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Ultramafic soils are a natural source of metals such as Ni, Co and Cr that can pose ecosystem and human risks. Here, we assessed the environmental, ecological, and human health (carcinogenic and non-carcinogenic) risks from exposure to ultramafic soils through an integrated approach using petrographic and soil mineralogical assessments together with total, available, bioaccessible, and soil fractions analyses of Ni, Co and Cr in ultramafic soils from Brazil. The metal concentrations were similar or up to 5-fold higher for Ni than other studies worldwide in ultramafic soils. Soil sequential extraction showed Co and Ni predominantly bound to Fe and Mn oxides, while Cr was mostly in residual fractions. Medium environmental risks were found for Ni (RAC = 13.0), but no environmental risks were associated with Co and Cr in soils. Ecological risks were high (PERI = 522.8) and significantly high (PERI = 1759.9). Low metal bioaccessibility led to acceptable carcinogenic and non-carcinogenic risks for all routes of human exposure to soil, but consuming vegetables grown in these soils posed unacceptable cancer risks (> 10 -3 ). Our results reinforce the need to monitor ultramafic areas regarding the mobility and availability of metals in the soil to ensure food safety and human health., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

X-ray fluorescence is a fast, cost-effective, and eco-friendly method for elemental analyses. Portable X-ray fluorescence spectrometers (pXRF) have proven instrumental in detecting metals across diverse matrices, including plants. However, sample preparation and measurement procedures need to be standardized for each instrument. This study examined sample preparation methods and predictive capabilities for nickel (Ni) concentrations in various plants using pXRF, employing empirical calibration based on inductively coupled plasma optical emission spectroscopy (ICP-OES) Ni data. The evaluation involved 300 plant samples of 14 species with variable of Ni accumulation. Various dwell times (30, 60, 90, 120, 300 s) and sample masses (0.5, 1.0, 1.5, 2.0 g) were tested. Calibration models were developed through empirical and correction factor approaches. The results showed that the use of 1.0 g of sample (0.14 g cm -2 ) and a dwell time of 60 s for the study conditions were appropriate for detection by pXRF. Ni concentrations determined by ICP-OES were highly correlated (R 2  = 0.94) with those measured by the pXRF instrument. Therefore, pXRF can provide reliable detection of Ni in plant samples, avoiding the digestion of samples and reducing the decision-making time in environmental management., (© 2024. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)

The continuous expansion of the global vehicle fleet poses a growing threat to environmental quality through heavy metal contamination. In this scenario, monitoring to safeguard public health in urban areas is necessary. Our study involved the collection of 36 street dust and 29 moss samples from roads of a Brazilian metropolis (Recife) with varying traffic intensities as follows: natural reserve (0 vehicles per day), low (< 15,000 vehicles per day), medium (15,000-30,000 vehicles per day), and high (> 30,000 vehicles per day). ICP-AES analysis was performed to determine the concentrations of nine potentially toxic metals (Ba, Cd, Cr, Cu, Mn, Ni, Pb, V, and Zn) to assess the influence of vehicular flow on urban contamination. In the street dust samples, the mean metal concentrations (mg kg -1 ) exhibited the following order: Ba (503.7) > Mn (303.0) > Zn (144.4) > Cu (95.3) > Cr (56.1) > Pb (34.2) > V (28.7) > Ni (11.3) > Cd (1.5). Conversely, in the moss samples, the metal concentration order was as follows (mg kg -1 ): Mn (63.8) > Zn (62.5) > Ba (61.0) > Cu (17.7) > Cr (8.0) > V (7.3) > Pb (7.0) > Ni (2.9) > Cd (0.3). Roads with higher traffic volumes exhibited the highest metal enrichments in moss samples for all metals and in dust samples for Cd, Cr, Mn, Ni, and V. However, dust from low-flow roads had higher enrichments for Ba, Cu, and Zn, indicating the influential role of other traffic-related factors in metal deposition. Our findings highlight traffic flow as the predominant source of pollution in urban centers, with both street dust and moss serving as sensitive indicators of metal input attributable to vehicular traffic. These indicators offer valuable insights for urban quality monitoring and pollution control efforts., (© 2024. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)

Heavy metal pollution by accelerating urbanization is an emerging socio-environmental issue that poses a potential risk to human health and the environment. In this scenario, street dust is a primary source of contaminants. Here, the metal concentrations in street dust of one of the biggest Brazilian cities were assessed aiming to identify and quantify the sources of contamination. The metal bioaccessibility and estimated probabilistic (non)-carcinogenic risks to humans were also evaluated. Thirty-six dust samples were collected in the metropolitan region of Recife. Results showed that the traffic governed the distribution and accumulation of metals in street dust. Emissions from vehicles were the primary source (> 70 %) of heavy metals, except for Cd, which had a mixed origin (natural, traffic, and industrial). Moderate to heavy dust contamination by Ba, Cu, Mn, Pb, and Zn were found, with a very high potential ecological risk. The main exposure route depended on the metal. Barium, Cu, and Pb had ingestion rather than dermal contact as the main route of exposure, while inhalation and dermal contact posed the main risks to Mn and Cr, respectively. The risk for children was higher than for adults. The probabilities of unacceptable carcinogenic risk scenarios (TCRI >10-6) for children and adults were 27 and 4 %, respectively, with Cr being the most concerning metal for the health of the urban population., Competing Interests: Declaration of competing interest We confirm that no conflicts of interest are associated with the publication and that all authors are aware of the submission. Neither the manuscript nor any part of it are currently under consideration or published in another journal., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Heavy metal-contaminated wastes can threaten mangrove forests, one of the most biodiverse ecosystems in the world. The study evaluated the geospatial distribution of heavy metals concentrations in soils, the ecological and human health risks, and metal contents in soil fractions and mangrove organisms in the Botafogo estuary, Brazil, one of the most environmentally impacted estuaries in the country. The metal concentrations exceeded by up to 2.6-fold the geochemical background; 91%, 59%, 64%, 31%, and 82% of the soils were contaminated with Cr, Zn, Pb, Cu, and Ni, respectively. Adverse effects to the biota may occur due to Cr, Cu, Ni and Pb exposures. Contents of clay and organic matter were the main factors governing the distribution of metals in soil, contributing to up to 63% of the total variability. However, the geospatial modeling showed that the predictive ability of these variables varied spatially with the metal and location. The ecological and human health risks assessments indicated that the metal concentrations in soils are safe for the environment and human beings. There was a low transfer of metals from the soil to the biota, with values of sediment-biota accumulation factor (SBAF) and biological accumulation coefficients (BAC) lower than 1.0, except for Zn (SBAF = 13.1). The high Zn bioaccumulation by Crassostrea rhizophorae may be associated with the concentrations of Zn in the bioavailable fractions., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Biochar has attracted interest due to its ability to improve soil fertility, soil carbon, and crop yield. Also, biochar can adsorb metals and render them less bioavailable. We investigated the soil availability, sequential extraction, and maize uptake of Cd, Pb, and Zn in a highly contaminated soil amended with rice straw biochar rates (0.0, 5.0, 10.0, 20.0, and 30.0 Mg ha -1 ). We hypothesized that biochar application to the soil cultivated with maize attenuates metal toxicity and mobility in slag-polluted soils near an abandoned Pb smelting plant in Brazil. Results showed that applying biochar increased the soil organic carbon, CEC, and P up to 27, 30, and 107, respectively. Plant accumulation of P and N was 104 and 32% higher than control, while aerial and root biomasses were increased by 18 and 23%. The sequential extraction showed that Pb and Zn in the original soil were retained mainly in residual fractions (94 and 87%, respectively), while Cd was mostly allocated in the organic fraction (47%). Biochar rates increased the proportion of Cd in the organic fraction to 85%, while Pb and Zn were redistributed mainly into iron oxides. The Cd, Pb, and Zn bioavailability assessed by DTPA decreased 32% in the biochar-amended soil, reducing plants' metal uptake. The maize biomass increase, metal soil bioavailability decrease, and low metal concentration in shoots driven by biochar indicate that phytoattenuation using rice straw biochar and maize cultivation could reduce risks to humans and the environment in the polluted sites of Santo Amaro., (© 2021. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Food production in areas contaminated by industrial wastes poses a serious risk to farmers and consumers. Here, we evaluate Cd, Cr, Ni, and Pb concentrations in the soils and the edible parts of lettuce, chives, tomatoes, pepper, and cassava plants grown by small farmers in areas contaminated by slag from an abandoned steel plant in Havana, Cuba. The total, environmentally available, and bioavailable concentrations of metals in the soils and the metals bioconcentration factor in the plants were determined. The risks to human health from food and soil ingestion were estimated. The total and environmentally available concentrations of Cd, Cr, and Pb were above values considered safe by international standards, with likely adverse effect on human health. Cadmium was the most bioavailable metal, reflected in the highest accumulation in the crops' edible parts. Even with negligible DTPA-available Cr concentrations in soils, the Cr concentrations in edible parts of the crops exceeded regulatory levels, suggesting that rhizosphere mechanisms may increase Cr availability. The consumption of vegetables represented 70% of the daily intake dose for Cr, Cd, and Ni, while accidental ingestion of contaminated soil is the predominant human exposure route for Pb. Our results demonstrated the health risks associated with cultivating and consuming vegetables grown on metal contaminated soils in Havana and can assist public policies capable of guaranteeing the sustainability of urban agriculture and food security., (© 2021. The Author(s), under exclusive licence to Springer Nature B.V.)

The emission of mercury (Hg) by chlor-alkali plants can pollute soils and sediments, posing risks to the environment and human health. Mangrove ecosystems are particularly sensitive to Hg contamination. Here, we studied the Hg spatial distribution and associated human and ecologic risks in mangrove soils impacted by a chlor-alkali plant. Sixty-six samples of superficial soils were collected from the mangrove of the Botafogo River, Brazil. Mercury contents were determined and ecological and human health risks were estimated from the soil. The Hg contents exceeded the local Hg background by up to 180 times, indicating the substantial anthropic contribution that occurred in the area. Mercury concentrations followed a gradient as a function of the distance from the chlor-alkali plant, with an apparent contribution from the estuary's hydrodynamic regime. The ecological risk was considered high in all the soils evaluated, while the daily average exposure for humans, considering multiple exposure routes to soil, is below the tolerable dose recommended by the World Health Organization (WHO). However, the risk to human health was unacceptable in the estuary section closest to the plant, mainly for children. Vapor inhalation was the main route for estimating non-carcinogenic risk. The results of this study indicate a severe scenario of Hg pollution with unacceptable risks to the ecosystem and the health of human beings, especially of the communities that live from fishery and shellfish colletion and are exposed daily to soils polluted by mercury. Studies on the organomercurial species in the food chain and Hg levels in individuals living close to the estuary are warranted. This research is an important reference in the world regarding the contamination of mangrove areas by Hg., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Odontarrhena muralis is one of the most promissing plant species for Ni phytomining, and soil amendments can further increase its Ni phytoextraction ability. Here we investigated whether Ni phytomining/phytoremediation using this Ni hyperaccumulator can benefit from applying citric acid to a serpentine soil that is naturally enriched in Ni (>1000 mg kg -1 ). Synchrotron micro X-ray fluorescence (μ-SXRF) was used to image Ni and other metal distributions in whole fresh leaves of O. muralis. Leaf Ni accumulation in plants grown on citric acid-amended soil increased up to 55% while Co, Cr, Fe, Mn, and Zn concentrations were 4-, 14-, 6-, 7- and 1.3-fold higher than the control treatment. O. muralis presented high bioconcentration factors (leaf to soil concentration ratio) to Ni and Zn whereas Cr was seemingly excluded from uptake. The μ-SXRF images showed a uniform distribution of Ni, preferential localization of Co in the leaf tip, and clear concentration of Mn in the base of trichomes. The citric acid treatments strongly increased the Co fluoerescence intensity in the leaf tip and altered the spatial distribution of Mn across the leaf, but there was no difference in Ni fluorescence counts between the trichome-base region and the bulk leaf. Our data from a serpentine soil suggests that citrate treatment enhances Ni uptake, but Co is excreted from leaves even in low leaf concentrations, which can make Co phytoming using O. muralis unfeasible in natural serpentine soils., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Botafogo river estuary poses the highest Hg concentration reported for mangrove soils in Brazil. Such high contamination took place owing to the improper waste disposal for 24 years from a chlor-alkali plant nearby the estuary. Here we determined Hg concentrations in soils, mangrove plants (Rhizophora mangle and Laguncularia racemosa), and an aquatic organism (the oyster species Crassostrea rhizophorae) to assess Hg bioavailability. Besides, a sequential extraction procedure was used to separate soil Hg into five fractions: water-soluble; 'human stomach acid' soluble; organically bound; elemental Hg; mercuric sulfide. Results showed that environmentally available concentration of Hg in the mangrove soils were up to 150-fold higher than a pristine mangrove under the same geological context used as a reference. Additionally, Hg concentration in soils was also above sediment quality guidelines and Hg adverse effects towards sensitive estuarine organisms are likely. Mercury concentrations in oysters were the highest reported in Brazil, but within safety standards according to the country food security agency. It seems that Hg stocks in the studied soils are governed by organic matter and redox conditions, but changing on environmental conditions and land use can alter this balance and convert these mangrove areas from sink to source of Hg to the environment., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Soils impacted by metallurgy activities pose serious risks to the health of exposed populations, whether by ingestion of soil or contaminated food and water. The municipality of Santo Amaro, Bahia state, presents the most important case of human lead contamination in Brazil. It occurred because of inadequate slag disposal. The aims of this research were to: (i) determine the environmentally available concentrations and the distribution of As, Cd, Pb, and Zn in soil fractions; (ii) estimate the non-carcinogenic and carcinogenic risks of these elements for children; and (iii) to evaluate the use of corn (Zea mays) and castor bean (Ricinus communis) either for phytoextraction induced by chelating agents or phytostabilization. Our data demonstrated that the environmentally available concentrations of As, Cd, Pb, and Zn in soils surrounding the Pb smelting plant are among the highest that have been reported. Apart from Cd, sequential extraction demonstrated that most metals are in recalcitrant forms in the soil. However, the daily exposure of children to Pb, Zn, Cd, and As exceeded the acceptable daily intake as established by the World Health Organization. Non-carcinogenic risk modeling indicated probable adverse health effects from chronic exposure to soil Pb. The mean estimated time for remediation of the area using phytoextraction was high, ranging from 76 to 259 years; therefore, this is not a viable alternative for remediating soils in the studied area. However, good development in the contaminated soil along with restriction of the metal(oid) translocation to shoots enables castor bean to phytostabilize metal(oid)s. Additionally, castor bean cultivation may be an alternative for an economic return because of biofuel production., (Copyright © 2017. Published by Elsevier Inc.)