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[en] Nitrate pollution sources in water can be discriminated through the analysis of its stable δ15N and δ18O isotopes. Pseudomonas aureofaciens bacteria enzymatically convert aqueous NO3- to gaseous N2O in a process called denitrification. The gaseous N2O can then be measured on an isotopic laser spectroscope to attain concentration, as well as signatures of δ15N and δ18O isotopes, which can then be utilized as tracers to understand the sources of dissolved nitrate. The advantages of the denitrifier method compared to existing nitrate isotope discrimination methods are the small sample volume required, that no toxic chemicals are added, and that it can be used for samples with low concentrations. In addition to providing robust analysis, the laser spectroscopy method can be customized to accommodate a large sample input. Furthermore, this method is applicable in both, freshwater and seawater, and can be easily applied to any water sample sources with a nitrate contamination concentration of 2ppm and above. This SOP was developed to provide illustrated guidance for determining the δ15N and δ18O isotopic composition of nitrate (NO3-) in water samples. It provides step-by-step guidance to scientists, technicians and students implementing procedures and tools to prepare samples for isotope analysis. Determination of the stable nitrogen isotope composition allows Member States to better determine and understand the sources and forms of nitrate for improved water and nutrient management practices.
[en] The worldwide comparison of stable 15N and 13C isotope measurements provides confidence in the analytical performance of stable isotope laboratories and hence an important tool for external quality control. The 2017 Proficiency Test (PT) on 15N and 13C isotopic abundance in plant materials, organized by the University of Wageningen, the Netherlands, and funded by the SWMCN Laboratory has been successfully completed. In total eleven stable isotope laboratories participated in the PT-round 2017: Africa (1): Morocco, Asia (3): Pakistan and Philippines (2 labs), Europe (3): Austria Belgium and France, Latin America (3): Argentina, Brazil and Chile and South Pacific (1): New Zealand. Eight out of nine laboratories participating in the nitrogen analysis reported 15N-data within the control limits for the enriched plant sample and nine out of nine participating laboratories in carbon analysis reported 13C isotopic abundance results within the control limits.
[en] Uranium ores mined for industrial use are typically acid-leached to produce yellowcake and then converted into uranium halides for enrichment and purification. These anthropogenic chemical forms of uranium are distinct from their mineral counterparts. The purpose of this study is to use soft X-ray absorption spectroscopy to characterize several common anthropogenic uranium compounds important to the nuclear fuel cycle. Chemical analyses of these compounds are important for process and environmental monitoring. X-ray absorption techniques have several advantages in this regard, including element-specificity, chemical sensitivity, and high spectral resolution. Oxygen K-edge spectra were collected for uranyl nitrate, uranyl fluoride, and uranyl chloride, and fluorine K-edge spectra were collected for uranyl fluoride and uranium tetrafluoride. Interpretation of the data is aided by comparisons to calculated spectra. The effect of hydration state on the sample, a potential complication in interpreting oxygen K-edge spectra, is discussed. These compounds have unique spectral signatures that can be used to identify unknown samples. - Highlights: • NEXAFS peaks can be used to identify anthropogenic uranium compounds. • Calculations allow the origin of these peaks to be determined. • The presence of water does not preclude uranyl compound identification. • The fluorine K-edge is particularly useful for compound identification.
[en] Under oxic conditions, Tc exists as the soluble, weakly sorbing pertechnetate [TcO4-] anion. The reduced form of technetium, Tc(IV), is stable in anoxic environments and is sparingly soluble as TcO2 · nH2O(S). Here we investigate the heterogeneous reduction of Tc(VII) by Fe(II) adsorbed on Al (hydr)oxides [diaspore (α-AlOOH) and corundum (α-Al2O3)]. Experiments were performed to study the kinetics of Tc(VII) reduction, examine changes in Fe surface speciation during Tc(VII) reduction (Moessbauer spectroscopy), and identify the nature of Tc(IV)-containing reaction products (X-ray absorption spectroscopy). We found that Tc(VII) was completely reduced by adsorbed Fe(II) within 11 (diaspore suspension) and 4 days (corundum suspension). Moessbauer measurements revealed that the Fe(II) signal became less intense with Tc(VII) reduction and was accompanied by an increase in the intensity of the Fe(III) doublet and magnetically ordered Fe(III) sextet signals. Tc-EXAFS spectroscopy revealed that the final heterogeneous redox product on corundum was similar to Tc(IV) oxyhydroxide, TcO2 · nH2O
[en] Bulk density is defined as the dry weight of soil per unit volume of undisturbed soil. • Bulk density can be used to give an indication of the porosity and structure of the soil influencing O_2 and H_2O movement in the soil. • Soils with a bulk density higher than 1.6 g/cm"3 may restrict root development. • Bulk density is also a measurement of the degree of compaction of the soil. • Bulk density increases with compaction and tends to increase with soil depth. • Sandy soils tend to have higher bulk density (1.4-1.5 g/cm"3) than clay soils (1.2-1/3g/cm"3). The measurement of soil bulk density is carried out by collecting undisturbed soil samples through inserting metal rings (with a known volume) into the soil, and determining the weight of the collected soil after drying
[en] Full text: SWMCNL has developed methods using a carbon dioxide carbon isotope analyser to identify agricultural practices that promote climate-smart agriculture by optimizing soil organic carbon sequestration. These methods along with an example case study are now being compiled into a TECDOC that will guide users in the operation of the laser carbon dioxide carbon isotope analyser as well as in data analysis that can, ultimately be used to evaluate soil management practices. Specifically, the TECDOC will describe: 1) creating reference gases for gas isotope analysis, 2) measuring with the laser carbon dioxide carbon isotope analyser in continuous basic-free flow mode, 3) measuring with the laser carbon dioxide carbon isotope analyser in injection/batch mode, 4) correcting data collected with the laser carbon dioxide carbon isotope analyser, and 5) a case study measuring carbon loss of mulch applied in a soil incubation experiment. In contrast to existing information on the use of these analysers, this TECDOC will provide step-by-step instructions on how to perform analyser measurements and data analysis with illustrations for guidance. The goal of this TECDOC is to guide users in the use of laser carbon dioxide carbon isotope analysers to ultimately evaluate the potential of soil management practices to optimize soil organic carbon sequestration for climate-smart agriculture. (author)
[en] Full text: As of November 2017, 3850 plant, soil and water samples were analysed for stable isotopes and 200 samples were measured for fallout radionuclides in the SWMCN Laboratory. Most analyses were carried out to support Research and Development activities at the SWMCNL focusing on the design of affordable isotope and nuclear techniques to improve soil and water management in climate-smart agriculture. Analytical support has also been given to the Food and Environmental Protection Laboratory with about 65 samples analysed. In 2017, major focus of the SWMCN Laboratory has been on stable isotope measurements of greenhouse gases (13C-CO2 and 15N-N2O) through laser isotope analysers. (author)
[en] The European Geosciences Union (EGU) General Assembly 2015 that took place at the Austria Center of Vienna, from 12-17 April 2015, was a big success with 4870 oral, 8489 poster, and 705 PICO (Presenting Interactive COntent™) presentations as well as 11837 scientists attending from 108 different countries. This year again, the activities of the SWMCN Laboratory were well represented with 3 PICO presentations during the SSS12.10 session (i.e. Soil and sediment tracing techniques for understanding environmental processes)
[en] Full text: The worldwide comparison of stable 15N and 13C isotope measurements provides confidence in the analytical performance of stable isotope laboratories and hence making it an important tool for external quality control. The 2018 Proficiency Test (PT) on 15N and 13C isotopic abundance in plant materials, organized by the University of Wageningen, the Netherlands, and funded by the SWMCN Laboratory was successfully completed. The Wageningen Evaluating Programs for Analytical Laboratories (WEPAL, http://www.wepal.nl) is accredited for the organization of Inter-laboratory Studies by the Dutch Accreditation Council. Every year, one 15N-enriched plant test sample is included in one round of the WEPAL IPE (International Plant- Analytical Exchange) Programme. A special evaluation report for IAEA participants on the analytical performance in stable isotope analysis is issued by the SWMCN Laboratory and sent to the participants together with a certificate of participation additionally to the regular WEPAL evaluation report. The participation fee for one round per year is covered by the IAEA. In total, eleven stable isotope laboratories participated in the PT-round 2018: Africa (1): Morocco; Asia and the Pacific (3): New Zealand, Pakistan and Philippines; Europe (4): Austria, Belgium, Germany and France; Latin America (3): Argentina, Brazil and Chile. All nine laboratories participating in the nitrogen analysis test reported 15N-data within the control limits for the enriched plant sample and seven out of nine participating laboratories in carbon analysis test reported 13C isotopic abundance results within the control limits. (author)