During the last few decades, variations in the 'natural' isotopic abundances of stable elements (termed 'fractionation') have received considerable interest from the scientific community. Though analytical methods and techniques for the measurement of isotopic abundances with adequate figures of merit have been available for light elements (e.g. B, C, N and O) for some time, and the wealth of data produced has secured maturity status for such applications, relatively modest progress in fractionation studies devoted to high-mass elements has been made until recently, mainly because of constraints of the available analytical techniques. The situation has changed drastically with the advent of multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS), with the number of reports about natural fractionation of Fe, Cu, Zn, Mo, Cd, Sn increasing exponentially during the recent years. In spite of the high Si abundance in nature and the importance of the element in many areas of the Earth sciences (focusing on e.g. weathering, the global Si cycle, paleoclimate studies, paleoceanography, and biological uptake), the available information on Si isotope fractionation remains rather limited due to the laborious and hazardous chemical purification procedures associated with the analyses. The focus of this thesis was the development of analytical methods for the precise and accurate measurements of Si isotope ratios, which is an absolute requirement for meaningful fractionation studies, in various matrices. This work involved detailed studies on sample preparation (including matrix separation) and refining the measurement protocol by using high resolution MC-ICP-MS. In the former stages, quantitative analyte recovery, thorough control of contamination levels and purification efficiency were the major targets, while severe spectral interferences and the need for adequate instrumental mass bias corrections challenged the latter. The performance of the method was tested in the first inter- laboratory performance assessment study of its kind with good results. As limited examples of applications, studies on Si isotope fractionation in aqueous, plant and humus samples were performed utilizing methods developed. The efficient analyte separation, high-resolution capability of the instrument, quantitative Si recovery and accurate mass bias correction using Mg as internal standard, allowed the determination of the Si isotopic composition of natural waters and biological samples with long-term reproducibility, expressed as twice the standard deviation (2σ), equal to or less than 0.10‰ for δ29Si and 0.25‰ for δ30Si. Furthermore, the presence of a challenging spectral interference on 29Si originating from 28SiH+ was revealed during this study, indicating that instrumental resolution in excess of 3500 is required for interference-free Si isotopic analyses. However, despite complete removal of N-, O-, and C-containing interferences appearing on the high-mass side of the Si isotopes, it was found that exact matching of both the acid matrix and the Si concentration are mandatory due to tailing from the abundant 14N16O+ interference on 30Si. This thesis also includes results from the first study of the Si isotopic homogeneity of major biomass components from a defined area in Northern Sweden covered by boreal forest. Since the potential impact of vegetation on the terrestrial biogeochemical cycle has attracted considerable interest, thorough characterization of the Si isotopic composition of the biomass potentially allows the utilization of this isotope system in the assessment of the relative contributions of biogenic and mineral silica in plants, soil solutions and natural waters (including fresh-, brackish- and marine waters). Isotopic analyses of the biological materials yielded a surprisingly homogenous silicon isotopic composition (relative to the NBS28 Si reference material), expressed as δ29Si (2σ), ranging from (- 0.14 ± 0.05)‰ to (0.13 ± 0.04)‰ Furthermore, elemental and isotopic analysis of local airborne particulate matter suggests that vegetation also accumulates silica via incorporation of exogenous Si containing primary and secondary minerals (in addition to root uptake of non-ionic silicic acid), a fact that has been neglected in previously published studies. This strongly indicates that the presence of potential surface contributions must be considered during in situ silicon uptake studies / <p>Godkänd; 2007; 20071011 (ysko)</p>

Physicochemical speciation of metals in natural waters is very important for understanding their distribution, mobility, bioavailability and toxicity. To be able to understand the behaviour of an aqueous element and the transformation between chemical and physical species, there is a need for reliable methods that enable measurements of specific fractions of metals. Many different techniques are used for metal speciation, of which many suffer from problems. Ultrafiltration has frequently been used to study speciation of metals in natural waters. A possible alternative or complement to ultrafiltration is the technique of diffusive gradients in thin films (DGT), a novel technique which provides an in situ measurement of labile metal species. DGT accumulates metals in a time- integrated way and produces a mean concentration over the chosen deployment period. DGT- labile metals may be regarded as a measure of the bioavailable amount, since the DGT simulates the diffusion process that occurs when a metal is diffusing into a cell membrane. This thesis is focused on the DGT technique for sampling and determination of labile species in the Baltic Sea. The aim of this study was to compare the trace metal speciation methods; DGT, 1 kDa ultrafiltration, 0.22µm membrane filtration and unfiltered water, to study the dynamics for the DGT labile fractions to find out which mechanisms that control the labile fraction. In 2003 and 2004, DGT and 1 kDa ultrafiltration were simultaneously applied at two sampling stations in the Baltic Sea with different salinity and trace metal concentrations. Baltic Sea concentrations of Mn, Zn and Cd measured by DGT during 2004 were similar to the concentrations measured in 1 kDa ultrafiltered samples, especially for Mn. Cu and Ni, showed noticeably higher concentrations in ultrafiltered water than DGT-labile concentrations. This indicates the existence of low molecular weight Cu and Ni species, small enough to pass through the 1 kDa, but can also be a sign of high degree of organic complexation which will lead to an underestimation in the DGT labile fraction. The dynamics of DGT-labile trace metals during 2004 show quite large variations during the season at 0.5 to 40 meters depth. From May to August, Cu, Cd and Mn drop about 35, 50% and 60% respectively. Ni decreased about 25% late April to late June but was slightly recovered at late season. The only elements that showed good correlation between DGT-labile species to dissolved phase (0.22µm filtrate) was Mn and Cd. DGT labile Mn is probably controlled by oxidizing bacteria during most of the sampling period, and DGT labile Co, Cd and to some extent Zn seem to follow this process. It should be noted that Mn is closely correlated to P, a relationship which need further investigations. Cu and Ni are controlled by other processes, where influence from primary production may be one. This is the first comparison of DGT and 1 kDa ultrafiltration regarding trace metals in brackish waters. Strong correlations between the methods imply that DGT can be a simple alternative to an ultrafiltration procedure. It is also the first study on trace metals in the Baltic Sea where measurements were performed at high temporal resolution during several months. / <p>Godkänd; 2006; 20061124 (ysko)</p>

<p> Models suggest that global warming will cause an intensification of the hydrologic cycle, but they are poor at predicting changes in the frequency of short, intense precipitation events at the regional to local scale. High-resolution stable isotope measurements across tree rings have shown potential for resolving precipitation at sub-annual resolution, but identification of single intense precipitation events across multiple tree rings has proven elusive. In this work, I report 218 high-resolution carbon isotope (&delta;¹³C) measurements made across eight growth rings of two Pinus trees cored in southern Louisiana. Tree rings were targeted for the presence and absence of extreme rainfall associated with land-falling tropical cyclones within 100 km of the study site. Comparison of the &delta;¹³C record to meteorological data yields a significant correlation (r = -0.576, p = 0.0004) with monthly precipitation and &delta;¹³C value measured across the rings. Significant, intra-ring declines of >1&permil; are associated with monthly precipitation > 200 mm that cannot be resolved by low-resolution sampling. Comparing the effects of sample resolution on &delta;¹³C patterns suggests that wide-ringed samples are preferred for identifying precipitation events at sub-seasonal resolution. Recent technical and methodological advancements allow for more rapid preparation and analysis of intra-ring &delta;¹³C data and provide opportunity for quantifying sub-seasonal environmental information within high-resolution tree-ring datasets. This work indicates the potential for quantifying changes in the magnitude and frequency of extreme precipitation events at individual sites from long-term intra-ring &delta;¹³C records.</p><p>

<p> The Lower Mississippi River Alluvial Aquifer (LMRAA) is a critical groundwater resource for Arkansas, Mississippi, and Louisiana. It is second only to the Ogallala aquifer in terms of the volume of groundwater pumped for irrigation. High concentrations of salinity, iron (Fe), and arsenic (As) affect several regions of the LMRAA. In this study, long-term geochemical changes in the LMRAA in Louisiana were evaluated to better understand the relationships among salts, Fe, and As. The geochemistry was investigated using historical data collected from the LDEQ and USGS. Data from the LDEQ were collected every three years from approximately 2001 to 2013. Major and some trace element data were available, including concentrations of sodium (Na), chlorine (Cl), magnesium (Mg), calcium (Ca), Fe, and As. These historical data were supplemented with recent (2016/2017) sampling and analysis of the isotopes of oxygen (&delta;¹⁸O) and hydrogen (&delta;²H). Geochemical results show that groundwater in the LMRAA in Louisiana can be characterized by two main groupings. The first group is generally characterized by a Na/Cl ratio close to one and/or higher salinity, while the second group is generally characterized by excess Na (relative to Cl) and tends to be more alkaline and rich in Fe. The highest salinity regions are spatially limited, and their extents appear to have remained stable over time. Areas of elevated salinity in the northeast part of the study area may be attributable to mixing of deeper salt-rich waters with the shallow groundwater system, while the salt-rich areas in the southern part of the study area are thought to be attributable to dissolution of salt domes. The waters potentially influenced by brines in the northeast are additionally characterized by higher Mg/Ca ratios. These waters are also enriched in &delta;¹⁸O relative to other areas of the LMRAA. There was no correlation between the areas of potential brine interaction and the concentrations of Fe or As. Instead, areas of high Fe concentration correlated spatially with areas of high alkalinity and the development of waters with excess Na (i.e., waters where Na is in substantial excess relative to the amount of chloride, and instead counterbalanced by HCO_3^-). Arsenic concentrations varied from below detection to 67.7&micro;g/L at one location sampled by the LDEQ in 2010. Six of the approximately 25 wells historically sampled by the LDEQ as part of the ASSET program consistently had concentrations of As >10 &micro;g/L. These locations generally correspond with the groundwater characterized by higher Fe, alkalinity, and Na-excess, but at the same time appear to be localized and often surrounded by wells with low concentrations of As. The concentrations of Fe and As were not correlated. This rather heterogeneous distribution of As contamination could point to anthropogenic influences or sources. The concentrations and spatial distributions of waters rich in salts, Fe, and As in the LMRAA appear to have remained relatively consistent for the last decade, even though demand for groundwater in the LMRAA of Louisiana has more than doubled over this time to 493 million gallons per day (in 2016). </p><p>

<p> Source rock kinetics have become increasingly important when defining kerogen maturity and building basin models. Recent studies have suggested that the activation energies (E_a) needed for these applications can be obtained using one-run open-system pyrolysis with a single heating rate and a fixed frequency factor (A). This method is thought to be faster and cheaper than using multiple heating rates with a varying frequency factor. In this study both methods were used to find the E_a of seven organic-rich samples from the Eagle Ford Shale. Activation energies for the multiple heating rate method were calculated in accordance to the Kissinger method, while E_a values for the single heating rate method were found using the One Run Fixed A (ORFA) kinetic software. The multiple heating rate method implemented heating rates of 5, 10, 20, and 50 &deg;C/min, while the single heating rate method used a standard heating rate of 25 &deg;C/min. Due to the use of a fixed A, the single heating rate method produced larger, more consistent values than the multiple heating rate method. However, these E_a values were not always consistent with previous known values. When the fixed A value used in the single heating rate method was replaced with the A values obtained from the multiple heating rate method, E_a became closer to those found using multiple heating rate method.</p><p>

<p> Several studies have suggested a link between the generation of petroleum and the formation of base metal deposits, primarily Pb, Cu, and Zn deposits, in sedimentary basins. The metals incorporated into basinal brines could be derived from a number of sources, including host rock units. In this study we evaluated hydrocarbon source rocks, specifically organic-rich shales, as a source of trace metals for basinal brines using batch leaching experiments and analyzing the USGS&rsquo; produced waters geochemical database. Batch leaching experiments were performed with powdered source rocks from the Eagle Ford, Marcellus, and Wolfcamp Shales. A subset of the samples was subjected to the destruction of organic matter through the loss-on-ignition method prior to leaching. All samples were subjected to batch leaching by combining approximately 1 g of rock with 10 mL of NaCl, acetate, or NaCl and acetate-electrolyte solution with molarities of 0.01, 0.1, 0.5, or 1. The experimental results showed that more trace (Pb, Zn, and Mo) metals were extracted from the Eagle Ford (EF 28) and Marcellus (Ma) source rocks post destruction of the organic matter prior to leaching using a NaCl and acetate-electrolyte solution. The leaching results also suggested that chloride complexes increased metal solubility in solution more than organic complexes (acetate) for trace metals (Zn and V) and some major elements (Mg). In the produced waters database, trace metal concentrations (Cu, Pb, and Zn) in samples from the Appalachian, Arkla, Gulf Coast, and Williston Basins exhibited a positive correlation with increasing chloride concentration. The produced waters database results hint that there are additional complexities associated with metal sources and loading such as pH and the presence of H₂S.</p><p>

As both the toxicity and the mobility of trace elements are related to chemical forms present, robust methods for element speciation analysis are of great interest. During the last 15 years, hundreds of scientific articles have been published on the development and applications of the diffusive gradients in thin films (DGT) passive sampling technique. The aim of this thesis was to explore new application areas as well as carry out further characterisation of DGT-adsorbents already on the market. The commercially available DGT containing ferrihydrite adsorbent, currently in use for the determination of phosphate and inorganic arsenic, was characterised with respect to anionic arsenate, molybdate, antimonate, vanadate and tungstate determination. Tests were performed in the laboratory as well as in the field. Diffusion coefficients were determined for the anions using two different methods with good agreement. Simultaneous measurements of arsenate were conducted as quality control to facilitate comparison of the performance with previous work. The ferrihydrite-backed DGT was concluded useful for application over the pH-range 4 to 10 for vanadate and tungstate, and 4 to <8 for molybdate and antimonate. At pH values ≥8, deteriorating adsorption was observed. Further investigations of the ferrihydrite-DGT device were done with respect to organic arsenic species. From previous research it is understood that the two most prevalent forms of organic arsenic in natural waters, monomethylarsinate (MMA) and dimethylarsonate (DMA), adsorb to ferrihydrite. It was concluded that MMA and under some conditions DMA are accumulated and might therefore be included in total arsenic measurements. A method for speciation of inorganic As, DMA and MMA was described. DGT sampling was applied at three stations, with different salinities, in the brackish Baltic Sea. Time series as well as vertical profiles were taken and complementary membrane- (<0.22 μm) and ultrafiltrations (<1 kDa) were conducted on discrete samples collected at 5 m depth. A combination of a restricted pore (RP) version of DGT and the normal open pore (OP) DGT, both loaded with Chelex cation exchanger, was used for speciation of copper and nickel. Due to minimal differences in results between the OP- and RP-DGTs it was suggested that the complexes were smaller than the pore size of the RP gel (~1 nm) resulting in both DGTs accumulating essentially the same fraction. Furthermore, there seemed to be a trend in copper speciation indicating a higher degree of strong complexation with increasing salinity. The low salinity stations are more impacted by fluvial inputs which will likely affect the nature and composition of the organic ligands present. Assuming that copper forms more stable complexes with ligands of marine rather than terrestrial origin would be sufficient to explain the observed trend. Additionally, uranium results from the same sampling tours were used to evaluate OP-DGT for in situ uranium measurements. Previous research has focused on laboratory studies for characterisation of a range of suitable uranium adsorbents, including Chelex. From the Baltic Sea study, a strong correlation between DGT-labile uranium and pH was revealed. The correlation could not be associated to organic complexation, since the ultrafiltration results implicated that uranium was truly dissolved. Instead it must be attributed to the formation of stable inorganic anionic uranyl-carbonate complexes, the stability of which increases with increasing numbers of carbonates and pH. Transplanted aquatic moss has commonly been used to monitor bioavailable trace metal contaminations in freshwater. Like the DGT technique the method has the advantage of generating time-weighted averaged concentrations. The DGT technique has in several previous studies been suggested to mimic biological uptake of trace metals. Four speciation/fractionation techniques – DGT, transplanted aquatic moss, ultrafiltration (1 kDa) and membrane filtration (0.22 μm) – were used in parallel for measurements of Al, Cd, Co, Cu, Fe, Mn, Ni and Zn in a contaminated freshwater stream in northern Sweden. Differences and similarities between the methods were investigated and how these depend on geochemical water quality. Strong correlations between DGT-results and the concentrations in the filtrate (<0.22 μm) and ultrafiltration permeate for Al, Cu, Cd, Co and Zn were detected and, generally, elevated trace metal concentrations were found in the transplanted moss, compared to moss from the non-polluted reference stream. However, no correlation between moss and DGT-labile concentrations could be discerned. / Godkänd; 2011; 20110921 (helost)

The increasing load of toxic elements entering the ecosystems, as a consequence of anthropogenic processes, has grown public awareness in the last decades, resulting in a great number of studies focusing on pollution sources, transport, distribution, interactions with living organisms and remediation. Physical/chemical processes that drive the uptake, assimilation, compartmentation and translocation of heavy metals in biota has received a great deal of attention recently, since elemental concentrations and isotopic composition in biological matrices can be used as  probes of both natural and anthropogenic sources. Further they can help to evaluate fate of contaminants and to assess bioavailability of such elements in nature. While poorly defined isotopic pools, multiple sources and fractionating processes add complexity to source identification studies, tracing is hindered mainly by poorly known or unidentified fractionating factors. High precision isotope ratio measurements have found increasing application in various branches of science, from classical isotope geochronology to complex multi-tracer experiments in environmental studies. Instrumental development and refining separation schemes have allowed higher quality data to be obtained and played a major role in the recent progress of the field. The use of modern techniques such as inductively coupled plasma sector field mass spectrometry (ICP-SFMS) and multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) for trace and ultra-trace element concentrations and isotope ratio measurements have given new opportunities.  However, sources of errors must be accurately evaluated and avoided at every procedural step. Moreover, even with the utilization of sound analytical measurement protocols, source and process tracing in natural systems can be complicated further by spatial and temporal variability. The work described in the present thesis has been focused primarily on analytical method development, optimization and evaluation (including sample preparation, matrix separation, instrumental analysis and data evaluation stages) for isotopic and multi-elemental analyses in environmental samples at trace and ultra-trace levels. Special attention was paid to evaluate strengths and limitations of the methods as applied to complex natural environments, aiming at correct interpretation of isotopic results in environmental forensics. The analytical protocols covered several isotope systems of both stable (Cd, B, Cr, Cu, Fe, Tl and Zn) and radiogenic (Os, Pb and Sr) elements. Paper I was dedicated to the optimization and testing of a rapid and high sample throughput method for Os concentrations and isotope measurements by ICP-SFMS. If microwave (MW) digestion followed by sample introduction to ICP-SFMS by traditional solution nebulization (SN) offered unparalleled throughput important for processing large number of samples, high-pressure ashing (HPA) combined with gas-phase introduction (GPI) proved to be advantageous for samples with low (below 500 pg) analyte content. The method was applied to a large scale bio-monitoring case, confirming accumulation of anthropogenic Os in animals from an area affected by emissions from a stainless steel foundry. The method for Cr concentrations and isotope ratios in different environmental matrices was optimized in Paper II. A coupling between a high pressure/temperature acid digestion and a one pass, single column matrix separation allowed the analysis of chromites, soils, and biological matrices (first Cr isotope study in lichens and mosses) by ICP-SFMS and MC-ICP-MS. With an overall reproducibility of 0.11‰ (2σ), the results suggested a uniform isotope composition in soil depth profiles. On the other hand a strong negative correlation found between δ53Cr and Cr concentrations in lichens and mosses indicates that airborne Cr from local anthropogenic source(s) is depleted in heavy isotopes, therefore highlighting the possibility of utilization of Cr isotopes to trace local airborne pollution source from steel foundries.   Paper III describes development of high-precision Cd isotope ratio measurement by MC-ICP-MS in a variety of environmental matrices. Several digestion methods (HPA, MW, ultrawave and ashing) were tested for sample preparation, followed by analyte separation from matrix using ion-exchange chromatography. The reproducibility of the method (2σ for δ114Cd/110Cd) was found to be better than 0.1‰. The method was applied to a large number of birch leaves (n&gt;80) collected at different locations and growth stages. Cd in birch leaves is enriched in heavier isotopes relative to the NIST SRM 3108 Cd standard with a mean δ114Cd/110Cd of 0.7‰. The fractionation is assumed to stem from sample uptake through the root system and element translocation in the plant and it exhibits profound between-tree as well as seasonal variations. The latter were compared with seasonal isotopic variations for other isotopic systems (Zn, Os, Pb) in the same trees to aid a better understanding of underlying processes. In Paper IV the number of isotope systems studied was extended to include B, Cd, Cu, Fe, Pb, Sr, Tl and Zn. The analytical procedure utilized a high pressure acid digestion (UltraCLAVE), which provides complete oxidation of the organic material in biological samples, and a two-column ion-exchange separation which represents further development of the separation scheme described in Paper III. Such sample preparation ensures low blank levels, efficient separation of matrix elements, sufficiently high analyte recoveries and reasonably high sample throughput. The method was applied to a large number of biological samples (n&gt;240) and the data obtained represent the first combined characterization of variability in isotopic composition for eight elements in leaves, needles, lichens and mushrooms collected from a geographically confined area. To further explore the reason of variability observed, soil profiles from the same area were analyzed for both concentrations and isotopic compositions of B, Cd, Cr, Cu, Fe, Pb, Sr, Tl and Zn in Paper V. Results of this study suggest that the observed high variability can be dependent on operationally-defined fractions (assessed by applying a modified SEP to process soil samples) and on the typology of the individual matrix analyzed (assessed through the coupling of soil profile results to those obtained for other matrices: lysimetric waters, mushrooms, litter, needles, leaves and lichens). The method development conducted in this work highlights the importance of considering all possible sources of biases/errors as well as possibility to use overlapping sample preparation schemes for multi-isotope studies. The results obtained for different environmental matrices represent a starting point for discussing the role of natural isotopic variability in isotope applications and forensics, and the importance of in-depth knowledge of the multiple parameters affecting the variability observed.

The Geological Survey of Sweden, SGU, has carried out geochemical mapping for several decades. In 1983, two regional mapping programmes were initiated, aiming at a nation wide coverage. While one of the programmes, till geochemical mapping, was focussed mainly on production of regional baseline information for mineral exploration purposes, the second programme was more adapted to environmental issues. This second programme constitutes sampling of living matter (roots of Carex species, Filipendula Ulmaria, and the bryophyte Fontinalis Antipyretica) in minor streams, and is called biogeochemical mapping. Despite more than twenty years of mapping, several aspects of the method and its results still remain unexplored. Furthermore, results from the biogeochemical mapping programme have traditionally been expressed as residuals (contents in ash, contents of iron and manganese, and loss on ignition have been used as independent variables). This residual method however is not used in the Fontinalis antipyretica monitoring method developed by the Swedish Environmental Protection agency (SEPA), thus use of the SGU regional data set as baseline information in a SEPA context is very difficult. Therefore, a transition to dry weight is desirable. This however introduces several problems, e. g. for chromium. Following an introduction to the development and current status of the geochemical mapping programmes, two environmental applications of the biogeochemical dataset have been developed through a combination of statistical and geostatistical methods. In the first, subsets of the biogeochemical database have been created and used in order to determine possible species dependent effects, spatial correlation and influence of main elements like titanium, iron, aluminium, silica, and manganese on chromium. In the second, relations between the chemical composition of samples and areas known (and suspected) to host acid sulphate soils are studied. The species studied vary somewhat regarding metal contents. Such differences are assumed to be related to uptake mechanisms. However, for most elements the differences are much smaller than the spatial variance and the results from the mapping programme can be used without respect to species. Other geochemical databases (till and soil), as well as geological data, have been used in order to examine the geochemical properties of the biogeochemical samples, and factors affecting spatial distribution, e.g. relationships with quaternary deposits. Chromium contents in biogeochemical samples are strongly related to titanium, silica, zirconium and ash content. This correlation is not present in glacial till and other quaternary deposits. Normalisation of chromium by titanium is an efficient tool to separate anthropogenic point source pollution from chromium derived from natural sources. Acid sulphate soils have a strong impact on surface waters, and ecosystems therein. The metal contents of biogeochemical samples in two separate areas where acid sulphate soils occur display similar features as stream water. Of the elements studied, levels of yttrium, nickel, cobalt, zinc, sulphur, (and others) are significantly higher in samples collected in areas with postglacial clays and gyttja containing soils, deposits that are known to comprise acid sulphate soils. The metal content of the biogeochemical samples can be used in order to detect active acid sulphate soils. / <p>Godkänd; 2005; 20061211 (haneit)</p>

No description available.