The relationship between the inhalation bioaccessibility of potentially toxic elements in road dust from a heavily polluted industrial area and the source of their pollution.

One of the sources of chronic exposure to potentially toxic elements (PTE), especially in polluted environments, is the inhalation of resuspended road dust (RD). The aim of this study is to assess the inhalation bioaccessibility of PTE in RD from highly polluted environments from mining/smelting industries and traffic, and to identify any correlations between the bioaccessibility fraction of PTE and the physicochemical characteristics of the particles. RD from the studied area contains extremely high total concentrations of Cr, V, and Mn, which are likely due to pollution from the smelting industry. Additionally, elevated total concentrations of other elements associated with traffic emissions including Zn, Cu, Pb, Sb, and Sn were also measured. The bioaccessibility of PTE was assessed using two synthetic extraction solutions - Gamble's solution (GS) and Artificial Lysosomal Fluid (ALF). The majority of elements showed negligible bioaccessibility in GS. However, quite high inhalation bioaccessibility was observed for Zn, Pb, Sb, Cd, and Mn in the ALF solution, with a mean bioaccessible fraction of 49, 51.5, 41, 50, and 40% respectively. The highest bioavailable fraction was measured for Cd (97%) in a sample collected near a steel production facility and for Pb (95%) in a sample collected near the highway. These results indicate that increased mobility of the elements in inhaled particles occurs only in the case of phagocytosis. The lowest inhalation bioavailability was measured for Cr (mean is 3%). Differential individual particle analysis revealed that about 60% of phases, mostly major (Cr,Ti,V)-bearing metallic alloys, silicates, oxides and sulphides, are stable in ALF solution, while 40% of phases, mostly (Fe,Ca,Mn)-bearing oxides, silicates, sulphides, metals and metallic alloys originating from steel production, ferrochrome, ferrosilicon and vanadium production and from traffic emissions have been heavily corroded or completely dissolved. The study provides valuable information to further assess health hazards from various emission sources.

Natural and anthropogenic impact on the microclimate and particulate matter in the UNESCO show cave.

Particulate matter concentrations (PM10, PM2.5, PM1) and microclimatic parameters (air temperature, CO2) were monitored in the Skocjan Caves (Slovenia). The effects of tourist visits on the PM concentrations and the cave's microclimate are immediate and direct, but these values normalise relatively quickly. The results showed seasonal, diurnal, and spatial differences in all parameters studied. Due to the higher number of visitors, their influence on the cave's microclimate and PM10 and PM2.5 concentrations is greater in summer than in winter. The measured PM1 levels depend on the ventilation in the cave, as air transport plays an important role in their introduction into the cave. PM consists of minerals of natural origin resulting from the re-suspension of cave sediments due to strong air currents generated by the opening of the doors to tourists and their walks. The second most common influence is the anthropogenic phases originating from maintenance work in the cave, electronic devices, cave lighting and emissions from outside the cave (aerosols from the polluted Reka River, industry, traffic, gypsum waste disposal). In order to upgrade the sustainable use of the UNESCO-listed Skocjan Caves for tourism, we propose regular monitoring of PM and a detailed characterization of individual PMs and their sources, in addition to monitoring of the cave's microclimate and biology.

The environmental impact of historical Pb-Zn mining waste deposits in Slovenia.

Mining waste deposits (MWDs) represent significant and constant pollution source for the environment worldwide, thus it is very important to identify and diminish their environmental impacts. The aim of this study was to determine long-term environmental impacts and their temporal variations of MWDs in Pb-Zn mining districts in Slovenia and assess stability of potentially harmful element (PHE)-bearing phases in stream water. The results showed that investigated MWDs are important source of PHEs in stream sediments and that PHEs mostly occur as fine-grained and liberated PHE-bearing ore minerals. MWDs have generally stronger impact on sediments of smaller streams draining MWDs and main streams close to their confluences, however, fine-grained PHE-bearing material is transported along major watercourses over long distances causing regional pollution. Main ore minerals are mostly soluble in stream water. However, measured PHE leaching potential of MWDs is negligible. PHE levels in stream waters are thus low, demonstrating that drainage of MWDs predominantly contributes to PHE pollution in solid particulate form. Possible long-term remediation solution that would reduce environmental impact is recovery of metals from fine grain size fractions of MWDs, which could become an effective practice in sustainable management of historical MWDs. However, further studies of MWDs' secondary resource potential, processing technology and evaluation of environmental aspects of extraction are needed.

Contamination of children's sandboxes with potentially toxic elements in historically polluted industrial city.

When playing in sandboxes, children are particularly vulnerable to poisoning with potentially toxic elements (PTE) due to their hand-to-mouth behaviour. In Slovenia, the city of Celje is heavily contaminated due to zinc ore smelting and iron industry. In some sandboxes, sand from Mezica Pb-Zn mine waste was used. Granulometric and XRF analysis showed that all samples contain larger percentage of fine-sized particles and some have higher As, Ba, Cd, Pb and Zn contents than allowed. By XRD and SEM/EDS analysis we identified carries of PTE, and confirmed three possible sources of contamination: the waste material from the Pb-Zn mine, the emissions from local industry and from the old Zn-smelting stockpile used as a landfill. The total health risk (ΣHI) exceeds critical value in one sandbox. The bioaccessibility of PTEs is alarming due to presence of highly soluble metal-bearing particles. Study revealed importance of combining results of health risk evaluation with bioaccessibility of elements, which is a function of the carriers of PTE. This knowledge is essential for undertaking remedial measures. Improper use of waste material could result in introducing hazardous material in the environment. We propose frequent replacement of sand and stricter legislation regulating status and usage of waste materials.

Airborne particles in city bus: concentrations, sources and simulated pulmonary solubility.

PM10 and PM2.5 concentrations in Ljubljana city bus were monitored during entire shift, and individual particles were morphologically and chemically characterised in order to determine PM concentration variability, particle sources, solubility in simulated pulmonary environment and effects on human health. PM measurements revealed high mean PM10 (82.8 µg/m3) and PM2.5 (47 µg/m3), which were highest and most variable during rush hours with fluid traffic and lowest during traffic jams with standing vehicles. Individual particle analysis showed that airborne particles were dominated by metal-bearing phases, particularly small-sized (Cr,Mn,Zn)-bearing Fe-oxyhydroxides and Al-/Fe-Al-oxides, large (Fe,Cr,Ni)- and (Cu,Zn,Ni)-alloys, and small-sized Sb-sulphide and Ba-sulphate. Non-metallic phases were represented by (Ca,Mg)-carbonates, Al-silicates, Na-chloride and Ca-sulphate. Comparison with possible source materials (vehicle exhaust emissions, brake disc dust and road sediment) showed that primary sources of these metal-bearing phases were wear of brake discs, brake pads and tyres, and also wear of engine components and catalytic converters. Most non-metallic phases originated from resuspension of road sediment, containing road sanding materials, but also from emissions of burned fuel and lubricating oil (Ca-sulphate). Assessment of effects on human health indicated that mean PM concentrations, which significantly exceeded daily limit values, increased mortality (by 2-3%) and morbidity (by 7-8%) risk for bus drivers. Simplified PHREEQC calculations of airborne metal-bearing phase solubility in aqueous solutions simulating pulmonary environment showed that metallic Fe, Ba-sulphate, Sb-sulphide and Al-oxide, partly also Cu-bearing metal alloys, were soluble under reducing and oxidising conditions, but released metals were removed from solution by precipitation of stable secondary metal-bearing phases.

Assessment of contribution of metal pollution sources to attic and household dust in Pb-polluted area.

Attic and household dusts from Pb-polluted area were investigated using various analytical techniques for source apportionment and assessment of source contribution of metal-bearing phases. Mineralogically, attic dust consists of gypsum, anhydrite, and metal-bearing phases, while household dust comprises C-bearing particles and only minor metal-bearing phases. Sulfur isotope composition of sulfides and sulfates in attic dust shows that they result from past primary smelting of local sulfide ore, while those in household dust originate directly from local mine-waste material. Pb isotope ratios show that Pb-bearing phases in both dust types mostly originate from mining and primary smelting of local Pb-ore. Individual metal-bearing particles were apportioned by their composition, morphology, and mineralogy to phases from past Pb-smelting, present-day Pb-recycling, and past mining/mine-waste mechanical processing. Calculated source contribution of metal-bearing phases to indoor dust showed that primary Pb-smelting was important pollution source in the past, while active Pb-recycling has contributed only negligible amount of material so far. However, material from mining/mine-waste processing is an important currently active pollution source. Study demonstrated that simultaneous investigation of characteristics and isotopic composition of metal-bearing phases in different indoor dust types serves as tool for assessment of source contribution of past and recent airborne metal pollution.

Sources of sulphate minerals in limestone cave-a possible evidence of anthropogenic activity: a case study in Crna Jama Cave (Slovenia).

In the caves, the formation of cave minerals is a consequence of a variety of chemical reactions, some of them also due to human activity. There are many caves in Slovenia, but sulphate minerals are not very often reported and analysed. In this study, the presence of sulphate minerals is detected by SEM/EDS analysis of speleothems from Crna Jama, a cave near Kocevje (southern Slovenia). The cave is characterised by its dark, almost black colour on cave walls, floor and speleothems. Anthropogenic influence in the cave is still visible, including the remains of a fireplace, some inscriptions on the walls and wooden containers. The analyses of some of the black-coated speleothems reveal the presence of calcium sulphate, confirmed by XRD as gypsum. Gypsum crystals are around 50 µm in size, and they occur in thin crusts. Additionally, some rare authigenic baryte crystals a few micrometres in size are detected. The sulphates δ34S value in gypsum found on dark coloured speleothems is + 10.4‰ Vienna Canyon Diablo Troilite (VCDT), while the sulphate δ34S of the bedrock is + 8.6‰ VCDT. The more likely source of sulphate ions is thus biomass burning rather than bedrock. Also, bedrock and biomass ash are a very probable source of calcium and barium. The highly probable pyrogenous origin of sulphates draws attention to human impact on cave mineralogy.

Characterisation of secondary metal-bearing phases in used dental amalgam and assessment of gastric solubility.

Detailed SEM/EDS investigation of used dental amalgams was carried out in order to characterise morphology and chemical composition of secondary metal-bearing phases resulting from long-term exposure of dental amalgam to oral environment, and assess their solubility in gastric environment. The investigation revealed numerous secondary phases, represented by compositionally and morphologically complex Hg-, Cu-, Sn-, Ag-, Zn-bearing sulphides and oxides/hydroxides, while sulphates and phosphates are scarce. Secondary metal-bearing phases mostly occur at the amalgam/tooth interface; however, some phases were found only on the occlusal surfaces of amalgam. Secondary phases mostly form porous aggregates of minute crystallites and micro- or nanocrystalline crusts. In oral environment, these phases are mostly stable and represent trapping media for dissolved potentially toxic metals released during amalgam corrosion. Simplified PHREEQC calculations of solubility of secondary metal-bearing phases in aqueous environment under conditions similar to those in gastric environment showed that secondary phases are more soluble in gastric environment than in oral solutions, which is mostly due to their forms of occurrence. Secondary phases in gastric environment thus act as secondary sources of potentially toxic metals, particularly Sn, Zn and also Cu, which are released both under reducing and oxidising conditions especially in acidic environment. Only very small amounts of Hg are potentially released and should not represent serious threat. Secondary phases that contribute the most to bioaccessibility of these metals are Sn hydroxychlorides, Sn oxides/hydroxides, Sn sulphates/hydroxysulphates, Sn oxides, Zn sulphides and Cu sulphides (Cu2S).

Calcite precipitates in Slovenian bottled waters.

Storage of bottled waters in varying ambient conditions affects its characteristics. Different storage conditions cause changes in the initial chemical composition of bottled water which lead to the occurrence of precipitates with various morphologies. In order to assess the relationship between water composition, storage conditions and precipitate morphology, a study of four brands of Slovenian bottled water stored in PET bottles was carried out. Chemical analyses of the main ions and measurements of the physical properties of water samples were performed before and after storage of water samples at different ambient conditions. SEM/EDS analysis of precipitates was performed after elapsed storage time. The results show that the presence of Mg2+, SO42-, SiO2, Al, Mn and other impurities such as K+, Na+, Ba and Sr in the water controlled precipitate morphology by inhibiting crystal growth and leading to elongated rhombohedral calcite crystal forms which exhibit furrowed surfaces and calcite rosettes. Different storage conditions, however, affected the number of crystallization nuclei and size of calcite crystals. Hollow calcite spheres composed of cleavage rhombohedrons formed in the water with variable storage conditions by a combination of evaporation and precipitation of water droplets during high temperatures or by the bubble templating method.

Geochemical investigation of potentially harmful elements in household dust from a mercury-contaminated site, the town of Idrija (Slovenia).

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 (Hg0), 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.

Application of Scanning Electron Microscopy/Energy-Dispersive X-Ray Spectroscopy for Characterization of Detrital Minerals in Karst Cave Speleothems.

Micro-scale observations in karst caves help to identify different processes that shaped local morphology. Scanning electron microscopy/energy-dispersive X-ray spectroscopy inspection of speleothems from two karst caves in Slovenia, Predjama and Crna Jama, confirmed the presence of sub-angular to sub-rounded detrital fragments of clay minerals, feldspars, quartz, Fe-oxides/hydroxides, rutile and Nb-rutile, xenotime, kassite, allanite, fluorapatite, epidote, ilmenite, monazite, sphene, and zircon, between 2 and 50 µm across. These occur in porous layers separating calcite laminae in the clayey coating on the layer below the surface of the speleothems, and are also incorporated within actual crystals. It is likely that they are derived from the weathered rocks of the Eocene flysch. Probably they were first transported into the caves by floodwaters forming cave sediments. Later, depending upon the climate conditions, they were moved by air currents or by water to the surface of active speleothems. They might also be redeposited from overlying soils enriched with wind-transported minerals from the flysch, or from higher passages filled with weathered flysch sediment, by drip water percolating through the fissured limestone. As some of the identified minerals are carriers of rare earth elements, Ti and Zr, their presence could affect any palaeoclimatic interpretations that are based upon the geochemical composition of the speleothems.

Chemical and morphological characteristics of solid metal-bearing phases deposited in snow and stream sediment as indicators of their origin.

Detailed scanning electron microscopy/energy dispersive spectroscopy of metal-bearing particles in snow deposits and stream sediment from a steelworks area was performed. Identified metal-bearing phases were apportioned according to their chemical and morphological characteristics to anthropogenic phases and secondary weathering products. Anthropogenic metal-bearing phases are the most abundant in both media and are represented by various irregular ferrous oxides, ferrous alloys, spherical ferrous oxides, and ferrous silicates with variable contents of Cr, Mn, Ni, V, W, and Mo. Secondary weathering products are Al silicates, Fe oxy-hydroxides, and Fe oxy-hydroxy sulfates with minor contents of transition metals, resulting from weathering of anthropogenic phases and Pb-Zn ore minerals from a closed Pb-Zn mine located upstream from the study area. Comparison of anthropogenic metal-bearing phases in both media showed agreement in their compositions and morphologies and indicated their sources are high-temperature processes in steel production. It also showed that spherical metal-bearing phases were transported by the same transport medium, which is the atmosphere, while other phases were transported into stream sediment mostly by other pathways, such as precipitation runoff over contaminated surfaces.

Assessment of metal pollution sources by SEM/EDS analysis of solid particles in snow: a case study of Zerjav, Slovenia.

Solid particles in snow deposits, sampled in mining and Pb-processing area of Zerjav, Slovenia, have been investigated using scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDS). Identified particles were classified as geogenic-anthropogenic, anthropogenic, and secondary weathering products. Geogenic-anthropogenic particles were represented by scarce Zn- and Pb-bearing ore minerals, originating from mine waste deposit. The most important anthropogenic metal-bearing particles in snow were Pb-, Sb- and Sn-bearing oxides and sulphides. The morphology of these particles showed that they formed at temperatures above their melting points. They were most abundant in snow sampled closest to the Pb-processing plant and least abundant in snow taken farthest from the plant, thus indicating that Pb processing was their predominant source between the last snowfall and the time of sampling. SEM/EDS analysis showed that Sb and Sn contents in these anthropogenic phases were higher and more variable than in natural Pb-bearing ore minerals. The most important secondary weathering products were Pb- and Zn-containing Fe-oxy-hydroxides whose elemental composition and morphology indicated that they mostly resulted from oxidation of metal-bearing sulphides emitted from the Pb-processing plant. This study demonstrated the importance of single particle analysis using SEM/EDS for differentiation between various sources of metals in the environment.