The investigation of Idrija, one of the oldest mining areas in Slovenia, is an on-going field of geochemical research. Over 500years of Hg mining and ore processing resulted in widespread ...contamination, especially in soil. Past investigations showed that soil in the Idrija surroundings is seriously contaminated on a regional scale (160km2 area), mainly due to aerial emissions from an ore roasting plant in the past. This study focuses on the soil from the urban area of Idrija (3km2). Following a sampling model grid, which was developed for collection of 9 soil samples per km2, 45 sampling sites were selected and sampled. Concentrations of 10 potentially harmful elements (As, Cd, Co, Cr, Cu, Hg, Mo, Ni, Pb, Zn) were determined using aqua regia digestion. Soil samples were taken from two different depths (0–10cm and 10–20cm) in order to distinguish between possible different element sources. The results showed that only Hg concentrations were extremely high in comparison to element concentrations reported in other areas around the world, and national guidelines for soil contamination. Mercury ranges from 8 to 1210mg/kg with a median of 60mg/kg in topsoil and from 7 to 1550mg/kg, with a median of 50mg/kg in subsoil. Spatial analysis show that high Hg concentrations occur near the identified Hg sources (rocks containing Hg ore, Hg ore residue dumps and old roasting sites). High Hg concentrations cause concern, because the soil in Idrija area is often used for vegetable gardening.
•Systematic soil sampling was performed to investigate element contents•Determination of PHE concentrations in the urban soil of Idrija•Urban soil in Idrija is critically polluted with mercury•PHE, except Hg, are within representative background soil concentrations
SUMMARY
Western Slovenia is part of an actively deforming region accommodating anticlockwise rotation of Adria and its continuous collision with Eurasia. The geometry of the active faulting system in ...this plate boundary is not well defined. In this study, detailed analysis of earthquake activity was performed with relocation of earthquakes in the period between 2006 and 2017. With inspection of the waveform data, slight temporal clustering of activity was observed. To increase the detection rate of microearthquakes we used a matched filter detection algorithm method. Templates of earthquakes were created and a database of continuous waveform data within the period 2006–2017 was investigated. As a result, high temporal correlation allowed us to identify swarms and earthquake sequences that affected the active fault system in the study region.
Relocated seismicity allowed us to constrain the geometry of 5 nearly parallel faults, namely: Ravne, Idrija, Predjama, Selce and Raša faults. All these faults do have an expression in the geomorphology and reach a seismogenic depth of up to 20 km. Vertical and along strike extents of these active faults can favour earthquakes of moment magnitude equal to 7 or larger. The most recent large earthquake that occurred in this region is the 1511 earthquake with a magnitude 6.8.
The leading fault in the system being the Idrija right-lateral strike-slip fault, experiences earthquake activity from 5 to 20 km on its northern segment, while on its southern segment no earthquake activity is detected over the decade of observations. We show that the interseismic loading on the southern segment of Idrija fault is likely unclamping the locked adjacent faults promoting the observed bursts of seismicity. Moreover, in 2009 the Predjama fault accommodated a sudden increase of the surface deformation at the extensometer accompanied by a simultaneous swarm activity at its seismogenic depth. This behaviour might correspond to velocity strengthening and weakening processes taking place at both the surface and depth terminations of a locked vertical fault. These processes can be driven by a slow-slip event on the deeper part of Idrija fault that would generate a temporary acceleration of the interseismic loading rate along with a change within the fluid circulation.
This paper provides an overview of the physical and chemical landscape changes that have occurred at four reference sites due to historical mining and smelting activities within Slovenia, and their ...comparison with similar sites around the World. Literature review has been made with the intention to identify major pollutant sources, its dispersion control factors, and effects. The four reference sites are Idrija, with more than 500‐year Hg mining and ore smelting history, the Meža Valley, also with a 500‐year PbZn mining and smelting history, the Celje area where Zn was smelted for 100 years and the Drava River alluvial plain, which is contaminated because of historical PbZn mining upstream. Based on the comparison between the four abovementioned reference sites and similar sites around the world that are situated in different landscapes and climates, we identified major sources of contamination, which are the erosion of mine and ore processing wastes, and atmospheric emissions of metal‐containing particles from smelters. In the first case, major control factors are rainfall pattern and river gradient, controlling erosion and sediment deposition patterns. In the second case, the prevailing control factors are topography and the dominant wind directions.
Estimation of mercury (Hg) species fluxes in Hg contaminated rivers is crucial to predict Hg methylation in connected sediment sinks. Cinnabar (HgS) was mined and roasted for ∼500 years in the Idrija ...mining area, Slovenia, which is drained by the Idrijca River to the Gulf of Trieste (GT), Italy. Mining residues dumped into the Idrijca River caused high proportions of cinnabar in sediments, whereas soils containing high proportions of natural organic matter bound to Hg (NOM-Hg) are attributed to atmospheric Hg deposition. Previous calculations of Hg fluxes have been based on the erosion of cinnabar only, and neglected transport of NOM-Hg derived from soil. Here, we estimated NOM-Hg and cinnabar fluxes in the Idrijca River and evaluated the extent of variability under changing hydrological conditions. We estimated the discharge of NOM-Hg by Idrijca's tributaries and the importance of NOM-Hg fluxes for Hg methylation in the GT. Mass balance calculations reveal that approximately 11.2 Mg y−1 of NOM-Hg and 38.9 Mg y−1 of cinnabar are transported by the Idrijca River to the GT under median-flow conditions. In the past 520 years, a total of 53,000 tons of Hg have been released from the Idrija mining area, of which ∼32,000 tons were NOM-Hg. Under low-flow conditions, Idrijca's tributaries deliver more than 1280 kg y−1 of NOM-Hg. This study highlights the importance of Hg species analyses and their flux calculations to estimate risks of biological Hg uptake in sedimentary Hg sinks connected to Hg mining areas.
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•Hydrology influences transport of Hg species in areas surrounding former Hg mines.•Bioavailable Hg is transported under low to high-flow conditions in the Idrijca river.•Hg fluxes must be based on Hg species proportions and no solely in Hg concentrations.•Soil erosion is important for Hg cycling, in contrast to transport of river sediments in former Hg mining areas.•Tributaries supply substantial amounts of organically-bound Hg forms derived from soils.
Hg species analysis and their flux calculations allow evaluating Hg transformations downstream in former Hg mining areas which cannot be solely explained by total Hg concentrations.
Fluvial sediments of the Paglia River, a tributary of Tiber River (Central Italy), are contaminated by mercury (Hg) as a consequence of past mining activity (1846–1981, with main production ...1900–1970) in the Monte Amiata district (the 3rd largest Hg producer worldwide). In this study, we combine a geomorphological analysis with geochemical data to try and understand the influence of fluvial dynamics on the spatial distribution of Hg in fluvial sediments over a 43 km segment of the river.
By considering the evolution of the river course between 1883 and 2013, eight different geomorphic units (GUs) were recognised, including the active channel bed (baseflow channel and bar), the floodplain, and five orders of terraces. The distribution of Hg in sediments of these GUs reflects the timing of their formation with respect to evolution of the mining activity. In GUs formed before the main peak of mining activity, or after mine closure, sediments show mean Hg contents comparable to, or slightly higher than, the local background, estimated at 2–6 mg/kg; in GUs formed during the peak production, Hg mean contents are definitely higher (up to 26 mg/kg). The current floodplain also shows high contents (mean 19 mg/kg), because of continuous reworking and transport of older contaminated sediments during major flood events. Therefore, the point contaminant sources represented by mining centres evolved into a diffuse source spread over several tens of kilometres.
By combining geochemical data with calculated sediment volumes, we estimate that not less than 63 tonnes of Hg are currently contained in the sediments of the investigated river stretch. Such amount of Hg will probably limit for the near future a full land use along the Paglia–Tiber course.
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•The Paglia river catchment is affected by Hg released from the M. Amiata mining district.•Distribution of contaminants in river sediments is controlled by fluvial dynamics.•A total mass of 63 t Hg is accumulated in sediments of a 43 km-long river stretch.•This amount will pose limitations to land use in the affected area for the next decades.•Dispersion of contaminants in river sediments may change point sources into diffuse sources.
A regional geochemical survey was conducted, covering the entire territory of Slovenia. Medium-density soil sampling was performed in a 5×5km grid, mercury concentrations were analysed and a map of ...mercury spatial distribution was constructed. The determined mercury concentrations revealed an important difference between the western and the eastern parts of the country. A huge anomaly in the western part is the consequence of environmental contamination due to the 500-year history of mining and ore processing in the Idrija mercury mine and partly due to Hg containing rocks on outcrops. Slightly elevated Hg concentrations revealed in the Ljubljana-Kranj and Celje basins indicate urban pollution due to industry, traffic and the use of mercury-containing products. It was established that, besides anthropogenic impacts, lithological and climatic characteristics that determine the type of soil also influence the distribution of mercury in soils. The data were compared to a previously conducted low-density geochemical survey (sampling grid 25×25km, n=54) and to the regional geochemical data set supplemented by local high-density sampling data (irregular grid, n=2835). Comparing high-, medium- and low-sample density surveys, it was shown that higher sampling density allows the identification and characterization of anthropogenic influences on a local scale, while medium- and low-density sampling reveal general trends in the mercury spatial distribution, but are not appropriate for identifying local contamination in industrial regions and urban areas.
•Regional geochemical survey was conducted.•Hg distribution in Slovenian soils was determined.•High and low sample density surveys were compared.•A distinct Hg anomaly around Idrija area was revealed.•The variability of the spatial distribution of Hg mainly depends on pollution.
Gaseous exchanges of mercury (Hg) at the water–air interface in contaminated sites strongly influence its fate in the environment. In this study, diurnal gaseous Hg exchanges were seasonally ...evaluated by means of a floating flux chamber in two freshwater environments impacted by anthropogenic sources of Hg, specifically historical mining activity (Solkan Reservoir, Slovenia) and the chlor-alkali industry (Torviscosa dockyard, Italy), and in a pristine site, Cavazzo Lake (Italy). The highest fluxes (21.88 ± 11.55 ng m−2 h−1) were observed at Solkan, coupled with high dissolved gaseous mercury (DGM) and dissolved Hg (THgD) concentrations. Conversely, low vertical mixing and saltwater intrusion at Torviscosa limited Hg mobility through the water column, with higher Hg concentrations in the deep layer near the contaminated sediments. Consequently, both DGM and THgD in surface water were generally lower at Torviscosa than at Solkan, resulting in lower fluxes (19.01 ± 12.65 ng m−2 h−1). However, at this site, evasion may also be limited by high atmospheric Hg levels related to dispersion of emissions from the nearby chlor-alkali plant. Surprisingly, comparable fluxes (15.56 ± 12.78 ng m−2 h−1) and Hg levels in water were observed at Cavazzo, suggesting a previously unidentified Hg input (atmospheric depositions or local geology). Overall, at all sites the fluxes were higher in the summer and correlated to incident UV radiation and water temperature due to enhanced photo production and diffusivity of DGM, the concentrations of which roughly followed the same seasonal trend.
The first recovery of the conodont Hindeodus parvus from Žiri (Slovenia) a few years ago highlights this area for Early Triassic biostratigraphical study. Systematic sampling of five sections in the ...Idrija–Žiri area has yielded the new species Platyvillosus corniger sp. nov. and Neospathodus planus sp. nov. Based on these new species and other conodont elements collected here, nine discrete conodont Unitary Association (UA) zones are proposed for this area. In ascending order they are: Eurygnathodus costatus Zone (UA 1), Eurygnathodus hamadai Zone (UA 2), Foliella gardenae Zone (UA 3), Neospathodus robustus Zone (UA 4), Platyvillosus corniger Zone (UA 5), Platyvillosus regularis Zone (UA 6), Triassospathodus hungaricus Zone (UA 7), Triassospathodus symmetricus Zone (UA 8), and Neospathodus robustispinus Zone (UA 9). The conodont and δ13C data indicate that these conodonts span the Dienerian/Smithian (i.e. Induan/Olenekian) boundary interval to the Spathian, and they also indicate that Triassospathodus hungaricus Zone (UA 7) does not occur at the base of the Spathian. These conodont zones are valuable for stratigraphic correlation within Central and southern Europe, and they also promote a better correlation worldwide. Conodonts in the Idrija–Žiri area were adapted to a shallow-water environment in an epeiric ramp.
•Nine discrete conodont zones are identified for the Early Triassic in Idrija–Žiri, Slovenia.•δ13C data and conodonts indicate that these sections span the late Dienerian to Spathian.•According to δ13C data the Smithian/Spathian boundary is characterized by Foliella gardenae.•These conodonts were adapted to a shallow-water environment in an epeiric ramp.•This unique conodont sequence was probably the result of paleoecological influence and/or provincialism.
In the initial period of mining activities in the Idrija basin (the16
th and the first half of the17
th centuries), Hg ore processing was performed at various small-scale roasting sites in the woods ...surrounding Idrija, by roasting ore in earthen vessels. The recovery rate of this method was very low; about half of Hg was lost, causing soil contamination and considerable amounts of waste material that could potentially leach Hg into the surrounding environment. The main aims of present geochemical study were to determine the contents, vertical distribution and speciation of Hg in soils at the roasting site at Frbejžene trate in order to verify the extreme pollution of ancient Hg ore roasting sites in the Idrija area and to establish their significance in the wider spatial contamination of soils and aquatic systems. Soil sampling was performed at the area of the former roasting site. The organic matter-rich surface soil layer (SOM) and underlying mineral soil were sampled at 63 sampling locations. Mercury speciation was performed using Hg thermo-desorption-AAS to distinguish cinnabar from potentially bioavailable forms. The results indicate extremely high Hg concentrations with a maximum of 37,000
mg/kg in SOM and 19,900
mg/kg in mineral soil. The established Hg median in soil was 370
mg/kg and in SOM 96.3
mg/kg. Spatial distributions of Hg in SOM and soil showed very high Hg contents in the central area and decreased rapidly with distance. The results of Hg thermo-desorption measurements indicated the presence of cinnabar (HgS) and Hg bound to organic or mineral soil matter. A significant portion (35–40%) of Hg in the investigated soil and SOM samples was comprised of non-cinnabar compounds, which are potentially bioavailable. It has been shown that soils contain high amounts of potentially transformable non-cinnabar Hg, which is available for surface leaching and runoff into the surrounding environment. Therefore, contaminated soils and roasted residues at the studied area are important for persistent Hg release into the aquatic ecosystem.
► Extreme mercury soil contamination as a result of small scale ore roasting activity. ► Hg contents above 10,000
mg/kg determined in several soil and SOM samples. ► About 40% of Hg in investigated soil and SOM samples are potentially bioavailable.
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