Temperature-time dependence of the electrical conductivity of garnets

aam mam uu mn¶rt;muaamuu n¶rt; u u nua ua —aam auumu m mnam (200–1000°, ₂ 10^–1 a). aa¶rt;u, m um na¶rt;a uu a n¶rt;u auumu mn¶rt;mu m mnam, u¶rt;m auumu ¶rt;a mn¶rt;mu mnam u n¶rt;m mu mnam uma.     

Sudden ionospheric disturbances and flare activity in the course of the solar cycle no 20

a¶rt;a ma nu an u u (SID) u nu n a (a n¶rt; au) mu 1965–1975 . u u SID na¶rt;am nau, mum u nm R.     

The economics of decarbonizing the energy system—results and insights from the RECIPE model intercomparison

This paper synthesizes the results from the model intercomparison exercise among regionalized global energy-economy models conducted in the context of the RECIPE project. The economic adjustment effects of long-term climate policy are investigated based on the cross-comparison of the intertemporal optimization models ReMIND-R and WITCH as well as the recursive dynamic computable general equilibrium model IMACLIM-R. A number of robust findings emerge. If the international community takes immediate action to mitigate climate change, the costs of stabilizing atmospheric CO₂ concentrations at 450?ppm (roughly 530?C550?ppm-e) discounted at 3% are estimated to be 1.4% or lower of global consumption over the twenty-first century. Second best settings with either a delay in climate policy or restrictions to the deployment of low-carbon technologies can result in substantial increases of mitigation costs. A delay of global climate policy until 2030 would render the 450?ppm target unachievable. Renewables and CCS are found to be the most critical mitigation technologies, and all models project a rapid switch of investments away from freely emitting energy conversion technologies towards renewables, CCS and nuclear. Concerning end use sectors, the models consistently show an almost full scale decarbonization of the electricity sector by the middle of the twenty-first century, while the decarbonization of non-electric energy demand, in particular in the transport sector remains incomplete in all mitigation scenarios. The results suggest that assumptions about low-carbon alternatives for non-electric energy demand are of key importance for the costs and achievability of very low stabilization scenarios.     

Clitellate worms (Annelida) in lateglacial and Holocene sedimentary DNA records from the Polar Urals and northern Norway

While there are extensive macro‐ and microfossil records of a range of plants and animals from the Quaternary, earthworms and their close relatives amongst annelids are not preserved as fossils and therefore the knowledge of their past distributions is limited. This lack of fossils means that clitellate worms (Annelida) are currently underused in palaeoecological research, even though they can provide valuable information about terrestrial and aquatic environmental conditions. Their DNA might be preserved in sediments, which offers an alternative method for detection. Here we analyse lacustrine sediments from lakes in the Polar Urals, Arctic Russia, covering the period 24 000–1300 cal. a BP, and NE Norway, covering 10 700–3300 cal. a BP, using a universal mammal 16S rDNA marker. While mammals were recorded using the marker (reindeer was detected twice in the Polar Urals core at 23 000 and 14 000 cal. a BP, and four times in the Norwegian core at 11 000 cal. a BP and between 3600–3300 cal. a BP), worm extracellular DNA ‘bycatch’ was rather high. In this paper we present the first reported worm detection from ancient DNA. Our results demonstrate that both aquatic and terrestrial clitellates can be identified in late‐Quaternary lacustrine sediments, and the ecological information retrievable from this group warrants further research with a more targeted approach.     

Enhanced geochemical gradients in a marine shallow-water hydrothermal system: Unusual arsenic speciation in horizontal and vertical pore water profiles

The shallow marine hydrothermal vents near Ambitle Island in eastern Papua New Guinea discharge hot, slightly acidic, As-rich, chemically reduced fluid into cool, slightly alkaline, oxygenated seawater. Gradients in temperature, pH, and total As (As^T), among others, are established as the two aqueous phases mix. The hydrothermal fluid contained 900 μg/L As^T, almost exclusively present as the reduced As^III, while local seawater measured between 1.2 and 2.4 μg/L As, with approximately equal levels of As^III and As^V. Of particular interest in this study was As speciation and abundance in pore waters as a function of sediment depth and as a function of distance from the area of focused venting. With increasing distance, As^T concentration in the pore water decreased rapidly, but remained elevated up to 300 m from the area of focused venting when compared to a non-hydrothermal control site. As a function of depth (to 100 cm) As^T concentration in the pore water profiles was elevated and generally increased with depth. Surprisingly, aqueous As^V far exceeded aqueous As^III at almost all distances and depths investigated, while at the control site the As^III concentration exceeded that of As^V. In the Tutum Bay hydrothermal system, chemical disequilibria among As species provide potential metabolic energy for arsenite oxidizing microorganisms where hydrothermal fluid mixes with seawater near the vent orifice, and for arsenate reducing microorganisms with increasing distance and depth from the hydrothermal point source.     

Trends and evolution of contamination in a well-dated water reservoir sedimentary archive: the Brno Dam, Moravia, Czech Republic

The sedimentary record from dams can provide important information about stratigraphy and pollution history of densely populated river basins. The Brno Dam is a small reservoir within the Morava River catchment (Czech Republic) accumulating lacustrine sediments since 1940 (dam filling). The stratigraphy of the dam sediments was studied using multiproxy stratigraphic analysis (X-ray densitometry, bulk magnetic susceptibility, diffuse spectral reflectance and cation-exchange capacity) of five sediment cores supported by ground-penetration radar sections. Concentrations of heavy metals were studied by X-ray fluorescence analysis. The thickness of the dam sediments decreases from 220 cm in the proximal part, near the feeder, to only 10 cm in the distal part, near the dyke. Sediments consist predominantly of finely-laminated silty sands, silts and clays. The sedimentation rate for the last ~22 years, inferred from ¹³⁷Cs dating, decreases from 4.2 cm per year in the proximal part of the dam to 0.29 cm per year in its distal part. Distinct long-term trends were found in the depth profiles of heavy metal concentrations. The heavy metal contents increase significantly after 1940 in all cores, with peak concentrations confined to layers deposited in the 1960s and 1980s. A decreasing trend occurred after 1989 (the decline in Czech heavy industry). The results also show that heavy metal contamination is dependent on lithology (hyperpycnal flow layers related to floods). Increased concentrations of phosphorus in the sediments indicate long-term eutrophication of the dam. Despite the recent decreasing trends in heavy metal concentrations the phosphorus contents remain high in recent years and have caused persisting problems with algal growth in the dam mentioned by previous authors.     

Persistent halogenated compounds in black guillemots (Cepphus grylle) from Greenland--levels, compound patterns and spatial trends

Twenty-seven black guillemot eggs and 39 livers were analysed for polychlorinated biphenyls (PCBs), chlorinated pesticides including chlordane-related compounds and toxaphene, and polybrominated diphenylethers (PBDEs). The samples were collected at Qeqertarsuaq (Godhavn, West Greenland) and Ittoqqortoormiit (Scoresbysund, East Greenland). The concentrations of halogenated organic compounds in samples from East Greenland were somewhat higher than the corresponding concentrations from West Greenland. Differences in compound patterns were found between West and East Greenland, with higher percentages of the heavier PCB molecules, p,p(')-DDE and alpha-HCH in the samples from Ittoqqortoormiit. Similarly, different levels and different compositions were observed for eggs and livers. The eggs had generally higher concentrations of all compounds as well as higher percentages of CHB-50, CHB-62 and alpha-HCH than liver samples from the same area. Dividing the liver samples into age groups revealed increasing concentrations with age.