Tea Zuliani

Environmental impact of toxic elements in red mud studied by fractionation and speciation procedures.

Aluminum (Al) is mostly produced from bauxite ore, which contains up to 70% of Al(2)O(3) (alumina). Before alumina is refined to aluminum metal, it is purified by hot alkaline extraction. As a waste by-product red mud is formed. Due to its high alkalinity and large quantities, it represents a severe disposal problem. In Kidričevo (Slovenia), red mud was washed with water before disposal, and after drying, covered with soil. In Ajka (Hungary), the red mud slurry was collected directly in a containment structure, which burst caused a major accident in October 2010. In the present work the environmental impact of toxic elements in red mud from Kidričevo and Ajka were evaluated by applying a sequential extraction procedure and speciation analysis. The predominant red mud fraction was the insoluble residue; nevertheless, environmental concern was focused on the highly mobile water-soluble fraction of Al and Cr. Al in the water-soluble Ajka mud fraction was present exclusively in form of toxic [Al(OH)(4)](-), while Cr existed in its toxic hexavalent form. Comparative assessment to red mud from Kidričevo (Slovenia) with a lower alkalinity (pH 9) with that from Ajka demonstrated significantly lower Al solubility and the presence of only trace amounts of Cr(VI), confirming that disposal of neutralized mud is environmentally much more acceptable and carries a smaller risk of ecological accidents. Since during the Ajka accident huge amounts of biologically available Al and moderate Cr(VI) concentrations were released into the terrestrial and aquatic environments, monitoring of Al and Cr(VI) set free during remedial actions at the contaminated site is essential. Particular care should be taken to minimize the risk of release of soluble Al species and Cr(VI) into water supplies and surface waters.

Analytical advances in butyl-, phenyl- and octyltin speciation analysis in soil by GC-PFPD.

The development and validation of a method for organotin analysis in soils, including butyl-, phenyl- and octyl-tins, are described in this study. The influence of pretreatment step based on sample lyophilization was first studied. Different solid-liquid extraction techniques including mechanical stirring (MSAE), accelerated solvent (ASE), microwave (MAE) and ultrasound (UAE), were compared. MSAE gave the best recoveries and repeatability and was thus chosen for OTC extraction from soils. Then, ethylation/extraction step before GC-PFPD analysis was investigated and the best derivatisation conditions were assessed in order to achieve a simple, non-expensive and reliable routine procedure. Finally, the robustness of the method was tested by the analysis of several soils with different organic matter content allowing the validation of developed protocol. The method appears to be reliable and accurate for the OTC determination in a broad range of soils.

Development of the extraction method for the simultaneous determination of butyl-, phenyl- and octyltin compounds in sewage sludge

The toxicity and bioaccumulation of organotin compounds (OTCs) led to the development of sensitive and selective analytical methods for their determination. In the past much attention was assigned to the study of OTCs in biological samples, water and sediments, coming mostly from marine environment. Little information about OTCs pollution of terrestrial ecosystems is available. In order to optimise the extraction method for simultaneous determination of butyl-, phenyl- and octyltin compounds in sewage sludge five different extractants (tetramethylammonium hydroxide, HCl in methanol, glacial acetic acid, mixture of acetic acid and methanol (3:1), and mixture of acetic acid, methanol and water (1:1:1)), the presence or not of a complexing agent (tropolone), and the use of different modes of extraction (mechanical stirring, microwave and ultrasonic assisted extraction) were tested. Extracted OTCs were derivatised with sodium tetraethylborate and determined by gas chromatography coupled with mass spectrometer. Quantitative extraction of butyl-, phenyl- and octyltin compounds was obtained by the use of glacial acetic acid as extractant and mechanical stirring for 16h or sonication for 30 min. The limits of detection and quantification for OTCs investigated in sewage sludge were in the ng S ng(-1) range.

Effective reduction of polyatomic interferences produced by high chloride and carbon concentrations in determination of Cr(VI) by FPLC-ICP-MS

Determination of Cr(VI) in aqueous samples including carbonate matrix solutions was performed by fast protein liquid chromatography (FPLC) coupled to inductively coupled plasma mass spectrometry (ICP-MS). NaCl was used for separation of Cr species representing a high burden of total dissolved solids for plasma. In addition, detection of Cr species in the NaCl and carbonate matrix was severely compromised also by chlorine and carbon polyatomic interferences at m/z 52 and 53. The influence of high amounts of chloride and carbonate ions on detection of Cr species was investigated using ICP-MS with a High Matrix Introduction (HMI) system, which reduced the sample aerosol transport and enabled direct analysis of separated Cr species in the presence of up to 4% NaCl. The potential of Helium Collision mode (He mode) and High Energy Collision Mode (HECM) to reduce polyatomic interferences from chlorine and carbon on m/z 52 and 53 was also evaluated. It was experimentally proven that for efficient removal of chlorine and carbon polyatomic interferences HECM instead of commonly used He mode should be applied. By applying HMI and HECM, determination of Cr(VI) in carbonate buffer matrices using NaCl as eluent is possible, following the most abundant Cr 52 and 53 isotopes. Despite the use of HMI and HECM, which significantly reduce the analyte transport to plasma and detector, low LODs were obtained for Cr(VI): 0.01 ng mL−1 at m/z 50, 0.06 ng mL−1 at m/z 52 and 0.02 ng mL−1 at m/z 53. The repeatability of the measurement (5 ng Cr(VI) mL−1) was better than ±1.5%. The simple solution of efficient lowering of the blank at low pH arising from a stainless steel injection needle was also demonstrated by the use of the reverse injection of samples.

The determination of Cr(VI) in corrosion protection coatings by speciated isotope dilution ICP-MS

Chromium conversion coatings are used as decorative finishes and to improve the corrosion protection and strengthen the wear resistance of metallic surfaces. Chromium electroplating frequently involves the use of hexavalent chromium (Cr). To reduce environmental impacts, several EU directives restricted its use to threshold values of 0.1% Cr(VI) by weight per homogeneous material in vehicles, and 1000 mg kg−1 of Cr(VI) in electronic and electrical equipment. There are few analytical procedures reported that comply with legislative demands, therefore, in our work a selective, quantitative and sensitive analytical procedure for determination of Cr(VI) in the corrosion protection coatings was developed. The investigation was performed on metallic plates homogeneously treated by chromium conversion or hard chrome coatings on copper or zinc electroplated steel surfaces. An alkaline solution (pH 12) was used for ultrasonic extraction of Cr(VI). Speciation analysis was performed by anion-exchange HPLC-ICP-MS. Species interconversions during the analytical procedure were followed using enriched isotopic solutions of 50Cr(VI) and 53Cr(III). To prevent Cr(III) oxidation, Tris, EDTA or MgCl2 was added along with a double isotopically enriched spike and extractions were performed over different time periods. Under optimal conditions that prevent any species interconversion (30 min ultrasonic extraction at 70 °C using 2% NaOH + 3% Na2CO3 + MgCl2 as an extraction agent), six consecutive extractions were necessary to quantitatively extract Cr(VI) from the protective layers; its content was determined by speciated isotope dilution ICP-MS. Concentrations in the samples investigated ranged from 2 to 7 ng of Cr(VI) per mm2. The accuracy of the HPLC-ICP-MS determinations was checked by analysis of the certified reference material CRM 545, Cr(VI) in welding dust, using both external calibration and speciated ID-ICP-MS. Good agreement was obtained between the determined and the reported certified values (±0.7% for external calibration and ±0.2% for speciated ID-ICP-MS). The high sensitivity of the procedure developed (LOQ 0.0107 ng Cr(VI) per mm2 on a surface of 250 mm2) and the possibility to use external calibration for quantification of separated Cr(VI) instead of ID-ICP-MS allows its application to be extended to the routine laboratory use.

Chromate in food samples: an artefact of wrongly applied analytical methodology?

Recently several papers were published in highly ranked journals on the presence of Cr(VI) in tea infusions, bread samples and plants. These statements were made on the basis of determination of total Cr concentrations in alkaline and aqueous sample extracts by ETAAS, without applying any speciation analysis. If Cr(VI) really exists in bread samples and tea infusions, consumption of bread and tea would represent long-term chronic exposure to Cr(VI) and a health threat for the majority of the human population. It is well accepted that due to the presence of organic matter foodstuffs of plant and animal origin cannot contain Cr(VI). Therefore, to show that the reported data on the presence of Cr(VI) in foodstuffs are an artefact of inappropriately applied analytical methodology, investigation of speciation was carried out by high performance liquid chromatography-inductively coupled plasma mass spectrometry (HPLC-ICP-MS). 50Cr(VI) and 53Cr(III) stable isotopes were used to follow species interconversions during the extraction procedures. Separated Cr species eluted from the column were followed at m/z 50, 52 and 53. The high sensitivity of the HPLC-ICP-MS method (LOD for m/z 52, 0.03 μg Cr(VI) L−1) enabled reliable determination of Cr(VI) at concentration levels that were much lower than the total Cr content present in sample extracts. The speciation analysis data demonstrated that in all samples analysed Cr(VI) concentrations were below the LOD. In tea infusions 50Cr(VI) was almost completely reduced due to the presence of antioxidants, while the high content of organic matter in bread appreciably reduced 50Cr(VI) even in highly alkaline (pH 12) bread extracts. The data confirmed that Cr(VI) does not exist in foodstuffs of plant origin and provided some conclusive evidence that the same can be expected for foods of animal origin.

Comprehensive study of the parameters influencing the detection of organotin compounds by a pulsed flame photometric detector in sewage sludge.

An investigation of the operating conditions of a pulsed flame photometric detection (PFPD) system for the determination of organotin compounds (OTCs) in sewage sludge is reported. During the analyses, some spectral interferences were observed. For their elimination detector parameters such as gate delay and gate width were investigated. In addition, the applicability of three different internal standards was evaluated. Under optimised analytical conditions (gate delay 3 ms, gate width 2 ms, tripropyltin as internal standard) limits of detection (LOD) were determined. The LOD for butyltins ranged between 8 and 16 ng Sn g(-1), for phenyltins around 8 ng Sn g(-1) and for octyltins between 5 and 10 ng Sn g(-1). Since there is no certified reference material (CRM) available for sewage sludge, the accuracy of the analytical procedure was checked by the analysis of CRM PACS-2 (marine sediment) and a spiked sludge sample. Good agreement between determined and certified values was obtained. Sewage sludge from a local wastewater treatment plant was analysed and the results compared with data from the literature.

Content of trace elements and chromium speciation in Neem powder and tea infusions

Total concentrations of selected trace elements in Neem powder and in Neem tea were determined by inductively coupled plasma mass spectrometry (ICP-MS). The data revealed that despite high total concentrations of the potentially toxic elements Al and Ni in Neem powder, their amounts dissolved in Neem tea were low. Total concentrations of the other toxic elements Pb, As and Cd were also very low and do not represent a health hazard. In contrast, total concentrations of the essential elements Fe, Cu, Zn, Se Mo and Cr in Neem powder were high and also considerable in Neem tea. Consuming one cup of Neem tea (2g per 200 mL of water) covers the recommended daily intakes for Cr and Se and represents an important source of Mo and Cu. Speciation analysis of Cr by high performance liquid chromatography (HPLC) coupled to ICP-MS with the use of enriched Cr isotopic tracers to follow species interconversions during the analytical procedure demonstrated that toxic Cr(VI) was not present either in Neem powder or in Neem tea. Its concentrations were below the limits of detection of the HPLC-ICP-MS procedure applied. The speciation analysis data confirmed that even Cr(VI) was added, it was rapidly reduced by the presence of antioxidants in Neem leaves. By the use of enriched Cr isotopic spike solutions it was also demonstrated that for obtaining reliable analytical data it is essential to apply the extraction procedures which prevent Cr species interconversions, or to correct for species transformation.

Leachability of Cr(VI) and other metals from asphalt composites with addition of filter dust.

The potential use of filter dust in asphalt composites for road construction was investigated. Filter dust contains high concentrations of metals, of which Cr(VI) and Pb are leached with water. Compact and ground asphalt composites with addition of 2% of filter dust by mass were studied. In order to evaluate their environmental impact, leachability tests were performed using water and salt water as leaching agents. The concentrations of Cr(VI) and Pb were determined in leachates over a time period of 182 days. The results indicated that Pb was not leached with leaching agents from asphalt composites. Cr(VI) was also not leached with leaching agents from compact asphalt composites. However, in ground asphalt composites, Cr(VI) was leached with water in concentrations up to 220 microg L(-1) and in salt water up to 150 microg L(-1). From the physico-mechanical and environmental aspects, filter dust can be used as a component in asphalt mixtures.

Environmental impacts of asphalt mixes with electric arc furnace steel slag.

Electric arc furnace (EAF) steel slag can be used as an alternative high-quality material in road construction. Although asphalts with slag aggregates have been recognized as environmentally acceptable, there is a lack of data concerning the potential leaching of toxic Cr(VI) due to the highly alkaline media of EAF slag. Leaching of selected water extractable metals from slag indicated elevated concentrations of total chromium and Cr(VI). To estimate the environmental impacts of asphalt mixes with slag, leachability tests based on diffusion were performed using pure water and salt water as leaching agents. Compact and ground asphalt composites with natural aggregates, and asphalt composites in which the natural aggregates were completely replaced by slag were prepared. The concentrations of total chromium and Cr(VI) were determined in leachates over a time period of 6 mo. After 1 and 6 mo, the concentrations of some other metals were also determined in the leachates. The results indicated that chromium in leachates from asphalt composites with the addition of slag was present almost solely in its hexavalent form. However, the concentrations were very low (below 25 μg L) and did not represent an environmental burden. The leaching of other metals from asphalt composites with the addition of slag was negligible. Therefore, the investigated EAF slag can be considered as environmentally safe substitute for natural aggregates in asphalt mixes.