ALBERT

Description: 〈span〉〈div〉Abstract〈/div〉The nanoSIMS (nanometre-resolution secondary ion mass spectrometry) microanalytical platform is used, for the first time, for direct 〈span〉in situ〈/span〉 visualization of medium half-life radionuclide (RN) distributions (〈sup〉226〈/sup〉Ra – 1602y; 〈sup〉210〈/sup〉Pb – 22.3y) in copper sulphide-bearing ore and copper sulphide flotation concentrate samples. More than 200 grains have been mapped, all with an Hyperion (H200) RF plasma oxygen ion source. Sufficient counts for masses of interest allowed the generation of maps that stand as a proof of concept for further detailed work to address the physical locations of radionuclides of main interest. The issue of potential isobaric interfering masses has been addressed and partially resolved. The distribution of the studied radionuclides, both in relation to host minerals and in relation to each other, is logical and clearly supported by well-established theories of deportment, diffusion, and redistribution. Isotope maps for 〈sup〉210〈/sup〉RN (〈sup〉210〈/sup〉Pb, 〈sup〉210〈/sup〉Po and 〈sup〉210〈/sup〉Bi) and 〈sup〉226〈/sup〉Ra maps tended to show RN distribution either within minerals (evenly distributed or zoned), as ‘hot spots’ on grain surfaces/mineral boundaries, or between cleavage planes of micaceous minerals. NanoSIMS element mapping of radionuclides may have widespread application for the disposal and long-term storage of nuclear waste, radioisotope monitoring, forensic science, nuclear and materials science, nuclear medicine, minerals engineering, and isotope geochemistry.〈/span〉

Description: Nitrogen (N) isotope ratios (15N/14N) provide integrative constraints on the N inventory of the modern ocean. Anaerobic ammonium oxidation (anammox), which converts ammonium and nitrite to dinitrogen gas (N2) and nitrate, is an important fixed N sink in marine ecosystems. We studied the so far unknown N isotope effects of...

Description: 〈span〉〈div〉Abstract〈/div〉Aluminum-phosphate-sulfate (APS) minerals of the alunite supergroup are minor components of uranium-bearing copper ores from the Olympic Dam deposit, South Australia. They typically represent a family of paragenetically late replacement phases after pre-existing REE-bearing phosphates (fluorapatite, monazite, and xenotime). Characterization with respect to textures and composition allows two groups to be distinguished: Ca-Sr-dominant APS minerals that fall within the woodhouseite and svanbergite compositional fields; and a second REE- and phosphate-dominant group closer to florencite in composition. All phases nevertheless display extensive solid solution among end-members in the broader APS clan and show extensive compositional zoning at the grain-scale. Samples representative of the deposit (flotation concentrate and tailings), as well as those that have been chemically altered during the processing cycle (acid leached concentrate), were studied for comparison. NanoSIMS isotope mapping provides evidence that the APS minerals preferentially scavenge and incorporate daughter radionuclides of the 〈sup〉238〈/sup〉U decay chain, notably 〈sup〉226〈/sup〉Ra and 〈sup〉210〈/sup〉Pb, both over geological time within the deposit and during ore processing. These data highlight the role played by minor phases as hosts for geologically mobile deleterious components in ores as well as during mineral processing. Moreover, Sr-Ca-dominant APS minerals exhibit preferential sorption of Pb from fluid sources, in the form of both common Pb and 〈sup〉210〈/sup〉Pb, for the first time revealing potential pathways for 〈sup〉210〈/sup〉Pb elimination and reduction from ore processing streams.〈/span〉

Description: Palsa peats are unique northern ecosystems formed under an arctic climate and characterized by an unique biodiversity and ecology. The stability of the palsas are seriously threatened by climate warming which will change the permafrost dynamic and results in degradation of the mires. We used stable carbon isotope depth profiles in two palsa mires of Northern Sweden to track environmental change during the formation of the mires. Carbon isotope (δ13C) depth profile of the yet undisturbed mire Storflaket indicated very low to no degradation of the peat in the water saturated depressions (hollows) but increased rates of anaerobic degradation at the Stordalen site. The latter might be induced by degradation of the permafrost cores in the uplifted areas (hummocks) and subsequent braking and submerging of the hummock peat into the hollows due to climate warming. Carbon isotope depth profiles of hummocks indicated a turn from aerobic mineralisation to anaerobic degradation at a peat depth between 4 to 25 cm. The age of these turning point was 14C dated between 150 and 670 years and could thus not be caused by anthropogenically induced climate change. We found the uplifting of the hummocks due to permafrost heave the most likely explanation for our findings. We thus concluded that differences in carbon isotope profiles of the hollows might point to the disturbance of the mires due to climate warming or due to differences in hydrology. The characteristic profiles of the hummocks are indicators for micro-geomorphic change during permafrost up heaving.

Description: Palsa peats are unique northern ecosystems formed under an arctic climate and characterized by a high biodiversity and sensitive ecology. The stability of the palsas are seriously threatened by climate warming which will change the permafrost dynamic and induce a degradation of the mires. We used stable carbon isotope depth profiles in two palsa mires of Northern Sweden to track environmental change during the formation of the mires. Soils dominated by aerobic degradation can be expected to have a clear increase of carbon isotopes (δ13C) with depth, due to preferential release of 12C during aerobic mineralization. In soils with suppressed degradation due to anoxic conditions, stable carbon isotope depth profiles are either more or less uniform indicating no or very low degradation or depth profiles turn to lighter values due to an enrichment of recalcitrant organic substances during anaerobic mineralisation which are depleted in 13C. The isotope depth profile of the peat in the water saturated depressions (hollows) at the yet undisturbed mire Storflaket indicated very low to no degradation but increased rates of anaerobic degradation at the Stordalen site. The latter might be induced by degradation of the permafrost cores in the uplifted areas (hummocks) and subsequent breaking and submerging of the hummock peat into the hollows due to climate warming. Carbon isotope depth profiles of hummocks indicated a turn from aerobic mineralisation to anaerobic degradation at a peat depth between 4 and 25 cm. The age of these turning points was 14C dated between 150 and 670 yr and could thus not be caused by anthropogenically induced climate change. We found the uplifting of the hummocks due to permafrost heave the most likely explanation for our findings. We thus concluded that differences in carbon isotope profiles of the hollows might point to the disturbance of the mires due to climate warming or due to differences in hydrology. The characteristic profiles of the hummocks are indicators for micro-geomorphic change during permafrost up heaving.