Elements In Natural Waters Research Articles

Multivariate optimization and validation studies in on-line pre-concentration system for lead determination in drinking water and saline waste from oil refinery

The present paper proposes an on-line pre-concentration procedure for lead determination in drinking water and saline waste from oil refinery by flame atomic absorption spectrometry (FAAS). It is based on the sorption of lead (II) ions in a minicolumn of polyurethane foam loaded with 4-(2-pyridylazo)-resorcinol (PAR) reagent. The optimization step was performed using Doehlert matrix involving the variables: sampling flow rate (SR), buffer concentration (BC), pH and eluent concentration (EC). The validation process was performed considering the parameters: linearity and other characteristics of the calibration curve, analytical features of on-line system, precision, robustness, effect of other ions in the pre-concentration system and accuracy. Using the established experimental conditions, the procedure allows lead determination with detection limit (3 δ/ S) of 0.4 μg l −1, quantification limit (10 δ/ S) of 1.4 μg l −1, and a precision, calculated as relative standard deviation (RSD) of 5.7 ( n=8) and 2.1% ( n=8) for lead concentration of 5 and 50 μg l −1, respectively. The pre-concentration factor (PF) considering the ratio among the slopes of the analytical curves with and without pre-concentration is 51. The achieved recovery for lead determination in presence of several cations demonstrated that this procedure could be applied for analysis of water samples. The accuracy was confirmed by analysis of the standard reference material NIST 1640 Trace elements in natural water. The sorption process was characterized by the Langmuir isotherm. The method was applied for lead determination in drinking water collected in Salvador City, Brazil and in saline effluent samples from oil refinery. The lead content for 16 samples of drinking water analyzed varied from 0.77 to 6.98 μg l −1.

Carbonate complexation of yttrium and the rare earth elements in natural waters

Potentiometric measurements of Yttrium and Rare Earth Element (YREE) complexation by carbonate and bicarbonate indicate that the quality of carbonate complexation constants previously obtained via solvent exchange analyses are superior to characterizations obtained using solubility and adsorptive exchange analyses. The results of our analyses at 25°C are combined with the results of previous solvent exchange analyses to obtain YREE carbonate complexation constants over a wide range of ionic strength (0 ≤ I ≤3 molal). YREE carbonate complexation constants are reported for the following equilibria, M 3++nHCO 3 −⇌M(CO 3) n 3−2n+nH +, where n = 1 or 2. Formation constants written in terms of HCO 3 − concentrations require only minor corrections for ion pairing relative to the corrections required for constants expressed in terms of CO 3 2− concentrations. Formation constants for the above complexation equilibria, CO 3 Hβ 1=[MCO 3 +][H +][M 3+] −1[HCO 3 −] −1 and CO 3 Hβ 2=[M(CO 3) 2 −][H +] 2[M 3+] −1[HCO 3 −] −2, have very similar dependencies on ionic strength because the reaction MCO 3 ++HCO 3 −⇌M(CO 3) 2 −+H + is isocoulombic. Potentiometric analyses indicate that the dependence of log CO 3 Hβ 1 and log CO 3 Hβ 2 on ionic strength at 25°C is given as (A) log CO 3 H β n = log CO 3 H β n 0−4.088 I 0.5/(1+3.033 I 0.5)+0.042 I where CO 3 Hβ n 0 denotes a formation constant at 25°C and zero ionic strength. Recommended values for log CO3 Hβ 1 and log CO 3 Hβ 2 0, expressed in the form (element, −log CO 3 Hβ 1 0, −log CO 3 Hβ 2 0), are as follows: (Y, 2.85, 8.03), (La, 3.60, 9.36), (Ce, 3.27, 8.90), (Pr, 3.10, 8.58), (Nd, 3.05, 8.49), (Sm, 2.87, 8.13), (Eu, 2.85, 8.03), (Gd, 2.94, 8.18), (Tb, 2.87, 7.88), (Dy, 2.77, 7.75), (Ho, 2.78, 7.66), (Er, 2.72, 7.54), (Tm, 2.65, 7.39), (Yb, 2.53, 7.36), (Lu, 2.58, 7.29).

Evaluation of the mixtures ammonium phosphate/magnesium nitrate and palladium nitrate/magnesium nitrate as modifiers for simultaneous determination of Cd, Cr, Ni and Pb in mineral water by GFAAS

A method is described for the simultaneous determination of Cd, Cr, Ni and Pb in mineral water samples by graphite furnace atomic absorption spectrometry with a transversely heated graphite atomizer (THGA) and a longitudinal Zeeman-effect background correction system. The electrothermal behavior of analytes during pyrolysis and atomization steps was studied without modifier, in presence of 5 mug Pd and 3 mug Mg(NO3)2 and in presence of 50 mug NH4H2PO4 and 3 mug Mg(NO3)2. A volume of 20 muL of a 0.028 mol L-1 HNO3 solution containing 50 mug L-1 Ni and Pb, 10 mug L-1 Cr and 5 mug L-1 Cd was dispensed into the graphite tube at 20 °C. The mixture palladium/magnesium was selected as the optimum modifier. The pyrolysis and atomization temperatures were fixed at 1000 °C and 2300 °C, respectively. The characteristic masses were calculated as 2.2 pg Cd, 10 pg Cr, 42 pg Ni and 66 pg Pb and the lifetime of the graphite tube was around 600 firings. Limits of detection based on integrated absorbance were 0.02 mug L-1 Cd, 0.94 mug L-1 Cr, 0.45 mug L-1 Ni and 0.75 mug L-1 Pb, which exceeded the requirements of Brazilian Food Regulation that establish the maximum permissible level for Cd, Cr, Ni and Pb at 3 mug L-1, 50 mug L-1, 20 mug L-1 and 10 mug L-1, respectively. The recoveries of Cd, Cr, Ni and Pb added to mineral water samples varied within the 93-108%, 96-104%, 87-101% and 98-108% ranges, respectively. Results of analysis of standard reference materials (National Institute of Standards and Technology: 1640-Trace Elements in Natural Water; 1643d-Trace Elements in Water) were in agreement with certified values at the 95% confidence level.

The use of a portable total reflection X-ray fluorescence spectrometer for field investigation

A newly developed, portable total reflection X-ray fluorescence (TXRF) spectrometer was tested during a field campaign on Chilean lakes and a German river in January 2002. The field measurements were compared with laboratory measurements carried out on a stationary instrument in the German laboratory. For method validation certified reference material (NIST SRM 1640 Trace elements in natural water) and water samples from different freshwater sources were analyzed with both techniques and evaluated statistically. Based on these preliminary results, it could be concluded that the portable TXRF is a useful technique for the quantitative elemental screening of freshwater samples during field campaigns. Future tests with biological samples (e.g. biofilms and zooplankton), and suspended matter will provide information about the suitability of the portable TXRF for these materials.

Application of iminodiacetate chelating resin muromac A-1 in on-line preconcentration and inductively coupled plasma optical emission spectroscopy determination of trace elements in natural waters

On-line system incorporating a microcolumn of Muromac A-1 resin was used for the developing of method for preconcentration of trace elements followed by inductively coupled plasma (ICP) atomic emission spectrometry determination. A chelating type ion exchange resin has been characterized regarding the sorption and subsequent elution of 24 elements, aiming to their preconcentration from water samples of different origins. The effect of column conditioning, pH and flow rate during the preconcentration step, and the nature of the acid medium employed for desorption of the retained elements were investigated. A sample (pH 5) is pumped through the column at 3 ml min −1 and sequentially eluted directly to the ICP with 3 M HNO 3/HCl mixtures. In order to remove residual matrix elements from the column after sample loading a short buffer wash was found to be necessary. The effectiveness of the matrix separation process was illustrated. The procedure was validated by analyzing several simple matrices, Standard River water sample as well as artificial seawater. Proposed method can be applied for simultaneous determination of In, Tl, Ti, Y, Cd, Co, Cu and Ni in seawater and for multielement trace analysis of river water. Recovery at 1 μg l −1 level for the determination of investigated 24 elements in pure water ranged from 93.1 to 96% except for Pd (82.2%) and Pb (88.1%). For the same concentration level for seawater analysis recovery was between 81.9 and 95.6% except for Hg (38.2%).

Influence of water sample storage protocols in chemiluminescence detection of trace elements

This paper shows the influence of different sample storage protocols, on the chemiluminescence signal of some metal ions. The storage protocols studied were: acid addition (HCl or HNO 3) and no reagent addition to filtered and refrigerated ( T=4 °C) samples. Light emission was produced for the chemiluminescence reaction between luminol and hydrogen peroxide in buffer carbonate conditions (pH 10.8) catalysed by Cr(III), Co(II) and Cu(II). Batch and/or flow modes in different conditions were tested. Fe(II), Fe(III), Ni(II) and Mn(II) did not give chemiluminescence in the studied conditions. A parallel study of sensitivity and selectivity was performed. Then the presence or absence of the masking agent EDTA, added to samples or used in the carrier stream, is assayed. If the samples are acidified with HNO 3, a previous neutralisation is needed using batch mode. The determination of Cr(III) is independent of storage protocol by flow injection (FI) method; however, the determination of Co(II) or Cu(II) or total determination of three metals requires the conditioning of standards. Detection limits achieved are ranged between 0.5 and 2 μg l −1. For batch mode, detection limits are better for unacidified samples and worse for carbonate-neutralised samples. The influence of storage protocols was validated using standard metal mixtures and calibration solutions. The use of standard reference material (SRM© 1640) (Trace elements in natural water) corroborates the previous statements and validates the accuracy of the different approaches underlined. This paper demonstrates that it is possible to determine Cr(III) selectively in natural waters.

Comparison and evaluation of cloud point extraction and low-temperature directed crystallization as preconcentration tools for the determination of trace elements in environmental samples

A comparative study between cloud point extraction (CPE) and low-temperature directed crystallization (LTDC) is presented. Trace elements (Cd, Pb, Cr, Cu, Zn, Ni and Fe) were preconcentrated by both methods from model and natural water samples and the results were evaluated with respect to extraction efficiency, accuracy, precision, sample throughput and interferences. Flame atomic absorption spectrometry (FAAS) and inductively coupled plasma atomic emission spectrometry (ICP-AES) were used for the final measurements. The results indicate that these extraction and preconcentration procedures ensure the required accuracy and precision for the reliable identification and quantification of trace elements in natural waters. Drawbacks of each method identified can further assist the analyst towards a better application of each method depending on the target species, the detector employed and the application intended (routine analysis, trace analysis, speciation analysis, etc.).

Voltammetric Microsystem for Trace Elements Monitoring

The development of a voltammetric microsystem for monitoring and speciation studies of trace elements in natural waters is presented. This system was designed to provide an efficient coupling of the square-wave anodic stripping voltammetry (SWASV) detection with the permeation liquid membrane (PLM) technique. It consists of a voltammetric microcell, based on a gel-integrated Ir(Hg) microdisk array, a PLM and two micromachined channels for the sample and strip solutions respectively. The analytical performance of the microsystem was first assessed for Pb(II) and Cd(II) and then the simultaneous accumulation and detection of Cd(II), Pb(II) and Cu(II) from a synthetic sample solution was performed. The estimated detection limit of the free metal ion is 2 pM for Pb(II) and 75 pM for Cd(II) using 5 min as deposition time.

Determination of ultratrace elements in natural waters by solid-phase extraction and atomic spectrometry methods

A study was carried out on the preconcentration of ultratrace amounts of cadmium, lead, manganese, copper and iron from high-salinity aqueous samples and determination by atomic spectrometry methods. Sample volume, amount of resin, loading flow rate, and elution volume were optimized in order to obtain the simultaneous preconcentration of all the analytes. Quantitative recoveries were obtained by using 200 mg of iminodiacetic resin with a loading flow rate of 2 mL min(-1), elution volume of 3 mL and sample volume of 50-450 mL. Only copper in seawater samples was not completely retained by the resin (60-70% recovery), due to unfavorable competition of iminodiacetic-active groups with organically bound metal.To quantify the metals in the eluates, two atomic spectrometry techniques were compared: electrothermal atomization atomic absorption spectrometry (ETAAS) and inductively coupled plasma-optical emission spectrometry (ICP-OES) with simultaneous CCD detection system. Both techniques are suitable for sample analysis with detection limits of 1.0, 4.7, 3.3, 6.8, and 53 ng L(-1) using ETAAS and 12, 122, 3.4, 17, and 21 ng L(-1) using ICP-OES for Cd, Pb, Mn, Cu, and Fe, respectively. Relative standard deviations of the procedures ranged from 1.7 to 14% at the sub-microg L(-1) concentration level. The accuracy of both methods was verified by analyzing various certified reference materials (river water, estuarine water, coastal and off-shore seawater).

Atomic Absorption Determination of the Dissolved and Suspended Forms of Elements in Natural Water with Dynamic Sorption Preconcentration in Atomizers

* Institute of Fundamental Problems of Biology, Russian Academy of Sciences, Pushchino, Moscow oblast, Russia ** Department of Chemistry, Moscow State University, Vorob’evy gory, Moscow, 119899 Russia In natural water (river, sea, atmospheric, etc.) elements occur in dissolved and suspended forms. The data on the concentrations and ratio of these forms are important for geochemical and environmental studies. For the determination of ultralow concentrations of Ag, Bi, Cd, Pb, and Tl in dissolved (El diss ) and suspended (El susp ) forms and the total concentration (El diss + El susp ), we proposed a sorption–atomic-absorption method with the dynamic preconcentration of metals on the DETATA sorbent directly in a crucible electrothermal atomizer. A filtrate, unfiltered water sample, or solution obtained after the decomposition of a suspension (< 5– 50 mL) was pumped through a crucible microcolumn with holes of small diameter in the bottom and a graphite filter. The crucible microcolumn is a part (evaporation zone) of a two/three-chamber graphite electrothermal crucible–cell/crucible–cylinder–cell atomizer. The design of the atomizers provided independent programmed heating of the evaporation zone and the atomization zone for optimizing the processes and decreasing nonselective interferences and matrix effects. The cycle of the determination of elements in a solid matrix (concentrate, concentrate + suspension) commonly included drying, pyrolysis, and atomization ( 1800– 2600°e ) with the evaporation of elements to the isothermally heated zone. For the efficient suppression of interferences, we used the principles of element vapor filtration through graphite filters (between the evaporation and atomization zones) and fractional evaporation with the subsequent independent atomic-absorption analysis of the condensate.

Sorption-atomic absorption determination of trace elements in natural waters with dynamic preconcentration in electrothermal atomizers

A sorption–atomic absorption method was proposed for the determination of ultratrace amounts of suspended and soluble forms of Ag, Cd, Bi, Pb, and Tl in natural waters using a dynamic preconcentration of these forms (separately or simultaneously) on the DETATA sorbent placed in a crucible atomizer and the subsequent direct atomic absorption analysis of the concentrate. This method is characterized by high a sensitivity and provides for the determination of elements in small volumes of unique samples. The accuracy of the determination of element species was verified by different methods in the analysis of sea and river water, atmospheric precipitation, and suspensions.

In situ trapping of selenium hydride in rhodium-coated tungsten coil electrothermal atomic absorption spectrometry

A flow injection hydride generation manifold was coupled to a tungsten coil electrothermal atomizer for in situ collection of selenium. This strategy exploits selenium hydride trapping onto a double-layer coiled tungsten filament coated with rhodium. The hydride flows through a capillary quartz tube (20 mm long × 1.3 mm od × 0.5 mm id) positioned 1 mm from the modified tungsten coil surface. The capillary can be either inserted in the tip of the autosampler arm by replacing the last section of the PTFE sample delivery tube, or can be fixed in a silicone stopper. Signal stability and repeatability were observed over 300 atomization cycles using 300 µg Rh thermally reduced over the tungsten coil surface. The coil lifetime was extended to at least 2000 firings at 2300 °C. An enrichment factor of 200 was obtained for selenium after 60 s of hydride trapping for a sample flowing at 2.5 ml min−1. The detection limit, based on three times the standard deviation of the blank, was 50 ng l−1 Se with a sample throughput of 40 h−1. Method accuracy was evaluated by analysing ordinary mineral water using the proposed method and hydride generation atomic fluorescence spectrometry and water reference materials from the National Institute of Standards and Technology (SRM 1640 Trace Elements in Natural Water) and from High-purity Standards (Trace Metals in Drinking Water). No statistical differences were found between the values encountered by both techniques and the certified values by applying a t-test at the 95% confidence level.

Flow Sorption-Spectroscopic Analysis

Combinations of the dynamic sorption preconcentration of elements with spectroscopic determination techniques was considered. The use of sorption systems in flow spectroscopic techniques are discussed, and the evaluation of the efficiency of these systems in the preconcentration of elements is described. The application of flow sorption–spectroscopic techniques to the determination of elements in natural water, drinking water, soil, food stuffs, rocks, and ores is surveyed.

Determination of sub-parts-per-trillion levels of rare earth elements in natural waters by inductively coupled plasma time-of-flight mass spectrometry after flow injection on-line sorption preconcentration in a knotted reactor

A flow injection (FI) on-line sorption system, for the preconcentration and separation in a knotted reactor (KR), is coupled with inductively coupled plasma time-of-flight mass spectrometry (ICP-TOFMS) for the fast, selective and sensitive determination of ultra-trace concentrations of rare earth elements (REEs) in environmental waters. The on-line preconcentration and separation of the REEs is achieved by sorption of the REE complexes formed in the pH range 3.7–4.6 on the inner walls of a (300 cm × 0.5 mm) PTFE KR pre-coated with the chelating reagent 1-phenyl-3-methyl-4-benzoylpyrazol-5-one (PMBP) at a pH of 9.6. The analytes are eluted and transported to the ICP-TOFMS system with 2% (v/v) HNO3 containing 0.5 µg l−1 of Rh and In as internal standards, using ultrasonic nebulisation. The REEs are effectively preconcentrated and separated from the major matrix constituents—alkali and alkaline earth elements. Of particular significance is their separation from barium, which produces considerable isobaric interferences on some of the analytes. Using a preconcentration time of 30 s and a sample flow rate of 4.4 ml min−1, enhancement factors of 15 to 22 for the different REES are achieved. The detection limits (3σ) range from 3 to 40 pg l−1. The precision for 9 replicate determinations of 0.1 µg l−1 of each analyte is better than 5% (RSD). The accuracy of the method is demonstrated by the analysis of environmental waters and by recovery measurements on spiked samples.

On-line pre-concentration system for vanadium determination in drinking water using flow injection-inductively coupled plasma atomic emission spectrometry

An on-line vanadium preconcentration and determination system implemented with inductively coupled plasma atomic emission spectrometry (ICP-AES) associated to flow injection (FI) was studied. For the retention of vanadium, 2-(5-Bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) and Amberlite XAD-7 were used, at pH 3.7. The vanadium was removed from the microcolumn in countercurrent with nitric acid. An enrichment factor (EF) of 75 was obtained. The detection limit value for the preconcentration of 50 ml of aqueous solution of vanadium was 0.04 μg l −1. The precision for 10 replicate determinations at the 5 μg l −1 vanadium levels was 2.5% relative standard deviation (R.S.D.), calculated with the peak heights obtained. The calibration graph using the preconcentration system for vanadium was linear with a correlation coefficient of 0.9996 at levels near the detection limits up to at least 50 μg l −1. The accuracy of the method was demonstrated by analysing a standard reference material NIST SRM 1640 trace elements in natural water. The method was successfully applied to the determination of vanadium in drinking water samples.

Determination of ultratrace metals of group-13 elements in natural water by graphite-furnace AAS after preconcentration with solvent extraction and back extraction

The need for highly sensitive and reliable methods for the determination of ultratrace elements has been recognized in analytical chemistry and/or environmental science.The author has developed micro-volume back-extraction methods for the ultratrace analysis of gallium, indium and thallium.At first, the determination of gallium and indium at ng dm-3 levels in natural water samples was investigated.Gallium or indium was extracted into carbon tetrachloride as an ion pair of 5-sulfo-8-quinolinol chelate anion with tetradecyldimethylbenzyl-ammonium chloride, and subsequently back-extracted into 0.3cm3 of nitric acid solution for determination by GFAAS.In the case of indium, the extraction behavior of the ion associate was compared with that of the 8-quinolinolato complex.Secondly, the determination of thallium at ng dm-3 levels in natural water samples was investigated.Thallium is extracted into chloroform as the dithizonate complex, and subsequently back-extracted into 0.3cm3 of a nitric acid solution.A speciation analysis of Tl(I)and Tl(III)is performed by the masking of Tl(III)with citrate and/or the reduction of Tl(III)to Tl(I)with ascorbic acid.The detection limits obtained for these elements are sub ng dm-3 levels, based on more than 1000-fold preconcentration.

Studies on Bio-geochemical and Environmental Behaviors of Trace Elements- Chemical Speciation of Trace Elements in Natural Water

Studies on Bio-geochemical and Environmental Behaviors of Trace Elements- Chemical Speciation of Trace Elements in Natural Water

Chemical Stability of Large Organic Molecule-Metal Complexes Dissolved in Natural Water as Studied by Size Exclusion Chromatography/Inductively Coupled Plasma Mass Spectrometry

Abstract The chemical stability of large organic molecule-metal complexes (LOMMCs) dissolved in pond water were investigated by a hyphenated system of size exclusion chromatography/UV absorption detection/inductively coupled plasma mass spectrometry (SEC/UV/ICP-MS) after ultrafiltration using a filter with a molecular permeation limit larger than 10000 Da. LOMMCs dissolved in the preconcentrated pond water sample were observed at the retention times corresponding to molecular weights larger than 300000 Da (Peak I) and that of 10000—50000 Da (Peak II) in the chromatograms measured by UV absorption and ICP-MS. When the pH of the sample solution was varied from 7.0 to 0.5 by adding the HNO3 solution, the peak intensities of both Peak I and Peak II in these chromatograms decreased with the decrease in pH of the sample solution. These results indicate that LOMMCs were decomposed by addition of HNO3. Peak I was rapidly decomposed below pH 4, while Peak II was gradually decomposed over the pH range from 7.0 to 0.5. The decomposition curve of Peak I was similar to the solubility characteristics of hydroxides of Fe and Al. On the other hand, that of Peak II suggested the dissociations of metal complexes (Cu and Zn) with some biogenic organic molecules. It was concluded from these results that some colloidal particles of hydroxides of Fe and Al may be core materials of LOMMCs for Peak I, while some metal complexes with biogenic protein-like compounds may be LOMMCs for Peak II. The possible models for LOMMCs in pond water were proposed as ``a string-ball model'', which might interpret as the removal and preservation mechanisms for trace elements in natural water.

Determination of Continuous Size and Trace Element Distribution of Colloidal Material in Natural Water by On-Line Coupling of Flow Field-Flow Fractionation with ICPMS

The coupled technique here presented utilizes the size-separating capabilities of flow field-flow fractionation (FlFFF) and the high-sensitivity, multielement detection capabilities of inductively coupled plasma mass spectrometry (ICPMS). The system enables determinations of colloidal size and element distributions for 28 elements (including carbon) in natural waters. To cope with the low concentrations often found for colloids and trace elements in natural waters, the conventional FlFFF system has been modified to include an on-channel preconcentration procedure allowing injection of up to 50 mL of sample. The performance of the FlFFF−ICPMS system is further evaluated in terms of reproducibility and detection limits. The size distributions of six selected elements are given, and different colloidal distributions for the elements are discussed.

Multielement Profiling Analyses of Biological, Geochemical, and Environmental Samples as Studied by Analytical Atomic Spectrometry

Abstract The progress of modern analytical atomic spectrometry is briefly reviewed with emphasis on ICP-AES and ICP-MS; these provide some excellent analytical features such as high sensitivity, wide linear dynamic range, and multielement detection capability. Thus, the multielement determination of the major-to-ultratrace elements from % to sub-ppt (1 ppt = 10−12 g ml−1) level is possible for the biological, geochemical, and environmental samples. The standard or certified reference materials of plant, human blood serum, and the other biological samples were analyzed to establish the reliable analytical methods for the multielement determination by ICP-AES and ICP-MS. The modern analytical methods were applied to: (i) the correlation analysis of the elements in human blood serum, and (ii) the determination of rare earth elements in human blood serum on a personal basis. The speciation of trace elements in natural water was also carried out by the SEC (size exclusion chromatography)/UV absorption detection/ICP-MS combined system after ultrafiltration of the water samples. The SEC chromatograms indicated that most of trace elements in natural water existed as large organic molecule–metal complexes with the molecular weight of &amp;gt; 300000 and 10000—50000. In addition, trace elements in man and in the sea were discussed from the viewpoints of the geochemical classification of the elements on the earth, the Lewis’s acid-base theory, and the principle of HSAB (hard and soft acids and bases). Such multielement information allows the multielement profiling analyses of various samples to elucidate the elemental distributions, physicochemical characteristics, and behaviors of the major-to-ultratrace elements in relation with the biological functions or with the geochemical and environmental phenomena.