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Adina-Laura Lazăr Călin Baciu Carmen Roba Tiberius Dicu Cristian Pop Călin Rogozan Cristina Dobrotă 《Environmental Earth Sciences》2014,72(11):4653-4666
The paper presents the results of a combined soil and vegetation survey in Ro?ia Montan? mining area (western Romania), famous for its gold and silver deposits, extensively exploited over the last 2,000 years. As the ore extraction has ceased in 2006 and new operations could be initiated in the future, the study contributes to the definition of the environmental baseline. Samples of topsoil and leaves of the tree species Betula pendula and Carpinus betulus have been collected from the inside and outside of the mining area, on a total surface of more than 60 km2. The pH and heavy metal concentrations (Cd, Cr, Cu, Ni, Pb, and Zn) have been measured on 262 soils/sediments samples, revealing the predominantly acidic character of soils and the generally low contents of heavy metals. Stronger acidity and higher contents of heavy metals have been noticed in the proximity of the mining site, on the tailings and waste rock dumps, and along the streams with acid water. More than 100 leaf samples have been analysed for the same heavy metals as soils and also for chlorophyll fluorescence and pigment concentrations. B. pendula has shown a particular ability to concentrate Zn in leaves, at levels that may greatly exceed the Zn content in the corresponding soil samples. The correlation between the heavy metal contents in leaves and in soils, in most of the cases, is not very strong, presumably in relation to the low concentrations in soils. The chlorophyll concentration in leaves of B. pendula slightly diminishes on soils with low pH. 相似文献
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Summary This paper promotes a GIS-based method that allows the visualization, the identification and the qualitative assessment of relationships existing among a limitless number of climatological variables. We use a variety of precipitation variables from fourteen Romanian weather stations to demonstrate the techniques and discuss its benefits and limitations. 相似文献
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Gas flux measurements have for the first time been taken from vents and soil of eastern Romania mud volcanoes, the largest geological structures in Europe releasing methane into the atmosphere. In the quiescent phase, the methane emission from single vents is up to 28 t yr?1. Diffuse soil microseepage is of the order of 102?105 mg m?2 day?1. A total output of at least 1200 tonnes of CH4 per year can be conservatively estimated over the area investigated alone (～ 2.3 km2). Helium fluxes are up to five orders of magnitude higher than the average flux in a stable continental area, pointing to a close link between mud volcanoes and crustal degassing through faults crossing the deep hydrocarbon reservoirs. These data represent a key contribution towards refining global CH4‐emission estimates, which indicate mud volcanoes as a significant and unavoidable source of greenhouse gases for the atmosphere. 相似文献
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Viorel Badescu Christian A. Gueymard Sorin Cheval Cristian Oprea Madalina Baciu Alexandru Dumitrescu Flavius Iacobescu Ioan Milos Costel Rada 《Theoretical and Applied Climatology》2013,111(3-4):379-399
Fifty-four broadband models for computation of solar diffuse irradiation on horizontal surface were tested in Romania (South-Eastern Europe). The input data consist of surface meteorological data, column integrated data, and data derived from satellite measurements. The testing procedure is performed in 21 stages intended to provide information about the sensitivity of the models to various sets of input data. There is no model to be ranked “the best” for all sets of input data. However, some of the models performed better than others, in the sense that they were ranked among the best for most of the testing stages. The best models for solar diffuse radiation computation are, on equal footing, ASHRAE 2005 model (ASHRAE 2005) and King model (King and Buckius, Solar Energy 22:297–301, 1979). The second best model is MAC model (Davies, Bound Layer Meteor 9:33–52, 1975). Details about the performance of each model in the 21 testing stages are found in the Electronic Supplementary Material. 相似文献
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Methane (CH4) in terrestrial environments, whether microbial, thermogenic, or abiogenic, exhibits a large variance in C and H stable isotope ratios due to primary processes of formation. Isotopic variability can be broadened through secondary, post-genetic processes, such as mixing and isotopic fractionation by oxidation. The highest and lowest 13C and 2H (or D, deuterium) concentrations in CH4 found in various geologic environments to date, are defined as “natural” terrestrial extremes. We have discovered a new extreme in a natural gas seep with values of deuterium concentrations, δDCH4, up to + 124‰ that far exceed those reported for any terrestrial gas. The gas, seeping from the small Homorod mud volcano in Transylvania (Romania), also has extremely high concentrations of nitrogen (> 92 vol.%) and helium (up to 1.4 vol.%). Carbon isotopes in CH4, C2H6 and CO2, and nitrogen isotopes in N2 indicate a primary organic sedimentary origin for the gas (a minor mantle component is suggested by the 3He/4He ratio, R/Ra ~ 0.39). Both thermogenic gas formation modeling and Rayleigh fractionation modeling suggest that the extreme deuterium enrichment could be explained by an oxidation process characterised by a δDCH4 and δ13CCH4 enrichment ratio (ΔH/ΔC) of about 20, and may be accounted for by abiogenic oxidation mediated by metal oxides. All favourable conditions for such a process exist in the Homorod area, where increased heat flow during Pliocene–Quaternary volcanism may have played a key role. Finally we observed rapid variations (within 1 h) in C and H isotope ratios of CH4, and in the H2S concentrations which are likely caused by mixing of the deep oxidized CH4–N2–H2S–He rich gas with a microbial methane generated in the mud pool of one of the seeps.We hypothesize that the unusual features of Homorod gas can be the result of a rare combination of factors induced by the proximity of sedimentary organic matter, mafic, metal-rich volcanic rocks and salt diapirs, leading to the following processes: a) primary thermogenic generation of gas at temperatures between 130 and 175 °C; b) secondary alteration through abiogenic oxidation, likely triggered by the Neogene–Quaternary volcanism of the eastern Transylvanian margin; and c) mixing at the surface with microbial methane that formed through fermentation in the mud volcano water pool. The Homorod gas seep is a rare example that demonstrates how post-genetic processes can produce extreme gas isotope signatures (thus far only theorized), and that extremely positive δDCH4 values cannot be used to unambiguously distinguish between biotic and abiotic origin. 相似文献
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A global database of gas composition and methane stable isotopes of 143 terrestrial mud volcanoes from 12 countries and 60 seeps independent from mud volcanism from eight countries, was compiled and examined in order to provide the first worldwide statistics on the origin of methane seeping at the earth's surface. Sixteen seep data were coupled with their associated subsurface reservoirs. 相似文献
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Synthetic pyrite crystals doped with As, Co, or Ni, undoped pyrite, and natural arsenian pyrite from Leadville, Colorado were investigated with electrochemical techniques and solid-state measurements of semiconducting properties to determine the effect of impurity content on pyrite’s oxidation behavior. Potential step experiments, cyclic voltammetry, and AC voltammetry were performed in a standard three-electrode electrochemical cell setup. A pH 1.78 sulfuric acid solution containing 1 mM ferric iron, open to atmospheric oxygen, was chosen to approximate water affected by acid drainage. Van der Pauw/Hall effect measurements determined resistivity, carrier concentration and carrier mobility.The anodic dissolution of pyrite and the reduction of ferric iron half-reactions are taken as proxies for natural pyrite oxidation. Pyrite containing no impurities is least reactive. Pyrite with As is more reactive than pyrite with either Ni or Co despite lower dopant concentration. As, Co, and Ni impurities introduce bulk defect states at different energy levels within the band gap. Higher reactivity of impure pyrite suggests that introduced defect levels lead to higher density of occupied surface states at the solid-solution interface and increased metallic behavior. The current density generated from potential step experiments increased with increasing As concentration. The higher reactivity of As-doped pyrite may be related to p-type conductivity and corrosion by holes. The results of this study suggest that considering the impurity content of pyrite in mining waste may lead to more accurate risk assessment of acid producing potential. 相似文献
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Madalina N. Frinculeasa Alin P. Frinculeasa Cornel David 《Studia Geophysica et Geodaetica》2014,58(2):289-301
The Roman fort from Sfârleanca is one of the most representative archaeological sites dating from the Roman period (2nd century A.D.) in Northern Muntenia. The existing natural and anthropic features of the environment required the application of geophysical methods in order to outline the spatial pattern of the buried remains, to define the geometry of the anthropogenic settlements and to obtain detailed information about different archaeological materials without digging. During the survey, two different geophysical methods have been employed: total magnetic field measurements and electrical resistance mapping using Twin-probe array. The instrument consists of GSM19W Overhauser magnetometers with GPS, in base-rover system, and a twin-probe array LGM 4-Point light hp. The measurements were used to draw primary maps of the physical parameters (total magnetic field strength/intensity, electrical resistance), and also processed maps (filtering, derivative). The magnetic results obtained by interpreting the anomalies yielded information about the limits of the fort, about the internal organization of the military structure (its axial road, partially its secondary road, the localization and the shape of its constructions) and at the bath and heating installation. A previously unknown element is the possible water supply pipe made of ceramic material highlighted by the mathematical modelling of the data obtained by the magnetic investigations. Electrical resistance results provide complementary information to the magnetic survey concerning the limits of the baths and the remains of the fort structure. This paper brings to light geophysical investigations into this Roman fort and baths, extending the picture produced by previous archaeological excavations that only dealt with a small part of the site. It indicates the importance of using geophysical methods in preliminary archaeological research and the advantages of combining total magnetic field measurements and electrical resistance mapping when investigating an archaeological site characterized by a number of environmental difficulties. 相似文献
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