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While vegetable uptake of traditional metal contaminants is a well-studied pathway to human exposure and risk, a paucity of information exists on the uptake of emerging metal contaminants. This study evaluated the uptake of the Technology-critical elements (TCEs) gallium (Ga), germanium (Ge), niobium (Nb), tantalum (Ta), thallium (Tl), and rare earth elements (REEs) into lettuce cultivated in 21 European urban soils. For comparison, the uptake of cadmium (Cd) was also analysed. First, the uptake was predicted by multiplying soil concentrations with previously established bioconcentration factors (BCFs). Subsequently, multiple regression models incorporating geochemical variables as predictors were used to determine whether prediction accuracy could be improved. A "3-predictor model" incorporated soil TCE concentration, pH, and organic matter (OM), and a "7-predictor model" added data on clay content and the soil concentrations of Fe, Al, and Mn as well. With the exception of Cd, Ge, and Tl, the BCF approach provided unsatisfactory predictions (R 2  < 0.5), while the 7-predictor models yielded the best predictions, even when accounting for the greater number of predictors. While the most important predictors of uptake varied somewhat between the TCEs, the concentrations of TCEs in the soil generally explained the largest proportion of the variation. The least influential predictors in our dataset were [Mn soil ], [Fe soil ], and soil OM. Incorporating geochemical data generally improved the predictions of uptake by lettuce, and these findings underscore the need for more detailed characterisations of the uptake potential of TCEs by food plants and subsequent consequences for human health., Competing Interests: Declaration of competing interest The authors declare no conflict of interest., (Copyright © 2025 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Metalloid co-contamination such as arsenic (As) and antimony (Sb) in soils has posed a significant threat to ecological balance and human well-being. In this study, a novel magnetic graphene-loaded biochar gel (FeBG) was developed, and its remediation potential for the reclamation of AsSb spoiled soil was assessed through a six-month soil incubation experiment. Results showed that the incorporation of iron substances and graphene imparted FeBG with enhanced surface characteristics, such as the formation of a new FeO bond and an enlarged surface area compared to the pristine biochar (BC) (80.5 m 2  g -1 vs 57.4 m 2  g -1 ). Application of FeBG significantly decreased Na 2 HPO 4 -extractable concentration of As in soils by 9.9 %, whilst BC addition had a non-significant influence on As availability, compared to the control. Additionally, both BC (8.2 %) and FeBG (16.4 %) treatments decreased the Na 2 HPO 4 -extractable concentration of Sb in soils. The enhanced immobilization efficiency of FeBG for As/Sb could be attributed to FeBG-induced electrostatic attraction, complexation (Fe-O(H)-As/Sb), and π-π electron donor-acceptor coordination mechanisms. Additionally, the FeBG application boosted the activities of sucrase (9.6 %) and leucine aminopeptidase (7.7 %), compared to the control. PLS-PM analysis revealed a significant negative impact of soil physicochemical properties on the availability of As (β = -0.611, P < 0.01) and Sb (β = -0.848, P < 0.001) in soils, in which Sb availability subsequently led to a suppression in soil enzyme activities (β = -0.514, P < 0.01). Overall, the novel FeBG could be a potential amendment for the simultaneous stabilization of As/Sb and the improvement of soil quality in contaminated soils., 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.)

The escalating problem of compound arsenic (As) and cadmium (Cd) contamination in agricultural soils necessitates the urgency for effective remediation strategies. This is compounded by the opposing geochemical behaviors of As and Cd in soil, and the efficacy of biochar treatment remains unclear. This pioneering study integrated 3780 observation pairs referred from 92 peer-reviewed articles to investigate the impact of iron-modified biochar on As and Cd responses across diverse soil environments. Regarding the treatments, 1) biochar significantly decreased the exchangeable and acid-soluble fraction of As (AsF1, 20.9%) and Cd (CdF1, 24.0%) in paddy fields; 2) iron-modified biochar significantly decreased AsF1 (32.0%) and CdF1 (27.4%); 3) iron-modified biochar in paddy fields contributed to the morphological changes in As and Cd, mainly characterized by a decrease in AsF1 (36.5%) and CdF1 (36.3%) and an increase in the reducible fraction of As (19.7%) and Cd (39.2%); and 4) iron-modified biochar in paddy fields increased As (43.1%) and Cd (53.7%) concentrations in the iron plaque on root surfaces. We conclude that iron-modified biochar treatment of paddy fields is promising in remediating As and Cd contamination by promoting the formation of iron plaque., 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.)

Biochar, an environmentally friendly material, was found to passivate lead (Pb) in contaminated soil effectively. This study utilized spectroscopic investigations and partial least squares path modeling (PLS-PM) analysis to examine the impact of coconut-fiber biochar (CFB) on the translocation, accumulation, and detoxification mechanisms of Pb in soil-rice systems. The results demonstrated a significant decrease (p < 0.05) in bioavailable Pb concentration in paddy soils with CFB amendment, as well as reduced Pb concentrations in rice roots, shoots, and brown rice. Synchrotron-based micro X-ray fluorescence analyses revealed that CFB application inhibited the migration of Pb to the rhizospheric soil region, leading to reduced Pb uptake by rice roots. Additionally, the CFB treatment decreased Pb concentrations in the cellular protoplasm of both roots and shoots, and enhanced the activity of antioxidant enzymes in rice plants, improving their Pb stress tolerance. PLS-PM analyses quantified the effects of CFB on the accumulation and detoxification pathways of Pb in the soil-rice system. Understanding how biochar influences the immobilization and detoxification of Pb in soil-rice systems could provide valuable insights for strategically using biochar to address hazardous elements in complex agricultural settings., 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.)

While urban-grown vegetables could help combat future food insecurity, the elevated levels of toxic metals in urban soils need to be met with measures that minimise transfer to crops. This study firstly examines soil/dust particle inclusion in leafy vegetables and its contribution to vegetable metals (As, Ba, Cd, Co, Cr, Cu, Ni, Pb, Sb, and Zn), using vegetable, soil and dust data from an open-field urban farm in southeastern Sweden. Titanium concentrations were used to assess soil/dust adherence. Results showed that vegetables contained 0.05-1.3 wt% of adhering particles (AP) even after washing. With 0.5 % AP, an adult with an average intake of vegetables could ingest approximately 100 mg of particles per day, highlighting leafy vegetables as a major route for soil/dust ingestion. The presence of adhering particles also significantly contributed to the vegetable concentrations of As (9-20 %), Co (17-20 %), Pb (25-29 %), and Cr (33-34 %). Secondly, data from an indoor experiment was used to characterise root metal uptake from 20 urban soils from Sweden, Denmark, Spain, the UK, and the Czech Republic. Combining particle adherence and root uptake data, vegetable metal concentrations were calculated for the 20 urban soils to represent hypothetical field scenarios for these. Subsequently, average daily doses were assessed for vegetable consumers (adults and 3-6 year old children), distinguishing between doses from adhering particles and root uptake. Risks were evaluated from hazard quotients (HQs; average daily doses/tolerable intakes). Lead was found to pose the greatest risk, where particle ingestion often resulted in HQs > 1 across all assessed scenarios. In summary, since washing was shown to remove only a portion of adhering metal-laden soil/dust particles from leafy vegetation, farmers and urban planners need to consider that measures to limit particle deposition are equally important as cultivating in uncontaminated soil., 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 © 2023 The Authors. Published by Elsevier B.V. All rights reserved.)

The accuracy of environmental risk assessment depends upon selecting appropriate matrices to extract the most risk-relevant portion of contaminant(s) from the soil. Here, we applied the chelatants EDTA and tartaric acid to extract a metal-contaminated soil. Pistia stratiotes was applied as an indicator plant to measure accumulation from the metal-laden bulk solutions generated, in a hydroponic experiment lasting 15 days. Speciation modeling was used to elucidate key geo-chemical mechanisms impacting matrix and metal-specific uptake revealed by experimental work. The highest concentrations of soil-borne metals were extracted from soil by EDTA (7.4% for Cd), but their uptake and translocation to the plant were restricted due to the formation of stable metal complexes predominantly with DOC. Tartaric acid solubilized metals to a lesser extent (4.6% for Cd), but a higher proportion was plant available due to its presence mainly in the form of bivalent metal cations. The water extraction showed the lowest metal extraction (e.g., 3.9% for Cd), but the metal species behaved similarly to those extracted by tartaric acid. This study demonstrates that not all extractions are equal and that metal-specific speciation will impact accurate risk assessment in soil (water)-plant systems. In the case of EDTA, a deleterious impact on DOC leaching is an obvious drawback. As such, further work should now determine soil and not only metal-specific impacts of chelatants on the extraction of environmentally relevant portions of metal(loid)s., (© 2023. The Author(s).)

Technology-critical elements (TCEs) include most rare earth elements (REEs), the platinum group elements (PGEs), and Ga, Ge, In, Nb, Ta, Te, and Tl. Despite increasing recognition of their prolific release into the environment, their soil to plant transfer remains largely unknown. This paper provides an approximation of the potential for plant uptake by calculating bioconcentration factors (BCFs), defined as the concentration in edible vegetable tissues relative to that in cultivation soil. Here data were obtained from an indoor cultivation experiment growing lettuce, chard, and carrot on 22 different European urban soils. Values of BCFs were determined from concentrations of TCEs in vegetable samples after digestion with concentrated HNO 3 , and from concentrations in soil determined after 1) Aqua Regia digestion and, 2) diluted (0.1 M) HNO 3 leaching. For comparison, BCFs were also determined for 5 traditional metal contaminants (TMCs; As, Cd, Cu, Pb, and Zn). The main conclusions of the study were that: 1)BCF values for the REEs were consistently low in the studied vegetables;2)the BCFs for Ga and Nb were low as well;3) the BCFs for Tl were high relative to the other measured TCEs and the traditional metal contaminants; and 4) mean BCF values for the investigated TCEs were generally highest in chard and lowest in carrot. These findings provide initial evidence that there are likely to be real and present soil-plant transfer of TCEs, especially in the case of Tl. Improvements in analytical methods and detection limits will allow this to be further investigated in a wider variety of edible plants so that a risk profile may be developed., 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 © 2022 The Authors. Published by Elsevier Ltd.. All rights reserved.)

The application of organic amendments to contaminated soils is a remediation method to regulate metal(loid) leaching to waters and uptake to crops. Here, wood-derived biochar and/or green waste compost was amended to a Zn-rich agricultural soil (~ 450 mg kg -1 total Zn, derived from legacy sludge application). A pot experiment grew barley and pea crops in amended soil for 100 days, simultaneously measuring Zn, pH, and dissolved organic carbon (DOC) in pore waters and Zn uptake to plants. An assessment was made of leaching of Zn via a linked column test that recirculated soil leachates to amendments multiple times to chart the confounding impacts of pH and DOC on Zn mobility. Concentrations of Zn in pore waters in the pot test were reduced from 2 mg l -1 in soil without amendment to 1 mg l -1 following the addition of 5% (vol.) biochar and compost, which was reduced further (0.5 mg l -1 ) in the presence of crops. DOC appeared largely unaffected by soil amendment when mixed into soil, though was universally increased by the presence of the barley crop, whilst pH was variable (pH 4-6) and not clearly correlated with any intervention. Barley head mass was significantly increased after 5% biochar and both doses of compost amendment. Barley Zn content was maintained or enhanced by all soil amendments. The leaching column test revealed that biochar raised pH above that of the soil and compost amendment. Zn leachate concentrations were also reduced from after biochar amendment. Notably, compost resulted in net mobilisation of Zn from soil. This study demonstrates that the addition of biochar and compost to a Zn-rich agricultural soil was able to reduce pore water Zn considerably, especially in the presence of a barley crop. Compared to compost, biochar was the more efficient sorbent of Zn., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

The remediation of legacy metal(loid) contaminated soils in-situ relies on the addition of [organic] amendments to reduce the mobility and bioavailability of metal(loid)s, improve soil geochemical parameters and restore vegetation growth. Two vermicomposts of food and animal manure waste origin (V 1 and V 2 ) were amended to an arsenic (As) and copper (Cu) contaminated mine soil (≤1500 mg kg -1 ). Leaching columns and pot experiments evaluated copper and arsenic in soil pore waters, as well as pH, dissolved organic carbon (DOC) and phosphate (PO 4 ) concentrations. The uptake of As and Cu to ryegrass was also measured via the pot experiment, whilst recovered biochars from the column leaching test were measured for metal sorption at the termination of leaching. Vermicompost amendment to soil facilitated ryegrass growth which was entirely absent from the untreated soil in the pot test. All amendment combinations raised pore water pH by ∼4 units. Copper concentrations in pore waters from columns and pots showed steep reductions (∼1 mg L 3- ) concentrations. The uptake of As and Cu to ryegrass was also measured via the pot experiment, whilst recovered biochars from the column leaching test were measured for metal sorption at the termination of leaching. Vermicompost amendment to soil facilitated ryegrass growth which was entirely absent from the untreated soil in the pot test. All amendment combinations raised pore water pH by ∼4 units. Copper concentrations in pore waters from columns and pots showed steep reductions (∼1 mg L -1 ), as a result of V 1 compared to untreated soil (∼500 mg L 2 compared to untreated soil (∼500 mg L -1 ). Combined with an increase in DOC and PO 4 . Biochar furthest reduced Cu in pore waters from the columns to <0.1 mg L 3- , As was mobilised an order of magnitude by V 1 . Biochar furthest reduced Cu in pore waters from the columns to <0.1 mg L -1 , as a result of surface sorption. The results of this study indicate that biochar can restrict the mobility of Cu from a contaminated mine soil after other amendment interventions have been used to promote revegetation. However, the case of As, biochar cannot counter the profound impact of vermicompost on arsenic mobility., (Copyright © 2022 The Authors. Published by Elsevier Ltd.. All rights reserved.)

In remediation of metal(loid) polluted soils, it is crucial to improve soil conditions and reduce metal(loid) toxicity to permit plant growth. To do that, amendments, such as biochar, activated carbon, and redmud, can be applied to the soil. Their effects are dependent on their type and properties. The aims of this study were thus to evaluate the potential of diverse biochars, activated carbons, and redmuds to reduce phytotoxicity of a former mine technosol polluted with As and Pb. Two pots experiments were set up. The first one applied on Pontgibaud technosol ten biochars, eight activated carbons, and three redmuds, at 2% for the biochars and activated carbons and 1% for the redmud. Soil pore water properties (pH, electrical conductivity), metal(loid) mobility, and Phaseolus vulgaris growth were monitored. In a second experiment, the five best amendments, one redmud associated with two biochars and two activated carbons, selected based on their ability to improve soil conditions, immobilize metal(loid)s and improve plant growth, were applied. The same plant species was used and soil and plant parameters were measured. Results demonstrated that not all amendments were capable of ameliorating soil conditions and reducing soil phytotoxicity. Moreover, the five selected amendments (biochars from oak bark sapwood and bamboo, activated carbons from vegetal feedstock chemically activated and physically activated, modified redmud) showed good sorption capacity towards Pb, with maximum sorption capacity between 63 and 217 mg g -1 , depending on the amendment, and their combined application led to better soil properties improvement than the single amendments. However, plant growth was only ameliorated further than a single application in the redmud-biochar combination but not in the association of redmud with activated carbon. This study is one of the first to deliver a rapid phytotoxicity test screening demonstrating that redmud associated with particular biochar could be beneficial in reducing the phytotoxicity of technosol polluted with As and Pb and thus allow plant growth and a phytomanagement process., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

The United Nations estimates the rate of deforestation over 10 million hectares per year, with additional infested wood available due to drought, bark beetle calamity and other damage vectors. Processing the hard-to-reach infested wood into biochar via mobile pyrolysis units seems to be a good option for fire prevention. However, since most biochar is currently produced mainly from biological waste, there is not enough experience with wood biochar on a large scale. Review of current knowledge, followed by techno-economic assessment reveals that following the chemical composition of the feedstock, wood biochar outperforms other types of biochar in terms of high porosity. Therefore, wood biochar shows excellent results in increasing the amount of plant-available water content in soil and appears to be an excellent tool for recycling nutrients (especially into plant-available forms of phosphorus and nitrogen). The overall positive effects of biochar application change from abiotic to biotic over time because as it decays, many of its physical properties disappear, but it can boost soil microbial communities on which soil fertility depends. As global climate change creates a wide range of factors that damage forest cover, wood biochar consequently represents untapped potential in the field of soil, nutrient, and energy management., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Lead (Pb) and copper (Cu) contamination seriously threatens agricultural production and food safety. This study aims to investigate Pb and Cu induced hormetic effect and toxicity mechanisms in lettuce (Lactuca sativa L.) and establish reliable empirical models of potentially toxic elements (PTEs) transfer in the soil-plant system. The content and distribution of Pb and Cu at subcellular levels in lettuce plants were examined using inductively coupled plasma-mass spectrometry, differential centrifugation and micro-X-ray fluorescence spectroscopy. The PTE-loaded capacity of Pb that ensures food safety was lower than that of Cu in the studied soil, but the PTE-loaded capacity of Pb that limits yield was higher than that of Cu. Lead in lettuce roots mainly accumulated in the cell wall (41%), while Cu mainly accumulated in the vacuoles (46%). The Pb and Cu were primarily distributed in the radicle of lettuce seeds under severe PTE stress, resulting in no seed development. Iron plaque formed on the root surface of lettuce seedlings and sequestered Pb and Cu via chelation. At the same concentration, lettuce was less tolerant to Cu in contaminated soil than Pb due to the higher activity of Cu ions in the soil. Lead was more phytotoxic to lettuce than Cu, however, since the radicle emerged from the seed under severe Cu levels, while it did not protrude under severe Pb levels. The potentially damaging effect of Pb in the visually healthy lettuce appeared to be higher than that of Cu under the same soil contamination level., 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 B.V. All rights reserved.)

Two metal(loid) contaminated agricultural soils were amended with grape stalk (wine production by-product)-derived biochar as well as its pre-pyrolysed origin material, to investigate their geochemical impacts on As, Cr, Cu and Zn. Detailed physico-chemical evaluation combined with a column leaching test determined the retention of metal(loid)s from soil solution by each amendments. A pot experiment measured metal(loid)s in soil pore water and their uptake to ryegrass when the amendments were mixed into soils at 1 and 5% (w/w). Total Cr and Zn concentrations were reduced furthest in column leachates by the addition of raw material and biochar respectively, compared to the untreated soil; Cr(III) was the predominant specie initially due to rapid acidification of leachates and organic complexation resulting from raw material addition. Loadings of metal(loid)s to the amendments recovered from the post-leached columns were in the order Cu » Zn > Cr ≈ As. In the pot test ryegrass Cr uptake was initiated by the addition of both amendments, compared to the untreated soil, whereas only biochar addition resulted in significant increases in Zn uptake, explained by its significant enhancement of ryegrass biomass yield, especially at 5% dosage; raw material addition significantly decreased biomass yields. Inconsistent relationships between pore water parameters and ryegrass uptake were common to both soils investigated. Therefore, whilst both amendments modified soil metal(loid) geochemistry, their effects differed fundamentally; in environmental risk management terms these results highlight the need to investigate the detailed geochemical response of contaminated soils to diverse organic amendment additions., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Heavy metal(loid) rich ash (≤10,000 mg kg -1 total As, Cr, Cu and Zn) originating from the combustion of contaminated wood was subjected to several experimental procedures involving its incorporation into an upland pasture soil. Ash was added to soil that had been prior amended with local cattle manure, replicating practices employed at the farm scale. Metal(loid) concentrations were measured in soil pore water and ryegrass grown on soil/manure plus ash mixtures (0.1-3.0% vol. ash) in a pot experiment; toxicity evaluation was performed on the same pore water samples by means of a bacterial luminescence biosensor assay. Thereafter a sequential extraction procedure was carried out on selected soil, manure and ash mixtures to elucidate the geochemical association of ash derived metal(loid)s with soil constituents. Predictive modelling was applied to selected data from the pot experiment to determine the risk of transfer of As to meat and milk products in cattle grazing pasture amended with ash. The inclusion of manure to soils receiving ash reduced phyto-toxicity and increased ryegrass biomass yields, compared to soil with ash, but without manure. Elevated As and Cu concentrations in pore water and ryegrass tissue resulting from ash additions were reduced furthest by the inclusion of manure due to an increase in their geochemical association with organic matter. Zinc was the only measured metal(loid) to remain uniformly soluble and bioavailable regardless of the addition of ash and manure. Risk modelling on pot experimental data highlighted that an ash addition of >1% (vol.) to this pasture soil could result in As concentrations in milk and meat products exceeding acceptable limits. The results of this study therefore suggest that even singular low doses of ash applied to soil increase the risk of leaching of metal(loid)s and intensify the risk of As transfer in the food chain., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

The aim of our study was to compare the sorption properties of a contaminated soil before and after two types of phytoremediation (natural phytoextraction vs. phytostabilization with dolomite limestone (DL) application). Soil from a pot experiment in controlled greenhouse conditions performed for two vegetation periods was used for the study. Lead, as the main contaminant in the studied soil, was easily desorbed by Cu, especially due to the increased affinity of Cu for soil organic matter; hence input of Cu to the studied soil can present another environmental risk in soils contaminated with other metals (such as Pb). In addition, the sorption behavior of chosen metals from single-element solutions differed from multielement solutions. The obtained results proved the different sorption behavior of metals in the single-element solution compared to the multi-element ones. Soil sorption behavior of Cd, Cu, and Zn decreased with the presence of the competitive metals; nevertheless, Pb sorption potential was not influenced by other competitive metals. Natural phytoextraction showed no significant effect on the sorption of Cd, Cu, Pb, and Zn onto the soil On the other hand, phytostabilization associated with DL application improved the soil sorption efficiency of all chosen metals, especially of Cu.