Results are presented of the first airborne LiDAR survey ever flown in Europe for the purpose of mapping the surface expression of earthquake‐prone faults. Detailed topographic images derived from ...LiDAR data of the Idrija and Ravne strike‐slip faults in NW Slovenia reveal geomorphological and structural features that shed light on the overall architecture and kinematic history of both fault systems. The 1998 MW = 5.6, and 2004 MW = 5.2 Ravne Fault earthquakes and the historically devastating 1511 M = 6.8 Idrija earthquake indicate that both systems pose a serious seismic hazard in the region. Because both fault systems occur within forested terrain, a tree removal algorithm was applied to the data; the resulting images reveal surface scarps and tectonic landforms in unprecedented detail. Importantly, two sites were discovered to be potentially suitable for fault trenching and palaeo‐seismological analysis. This study highlights the potential contribution of LiDAR surveying in both low‐relief valley terrain and high‐relief mountainous terrain to a regional seismic hazard assessment programme. Geoscientists working in other tectonically active regions of the world where earthquake‐prone faults are obscured by forest cover would also benefit from LiDAR maps that have been processed to remove the canopy return and reveal the forest floor topography.
Mercury distribution and partitioning was studied in the River Idrijca system, draining the area of the former Idrija mercury mine, Slovenia. Mercury dynamics were assessed by speciation analysis of ...mercury in water and river bed sediment samples during a 2-year study at locations on the River Idrijca and its major tributaries. Simultaneously, the influence of some major physico-chemical parameters that influence the fate of mercury in the aquatic environment was investigated. The distribution of mercury species in the River Idrijca catchment indicated contamination from mine tailings distributed in the town of Idrija and erosion of contaminated soils. The partitioning between dissolved and particulate mercury phases in river water was found to be mostly controlled by the variable content of suspended solids resulting from changing hydrological conditions and complexation with various ligands present in river water, among which dissolved organic carbon (DOC) seems to be the most important. Overall results indicate that mercury is transported downstream from the mining area mainly as finely suspended material including colloids rather than in the dissolved phase. This riverine transport occurs mostly during short, but extreme hydro-meteorological conditions when remobilization of mercury from the river bed sediments occurs. A significant part of the mercury particulate phase in water corresponds to cinnabar particles. During its transport, important Hg transformation mechanisms that increase the risk of mercury uptake by biota take place, evidenced by the increase in the relative contribution of reactive mercury (Hg R ), dissolved gaseous mercury (DGM) and monomethylmercury (MeHg) downstream from the Idrija mine. However, our data revealed relatively low methylation efficiency in this contaminated river system. We attribute this to the site specific physico-chemical conditions responsible for making inorganic mercury unavailable and limiting the capacity of methylating bacteria.
The atmospheric distribution and deposition of Hg in the area of the former Idrija Hg-mine, Slovenia, were investigated. Mapping of air Hg
0 concentrations was performed to assess the spatial ...distribution and major sources of mercury to the atmosphere in the area. In addition, analyses of mercury speciation in the air over Idrija were performed during a 4-day sampling campaign in September 2006 to better understand the fate and transformation of Hg in the atmosphere of this specific mercury polluted site. The speciation results were then compared to the results of mercury speciation in the wet and throughfall deposition sampled on a precipitation event basis from October 2006 to September 2007. The Hg
0 concentration in air was mostly below 10
ng
m
−3, with the highest concentration in the area of the former smelter complex exceeding 5000
ng
m
−3. Mercury-bearing airborne particles (TPM) seem to dominate the atmospheric Hg deposition, which revealed noticeable variations between precipitation events (11–76
ng
m
−2
day
−1), mostly as a function of the amount of precipitation. Hg in precipitation was largely (∼50%) associated with the particulate phase (THg
P). No correlation was found between the THg
P and the dissolved phases (THg
D), suggesting that particulate phase Hg is mostly the result of dry deposition. In the throughfall, significantly higher (2–10 fold) Hg concentrations than in associated event precipitation were observed, mostly due to Hg in the particulate phase (∼70% THg). As shown by SEM/EDXS microscopy, an important amount of mercury in the precipitation and throughfall samples is due to the presence of cinnabar particles as a result of the aeolian erosion of cinnabar-containing surfaces in the area.
► Soils surrounding the smelting plant are the main source of Hg in the Idrija region. ► Atmospheric Hg in the Idrija Hg-mine region is subjected to long range transport. ► Mercury-bearing airborne particles dominate the atmospheric deposition.
Purpose
Concentrations and transformations of mercury were measured in river, estuarine, and marine sediments to determine factors affecting the fate of mercury entering the northern Adriatic Sea.
...Materials and methods
Radiotracer methodology was used to compare rates of mercury methylation (
203
Hg), MeHg demethylation (
14
C), and sulfate reduction (
35
S) in sediment depth profiles to concentrations of total and dissolved mercury species in the lower freshwater region of the Isonzo River, the coastal lagoons, and in the Gulf of Trieste, northern Adriatic Sea.
Results and discussion
Mercury was readily methylated and demethylated in all sediments, but the relative activity of these processes varied greatly with location. Methylation activity increased greatly from freshwater to the marine regions; however, demethylation was extremely high in the estuarine and lagoon sites. Ratios of methylation to demethylation were low in these coastal sites but increased further offshore in the gulf, which agreed with increased ratios of MeHg to total Hg (%MeHg) in gulf sediments. Comparisons of microbial activities indicated that sulfate reduction strongly controlled both methylation and demethylation. However, Hg methylation in coastal lagoon sediments was controlled by rapid demethylation and the bioavailability of Hg that was affected by Hg adsorption and precipitation. Methylation in offshore marine sites correlated with sulfate reduction but not the partitioning of Hg between pore water and solid phases. The decrease in sulfide production offshore exacerbated Hg methylation.
Conclusions
The freshwater to marine gradient in the Idrija/Soča/Isonzo/Adriatic region is dynamic, exhibiting horizontally variable rates of microbial activities and Hg transformations that create “hot spots” of MeHg accumulation that are controlled differently in each region.
The influence of geomorphological factors to Hg contamination of the Idrijca River alluvial sediments because of the historical mining and ore roasting activities has been studied. Main source of Hg ...in alluvial sediments was dumping of ore roasting residues and mining waste into the river channel and its erosion downstream. The position of the material in relation to the geomorphological properties is highly related with its Hg content. Floodplains were found to be the most contaminated geomorphological units (mean Hg content 335
mg/kg), with Hg concentration rapidly dropping in the first terrace (155
mg/kg). The least contaminated material was found in the higher terraces (3.8
mg/kg). Sampling upstream Idrija (average Hg content is 22.1
mg/kg) shows that not only mine and ore roasting plant increased Hg levels in alluvial deposits but also contaminated sites upstream Idrija contribute to Hg contamination. Geochemical background for alluvial sediments for this area is estimated to be 0.75
mg/kg. Downstream Idrija, 9 hotspots were determined where highly contaminated material is actively eroded and carries a high risk of further contamination of the Soča River and northern Adriatic Sea ecosystems.
► Hg contamination of alluvial sediment because of mining tradition in Idrija. ► High rate of contamination, up to 2000
mg/kg, enrichment factors up to 15,000. ► Floodplain most contaminated geomorphological unit. ► Exponential decrease of contamination in relation to the distance from the source. ► Geochemical background for Hg in alluvial sediments estimated to 0.75
mg/kg.
A comprehensive geochemical investigation of potentially harmful elements (PHEs) in household dust from the town of Idrija (Slovenia), once a world-famous Hg mining town that is now seriously ...polluted, was performed for the first time. After aqua regia digestion, the content of mercury (Hg), arsenic (As), cadmium (Cd), cobalt (Co), chromium (Cr), copper (Cu), molybdenum (Mo), nickel (Ni), lead (Pb) and zinc (Zn) was measured. PHE-bearing particles were recognised and observed by scanning electron microscopy and energy-dispersive spectrometry before and after exposure to simulated stomach acid (SSA). Mercury binding forms were identified by Hg thermal desorption technique and gastric bioaccessible Hg was estimated after SSA extraction by ICP-MS. With regard to rural and urban background values for Slovenia, high Hg content (6–120 mg/kg) and slightly elevated As content (1–13 mg/kg) were found. Mercury pollution is a result of past mining and ore processing activities. Arsenic content is potentially associated with As enrichment in local soils. Four Hg binding forms were identified: all samples contained Hg bound to the dust matrix, 14 samples contained cinnabar, two samples contained metallic Hg (Hg
0
), and one sample assumingly contained mercury oxide. After exposure to SSA, Hg-bearing phases showed no signs of dissolution, while other PHE-bearing phases were significantly morphologically and/or chemically altered. Estimated gastric Hg bioaccessibility was low (<0.006–0.09 %), which is in accordance with identified Hg binding forms and high organic carbon content (15.9–31.5 %) in the dust samples.
Total Hg concentrations and Hg speciation were determined in soils and attic dust in a 160 km
2 area around Idrija mercury mine. Attic dust as well as a sample of soil was collected at 100 locations. ...Mercury phases were separated into cinnabar and non-cinnabar compounds via a thermo-desorption technique. The amount of the non-cinnabar fraction is important since it is potentially bioavailable and results are needed for further risk assessment studies.
The concentrations of Hg in attic dust are many times higher than in surrounding soils and the attic dust/soil ratio changes with distance. The highest concentration ratios were identified at the greatest distance from the source of pollution and the lowest close to the source of pollution.
This confirms the impact of air emissions on the wider area around Idrija. Furthermore the spatial mercury distribution in the attic dust shows that the influence of atmospheric emissions caused by the Idrija smelter resulted in impacts on the environment on a regional scale. The portions of non-cinnabar compounds increase with distance from the mercury source in both sampling media. Non-cinnabar fractions were found to be enriched in distant areas where fine grained material was deposited. There were two different transport mechanisms of dust particles and gaseous Hg(0) during the mercury production period. Obviously coarse grained particles, with mostly cinnabar-bound Hg settled in the immediate vicinity of the smokestack of the smelter, whereas the fine grained fraction could be dispersed further ahead. This is represented by the percentage of cinnabar-bound Hg in attic dust and soil decreasing with distance from the smelter. Gaseous Hg(0) is probably bound to fine and ultrafine aerosols with longer residence time against deposition. The consequence is that fine grained material with Hg
2+ and Hg
0 prevails in remote localities and is bound in soils and dust with matrix and organic matter as non-cinnabar mercury compounds.
The distributions of mercury species in attic dust and soils along the Idrijca River show that in the region from Idrija to Spodnja Idrija the portions of cinnabar and non-cinnabar are about equal, while in the upper and in the lower Idrijca valley non-cinnabar bound mercury prevails.
The applicability of attic dust for tracing the mercury halo in the Idrija area was successfully shown.
Mercury in air over the Idrija region, where the world's second largest mercury (Hg) mine is located, decreased significantly in the last decade, from more than 20,000
ng
m
−3 in the early 1970s to ...values below 100
ng
m
−3 in the 1980s, and finally reached a level of 10
ng
m
−3 or even lower at the summer of the year 2004.
The air concentration of Hg was continuously monitored after closure of the Hg mine. Hg
0 in air was mapped in November 2003 at over 100 locations in the Idrija region during a 3-day period under different weather conditions, and the concentrations found were between 2.5 to over 2000
ng
m
−3. The Hg concentration in air was mostly below 10
ng
m
−3. The highest values were observed in the near vicinity of the former smelting plant, as well under its chimney. Elevated concentrations were also observed at some other locations in Idrija town. Mercury evaporation from topsoil was measured continuously for a 24
h period at two heavily polluted locations in Idrija and 50
km downstream the River Idrijca at Bača pri Modreju. The average Hg concentration in air at Bača pri Modreju was 5.5
ng
m
−3, with an average Hg flux from soil to atmosphere of 34
ng
m
−2
h
−1. At the site in Idrija the average Hg concentration in air was 11
ng
m
−3 with an average Hg flux from soil to the atmosphere of 84.4
ng
m
−2
h
−1.
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