Metal speciation

Cadmium, chromium, copper, lead, manganese, nickel, vanadium and zinc have been determined in samples of made-up ground from layers of a trial pit excavated on a recently derelict, industrially contaminated site. The pseudototal metal content of the layers was determined following a microwave-assisted digestion with aqua regia. Operational speciation was performed using the BCR three-step sequential extraction procedure. Analyses were carried out by ¯ame or electrothermal atomic absorption spectrometry (FAAS or ETAAS). A suppressive interference ($30%) was observed in the determination of cadmium in aqua regia digests by ETAAS, but not in 0.11 mol l À1 acetic acid, 0.1 mol l À1 hydroxylammonium chloride or 1.0 mol l À1 ammonium acetate extracts. Agreement between duplicate samples was acceptable (i.e. within 10%) for most elements in most layers, but some large discrepancies were apparent, especially for lead. The amount of metal extracted in the sequential procedure (i.e. Step 1Step 2Step 3residual) did not generally agree well with pseudototal digestion. Various layers of the trail pit contained signi®cant levels of contaminant metals, but these were not always in easily mobilized forms. For example, less than 0.2% of the lead ($4000 mg g À1 ) at 65±85 cm depth was present as exchangeable or acid-soluble species. The study illustrates the importance of considering metal speciation when assessing the mobility of potentially toxic elements in industrially-contaminated land. # 1998 Elsevier Science B.V.

In Morocco, spices are an integral part of daily cuisine and serve as a vector of both nutritional and toxicological exposure. Monitoring elemental composition is essential to ensure consumer safety, animal health when used as feed additives, and compliance with international standards. The present study aimed to determine the concentrations of essential (potassium, calcium, magnesium, sodium, and iron) and toxic (lead, cadmium, arsenic, chromium, and nickel) elements in commonly consumed spices in Morocco, including cinnamon, cumin, ginger, black pepper, and turmeric. A total of 162 spice samples were obtained from markets in the Greater Casablanca, Morocco. Five essential elements, including potassium, calcium, magnesium, sodium, and iron, and five toxic trace metals, including lead, cadmium, arsenic, chromium, and nickel, were determined by inductively coupled plasma mass spectrometry (ICP-MS) after microwave-assisted digestion. Cumin indicated the highest levels of magnesium (6.86 ± 1.61 g/kg), sodium (3.98 ± 1.59 g/kg), calcium (11.13 ± 4.53 g/kg), and iron (753.71 ± 446.07 mg/kg). Turmeric had the highest levels of potassium (25.96 ± 13.51 g/kg). Cinnamon had elevated levels of lead (2.05 mg/kg) and cadmium (0.29 mg/kg), exceeding Moroccan and European regulatory limits. Additionally, cumin indicated the highest levels of arsenic (0.45 ± 0.30 mg/kg) and nickel (4.18 ± 2.85 mg/kg) compared to other spices. Principal component analysis (PCA) revealed distinct elemental patterns. The first component (PC1), driven by magnesium and sodium, clearly separated cumin due to its high macronutrient content. The second component (PC2), influenced by cadmium and lead, isolated cinnamon because of its toxic metal burden. The PC1 and PC2 accounted for 64.6% of the total variance. Turmeric and ginger formed a close cluster in the PCA plot, associated with higher levels of potassium, calcium, and nickel. Black pepper was positioned between these groups, reflecting intermediate composition. Pearson correlation analysis supported these findings, with a strong correlation between lead and cadmium, suggesting a shared contamination source. These results emphasized the nutritional and toxicological roles of spices in Moroccan diets. Regular monitoring is essential to protect public health in both animals and humans.

An industrial site, polluted with As and heavy metals, was investigated by combining chemical (sequential extractions and pHstat leaching tests), physical and mineralogical characterization of soil samples and slag fragments, and by the analysis of soil porewater aimed at assessing the distribution, speciation and mobility of heavy metals and As. On the site itself, arsenic concentrations up to 3.6% in surficial soil samples and up to 22% in slag fragments were found, together with elevated concentrations (percentage level) of Cu, Co, Ni, Zn and Pb. High concentrations of arsenic (up to 38,000 microg/l) and heavy metals (up to 1700 microg/l Cu and 4700 microg/l Zn) were also found in the in situ sampled soil porewater, highlighting the considerable availability of As, Zn and Cu for uptake by plants and leaching to the ground water. Sequential extractions also indicated a high availability of arsenic and copper in most samples and slag fragments of the industrial site, although poorl...

Although mining has contributed considerably towards the GDP of a country it is the disposal of waste associated with mineral benefication has resulted in mine tailings that have an impact on the environment. studies were carried out to assess the heavy metal uptake by Paspalum grass species at a mine tailings dam (New Union Gold Mine, Limpopo south Africa) and a control site. the Paspalum di-latatum on average, absorbed total metal concentrations of 290.7 mg/kg (mine tailings) and 44.7 mg/kg (control) and these were significantly different (p< 0.0). the heavy metal concentration uptake of P. di-latatum probably originated from the mine tailings. this was confirmed by the metal composition (range) of the soil mine tailings: Mn [72.0-173.0 mg/kg]; zn [12.0-30.0 mg/kg]; cu [15.0-37.0 mg/kg]; Pb [3.0-6.0 mg/kg]; cd [< 1.0 mg/kg] and co [1.0-3.0 mg/kg]. For the control soil samples the heavy metal composition was: Mn [18.0-22.0]; zn [3.0-6.0]; cu [6.0-11.0]; Pb [1.0-2.0]; cd [<...

Copper is one of the most important trace elements in municipal solid waste (MSW) combustion. Knowledge of the speciation of copper is fundamental for the understanding of the effects of copper compounds on the combustion chemistry, for the evaluation of the environmental effects of copper in ash leachates and for the development of methods to recover copper from the MSW combustion ash. In this work an investigation of the speciation of copper in four ash flows from a bubbling fluidized bed boiler using synchrotron based X-ray absorption spectrometry is reported. The results showed that copper occurs in oxidation states zero, +I and +II in the bed ash and the cyclone ash, i.e. 10-20 % Cu(0), 25-35 % Cu(I), 50-60 % Cu(II), whereas the filter ash contained copper only in oxidation state +II. The most common copper compounds in the bed ash are copper metal, Cu 2 O, CuO and mixed oxides, such as CuCr 2 O 4 . The cyclone ash probably contained a mix of copper metal, Cu 2 O, CuCl, Cu(OH) 2 and CuSO 4 •5H 2 O,

is article describes remediation options for wind-remobilised old tailings at an 81year Pb-Zn-Ag mine in NW-Argentina. Long-term exposure of the dry surface of the older impoundments to wind led to spread of tailings over 2.5km2. Scoping-level geochemical characterisation included grain-size analysis, ICP-MS whole-rock geochemistry, XRD mineralogy, ABA and SPLP tests, and sequential extraction. Results suggested that high Pb-Zn contents are restricted to remobilised waste material and no leaching to the underlying soil occurred. us, the thickness was the driving factor to de ne remediation options. For sectors with up to 0.3m (22%), excavation and mobilisation was suggested. For thicknesses between 0.3 and 0.6m (78%), re-vegetation without impermeabilization was considered the best option. For in-situ old tailings (0.1km2), surface impermeabilization and re-vegetation was strongly suggested.

Complexing capacity of naturally occurring ligands in Vitis vinifera (Tempranillo variety) wines has been studied with respect to two target metals (Cu and Zn) by Differential Pulse Anodic Stripping Voltammetry (DPASV). Eight commercial wines of two certified brands of origin (CBO) and a young wine along its vinification process were monitored. Conditional stability constants and total complexing ligand(s) concentration have been calculated for both metals. Discussion of the particular electrochemical response for Cu and Zn for all samples is presented. A followup of the Cu stripping response allowed differentiating a commercial wine from one under processing related to the cupric casse phenomenon. Interaction of Cu with two molecular forms of cyanidin has been theoretically modeled at natural wine pH.

Zn and Cu interactions with three selected flavonoids (catechin, quercetin and rutin) have been electrochemically monitored. It has been shown that catechin takes 1 atom of metal per molecule; quercetin takes 2 atoms, and rutin is able to take up to 3 atoms. Not all ligands bind metals equally strong, and weakly bonded metals can be distinguished. Zn shows a sluggish kinetics and, at the same time, the highest conditional formation constants. The method could be applied to a real sample. Theoretical models are proposed for the most favourable compounds.

The distribution of copper(II) in species of different stability in some estuarine and sea water samples (Adriatic Sea) was investigated by a method based on the sorption of the metal ion on a strongly sorbing resin, Chelex 100, whose sorbing properties have been previously characterized. From them, it is possible to predict very high values of detection windows at the considered conditions, for example side reaction coefficient as high as 10 10 at pH 7.5. Strong copper(II) species in equilibrium with Chelex 100 were detected, at concentration 2-20 nM, with a reaction coefficient approximately 10 10.6 at pH 7.45 in sea water, strictly depending on the acidity. They represent 50-70% of the total metal ion and are the strongest copper(II) complexes found in sea water. Weak complexes too were detected in all the samples, with reaction coefficient lower than ca. 10 9 at the same pH. The method applied, named resin titration (RT), was described in a previous investigation, and is here modified in order to be carried out on oceanographic boat during a cruise in the Adriatic Sea.

The veracity of the free ion activity model (FIAM) was tested by examining the acute (48 h) valve movement responses (VMR) (measured in terms of the duration of valve opening) of the Australian tropical freshwater unionid bivalve, Velesunio angasi to increasing concentrations of total Mn or U, in a standard synthetic water under conditions of varying pH (5.0-6.0) and/or dissolved organic carbon (model fulvic acid, FA) concentrations (0 -8.9 mg l -1 ). Valve movement behaviour, measured using an automated data acquisition system, was shown to be a quantifiable and rapid, real-time endpoint for assessing the toxic effects of Mn and U exposures. For Mn, the VMR of V. angasi were independent (P\0.05) of pH and/or model FA concentration. In contrast, VMR to U exposures were highly dependent (P50.05) on pH and/or model FA concentration; individuals were more sensitive to U at low pH and model FA concentrations. Valve movement responses to Mn were directly proportional to the activity of the free metal ion (Mn 2 + ), which is consistent with the FIAM. In contrast, VMR to U were regarded as an 'exception' to the FIAM, since they were a weighted function of the activities of the free metal ion and the 1:1 metal hydroxide species (i.e. 1.86×UO 2 2 + +UO 2 OH + ). Additionally, the effect of U on V. angasi demonstrates the importance of examining VMR at more than one pH. At a fixed pH, the results for U were consistent with the FIAM (i.e. response was directly proportional to UO 2 2 + ); only when pH was altered, were the results inconsistent with the FIAM. The inconsistency in the VMR of V. angasi to U exposures in this study, together with similar examples from other studies using different metals (e.g. Al or Zn), raises questions regarding the veracity of the FIAM. A detailed examination of the conceptual development of the FIAM is required to probe its apparent failure to describe several metal -organism interactions.

AbstractÐSurface coatings (bio®lms and associated minerals) were collected on glass slides in the oxic surface waters of Cayuga Lake (New York State, U.S.A.) and were used to evaluate the relative contributions of Fe, Mn and Al oxides and organic material to total observed Pb and Cd adsorption by the surface coating materials. Several alternative selective extraction techniques were evaluated with respect to both selectivity and alteration of the residual unextracted material. Pb and Cd adsorption was measured under controlled laboratory conditions (mineral salts solution with de®ned metal speciation, ionic strength 0.05 M, 258C and pH 6.0) before and after extractions to determine by dierence the adsorptive properties of the extracted component(s). Hydroxylamine hydrochloride (0.01 M NH 2 OHÁHCl+0.01 M HNO 3 ) was used to selectively remove Mn oxides, sodium dithionite (0.3 M Na 2 S 2 O 4 ) was used to remove Mn and Fe oxides, and 10% oxalic acid was used to remove metal oxides and organic materials. Several other extractants were evaluated, but preliminary experiments indicated that they were not suitable for these experiments because of undesirable alterations of the residual, unextracted material. The selected extraction methods removed target components with eciencies between 71 and 83%, but signi®cant amounts of metal oxides and organic materials other than the target components were also removed by the extractants (up to 39%). Nonlinear regression analysis of the observed Pb and Cd adsorption based on the assumption of additive Langmuir adsorption isotherms was used to estimate the relative contributions of each surface coating constituent to total Pb and Cd binding of the bio®lms. Adsorption of Cd to the lake bio®lms was dominated by Fe oxides, with lesser roles attributed to adsorption by Mn and Al oxides and organic material. Adsorption of Pb was dominated by Mn oxides, with lesser roles indicated for adsorption to Fe oxides and organic material, and the estimated contribution of Al oxides to Pb adsorption was insigni®cant. The ®tted Pb adsorption isotherm for Fe oxides was in excellent agreement with those obtained through direct experiments and reported in independent investigations. The estimated Pb distribution between surface coating components also agreed well with that previously predicted by an additive adsorption model based on Pb adsorption isotherms for laboratory surrogates for Mn, Fe and Al oxides and de®ned biological components.

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Wolkersdorfer, Ch.; Sartz, L.; Weber, A.; Burgess, J.; Tremblay, G. (Editors) Abstract Mine drainage a ects waters locally and regionally and can have far reaching environmental and economic impacts. erefore, it is important to be able to quantify the changes in hydrochemistry and to be able to measure the extent of the impacts of mine waters to be able to assess when mitigation steps need to be taken, and to decide on the best methods of mitigation and remediation based on scienti c baseline studies. We present ndings from a study area that extends from the West Rand Gold eld of the Witwatersrand, South Africa, to Hartbeespoort Dam in the North and that encloses protected national spaces, including the internationally recognised UNESCO site known as the Fossil Hominid Site of South Africa (FHSoSA), locally referred to as the Cradle of Humankind World Heritage Site (COH WHS). e research results highlight a need for further investigations to provide realistic solutions that can be im...

Municipal solid waste composts (MSWC) are extensively utilized as organic soil conditioners and fertilizers in agricultural fields across many countries. However, the use of MSWC can lead to heavy metal pollution in soil and plants, which may adversely affect plant growth. This study examined the impact of MSWC on the heavy metal content in plants and soil across various pH levels. The experiment was conducted in a pot setting with three replications. The research findings indicated that MSWC application increased the levels of copper (Cu) and zinc (Zn) in soils but had no significant effect on lead (Pb), nickel (Ni), manganese (Mn), and iron (Fe) levels. Additionally, increases were observed in the Cu, Zn, and Fe content in plants, while Pb and Ni content remained unchanged. Cu, Zn, and Fe are essential for plant growth, and their enhancement in both soil and plants is a direct result of their relatively high presence in the MSWC used. The soil-plant transfer coefficients show that the transfer of heavy metals from soil to plants is highest under acidic conditions, indicating that the heavy metal content in MSWC can vary depending on soil pH and application rate. Therefore, it is crucial to carefully analyze and evaluate the heavy metal contents of soil and compost samples before employing MSWC in agricultural fields.

A laboratory experiment was conducted to evaluate the retention of copper (Cu) by sulphide mine tailings previously treated with lime (calcium carbonate) and submerged with water over 10 years. Sub-samples of air-dried mine tailings (pH tailing range: 2.56 to 7.60) were equilibrated with 30 mL of 0.01 M CaCl 2 containing 100 mg Cu L -1 , as CuSO 4 .5H 2 O, for seven days at room temperature. Afterwards, they were centrifuged and filtered. The filtrates were analyzed for Cu, by atomic absorption spectrophotometer, and pH (pH equilibrium ). The amount of Cu retained by mine tailing solids was calculated based on the difference between the initial and equilibrium Cu concentrations. The sorption experiment was replicated two times. After the sorption step, extractable acid-soluble Cu in tailing samples was assessed by extraction with Mehlich-3 solution. Results indicated a significant positive effect of lime application rate on Cu sorption. The sorption coefficient was positively correlated (p<0.001) with both pH equilibrium and pH tailing . In general, desorption showed that the Cu sorption was not rigidly bound under acidic conditions. The percentage of Cu released in the tailings without lime was much more than that released in the limed tailings. A positive linear relationship was found between the amounts of Cu desorbed and the amounts of Cu previously adsorbed. Copper in mine tailings may leach into water, especially under acidic conditions. The results highlight the importance of maintaining neutral pH conditions in sulphide mine tailings in order to protect surface water from the hazards of soluble anthropogenic Cu.

The influence of the degree of cross-linking (DCL) on chitosan beads was studied. Chitosan was prepared from the exoskeleton of Cape rock-lobsters, collected from the surroundings of Cape Town, South Africa. The chitosan beads were characterized; the beads water contents and pK a varied in the range of 90-96% and 4.3-6.0, respectively, and were found to decrease with increasing DCL (0.0-34.0%). A pH-model, which described the reversibility of the metal adsorbed onto the beads, was used to predict the equilibrium properties of copper adsorption onto the cross-linked beads. The model accounts for the effect of pH and the important model parameters, the equilibrium adsorption constant (K ads ) and to a lesser extent the adsorbent adsorption capacity (q max ) showed to decrease with the DCL. The adsorbent capacity and the adsorption constant were determined as 3.8-5.0 mmol/g chitosan and (9-90) Â 10 À4 , respectively. The adsorption kinetics could be described using a shrinking core model and the effective diffusion coefficient (D eff ) was determined as (8.0-25.8) Â 10 À11 m 2 /s. It was found that D eff decreases with the DCL mainly due to the decreased in water content of the beads at high DCL.

The influence of the degree of cross-linking (DCL) on chitosan beads was studied. Chitosan was prepared from the exoskeleton of Cape rock-lobsters, collected from the surroundings of Cape Town, South Africa. The chitosan beads were characterized; the beads water contents and pK a varied in the range of 90-96% and 4.3-6.0, respectively, and were found to decrease with increasing DCL (0.0-34.0%). A pH-model, which described the reversibility of the metal adsorbed onto the beads, was used to predict the equilibrium properties of copper adsorption onto the cross-linked beads. The model accounts for the effect of pH and the important model parameters, the equilibrium adsorption constant (K ads ) and to a lesser extent the adsorbent adsorption capacity (q max ) showed to decrease with the DCL. The adsorbent capacity and the adsorption constant were determined as 3.8-5.0 mmol/g chitosan and (9-90) Â 10 À4 , respectively. The adsorption kinetics could be described using a shrinking core model and the effective diffusion coefficient (D eff ) was determined as (8.0-25.8) Â 10 À11 m 2 /s. It was found that D eff decreases with the DCL mainly due to the decreased in water content of the beads at high DCL.

The speciation of Cr, Zn, Cu and Pb in two metal finishing filter cakes (TX and ST) was investigated by X-ray absorption spectroscopy (XAS) complemented by X-ray fluorescence (XRF) and X-ray diffraction (XRD). XRF showed that concentrations of Cr, Zn, Cu and Pb were 1.4%, 0.19%, 0.20% and 0.01%, respectively, in TX, and 12.6%, 3.3%, 1.3% and 0.21% in ST. No crystalline phases were detected in TX by XRD whereas ST was dominated by calcite. Cr and Fe K edge XAS showed Cr to be trivalent and octahedrally coordinated, coprecipitated with Fe as Cr x Fe 1-x-(oxy)hydroxides in both filter cakes. Zn, P and Ca K edge XAS showed that 2ZnCO 3 •3Zn(OH) 2 and Zn 3 (PO 4) 2 were the dominant zinc-containing phases, with combined tetrahedral and octahedral coordination; Zn phases were slightly more crystalline in TX than ST. Pb L 3 edge X-ray absorption near edge spectroscopy (XANES) found that Pb was likely adsorbed on amorphous SiO 2. Cu, Si and S K edge XAS showed that all Cu was divalent, and the dominant copper phases were found to be Cu 2 Cl(OH) 3 , Cu(OH) 2 and CuSO 4 ⋅5H 2 O for ST, whereas Cu appeared to adsorb to amorphous SiO 2 for TX, which contained much less Pb. Cr is thus immobilized in the filter cakes in a phase with low solubility at environmentally feasible pH values, whereas Zn, Cu and Pb could be released when the pH decreases below 8 or above 11. These findings are significant for the development of waste management regulations and/or metal recovery methods (e.g., hydro/ pyrometallurgy).

This report provides an overview of the "SIMS Analysis: Development and Evaluation Program," which was executed at the Idaho National Engineering Laboratory from mid-FY-92 to the end of FY-96. It should be noted that prior to FY-1994 the name of the program was "In-Situ SIMS Analysis". This report will not go into exhaustive detail regarding program accomplishments, because this information is contained in annual reports which are referenced herein. In summary, the program resulted in the design and construction of an ion trap secondary ion mass spectrometer (IT-SIMS), which is capable of the rapid analysis of environmental samples for adsorbed surface contaminants. This SUMMARY A program entitled "SIMS Analysis: Development and Evaluation Program," was conducted at the Idaho National Engineering Laboratory from mid-FY-92 to the end of FY-96. It should be noted that prior to FY-1994 the name of the program was "In-Situ SlMS Analysis". The program had three broad objectives, which were 1. Demonstration of secondary ion mass spectrometry (SIMS) for chemical detection and sample characterization applications. SlMS and ion trap technology. 3. Technology transfer of instrument components to manufacturers and end users. These three objectives will be discussed sequentially.

Kinetic speciation of nickel, aluminium, and iron in fresh water has been investigated by cascade ultrafiltration followed by competing ligand exchange of the ultrafiltered fractions. Graphite furnace atomic absorption spectrometry was used to measure the kinetics of metal complex dissociation. Dissolved metal species were fractionated by cascade ultrafiltration. Metal speciation in each ultrafiltered fraction was then characterized as free metal ions, "labile" metal complexes (with dissociation rate constants ≥10 -3 s -1 ), "slowly labile" metal complexes (with dissociation rate constants >10 -6 s -1 ), and "inert" metal complexes (with dissociation rate constants <10 -6 s -1 ). The experimental results were compared with the predictions of a computerbased equilibrium speciation model, the Windermere humic aqueous model (WHAM) V. Cascade ultrafiltration coupled with kinetic speciation of the metal species in each molecular weight cut-off (MWCO) fraction provided a more comprehensive picture and insight into the physical and the chemical characteristics of the metal species than either ultrafiltration or measurement of dissociation kinetics alone.

Up to now, different approaches have been proposed for in situ trace metal speciation, based on the deployment of in situ devices such as Donnan Membrane device (DMT) and then analysis by ICP-MS [1], or by means of preconcentration systems hyphenated wih electrochemical detection such as gel integrated microelectrode (GIME) probe [2] or a direct in situ electrochemical stripping speciation method such as Absence Gradient Nernstian Equilibrium Stripping (AGNES) [3]. Although numerous in situ methods have been proposed, currently there is no reliable in situ probe for trace metal speciation at concentration levels present in natural systems. Regarding autonomy problems of in situ probes, electrochemical devices have the advantage of being easily available in smaller sizes and with the possibility to be operated with batteries. This work presents the probe ISIDORE developped for in situ trace metal speciation [4]. This probe is based on the hyphenation between a DMT and a screen-printe...

Heavy metals are stable and persistence environmental contaminant of soils. The vast increase in population growth, urbanisation and industrialization leads to increase in use of chemicals, which results in total loads of pollutants being delivered to the soil. Heavy metal pollution in soil environment and subsequent uptake in food chain by asquatic organisms and humans put public health at risks. However, even at lower concentrations heavy metals like Cd, Hg, Cr and Pb may exhibit extreme toxicity under certain condition. Thus, this makes regular monitoring to be more imperative and necessary. Total levels of microelements provide no or little information about their chemical nature or potential mobility and bioavailability in the soil. The bioavailability mainly depends on chemical forms, fractions or phases in which an element occurs and is essentially a function of soil chemistry and mineralogy. This paper therefore, reviews the occurrence of heavy metals in various geo-chemical...

Purpose: The objective was to evaluate the water quality based on physical and chemical parameters in different quadrants of an urban wetland and correlate variables that may show possible natural and anthropogenic polluting sources.   Theoretical framework: Wetlands are essential ecosystems for the maintenance of ecological balance, biodiversity of organisms, and water reserves. Studies on water quality in urban wetlands are important for understanding their preservation level, elucidating the need for possible conservationist actions.   Method/design/approach: The wetland area was divided into four quadrants; water samples were collected for analysis of physical and chemical. When possible, the results were compared with the limits established by the CONAMA Resolution 357/2005 (class 1), which deals with surface waters, and with the literature.   Results and conclusion: The Quadrant 3, which presented riparian forest, invasive species, and high deposition of solid waste, showed a ...

The Ria de Huelva is an estuarine zone into which flow the Odiel and Tinto rivers, polluted by trace metals. Total contents of Al, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Pb, Cd and Hg were determined in the < 630 and < 63 pm fractions of bed sediments. Total trace metal contents in the coarsest fraction are lower Ihan in the finest, although both are highly correlaled for mosl of the metals, allowing an easy grain size elTect correclÍon. Total concentrations of Cu, Zn, As, Pb and Hg are very high, having enrichmenl faclor indexes rangíng from 35-111. Important proportions of these are in easily soluble and reducible physico-chemical forms, which are readily available for living organisms.

The concept of liquid coacervate extraction (LCE) is deployed to accomplish metal speciation after appropriate derivatization of the target metallic species. The method involves the partitioning of the hydrophobic metal chelates, produced from the reaction of Cr with APDC, in the vesicular aggregates formed from an anionic surfactant with alkaline earth metals and a cosurfactant, which are separated from the bulk aqueous phase. Under the established experimental conditions, the method offers high reproducibility, very low detection limits and recoveries in the range of 95 -104%. Moreover, the method affords high tolerance for EDTA, which is used as a masking agent in order to avoid interferences from co-extracted metals. Validation of the outlined method was performed by analysing a certified reference material (BCR 544) yielding recoveries higher than 94% for both Cr oxidation states.

We investigated the binding of Cd, Cu, and Zn to metallothionein (MT) and other metal‐binding proteins in free‐living wood mice (Apodemus sylvaticus L.) captured in four areas along a metal pollution gradient. We measured total and cytosolic Cd, Cu, and Zn concentrations in mouse liver and kidney by means of inductively coupled plasma—mass spectrometry (ICP‐MS). Total (Cu, Cd, Zn)‐MT levels were determined in the same tissues by means of the cadmium thiomolybdate saturation assay. Metal speciation of metalloproteins was studied by means of size‐exclusion high‐performance liquid chromatography‐ICP‐MS. Liver and kidney of wood mice from the site adjacent to the pollution source showed the highest Cd and Zn concentrations (total and cytosolic) and (Cu, Cd, Zn)‐MT levels compared to the other sites farther away from the pollution source. No or only small site differences in tissue Cu concentrations were observed. Almost all the variation (85–95%) in hepatic and renal (Cu, Cd, Zn)‐MT lev...

The term bioavailability has many different meanings across various disciplines of toxicology and pharmacology. Often bioavailability is concerned with human health aspects such in the case of lead (Pb) ingestion by children. However, some of the most contaminated sites are found in nonpublic access facilities (Department of Defense or Energy) or in remote regions as a result of mining or industrial practices in which ecoreceptors such as plants, animals, and soil organisms are the primary concerns as well as the potential for food-chain transfer. In all cases, the endpoint requires movement of the element across a biological barrier. The still utilized approach to base risk assessment on total metal content in soils is an outdated endeavor and has never been proved to be scientifically sound. Yet to reverse this trend, much work is required to establish baseline bioavailability measurements and to develop complementary methods that are capable of predicting bioavailability across a whole range of impacted media in a cost-efficient manner. Thus, regulators have recognized site-specific human health risk assessments play a key role in decision-making processes at contaminated sites. Bioavailability issues surrounding metal-contaminated soils and media have been an area of intense research. For obvious ethical reasons, we cannot solicit humans, in particular the sensitive population of children, from the general population for experimental purposes to examine the long-term harmful effect of metals in soils. However, some adult human feeding studies have been accomplished under tight medical supervision and with very small doses. One option to understand and relate bioavailability in humans is to employ animal surrogates; however, the physiology of most animals is different than that of humans but good correlations have been achieved despite the dose-response paradigm not being identical. The biggest drawback of in vivo studies to examine metal bioavailability to an appropriate ecoreceptor, be it human, plant, or soil organism, is the tremendous cost and time involved relative to chemical and physical surrogates. Chemical surrogate methods generally only require knowledge of the total metal content so that a percent bioaccessible number can be generated from in vitro extractions that simulate digestive systems or mimic responses to sensitive ecoreceptors. However, there is not a consensus as to which of the many in vitro methods is the best analogy to an ecoreceptor uptake and the same can be said for in vivo animal models to mimic human response as well. Further, there is yet to be a single in vitro method that can account for more than a few elements for a specific exposure pathway (e.g., Pb and/or arsenic (As) for human health). These in vitro tests require honest and accurate validation against in vivo bioavailability measurements, but most of all would benefit from metal speciation methods to identify the forms of metals allowing their release. Adaptation of spectroscopic speciation techniques to identify metal(loid) phases is extremely beneficial in bioavailability research to understand the variability of biologically available metal uptake, to manipulate the ecosystem to reduce bioavailability via in situ amendments, to monitor the long-term stability of elements to ensure bioavailability indicators do not change over time, and to develop comprehensive predictive models based on speciation.

This paper reports the results of an investigation on the performance of the diffusive gradient in thin film technique (DGT) as a speciation tool for trace elements (TEs) in artificial human gastrointestinal fluids. The validity of Cd, Pb, and Zn sampling by DGT in digestive fluids was checked. The TE bioaccessibility in highly contaminated soils was determined using the in vitro Unified Barge Method (UBM) test. DGT devices were deployed in the gastrointestinal solutions obtained after carrying out the UBM test. The computer speciation code JESS (Joint Expert Speciation System) was used to predict the metal speciation of Cd, Pb, and Zn. Combining the in vitro test with the DGT technique and JESS provided an approach to the TE species available for transport across the intestinal epithelium. The gastrointestinal absorption of ingested TE ranged from 8 to 30% for Cd, 0.6 to 11% for Pb, and 0.8 to 7% for Zn and was influenced by TE speciation. In this original approach, the DGT technique was found to be simple and reliable in the investigation of TE chemical speciation in digestive fluids. Extrapolation to the in vivo situation should be undertaken very cautiously and requires further investigation.

This paper reports the results of an investigation on the performance of the diffusive gradient in thin film technique (DGT) as a speciation tool for trace elements (TEs) in artificial human gastrointestinal fluids. The validity of Cd, Pb, and Zn sampling by DGT in digestive fluids was checked. The TE bioaccessibility in highly contaminated soils was determined using the in vitro Unified Barge Method (UBM) test. DGT devices were deployed in the gastrointestinal solutions obtained after carrying out the UBM test. The computer speciation code JESS (Joint Expert Speciation System) was used to predict the metal speciation of Cd, Pb, and Zn. Combining the in vitro test with the DGT technique and JESS provided an approach to the TE species available for transport across the intestinal epithelium. The gastrointestinal absorption of ingested TE ranged from 8 to 30% for Cd, 0.6 to 11% for Pb, and 0.8 to 7% for Zn and was influenced by TE speciation. In this original approach, the DGT technique was found to be simple and reliable in the investigation of TE chemical speciation in digestive fluids. Extrapolation to the in vivo situation should be undertaken very cautiously and requires further investigation.

The toxicity of iv injected hydrophilic aluminum complex tris(maltolate)aluminum(III) was studied in New Zealand white rabbits for a period of time ranging from 5 to 63 wk. Animals were injected 3-5 times a week with 1 mL of 7.5 mM Al(malt)3 and one rabbit with a dose 10 times higher after 14 wk of treatment. Autopical examination was performed on all animals. Chemoclinical analysis (glucose, urea, creatinine, cholesterol, bilirubin, alanin aminotransferase, aspartate aminotransferase, alkaline phosphatase, ~/-glutamyltransferase, LDH, CK, total protein, triglycerides, and Ca 2+) gave no variation in treated animals with respect to the control. The toxicological data show a moderate systemic general toxicity at doses far higher than those used in similar previous experiments using Al(acac)3 (acac = 2,4 pentanedionate), a hydrolytically stable and more lipo-*Author to whom all correspondence and reprint requests should be addressed.

A soil column experiment was carried out to investigate the effects of inoculation of bacteria on metal bioavailability, mobility and potential leachability through single chemical extraction, consequential extraction and in situ soil solution extraction technologies. Results showed that bacteria inoculated, including Azotobacter chroococcum, Bacillus megaterium and Bacillus mucilaginosus, may pose both positive and negative impacts on bioavailability and mobility of heavy metals in soil, depending on the chemical nature of the metals. The activities of bacteria led to an increase of water dissolved organic carbon (DOC) concentration and a decrease of pH value, which enhanced metal mobility and bioavailability (e.g. an increase of water-soluble and HOAc-soluble Zn). On the other hand, bacteria could immobilize metals (e.g. a great reduction of water-soluble Pb) due to the adsorption by bacterial cell walls and possible sedimentation reactions with phosphate or other anions produced through bacterial metabolism.

A soil column experiment was carried out to investigate the effects of inoculation of bacteria on metal bioavailability, mobility and potential leachability through single chemical extraction, consequential extraction and in situ soil solution extraction technologies. Results showed that bacteria inoculated, including Azotobacter chroococcum, Bacillus megaterium and Bacillus mucilaginosus, may pose both positive and negative impacts on bioavailability and mobility of heavy metals in soil, depending on the chemical nature of the metals. The activities of bacteria led to an increase of water dissolved organic carbon (DOC) concentration and a decrease of pH value, which enhanced metal mobility and bioavailability (e.g. an increase of water-soluble and HOAc-soluble Zn). On the other hand, bacteria could immobilize metals (e.g. a great reduction of water-soluble Pb) due to the adsorption by bacterial cell walls and possible sedimentation reactions with phosphate or other anions produced through bacterial metabolism.