Tin and Antimony as Soil Pollutants along Railway Lines—A Case Study from North-Western Croatia

Green and blue infrastructure as model system for emissions of technology-critical elements

Over the recent decades, technological advancements have led to a rise in the use of so-called technology-critical elements (TCEs). Environmental monitoring of TCEs forms the base to assess whether this leads to increased anthropogenic release and to public health implications. This study employs an exploratory approach to investigate the distribution of the TCEs Li, Be, V, Ga, Ge, Nb, Sb, Te, Ta, Tl, Bi and the REYs (rare-earth elements including yttrium) in urban aerosol in the city of Vienna, Austria. Leaf samples (n = 292) from 8 plant species and two green facades and water samples (n = 18) from the Wienfluss river were examined using inductively coupled plasma tandem mass spectrometry (ICP-MS/MS). Surface dust contributions were assessed by washing one replicate of each leaf sample and analysing the washing water (n = 146). The impacts of sampling month, plant species and storey level on elemental distribution were assessed by statistical tools and generative deep neural network modelling. Higher TCE levels, including Li, V, Ga, Ge, Tl, Bi, and the REYs, were found in the winter months, likely due to the use of de-icing materials and fossil fuel combustion. A. millefolium and S. heufleriana displayed the highest levels of Li and Ge, respectively. In addition, increased elemental accumulation at lower storeys was observed, including Be, Sb, Bi and the REYs, indicating greater atmospheric dust deposition and recirculation closer to ground level. The results suggest a broad association of TCE levels with urban dust. This study enhances the current understanding of TCE distribution in urban settings and underscores the importance of their inclusion in pollution monitoring. It highlights the complex interplay of human activities, urban infrastructure, and environmental factors, offering valuable insights for managing urban environmental health risks and underlining the need for comprehensive urban ecosystem studies.

Effects of dissolved organic carbon on potentially toxic element desorption in stormwater bioretention systems

Stormwater runoff contains dissolved organic carbon (DOC) and potentially toxic elements (PTEs). Interactions between DOC and PTEs can impact PTE speciation and mobility, but are not fully understood. Soil samples were collected from a vegetated bioretention bed to investigate the effects of DOC (0, 15, and 50 mg-C/L) on the desorption of 10 PTEs captured by the soil media: Mn, Fe, Co, Cu, Zn, As, Cd, Sn, Sb, and Pb. In the absence of DOC, the desorbed PTE concentration from bioretention media into the aqueous phase ranking was as follows: Fe > Mn ∼ Zn > Cu > Pb > Sb > As > Co > Sn ∼ Cd. Increased DOC concentrations resulted in a reduction of the soil-water distribution coefficient (Kd) values. The greatest shift in Kd was observed for Cu and lowest for Sb. The PTE sorption capacities were lower for surficial soil samples (lower Kd) compared to the deep soil samples. Overall, the desorbed PTE (average midchannel 55.7 μg/g) fraction accounted for <1.1 % of the total extracted PTEs (5364 μg/g), and while this is a small percentage of the total, this is the fraction that is mobile. The extracted PTE fractions revealed that DOC reduced the organic matter-bound and carbonate-bound fractions. The PTE desorption trends suggest that reducing DOC in stormwater runoff could be an effective measure to mitigate the release of PTEs into the environment.

Evaluating natural and anthropogenic inputs on the distribution of potentially toxic elements in urban soil of Valdivia, Chile

The increasing population in urban areas in the last decades requires an effort to understand the geochemistry of contaminant elements in urban soil. Topsoil plays a crucial role in the exposure of Potentially Toxic Elements (PTEs) to humans through ingestion, dermal contact, and inhalation. In Chile, the last census revealed that 88.6% of people live in cities or towns and only 11.4% in rural areas. This study presents the first systematic geochemical survey of urban soil in the city of Valdivia, in the South of Chile. Topsoil samples (0-10 cm depth) were collected in less disturbed locations within the city at 130 sampling sites using a grid of 0.25 km2 squares covering a total area of approximately 30 km2. The concentrations of Al, Fe, Na, Ca, Mg, K, Ti, Be, V, Cr, Mn, Co, Ni, Cu, Zn, As, Mo, Sn, Cd, Se, Pb and Hg were measured. The results showed that high concentrations of Cu, V, Zn and Pb are located mainly in the city's northern area and exceed international soil quality legislation for agricultural use. Data processing comprised plotting of individual spatial distribution maps and the use of a combination of multivariate statistical methods. Hierarchical cluster analysis and principal component analysis identified three element associations. The two element groups V-Al-Ti-Fe-Cr-Co-Mn-Be-Ni and Ca-Na-K-As-Mg are interpreted as a dominant lithological origin related to the most pristine soil conditions in less populated areas. By contrast, the Sn-Pb-Zn-Mo-(Cu-Hg) association presents a significant correlation with urbanization indicators, including vehicular traffic and industrial activities developed since the end of the nineteenth century in Valdivia.

Geochemical fractionation, mobility of elements and environmental significance of surface sediments in a Tropical River, Borneo

Miri River is a tropical river in Borneo that drains on flat terrain and urbanised area and debauches into the South China Sea. This paper documents the environmental status of this river, and provides an insight into the provenance using bulk chemistry of the sediments, and brings out the geochemical mobility, bioavailability, and potential toxicity of some critical elements based on BCR sequential extraction. The sediments are intense to moderately weathered and recycled products of Neogene sedimentary rocks. The hydrodynamic characteristics of the river favoured an upstream section dominated by fine sand, while the downstream sediments are medium silt. Based on the bulk geochemistry, the Miri River sediments are moderate to considerably contaminated by Cu, Mo, and As in the upstream and by Sb, As and Cu in the downstream. The potential ecological risk values are low except Cu and a significant biological impact is expected in downstream due to Cu, As, Zn and Cr. The mobility, bioavailability and Risk Assessment Code values for Zn and Mn are higher and thus may pose moderate to very high risk to aquatic organisms. Though a high bulk concentration of Cu is observed, the association of Cu with the bioavailable fraction is low.

Railway Urbanozems: Interrelation of Physicochemical and Integral Environmental Indicators

Urbanozems with typical pollution are formed along railways: heavy metals (HM), oil products, anthropogenic organic matter. Depending on the natural zone and intensity of the leaching regime, the accumulated pollution can have a different effect on the integral environmental indicators of soils – the toxicity and enzymatic activity. The aim of the work was to determine the influence of the railway on the physicochemical characteristics of adjacent urbanozems that are formed in the southern taiga zone and to find out the interrelation of these indicators with the toxicity and catalase activity of the soil. Samples of urbanozems were taken from the surface layer of 0-10 cm at the distance of 50 m west and east of the railway and at the distance of 100, 500, 1000 m of it (east). The pH, content of organic matter, humus, ammonium nitrogen, mobile forms of HM, mortality for Daphnia magna Straus, influence on bioluminescence of Escherichia coli Migula, and the catalase activity were determined in the samples. It was shown that the levels of toxicity and the activity of catalase are strongly related to the distance from the railway: Pearson’s coefficients (r) were -0.53 (D. magna), -0.69 (E. coli), 0.95 (catalase). However, the interrelation between the total pollution index (TPI) of metals and integral indicators is lower: r=0.50 for the pair “D. magna – TPI”, r=0.42 for “E. coli – TPI”, r=0.19 for “catalase – TPI”. Consequently, the reactions of living organisms and the activity of catalase were formed in response to a combination of pollutants, not to one group of compounds.

Pyrite ore cargo spills as a source of soil pollution and ecological risk along the abandoned railway corridors of the Tharsis and Rio Tinto mines (Spain)

Abandoned mining railways are a prominent legacy environmental issue facing many metalliferous regions with a long mining history. However, there is a general lack of information on potentially hazardous trace elements occurring in soils alongside railroad lines as a result of hazmat cargo spills. This paper explores for the first time the effects of pyrite ore transportation on soil pollution along the old railways of Tharsis and Rio Tinto, two historical mining districts of world-class importance in the Iberian Pyrite Belt. The railroad-side topsoil was found to be extremely acidic in reaction and contains abundant pyrite, spilled on the tracks during transit, and its oxidation products (jarosite, iron oxyhydroxides, and efflorescent sulfate minerals). Compared to local background concentrations, highly elevated levels of Pb, Zn, Cu, As, Hg, Sb, Bi, Cd, Ag, and Tl were detected in both railroad lines, indicating serious anthropogenic contamination. Exposure to soil contaminants, notably Pb, As, and Tl, could pose hazards to human health and the environment. Accordingly, a specific-site risk assessment is needed before the mining railway lines are converted into recreational trails.

Can Urban Grassland Plants Contribute to the Phytoremediation of Soils Contaminated with Heavy Metals

The main objective of this study was to investigate whether the most common wild plant species of urban grassland can be used for phytoremediation of soils polluted with heavy metals. The study was conducted in the city of Varaždin, in northern Croatia. The content of heavy metals (Cd, Cu, Fe, Mn, Ni, Pb, Zn) was determined in soil samples as well as in unwashed and washed plant samples (Taraxacum officinale, Plantago lanceolata, Trifolium repens). The results show that the most polluted site is the railway station, while most sites are polluted by road traffic. The soils are most enriched with Pb, Cu, Zn and Cd. The bioconcentration factors for all three plant species are <1, indicating the relatively low capacity of phytoextraction. A considerable amount of heavy metals is found in the dust deposited on the plant surface, which is confirmed by a statistically significant difference between washed and unwashed plant samples. In addition, the biomass of each plant species that can be removed (in t/ha year), the mass of specific heavy metal that can be removed (in kg/ha), and the years required for phytoremediation are reported. In conclusion, phytoremediation with only common plant species of urban grassland is not possible within a reasonable period of time.