Reduction of Fe(III)(hydro)oxides to green rust in soils results increasing dissolved iron conten... more Reduction of Fe(III)(hydro)oxides to green rust in soils results increasing dissolved iron content in the pore water. This process is controlled by oxidation/reduction status. However, the Eh-pH threshold is known, scientific papers publish various values. One of the most comprehensive source is the „Atlas of Eh-pH diagrams” (Takeno, 2005) which includes a comparison of several thermodynamic databases. Some field researches support (Glasby and Schultz, 1999) these calculations, whereas others publish different results (Lemos et al., 2007). Differences can be explained by the different environmental conditions (lateritic soil vs. seawater conditions). Our research group has focused on these differences (Szalai, 2008). Two group of sampling wells and Eh-pH monitoring systems were installed in two wetlands: a hilly headwater wetland (Geresdi-dombság, Hungary) on silt parent material, and a plain wetland (Danube-Tisza Interfluve, Hungary) on sandy parent material. Headwater wetland is a...
Rhodochrosite concretions with fish and plant fossils occur in the Urkut manganese carbonate depo... more Rhodochrosite concretions with fish and plant fossils occur in the Urkut manganese carbonate deposit (Jurassic) and were investigated for mineralogy and geochemistry. These concretions are mainly composed of rhodochrosite and Mn-bearing calcite, but X-ray diffraction and electron microprobe analysis showed also the presence of Ca-rich kutnohorite. Cathodoluminescence microscopy revealed kutnohorite as luminescent mineral as infiltration and veinlets suggesting early diagenetic origin. Chrysotile needles were also detected in one of the kutnohorite veinlets by transmission electron microscopy. Stable C and O isotope results showed low-T very early diagenetic, bacterially mediated decomposition of organic matter and formation of Mn-carbonate in the ore section, which effect was the strongest around the organic remnants. Compared to the polarized light microscopy, cathodoluminescence microscopy was able to give visible picture about the texture of the very fine-grained Mn-carbonate con...
Sideritic-kaolinitic and green clay layers were previously reported from the Mecsek Mountains (SW... more Sideritic-kaolinitic and green clay layers were previously reported from the Mecsek Mountains (SW Hungary) as indicators of Tethyan volcanism in the otherwise germanotype Middle Triassic succession. The aim of the present study is to provide a review and a critical re-evaluation of the previously published data on both the sideritic-kaolinitic layers (the so-called "Mánfa Siderite") and the green clay layers. New results of mineralogical investigation of the green clay layers are also presented. The Middle Triassic volcanic origin of the "Mánfa Siderite" cannot be confirmed. In addition to a possible volcanic contribution, the sideritic-kaolinitic layers were probably formed in a freshwater swamp under humid, tropical climatic conditions, whereby weathering in an organic-rich, acidic environment led to the formation of "underclays" and siderite in the coal-bearing formations of Late Triassic to Early Jurassic age. These layers were probably tectonically placed over Middle Triassic carbonates. The illitic green clay layers intercalated in the Middle Triassic dolostone may represent terrigenous deposits, and the illite mineralogy probably is the result of burial diagenesis of detrital clays.
Toarcian black shale that hosts Mn-carbonate microbialites at Úrkút, Hungary was investigated by ... more Toarcian black shale that hosts Mn-carbonate microbialites at Úrkút, Hungary was investigated by mineralogical, inorganic, and organic geochemical methods for characterization and comparison with other European black shales representative of the Toarcian Oceanic Anoxic Event. Based on the authigenic mineral composition, calculations were made to estimate environmental conditions during sediment accumulation and early diagenesis. Geochemical and petrographical results of organic, carbonate, and REE multiple-proxy analyses revealed a strong congruence between the host black shale and the Mn-carbonate ore beds. The Úrkút black shale is really a grey shale with moderate to low TOC content that accumulated in a starved basin. The organic matter content and anoxic characteristics resulted from rapid accumulation of microbial organic matter from microbial booms, accompanied by a geothermally generated hydrothermal circulation system, and a high rate of authigenic mineral formation (clay minerals and proto-ore minerals). The inferred enzymatic Mn and Fe oxidation blocked carbonate formation by decreasing the pH. The system remained suboxic via syngenetic mineral accumulation (Fe-rich biomats), and became anoxic during diagenesis in conjunction with pyrite generation. The separation of black shale beds and Mn-ore beds is not distinct through the section. Instead, a distal hydrothermally induced clay-rich authigenic assemblage (marlstone) best describes the black shale, in which Mn-oxide proto-ore beds (Mn-rich laminae) formed from the beginning of black shale deposition, when the oxygen supply in the sedimentary basin was insufficient for enzymatic Mn(II) oxidation. Mn-oxide proto-ore turned into Mn-carbonate ore via microbially mediated processes during early diagenesis. The drivers for Mn-bearing organic matter-rich marlstones were most probably a combination of regional and local processes, with generation of a tectonic rift system that promoted geothermally generated hydrothermal fluids, which initiated microbial blooms. Black shale mineralogy, geochemistry, and organic matter at Úrkút differ from those of the epicontinental shelf black shales of the Tethyan ocean.
Boda Claystone Formation (BCF) is the host rock of the planned site for high level nuclear waste ... more Boda Claystone Formation (BCF) is the host rock of the planned site for high level nuclear waste repository inHungary. Samples representing the dominant rock types of BCF were studied: albitic claystone, claystone with high illite content, and analcime bearing claystone. Clay minerals in these three rock types were characterized by Xray powder diffraction (XRD), transmission electron microscopy (TEM) and thermal analysis (DTA-TG), and the results were discussed from the point of view of the radionuclide sorption properties being studied in the future. Mineral compositions of bulk BCF samples vary in wide ranges. In the albitic sample, besides the dominant illite, few percent of chlorite represents the layer silicates in the clay fraction. Illite is the dominating phase in the illitic sample, with a few percent of chlorite. HRTEM study revealed that the thickness of illite particles rarely reaches 10 layers, usually are of 5-6 TOT layer thick. Illite crystals are generally thicker in...
The issue of diagenetic alteration of carbonate deposits in caves (speleothems) has gained increa... more The issue of diagenetic alteration of carbonate deposits in caves (speleothems) has gained increasing importance in recent years, as this process has serious consequences for speleothembased paleoclimate studies. In this study stable hydrogen and oxygen isotope data of water trapped in fluid inclusions were collected for recently forming stalagmites and flowstones in order to determine how dripwater compositions are reflected and preserved in the inclusion water compositions. Hydrogen isotope compositions were found to reflect dripwater values, whereas the oxygen isotope data were increasingly shifted from the local dripwater compositions with the time elapsed after deposition. The δ 18 O data are correlated with X-Ray diffraction full width at half maximum values (related to crystal domain size and lattice strain), suggesting that the oxygen isotope shift is related to recrystallization of calcite. Transmission electron microscope analyses detected the presence of nanocrystalline (<50 nm) calcite, whose crystallization to coarser-grained calcite crystals (>200 nm) may have induced re-equilibration between the carbonate and the trapped inclusion water. The Ostwald ripening process provides an explanation for unexpectedly low oxygen isotope compositions in the inclusion water. The detected diagenetic alteration and its isotopic effects should be taken into consideration during sampling strategies and data evaluation as speleothems containing nanocrystalline calcite during their deposition are prone to late-stage oxygen isotope water-carbonate re-equilibration, which may shift the oxygen isotope composition of the inclusion water to more depleted values while the hydrogen isotope composition remains intact.
Variable cryptocrystalline silica varieties occur en masse in the fractures and cavities of the a... more Variable cryptocrystalline silica varieties occur en masse in the fractures and cavities of the andesite host rock, showing different genetic and morphological features of variable microbial activity. Four types of CL features characterized silica phases. Raman spectroscopy supported variable amorphous carbon phases in inhomogenous distribution.
We studied the degree and distribution of traffic induced pollution at a 40 m high building at th... more We studied the degree and distribution of traffic induced pollution at a 40 m high building at the side of a major road in Budapest by making magnetic, mineralogical and geochemical analysis on settled dust samples collected at different levels and at the front and back sides of the building. We observed strong seasonal dependence of the amounts of anthropogenic pollutants, which were highest during summer. This season was also characterized by strong vertical variation of the amounts of dust, of the magnetic susceptibilities (reflecting best the traffic induced pollution) and of the concentrations of Pb. All these have maximum values at 9 m, on both sides of the building. The pattern of the distribution does not correspond to what is predicted by an air flow model published for high buildings with similar morphology and wind conditions.
Finely laminated sediment records have been studied from a small landslide-dammed lake (Bol at au... more Finely laminated sediment records have been studied from a small landslide-dammed lake (Bol at au) located in Bukovina, Romania. An age-depth model for the Bol at au sediment record was established based on 8 AMS radiocarbon dates from terrestrial macrofossils and the double peaks of the 137 Cs flux (i.e. mid-1960s: global fallout maximum; 1986: Chernobyl accident). The onset of the lacustrine sedimentation is estimated to~5e6.5 ka while the landslide event can be constrained by~6.8e7 ka as an inferior age estimate. The laminated structure is interpreted as organic and clastic type varvite at the lower and upper part of the core, respectively. Major fluctuations found in the coarsely sampled (5 cm) stable carbon isotope data showed remarkable correspondence with nearby palynological records and a lacustrine d 13 C record. It suggests that the sediment record preserves environmental signals with a broader regional relevance. The established timescale provides the necessary chronological basis of the records from Lake Bol at au for further analysis.
We collected urban dust during two years, on seasonal basis, in 8 standard sampling pots with con... more We collected urban dust during two years, on seasonal basis, in 8 standard sampling pots with continuous supply of distilled water, placed at 2, 9, 21 and 33 m, on the front and back sides, respectively, on a 40 m high building. After the vacuum filtering and air-drying of the samples, magnetic measurements, mineralogical and geochemical analysis were carried out on them as well as on car exhaust filters. Then remarkably similar magnetic properties of the settled dust and the exhaust filters suggested that the anthropogenic contribution to the dust is traffic induced. The traffic induced pollution is best reflected in the apparent susceptibilities of the samples, which show a strong seasonal dependence. The settled dust has the highest values of apparent susceptibilities, the highest amounts of dust and the highest concentrations of Pb during summer. The bulk mineral composition of the dust also depends on the season, since the dust becomes enriched in dolomite, coming from a hill b...
Knowledge of the distribution and sorption characteristics of trace metals in soils is essential ... more Knowledge of the distribution and sorption characteristics of trace metals in soils is essential because of their importance both from agricultural and environmental point of view. In this paper, an overview will be provided on the relationship between the behavior and sorption properties of Cu and Pb as well as major soil characteristics, based on the results obtained by several independent research projects carried out on this field at the Institute for Geological and Geochemical Research over the last 15 years. These projects were accomplished using methods with different approaches, e.g. studying metal characteristics by total metal content, selective chemical extractions and batch sorption experiments. Our results show that both metals can be found in soils, primarily in the form of phases highly resistant to weathering. However, if they are mobilized, they are easily and strongly immobilized by soils rich in organic matter, with higher affinity for Cu than for Pb. In acid soils, on the other hand, the leaching of Cu is expected to be higher from such horizons when compared to Pb, especially when iron oxides, which immobilize Pb preferentially, are also present in these horizons. In mineral horizons the close association of Pb and iron oxides can be still expected, whereas Cu prefers to be bound both by clay minerals and iron oxides. In alkaline soils, however, precipitation of both metals as carbonates is a general feature. Our results obtained through different approaches presented in this paper were found to be effectively complementary to each other, providing a much deeper insight into soil-metal interaction than when they are used independently.
The mineralogy, geochemistry and magnetic properties of total suspended particulate (TSP) matter ... more The mineralogy, geochemistry and magnetic properties of total suspended particulate (TSP) matter in Budapest, Hungary were studied to identify their heavy metal-bearing mineral phases. Amorphous organic matter, magnetite, salts as well as mineral phases characteristic of the surrounding geology are the main components of the TSP. They show significant enrichment in several heavy metals, such as Zn (up to 19 046 mg/kg), Pb (up to 3597 mg/kg), Cu (up to 699 mg/kg) and Mo (up to 53 mg/kg). The most frequent heavy metal-bearing mineral phases are spherular or xenomorphic magnetite particles containing 2-3 wt% Pb and Zn. They often form aggregates and are closely associated with soot and/or clay minerals. The size of these particles is rarely below 30 nm. Cu and Mo could be associated to magnetite too. Clay minerals and mica particles may also contain significant amount of Zn (up to 5wt%). Additionally, ZnO and ZnCO 3 particles were found in the sample with highest Zn content and our data suggest the potential association of Pb and carbonates, as well. Magnetite particles are resistant to weathering releasing its toxic components slowly to the environment, while layer silicates (and carbonates) may be the potential source of mobile toxic metals in the TSP.
Kivonat Az ülepedő porok jelentős hatással lehetnek a levegőminőségre, amelyben szemcseméretüknek... more Kivonat Az ülepedő porok jelentős hatással lehetnek a levegőminőségre, amelyben szemcseméretüknek és ásványos összetételüknek komoly szerepe van. Budapest egyik legforgalmasabb útja mentén álló toronyépület két oldalán, négy különböző magasságban, évszakonként gyűjtött ülepedő porok ásványos-és szemcseösszetételét vizsgáltuk. A minták szemcseeloszlására két csúcs jellemző (12 és 37 m körül). A finomabb szemcsék aránya, de a maximális szemcseméret is a szélfelőli oldalon nagyobb. Jellegzetes vertikális eloszlási trend nem fedezhető fel, viszont nyáron a durvább szemcsék arányának növekedése jellemző. A fő ásványos alkotók a mintázási hely környezetének földtani jellemzőit tükrözik. A finom szemcsefrakcióban (<20 m) az agyagásványok és az amorf anyag aránya jelentősen nő, és megjelenik az épület anyagából származtatható gipsz is. Az épület két oldala közti legnagyobb különbség a dolomit mennyiségében mutatkozott, ami az épület mögötti hegyről érkezik, és a speciális légáramlási viszonyoknak köszönhetően az utcafronton mutat nagyobb értékeket. A karbonát-és agyagásványok aránya nyáron jelentősen nő a kvarc rovására, ami a száraz felszínnel jellemzett időszakokat uraló porfelkavarodásnak tudható be. Az ásványos összetétel vertikális változása az agyagásványok esetén a legszembetűnőbb, és jól mutatja a kis szemcseméretű fázisokra jellemző kettős, helyi és távolabbi forrásokból is származó ülepedés egymással ellentétes hatását.
Soil porosity increase on arable fields is mainly the result of cultivation while sealing and cru... more Soil porosity increase on arable fields is mainly the result of cultivation while sealing and crusting are natural processes. The first is a rapid change the latter is slower, however, little is known about the time scale of soil sealing and crusting. Crusting rainfall simulation experiments were carried out to investigate the role of single rainfall events on soil sealing and crusting, on an intensively cultivated arable field. To follow porosity changes trough out the year, undisturbed samples were analyzed. High seasonal differences were identified in bulk density and porosity during the vegetation period that appeared to be the results of tillage. The results of rainfall simulation underline the rapid influence of a single storm in sealing and crusting of a Cambisol by decreasing the final infiltration rate and increasing runoff and sediment load. Porosity reduction manifested first of all in surface crust formation, however, kaolinite was the dominating cay mineral in the investigated Cambisol. Bulk density of the tilled soil layer enhanced by 15% in case of structural and 40% in erosion crust. The higher value could be the result of the continuous deposition according to Stoke's law creating a clay film cover on the surface. The sealing and crusting effect of a single storm could be of the same order as the influence of tillage on soil porosity runoff and soil loss. The porosity created by tillage can collapse during one precipitation event.
Spatial diversity of landscapes results in spatial and temporal heterogeneity of soil physical an... more Spatial diversity of landscapes results in spatial and temporal heterogeneity of soil physical and soil chemical parameters. These diversities of pH and E H may cause spatial and temporal diff erences of dissolved macro-and microelements between ecotopes. The present paper focuses on the relationship between vegetation induced landscape patt erns and the spatial and temporal diversities of soil physical and chemical parameters. We supposed
In this study we report the first hydrogen isotope composition analyses on carbonado diamond alon... more In this study we report the first hydrogen isotope composition analyses on carbonado diamond along with cathodoluminescence and scanning electron microscopic imaging, electron microprobe analyses, and stable (H and C) and radiogenic (Sr) isotope measurements. The hydrogen of bulk carbonado (consisting diamond and pore-filling minerals) yielded ~-4‰, consistent with usual crustal or mantle-derived fluids. The diamond-related hydrogen component is about 70 ± 30 ppm and shows a D-depletion down to-200‰. Determined H isotope values-together with C isotope compositions-overlap the ranges for mantle-derived hydrocarbons. Textural characteristics and Sr isotope ratios of pore-filling florencite indicate that the carbonado was formed in a fluid-rich environment, underwent a significant high-temperature influence and finally suffered thorough alteration. Based on these observations, a terrestrial formation during interaction of mantle rocks/melts or subducted crustal materials and reduced C-H fluids seems to be more plausible than an extraterrestrial origin.
Highlights-Manganese carbonate microbialites are explicable by a two-step microbial formation mod... more Highlights-Manganese carbonate microbialites are explicable by a two-step microbial formation model-Úrkút Mn-carbonate ores bear strong similarities to Molango (Upper Jurassic, Mexico) and Tao Jiang (Middle Ordovician, China).-Mn, δ 34 S values, and trace metals point to the effects of distal hydrothermal fluid sources *Highlights (for review)
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