Viktor Sjöberg

Comparison of MP AES and ICP-MS for analysis of principal and selected trace elements in nitric acid digests of sunflower (Helianthus annuus)

The use of nitrogen as plasma gas for microwave plasma atomic emission spectroscopy (MP AES) is an interesting development in analytical science since the running cost can be significantly reduced in comparison to the inductively coupled argon plasma. Here, we evaluate the performance of the Agilent 4100 MP AES instrument for the analysis of principal metals (Ca, K, Mg, and Na), lithogenic metals (Al, Fe, and Mn) and selected trace metals (As, Ba, Cd, Co, Cr, Cu, Mo, Ni, Pb, V, and Zn) in nitric acid plant digests. The digests were prepared by microwave-assisted dissolution of dry plant material from sunflower (Helianthus annuus) in concentrated nitric acid. Comparisons are made with analysis of the same solutions with ICP-MS (Agilent 7500cx) using the octopole reaction system (ORS) in the collision mode for As, Fe, and V. The limits of detection were usually in the low µg L(-1) range and all principal and lithogenic metals were successfully determined with the MP AES and provided almost identical results with the ICP-MS. The same applies for the selected trace metals except for As, Co and Mo where the concentrations were below the detection limit with the MP AES. For successful analysis we recommend that (i) only atom lines are used, (ii) ionization is minimized (e.g. addition of CsNO3) and (iii) the use of internal standards should be considered to resolve spectral interferences.

Bioleaching of Shale – Impact of Carbon Source

Bioleaching is often used for processing low-grade shale feedstock and the microbial community used for that purpose is supplied with nutrients such as sugar and/or Fe2+. In the present study, the leaching efficiency was tested when crushed weathered shale was mixed with aspen wood shavings and kept moist, at the mixtures field capacity. The purpose was to investigate whether a more complex carbon source and a lower content of water may be a feasible way of lowering the cost for bioleaching. After 56 days of incubation the amount of uranium mobilized from the shale reached some 1.7% with a minimum of effort and cost.

Impact of humic substances on uranium mobility in soil : a case study from the Gessenwiese test field

Uranium has been mined in Namibia since the 1970s. The worldwide increasing need for energy in the early 2000s has triggered an increased interest in uranium exploration, often referred to as “the Namibian Uranium Rush”. All in all, five mining licenses have been granted by the Namibian Government, with currently two mines in operation, a third under construction undertaking trial mining, the fourth under care and maintenance after completing a large scale and successful trial period and the fifth in project finance negotiations. In addition, highly intensive prospecting activities at additional deposits are at an advanced stage. The finalization of the strategic environmental impact assessment (SEA) on uranium mining in 2010, the first of its kind and scale in the world, has enabled the Namibian government to assess this uranium rush and its tremendous legal, socioeconomic and environmental impacts and to prepare for different future scenarios, including both, a skyrocketing and a complete breakdown of demand scenario. The Fukushima disaster and plans of the Namibian government to significantly increase royalties and company taxes in 2011 have threatened the market situation, forcing investors to reevaluate Namibian uranium mining projects. However, with the tax and royalty increase initiative since withdrawn, most projects have soon been back on track with significant pace, when again low market prices hampered some of the projects or even completely put them on hold.

Metal contaminated soil leachates from an art glass factory elicit stress response, alter fatty acid metabolism and reduce lifespan in Caenorhabditis elegans

The present study evaluated the toxicity of metal contamination in soils from an art glass factory in Småland Sweden using a Caenorhabditis elegans nematode model. The aim of the study was to chemically analyze the soil samples and study the biological effects of water-soluble leachates on the nematodes using different physiological endpoints. The total metal content showed that As, Cd and Pb were at levels above the guideline values for soils in areas around the factory. Less than 10% of the total metal content in the soil was found in the water-soluble leachates, however, Al, As, Fe and Pb remained higher than the guideline values for safe drinking water. Exposure of C. elegans to the water-soluble leachates, at both post-hatching larvae stage (L1-young adult) for 48 h and at the young adult stage (L4) for 6 h, showed significant gene alteration. Although the nematodes did not exhibit acute lethality, lifespan was significantly reduced upon exposure. C. elegans also showed altered gene expression associated with stress response and fat metabolism, as well as enhanced accumulation of body fat. The study highlighted the significance of assessing environmental samples using a combination of gene expression analysis, fatty acid metabolism and lifespan for providing valuable insight into the negative impact of metals. The altered fat metabolism and reduced lifespan on exposure to soil leachates motivates further studies to explore the mechanism of the toxicity associated with the metals present in the environment.

Release of uranium from weathered black shale in meso-scale reactor systems – first year of data

Release of uranium from weathered black shale in meso-scale reactor systems : first year of data

Uranium induced stress promotes fungal excretion of uranium/metal stabilizing ligands : Analysis of metal-organic compounds with Size Exclusion Chromatography and Inductively Coupled Plasma-Mass Spectroscopy

Weathering of pyrite rich alum shale processing waste has led to metal pollution in Kvarntorp, Sweden. Here we use a fungal strain isolated from the site to monitor the excretion of uranium/metal stabilizing ligands under uranium induced stress. After 2 weeks 91 % was lost from a 10 mg L−1 solution but 57 % already within 10 min. The formation of colloidal/particulate uranium is mainly controlled by organic exudates phosphorus excreted by the fungus. Most likely, the change in solution properties from metabolic processes resulted in the formation species through adsorption and precipitation.

Phytostabilization of uranium-containing shale residues using Hieracium pilosella

A greenhouse pot experiment was conducted to evaluate the feasibility of using Hieracium pilosella and soil microorganisms for phytostabilization of uranium-containing shale residues. Conductivity of leachates significantly decreased and pH increased when plants were grown on the substratum. H. pilosella has ability to change the hydrochemical parameters and to decrease the mobilization of uranium. Moreover, H. pilosella is able to accumulate significant amounts of uranium in the shoots.