Fractionation Of Cadmium Research Articles

Total content and extractable fraction of cadmium, cobalt, copper, nickel, lead, and zinc in calcareous orchard soils

Abstract The levels and availability of six heavy metals cadmium (Cd), cobalt (Co), copper (Cu), nickel (Ni), lead (Pb), and zinc (Zn) in calcareous orchard soils were measured in an investigation of a method for the determination of total content and extractable fraction of these metals by atomic absorption spectrometry. The digestion step was performed comparatively using two different types of heating. Cadmium, Cu, Ni, Pb, and Zn were determined by flame atomic absorption spectrometry (F‐AAS) and Cd was determined by electrothermal or graphite furnace atomic absorption spectrometry (GF‐AAS) using the method of standard addition. The detection limits, precision values, and accuracy (recovery assays) show the reliability of the method. The conditions for the determination of the extractable fraction of the metals were also optimized. Extraction time for Cd and Zn was studied, and the application of two hours of shaking was selected. The tested method was applied to real samples corresponding to highly calcareous orchard soils characteristic of the Mediterranean area. Only Zn, Cu and Pb showed high levels in their extractable forms, whereas Cd and Co had highest levels in their total contents. An important bio‐availability was observed in all the studied metals, but mainly for Cd and Pb.

Speciation Profile of Cadmium and its Bioconcentration in an Aquatic System

A study on speciation profile of cadmium and its bioconcentration in an aquatic ecosystem was undertaken. Inorganic-metallic species of cadmium along with ionic, soluble and total cadmium content were measured in the aquatic phase. Inorganic-metallic cadmium species were quantified by working out the conditional stability constants of cadmium with various inorganic ligands. Speciation profile of cadmium shows that the major fraction of cadmium is represented by soluble (including ionic) forms, and within this fraction the inorganic-metallic species are present in pico-molar concentrations. Bioconcentration studies show Cd deposits in fish tissues and in the planktonic fauna and flora. Cadmium (II) concentrations in the teleost, Colisa fasciatus and its correlation with Cd++ in the exposure medium; exemplifies that the ionic species of cadmium represent the principal bioavailable forms. Strong correlations between concentrations of Cd in the exposure medium with that of whole body Colisa fasciatus teleost ...

Chemical fractionation of phosphorus and cadmium in the marine diatom Phaeodactylum tricornutum

Fractionation of P and Cd within the cell of Phaeodactylum tricornutum grown by semi-continuous cultures in natural low concentrations of dissolved phosphate and cadmium was examined by the chemical separation method. Cellular Cd content increased with the concentration of Cd in the medium and was independent of growth rate, but it was present only in the acid-soluble fraction and no growth inhibition was observed even at 90 nM. Cellular P content in the acid-soluble fraction varied with both growth rate and concentration in the medium. The residue fraction (acid-insoluble) depended on concentration in the medium. Proportion of these fractions, however, changed only as a function of growth rate. As a consequence of these changes, cellular Cd P ratio decreased with growth rate. The distributions of Cd and P in the phytoplankton cells were not always the same portion. The Cd P ratio in phytoplankton cells is affected by the physiological state of the cells and ambient Cd PO 4 ratio in the medium. Thus, biological activity would influence the biogeochemical cycling of Cd and PO 4 and the Cd PO 4 ratio in the ocean.

Microprobe Raman study of the variation of LO phonon frequency with the Cd concentration in the ternary compound Zn1 − xCdxSe

Experimental and theoretical studies of II–VI and III–V ternary alloys suggest that the long wavelength optical phonons exhibit one of two types of behaviour, single or double mode. A semi-empirical model which has had success in predicting LO and TO phonon frequencies for mixed alloys is the random element isodisplacement model (REIM). Using a modified version of this model we have predicted that ZnCdSe will be of single mode type, and have calculated LO phonon frequency shifts with composition. Room temperature microprobe Raman measurements on samples of MBE grown Zn1 − xCdxSe with x ranging from 0 to 0.35 show a linear variation of a single LO phonon peak with composition, confirming our predictions, with good agreement with theory for low mole fraction of cadmium.

Evaluation of Elemental Cadmium as a Marker for Environmental Tobacco Smoke

Download Hi-Res ImageDownload to MS-PowerPointCite This:Environ. Sci. Technol. 1995, 29, 9, 2311-2316

Distribution of different fractions of cadmium, zinc, lead, and copper in unpolluted and polluted soils

McLaren and Crawford's method for fractionating soil Cu was modified, and used to fractionate soil Cd, Zn, Pb, and Cu in 38 soil samples from 11 soil profiles from industrially polluted and nearby unpolluted areas. Pollutant metals, especially Cd and Zn, were more soluble than the native soil metals. On average, approximately 45% of Cd was present in the CaCl2 soluble (CA) fraction, whereas corresponding values for the other metals were below 10%. The percentages of each metal in the CA fraction followed the order Cd > Zn > Pb > Cu. The same order was observed for the acetic acid soluble (AAC) fraction. Approximately 30% of total Pb and Cu were present in the pyrophosphate soluble (PYR) fraction, and only 10% of total Cd and Zn. Approximately 20% of total Zn or Pb and 10% of Cd or Cu were present in the free oxide (OX) fraction. Only 20% of Cd and between 40–50% of the other 3 metals were present in the residual (RES) fraction. The results show that Cd is more labile than the other 3 metals.

Fractionation of residual cadmium, copper, nickel, lead, and zinc in previously sludge‐amended soil

Abstract The fractionation of heavy metals in previously sludge‐amended soil is important to evaluate their behavior in the environment in terms of mobility and availability to crop plants. A surface soil that received two types of sludges at two different rates, plus fertilizer only and no treatment (control), having been fallow for nine years, was used in this study. The contents of cadmium (Cd), copper (Cu), nickel (Ni), lead (Pb), and zinc (Zn) fractions in previously sludge‐amended soils were governed by the total content of these metals in the sludges applied and by the rate of sludge application. The contents of these metals were higher for soils that received the Chicago sludge as compared to that receiving the Huntsville sludge. Furthermore, soils that received 20 Mg/ha/yr of sludge for five years generally had higher levels of these metals than those receiving a single dose at the 100 Mg/ha application rate. The percentage of the total content in the water soluble and exchangeable forms was very...

Distribution of Copper and Cadmium Fractions in Two Forest Soils.

Pollution of soil by Cu and Cd seems to be increasing in Switzerland. To know the background concentration in low polluted soil we have measured their concentrations in every horizon and calculated the total amounts. The concentrations were low: the largest concentrations of Cu and Cd occurred in the topsoil of a Typic Dystrochrept (acid brown soil) (13.5 mg kg-1 Cu and 437 μg kg-1 Cd) and in the Oi-Oa-Al and Bh horizons of a Typic Haplorthod (podzol) (up to 16 mg kg-1 Cu and 460 μg kg-1 Cd in Oi), though when corrected by density, concentrations were higher in Al horizon of the Haplorthod and Al and BC of the Dystrochrept. The Dystrochrept was found to contain more of the metals than the Haplorthod. The soil is the main storage compartment of both ecosystems. A six step sequential extraction was applied to evaluate the affinity of metals for the soil constituents and the binding strength to the solid matrix. Water, 0.1 M NaNO3 , 0.1 M hydroxylamine, 1 M hydroxylamine plus acetic acid, H2 O2 and aqua regia were used as successive reagents. Patterns of Cu and Cd distribution in a given soil are different and, to a lesser extent, for a given element the distribution patterns depend on the soil type. Organic matter or Fe and Mn oxides seem to immobilize Cu whereas Cd is associated mainly with Fe and Mn oxides. If the sequential extraction is considered as succession of reagents of increasing strength, then Cd seems to be less strongly bound to soil than Cu and thus more readily solubilized and translocated within soil. The results show the limitations of multistep sequential extraction as a technique for studying metal fractions.

Sequential Fractionation of Copper, Lead, Cadmium and Zinc in Soils from or near Doñana National Park

AbstractA knowledge of the total amount of trace metals is not enough to assess the environmental impact of polluted soils. For this reason, the determination of metal species in solution is important to evaluate their behavior in the environment and their mobilization capacity. Soils contaminated by Cu, Pb, Cd, and Zn found at Doñana National Park (Spain) were examined for total content. Sequential extraction schemes were used to determine the degree of pollution and to partition the trace elements in soils. The three areas studied (marshes, stabilized sand, and mine) have different contamination levels. The northern‐most marshes of Doñana National Park have the highest total levels of the four metals due to the influence of a mine located 40 km away. The stabilized sand was not polluted by the metals studied. The bioavailable fraction of Cd represents more than 50% of the total Cd found in soils, and this percentage is much greater than that of the other elements examined. Most of the Cu was present in the organic fraction, with only small amounts being associated with the crystalline Fe‐oxide fraction. Lead and Zn were associated mainly with the crystalline Fe‐oxide fraction, but the amount of Zn associated with the carbonates and amorphous Fe‐oxide fractions was also significant. The total amount of Cu, Pb, Cd, and Zn in the soils and their distribution in the five fractions depended on total metal contents, soil type, and soil properties (i.e., pH and percentage of sand, clay, organic matter, and carbonates). Mobility of soil metals were Cd > Zn > Pb > Cu.

The significance of (radio-) labile cadmium pools in soil

The radio-labile fraction of cadmium, in a wide range of contaminated soils, was studied in relation to fractions of cadmium defined by traditional extraction procedures. The proportion of labile Cd which was exchangeable was highly pH-dependent, but above pH 5 only about 5% of labile Cd was extractable with 1 m KNO 3. By contrast, EDTA released more than the labile Cd pool into solution, suggesting that significant dissolution of metal adsorbents may occur when chelating agents are utilised as trace metal extractants. The effect of time in immobilising Cd added to soil was also illustrated by following changes in the radio-labile Cd concentration. In calcareous soils, an instantaneous ‘fixation’ reaction as well as a time-dependent transfer to non-labile pools was identified. It is suggested that radio-labile Cd represents a relatively unambiguous assessment of the chemical and biological reactivity of Cd in soil compared with the fractions isolated by chemical extractants.

Evaluation of cadmium levels in fertilized soils

Cadmium is a normal component of phosphate fertilizers; its concentrations in them may vary as a function of the origin of the mineral since the levels of the element range from 0.I to 0.4 mg Cd.Kg -I if the mineral is from the Kola peninsula and between 70 and 90 mg Cd.Kg -I if it is from Senegal (Adriano,1986). In the case of Senegal phosphates, according to Godin (1983), it is possible to obtain phosphate fertilizers containing upto 150 mg-Cd by Kg of P205. Contamination may be caused, therefore, by the long term continuous application of phosphate fertilizers, which has resulted in the accumulation of cadmium. The nature and intensity of the interaction between cadmium and soil components are the most important factors responsible for the existence of a cadmium fraction, originating in the fertilizers, that is able to move through the soil. The aim of the present work was to evaluate the state of this element in several soils and to relate the values found with the soil variables.

Low temperature, low pressure CdZnS films produced by metalorganic chemical vapor deposition

CdxZn(1−x)S thin films were deposited on (100) Si at low temperature and low pressure from the reaction of dimethylzinc, dimethylcadmium, and hydrogen sulfide. A possible application of mixed metal-sulfide films as novel insulators in metal–insulator–semiconductor structures in HgCdTe-based infrared devices provides the motivation for studying the physical properties of the CdZnS films. The films were produced over a 25 to 125 °C range of deposition temperature, and deposition pressure less than 1 Torr. No carrier or diluent gases were used. The polycrystalline films have been characterized by x-ray photoelectron spectroscopy (XPS), scanning electron microscopy, Rutherford backscattering spectroscopy (RBS), and x-ray diffraction. Films with cadmium fractions of zero to 0.75 have been produced and characterized. The growth rate ranges from 4 to 145 Å/s. XPS indicates 1%–2 at. % oxygen contamination in the films, and about 3 at. % carbon within the bulk of the films. The cadmium mole fraction was determined by RBS and XPS. Film stress was determined by measurement of wafer bow, using x-ray diffraction.

Partitioning of trace metals released from polluted marine aerosols in coastal seawater

Mobilization and transfer of atmospherically transported metals to major suspended particulate matter components in seawater have been studied in a multichamber leaching experiment. Data on the meteorological air mass history, enrichment factors and sequential extraction analysis indicate that the highly polluted marine aerosol samples collected on Helgoland are of anthropogenic origin. A significant fraction of the total cadmium (81%), zinc (58%), copper (41%), and lead (40%) was released in seawater within 1 h. When exposed to the aerosol and artificial suspended particulate matter components for another 100 h, a portion of the released metals ranging from 10 to 60% was readsorbed. Zinc and lead were scavenged by iron/manganese oxides or readsorbed by the aerosol particulates. Of the total scavenged copper portion 67% was bound to phytoplankton cell walls which evidences an ecological impact of the polluted marine aerosols even in the coastal environment.

Influence of age and time of administration of dithiocarbamate analogues on cadmium retention in rats

In the present study the influence of age and time of chelation therapy on cadmium retention in 6-, 11-and 14-day-old rats and in 6-week-old rats has been investigated. Chelating agents N-benzyl-dithiocarboxy-D-glucamine (BDCG), sodium N-(metho-xybenzyl)-D-glucamine dithiocarbamate monohydrate (MeOBDCG) and N-methyl-N-dithiocarboxy-D-glucamine (MDCG) were administered intraperitoneally to three different groups at a dose of 1 mmol kg-1 body weight on two occasions following 115mCd intraperitoneal administration; immediately and after 24 h; after 24 h and 48 h; or after 48 h and 72 h. The 115mCd retention in the whole body and organs was determined 6 days after cadmium administration. Chelation therapy very effectively reduced cadmium retention in the whole body and organs, MeOBDCG being the most effective. The effects of chelating agents were significantly more pronounced in older than younger animals and in the case of early rather than late administration. The highest fraction of cadmium administered was retained in the liver, where also the strongest effect of chelation therapy was observed. Mobilized cadmium was excreted almost exclusively by the faecal route.

Absorption of cadmium after a long-term oral administration of cadmium to dogs

A long-term experiment using beagle dogs to investigate the absorption of cadmium was conducted. The dogs in the experimental groups were given a commercial diet and pelleted food containing 1, 3, 10, 50, and 100 mg of cadmium per day. The cadmium concentration in the blood increased continuously, gradually reaching a steady state following the administration of cadmium. The cadmium excreted daily in urine increased continuously. The cumulative excreted amount of cadmium in urine was calculated by using the trapezoidal rule based on the data of excretion of cadmium in urine. Then the absorbed fraction of administered cadmium was estimated on the basis of the relationship between the cumulative excreted amount of cadmium in urine and the cumulative administered dose of cadmium after the cadmium concentration in blood reached a steady state. The absorbed fraction of cadmium decreased with an increase in the administered dose of cadmium. A dose-dependent increase between the absorbed amount and the administered dose was observed.

Non-metallothionein-bound cadmium in the pathogenesis of cadmium nephrotoxicity in the rat

Male rats were injected SC with 0.6 mg Cd/kg/day for 5 days per week for 2, 4, 6, and 8 weeks. Liver and kidney were examined morphologically and analyzed for metallothionein, cadmium, zinc, and copper. Morphologic changes were found in kidney but not in liver. The earliest ultrastructural change consisted of myelin figures in vacuoles in cytoplasm of proximal tubular lining cells reflecting degeneration of membranes. This change occurred after 4 weeks with 801 ± 25 nmol/g (89.9 μg/g) total kidney cadmium or 390 nmol/g (43.7 μg/g) of cadmium not bound to metallothionein. Similar changes were observed after 6 weeks but after 8 weeks pathological changes consisted of focal cellular necrosis and interstitial fibrosis. Other ultrastructural changes included altered mitochondria and increased numbers of microbodies. Renal cadmium after 8 weeks exposure was 1827 ± 48 nmol/g (215.3 ± 5.8 μg/g) or 628 nmol/g (70.2 μg/g) of cadmium not bound to metallothionein. Total cadmium was higher in liver than in kidney but partitioning between bound and nonbound cadmium differed in the two organs. The fraction not bound to metallothionein increased with time of exposure in both liver and kidney. However, total cadmium in the liver did not exceed potentially available binding sites of metallothionein, whereas total cadmium did exceed potentially available binding sites of metallothionein,in the kidney where pathologic changes occurred. The results indicated that degeneration of cellular membranes is an early cellular effect of cadmium exposure followed later by toxicity to organelles, cellular necrosis, and interstitial fibrosis. Cadmium-induced cellular toxicity is more directly related to the fraction of cadmium in the kidney that is not bound to metallothionein than is total cadmium per se.

The organometallic epitaxy of extrinsic p-doped HgCdTe

Extrinsic p-doped mercury cadmium telluride (MCT) layers have been grown by organometallic vapor phase epitaxy, using arsine in hydrogen as the dopant gas. Controllable doping in the range 3.5×1015–4.3×1016 was obtained when grown on GaAs with CdTe buffer layers. Consistently higher doping concentration (a factor of 2 to 4) was observed when a CdTe substrate was used. This is believed to be due to higher dislocation densities present when grown on GaAs, around which As may segregate. The cadmium fraction fell at very high flow; we believe that this is due to the prereaction of dimethylcadmium with arsine. Isothermal annealing under a Hg-rich ambient of MCT grown on CdTe substrates did not produce significant changes in the measured doping concentration. This indicates that the acceptor level is extrinsic in nature and that arsenic behaves as a stable acceptor dopant in MCT. The activation energy of this acceptor was determined as a function of doping, and is about one-half the value of the acceptor due to the Hg vacancies.

Cadmium disposition following repeated exposure in the pregnant hamster

Pregnant Syrian hamster were given a dose of 3.9 micromoles cadmium ion/kg (radiolabelled with 109cadium) on days 7, 8, 9, and 11 of gestation. Animals were sacrificed on day 13 of gestation and maternal blood, liver, kidney, placentas, and fetuses collected. No pathology was observed in placentas or fetuses. Maternal liver accounted for 61% of the total cadmium injected (15.6 micromoles/kg dam), maternal kidney 4%, and placentas 0.24%. Maternal blood and fetuses contributed negligibly to the total body burden of cadmium. Gel filtration experiments indicated two major cadmium fractions in maternal liver, maternal kidney, and placental cytosols, one at the excluded volume and another nearly twice the excluded volume. Further purification and characterization of the cadmium fraction eluting at twice the excluded volume in the gel filtration experiments showed it to be cadmium metallothionein. Ion exchange chromatography on DEAE Sephacel revealed two forms of cadmium metallothionein in the cytosols of maternal liver and placentas. Maternal kidney cytosols contained one cadmium metallothionein. Amino acid analyses suggest that the thionein components of placental cytosols are synthesized in situ.

Cadmium mass fractionation in unequilibrated ordinary chondrites

Measurements of the isotopic composition of cadmium in whole rock samples of a number of unequilibrated ordinary chondrites have shown the presence of significant fractionation in the abundances of the isotopes. Some meteorites are enhanced in the light isotopes with respect to a laboratory standard, whilst the reverse effect is exhibited in other meteorites. The mass fractionation is linear over the range 106–116 within the limits set by experimental error. The extent of the mass-dependent fractionation varies from −2.1‰ per mass unit for light isotope enrichment for the LL3 chondrite Semarkona, to +2.7‰ per mass unit for the LL3 chondrite Bishunpur. This is the first time that negative mass fractionation has been reported for cadmium in meteoritical material. The cause of the fractionation is not known. If Rayleigh distillation were responsible then some correlation with Cd concentration would be expected, but this is not observed. There does not appear to be a correlation between the magnitude of cadmium fractionation and abundance in whole rock samples of unequilibrated ordinary chondrites.

Effectiveness of cigarette filter tips for reducing cadmium in relation to other mainstream smoke constituents.

The effectiveness of filter tips for reducing cadmium, tar, nicotine, carbon monoxide and carbon dioxide in cigarettes was studied. The cigarettes were made from tobacco grown on municipal sewage sludge-amended soil and were therefore high in cadmium. When machine-smoked, filter tips did not result in a significant reduction of cadmium deposited on Cambridge filters. This may indicate that a considerable fraction of cadmium is present in the vapor phase of the smoke and therefore not reduced to the same extent as the tar by certain filters. Nicotine and carbon monoxide were reduced to a lesser extent than tar. This indicates that the filter tip has influenced the combustion of the tobacco column during smoking.