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At least 991 records · Page 55Linked to original sources
PubMed2005

A link between lead and cadmium kinetic speciation in seawater and accumulation by the green alga Ulva lactuca.

In this work, studies on the bioaccumulation of Cd and Pb by Ulva lactuca at different sites of Gulf San Jorge (Patagonia, Argentina) are presented. Higher values of bioaccumulated Cd were found in Punta Maqueda - a site believed to serve as a control - in comparison to those in Punta Borja, a place highly exposed to urban and industrial activities. Consequently; the labile fractions of Cd and Pb in seawater were determined with a flow injection-preconcentration manifold interfaced to a graphite furnace-atomic absorption spectrometer (FI-GFAAS). The results obtained by kinetic speciation showed that the variable that correctly explains heavy metals accumulation in the alga, is the labile metal fraction in seawater. We propose to use an enhancement ratio - on the basis of the kinetically labile metal fraction - for calculation of the metal accumulated by the alga relative to its environment.

Argentina↗
PubMed2005

Physicochemical characterization and mercury speciation of particle-size soil fractions from an abandoned mining area in Mieres, Asturias (Spain).

Soils from old cinnabar mining areas usually exhibit high Hg contents, whose mobility depends on soil parameters and environmental conditions. This paper presents the study of the Hg speciation in soil samples from an abandoned Hg mine and metallurgical plant in Mieres (Asturias, Spain), in relation to their mineralogical and chemical composition and their particle-size distribution. A characterization of samples was made by X-Ray Diffraction Spectrometry, Scanning Electron Microscopy and Atomic Absorption and Emission Spectroscopy analyses. A sequential extraction method was applied to establish Hg mobility in the samples and their grain-size subsamples. The highest Hg mobility was found in well-developed soils, as a consequence of the adsorption processes by iron and manganese oxides, whereas in those more contaminated soils, a higher proportion of Hg was leached in the non-mobile fraction. A higher Hg mobility was found in the finest grain-size subsamples, probably due to the accumulation of clay minerals and oxides in these ranges.

Adsorption↗
PubMed2006

A test of sequential extractions for determining metal speciation in sewage sludge-amended soils.

Sequential extraction procedures are widely used to estimate the quantity of trace metals bound to different solid fractions in contaminated soils. However, reliability of speciation of trace metals by these procedures remains largely unexamined. In the present study, the selectivity of each extraction step was tested by observing the effect of reversing the extraction order in the procedure. Two different sequential extraction methods and their reversed modes were used for metal fractionation in sewage sludge-amended soils. Significantly increased amounts of extractable metals (Cd, Cu, Pb and Zn) were evident in the sludge-amended soils compared to control soil by all extraction schemes; however, the amounts of metals extracted by each step were strongly dependent on the order of extraction, the type of reagents and the nature of the individual metals. Caution is advised in deducing the forms of soil metals from sequential extraction results from metal-contaminated soils.

Cadmium↗
PubMed2006

Impact of river overflowing on trace element contamination of volcanic soils in south Italy: part I. Trace element speciation in relation to soil properties.

Volcanic soils affected by different numbers of polluted river flooding events were investigated. Chromium and Cu were the major soil contaminants. Nickel, Fe, Zn and Mn total content never exceeded the Italian mandatory limits. The distribution of Cr and Cu total contents among studied soils indicated that only Cr contamination was related to overflowing events. In polluted soils, sequential chemical extractions revealed a preferential association of Cr and Cu with organic forms. A progressive Cr insolubilization with ageing was observed. Significant amounts of Cr and Cu were extracted by NH(4)-oxalate, suggesting metals association with short-range-order aluminosilicates and organo-mineral complexes. Possible methodological drawbacks in the use of the EU-BCR chemical speciation protocol on volcanic soils are discussed. Micromorphology and SEM/WDS analyses revealed Cr and Cu enriched silt and clay coatings in surface and subsurface soil horizons, suggesting a transfer of metal-rich sediments along the soil pore network with water movement.

Chromium↗
PubMed2006

The leachability, bioaccessibility, and speciation of Cu in the sediment of channel catfish ponds.

There have been growing concerns about the environmental impact of Cu applied in the catfish pond aquaculture. In this paper, sediments taken from three commercial catfish ponds were studied for content, leachability, bioaccessibility, and speciation of sediment-bound Cu. Results showed that the Cu was concentrated in the top 10 cm of the sediments and the peak Cu concentrations ranged from the background level to about 200 mg/kg. Toxicity characteristic leaching procedure showed only 1-8% of sediment Cu was leachable while bioaccessible Cu, evaluated by physiological based extraction test, accounted for up to 40-85% of total Cu. Due to the high redox potential in the surface sediments, acid-volatile sulfide was not a significant binding phase. The sequential extraction results showed that the residual phase (forms in lattices of primary and secondary minerals) was the major Cu fraction in the first two pond sediments but carbonate-bound, Fe/Mn oxide-bound and organically bound Cu, as well as the residual fraction, seemed equally important in the third pond.

Animals↗
PubMed2006

Arsenic speciation transported through the placenta from mother mice to their newborn pups.

The primary goal of the present study was to confirm the arsenic species that can be transferred from the mother to the bodies of newborn pups through the placenta and the speciated arsenic distribution in the liver and brain of newborn mice after gestational maternal exposure to inorganic arsenic (iAs). Mother mice were exposed to iAsIII and iAsV in drinking water during gestation. The livers and brains of the mother mice and their newborn pups were taken. Contents of iAs, monomethylarsonic acid (MMA), dimethylarsinic acid (DMA), and trimethylarsenic (TMA) compound were detected using the HG-AAS method. Contents of iAs, MMA, and DMA in the liver of mother mice increased with the concentration of arsenite or arsenate in their drinking water. However, only DMA increased with the concentration of arsenate or arsenite in the drinking water in the brain of mother mice. On the other hand, contents of both iAs and DMA in the liver and brain of newborn mice increased with the concentration of arsenate or arsenite administered to their mother orally. Contents of arsenic species in the liver and brain of both mother mice and their newborn pups were significantly lower in the 10 ppm iAsV group than in the 10 ppm iAsIII group. Ratios of iAs or DMA levels between the brain and the liver of newborn mice were larger than 1, whereas those in mother mice were much smaller than 1. iAs taken from drinking water was distributed and metabolized mainly in the liver of mother mice. iAsIII in low levels may be taken up and metabolized easily in the liver compared to iAsV. Both iAs and DMA are transferred from the mother through the placenta and cross the immature blood-brain barrier (BBB) easily. Compared to that in the liver of newborn mice, DMA as an organic metabolite is prevalent in brain, a lipidic organ, if the BBB is not matured enough to prevent it from entering the brain.

Animals↗
PubMed2005

Contrasting views over a hybrid complex: Between speciation and evolutionary "dead-end".

The Squalius alburnoides complex, of hybrid origin, comprises diploid, triploid and tetraploid forms and has a widespread distribution in the Iberian waters. The southern populations of this complex, sympatric with S. pyrenaicus, show high genetic variability, diversity of forms and reproductive modes which create pathways that may allow for the establishment of a new species in the future. Here we report a contrasting view over the S. alburnoides complex: in the Mondego River basin (northern Portugal), nuclear "non-hybrid" and tetraploid forms are absent and a clearly impoverished genetic diversity is observed, contributing to a general scarcity of possibilities of generating novel genetic material. Moreover, the bisexual species involved in the maintenance of the complex in this basin (S. carolitertii) exhibits a considerably lower genetic variability, when compared with S. pyrenaicus. The observed differences suggest that, despite being originated by similar hybridization events and maintained by analogous reproductive mechanisms, different populations of the complex were exposed to distinct evolutionary constrains, which in some cases resulted in diversification and speciation while in others led to a compromising situation in terms of evolutionary potential. Additionally, and for the first time all forms were used in the calculation of genetic distances and diversity indices, widening the possibilities of analysis of the complex by allowing the inclusion of a large part of the available data, irrespective of ploidy level.

Animals↗
PubMed2006

Speciation of 210Po and 210Pb in air particulates determined by sequential extraction.

Speciation of (210)Po and (210)Pb in air particulates of two Syrian phosphate sites with different climate conditions has been studied. The sites are the mines and Tartous port at the Mediterranean Sea. Air filters were collected during September 2000 until February 2002 and extracted chemically using different selective fluids in an attempt to identify the different forms of these two radionuclides. The results have shown that the inorganic and insoluble (210)Po and (210)Pb (attached to silica and soluble in mineral acids) portion was found to be high in both sites and reached a maximum value of 94% and 77% in the mine site and Tartous port site, respectively. In addition, only 24% of (210)Pb in air particulates was found to be associated with organic materials probably produced from the incomplete burning of fuel vehicle and similar activities. Moreover, the (210)Po/(210)Pb activity ratio in air particulates was higher than that in all samples at both sites and varied between 3.85 in November 2000 at Tartous port site and 20 in April 2001 at the mine area. These activity ratios were also higher than the natural levels. The (210)Po/(210)Pb activity ratio was also determined in each portion resulting from the selective extraction and found to be higher than that in most samples. The sources of (210)Po excess in these portions are discussed. Soil suspension, which is common in the dry climate dominant in the area, sea water spray and heating of phosphate ores were considered; polonium is more volatile than the lead compounds at even moderate temperature. Furthermore, variations in the chemical forms of (210)Po and (210)Pb during the year were also investigated. However, the results of this study can also be utilized for dose assessment to phosphate industry workers.

Air Pollutants, Radioactive↗
PubMed2004

Phytotoxicity and heavy metals speciation of stabilised sewage sludges.

The presence of heavy metals in the sludges produced in wastewater treatment restricts plants growth and hence their use for agricultural purposes. This study looks at different types of sludges (aerobic, anaerobic, unstabilised and sludge from a waste stabilisation pond) and compares the distribution of the heavy metals that they contain according to the treatment that they have undergone. The sewage sludges were subjected to chemical characterisation and phytotoxicity testing (in absence of substrate) to provide a preliminary assessment of their suitability for land application. In addition, the total quantity of metals (Cd, Cr, Cu, Ca, K, Fe, Mg, Ni, Na, Pb and Zn) was determined. The Community Bureau of Reference (BCR) method for heavy metal speciation was followed. It was confirmed that the total concentration of heavy metals did not exceed the limits set out by European legislation and that the stabilisation treatment undergone by the sludges strongly influenced the heavy metal distribution and the phases to which they were associated. The sludge extracts did not exert any significant adverse effect on the relative seed germination (RSG) of barley (Hordeum vulgare L.) or cress (Lepidium sativum L.), although the reduction in germination index (GI) indicates that some characteristics existed did have an adverse effect on root growth.

Biological Assay↗
PubMed2004

Vanadium(III) complexes with L-cysteine--stability, speciation and the effect on actin in hepatoma Morris 5123 cells.

The complexation processes of vanadium(III) with L-cysteinate and s-methyl-L-cysteinate ligands have been studied in aqueous solutions in the pH range 2-7 by the pH-potentiometric, UV-Vis absorption and CD spectroscopy methods. The equilibria model of complex formation, evaluated by SUPERQUAD program, so as careful inspection of spectroscopic data have allowed to determine the speciation and the coordination mode of vanadium(III) ion in the major species present in aqueous solutions. Relatively stable ML2 species of vanadium(III)-L-cysteinate system exists in aqueous solutions above pH 5. It was deduced from spectral data that the coordination sphere of vanadium(III) ion in V(Cys)2 is completed by oxygen, nitrogen and sulfur atoms of two L-cysteinate ligands. Solution of vanadium(III) with L-cysteine (pH approximately 7, L/M=20) was administrated to the culture medium of hepatoma Morris 5123 growing cells. Cytotoxic effect of this solution towards tumor cells was observed. The viability of these cells depended on the complex concentration. It was reduced by 70% at 100 microM of the vanadium species concentration in the culture medium. The death of cancer cells seems to be induced on apoptotic route. The statistically significant increase of total actin level and filamentous to monomeric actin ratios (F/G) were found in the cytoplasm of cells exposed to the vanadium(III)-L-cysteine complex. It was accompanied by the rearrangement of actin cytoskeleton architecture. These factors are important for migration and metastasis formation of the cancer cells.

Actins↗
PubMed2006

Effects of N-alkyl and ammonium groups on the hydrolytic cleavage of DNA with a Cu(II)TACH (1,3,5-triaminocyclohexane) complex. Speciation, kinetic, and DNA-binding studies for reaction mechanism.

cis,cis-1,3,5-Triaminocyclohexane (c-TACH), its N-alkyl-derivatives (alkyl = methyl, ethyl), and trans,cis-1,3,5-triaminocyclohexane (t-TACH) were prepared, and speciation and DNA cleaving property of Cu(II) complexes of these ligands were investigated. All of the complexes efficiently promote the hydrolytic cleavage of supercoiled plasmid DNA under physiological conditions without further additives. The DNA cleavage rate (V(obs)) trend at pH values between 8 and 9 is N-Me(3) = N-Et(1) < t-TACH < c-TACH < N-Et(2) < N-Et(3). At pH 7, the trend is c-TACH < N-Et(3) = N-Et(2) < N-Et(1) < N-Me(3) << t-TACH. The cleavage rate constants at 35 degrees C, for the c-TACH complex are 3 x 10(-1) h(-1) at pH 8.1 and 2 x 10(-1) h(-1) at pH 7.0 ([DNA] = 7 microM, [Cu(II)-complex] = 105 microM). The hydrolytically active species at pH > 8 is CuL(H(2)O)(OH)(+) in which L coordinates to Cu(II) as a tridentate ligand for all complexes except for t-TACH. The hydrolytically active species at pH 7 is CuLH(H(2)O)(3)(3+) or CuLH(H(2)O)(4)(3+) in which LH coordinates as bidentate ligand. DNA-binding constants of c-TACH and t-TACH complexes are presented and the effects of N-alkyl and ammonium groups are discussed in light of the proposed reaction mechanism.

Alkylation↗
PubMedDate not supplied

Total content and chemical speciation of arsenic in the polychaete Sabella spallanzanii.

An unusual feature has been observed in polychaetes regarding their capacity to accumulate high levels of relatively toxic forms of arsenic in specific tissues. Basal levels of arsenic and distribution of its compounds were investigated in tissues of the Mediterranean polychaete Sabella spallanzanii. Particularly high concentrations were measured in the branchial crown (1036+/-136 microg/g d.w.) and chemical speciation revealed that the predominant form was the relatively toxic dimethylarsinate (DMA). These data suggest a potential role of As as anti-predatory strategy in polychaetes.

Animals↗
PubMedDate not supplied

Chemical speciation of arsenic in different marine organisms: Importance in monitoring studies.

Arsenic is a widely distributed element in the marine environment. Inorganic and organic compounds have extremely different toxicological effects, and their characterization is thus of great utility when monitoring and assessing the impact of arsenic pollution. In this study both the levels of total arsenic and its chemical speciation were analyzed in several marine organisms collected from Cienfuegos Bay (Cuba) following an episode of acute As-contamination. Fish from the more impacted site were characterized by elevated concentrations of arsenic (up to 500 microg/g d.w.) and inorganic species represented the predominant forms in muscle tissues of these organisms.

Animals↗
PubMed2005

Copper bioavailability in a coastal environment of Northern Chile: comparison of bioassay and analytical speciation approaches.

An integrated approach including chemical speciation analyses and microalgal bioassays was used to assess the impact of copper from copper mining on a coastal area in Northern Chile. Dissolved copper ranged from <1 microg l(-1) at reference sites to 48 microgl(-1) at sites close to the mine discharge. Dissolved copper at sites closest to the discharge always exceeded seawater complexing capacities determined by anodic stripping voltammetry (ASV), and consequently labile copper was always detected (1-37 microg l(-1)). Agreement between ASV-labile copper and copper retained by cation exchange (ALSA) columns was excellent. Measured labile copper also accurately predicted bioavailable copper determined by growth inhibition of Nitzschia closterium and enzyme inhibition in Dunaliella tertiolecta. Seawater from Caleta La Lancha had the highest dissolved and labile copper and was the most toxic to micro-algal growth and enzyme activity. Previous studies at this site confirmed it had the lowest level of biodiversity, suggesting that copper may have both direct and indirect effects on these communities.

Biological Assay↗
PubMed2005

Morphometrical evidence for speciation within Bolivian Lutzomyia aragaoi (Diptera: Psychodidae).

For Bolivian specimens of Lutzomyia aragaoi (Costa Lima, A., 1932. Sobre os phlebotomos americanos (Diptera, Psychodidae). Mem. Inst. Oswaldo Cruz 26, 15-69), collected in the same light-traps, we show the existence of two distinct morphotypes distinguished by male parameres. These sympatric forms were observed in the Alto Beni, Subandean region of Bolivia, and in the North Beni, Amazonian region of Bolivia, two areas separated by large, sparsely forested, "llanos". Univariate morphometric comparisons between these two forms showed non-overlapping variation of size for external structures of the genitalia (lateral lobe, style and coxite), allowing separation of them on the basis of a single measurement. Multivariate discriminant analysis of head and wing dimensions-excluding genitalia structures-grouped the insects according to their morphotype instead of their geographic origins. The two forms also showed different patterns in number and distribution of low mesepisternal setae. The existence of these two separate forms in close sympatry suggests reproductive isolation, hence a speciation process.

Animals↗
PubMed2006

Speciation of manganese in cells and mitochondria: a search for the proximal cause of manganese neurotoxicity.

Recent studies of speciation of manganese (Mn) in brain mitochondria, neuron-like cells, and astrocytes are reviewed. No evidence is found for oxidation of Mn(2+) complexes to a Mn(3+) complex. The only evidence for any Mn(3+) complex is found in a spectrum essentially identical to that of mitochondrial manganese superoxide dismutase (MnSOD). While this does not prove that no Mn(3+) is produced in these tissues by oxidation of Mn(2+), it does suggest that formation of an active Mn(3+) complex by oxidation of Mn(2+) probably does not play as important a role in Mn toxicity as has been suggested earlier. Since these results suggest that we should look elsewhere for the proximal causes of Mn neurotoxicity, we consider the possibilities that Mn(3+) may be transported into the cell via transferrin and that Mn(2+) may inhibit Ca(2+)-activation and control of the rate of ATP production by oxidative phosphorylation.

Animals↗
PubMed2005

Speciation in parasites: a population genetics approach.

Parasite speciation and host-parasite coevolution should be studied at both macroevolutionary and microevolutionary levels. Studies on a macroevolutionary scale provide an essential framework for understanding the origins of parasite lineages and the patterns of diversification. However, because coevolutionary interactions can be highly divergent across time and space, it is important to quantify and compare the phylogeographic variation in both the host and the parasite throughout their geographical range. Furthermore, to evaluate demographic parameters that are relevant to population genetics structure, such as effective population size and parasite transmission, parasite populations must be studied using neutral genetic markers. Previous emphasis on larger-scale studies means that the connection between microevolutionary and macroevolutionary events is poorly explored. In this article, we focus on the spatial fragmentation of parasites and the population genetics processes behind their diversification in an effort to bridge the micro- and macro-scales.

Animals↗
PubMed2004

In situ speciation studies of copper in the electroplating sludge under an electric field.

Speciation of copper in the electrokinetic treatments of an industrial sludge was studied by in situ extended X-ray absorption fine structural (EXAFS) and X-ray absorption near-edge structural (XANES) spectroscopies in the present work. The least-square fits (LSF) of the XANES spectra indicated that the main copper species in the sludge were Cu(NO)(3) (82%) and adsorbed copper (Cu/SiO(2)) (17%). Copper in the sludge possessed a Cu-O bond distance of 1.97A with a coordination number (CN) of 3.8. In the second shells, the bond distance of Cu-(O)-Si was 3.03A with a CN of 1.5. Most of Cu/SiO(2) was dissolved in the aqueous phase since little Cu-(O)-Si species in the sludge was found after 180 min of the electrokinetic treatments. About 69% of total Cu(II) was dissolved into the aqueous phase and 51% of which was migrated to the cathode under the electric field (5V cm(-1)) for 180 min.

Copper↗