Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Mobilization potential”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 325 records · Page 18Linked to original sources
PubMed2005

Solid state partitioning of trace metals in suspended particulate matter from a river system affected by smelting-waste drainage.

The partitioning of particulate trace metals was investigated during one year of monthly sampling of suspended particulate matter (SPM) at eight sites along the Lot-Garonne fluvial system, known for its polymetallic pollution. The chemical partitioning in five operationally defined fractions (exchangeable/carbonate, Fe/Mn oxides, organic matter/sulfides, acid soluble, residual) was determined using a multiple single extraction approach. This approach showed that Cd, Zn, Pb and Cu were mainly associated with acid soluble phases (84-95%, 65-88%, 61-82% and 55-80% of the respective total metal content), and therefore showed a high mean potential of mobilization and bioavailability. In the Riou-Mort River, draining the smelting-wastes, Zn, Cd and Mn showed high mobility as they were little associated with the residual fraction (1-2%) and mainly bound to the 'exchangeable' fraction of SPM (60-80%), probably weakly adsorbed on amorphous freshly-precipitated sulfide and/or oxide phases. Upstream and downstream of the anthropogenic source of metallic pollution, Mn and Cd, and Zn to a lesser extent, remained highly reactive. The other trace metals were mainly associated with the residual fraction and thus less mobile. However, the multiple single extraction scheme revealed that the most reactive transport phases were non-selectively extracted by the conventional extractants used here. These selectivity problems could not have been observed if sequential extraction was used.

Journal Article↗
PubMed2005

Displacement of five metals sorbed on kaolinite during treatment with modified Fenton's reagent.

The displacement of sorbed metals during the treatment of soils and groundwater with modified Fenton's reagent was investigated using five common metal contaminants (cadmium, copper, lead, nickel, and zinc) and kaolinite as a model sorbent. Modified Fenton's conditions included three H(2)O(2) concentrations (0.9, 1.8, 2.7 M) and two catalysts: soluble iron (III) at pH 3 and iron (III)-NTA chelate at pH 6. Iron (III)-catalyzed Fenton's reactions released significant amounts of zinc, cadmium, and copper. Modified Fenton's reactions catalyzed by iron (III)-NTA released zinc, cadmium, copper, and lead, and resulted in greater amounts of metals release than the iron (III)-catalyzed reactions. Metals release may have been mediated by transient oxygen species, such as superoxide, generated by propagation reactions, which become dominant at the relatively high hydrogen peroxide concentrations used. Metals release from kaolinite was undetectable when sufficiently low hydrogen peroxide concentrations were maintained to minimize propagation reactions. These results indicate that using dilute concentrations of hydrogen peroxide for Fenton's ISCO may minimize potential metals mobility when treating contaminated soils and groundwater containing a mixture of organic and metal contaminants.

Adsorption↗
PubMed2006

Solubility of schoepite: comparison and selection of complexation constants for U(VI).

Solubility of UO(3) x nH(2)O and sorption of U(VI) onto ferric (hydr)oxides were measured at pH 5.9, 6.8, and 7.8 at 10(-3.5)atm CO(2) using reaction times up to 48 days. Precipitation was fastest in the presence of hydrous ferric oxide and slower with hematite or without an initial solid phase. Solubility after 48 days was statistically similar for low to intermediate initial supersaturation conditions and increased for the highest initial supersaturation. Schoepite was identified for low-to-intermediate initial conditions of supersaturation and was not found for the highest initial supersaturation. Predicted concentrations of monomeric and polymeric species differed considerably with the different suites of complexation constants, resulting in significant differences in predicted oxidation-reduction potential and mobility of U(VI) in groundwater. Solubilities for low to intermediate initial supersaturation were best represented using complexation constants from Langmuir, D. [1978. Uranium solution-mineral equilibria at low temperatures with applications to sedimentary ore deposits. Geochim. Cosmochim. Acta 42, 547-569] and log*K(sp)=5.39 for schoepite, while solubilities for very high initial supersaturation were consistent with amorphous UO(3) x nH(2)O.

Chemical Precipitation↗
PubMed2006

Size charge fractionation of metals in municipal solid waste landfill leachate.

Municipal solid waste landfill leachates from 9 Norwegian sites were size charge fractionated in the field, to obtain three fractions: particulate and colloidal matter >0.45microm, free anions/non-labile complexes <0.45microm and free cations/labile complexes <0.45microm. The fractionation showed that Cd and Zn, and especially Cu and Pb, were present to a large degree (63-98%) as particulate and colloidal matter >0.45microm. Cr, Co and Ni were on the contrary present mostly as non-labile complexes (69-79%) <0.45microm. The major cations Ca, Mg, K, and Mn were present mainly as free cations/labile complexes <0.45microm, while As and Mo were present to a large degree (70-90%) as free anions/non-labile complexes <0.45microm. Aluminium was present mainly as particulate and colloidal matter >0.45microm. The particulate and colloidal matter >0.45microm was mainly inorganic; indicating that the metals present in this fraction were bound as inorganic compounds. The fractionation gives important information on the mobility and potential bioavailability of the metals investigated, in contrast to the total metal concentrations usually reported. To study possible changes in respective metal species in leachate in aerated sedimentation tanks, freshly sampled leachate was stored for 48h, and subsequently fractionated. This showed that the free heavy metals are partly immobilized during storage of leachate with oxygen available. The largest effects were found for Cd and Zn. The proportion of As and Cr present as particulate matter or colloids >0.45microm also increased.

Chemical Fractionation↗
PubMed2002

Creation of an artificial bifunctional intein by grafting a homing endonuclease into a mini-intein.

The majority of inteins are comprised of a protein splicing domain and a homing endonuclease domain. Experimental evidence has demonstrated that the splicing domain and the endonuclease domain in a bifunctional intein are largely independent of each other with respect to both structure and activity. Here, an artificial bifunctional intein has been created through the insertion of an existing homing endonuclease into a mini-intein that is naturally lacking this functionality. The gene for I-CreI, an intron-encoded homing endonuclease, was grafted into the monofunctional Mycobacterium xenopi GyrA intein at the putative site of the missing endonuclease. The resulting fusion protein was found to be capable of protein splicing similar to that of the parent intein. In addition, the protein demonstrated site-specific endonuclease activity that is characteristic of the I-CreI homing endonuclease. The function of each domain therefore remained unaffected by the presence of the other domain. This artificial fusion of the two domains is a potential novel mobile genetic element.

Algal Proteins↗
PubMed1999

Transport of rimsulfuron and its metabolites in soil columns

This paper presents a study on degradation, sorption and transport of the sulfonylurea herbicide rimsulfuron and its major metabolites in alluvial soil columns. The formulation of rimsulfuron was found to strongly affect its degradability. Hydrolysis of pure rimsulfuron takes place rapidly in distilled water (t(1/2)=2.2 days) or indeed instantaneously in alkaline solution. The formulated rimsulfuron (Titus, 25% rimsulfuron, Du Pont De Nemours) is more persistent in alluvial soil suspensions (t(1/2)=7.5 days). The study of sorption of Titus and its two major metabolites (1 and 2) revealed that these three chemicals are potentially highly mobile in the studied soil: in suspension distribution coefficients of 0.0028, 0.125 and 0.149 cm3 g(-1) were obtained respectively. Given the instability of rimsulfuron in alkaline solutions, the pH effect was evaluated with metabolite 2 in water saturated Fontainebleau sand columns at pH 6, 8 and 10. Transport was found to be strongly dependent on pH; a linear relationship was obtained between pH and the retardation factor or the dispersion coefficient. In alluvial soil columns, rimsulfuron from Titus was found to be very mobile (R=1.2) and rapidly degraded into metabolites 1 and 2, which were transported at a similar velocity. Nevertheless, the risks of groundwater contamination by rimsulfuron seem very low, as it is rapidly degraded under dynamic conditions (t(1,2)=1.4 days). On the other hand the relatively stable metabolite 2 seems likely to persist in the soil and to be transported to the groundwater. Special attention should thus be given to this compound at least as long as its harmlessness is not demonstrated.

Journal Article↗
PubMed2000

Assessing the consequences of global change for forest disturbance from herbivores and pathogens.

Herbivores and pathogens impact the species composition, ecosystem function, and socioeconomic value of forests. Herbivores and pathogens are an integral part of forests, but sometimes produce undesirable effects and a degradation of forest resources. In the United States, a few species of forest pests routinely have significant impacts on up to 20 million ha of forest with economic costs that probably exceed $1 billion/year. Climatic change could alter patterns of disturbance from herbivores and pathogens through: (1) direct effects on the development and survival of herbivores and pathogens; (2) physiological changes in tree defenses; and (3) indirect effects from changes in the abundance of natural enemies (e.g. parasitoids of insect herbivores), mutualists (e.g. insect vectors of tree pathogens), and competitors. Because of their short life cycles, mobility, reproductive potential, and physiological sensitivity to temperature, even modest climate change will have rapid impacts on the distribution and abundance of many forest insects and pathogens. We identify 32 syndromes of biotic disturbance in North American forests that should be carefully evaluated for their responses to climate change: 15 insect herbivores, browsing mammals; 12 pathogens; 1 plant parasite; and 3 undiagnosed patterns of forest decline. It is probable that climatic effects on some herbivores and pathogens will impact on biodiversity, recreation, property value, forest industry, and even water quality. Some scenarios are beneficial (e.g. decreased snow cover may increase winter mortality of some insect pests), but many are detrimental (e.g. warming tends to accelerate insect development rate and facilitate range expansions of pests and climate change tends to produce a mismatch between mature trees and their environment, which can increase vulnerability to herbivores and pathogens). Changes in forest disturbance can produce feedback to climate through affects on water and carbon flux in forest ecosystems; one alarming scenario is that climate warming may increase insect outbreaks in boreal forests, which would tend to increase forest fires and exacerbate further climate warming by releasing carbon stores from boreal ecosystems. We suggest a list of research priorities that will allow us to refine these risk assessments and adopt forest management strategies that anticipate changes in biotic disturbance regimes and mitigate the ecological, social, and economic risks.

Animal Nutritional Physiological Phenomena↗
PubMedDate not supplied

The effect of PCBs on glycogen reserves in the eastern oyster Crassostrea virginica.

Recent declines in Chesapeake Bay oyster populations have been attributed to disease, and reduced water quality from pollution. The stress associated with pollutant exposure may reduce energy available for growth and reproduction. Polychlorinated biphenyls (PCBs) are lipophilic contaminants that may potentially affect mobilization of lipid reserves, increasing reliance on glycogen stores, which could otherwise be utilized to supply energy for gametogenesis. Thus, PCBs may indirectly affect glycogen stores in oysters in a deleterious manner. To test for this effect, reproductively inactive oysters were exposed to PCBs by feeding individuals 0.7 g of algal paste containing 0, 0.35, or 3.5 micrograms PCBs daily for 8 weeks. Additionally, a group of oysters was exposed to PCBs (0, 0.35, and 3.5 micrograms) plus 0.3 g of non-toxic artificial sediment to examine interactive effects of sediment particles and PCBs. Adductor muscle, mantle, and gonadal tissues were analyzed for glycogen content. Results suggest that glycogen content is reduced in the adductor muscle with increasing PCB exposure, but there are no effects of PCBs in the mantle and gonadal tissues.

Animals↗
PubMed1999

Xenogeneic and allogeneic anti-MHC immune responses induced by plasmid DNA immunization.

Major histocompatibility complex (MHC) proteins are known to be incorporated into the human immunodeficiency virus (HIV-1) envelope as the virion buds from the host cell surface. Studies using simian immunodeficiency virus (SIV) infection of macaques have demonstrated that immunization with uninfected human cells or purified HLA proteins can provide protection from challenge with live SIV when it is grown in human cells expressing the same MHC alleles. Thus the induction of anti-MHC immune responses represents an important option to consider with respect to vaccine design for SIV and HIV. Here we examine plasmid DNA immunization strategies as an alternative to cellular or protein immunogens for the induction of xenogeneic and allogeneic immune responses in C57BL/6 mice and in an HLA transgenic mouse model system, respectively. We compared the immunogenicity of HLA-A2- and HLA-B27-expressing splenocytes with the corresponding plasmid DNA immunogens. Results from the transgenic mouse experiments indicate that plasmid DNA immunization with both class I and class II MHC-encoding vectors can elicit antibody responses recognizing conformationally intact MHC molecules. Our data also show that immunization with class I MHC-encoding DNA immunogens can elicit cytotoxic T-lymphocyte responses, demonstrating the potential to mobilize both antibody and cell-mediated anti-MHC immune responses in the context of this approach to HIV-1 vaccine design.

AIDS Vaccines↗
PubMed2003

Heavy metal levels and solid phase speciation in street dusts of Delhi, India.

Street dust samples were collected from three different localities (industrial, heavy traffic and rural) situated in the greater Delhi area of India. The samples analyzed for Cd, Zn, Pb, Ni, Cu, and Cr indicated remarkably high levels of Cr, Ni, and Cu in the industrial area, whilst Pb and Cd did not show any discernible variations between the three localities. A multivariate statistical approach (Principal Component Analysis) was used to define the possible origin of metals in dusts. The street dusts were sequentially extracted so that the solid pools of Cd, Zn, Pb, Ni, Cu, Cr could be partitioned into five operationally defined fractions viz. exchangeable, bound to carbonates, bound to Fe-Mn oxides, bound to organic matter and residual. Metal recoveries in sequential extractions were +/- 10% of the independently measured total metal concentrations. Cd was the only metal present appreciably (27.16%) in the exchangeable fraction and Cu was the only metal predominantly associated (44.26%) with organic fraction. Zn (45.64%) and Pb (28.26%) were present mainly in the Fe-Mn oxide fraction and the residual fraction was the most dominant solid phase pool of Cr (88.12%) and Ni (70.94%). Assuming that the mobility and bioavailability are related to the solubility of geochemical forms of the metals and decrease in order of extraction, the apparent mobility and potential metal bioavailability for these highly contaminated street dust samples is: Cd>Zn approximately equal Pb>Ni>Cu>Cr.

Cadmium↗
PubMed1998

Modulation of the binding of signal peptides to lipid bilayers by dipoles near the hydrocarbon-water interface.

Interactions between signal (leader) sequences and membranes are critical to protein insertion and translocation across membranes. In this paper, circular dichroism, tryptophan fluorescence, electrophoretic mobility, dipole potential, and binding measurements were used to study the interaction of the signal sequence of the Escherichia coli LamB protein with various lipid bilayers. By modifying specific chemicophysical properties of both the signal sequence and bilayer, we analyzed some of the key factors underlying peptide-lipid interactions. We synthesized three analogues of the LamB signal peptide differing in their net charge (-2 to +4) and studied their binding to bilayers containing combinations of neutral lipids [egg phosphatidylcholine (EPC), sphingomyelin, cholesterol, ketocholesterol, and nitroxide-containing phospholipid] and a charged lipid (phosphatidylserine). All three peptides bound to EPC bilayers and underwent a random coil to alpha-helix transition upon binding. Microelectrophoresis experiments revealed that both the N and C termini were near the outer surface of the bilayer, suggesting that the peptides adopted a "hammock" configuration with both termini exposed to the aqueous phase and the core of the alpha-helix located near the hydrocarbon-water interface. The binding of these LamB peptides was not markedly dependent on the bilayer area per molecule, compressibility modulus, or dipole potential, but did depend on the charge of the peptide and bilayer interfacial region. Moreover, the binding of LamB peptides was essentially eliminated in bilayers composed of phospholipids with a nitroxide moiety at the 7 position in one of their acyl chains or in EPC bilayers containing equimolar ketocholestanol. We propose that the incorporation of nitroxide or ketone groups into the hydrocarbon region near the lipid headgroup increases the effective width of the hydrophilic interfacial region and prevents some of the hydrophobic amino acids in the alpha-helix from reaching the nonpolar hydrocarbon core, thereby diminishing the free energy of partitioning and inhibiting peptide binding. These results point to an important role for interfacial dipoles in peptide-lipid interactions.

Amino Acid Sequence↗
PubMedDate not supplied

Magnetophoretic cell sorting is a function of antibody binding capacity.

Antibody binding capacity (ABC) is a term representing a cell's ability to bind antibodies, correlating with the number of specific cellular antigens expressed on that cell. ABC allows magnetically conjugated antibodies to bind to the targeted cells, imparting a magnetophoretic mobility on each targeted cell. This enables sorting based on differences in the cell magnetophoretic mobility and, potentially, a magnetic separation based on the differences in the cell ABC values. A cell's ABC value is a particularly important factor in continuous magnetic cell separation. This work investigates the relationship between ABC and magnetic cell separation efficiency by injection of a suspension of immunomagnetically labeled quantum simply cellular calibration microbeads of known ABC values into fluid flowing through a quadrupole magnetic sorter. The elution profiles of the outlet streams were evaluated using UV detectors. Optimal separation flow rate was shown to correlate with the ABC of these microbeads. Comparing experimental and theoretical results, the theory correctly predicted maximum separation flow rates but overestimated the separation fractional recoveries.

Antibody Affinity↗
PubMed2001

Fixation of radionuclides in soil and minerals by heating.

Heating of fine sand-sized common mineral powders (quartz, feldspar, or calcite) or a soil (from the Department of Energy's Hanford site) up to 1000 degrees C, in contact with sorbed radioisotopes (85Sr, 57Co, 134Cs, or U), markedly increased each isotope's immobilization. A sequential extraction procedure was applied after heating the materials to assess the changes in each isotope's functional form among water-soluble, cation-exchangeable, acid-soluble, and residual phases. The overall immobilization effects were consistent with rapid high temperature ionic diffusion from the initially contaminated surfaces into the mineral matrices; subsequent diffusion out of mineral particles at ambient temperature, as measured by the sequential extraction behavior, would be such a slow process that the radionuclides may be considered sequestered from further potential environmental mobilization. In the Hanford soil, the effect was found to follow an Arrhenius-type relationship with treatment temperature up to 1000 degrees C for 57Co, 85Sr, and U, and immobilization was independent of previous thermal treatment of the materials. Although 134Cs exhibited its largest immobilization in the Hanford soil after heating to 1000 degrees C, the large immobilization of 134Cs at all temperature and even in unheated Hanford soil made it difficult to observe a strong temperature dependence. A general and promising technique for environmental remediation of contaminated soil by high-temperature heating without melting can be extrapolated directly from the empirical leaching information.

Environmental Pollution↗
PubMed2006

Lone-pair orbital interactions in polythiaadamantanes.

The electronic structures of a series of polythiaadamantanes from thiaadamantane through 2,4,6,8,9,10-hexathiaadamantane (HTA) have been analyzed using density functional theory calculations in conjunction with Hückel and natural bond orbital analysis. The effects of multiple sulfur p-type lone-pair orbital interactions on ionization potentials, hole mobilities, and electronic coupling have been determined. An overall increase in the average energy of the lone-pair orbitals as the number of sulfur atoms increases is predicted, with the exact positioning of the HOMO depending on specific lone-pair interactions. Separation of through-bond (TB) and through-space (TS) interactions between intramolecular sulfur atoms has been performed using localized molecular orbitals and model systems based on interacting hydrogen sulfide molecules. TB interations were found to reduce orbital splitting, while TS interactions were found to increase orbital splitting. TS interactions were more or less constant from one polythiaadamantane to the next, and the contributions of TB effects to individual orbital energies vary depending on the relative orientation of sulfur atoms as determined by the sigma molecular framework. Electronic coupling between intermolecular sulfur lone-pair orbitals was determined by investigating unique dimer pairs observed in the crystal structure of HTA. Electronic coupling is not as strong as expected given the short intermolecular S-S distances observed in the crystal structure. In general, B3LYP/6-31G(d) and B3LYP/6-311+G(d,p) give very similar orbital energies and splittings.

Journal Article↗
PubMed2004

Effective transfection of rabies DNA vaccine in cell culture using an artificial lipoprotein carrier system.

PURPOSE: To evaluate the transfection efficiency in cell culture of rabies plasmid DNA vaccine carried by a novel artificial lipoprotein system. METHODS: Phospholipid nanoemulsions resembling the lipid core of natural lipoproteins were prepared. The artificial lipoprotein carrier system for DNA was constructed by assembling of the nanoemulsion (NE)-palmitoyl-poly-L-lysine (p-PLL)-rabies DNA complex. Agarose gel electrophoresis, zeta potential, and mobility measurement were conducted to determine the surface charge balance in various complex compositions. Transfection and transfection efficiency were examined by fluorescence microscopy and flow cytometry, respectively. RESULTS: The artificial lipoprotein system was successfully constructed and the rabies DNA vaccine was effectively transfected in glioma cell line SF-767. The amount of p-PLL incorporated into the artificial lipoprotein formulations had a significant effect on transfection efficiency. The new system also proved to be more efficient in cellular transfection of rabies DNA vaccine than the commercial lipofectamine formulation. CONCLUSIONS: Effective transfection of rabies DNA vaccine in cell culture can be achieved using the novel artificial lipoprotein carrier system, and the charge balance of the NE-p-PLL-DNA complex appears an important factor.

Cell Line, Tumor↗
PubMed2001

DCEP (dexamethasone, cyclophosphamide, etoposide, and cisplatin) is an effective regimen for peripheral blood stem cell collection in multiple myeloma.

DCEP (dexamethasone, cyclophosphamide, etoposide, and cisplatin) has proved to be an effective salvage therapy for refractory-relapsed MM patients. Little is known, however, about its potential as mobilizing therapy. The aim of this study was to evaluate the efficacy of DCEP in mobilizing PBSC and to define its toxicity. Fifty-five MM patients received DCEP followed by G-CSF as part of high-dose programs including autologous transplantation. At the time of mobilization, 40 patients had previously received VAD only, and 15 alkylating agents. Mobilization was successful (minimum number of CD34(+) cells 2 x 10(6)/kg) in 48/55 patients (87%), and 41/55 patients (75%) collected >4 x 10(6)/kg CD34(+) cells. Of the seven patients who did not mobilize stem cells, five (71%) had been previously exposed to alkylating agents. The median number of CD34(+) cells harvested was 5.8 x 10(6)/kg (range 2.1-22.4). There was no treatment-related mortality. The side-effects of DCEP were always tolerable. No neutropenia <1000/microl nor thrombocytopenia <50,000/microl were observed. No patient required transfusion as a consequence of therapy, or hospitalization for septic complications. In conclusion, DCEP, in addition to its demonstrated anti-tumor activity, is an effective regimen for mobilizing peripheral blood progenitor cells in myeloma patients, with little or no side-effects. These properties render DCEP a useful regimen for the debulking and mobilization phase of high-dose programs for multiple myeloma.

Adult↗
PubMed2003

A study of the elemental leachability and retention capability of compost.

In this work a comparison is made between the different approaches that can be taken to evaluate the mobility of elements in compost. The practical consequences of the results obtained are also discussed in terms of methods for cleaning up compost and using compost in environmental remediation. The mobility of potentially toxic elements in compost is evaluated by leaching with four selected eluents, i.e. diluted sulfuric acid, oxalate, citrate and EDTA. In contrast to the chelating agents, diluted sulfuric acid was found to generally have a low leaching capability for removal of heavy metals from compost. This implies that the risk of heavy metal leaching caused by natural rainfall is likely to be low. The results obtained in the leaching experiment were compared with previous results obtained from sequential fractionation. This comparison confirmed that both methods gave similar results for predicting the lability of elements in compost. A non-linear regression analysis of the leaching curves was also conducted. The leaching curves for elements with high lability could be fitted with a two components model. The labile components identified by the kinetic model are approximately in accordance with the fractions obtained from the first step of the sequential extraction method. The kinetic speciation method is shown to be a relatively rapid and simple procedure for compost which gives more information about element lability than simple leaching experiments. The leaching reagents used in this work were not effective enough to be used for cleaning up compost with a high metal content. Compost was however shown to have a high affinity for heavy metals, with the order of affinity of metal for the compost being very similar to that seen for humic acid. Compost may therefore prove to be a good remediation material for metal contaminated waste.

Chelating Agents↗
PubMed2005

Fractionation and elemental association of Zn, Cd and Pb in soils contaminated by Zn minings using a continuous-flow sequential extraction.

Fractionation and elemental association of Zn, Cd, and Pb in soils near Zn mining areas were studied using a continuous-flow sequential extraction approach. The recently developed sequential extraction procedure not only gave fractional distribution data for evaluation of the mobility or potential environmental impact of the metals, but also the extraction profiles (extractograms) which were used for study of elemental association. In addition, the elemental atomic ratio plot extractogram can be used to demonstrate the degree of anthropogenic contamination. Seventy-nine soil samples were collected in the vicinity of a Zn mine and were fractionated into 4 phases i.e. exchangeable (F1), acid soluble (F2), reducible (F3) and oxidizable (F4) phases. Most samples were contaminated with Zn, Cd and Pb. The reducible phase is the most abundant fraction for Zn and Pb (>50%) while Cd is concentrated in the first 3 extraction steps. The distribution patterns of Cd were obviously affected by soil pH. 55% of Cd appears predominantly in the F1 fraction for acidic soils while in neutral and alkaline soils, it was mostly (70%) found in the F2 + F3 fractions. The extractograms obtained from the continuous-flow extraction system revealed close association between Zn, Cd, Pb and Fe in the acid soluble phase, Cd-Pb and Zn-Fe in the reducible phase for contaminated soils. A correlation study of the 3 metals using a correlation coefficient was also performed to compare the results with the elemental association revealed by the extractograms. Atomic ratio plot extractograms of Zn/Fe, Cd/Fe and Pb/Fe in the reducible phase, where contaminated metals are predominant, can be used to evaluate the degree of anthropogenic contamination. From the elemental atomic ratio plot, it is obvious that the contaminants Cd and Pb are mostly adsorbed on the surface of Fe oxides. Zn, which is present in an approximately 1 ratio 1 ratio with Fe in contaminated soils, does not show a similar trend to that found for Cd and Pb.

Chemical Fractionation↗