Study of different environmental matrices to access the extension of metal contamination along highways

Integrated environmental assessment of iron ore tailings in floodplain soils and plants after the Fundão Dam disaster in Brazil

Previous studies of the Doce River basin (Brazil) seem to be contradictory regarding the contamination of soils with potentially harmful elements (PHE). This research aimed to perform an integrated assessment of PHE in the soil-plant-tailing system from the area most affected by the iron waste after the Fundão Dam disaster in 2015. Different fractions of PHE (exchangeable, nonexchangeable, reducible, and pseudo-total) were determined on deposited iron waste (DIW), soil waste mixture (SWM), and control soil (CS) samples. Total contents of PHE in Poaceae were also determined, and Allium cepa bioassays were performed to determine DIW and CS cytotoxicity and/or genotoxicity to plants. The Fe and Mn contaminations were the only ones related to the deposition of DIW on floodplains, and other harmful element content (such as As, Hg, Ni, Cd, Cr, and Pb) was not found above baseline values for soils. In addition, a significant part of the Fe and Mn in DIW is readily available or subject to acidification and prolonged flood reduction processes. The high available content of Fe favored its excessive accumulation by Brachiaria. The DIW chemical conditions reduced biological functions of A. cepa under a controlled environment. However, more drastic effects, such as genetic damage, were not seen. The postdisaster action of covering DIW with CS resulted in undesirable enrichment of Pb on the floodplain soils. The integrated results allow the conclusion that the iron waste is not a time bomb for PHE contamination of soils between the Fundão and Risoleta Neves Hydroelectric Dam (~100 km away from Fundão). Integr Environ Assess Manag 2024;20:117-132. © 2023 SETAC.

A simple method for microwave-assisted preparation of tire samples

Heavy metals content in tires affects the safety of soil and agricultural products. The digestion method is a pretreatment for determining heavy metals in tire samples, and will affect the efficiency and accuracy of the heavy metal determination. The microwave digestion process and reagents for tire samples are not currently standardized. Therefore, this study attempts to provide an appropriate method of resolution for scholars. All digestion processes were performed in Mars One. We tested 15 different acid mixtures to determine the best reagent type and dose and then investigated the effect of maximum temperature, holding time, and sample grams on the degree of digestion. In summary, the best condition to digest the tire sample was a mixture of 3 ml HNO3 and 7 ml H2SO4, taking 0.1 (± 0.0005) g tire sample, at the maximum digestion temperature of 220 °C for 25 min. The experimental conclusion will provide a reliable experimental method for scientists using MARS One to study heavy metals in tires. At the same time, researchers using the MARS series can also find valuable references in this paper.

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

The aim of this study was to determine the extent and patterns of antimony and tin contamination in soils along railway lines, as there are very few data in the literature on this subject. The study was conducted in north-western Croatia. Total and bioavailable concentrations of Sn and Sb were detected using high resolution inductively coupled plasma mass spectrometry (HR-ICP-MS). The following results were obtained: total concentrations of Sb ranged from 0.98 to 52.0 mg/kg and of Sn from 3.04 mg/kg to 97.6 mg/kg. The soil samples showed pronounced Sb and Sn enrichment, up to 87 and 33 times the median value for European soils, respectively. In contrast to the total concentrations, the bioavailable concentrations showed relatively low values. For Sn, the percentage of total content ranged from 0.001 to 0.021%, while for Sb it ranged from 0.001 to 0.136%. Statistical data analysis suggests that the distribution of Sb and Sn in soils near railway lines is influenced by the functional use of the site, distance from the tracks, topography, age of the railway line, and also by soil properties such as soil texture, humus content, and soil pH. This study demonstrates that rail transport is a source of soil pollution with Sn and Sb. The origin of Sb and Sn enrichment is abrasion by brakes, rails, wheels, freight losses, exhaust gasses, etc. Both elements in soils along railway lines pose an environmental risk to humans, agricultural production, and wildlife, and therefore further detailed studies are required.

Effects of compaction on lead availability in contaminated soils with contrasting texture

The effects of soil compaction on porosity (α), bulk density (ρs), and saturated hydraulic conductivity (Ksat) can create a physical barrier in the soil, reducing the vertical movement of toxic elements in the soil profile. However, the indirect effects of compaction in altering the forms and availability of heavy metals in soil have not been well-studied. This study examined the influence of compaction on forms of lead (Pb) in soils with contrasting texture. Four levels of compaction were imposed on a sandy loam and a clayey soil, which were artificially contaminated based on their maximum Pb adsorption capacity. Compaction had different effects on Pb forms depending on soil texture. In the sandy loam soil, compaction had a dual beneficial effect in mitigating the impact of Pb contamination, since it decreased Ksat, reducing metal transport to deeper soil layers, and also prevented transformation to more available Pb forms (soluble and exchangeable). Instead, there was an increase in the most environmentally stable forms of Pb (inner sphere adsorption on iron and manganese oxides). In the clayey soil, compaction caused a significant increase in soluble and exchangeable Pb, accompanied by a significant reduction in environmentally stable Pb (inner sphere adsorption on gibbsite and kaolinite). In addition, studies about Pb contents under compacted soil layers should be investigated, mainly in clayey soils with edible crops, and environmental remediation practices that involve the machines traffic (for example, phytoremediation-successive cultivation of Pb-hyperaccumulating plants) should be used with care to minimise the compaction of clayey soils.

Size distributions and heavy metal pollution of urban road-deposited sediments (RDS) related to traffic types

Little is known about the particles attached on the surfaces of coarse (> 150 μm) road-deposited sediments (RDS), which are potential contributors of stormwater pollution. Therefore, the size distributions and heavy metal (including Cu, Pb, Zn, Cr, and Ni) pollution of RDS were evaluated taking these attached particles into consideration. Moreover, the relationships of RDS contamination with traffic types were further discussed. The results showed that < 22, 22-38.5, 38.5-150, > 150 μm RDS and attached particles accounted for 2.1 ± 1.8%, 8.5 ± 5.7%, 50.7 ± 6.8%, 38.6 ± 8.3%, and 2.0 ± 1.2% of total RDS mass, respectively. The size distributions of attached particles were comparable to that of representative stormwater particles, suggesting their great potential to contribute stormwater particles by desorption. The Zn pollution of attached particles was remarkable, which was significantly higher than that of both fine (< 150 μm) and coarse (> 150 μm) RDS. The Cu and Pb pollution were comparable to that of fine RDS, which were significantly higher than that of coarse RDS. Conversely, the Cr and Ni pollution were comparable to that of coarse RDS, which were significantly lower than that of fine RDS. Traffic types were found to be closely related with RDS contamination, and thus are indicative of specific RDS pollution. For example, electrombile in old residential area is indicative of abnormal Pb pollution due to past emissions of leaded gasoline; lorry is indicative of remarkable Zn pollution of > 22 μm RDS due to abrasion of tires and metallic substances. Accordingly, traffic type is accessible to identify the typical pollutants in RDS to promote effective RDS management.

Sentinel species for biomonitoring and biosurveillance of environmental heavy metals in Nigeria

Nigeria receives copious annual precipitation to nourish its forests and agriculture, it has an extensive river drainage system, and it possesses valuable mineral deposits that stimulate both commercial and artisan mining activities. The combination of these features complicates Nigeria's efforts to produce adequate amounts of healthy foods to support its population. Toxic heavy metals like lead, cadmium, and mercury, and toxic metalloids such as arsenic, are also present in its mineral deposits and they migrate gradually into the soil and water of Nigeria by natural means. However, mining activities can liberate higher levels of toxic metals, which adversely affect Nigerian ecosystems and its food chains. Thus, environmental pollution due to anthropogenic activities is a major public health concern in Nigeria. This review covers the importance of native Nigerian and African wild and cultivated plants along with livestock and wild animals as sentinel species to evaluate heavy metals as environmental stressors and the use of sentinel species for food safety monitoring and for predicting potential risks to human health.

Assessing soil contamination in automobile scrap yards by portable X-ray fluorescence spectrometry and magnetic susceptibility

A by-product of industrialization and population growth, automobile scrap yards are a potential source of metal contamination in soil. This study evaluated the use of portable X-ray fluorescence (pXRF) spectrometry and magnetic susceptibility (χ) analysis in assessing metal soil contamination in scrap yards located in Brazil. Five automobile scrap yards were selected in Curitiba, Paraná State (CB1, CB2, and CB3) and Lavras, Minas Gerais State (LV1 and LV2). By evaluating metal concentrations and geoaccumulation index values, we verified moderate Cu, Pb, and Zr contamination and moderate to high Zn contamination, primarily in the topsoil (0-10 cm). Soil Zn concentrations in automobile scrap yards were on average four times higher than in reference soils, suggesting that galvanized automobile parts may be the primary source of this soil contaminant. Although other elements (i.e., As, Cr, Fe, Nb, Ni, and Y) were slightly increased compared to reference values in one or more soils, concentrations did not constitute contamination. Automobile scrap yard topsoil had higher χ values (5.8 to 52.9 × 10^-7 m³ kg^-1) at low frequency (χ_lf) compared to reference soil (3.6 to 7.5 × 10^-7 m³ kg^-1). The highest values of χ_lf occurred in LV soils, which also represented the highest Zn contamination. Magnetic multidomain characteristics (percent frequency-dependent susceptibility between 2 and 10) indicated magnetic particle contributions of anthropogenic origin. The use of pXRF and χ_lf as non-destructive techniques displays potential for identifying soil contamination in automobile scrap yards.

Topsoil pollution in highway medians in the State of São Paulo (Brazil): determination of potentially toxic elements using synchrotron radiation total reflection X-ray fluorescence

The presence of metals in vehicle emissions is due to several factors, such as the composition of fuels and lubricating oils, the wear of engine components, and their use in catalytic converters. It is known that the soil near highways is greatly affected by heavy vehicle traffic, since the use of highways is of fundamental importance for the flow of goods and public transport, especially in Brazil, street transport being the main form of transport in the country. Considering the scenario described, the main objective of this study was to monitor the concentration of potentially toxic elements in surface soils located on the medians of the main access highways in the city of Campinas (SP-Brazil) and classify the soils through geoaccumulation index. Using SR-TXRF it was possible to detect and determine the concentrations of 5 elements of toxic-environmental interest (Cr, Ni, Cu, Zn, and Pb) and 11 natural soil composition elements (Al, Si, S, Cl, K, Ca, Ti, Mn, Fe, Rb, and Sr). To evaluate the influence of highway distance on elementary concentrations, ANOVA and Tukey statistical tests were applied. Nickel, Cu, and Zn showed a decrease in their concentrations moving away from the highway, indicating their relation with vehicular emissions. Applying principal components analysis (PCA), it was possible to identify four groups of the quantified elements: those mainly related to the soil itself, those produced by traffic of automotive vehicles, and those emitted by industrial activities.

Arsenic and Heavy Metal Accumulation and Risk Assessment in Soils around Mining Areas: The Urad Houqi Area in Arid Northwest China as an Example

Mining activities make important contributions to economic growth, but they can also produce massive amounts of solid waste, such as tailings and metal accumulations. Taking the Urad Houqi mining area in Inner Mongolia as the study area, this study systematically assessed the contamination risk of arsenic and heavy metals in the soils of the study area and explored the contamination characteristics in a key polymetallic mining area. For the whole study area, based on the Nemerow comprehensive pollution method, almost half of the investigated sites were contaminated, and the most contaminated site was Urad Houqi Qianzhen Mineral Concentration Co., Ltd. (Bayannaoer, China), a cooperation between the lead and zinc mining industry. The assessment results indicated that Cd and As were the elements of greatest concern, followed by Pb, Cr and Hg. Particularly, for the typical Dongshengmiao mining area, when compared with the GB15618-1995 standard values, As, Zn and Cd posed the most serious contamination threat, while Cr and Ni exhibited clean conditions. In addition, the vertical distribution maps demonstrated that the contents of arsenic and metals in some soil profiles were correlated with sampling depth. Therefore, arsenic and heavy metals pose high threat to soil ecosystems in this area, there is encouragement for some control and remediation measures to be taken into effect.