Laser ablation microprobe as an injection device for analytical atomic spectrometry

Imperial Users onl

A feasibility study on the use of isotope dilution as a tool for quantifying uranium isotopic concentrations by quadrupole ICP-MS

The determination of uranium elemental concentrations and isotope ratios has been a major task for the BGS inductively coupled plasma mass spectrometry (ICP-MS) laboratory over the last five years. UK government departments and the nuclear industry have ongoing environmental monitoring programmes which require high quality data. The need for a greater understanding of chemical pathways, sinks and sources has been a driver for BGS to continue to improve analytical performance but with a minimal increase in costs. This study seeks to identify whether isotope dilution could provide a significant increase in analytical performance with minimal cost implications. This report reviews the fundamental concepts of isotope dilution and its advantages over related techniques such as internal standardisation. It considers the potential benefits of quadrupole ICPMS (ICP-QMS) over other techniques where high productivity is an issue, such as for environmental monitoring. The optimisation of the ICP-MS acquisition parameters including peak dwell times, detector dead-times, spike concentrations and operating conditions are examined. Isotope dilution (ID) relies heavily on the accurate calibration of the 233U spike and the process of reverse isotope dilution is used and discussed as part of this study. A series of experiments was conducted to ascertain the degree of chemical preparation required for accurate isotope dilution determination. These included comparing the effectiveness of using the 233U spike with internal standardisation by a proxy element, to overcome ICP-MS matrix effects and changes in sensitivity. Finally, the proposed methodology was tested using a range of natural rock reference materials with known uranium concentrations covering various common igneous and metasedimentary types. This project established that the use of 233U, a by-product of nuclear fuel processing, provided superior precision when used as an internal standard for measurements of other uranium isotope concentrations, compared to indium, rhenium or bismuth. The data suggest that the within sample precision is better when full ID quantification is performed, regardless of the matrix, than when using the spike as an internal standard. The IDMS technique could potentially eliminate the current column separation procedure, which would achieve significant savings in staff time and consumables. A small systematic bias has been observed in the data. It is thought that one of the most likely factors is the assumption made about the density of the 233U spike solution, which would affect the IDMS calculations but have no influence when 233U is used as an internal standard. It will not always be appropriate to use this method for the determination of uranium isotope concentrations and a decision tree needs to be devised to determine the appropriate method to be used for each potential application. The investigation has proved the value and potential of this methodology for isotope concentration analysis by quadrupole ICP-MS. Once a robust, fit for purpose methodology can be applied routinely, the possibility of the use of IDMS for other stable isotopes should be considered

Tracing sources and fate of zinc in a mining-impacted river catchment: insights from flow measurements, synoptic sampling, and zinc isotopes

This paper reports on the comprehensive monitoring of the Rookhope Burn catchment in the Weardale valley, northern Pennines (Uk), which has been subject to lead, zinc, and fluorspar mining for over two centuries. Zinc is the major contaminant in surface waters, exceeding the Environmental Quality standard value for salmonid fish. synoptic flow monitoring and water sampling have been carried out, including both inflow and instream sampling points along the Rookhope Burn, with the purpose of tracing both point and diffuse sources of Zn throughout the catchment. The Zn load profile suggests an important role for Zn-rich groundwater contributions to the stream bed and has also established the existence of Zn sinks. Evidence from hyporheic zone sampling suggests Zn reaction or surface complexation with Mn oxide surfaces forming on stream bed sediments as a potential mechanism responsible for the observed metal attenuation. Current work is focused on testing the potential of Zn isotopes to fingerprint sources and pathways of Zn in the aquatic system. Preliminary results show significant variation in the stream water Zn isotopic signature from the headwaters to the base of the catchment

An archaeometric study of Hellenistic glass vessels: evidence for multiple sources

In the present study, 53 glass fragments from core-formed vessels and 3 glass beads are investigated using SEM/EDX, EPMA and LA-ICP-MS. All samples were excavated in the Latin settlement of Satricum in central west Italy and apart from two, were found in the so-called fourth–third c. BC Hellenistic Votive deposit, also known as Votive Deposit III, discovered in front of the sanctuary of Mater Matuta on top of the acropolis. The analytical results indicate that the glass from Satricum is a typical soda-lime-silica type with natron used as a flux. Its chemical compositions display a relatively low compositional variation. Small differences in the concentrations of major and minor oxides (SiO2, Al2O3, CaO and Fe2O3) and in trace elements (Sr, Zr and Nd) between individual samples suggest the use of different types of raw materials, especially sand. In turn, this suggests that the glass derived from more than one glass making centre. The combined investigation of colourants (Co, Cu and Mn) reinforces and confirms the idea that glass from Satricum was made using different manufacturing traditions during the Hellenistic period

Statoliths of the whelk Buccinum undatum: a novel age determination tool

Sustainability within the fisheries of the commercially important European whelk Buccinum undatum has become a major concern because of over-exploitation and increased landings in many European coastal shelf seas due to the expansion of export markets to East Asian countries. Current management of B. undatum populations is difficult to achieve as several life history traits are problematic to accurately monitor. The current method of age determination for stock assessment has a low success rate and focuses on the use of putative annual rings on the surface of the organic operculum. Here, we validate an annual periodicity of growth ring formation in B. undatum statoliths that provides an alternative, reliable and accurate method for determining a whelk’s age. Laboratory-reared juvenile B. undatum of known provenance and age deposited a hatching ring at the time of emergence from their egg capsule and a clearly defined growth ring during February of their first and second years. Stable oxygen isotope profiles from the shells of 2 adult whelks confirmed annual growth ring deposition by demonstrating seasonal cycles of δ18O in the shell that matched the relative position and number of visible growth rings in the statolith. Validation of annually resolved statolith growth rings will, for the first time, provide fisheries scientists with a tool to determine the age structure of B. undatum populations and allow analytical stock assessments that will enable informed decisions for future management practices of whelk fisheries

Iodine status of soils, grain crops, and irrigation waters in Pakistan

A study was carried out across 86 locations of the country to investigate iodine supply potential of soils, grains and underground waters for onward design of an environmental intervention in Pakistan. Wheat crops were the principal crop in this study since it supplies 75 % of calorific energy in an average Pakistani diet. TMAH-extractable iodine in soils provided a geometric mean of 0.66 µg g−1, far lower than the worldwide mean of 3.0 µg g−1 for soil iodine. Bioavailable (water-extractable) iodine concentration had a geometric mean of 2.4 % (of TMAH-extractable iodine). Median iodine concentrations in tube well sourced waters were 7.3 µg L−1. Median wheat grain-iodine concentrations were 0.01 µg g−1. In most of the grain samples, TMAH-extractable iodine was below detection limit of 0.01 µg g−1. The highest wheat grain iodine was measured on a soil having highest TMAH-extractable iodine. An iodine intake of 25.4 µg a day has been estimated based on median wheat grain iodine measured and groundwater consumption compared to world health organisation (WHO) recommendations of iodine intake of 150 µg a day. This nominal intake of iodine is alarming since 60 % of Pakistani households do not consume iodised salt

Late Cretaceous and Cenozoic paleoceanography from north-east Atlantic ferromanganese crust microstratigraphy

Oceanic hydrogenetic ferromanganese (Fe-Mn) crusts precipitate directly from ambient seawater over millions of years. Their very slow growth rates and physio-chemical properties mean that they adsorb numerous elements from seawater. As such, they provide condensed records of seawater evolution through time that can be used for paleoceanographic reconstruction. Here, we present the results of a high-resolution, stratigraphic, textural and geochemical investigation of a core sample, obtained from a Fe-Mn crust pavement, located on the summit of Tropic Seamount in the tropical north-east Atlantic Ocean. A number of observations and interpretations are proposed, within the context of a well-constrained age model, spanning the last 75 ± 2 Myr. This core has textural stratigraphic coherence with Pacific Fe-Mn crusts formed since the Late Cretaceous, highlighting that global oceanic and climatic phenomena exert first-order controls on Fe-Mn crust development. All major hiatuses observed in the Fe-Mn crusts are contemporaneous with erosion events occurring throughout the Atlantic Ocean. High-resolution geochemical data indicate that there is variability in the composition of Fe-Mn crusts at the cm to μm scale. The dominant factors controlling this include major oceanographic events, mineral textures and micro-topography

Optimisation of a current generation ICP-QMS and benchmarking against MC-ICP-MS spectrometry for the determination of lead isotope ratios in environmental samples

© 2018 The Royal Society of Chemistry. Novel ANOVA methodology was used to benchmark ICP-QMS against MC-ICP-MS for Pb isotope ratios, demonstrating "fitness-for-purpose" in environmental source apportionment. The precision and accuracy of lead (Pb) isotope measurements obtained from quadrupole-based mass spectrometers (ICP-QMS) are considered to be limited by a number of factors originating in different components of the instruments. In this study, experimental and instrumental protocols were optimised for determining lead isotope ratios in urban soil digests. Experimental measures included individual dilution of all samples and isotopic standards (SRM-981, NIST) to a single Pb concentration intended to produce an intensity which was high enough to negate blanks and interferences but low enough to ensure the detector operated only in pulse counting mode. Instrumental protocols included batch dead time correction, optimisation of dwell time and the number of scans employed and correction of mass discrimination by sequential application of both internal ( 203 Tl/ 205 Tl ratio) and external (SRM-981, NIST) standards. This optimised methodology was benchmarked against multi-collector mass spectrometer (MC-ICP-MS) measurements of Pb isotope ratios using replicate digest solutions of the same soil; but after these had been subjected to Pb separation using an ion-exchange procedure. On the assumption that MC-ICP-MS measurements are more accurate, small additive and multiplicative differences were observed in only the 4 th decimal place. ANOVA was used to compare the precisions of the two techniques demonstrating equal precisions c. 0.08% for 207 Pb/ 206 Pb, suggesting a sample heterogeneity limitation. By contrast, for 207 Pb/ 204 Pb, the worst-case ratio, ICP-QMS had a 10-fold poorer precision, despite negligible interference from 204 Hg, implying an instrumental limitation. The study concludes that ICP-QMS can provide valuable source apportionment information for most Pb isotope ratios but further efforts should focus on improving assay of the 207 Pb/ 204 Pb ratio

Catchment-scale assessments of the effects of abandoned metal mines on groundwater quality and stream ecology

This paper presents an overview of a British Geological Survey catchment-scale research project designed to quantify catchment-derived metal loading on surface water quality. This work is focused on the Rookhope Burn, a tributary of the River Wear in the North Pennines, UK. The river has been identified in the Water Framework Directive (WFD) River Basin Management report as being at risk of failing to achieve Good Status due to mines and minewater pressures. Although geologically relatively simple, the catchment is hydrogeologically complex in that it comprises an area of entrenched karst, characterised by Lower Carboniferous Limestone exposed in the base of valleys overlain by Namurian strata, comprising interbedded shales, sandstones and limestones, which are capped by drained blanket peat. Metal loadings in this catchment result from lead and zinc mineralization and its historic exploitation and processing, which have resulted in both point source and diffuse impacts within the catchment. There have been three main phases of research: (i) collection of hydrological and water chemistry data to enable loading and mass balance calculations to be undertaken; (ii) development of a conceptual understanding of the hydrology and hydrogeology of the catchment, and (iii) application of the hydrological understanding to more recent baseline monitoring of ecological impacts. This work has identified previously unreported mine and groundwater contributions to the catchment, which may have significant implications for the design of remedial measures in the catchment