Urban gardening offers multiple societal benefits, supporting both mental and physical well-being while enhancing access to fresh, locally grown produce. However, it may also pose potential health risks due to contamination of urban soils with potentially toxic elements (PTEs), including metal(loid)s. This study investigated metal(loid) concentrations in soils and homegrown vegetables from urban gardens across Bratislava (Slovak Republic) and evaluated the factors affecting their accumulation and bioavailability. Median Cu concentration in vineyard soils (51 mg kg-1 ) was twice those in non-vineyard soils (25 mg kg-1 ). In contrast, raised-beds gardens exhibited significantly lower concentrations of most metal(loid)s compared to ground plots (p<0.05). Soil concentrations of Cd, Cu, Pb, Sb, and Zn showed a positive correlation with garden age and negative correlation with distance from the historical city core (pre-1946 boundary), suggesting legacy anthropogenic inputs. Integrated analyses, including enrichment factor calculations and statistical source apportionment, confirmed that Cd, Cu, Pb, Sb, and Zn in garden soils originated predominantly from anthropogenic sources; whereas, metal(loid)s such as Al, Cr, Li, Ni, and V were likely governed by natural geological processes, including variation in parent material composition. Concentrations of Cd, Ni, and Pb in edible vegetables remained below the maximum allowable limits set by EU regulations. Estimated daily intakes of all metal (loid)s, based on average vegetable consumption, were substantially below respective tolerable daily intake thresholds. Human health assessments indicated negligible non-carcinogenic risks (hazard index < 1.0) and low carcinogenic risk (< 10-4 ), suggesting minimal public health concerns associated with consumption of homegrown produce or incidental soil exposure in these gardens. This study represents a comprehensive, citywide assessment of metal(loid) distribution in urban gardens within a medium-sized Central European city. It advances scientific understanding of metal(loid) dynamics in urban agroecosystems and supports evidence-based guidance to enhance public awareness of both the benefits and potential risks of urban agriculture.

Per- and polyfluoroalkyl substances (PFAS) are persistent contaminants that are widely detected in surface waters and are of growing global concern. However, the factors associated with variations in PFAS contamination across space and time at a continental scale remain poorly understood. Here, we combine results from a harmonised pan-European river monitoring study with partial least squares path modelling (PLS-PM) to identify the key factors associated with PFAS contamination in European rivers. Seven high-priority PFAS were monitored at 280 sites across 93 rivers in 31 European countries, representing the PFAS footprint of approximately 309 million people. At least one PFAS was detected at 93% of monitoring locations. Highest concentrations were observed in parts of southern, southeastern and western Europe and were associated with landfills, wastewater discharges and industrial activity. Higher PFAS concentrations occurred in summer, potentially reflecting dilution-related effects associated with lower flow conditions. PLS-PM revealed that PFAS concentrations were associated with socioeconomic pressures and environmental conditions. The Human Footprint Index showed the strongest association among the socioeconomic variables examined, while electrical conductivity was the environmental variable most strongly associated with PFAS concentrations, possibly reflecting shared transport pathways with wastewater and industrial effluents. An indicative, screening-level assessment against existing regulatory threshold values suggested that PFAS concentrations at 61% of sites are of potential concern. These findings support the use of combined human pressure and hydrochemical indicators to inform more targeted, risk-based monitoring and regulatory prioritisation at large spatial scales.

Landfills, especially those poorly managed, can negatively affect the environment and human beings through chemical contamination of soils and waters. This study investigates the soils of a historical municipal solid waste (MSW) landfill situated in the heart of a residential zone in the capital of Slovakia, Bratislava, with an emphasis on metal (loid) contamination and its consequences. Regardless of the depth, many of the soils exhibited high metal (loid) concentrations, mainly Cd, Cu, Pb, Sb, Sn and Zn (up to 24, 2620, 2420, 134, 811 and 6220 mg/kg, respectively), classifying them as extremely contaminated based on the geo-accumulation index (Igeo >5). The stable lead isotopic ratios of the landfill topsoil varied widely (1.1679–1.2074 for 206Pb/207Pb and 2.0573–2.1111 for 208Pb/206Pb) and indicated that Pb contained a natural component and an anthropogenic component, likely municipal solid waste incineration (MSWI) ash and construction waste. Oral bioaccessibility of metal (loid)s in the topsoil was variable with Cd (73.2–106%) and Fe (0.98–2.10%) being the most and least bioaccessible, respectively. The variation of metal (loid) bioaccessibility among the soils could be explained by differences in their geochemical fractionation as shown by positive correlations of bioaccessibility values with the first two fractions of BCR (Community Bureau of Reference) sequential extraction for As, Cd, Mn, Ni, Pb, Sn and Zn. The results of geochemical fractionation coupled with the mineralogical characterisation of topsoil showed that the reservoir of bioaccessible metal (loid)s was calcite and Fe (hydr)oxides. Based on aqua regia metal (loid) concentrations, a non-carcinogenic risk was demonstrated for children (HI = 1.59) but no risk taking into account their bioaccessible concentrations (HI = 0.65). This study emphasises the need for detailed research of the geochemistry of wastes deposited in urban soils to assess the potentially hazardous sources and determine the actual bioaccessibility and human health risks of the accumulated metal (loid)s.

Background: Groundwater contamination with chlorinated hydrocarbons (CLHCs), particularly with tetrachloroethylene (PCE) and trichloroethylene (TCE), which are used in industry for degreasing and cleaning, can be considered a serious problem concerning the entire world. In addition to conventional groundwater monitoring from a network of wells, several screening methods have been proposed to identify and delineate groundwater contamination with volatile organic compounds (VOCs), such as soil gas measurement, bioindicators, direct-push technologies or geophysical techniques. The main objectives of this study were to confirm the feasibility of active soil gas screening for the characterisation of groundwater contamination with CLHCs under the wider area of the former refrigerator manufacturer (city of Zlaté Moravce, western Slovakia) and to evaluate the human health risks through exposure to CLHCs present in groundwater. Methods: a conventional site investigation based on concentration measurements using gas chromatography-mass spectrometry from monitoring wells and soil gas measurements using a portable photo-ionisation detector device were applied. Results: The chemical analyses showed the persistent contamination of groundwater, with PCE, TCE and other CLHCs, such as cis-1,2-dichloroethylene (cis-DCE) or 1,1,2-trichloroethane (TCA), being most severe in the zone of the former factory (up to 2690, 83,900, 6020 and 156 µg/L for PCE, TCE, cis-DCE and TCA, respectively), but also extended into the residential zone located 600 m along the groundwater flow line. Soil gas measurements of VOCs and other chemical parameters (methane (CH4), total petroleum (TP), carbon dioxide (CO2) and oxygen (O2)) from a densely designed network of sampling points (n = 300) helped trace the current state of groundwater contamination. Spatial distribution maps of VOCs concentrations in soil gas clearly marked the areas of the highest CLHCs concentrations in groundwater. Principal component analysis (PCA) confirmed a significant correlation of VOCs and CLHCs with the first principal component, PC1, explaining up to 84% of the total variability of the concentration data, suggesting that VOCs in soil gas were a suitable marker of the extent of groundwater contamination with CLHCs. Despite severe groundwater contamination with CLHCs reaching residential areas, local residents were not exposed to non-carcinogenic risks, but a potential carcinogenic risk was present. Conclusions: based on the results, it could be confirmed that soil gas screening is an efficient and quick tool for identifying the sources of groundwater contamination with CLHCs as well as the level of this contamination.

Positive matrix factorisation (PMF) is a receptor model, which is frequently used in environmental geochemistry for metal(loid)s' source apportionment in various matrices. In this study, concentration data for As, Cu, Co, Cr, Fe, Mn, Ni, Pb, Sb, V and Zn in urban soils of two land uses (playground and roadside soils) from the city of Bratislava (Slovak Republic) were reinterpreted using the PMF model to quantify the contributions of individual sources of metal(loid)s in soils. Brake and tyre abrasion (27.0%), mixed traffic/industrial sources (14.3%), and natural origin (58.7%) were identified for roadside soils, while mixed traffic sources (28.4%), Cu-specific source (24.6%), and natural origin (47.0%) contributed to the metal(loid) concentrations in playground soils. Factor contributions revealed prevailing non-exhaust sources dominated by Cu, Sb and Zn over mixed traffic/industrial sources in roadside soils, following the world trend. Strong negative correlations of the 206Pb/207Pb isotopic ratio with Factor 1 in both groups of soils, representing traffic and industrial sources, are an evidence of the correct assignment of the obtained factor profiles to the actual sources of metal(loid)s in soils. There were significant differences in the proportion of mixed traffic sources in playground soils among the five urban districts, while the largest proportion of this source was identified in the city centre with the longest urbanisation and industrial history. Error estimation methods (displacement, bootstrap, displacement with bootstrap) proved that the data fit the model well and there was a minimal rotational ambiguity and random errors in the base model run.

Background and Aims Bioremediation of soils contaminated with metal(loid)s is an attractive research area due to its sustainability and economic benefits. In the Slovak Republic, there are several abandoned mines containing high concentrations of arsenic (As) and antimony (Sb). This calls for new options for removing these hazardous metalloids from contaminated substrates. Studies on bioleaching of soils co-contaminated with both metalloids are very rare. This study aimed to test the effectiveness of bioleaching of soils heavily co-contaminated with As and Sb (up to 1463 mg.kg –1 and 5825 mg.kg –1 , respectively) at a former stibnite mining site (Poproč, eastern Slovakia) through biostimulation and bioaugmentation. Methods Bioleaching of As and Sb from four soils was induced by biostimulation of autochthonous microflora with Sabouraud medium (SAB) and SAB+glucose, and bioaugmentation of the soil with bacterial strains Cupriavidus oxalaticus and Cupriavidus metallidurans . Soil samples were subjected to determination of physico-chemical properties, microbiological parameters, and additional mineralogical analysis. Results An inverse relationship between the total metalloid concentration and the microbial diversity was confirmed. In experiments with Cupriavidus metallidurans and Cupriavidus oxalaticus , mean bioleached As fractions were 37.6% and 41.3%, while Sb bioleaching was significantly lower, ranging between 17.0–26.2%. The mean bioleached fraction of As and Sb using SAB was 40.7% and 14.4%, respectively. The addition of glucose to SAB increased As bioleaching (50.7%) but not that of Sb. Conclusion Collectively, the results highlighted a role of microorganisms in the mobility of metalloids in soils with their prospective applications in remediation of contaminated sites.

Municipal solid waste incineration (MSWI) is an effective method for reducing the volume/mass of waste. However, MSWI ashes contain high concentrations of many substances, including trace metal (loid)s, that could be released into the environment and contaminate soils and groundwater. In this study, attention was focused on the site near the municipal solid waste incinerator where MSWI ashes are deposited on the surface without any control. Here, combined results (chemical and mineralogical analyses, leaching tests, speciation modelling, groundwater chemistry and human health risk assessment) are presented to assess the impact of MSWI ash on the surrounding environment. The mineralogy of ∼forty years old MSWI ash was diverse, and quartz, calcite, mullite, apatite, hematite, goethite, amorphous glasses and several Cu-bearing minerals (e.g. malachite, brochantite) were commonly detected. In general, the total concentrations of metal (loid)s in MSWI ashes were high, following the order: Zn (6731 mg/kg) > Ba (1969 mg/kg) ≈ Mn (1824 mg/kg) > Cu (1697 mg/kg) > Pb (1453 mg/kg) > Cr (247 mg/kg) > Ni (132 mg/kg) > Sb (59.4 mg/kg) > As (22.9 mg/kg) ≈ Cd (20.6 mg/kg). Cadmium, Cr, Cu, Pb, Sb and Zn exceeded the indication or even intervention criteria for industrial soils defined by the Slovak legislation. Batch leaching experiments with diluted citric and oxalic acids that simulate the leaching of chemical elements under rhizosphere conditions documented low dissolved fractions of metals (0.00-2.48%) in MSWI ash samples, showing their high geochemical stability. Non-carcinogenic and carcinogenic risks were below the threshold values of 1.0 and 1 × 10-6, respectively, with soil ingestion being the most important exposure route for workers. The groundwater chemistry was unaffected by deposited MSWI ashes. This study may be useful in determining the environmental risks of trace metal (loid)s in weathered MSWI ashes that are loosely deposited on the soil surface.

Community gardens are "green oases" of recent cities with many benefits for human society. From a human health perspective, these benefits can be damaged by chemical contamination of soil and cultivated vegetables. Using geochemical approaches, this study characterised (i) total metal(loid) concentrations in soils and two commonly grown vegetables in urban community gardens (Bratislava, Slovakia), (ii) gastrointestinal bioaccessibility using a modified physiologically based extraction test (PBET), and (iii) stable lead (Pb) isotopes in order to identify sources of metal(loid)s, solubilisation in the human body and migration of Pb from soil to vegetables. While some soils could be considered contaminated when compared to the Slovak legislation for agricultural soil, the bioaccessibility of metal(loid)s did not exceed 20% in the intestinal phase, with the exception of cadmium (Cd). Tomatoes and lettuce contained low total and bioaccessible concentrations of metal(loid)s, being safe for people who consume their own grown vegetables. There were differences in Pb isotope composition among bulk soils, vegetables and bioaccessible Pb, with less radiogenic Pb being preferentially mobilised. Statistical methods considering the compositional nature of the geochemical data and the enrichment factor (EF) distinguished well metal(loid)s of natural origin (As, Co, Cr, Fe, Mn, Ni, V) from those with anthropogenic contributions. This research has shown the usefulness of integrating different methodologies to better understand the geochemistry of metal(loid)s in urban soils with their highly diversified sources.

The former mercury ore deposit of Merník in Eastern Slovakia was selected for the investigation of the environmental availability of mercury (Hg), chromium (Cr) and nickel (Ni) in mine soils.Singlestep extractions with four chemical agents (deionised water, ethylenediaminetetraacetic (EDTA), acetic (CH 3 COOH) and hydrochloric (HCl) acid solutions) and chemical analysis of the common nettle (Urtica dioica) were used to determine the availability of the three metals.Regardless of the type of extraction, the soluble ratios of metals in mine soils increased in the order of Hg≤CrCH 3 COOH ≈ EDTA>˃H 2 O.The total or extractable metal concentrations in soil did not correlate with their concentrations in aerial parts of the common nettle, however, its ability to accumulate these trace metals in roots and aerial parts copied the results of extraction tests, i.e.Hg≤Cr

Combustion of fossil fuels is the most important source of polycyclic aromatic hydrocarbons (PAHs) in the environment. Cities are typical of many human activities which are dependent on fossil fuels (road and railway transport, heat generation, waste incineration and industry) on a small area, leading to high concentrations of PAHs in urban air, dust and soil. The aim of this study was to determine the possible influence of urban traffic on the accumulation of sixteen priority PAHs in soils (n = 132 at two soil depths of 0–10 cm and 10–20 cm) taken at intersections (n = 37) with different traffic volumes and road ages. Variable concentrations of the sum of PAHs (∑16PAH) ranging from 188 to 21,950 μg/kg with a mean and median of 3021 μg/kg and 1930 μg/kg were recorded, respectively. Concentrations of PAHs positively correlated with soil organic carbon content (TOC) (rSpearman = 0.518; p < 0.001). Statistically significant positive correlations between ∑16PAH concentrations and traffic volume/road age were found in this study (rSpearman = 0.689/0.619; p < 0.001), while ∑16PAH concentration decreased with increasing distance from the road edge and was statistically lower at a soil depth of 10–20 cm than at 0–10 cm (p < 0.05). Multivariate statistical methods (principal component analysis and cluster analysis) applied to log-ratio transformed data (clr) to decrease the constant sum constraint coupled with positive matrix factorisation (PMF) modelling pointed to the dominance of pyrogenic emission sources, with 62.1% traffic-related (petrol and diesel emissions, liquid fuel and motor oil spills, and tyre wear) according to PMF results.

Soils containing a large proportion of industrial waste can pose a health risk due to high environmentally available concentrations of toxic metal(loid)s. Nano zero-valent iron (nZVI) and amorphous manganese oxide (AMO) were applied as immobilising amendments (1 wt%) to soils with different industrial origin of As and Sb, and leaching of As, Sb, Pb, and Zn was investigated using a single extraction with deionised water. The different industrial impact was reflected in the mineralogy, chemical composition and pH of these soils. Water-soluble As ratios positively correlated with pH in all experimental treatments. A significant decrease of water-soluble As ratios was observed in all nZVI-amended soils (similar to 65-93% of the control) except for one sample with the lowest solution pH. Nano zero-valent iron was also successful in Sb immobilisation (similar to 76-90% of the control). Highly variable results were obtained for AMO, which only led to a decrease of water-soluble As in soils with solution pH of >= 7 (similar to 70-80% of the control), probably due to lower stability of AMO in acidic conditions. In each case, nZVI was more efficient at decreasing water-soluble As ratios than AMO. Dissolved Pb concentrations remained unchanged after the application of nZVI and AMO, and the decrease of Zn leaching using AMO was controlled mainly by soil pH increase induced by its application. According to the calculated saturation indices, tripuhyite (FeSbO4) was predicted to be the key mineral controlling Sb solubility in mine soils. Secondary Fe (hydr)oxides either originally present or newly formed due to nZVI oxidation were instrumentally identified at different stages of their transformation and metal(loid) retention. To conclude, nZVI is suitable for application to contaminated soils at a wide pH range, while the use of AMO for decreasing As leaching is limited to soils with pH >= 7.

It is well known that road transport emits various trace elements into the environment, which are deposited in soils in the vicinity of roads, so-called roadside soils, and thus contributes to the deterioration of their chemical state. The aim of this work was to determine concentrations of some metals and metalloids (arsenic (As), cobalt (Co), chromium (Cr), copper (Cu), iron (Fe), manganese (Mn), nickel (Ni), lead (Pb), antimony (Sb), vanadium (V), and zinc (Zn)) in soils from crossroads with traffic signals, which are characterized by deceleration of vehicles and increased emissions of elements related mainly to brake and tyre wear. The results confirmed a moderate enrichment of soils with Cu, Pb, and Zn (enrichment factor (EF) values > 2) and significant enrichment for Sb (EF > 5), while the other elements showed no or minimal enrichment. The age of crossroads proved to have a positive influence on the accumulation of some elements in soils with the largest differences for Cu, Fe, Pb, Sb, and Zn (p < 0.001). Traffic volumes expressed as the average daily traffic intensity (ADTI) also positively influenced soil concentrations of Cr, Cu, Pb, Sb, and Zn, while distance to the crossroad had a significant negative effect on the soil concentration of Cu, Sb, and Zn (p < 0.001). The stable isotopic ratios of Pb, 206Pb/207Pb and 208Pb/206Pb, ranging from 1.1414 to 1.2046 and from 2.0375 to 2.1246, respectively, pointed to the mixed natural-anthropic origin of Pb in the soils of crossroads with a visible contribution of traffic-related sources. Based on the above findings combined with covariance among the studied elements using statistical methods applied to compositionally transformed data, it was possible to show that Cu, Pb, Sb, and Zn clearly originated from road traffic.

Today, it is proven that the contaminated urban soils are hazardous for the human health. Soil substrates of playgrounds call for special research as they are places where children are directly exposed to soil contaminants. Therefore, the objective of this work was to measure the pseudo-total contents and bioaccessibility of several metals and metalloids (As, Bi, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Sb, Sn, V, Zn) in two grain sizes (< 150 μm and < 50 μm) of playground soils in Bratislava city (the capital of Slovakia). The content of metal(loid)s in the soils was controlled by a number of factors, with their increased contents (above 75% percentile or higher) at sites influenced by point sources of pollution (industry and agriculture) or at old sites located in the city centre. Cobalt, Cr, Fe, Mn, Ni and V had relatively uniform contents in soils compared to the other elements. As regression modelling with a categorical variable confirmed, the age of urban areas influenced the accumulation of As, Bi, Cd, Cu, Hg, Pb, Sb and Sn in playground soils. Exploratory statistical techniques with compositionally transformed data (principal component analysis, cluster analysis and construction of symmetric coordinates for correlation analysis) divided trace elements into the two main groupings, Co, Cr, Fe, Mn, Ni, V and Bi, Cd, Cu, Hg, Pb, Sb, Sn, Zn. Median concentrations of the elements in smaller soil grains (< 50 μm) were significantly higher than in coarser grains (< 150 μm). Cobalt, Cu, Mn, Pb, Sn and Zn had significantly higher bioaccessible proportions (% of the pseudo-total content) in < 50 μm soil size than in < 150 μm; however, the same order of bioaccessibility was achieved in both grain sizes. The highest bioaccessibility had Cd, Cu, Pb and Zn (~ 40% and more), followed by Co, As, Mn, Sb (18–27%), Hg, Ni, Sn (10–12%) and finally Cr, Fe and V (less than 4%). The hazard index and carcinogenic risk values were higher in < 50 μm than in < 150 μm and significantly decreased in the two soil sizes when the bioaccessibility results were included in the health hazard calculation.

The US EPA health risk assessment method is currently widely used to assess human health risks for many environmental constituents. It is used for risk assessment from the exposure to various contaminants exceeding tolerable or safe reference doses, determined e.g., for drinking water, soil, air and food. It accepts widely that excess contents of non-essential elements (e.g., As, Pb or Sb) in environmental compartments represent a general risk to human health. However, contrary to toxic trace elements, deficient contents of essential (biogenic) elements e.g., F, I, Se, Zn, Fe, Ca or Mg may represent even higher health risk. Therefore, we propose to extend the human health risk assessment by calculating the health risk for deficient content and intake of essential elements, and to introduce the terms Average Daily Missing Dose (ADMD), Average Daily Required Dose (ADRD) and Average Daily Accepted Dose (ADAD). We propose the following equation to calculate the Hazard Quotient (HQ) of health risk from deficient elements: HQd = ADRD/ADAD. At present, there are no reference concentrations or doses of essential elements in each environmental compartment in world databases (Integrated Risk Information System IRIS, The Risk Assessment Information System RAIS). ADRD and ADMD can be derived from different regulatory standards or guidelines (if they exist) or calculated from actual regional data on the state of population health and content of essential elements in the environment, e.g., in groundwater or soil. This methodology was elaborated and tested on inhabitants of the Slovak Republic supplied with soft drinking water with an average Mg content of 5.66 mg·L−1. The calculated ADMD of Mg for these inhabitants is 0.314 mg·kg−1·day−1 and HQd is equal to 2.94, indicating medium risk of chronic diseases. This method extending traditional health risk assessment is the first attempt to quantify deficient content of essential elements in drinking water. It still has some limitations but also has potential to be further developed and refined through its testing in other countries.

The protective role of hard drinking water against cardiovascular diseases is well documented by numerous studies. This article describes the impact of Ca and Mg contents in the drinking water with different water hardness on the cardiovascular system (arterial stiffness, arterial age) of residents of the Krupina district, the Slovak Republic. The research was based on the measurements of arterial stiffness, including the measurements of aortic pulse wave velocity (PWVao) and the calculation of the arterial age of the residents. In total, 144 randomly selected residents were included in measurements, divided into the two groups according to Ca and Mg contents in drinking water (water hardness). The first group was supplied with soft drinking water (total dissolved solids (TDS): 200–300 mg·L−1, Ca: 20–25 mg·L−1, Mg: 5–10 mg·L−1). The second group of residents was supplied with harder drinking water (TDS: 500–600 mg·L−1, Ca: 80–90 mg·L−1, Mg: 25–30 mg·L−1). Differences in arterial stiffness between the two groups of respondents were documented. Higher arterial stiffness (low flexibility of arteries) was determined for a group of residents supplied with soft drinking water. This was reflected in higher PWVao levels, higher number of pathological cases (PWVao > 10 m·s−1), and arterial age of respondents compared to their actual age. The “absolute” difference between the arterial and actual age between the two evaluated groups of residents (soft vs. harder water) was nearly 5 years on average. The higher arterial stiffness and age of residents that consumed soft drinking water indicate the health significance of lower contents of Ca and Mg in drinking water as an environmental risk factor of cardiovascular diseases. Measuring arterial stiffness of residents in the areas supplied with soft drinking water can be used as a non-invasive approach in the prevention of cardiovascular risks.

The aims of this study were to investigate the occurrence and distribution of total mercury (Hg) and other trace elements of environmental concern, such as arsenic (As), copper (Cu), chromium (Cr), manganese (Mn), nickel (Ni), lead (Pb), zinc (Zn) and vanadium (V), in soils from the abandoned Merník cinnabar mine in eastern Slovakia. For this purpose, thirty soil samples from two depth intervals within the mine area (n = 60 soil samples) and additional sixteen soil samples from adjacent areas (n = 25 soil samples) were collected. Total Hg was measured by atomic absorption spectrometry, while As and other metals were analyzed using inductively coupled plasma atomic emission spectrometry. High mercury concentrations (> 100 mg/kg with a maximum of 951 mg/kg) were observed only in surface soils close to mine waste heaps and adits. Otherwise, Hg concentrations in the majority of surface soils were lower (0.14–19.7 mg/kg), however, higher than Hg in soils collected from sites outside the mine area (0.19–6.92 mg/kg) and even considerably higher than Hg in soils at sites not influenced by the Merník mine. Elevated Cr and Ni concentrations in soils regardless of their sampling sites (mean of 276 mg/kg and median of 132 mg/kg for Cr and 168 mg/kg and 81 mg/kg for Ni, respectively) were attributed to the lithology of the area; the soils are underlain by the sediments of the Central Carpathian Palaeogene, containing a detritus of ultrabasic rocks. As our geochemical data are compositional in nature, they were further treated by compositional data analysis (CoDA). Robust principal component analysis (RPCA) applied on centred (clr) log-ratio-transformed data and correlation analysis of compositional parts based on symmetric balances distinguished very well different sources of origin for the chemical elements. The following three element associations were identified: Hg association with the main source in mining/roasting, Cr–Ni association derived from bedrock and As–Cu–Mn–Pb–Zn–V association (natural background and minor sulphides/sulfosalts in mineralized rocks). The values of geoaccumulation index and enrichment factor suggested that concentrations of Hg in the soils were influenced by human industrial activities.

This contribution investigates the natural attenuation of arsenic (As) and antimony (Sb) in highly contaminated soils at the abandoned Sb-deposit Poproč in eastern Slovakia. The studied soils were identified as technosols with pH values of 3.5–7.0 and high metal and metalloid load: antimony, arsenic, lead, and zinc up to 5757, 2484, 683, and 407 mg/kg, respectively. These toxic elements occur in the soils mainly as constituents of secondary minerals, which are products of sulphide oxidation. Bulk correlation between Fe and As is weak (p > 0.05), but inspection of micro-X-ray fluorescence maps shows that the secondary iron oxides are always associated with elevated As. Electron microprobe (EMP) and micro-X-ray diffraction analyses showed significant chemical and mineralogical heterogeneity of the secondary minerals, with wide variations of their Fe/Sb ratio and occasionally elevated Ca and Pb (> 5 wt%). The most common secondary minerals are goethite (α-FeOOH) with concentrations of Sb up to 3.14 wt% and As (1.29 wt%) and tripuhyite (FeSbO4) with increased content of As (1.14 wt%). Sb-rich secondary phases were identified as valentinite/senarmontite (Sb2O3), cervantite (Sb2O4), and a pyrochlore-group mineral stibiconite. High Sb phases with increased concentrations of Ca (up to 6.48 wt%) or Pb (20.78 wt%) were identified as stibiconite (EMP). This study shows that the secondary mineralogy in naturally attenuated contaminated soils and in Sb-containing tailings is identical. Hence, such tailings achieve their final state with respect to the Sb minerals within decades and are unlikely to change further.

In this study, playground soils of kindergartens and green recreational zones in Bratislava were investigated for the occurrence and gastric bioaccessibility of arsenic (As) in the < 150 μm soil size fraction. Eighty topsoil (0–10 cm) samples were collected from playgrounds in kindergartens and green recreational zones throughout the urban area. Bioaccessibility measurements of As were performed using the Simple Bioaccessibility Extraction Test that mimics the human gastric environment, and resulting extracts were analyzed by hydride generation-atomic absorption spectrometry to assess bioaccessible As concentrations in the collected playground soils. Single selective chemical extractions using hydroxylamine hydrochloride–hydrochloric acid and dithionite-citrate-bicarbonate solutions also were used to determine the amount of As associated with amorphous and amorphous/crystalline Fe oxy-hydroxides in soils, respectively. The results showed that the spatial distribution of total As concentrations was related to the historical development of the city, with higher soil concentrations of As found in the old city centre and related urban zones and the lower ones on the outskirts of Bratislava. There was a variation in the values of bioaccessible concentrations and fractions of As, with ranges from 0.40 to 5.60 mg/kg and 7.29 to 56.1%, respectively. Correlation and multivariable linear regression analyses revealed that bioaccessible concentrations of As were linearly related to its total concentrations in the soils, whereas dithionite-citrate-bicarbonate extractable Fe (FeDCB) was the main soil property, controlling the bioaccessibility of As. When the amount of FeDCB in the soils increased, As bioaccessibility decreased, confirming an importance of Fe bound to amorphous and crystalline iron oxy-hydroxides to the limitation of As bioaccessibility in urban playground soils of Bratislava. Additionally, single selective extractions showed that As concentrations extracted by hydroxylamine hydrochloride (AsHH) and dithionite-citrate-bicarbonate (AsDCB) were positively correlated with its bioaccessible concentrations (Spearman r = 0.75 and 0.62, respectively; p < 0.001).

The main aim of this paper was to investigate the removal efficiency of antimony (Sb) and arsenic (As) from circum-neutral mine drainage in the former Sb mine in Poproč (Slovakia) using a simple field treatment system based on the adsorption onto iron fillings. The treatment system consisted of two batch reactors with a volume of 1 m3: the first was used for settling of spontaneously precipitated ochreous sediments and the second, filled with reactive iron material, was designed to remove Sb and As from mine water. This passively operated treatment system contained 150 kg of low-cost iron fillings and was able to treat approximately 360 l of mine drainage per hour. The average removal efficiency of Sb and As reached 84 and 89% during a period of 2.3 years of the system operation, respectively. On average, dissolved Sb and As concentrations in mine drainage decreased from 175 to 24.3 µg/l and from 452 to 50.6 µg/l, respectively. Based on the electron microprobe (EMP) analyses of corrosion products developed on the surfaces of iron fillings, average Sb and As contents were 0.28 and 0.73 wt%, respectively. The chemical analyses of precipitated HFOs in the settling reactor showed that these ochreous precipitates contained up to 19.3 g/kg Sb and 65.8 g/kg As, indicating their natural role in the removal of the two metalloids from circum-neutral mine drainage. The results of transmission electron microscopy (TEM) and X-ray diffraction (XRD) analyses confirmed the presence of ferrihydrite and goethite in ochreous sediments.