Michael Krachler

A peat bog record of natural, pre-anthropogenic enrichments of trace elements in atmospheric aerosols since 12 370 14C yr BP, and their variation with Holocene climate change

Abstract A peat bog in the Jura Mountains, Switzerland, provides a continuous record of peat accumulation since 12 370 14 C yr BP. Periods of enhanced soil dust deposition (10 590 14 C yr BP, 8230 14 C yr BP, and after 5320 14 C yr BP) are characterized by strongly elevated Ti/Sc and Zr/Sc ratios which imply an increase in the abundance (both relative and absolute) of heavy minerals such as ilmenite and zircon. With respect to trace elements such as Cu, Zn, As, Cd, Sb and Au, the M/Sc ratios are at their lowest, and often approach crustal values, during periods of enhanced soil dust deposition. The lowest rates of atmospheric deposition of soil dust date from 8030 to 5320 14 C yr BP, corresponding to the Holocene climate optimum, but here many trace elements exhibit their greatest natural enrichments: the average enrichment factor (calculated using Sc as the reference element, and normalizing to crustal abundance) was Zn 4.1±1.4, Sb 4.8±1.4, Cu 8.8±3.3, As 14.9±3.2, Au 53.9±25.1, and Cd 357.4±53.8. These enrichments cannot be explained by chemical diagenesis within the deeper sections of the peat profile during or subsequent to peat formation, but rather reflect the chemical composition of airborne material supplied to the surface layers of the bog at the time of deposition. The enrichments of trace metals in ancient peats, relative to crustal abundance, most likely reflects the natural enrichment of these elements in the fine fraction of soils during rock weathering. Periods of enhanced soil dust deposition such as the Younger Dryas cold climate phase (10 590 14 C yr BP) are characterized by reduced vegetation cover, greater exposed soil surface, and higher wind strengths; these conditions promote the transport of locally derived soil materials of greater particle size, lower concentration of trace metals, and M/Sc ratios approaching crustal values. During the Holocene climate optimum, vegetation cover was extensive, and with lower wind strengths and a reduction in erodible soil materials, long range transport of soil dust became relatively more important to the soil dust inventory of the bog; soil dust particles in this size class are characterized by strong enrichments of a wide range of trace elements. At the end of the Holocene optimum, dust fluxes increased once again, due mainly to soil erosion resulting from the combined effects of human activities (tillage) and the climatic deterioration at the beginning of the Neoglaciation Period; this promoted the supply of local, more coarse soil particles with M/Sc ratios approaching those of crustal rocks. While biological cycling and volcanic emissions probably also contributed to the atmospheric supply of many of these elements in the pre-anthropogenic past, these contributions appear to be less important than the chemical weathering, physical fractionation, and atmospheric transport of soil dust particles.

Characterization of the Running-in Period in Total Hip Resurfacing Arthroplasty: An in Vivo and in Vitro Metal Ion Analysis

BACKGROUND Metal-on-metal total hip resurfacing arthroplasty is increasingly being performed in young and active patients. Preclinical in vitro testing of implants is usually performed with use of hip simulators, and the serum metal ion concentration is determined for the purpose of monitoring the patients. The goal of this study was to characterize the early running-in period in vivo and in vitro by characterizing metal ion levels. METHODS A well-functioning total hip resurfacing prosthesis was implanted in fifteen consecutive patients, and the serum metal ion concentrations in these patients were then determined preoperatively and at intervals during the first postoperative year (at one, six, twelve, twenty-four, and fifty-two weeks). The number of walking cycles was measured with use of a computerized accelerometer in order to compare walking cycles to hip simulator cycles. In vitro, five similar components were investigated for 3 million cycles with use of a hip simulator. Serum samples were obtained at different time points, and wear was measured by quantifying wear particles and ions in the samples. All patient and simulation serum samples were analyzed with use of inductively coupled plasma-mass spectrometry. One simulator implant was investigated with use of scanning electron microscopy. RESULTS The serum chromium and cobalt levels of the patients continuously increased during the first six months and showed an insignificant decrease thereafter. The molybdenum concentration was unchanged compared with preoperative values. In contrast, the simulator measurements showed a different wear pattern with a high-wear running-in period and a low-wear steady-state phase. The running-in period was delayed by 300,000 cycles and lasted up to 1 million cycles. Scanning electron microscopic analysis showed a carbon-rich protein film predominantly in the early phases of simulation. Scratches were detected originating from pits filled with aluminum oxide and silicon oxide and from pulled-out carbides that were causing third-body wear. CONCLUSIONS The simulator study allowed an exact characterization of the running-in period and showed a delayed onset of running-in wear. In contrast, the clinical data showed a slow increase in measured ion concentrations. These different wear patterns are probably due to the effects of distribution, accumulation, and excretion of particles and ions in vivo.

Trace and ultratrace metals in bottled waters: Survey of sources worldwide and comparison with refillable metal bottles

Bottled waters from diverse natural and industrial sources are becoming increasingly popular worldwide. Several potentially harmful trace metals (Ag, Be, Li, Ge, Sb, Sc, Te, Th, U) are not monitored regularly in such waters. As a consequence, there is extremely limited data on the abundance and potential health impacts of many potentially toxic trace elements. Containers used for the storage of bottled waters might also increase trace metal levels above threshold limits established for human consumption by the EPA or WHO. Applying strict clean room techniques and sector field ICP-MS, 23 elements were determined in 132 brands of bottled water from 28 countries. In addition, leaching experiments with high purity water and various popular metal bottles investigated the release of trace metals from these containers. The threshold limits for elements such as Al, Be, Mn and U in drinking water were clearly exceeded in some waters. Several bottled waters had Li concentrations in the low mg/L range, a level which is comparable to blood plasma levels of patients treated against manic depression with Li-containing drugs. The rate of release of trace metals from metal bottles assessed after 13 days was generally low, with one exception: Substantial amounts of both Sb and Tl were released from a commercially available pewter pocket flask, exceeding international guidelines 5- and 11-fold, respectively. Trace metal levels of most bottled waters are below guideline levels currently considered harmful for human health. The few exceptions that exist, however, clearly reveal that health concerns are likely to manifest through prolonged use of such waters. The investigated coated aluminium and stainless steel bottles are harmless with respect to leaching of trace metals into drinking water. Pocket flasks, in turn, should be selected with great care to avoid contamination of beverages with harmful amounts of potentially toxic trace metals such as Sb and Tl.

Analytical procedures for the determination of selected trace elements in peat and plant samples by inductively coupled plasma mass spectrometry

A simple, robust and reliable analytical procedure for the determination of 15 elements, namely Ca, V, Cr, Mn, Co, Ni, Cu, Zn, Rb, Ag, Cd, Ba, Tl, Th and U in peat and plant materials by inductively coupled plasma-quadrupole mass spectrometry (ICP-QMS) was developed. Powdered sample aliquots of approximately 220 mg were dissolved with various acid mixtures in a microwave heated high-pressure autoclave capable to digest 40 samples simultaneously. The selection of appropriate amounts of digestion acids (nitric acid, hydrofluoric acid or tetrafluoroboric acid) was crucial to obtain accurate results. The optimized acid mixture for digestion of plant and peat samples consisted of 3 ml HNO3 and 0.1 ml HBF4. An ultrasonic nebulizer with an additional membrane desolvation unit was found beneficial for the determination of Co, Ni, Ag, Tl, Th and U, allowing to aspirate a dry sample aerosol into the ICP-QMS. A pneumatic cross flow nebulizer served as sample introduction device for the other elements. Internal standardization was achieved with 103Rh for all elements, except for Th whose ICP-QMS signals were corrected by 103Rh and 185Re. Quality control was ascertained by analysis of the certified plant reference material GBW 07602 Bush Branches and Leaves. In almost all cases HNO3 alone could not fully liberate the analytes of interest from the peat or plant matrix, probably because of the silicates present. After adding small amounts (0.05–0.1 ml) of either HF or HBF4 to the digestion mixture, concentrations quantified by ICP-QMS generally increased significantly, in the case of Rb up to 80%. Further increasing the volumes of HF or HBF4 in turn, resulted in a loss of recoveries of almost all elements, some of which amounted to approximately 60%. The successful analytical procedures were applied to the determination of two bulk peat materials. In general, good agreement between the found concentrations and results from an inter-laboratory trial or from instrumental neutron activation data were obtained, underpinning the suitability of the developed analytical approach.

Metal release and corrosion effects of modular neck total hip arthroplasty

Modular neck implants are an attractive treatment tool in total hip replacement. Concerns remain about the mechanical stability and metal ion release caused by the modular connection. Five different implant designs were investigated in an experimental set-up. In vivo conditions were simulated and the long-term titanium release was measured. Finally, the modular connections were inspected for corrosion processes and signs of fretting. No mechanical failure or excessive corrosion could be identified for the implants tested. The titanium releases measured were extremely low compared to in vivo and in vitro studies and were not in a critical range.RésuméDans les prothèses totales de hanche l’utilisation d’implants avec col modulaire est d’une utilisation fréquente et pratique. Néanmoins, cette utilisation laisse persister des doutes sur la stabilité mécanique et sur le relargage des ions métalliques. 5 différents implants ont été étudiés en reproduisant les conditions in vivo, en mesurant le relargage de titane et en évaluant la corrosion et les lésions du col. Ce travail n’a pas permis de mettre en évidence d’échec secondaire à une corrosion excessive, et les taux de titane sont restés extrêmement bas dans les limites de l’acceptable.

Influence of digestion procedures on the determination of rare earth elements in peat and plant samples by USN-ICP-MS

Analytical procedures for the determination of rare earth elements (REE) in 250 mg aliquots of difficult-to-digest peat and plant matrices by ICP-MS were developed. Three different pressurised digestion approaches were tested for this purpose, namely (i) closed vessel acid digestion on a hot-plate at 180 °C, (ii) digestion in a microwave high pressure autoclave at a temperature of 240 °C and (iii) high pressure ashing (HPA) at a temperature of 320 °C. Acid mixtures for digestion contained concentrated nitric acid (3–5 ml) alone or additions of hydrofluoric acid (HF) or tetrafluoroboric acid (HBF4) at volumes of 0.05–1.0 ml. The selection of appropriate volumes of HF or HBF4 was identified as a critical step in obtaining accurate results. For several reasons, HBF4 is preferred in comparison with the normally used addition of HF for the destruction of siliceous matter in the samples investigated. The optimum acid mixture consisted of 3 ml of HNO3 and 0.1 ml of HBF4. High sample throughput (40 samples simultaneously in about 2 h) favours the microwave autoclave over the other two digestion systems. An ultrasonic nebuliser (USN) with membrane desolvation used for sample introduction reduced the spectral interferences originating from oxide formation of lighter REE and Ba to a negligible extent. Internal standardisation with Rh and Re proved to be essential for obtaining correct results. In this way, all REE could be reliably quantified by USN-ICP-MS without applying any mathematical correction equations. The accuracy of the optimised procedures was assessed by the determination of REE in digests of the certified reference material GBW 07602 Bush Branches and Leaves and of the candidate reference material CRM 670 Aquatic Plant. The developed analytical procedures were applied to the determination of REE in two different peat matrices. Results for these peat samples obtained by USN-ICP-MS showed good agreement with INAA values. Strong fractionation of REE caused by the addition of HF or HBF4 in excess, known as lanthanide contraction, could be experimentally established, except for europium, which revealed a different behaviour.

Predominance of industrial Pb in recent snow (1994–2004) and ice (1842–1996) from Devon Island, Arctic Canada

Predominance of industrial Pb in recent snow (1994-2004) and ice (1842-1996) from Devon Island, Arctic Canada

Influence of sample pre-treatment on the determination of trace elements in urine by quadrupole and magnetic sector field inductively coupled plasma mass spectrometry

An investigation was carried out to explore further the analytical capabilities of quadrupole and magnetic sector field inductively coupled plasma mass spectrometry (ICP-MS) in conjunction with ultrasonic nebulization (UN) for the reliable determination in human urine of nine potentially toxic and/or environmentally relevant trace elements, namely Cd, Co, Cr, Ni, Pb, Rb, Sb, Se and V. For the quantification of Cr, Ni and V magnetic sector field ICP-MS was used in the medium resolution mode (m/Δm=3000) to separate the signal of the analyte from severe polyatomic interferences caused by high concentrations of bulk elements (C, Ca and Cl). The detection power afforded by quadrupole ICP-MS, on the other hand, was adequate for the reliable determination of Cd, Co, Pb, Rb, Sb and Se. Three different sample pre-treatment steps, namely dilution of urine with high-purity water, UV irradiation and microwave digestion with concentrated HNO3 and H2O2, were investigated in detail to clarify two key issues, i.e., first, the performance, accuracy and reproducibility of the two ICP-MS systems under different matrix loads of the plasma and, second, the actual concentrations of trace elements in the urine sediment.

Optimising accuracy and precision of lead isotope measurement (206Pb, 207Pb, 208Pb) in acid digests of peat with ICP-SMS using individual mass discrimination correction

Using ICP-SMS, a robust analytical protocol for accurate and precise determination of the isotopic Pb composition (206Pb, 207Pb, 208Pb) of acid digests of peat samples was developed. External precision better than 0.05% and 0.1% for Pb concentrations in the range of 1 µg l−1 and 0.1 µg l−1, respectively, were achieved for both 207Pb/206Pb and 208Pb/206Pb ratios. This precision has never before been achieved with ICP-SMS in a complex matrix containing such low concentrations of total Pb. Procedural Pb blank concentrations amounted to 0.003 µg l−1 and had no influence on the accuracy of the Pb isotope ratios. Corrections for mass discrimination were accomplished using the certified isotopic reference material SRM 981. However, mass discrimination was found to be non-systematic, and varied among the masses both with respect to magnitude and direction. To accommodate this phenomenon, an individual mass discrimination correction was applied to each ratio resulting in improved accuracy. Using this approach, the mass discrimination for both Pb isotope ratios was <0.2%, compared to values on the order of ±0.35% if only a single Pb isotope ratio was used. The accuracy and precision of the ICP-SMS protocol was further evaluated using thermal ionisation mass spectrometry (TIMS) of selected samples and an in-house peat reference material. In general, the Pb isotope ratios determined using ICP-SMS deviated from the TIMS values by less than <0.1%. Given the throughput of the ICP-SMS compared to the TIMS (which requires chemical separation of Pb), the approach described offers great promise for environmental studies to fingerprint the predominant sources of anthropogenic Pb. Two applications are presented here: a bog profile from the Black Forest (SW Germany) consisting of eight thousand years of peat accumulation, and a depth profile through a snowpack collected from the same site during the winter of 2003.

Novel calibration procedure for improving trace element determinations in ice and water samples using ICP-SMS

Matrix-induced loss of accuracy was observed during the determination of 19 trace elements (Ag, Al, Ba, Bi, Cd, Co, Cr, Cu, Fe, Mn, Pb, Rb, Sb, Sc, Sr, Tl, U, V, Zn) in ice and water samples at fg g−1 to µg g−1 concentrations using ICP-sector field mass spectrometry (ICP-SMS) equipped with a guard electrode. The accuracy of the results was considerably improved by utilising the Ar dimer at m/z 80 measured in the medium resolution mode (m/Δm 4000) as internal standard. This innovative correction was carefully evaluated using the certified water reference material SLRS-4. The correction approach applied here during the determination of trace elements in ice samples by ICP-SMS adequately compensates for potential matrix effects in individual samples as well as for long-term drifts in sensitivity. Thus, the ArAr correction is as good as conventional internal standards such as In or Rh, respectively, but does not require addition of an “internal standard element”, which risks contamination of the clean ice samples.