S. J. Parry

Iodine concentration and availability in atmospheric aerosol

Abstract Iodine has been determined in aerosol samples collected at a coastal site in southeast England using instrumental neutron activation analysis (INAA) and by an electrochemical technique, after aqueous extraction. Size distribution and enrichment factor data for the samples are consistent with a non-sea-salt source of iodine, presumably gas-to-particle conversion of volatile iodocarbons. On average, only ∼70% of INAA (i.e. total) iodine could be released from the aerosols as inorganic iodine by aqueous extraction at 95°C. Extraction at a more environmentally realistic temperature (20°C) decreased this yield to ∼25%. Through the use of high-energy UV light, which is known to destroy organic matter, the yield of aqueous extractable iodine at the lower temperature was increased for some samples. Thus, it appears likely that iodine is present in aerosol in varying proportions as soluble inorganic iodine, soluble organic iodine and insoluble, or unextractable, iodine. The different characteristics of these fractions are likely to have significant impacts on the cycling and reactivity of iodine in the atmosphere.

Quantitative determination of the platinum-group elements and gold using NiS fire assay with laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS )

Abstract Traditional methods for separating the platinum-group elements (ruthenium, rhodium, palladium, osmium, iridium, platinum; PGEs) and gold (Au) from ores and rocks have been adapted for use with laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). Samples were prepared using NiS fire-assay techniques resulting in the production of a collector button weighing only ∼ 1 g. The button was ground to produce a flat surface and directly ablated using a Nd:YAG laser operating at fundamental wavelength. Quantitative data were obtained by external calibration against both natural geological reference materials (SARM-7, MINTEK 2/77 and CHR-Pt+) and synthetic Nis standard buttons produced by doping high-purity quartz sand with multi-element stock solutions. Analysis times are rapid, 30 s per analysis, and the sampling protocols developed offer the possibility of full automation. Precision of the measurements varied according to concentration and the element concerned, but were typically 10–15% relative standard deviation or better. Accuracy of the data was assessed by comparison of measured and reference values. Accuracy was partly dependent on element. Data for Ru, Rh and Pd in 2/77 and Ru in CHR-Pt+ were in excellent agreement with reference values, while recoveries for Rh in CHR-Pt+ were a little high. Data for Os and Au could only be evaluated in SARM-7 where agreement with reference values was good. Platinum consistently showed poor recovery with values which were typically 30% low. Experimentally determined detection limits were similar for all elements, from 10 to 90 ng g−1 The method provides for the rapid, simultaneous and sensitive determination of the PGEs and Au in rocks and ores.

Elimination of reagent blank problems in the fire-assay pre-concentration of the platinum group elements and gold with a nickel sulphide bead of less than one gram mass

Fire assay is a classical method used for the separation of platinum group elements and gold (PGE + Au) by pre-concentration with a collector. In the nickel sulphide fire assay, nickel and sulphur are used for the collection of PGE + Au. We have successfully reduced the mass of the collectors used without affecting element recovery. The PGE + Au are recovered from 25 g of SARM-7 reference material with only 0.5 g of nickel, compared with the 10 g proposed by other workers. The inherent blank problem due to impurities in the reagents is eliminated when the mass of nickel is reduced by the factor of 20 proposed.

Geochemistry of the granitic rocks and their minerals from Serra da Estrela, Central Portugal☆

Abstract Several types of Hercynian peraluminous granitic rocks ranging from biotite-muscovite granodiorite to muscovite granite occur in the horst of Serra da Estrela. Variation diagrams of most major and trace elements of the rocks and biotites and Cr and V of muscovites show fractionation trends. However, Nb, Li, Rb, K Rb , Li Mg variation diagrams of the rocks and muscovites and also of Sn, Cs, Cs K of the muscovites indicate that the muscovite granite probably originated by another mechanism. Least squares analysis of major elements and modelling of trace elements indicate that the coarse grained porphyritic biotite-muscovite granite, granite porphyry and fine to medium grained muscovite-biotite granite were derived from the granodiorite magma by fractional crystallization of plagioclase, quartz and biotite. Emplacement of granodiorite magma took place at 3.5–3 Kb and 720°C: granites and granite porphyry probably originated about 690°C, but were completely crystallized about 520°C. ƒO2 was about 10−17 for the granodiorite and ƒ HCl ƒ HF ) was higher, whereas log ( ƒ h2o ƒ hcl ) was lower in the granodiorite than in the other granitic rocks of the fractionated series. The coarse-grained porphyritic biotite-muscovite granite was hydrothermally altered between 400–350°C and 260–230°C at about 1.5–1 Kb. The hydrothermal fluids were probably mainly meteoric in origin, but some fluids released during the late stage of granite solidification might also have been involved.

Determination of trace elements in food contact polymers by semi-quantitative inductively coupled plasma mass spectrometry. Performance evaluation using alternative multi-element techniques and in-house polymer reference materials

The determination of trace elements in a wide range of polymers intended for food contact use was carried out by inductively coupled plasma mass spectrometry (ICP-MS). Microwave digestion in concentrated nitric and sulfuric acids enabled rapid wet oxidation of all the polymers, to give samples suitable for introduction into the plasma. Semi-quantitative multi-element screening of the polymer digests could then be carried out using a single indium internal standard. Limits of detection for the polymers were generally in the order of 1 mg kg–1. Owing to the paucity of suitable standard reference polymer materials required for validation of the procedures used, a series of in-house reference materials was prepared by incorporating a cocktail of metal stearates into a range of polymer materials via the melt. Levels of elements in these reference materials were established by two reference methods: direct neutron activation analysis (NAA) and a quantitative ICP-MS method. Results for the two reference methods were encouragingly close to nominal added values and replicate analyses indicated that homogeneity was good. Further analysis of the materials using laser ablation ICP-MS confirmed that the distribution of elements within the polymer matrix was satisfactory. In addition, NAA was carried out on the great majority of the polymer samples as a further aid to validation of the semi-quantitative multi-element ICP-MS method.

The development of a sequential method for the determination of actinides and 90Sr in power station effluent using extraction chromatography

Determination of the actinides and 90Sr in power station effluent requires their radiochemical isolation prior, to measurement. Historically, techniques such as precipitation, ion exchange and solvent extraction have been used but these methods can be complex, time consuming and produce large amounts of chemical waste. A more environmental friendly sequential scheme for their determination in power station effluent using extraction chromatography has been developed. This is a simplified method which minimises chemical waste and makes use of commercially available pre-packed chromatography columns. An Eichrom TRU.Spec column was used for the separation of isotopes of plutonium from americium and curium followed in sequence by an Eichrom Sr.Spec column for the separation of 90Sr. The isolated actinides were prepared for alpha spectrometry analysis by electrodeposition and 90Sr was analysed by liquid-scintillation counting. The tracers 242Pu, 243Am and 85Sr were used to measure chemical yields. Method evaluation was carried out on water samples spiked with certified radionuclide standards to determine precision, accuracy, detection limits and chemical recoveries. Finally, testing and evaluation of the method was carried out on power station effluent.

Simultaneous determination of the noble metals in geological material by radiochemical neutron-activation analysis

A simple procedure is described for determining the noble metals in geological samples rich in chromium and copper. Powdered rock samples (0.1–0.3 g) are irradiated in an epithermal neutron flux, under a cadmium filter, to reduce interference from 51Cr and 64Cu. After digestion with a peroxide fusion, the noble metals are separated on Srafion NMRR ion-exchange resin. Activity from chromium(VI), retained on the resin, is eliminated by reduction to chromium(III) with iron(II) sulphate before separation. The gamma-ray activity is measured with a lithium-drifted germanium detector for palladium (109Pd), platinum (199Au), iridium (194Ir) and gold (198Au). The separation yield (iridium 40%, palladium 80%, gold 90%) is determined for each sample by irradiating the resin to activate a stable noble metal carrier. Multi-element noble metal standards (0.1–8 µg) are prepared from dilute solutions (100 µl) evaporated on resin (1 ml). The practical detection limits are 2.5 ng of palladium and platinum, 0.1 ng of iridium and 0.01 ng of gold. The reliability of the procedure was confirmed by analysing sulphide standards (PTM, PTC) and standard rocks (PCC-1, DTS-1). The method has been applied to the analysis of chrome-spinels.

Influence of soil pH on the fractionation of Cr, Cu and Zn in solid phases from a landfill site

The spatial variability of soil pH for engineered Weathered Oxford Clay is described using 35 samples collected from the base of a new cell in an existing landfill. Soil pH variability influences the reactivity of Cr, Cu and Zn in the site. The reactivity of these metals as natural components was determined using a sequential extraction method. The total concentration of Cr, Cu and Zn and the mineralogical composition were also determined. The results showed that due to the presence of a layer rich in pyrite in the base, a natural acidification may occur which can produce a soil pH as low as 2.7. The spatial variability of soil pH in this area has been described with an anisotropical variogram model and the estimation of its values at unsampled locations was carried out using the ordinary kriging algorithm. From the spatial modelling of the soil pH, it was found that the metals in the soil solid phases follow a similar distribution.

Instrumental neutron activation analysis of a nickel sulfide fire assay button to determine the platinum group elements and gold

Platinum group elements and gold were determined in reference materials SARM 7 and MA 1b using fire assay with 0.5 g of nickel prior to neutron activation analysis. The method is simple and rapid, avoiding the dissolution step where losses occur, particularly of gold. The problem of standardizing the button mass was overcome by using a spiking technique. The method is best suited to samples with little or no copper, when the detection limits can be as low as 0.002, 0.025, 0.018, 0.0002, 0.002, 0.020 and 0.2 mg kg–1 for Rh, Pd, Pt, Ir, Au, Os and Ru, respectively.

The relationship of dissolved Pb to some dissolved trace metals (Al, Cr, Mn, and Zn) and to dissolved nitrate and phosphate in a freshwater aquatic system in Mauritius

The relationship of some dissolved trace metals (Al, Cr, Mn, Zn, and Pb) with one another and to dissolved phosphate and nitrate in a freshwater aquatic system at Flic en Flac and Grand River North West (GRNW) in Mauritius (1850 km2, 20 degrees S and 57 degrees E, Western Indian ocean) is reported following trace metal determination using inductively coupled plasma mass spectrometry (ICP-MS). Dissolved Al (<200 ng ml(-1)), Cr (<50 ng ml(-1)), Mn (<50 ng ml(-1)), Zn (< 100 ng ml(-1)), and Pb (<50 ng ml(-1)) upstream, downstream GRNW and in the marshes and rivulet at Flic en Flac were found to be below the recommended EEC maximum admissible concentrations and within the ambient drinking water quality standards in Mauritius. Dissolved Pb was significantly positively correlated to both dissolved Cr and Zn suggesting that the cycling for dissolved Pb is linked to the cycling of both dissolved Cr and Zn along GRNW. The common influential cycling of Pb and Zn was further reinforced as both dissolved Pb and Zn were significantly positively correlated to dissolved phosphate, which suggested a biological role in the cycling of Zn and Pb. The role of biological activity or adsorption to biological systems in Pb cycling along GRNW is further suggested as dissolved Pb was significantly correlated to dissolved nitrate. The apparent absence of the dissolved Al, Cr, and Mn with dissolved nitrate and phosphate could be attributed to factors such as the lower sensitivity of the GRNW to metal uptake during biological activity during the time frame considered. The cycling of dissolved Al and Mn was also not linked to the cycling of Cr, Zn, and Pb as no significant correlation was found along GRNW.