25 research outputs found

    European radon abatement policy: state and ongoing discussion

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    Radon is a hazardous air pollutant which can cause detriment to individuals and to the society. Thus, the natural consequence is avoiding it or in practice, limiting exposure. This has led to regulation on national and international level whose objective is reduction of radon exposure. In Europe, the Basic Safety Standards (BSS) issued in 2013, whose implementation is mandatory for EU Member States, caused a boost to efforts towards radon regulation as well as to radon research since a number of components of radon abatement policy appeared not resolved sufficiently reliable in the sense of quality assurance. In this contribution, we present the state of implementation of EURATOM Basic Safety Standards in Europe and in Germany, as a particular example. We also address a number of topics currently discussed

    ATLAS Run 1 searches for direct pair production of third-generation squarks at the Large Hadron Collider

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    Elemental and isotope fingerprint of metal deficiency in soils

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    Metal deficiency in soils is a frequently observed phenomenon in (sub)-tropical regions, and both natural and anthropogenic processes contribute to the depletion of soil reservoirs. Advanced chemical weathering, in old regolith, can lead to very severe natural depletion of metals in certain soil types, while soil over-cropping represents the human impact that increases the net offtake of metals from many soils. In both cases, the health of humans can suffer since many trace metals have vital functions in the human body. For example, nearly half the world population is affected by Zn deficiency symptoms caused by over-dependence on local crops that are grown on Zn deficient soils. This is all the more concerning in view of the anticipated rise in world population that will put additional demands on crop production with likely knock-on effects for essential metal depletion in soil. This thesis presents petrographic, mineralogical and geochemical as well as isotopic investigations of two contrasting weathering profiles from the Deccan Traps, India to investigate the natural causes of metal deficiency in soils. Major- and trace elements (including essential metals), organic carbon (C) content, chemical weathering indices, uranium-series (U-series) systematics as well as zinc (Zn)- and chromium (Cr)- isotopes were analysed to quantify the mineralogical transformations, biogeochemical processes and environmental factors that lead to the loss of metals during soil formation. In addition, agricultural topsoil and animal manure samples were investigated from Zn deficient regions in India to compare and contrast their biogeochemical fingerprints to the findings from the weathering profiles. The work revealed that actively weathering soils are strongly depleted in the isotope 234U, hosted in labile sites in minerals. The chemical breakdown of metal-rich primary silicates and clay minerals in saprolite results in the mobilisation of substantial amounts of metals to aqueous solutions and plants. Ultimately, the breakdown of these minerals contributes to oceanic metal inventories, exemplified by the excess of 234U in seawater. By contrast, strongly weathered soils (i.e. laterites) have lost their natural capacity to supply bio-available forms of metals to the environment and concentrations of residual essential metals such as Zn or redistributed Cr are mainly hosted in weathering resistant iron (Fe)-oxides. The isotopic fractionation of Zn and Cr is strongly affected by the formation of Fe-oxides, whereas the metal stable isotope ratios in actively weathering saprolite remain in the range of unweathered bedrocks. Hence, Zn isotopes can be used to distinguish between fertile and Zn deficient soils. Importantly, the geochemical fingerprints in the agricultural topsoils reveal that high concentrations of essential metals (Zn, copper (Cu), cobalt (Co), nickel (Ni), Cr) are also hosted in bio-unavailable oxide phases, whereas the bio-available pool in the inorganic soil constituents is much lower. Since the bio-available concentrations of metals in animal manure are too low to counterbalance essential metal deficiencies in Indian soils, their fertility status remains delicate without application of industrial metal fertilisers. Overall, the findings of this thesis suggest that geochemical and isotopic data can contribute to a deeper understanding of metal deficiency in soils and help in the development of more sustainable farming practices in (sub)-tropical regions

    Silicon and chromium stable isotopic systematics during basalt weathering and lateritisation: A comparison of variably weathered basalt profiles in the Deccan Traps, India

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    Global biomass production is fundamentally affected by the hydrological cycling of elements at the Earth?s surface. Continental weathering processes are the major source for most bio-essential elements in marine environments and therefore affect primary productivity. In addition, critical zone biomass depends on energy and chemical exchange reactions in weathering profiles. The latter reservoirs are in turn influenced by different climatic conditions that control weathering and pore water parameters like pH and Eh, these then regulate mineral break down rates that dictate the mobility and mass flux of elements. Two Deccan Trap basalt-weathering profiles of contrasting age and alteration intensity provide a natural laboratory for investigating the effects of rock alteration on Si and Cr and their isotopic systematics. The sub-recent Chhindwara profile has progressed to a moderate degree of alteration (saprolite), whilst the Paleogene Bidar example displays an extremely altered laterite. The Chhindwara profile shows a near uniform Cr and Si concentration and isotopic composition, whereas the Bidar profile is characterised by an intense loss of Si, a large enrichment of Cr within the most altered uppermost levels, and a wide range of Cr stable isotope ratios (-0.85 to 0.36 ? ?53/52Cr). A co-variation between Si and Cr isotopes, as well as their co-variation with iron content, provides empirical evidence that iron redistribution within the profile has a large effect on Cr mobility. Therefore, it is concluded that iron oxides exert a primary control over the isotopic composition of both Cr and Si in pore waters of laterites. Because laterite formation is promoted by tropical climates, the results of this study provide new evidence to suggest that the hydrological Cr and Si fluxes originating from continental weathering have changed in accordance with large-scale, deep time climate variation and continental plate configuration. An increased flux of Si and greater magnitude of Cr mobility and isotopic fractionation are possibly amplified under CO2-rich, greenhouse episodes and/or when large landmasses were tectonically arranged at near equatorial latitudes

    The role of pedogenesis and natural fertiliser as vectors for essential metal content in agricultural topsoils, Central India

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    Essential trace metals are well known for their environmental toxicity and for being part of complex bio-chemical cycles. Their role as critical micronutrients, delivering vital health benefits, is less widely discussed and understood, holding back strategies for combatting malnutrition. Crops grown on many Indian soils suffer from deficiencies in essential metals, notably iron (Fe), zinc (Zn), and molybdenum (Mo). The list of deficient metals will likely grow due to increasing future crop demand. Geostatistical analysis of soils and farmyard manure (FYM), the predominant fertiliser, implies that residual oxide minerals carry high concentrations of the essential trace metals Fe, Zn, copper (Cu), chromium (Cr), nickel (Ni), cobalt (Co), manganese (Mn) not only in soil but also in FYM (especially Fe, Cr, Cu, Co and Ni). A geochemical survey across a road traverse of 600¬†km, encompassing an area of c. 15,000¬†km2, was conducted in Central India to evaluate reported essential metal deficiency in key agricultural topsoils. Importantly, our evaluation of the element cycling in this system reveals that despite high bulk concentrations, some key metals remain bio-unavailable. In effect, the existence of refractory (weathering-resistant) oxides is likely a significant factor for deficiency symptoms in the soil‚Äďplant-fertiliser cycle. Further, mass balance calculations of the bioavailable pool of metals imply that only Fe and Mn are present in sufficient quantities to combat deficiency problems. Notwithstanding this limitation of FYM, its high organic carbon content, as well as its importance for Zn, Cu and Fe, validates its traditional use to maintain the fertility and physical condition of Indian topsoils.</p

    Alfred Kröner (1939-2019)

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    Th/U and U series systematics of saprolite: importance for the oceanic 234U excess

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    The presence of excess U-234 in seawater is a compelling argument for active delivery of solutes from the continents to the oceans. Previous studies found, however, that the complementary U-234 deficit on the continents is surprisingly modest, which would require protracted U loss from a large continental weathering pool. Our new compilation and statistical analysis of the published data, coupled with a mass balance calculation demonstrates that the apparent small U-234 deficit in the continental weathering pool implied by previous studies is insufficient to balance the observed oceanic excess. Our new data for a saprolite weathering profile developed on Deccan basalt reveal a very strong overall loss of U (elevated Th/U) with a strong U-234 deficit attributable to chemical weathering. The U and U-234 deficits reported here from a geologically recent saprolite confirm the importance of the early stages of chemical weathering at the weathering front in the supply of nutrients to the oceans. Thus, as much as half the oceanic U-234 inventory is likely sourced from a thin active saprolite zone

    Archaean granulite-facies paragneisses from central Swaziland: inferences on Palaeoarchaean crustal reworking and a complex metamorphic history

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    We present a petrographic, petrological, geochemical, and geochronological study (U-Pb/Lu-Hf) on granulite-facies paragneisses of the Mahamba Gneiss Complex in central Swaziland, eastern Kaapvaal Craton. Our data suggest that prograde metamorphism occurred at c. 3.07 Ga. Dating of detrital zircons of a metapelite in combination with geochronological and ambiguous structural relationships with granitoid gneisses suggests two possible scenarios: (1) the time of deposition of the sedimentary protoliths is prior to c. 3.58 Ga; (2) c. 3.58 Ga granitoid crust was the basement for the sedimentary protoliths. Furthermore, enrichment in Ni and Cr in the Mahamba metasediments may originate from erosion of a greenstone terrane similar in composition to the dominantly mafic and ultramafic lithologies of the Barberton Greenstone Belt or Dwalile supracrustal belt. Evidence for an older crustal basement is provided by the oldest detrital zircons, which yield ages up to c. 3.7 Ga. Because the metamorphic conditions of metapelitic rocks have no similarity to P-T paths of modern subduction-collision tectonic settings we conclude that the metamorphic history of the Mahamba Gneiss Complex cannot be explained by this model. We propose that deformation and metamorphism occurred through intracratonic contraction and a thermal event possibly related to Mpuluzi batholith emplacement

    Elemental and isotopic behaviour of Zn in Deccan basalt weathering profiles: Chemical weathering from bedrock to laterite and links to Zn deficiency in tropical soils

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    Zinc (Zn) is a micronutrient for organisms and essential for plant growth, therefore knowledge of its elemental cycling in the surface environment is important regarding wider aspects of human nutrition and health. To explore the nature of Zn cycling, we compared its weathering behaviour in a sub-recent regolith versus an ancient laterite profile of the Deccan Traps, India -an area of known soil Zn deficiency. We demonstrate that progressive breakdown of primary minerals and the associated formation of phyllosilicates and iron oxides leads to a depletion in Zn, ultimately resulting in a loss of 80% in lateritic residues. This residue is mainly composed of resistant iron oxides and hydroxides ultimately delivering insufficient amounts of bio-available Zn. Moreover, (sub)-tropical weathering in regions experiencing extended tectonic quiescence (e.g., cratons) further enhance the development of old and deep soil profiles that become deficient in Zn. This situation is clearly revealed by the spatial correlation of the global distribution of laterites, cratons (Africa, India, South America and Australia) and known regions of Zn deficient soils that result in health problems for humans whose diet is derived from such land. We also investigate whether this elemental depletion of Zn is accompanied by isotope fractionation. In the saprolitic horizons of both weathering profiles, compositions of delta Zn-66(JMC-Lyon) lie within the ‚Äúcrustal average‚ÄĚ of + 0.27 +/- 0.07% delta Zn-66(JMC-Lyon). By contrast, soil horizons enriched in secondary oxides show lighter isotope compositions. The isotopic signature of Zn (Delta Zn-66(sample-protolith) up to similar to -0.65 parts per thousand) during the formation of the ferruginous-lateritic weathering profile likely resulted from a combination of biotically-and kinetically-controlled sorption reactions on Fe-oxyhydroxides. Our findings suggest that oxide rich soil types/horizons in (sub)-tropical regions likely exert a control on riverine Zn isotope compositions such that these becomeheavier than the crustal average. This isotopic behaviour invites a broader study of global soils to test whether light isotope composition alone could serve as an indicator for reduced bioavailability of Zn. (C) 2017 Elsevier B.V. All rights reserved
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