Viktor Goliáš

Identifying century-old long-spined Daphnia: species replacement in a mountain lake characterised by paleogenetic methods

Mountain lakes often harbour morphologically or genetically unique populations of zooplankton species, including cladocerans. Daphnia lacustris Sars, predominantly found in Fennoscandia but also known from two Central European lakes in the Tatra Mountains, is one of such taxa. This Daphnia species often forms morphotypes with extremely long tailspines. Historical literature from a century ago documented similar morphs from another lake in the Tatra mountain range, presently inhabited by the phenotypically very different D. galeata. Using a paleogenetic approach (partial sequencing of the mitochondrial gene for 12S rRNA from preserved ephippial eggs in the lake sediment), we tested the hypothesis that Daphnia species composition changed in the lake due to anthropogenic disturbances, and that long-spined morphs were actually another relict population of currently extinct D. lacustris. Ephippia with extremely long spines were successfully retrieved from sediment cores. Despite being morphologically very well preserved, intact eggs were found in less than 2% of analysed ephippia. Genetic analyses, benefiting in most cases from amplification of short 12S fragments using internal primers, proved that long-spined ephippia belonged to D. longispina, which apparently coexisted with D. galeata in the mid-twentieth century. Our results confirm that paleogenetic methods are useful for studying the recent population structures of zooplankton species forming dormant egg banks but lacking reliably identifiable remains in sediments, and show that the extreme development of tailspines in mountain-lake Daphnia is associated with as-yet unclear environmental factors rather than taxonomic status.

Hakite from Příbram, Czech Republic: compositional variability, crystal structure and the role in Se mineralization

Abstract Hakite, ideally Cu10Hg2Sb4Se13, is a Se-dominant member of the tetrahedrite group occurring at only a few localities in the World. A new occurrence of this mineral in the Pribram uranium and base-metal ore district, Central Bohemia, Czechia, is reported in this paper. Hakite was found to be locally abundant and was identified in several samples with Se mineralization. Three chemically distinct types of hakite were distinguished based on electron microprobe study, Hg-rich hakite (hakite sensu stricto), Zn-rich hakite and Cd-rich hakite. Hg-hakite dominates among the samples studied. Its average empirical formula based on 29 apfu (n = 54) is (Cu5.61Ag0.39)∑6.00Cu400(Hg1.61Zn0.20Cu0.19Cd0.15Fe0.04)∑2.19(Sb3.85As0.28)∑4.13(Se11.55S1.14)∑12.69. Less common is the Zn-hakite, (Cu5.80Ag0.20)∑6.00Cu4.00(Zn1.33Hg0.42Cd0.22Cu0.18Fe0.01)∑2.16(Sb3.85 As0.26)∑4.11(Se10.92S1.81)∑12.73(n = 22), and rare Cd-hakite has an empirical formula (n = 7) of (Cu5.84 Ag0.16)∑6.00Cu4.00(Cd1.27Zn0.60Cu0.10Hg0.07Fe0.02)∑2.06(Sb4.00As0.19)∑4.19(Se12.14S0.61)∑12.75. The refined unit cell of Hg-hakite from Příbram, obtained from powder X-ray diffraction data, is a = 10.8783(3) Å with V= 1287.3(1) Å3 (Z= 4, for the cubic space group I4̅3m). Structure refinement from the precession electron diffraction data collected on the transmission electron microscope (R = 24.4% for 424 observed reflections), confirmed that hakite is isostructural with tetrahedrite. The evolution of hydrothermal fluids, from which Se mineralization formed, suggests a distinct enrichment in sulfur and depletion in selenium over the time span of crystallization.

Widenmannite, a rare uranyl lead carbonate: occurrence, formation and characterization

Abstract The rare uranyl lead carbonate widenmannite, Pb2(UO2)(CO3)3, was found at the Jánská vein, Příbram, Czech Republic, where two generations occur in several morphological types and mineral associations in hydrothermal veins. Alpha spectroscopy shows that these two generations have different ages, >220,000 and 118±12 y. ICP-MS analysis indicates that both widenmannites have a dominance of non-radiogenic Pb which originates from weathered galena. The older widenmannite I forms fine-grained, grey to beige aggregates in the highly altered supergene part of the hydrothermal ore vein in association with pyromorphite, cerussite and goethite. The younger widenmannite II occurs as white, yellow or greenish-yellow thin tabular crystals up to 0.5 mm long in association with cerussite, anglesite, limonite, kasolite and an unnamed Pb-U-O phase. Thermal analysis suggests that widenmannite decomposes in several steps, with Pb uranate as the final product. Infrared and Raman spectroscopy confirm the presence of non-equivalent (CO3)2- groups, bidentately coordinated in uranyl hexagonal polyhedra, forming the well known uranyl tricarbonate complex. Infrared spectroscopy shows conclusively that widenmannite does not contain molecular H2O.

Alteration halos around radioactive minerals in plutonic and metamorphic rocks of the northern Moldanubian area, Bohemian massif

Effects of strongly radioactive primary minerals (mainly monazite) on the surroundings are compared in various rocks of similar chemical and mineral composition (mainly granites and paragneisses) of the Moldanubian area in the Bohemian massif. All these rocks cooled to The halos of secondary phases most commonly occur around monazite in cordierite, but also in plagioclase and in quartz. It is unimportant if the monazite is included in one mineral grain or is located at grain boundaries. Compared to previous studies in similar rocks with similar cooling ages ( e.g. , in Erzgebirge and Massif Central, as documented in literature), quartz was destroyed relatively easily. In most cases the alteration of primary minerals close to radioactive grains cannot be explained in a conservative way that the radiation damage only helps to precipitation of secondary phases during a “ubiquitous” fluid alteration. It seems that the radioactivity promotes reactions of the primary minerals with fluid (fluid inclusions and H 2 O in channels of the cordierite structure) even at “static” conditions. The volume changes (caused by hydration or amorphization) make easier a later import of external fluid. The reason why these phenomena are observed in some regions and not in very similar rocks in other regions is not understood yet, but it is likely that the rocks of the Moldanubian area are mostly above-averagely rich in aqueous fluids. The frequent association of monazite with hydrated secondary phases may contribute significantly to resetting monazite ages during metamorphism and partial melting. In addition, the neglecting of the chemical transformation of the nuclear energy for the calculations of radioactive heat production and heat budgets of rocks is questioned.

Radiation damage in sulfides: Radioactive galena from burning heaps, after coal mining in the Lower Silesian basin (Czech Republic)

Abstract The isotopic composition of lead (207Pb/206Pb, 208Pb/206Pb, and 210Pb) in a recently formed galena from burning heaps after coal mining in Radvanice, Markoušovice, and Rybníček, the Lower Silesian basin, Czech Republic, was studied in detail. 210Pb activity in galena varied from 135 ± 9 to 714 ± 22 Bq/g and calculated integral doses ranged from 2.21 × 1011 to 6.11 × 1011 α/g. The radioactivity of the galena causes micro-deformations in its crystal structure as indicated by the Williamson-Hall graphs, showing that the level of micro-strain depends on the length of time that galena samples were exposed to the radiation. However, the crystal structure of galena is affected very inhomogenously; according to TEM investigations there are domains of fully crystalline, polycrystalline, and fully metamict galena within one crystal. Inductively coupled plasma-mass spectrometry (ICP-MS) was used to determine the isotopic composition of the studied galena. The stable isotope ratios of Pb varied for 207Pb/206Pb from 0.8402 to 0.8435 and for 208Pb/206Pb from 2.0663 to 2.0836. The average ratios 207Pb/206Pb = 0.8312 and 208Pb/206Pb = 2.0421 were obtained for coal from the same localities. These isotope ratios show that there is no isotopic fractionation taking place during the coal burning and subsequent galena crystallization from hot gases.

Uranium glasses: the experimental leaching compared to the long-term natural corrosion

Corroded surface layers were formed naturally on the historical uranium-coloured glasses. Comparative batch leaching test was performed in laboratory and the glass dissolution rates with respect to main components including uranium were established. The residual alkali-leached surface corrosion layers even of experimental or natural origin showed the stable concentration of uranium.