Stanislav Strekopytov | Natural History Museum, London (original) (raw)

Papers by Stanislav Strekopytov

Sixty five urine samples obtained during one or two non-consecutive days from 10 healthy individu... more Sixty five urine samples obtained during one or two non-consecutive days from 10 healthy individuals were analysed for major (Na, Mg, K, Ca) and trace (Co, Cu, Zn, As, Rb, Sr, Mo and Pb) element concentrations. Following microwave digestion, the analyses were carried out using ICP-QMS (inductively coupled plasma quadrupole mass spectrometry) incorporating a collision/reaction cell. Repeat analyses of quality control samples show that the procedure produces unbiased results and is well suited for routine urinalysis of the investigated elements. Concentrations were normalised using specific gravity (SG) and the resultant decrease in variability supports previous conclusions that SG-normalisation appropriately corrects for differences in urine dilution. The elemental concentrations of the individual urine samples show large differences in dispersion. Most variable are As, Co and Zn, with CVs (coefficients of variation) of >75%. The major elements as well as Rb, Sr and Mo display intermediate variability, whilst Cu and Pb have the least elemental dispersion with CV values of about 30%. A detailed assessment shows that the overall elemental variability is governed both by differences between individuals and variations for a single individual over time. Spot urine samples exhibit elemental concentrations that, on average, resemble the daily mean values to within about 30% for all elements except K and Rb. Diet-related changes in urinary element concentration are most prominent for Mg, K, Co, Rb and Pb. The concentrations of Co, As and Rb appear to vary systematically with gender but this may primarily reflect co-variance with specific diets.

Jbilet Winselwan is one of the largest CM carbonaceous chondrites available for study. Its light,... more Jbilet Winselwan is one of the largest CM carbonaceous chondrites available for study. Its light, major, and trace elemental compositions are within the range of other CM chondrites. Chondrules are surrounded by dusty rims and set within a matrix of phyllosilicates, oxides, and sulfides. Calcium-and aluminum-rich inclusions (CAIs) are present at ≤1 vol% and at least one contains melilite. Jbilet Winselwan is a breccia containing diverse lithologies that experienced varying degrees of aqueous alteration. In most lithologies, the chondrules and CAIs are partially altered and the metal abundance is low (<1 vol%), consistent with petrologic subtypes 2.7-2.4 on the Rubin et al. (2007) scale. However, chondrules and CAIs in some lithologies are completely altered suggesting more extensive hydration to petrologic subtypes ≤2.3. Following hydration, some lithologies suffered thermal metamorphism at 400-500 °C. Bulk X-ray diffraction shows that Jbilet Winselwan consists of a highly disordered and/or very fine-grained phase (73 vol%), which we infer was originally phyllosilicates prior to dehydration during a thermal metamorphic event(s). Some aliquots of Jbilet Winselwan also show significant depletions in volatile elements such as He and Cd. The heating was probably short-lived and caused by impacts. Jbilet Winselwan samples a mixture of hydrated and dehydrated materials from a primitive water-rich asteroid. It may therefore be a good analog for the types of materials that will be encountered by the Hayabusa-2 and OSIRIS-REx asteroid sample-return missions.

The seabed site of a probable Bronze Age shipwreck off the coast of Salcombe in southwest England... more The seabed site of a probable Bronze Age shipwreck off the coast of Salcombe in southwest England was explored between 1977 and 1982 and from 2004 onwards. Nearly 400 objects including copper and tin ingots, bronze artefacts/fragments and gold ornaments were found, typologically dating either to c. 1300–1150 BC or 1000–800 BC. The 280 copper and 40 tin plano-convex ingots and ingot fragments represent the largest discovery , measured by total weight as well as by quantity, of plano-convex or bun ingots in northwest Europe. The Salcombe copper ingots provided a wonderful opportunity for the technical study of copper ingots in a probable shipwreck context, as opposed to terrestrial contexts of deliberate deposition. The chemical composition of 25 plano-convex copper ingots was determined using inductively coupled plasma mass spectrometry (ICP-MS) and inductively coupled plasma atomic emission spectroscopy (ICP-AES). Two artefacts from the site were also analysed for comparison with the ingots. Following the compositional analysis, a microstructural study was carried out on ten Salcombe copper ingots selected to cover those with different sizes, shapes and variable impurity levels using metallography and scanning electron microscopy coupled with energy dispersive X-ray spectrometry (SEM-EDS). All the analysed copper ingots are of unalloyed copper with low levels of impurities. Sulphide inclusions are present in all samples and bulk sulphur contents are of 0.32–0.79% in the ingots but lower in the artefacts. The Salcombe ingots were found to have a quite similar impurity pattern to the Hertford Heath (England) ingots (except for iron content). They are distinctly different from the Uluburun ingots, and, to a lesser degree, from Sardinian ingots. The results are inconclusive as to how the Salcombe ingots were made. On the one hand, the very low concentration of iron and the absence of cuprite inclusions suggest that the ingots were primary smelting products of the primitive smelting process rather than produced from re-melting or refining of primary smelting lumps. On the other hand, the dense metal with very low porosity suggests the product of refining and re-casting operations under reducing conditions. However, the small ingots are not likely to have resulted from breaking of large ingots. The chemical compositions of the Salcombe ingots point to British or Western European sources although the connection with other regions cannot be excluded for some of the ingots. Further studies including lead isotope analysis are needed to address the question of provenance of the copper ingots, which would contribute to the re-emerging debates surrounding the European Bronze Age metal trade.

Life science collections and their curated metadata are now seen as potential archives of environ... more Life science collections and their curated metadata are now seen as potential archives of environmental levels of trace elements. Bird feathers are especially promising material, but surface contamination might present a significant issue. The suitability of preserved specimens for environmental studies may be further limited by historical application of inorganic pesticides in the collections. Arsenic (As) and mercury (Hg) are the most significant inorganic contaminants in natural history collections since they were widely applied as pesticides from the late 18th century until the 1980s. Potential presence of As-and Hg-containing pesticide residues has also to be taken into account when members of the public are allowed to handle specimens. Even though the testing of taxi-dermy and anthropology museum collections for pesticide residues is becoming a common practice, it is generally done qualitatively rather than quantitatively. In this study, the concentrations of As and Hg were determined in feathers of eleven bird specimens considered for an interactive display and were found to range from 1.1 to 15,183 μg g −1 and from b 1 to 26,960 μg g −1 , respectively. The study shows how the quantitative information can be obtained and the history of the pesticide treatment reconstructed using a combination of analytical techniques including bulk analysis by inductively coupled plasma mass spectrometry (ICP-MS) following destructive or non-destructive sampling, and spatially resolved techniques such as laser ablation (LA)-ICP-MS and scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS). Inorganic As speciation by squarewave anodic stripping voltammetry (SWASV) and localisation of pesticide residues by X-ray micro-computed tomog-raphy (μCT) can provide additional information. It is found that As is not only present as micron-sized particulate residues, but becomes incorporated into the keratin matrix of the feathers. Mercury is probably nano-particulate and fully incorporated into keratin. The history of pesticide treatment might be complicated with mixtures of chemicals involving both As and Hg compounds and more than one way of pesticide application used on the same specimen.

In your element: Nature Chemistry

Anthropogenic emissions completely overwhelmed natural marine lead (Pb) sources during the past c... more Anthropogenic emissions completely overwhelmed natural marine lead (Pb) sources during the past century, predominantly due to leaded petrol usage. Here, based on Pb isotope measurements, we reassess the importance of natural and anthropogenic Pb sources to the tropical North Atlantic following the nearly complete global cessation of leaded petrol use. Significant proportions of up to 30–50% of natural Pb, derived from mineral dust, are observed in Atlantic surface waters, reflecting the success of the global effort to reduce anthropogenic Pb emissions. The observation of mineral dust derived Pb in surface waters is governed by the elevated atmospheric mineral dust concentration of the North African dust plume and the dominance of dry deposition for the atmospheric aerosol flux to surface waters. Given these specific regional conditions, emissions from anthropogenic activities will remain the dominant global marine Pb source, even in the absence of leaded petrol combustion.

Stable isotope compositions can potentially be used to trace atmospheric Cd inputs to the surface... more Stable isotope compositions can potentially be used to trace atmospheric Cd inputs to the surface ocean and anthropogenic Cd emissions to the atmosphere. Both of these applications may provide valuable insights into the effects of anthropogenic activities on the cycling of Cd in the environment. However, a lack of constraints for the Cd isotope compositions of atmospheric aerosols is currently hindering such studies. Here we present stable Cd isotope data for aerosols collected over the Tropical Atlantic Ocean. The samples feature variable proportions of mineral dust-derived and anthropogenic Cd, yet exhibit similar isotope compositions, thus negating the distinction of these Cd sources by using isotopic signatures in this region. Isotopic variability between these two atmospheric Cd sources may be identified in other areas, and thus warrants further investigation. Regardless, these data provide important initial constraints on the isotope composition of atmospheric Cd inputs to the ocean.

Mussels have the ability to control biomineral production and chemical composition, producing she... more Mussels have the ability to control biomineral production and chemical composition, producing shells with a range of functions. In addition to biological control, the environment also seems to influence the process of biomineralization; thus, shells can be used as archives of ambient water parameters during the calcium carbonate deposition. Past and present environmental conditions are recorded in the shells in the form of various proxies including Mg/Ca or Sr/Ca ratios. For such proxies to be accurate and robust, the influence of biological effects including the size of studied organism must be examined and eliminated or minimized, so that the environmental signal can be efficiently extracted. This study considers mineralogy and elemental composition of shells representing four size classes of Mytilus trossulus from the Baltic Sea. Obtained results suggest that mineralogy and chemical composition change throughout the shell development due to most likely a combination of environmental and biological factors. The content of aragonite increases with increasing shell size, while the bulk concentrations of Na, Cd, Cu, U, V, Zn and Pb were found to decrease with increasing height of the shells. Therefore, using mussels for environmental monitoring requires analysis of individuals in the same size range.

$Research paper thumbnail of Stable isotope ratio measurements of Cu and Zn in mineral dust (bulk and size fractions) from the Taklimakan Desert and the Sahel and in aerosols from the eastern tropical North Atlantic Ocean$

Accurate characterization of the stable isotope composition of Cu and Zn in major global mineral ... more Accurate characterization of the stable isotope composition of Cu and Zn in major global mineral dust sources and in aerosols is central to the application of these isotope systems to the studies of global geochemical processes and cycles. We test here for the first time Cu and Zn isotope ratios within a well-defined source-receptor setting on the continent–ocean interface and determine the isotope composition of (i) bulk surface soil dust samples from the Sahel region, (ii) individual size fractions of surface dust samples from the Taklimakan Desert, and (iii) aerosols collected in the equatorial eastern North Atlantic region. This is achieved reducing the blank contribution during the ion exchange step using small resin and acid volumes and using a second ion exchange passage to purify the Cu fraction. We find no significant correlation between size fractions and isotope ratios in the two samples analyzed from the Taklimakan Desert. Mass balance calculations suggest that isotope ratios of bulk samples are within the analytical precision of the o4 μm size fraction and can be used to characterize atmospheric long range transport of Cu and Zn in mineral dust from the Taklimakan Desert. The o 1 mm size fractions of two aerosol samples collected over the equatorial eastern North Atlantic region have Cu and Zn isotope ratios that are different to Sahel surface soil dust suggesting important non-crustal sources, in line with calculated enrichment factors, and possibly of anthropogenic origin. Using previously reported δ 66 Zn values for anthropogenic emission from Europe, preliminary calculations suggest that up to 55% of Zn arriving at the sampling points in the equatorial eastern North Atlantic region could be of anthropogenic origin.

Cellulose nitrate was widely used as a film base for photography, cinematography, and radiography... more Cellulose nitrate was widely used as a film base for photography, cinematography, and radiography in the first half of the twentieth century. Its stability is inherently poor and subject to environmental storage conditions. The risk of fire and the cross-infection effect on the cellulose acetate film stored at the same location necessitate that cellulose nitrate is identified within collections and stored separately. Not only medical archives, but also museums using radiography in their research may hold a sizeable amount of historical X-ray films. The Natural History Museum, London has been using film for X-radiography since before World War II. This suggests that some of the X-ray materials in its collections have a cellulose nitrate rather than ‘safety’ (cellulose acetate or polyester) film base. X-ray sheets rarely contain information related to their composition so science-based identification methods must be used. We propose the determination of nitrogen content in the film by organic elemental analysis (OEA) as a reliable method for the identification of films (X-ray, photographic, or cinematographic) with a cellulose nitrate base. Though it is a destructive method, the sample size required is small (<1 mg). This method does not require any sample preparation apart from weighing the samples and wrapping them in tin foil. OEA proved to be more accurate than the ‘float’ test in trichloroethylene and quicker and more straightforward to perform than infrared spectroscopy.

Introduction: Lunar meteorites, which were ejected from the surface as result of impact events, a... more Introduction: Lunar meteorites, which were ejected from the surface as result of impact events, are an important source of lunar material in addition to the Apol-lo and Luna samples. Here we report the bulk element composition, mineral chemistry analysis and petrogra-phy of the Miller Range (MIL) 090036 and 090070 lunar meteorites, found during the 2009-2010 ANSMET field season in Antactica [1]. MIL 090036 and 090070 are both feldspathic rego-lith breccias consisting of mineral fragments and lithic clasts in a glassy matrix [2,3,4,5]. Differences in mafic minerals and KREEPy components indicate that these meteorites are not paired [6]. Analytical methods: We were allocated two chips of MIL 090036,34 and MIL 090070,35 (200 mg each) and two polished thick sections mounted in epoxy resin blocks. 150 mg of each chip were powdered and bulk major, minor and trace element chemistries were determined using a inductively coupled plasma spectrometer: ICP-AES was used for major elements and IC...

Biomass is increasingly being used as an alternative energy source to fossil fuels. Of particular... more Biomass is increasingly being used as an alternative energy source to fossil fuels. Of particular concern is that during combustion of biomass rich in silica (SiO 2), such as sugarcane and many other grasses, the silica can convert into a crystalline form. Exposure to crystalline silica can potentially cause respiratory disease, such as silicosis. To improve understanding of the potential health risk, a robust and rapid method for quantifying the amount of silicon (Si) in plant material is required. Traditional methods do not usually account for Si in organic materials. This paper, therefore, proposes a new methodology based on a closed vessel microwave digestion using hydrofluoric acid (HF). To test the method, sugarcane leaves were digested and the solutions analysed by inductively coupled plasma atomic emission spectroscopy (ICP-AES), with an HF-resistant setup, and two external calibration standard sets in an HF-H 3 BO 3-matrix and HNO 3-matrix. The concentration of Si found in the reference materials was consistent with previously published values and Si loss during the sample preparation was minimal. The elemental recoveries from the reference materials were generally good (85–115% for Al, Ca, Cu, Fe, K, Mg, P, Si, Sr, Ti and 78–125% for K and S). The new methodology can be constructive in building a new database on Si and some other elements in biofuel plant varieties.

There are unexplained links between human exposure to aluminium and the incidence, progression an... more There are unexplained links between human exposure to aluminium and the incidence, progression and aetiology of Alzheimer's disease. The null hypothesis which underlies any link is that there would be no Alzheimer's disease in the effective absence of a body burden of aluminium. To test this the latter would have to be reduced to and retained at a level that was commensurate with an Alzheimer's disease-free population. In the absence of recent human interference in the biogeochemical cycle of aluminium the reaction of silicic acid with aluminium has acted as a geochemical control of the biological availability of aluminium. This same mechanism might now be applied to both the removal of aluminium from the body and the reduced entry of aluminium into the body while ensuring that essential metals, such as iron, are unaffected. Based upon the premise that urinary aluminium is the best non-invasive estimate of body burden of aluminium patients with Alzheimer's disease were asked to drink 1.5 L of a silicic acid-rich mineral water each day for five days and, by comparison of their urinary excretion of aluminium pre-and post this simple procedure, the influence upon their body burden of aluminium was determined. Drinking the mineral water increased significantly (P < 0.001) their urinary excretion of silicic acid (34.3 ± 15.2 to 55.7 ± 14.2 µmol/mmol creatinine) and concomitantly reduced significantly (P = 0.037) their urinary excretion of aluminium (86.0 ± 24.3 to 62.2 ± 23.2 nmol/mmol creatinine). The latter was achieved without any significant (P > 0.05) influence upon the urinary excretion of iron (20.7 ± 9.5 to 21.7 ± 13.8 nmol/mmol creatinine). The reduction in urinary aluminium supported the future longer-term use of silicic acid as non-invasive therapy for reducing the body burden of aluminium in Alzheimer's disease.

In your element: Nature Chemistry