in internal metal concentrations. After 24 h in water, only Ni concentration had declined significantly (p < 0.05), suggesting that the majority of Ni was associated with the gut content, while Cd and Pb were accumulated in the tissues. Metal depuration in sediment was described with two-compartment, first-order kinetic models (r2 = 0.7,0.8; p < 0.001), indicating that T. tubifex has both a quickly depurated and a more tightly bound pool of accumulated metal. Tubifex tubifex were also exposed to sediment spiked with just Cd (3.66 ,mol/g). Cadmium uptake and induction of metallothionein-like protein (MTLP) were rapid; both parameters were significantly elevated within 24 h of exposure. Metallothionein-like protein (8.7 ± 1.8 nmol/g) and Cd (60.8 ± 11.0 ,mol/g) reached maximum concentrations after 96 h and four weeks, respectively. [source]


Mobilization of metals from uranium mine waste: the role of pyoverdines produced by Pseudomonas fluorescens

GEOBIOLOGY, Issue 4 2010
F. EDBERG
Microorganisms produce chelating agents, such as siderophores and other ligands, which allow them to mobilize and scavenge essential elements from the environment when bioavailability is low. To better understand the effects of biologically mediated leaching of metals from mine waste, Pseudomonas fluorescens was cultivated in the presence of processed ore from the former uranium mine in Ranstad, southern Sweden. Light conditions, the concentration of the mineral source and oxygen availability were varied. The presence of ore in the culture flasks enhanced bacterial growth and raised the pH of the culture medium. Increasing the amount of ore or enhancing aeration of the medium further encouraged cell growth and pH rise. Bacteria mobilized Fe, Ni and Co from the ore. Fe-siderophore complexes were detected and estimated to be present at approximately 9 ,m. In the presence of bacteria and light, dissolved Fe and U concentrations were higher compared to dark conditions. Increasing the amount of ore resulted in higher dissolved Ni concentrations but lower dissolved Fe, most likely due to precipitate formation. Data from this study support siderophore production by bacteria that allowed mobilization of essential nutrients from the processed ore. However, the availability of potentially toxic metals like Ni and U may also be enhanced. Microbial-promoted mobilization could contribute to leaching of toxic metals in current and historic mining areas. This process should be considered during design and implementation of remediation projects where trace metals are of environmental concern. [source]