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The number of studies using various stable isotope systems for tracing contamination sources and various biogeochemical processes is rapidly rising due to the increased availability of the techniqu...

The Atalanti basin is an intensively cultivated area in central Greece, facing groundwater quality deterioration threats due to natural and anthropogenic-related contamination sources. A combination of statistical and hydrogeochemical techniques, and stable isotope compositions (δ

During production of γ-hexachlorocyclohexane (γ-HCH), thousands of tons of other isomers were synthesized as byproducts, and after dumping represent sources of contamination for the environment. Several microbes have the potential for aerobic and anaerobic degradation of HCHs, and zero-valent iron is an effective remediation agent for abiotic dechlorination of HCHs, whereas the combination of the processes has not yet been explored. In this study, a sequence of anoxic/oxic chemico-biological treatments for the degradation of HCHs in a real extremely contaminated soil (10-30 g/kg) was applied. Approximately 1500 kg of the soil was employed, and various combinations of reducing and oxygen-releasing chemicals were used for setting up the aerobic and anaerobic phases. The best results were obtained with mZVI/nZVI, grass cuttings, and oxygen-releasing compounds. In this case, 80 % removal of HCHs was achieved in 129 days, and 98 % degradation was achieved after 1106 days. The analysis of HCHs and their transformation products proved active degradation when slight accumulation of the transformation product during the anaerobic phase was followed by aerobic degradation. The results document that switching between aerobic and anaerobic phases, together with the addition of grass, also created suitable conditions for the biodegradation of HCHs and monochlorobenzene/benzene by microbes.

Data mining and knowledge discovery by machine learning (ML) have recently come into application in environmental remediation, especially the exploration for the multifactorial process such as hexavalent chromium [Cr(VI)] removal by iron-biochar composite (Fe-BC). The Cr(VI) removal capacity of Fe-BC was concurrently controlled by impregnated iron species (Fe0/Fe2+/Fe3+), carbon properties, and iron-carbon interactions, while the current lab-scale research could hardly untangle the overall relationships with the Cr(VI) removal experiments of one or several Fe-BCs under different research frameworks. Herein, we investigated the impacts of various microscopic material properties of Fe-BC on aqueous Cr(VI) removal by ML approach and highlighted the variations of biochar properties after iron impregnation. Our results suggested that the direct impacts of impregnated-iron contents on the Cr(VI) removal were limited, possibly related to undistinguished Fe species in the ML models, in which the roles of different iron species on Cr(VI) removal might be counteracted. Instead, the impacts of impregnated iron on the Cr(VI) removal were embodied indirectly by altering the biochar properties. Surface oxygen-containing functional groups (SOFGs) contents on biochar played a pivotal role in Cr(VI) removal according to the ML models. The condensed polyaromatic carbon matrices of BC and Fe-BC with a high content of non-polar carbon were also proved to be conducive to Cr(VI) removal. The ML models developed in this study consider surface functionalities information of BC and Fe-BC and offer a more accurate prediction for Cr(VI) removal, and the information mining behind models can act as a vital reference for the rational design of engineered biochar to remove aqueous Cr(VI).

International audience; The current demand for alternative water sources requires the incorporation of low-cost composites in remediation technologies; these represent a sustainable alternative to more expensive, commercially used adsorbents. The main objective of this comprehensive field-scale study was to incorporate the layered double hydroxides (LDHs) into the hybrid biochar-based composites and apply an innovative material to remediate As/Sb-rich mine waters. The presence of hydrous Fe oxides (HFOs) within the composite enhanced the total adsorption efficiency of the composite for As(V) and Sb(V). The kinetic data fitted to a pseudo-second order model. Equilibrium experiments confirmed that the composite had a stronger interaction with As(V) than with Sb(V). The efficient removal of As(V) from mine water was achieved in both batch and continuous flow column systems, reaching up to 98% and 80%, respectively. Sb(V) showed different behavior to As(V) during mine water treatment, reaching adsorption efficiencies of up to 39% and 26% in batch and column experiments, respectively. The migration of Sb(V) in mine water was mostly attributed to its dispersion before it was able to show affinity to the composite. In general, the proposed column technology is suitable for the field remediation of small volumes of contaminated water, and thus has significant commercial potential.

Industrial sites affected by anthropogenic contamination, both past and present-day, commonly have intricate pollutant patterns, and source discrimination can be thus highly challenging. To this goal, this paper presents a novel approach combining multivariate statistics and environmental forensic techniques. The efficiency of this methodology was exemplified in a severely polluted estuarine area (Aviles, Spain), where factor analysis and clustering were performed to identify sub-areas with distinct geochemical behaviour. Once six clusters were defined and a pollution index applied, forensic tools revealed that the As speciation, Pb isotopes, and PAHs molecular ratios were useful to categorise the cluster groups on the basis of distinct pollution sources: Zn-smelting, coaly particles and waste disposal. Overall, this methodology offers valuable insight into pollution sources identification, which can be extended to comparable scenarios of complexly polluted environmental compartments. The information gathered using this approach is also important for the planning of risk assessment procedures and potential remediation strategies.

Oxidative extraction has become an economically viable option for recycling lithium (Li) from spent lithium iron phosphate (LiFePO

Nano zero-valent iron (nZVI) is a promising material for remediating metal(loid)-contaminated soils, but its aging in the soil ecosystem (unlike intensively studied aqueous systems) and interaction with soil microbial communities have not been resolved. In this study, three types of nZVI particles (bare nZVI, nZVI coated with carboxymethyl cellulose (CMC), or polyacrylic acid (PAA)) were incubated in soils with different microbial community compositions (realized by γ-radiation), and their aging was investigated using complementary microspectroscopic analyses. In addition, the soil microbial community in association with nZVI aging was assessed by employing DNA sequencing by using Illumina MiSeq. The results revealed a drastic morphological change of nZVI, which was transformed mainly into magnetite with a rough morphology. CMC coating decreased nZVI aging, whereas PAA coating accelerated it and facilitated magnetite, goethite and lepidocrocite formation. The γ-radiation induced soil microbial community change possibly slowed down nZVI oxidation (especially for bare nZVI). Iron-reducing/oxidizing bacteria (Bacillus, Shewanella, and Sediminibacterium) and fungal strains with a capacity for siderophore production may participate in nZVI aging. In return, nZVI presence and aging altered soil microbial communities. This study revealed the transformation of nZVI particles into Fe (oxy)hydroxides during aging in the soil ecosystem and their bilateral interactions with the soil microbial community, thus contributing to the assessment of nZVI use in soil remediation.

The chemical stabilization, or immobilization, of trace elements (metals and metalloids; TE) in contaminated soil has been studied for decades. A vast number of scientific publications are available on the method performance in laboratory settings, reporting that the application of various soil amendments to contaminated soil reduces TE mobility, bioavailability and toxicity. The most commonly used soil amendments include organic matter, iron oxides, phosphates, ashes, and lately biochar, alone or in combination with each other and/or lime. Most of the implemented field studies show a certain degree of improvement in soil and/or vegetation status following amendment. Regardless the positive performance of the technique in the laboratory, field validations and demonstrations remain scarce. The establishment of a field experiment often involves permits from authorities and agreements with site owners, both of which are considerably more time-consuming than laboratory tests. Due to conservative institutional structures, public authorities have been slow to adopt alternative remediation technologies, especially when the total TE concentration in soil remains the same and all of the associated risks are not yet convincingly described. For this reason, researchers should also focus on enhancing public knowledge of alternative remediation techniques so that future projects which aim to demonstrate the effectiveness of in situ immobilization techniques under natural conditions will be supported.

International audience; Cadmium (Cd) isotopes are known to fractionate during complexation with various environmentally relevant surfaces and ligands. Our results, which were obtained using (i) batch experiments at different Cd concentrations, ionic strengths, and pH values, (ii) modeling, and (iii) infrared and X-ray absorption spectroscopies, highlight the preferential enrichment of light Cd isotopes bound to humic acid (HA), leaving the heavier Cd pool preferentially in the solution (Δ114/110CdHA-Cd(aq) of -0.15 ± 0.01‰). At high ionic strengths, Cd isotope fractionation mainly depends on its complexation with carboxylic sites. Outer-sphere complexation occurs at equilibrium together with inner-sphere complexation as well as with the change of the first Cd coordination and its hydration complexes in solution. At low ionic strengths, non-specific Cd binding induced by electrostatic attractions plays a dominant role and promotes Cd isotope fractionation during complexation. This significant outcome elucidates the mechanisms involved in HA-Cd interactions. The results can be used during (i) fingerprinting the available Cd in soil solution after its complexation with solid or soluble natural organic matter and (ii) evaluate the contribution of Cd complexation with organic ligands and phytoplankton-derived debris vs. Cd assimilation by phytoplankton in seawater.

International audience; Metal isotopes are versatile pollutant source trackers, but biogeochemical processes can overprint or alter the original source isotopic fingerprint and thus hinder contamination tracing. Here, we explore Fe isotope systematics for the complete range of natural and metallurgical processes related to Ni lateritic ores from Barro Alto, Brazil, to assess its potential as a tracer in polluted lateritic soil contexts developed in an ultramafic system.The homogeneous δ57Fe values from protolith to soil confirmed that no significant Fe isotopic variation occurred during the formation of the deep lateritic profile. In addition, no Fe isotopic fractionation was found during the smelting process. Although the δ57Fe values resulting from mining activities fall within the range of terrestrial sample signatures, the conservation of the δ57Fe values from the ores to the by-products is an advantage for tracing anthropogenic sources when (i) the pyrometallurgical plant uses feeding material with Fe ores imported from other geological formations exhibiting different δ57Fe values and/or (ii) the by-products are transported or dispersed to other locations with different δ57Fe signatures in the topsoil.

Electroactive Fe-biochar has attracted significant attention for As(III)/Cr(VI) immobilization through redox reactions, and its performance essentially lies in the regulation of various Fe/C moieties for desired redox performance. Here, a series of Fe-biochar with distinct Fe/C speciation were rationally produced via two-step pyrolysis of iron minerals and biomass waste at 400-850 °C (BCX-Fe-Y, X and Y represented the first- and second-step pyrolysis temperature, respectively). The redox transformation of Cr(VI) and As(III) by Fe-biochar was evaluated in simulated wastewater under oxic or anoxic conditions. Results showed that more effective Cr(VI) reduction could be achieved by BCX-Fe-400, while a higher amount of As (III) was oxidized by BCX-Fe-850 under the anoxic environment. Besides, BCX-Fe-400 could generate more reactive oxygen species (e.g.

Understanding the links between sources of magnetic particles and bioaccessibility of metal(loids) in environmental sampling media is crucial for better evaluating human health risks, although relevant information in the scientific literature is scarce. Here, soil, road and house dust samples from a heavy industrial area in Greece were characterized in a multidisciplinary study combining magnetic measurements, SEM/EDS analyses, bioaccessibility measurements and Pb isotopic analyses of bioaccessible Pb. The oral and inhalable bioaccessible fractions of As, Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn were assessed by applying simulated gastric and lung solutions. SEM/EDS analysis revealed the abundant presence of anthropogenic Fe-containing spherules of industrial origin in all sampling media, often containing minor contents of Cr, Cu, Mn, Pb and Zn. The inhalation bioaccessibility (%) in all environmental compartments was higher than the oral one for most elements analyzed in the present study. Clear associations between magnetic susceptibility and bioaccessible amounts of most of analyzed elements were encountered for the soil and road dust. The isotopic analyses of bioaccessible Pb showed that there are significant differences in the isotopic ratios between total and bioaccessible Pb. We conclude that Pb solubilized by the simulated gastric and lung extractions is principally anthropogenic, representing a mixture of industrial Pb and Pb related to the past usage of leaded petrol. Low values of 206Pb/207Pb were accompanied by high bioaccessible contents of Cd, Pb and Zn indicating that anthropogenic (mostly industrial) sources exert influence on the bioaccessible forms of these metals. Coupling magnetic and bioaccessibility measurements with stable isotopic technique of bioaccessible Pb is more reliable for determining Pb and other metal sources with high oral and inhalation bioaccessibility.

Two Poaceae species, Agrostis capillaris and Festuca rubra, were selected for their potential as phytostabilizing plants in multicontaminated soils. These species are resistant to contamination and maintain high concentrations of contaminants at the root level. Nanoscale zero-valent iron (nZVI) is an engineered nanomaterial with the ability to stabilize metal(loid)s in soils, its potential toxicological effects in the selected species were studied in a germination test using: (i) control variant without soil, (ii) soil contaminated with Pb and Zn, and (iii) contaminated soil amended with 1% nZVI, as well as in an hydroponic experiment with the addition of nZVI 0, 25, 50 and 100 mg L&minus, 1. nZVI had no negative effects on seed germination or seedling growth, but was associated with an increase in shoot growth and reduction of the elongation inhibition rate (root-dependent) of F. rubra seedlings. However, applications of nZVI in the hydroponic solution had no effects on F. rubra but A. capillaris developed longer roots and more biomass. Increasing nZVI concentrations in the growing solution increased Mg and Fe uptake and reduced the Fe translocation factor. Our results indicate that nZVI has few toxic effects on the studied species.

A generic hydrous Fe oxide surface is often used in surface complexation modeling for predicting metal behavior in aqueous and soil environments. However, this approach may lead to incorrect results because there are many different naturally-occurring Fe(III) (oxyhydr)oxide mineral phases in the environment, each exhibiting distinct adsorption characteristics. This work presents a consistent dataset of surface complexation model parameters valid at 25 °C and 1 bar that characterize the adsorption of selected divalent metals (Cd, Cu, Pb, Zn) onto environmentally relevant Fe(III) (oxyhydr)oxides, i.e., FeOOH and Fe2O3 polymorphs (goethite, hematite, lepidocrocite, maghemite), at varying metal concentrations and ionic strengths. The parameters were obtained using a simple and unified workflow and are readily implementable into widely used geochemical codes, such as Visual MINTEQ, MINEQL+, and ORCHESTRA, enabling quantification of metal adsorption onto a range of Fe(III) oxides in various aqueous environments.

Nano zero-valent iron (nZVI) has great potential in the remediation of metal(loid)-contaminated soils, but its efficiency in metal(loid) stabilization in the plant-microbe continuum is unclear. This study investigated nZVI-mediated metal(loid) behavior in the arbuscular mycorrhizal (AM) fungal-maize ( Zea mays L.) plant association. Plants with AM fungal inoculation were grown in metal(loid)- (mainly Zn and Pb) contaminated soils (Litavka River, Czech Republic) amended with/without 0.5% (w/w) nZVI. The results showed that nZVI decreased plant metal(loid) uptake but inhibited AM development and its function in metal(loid) stabilization in the rhizosphere. AM fungal inoculation alleviated the physiological stresses caused by nZVI and restrained nZVI efficiency in reducing plant metal(loid) uptake. Micro proton-induced X-ray emission (μ-PIXE) analysis revealed the sequestration of Zn (possibly through binding to thiols) by fungal structures in the roots and the precipitation of Pb and Cu in the mycorrhizal root rhizodermis (possibly by Fe compounds originated from nZVI). XRD analyses further indicated that Pb/Fe mineral transformations in the rhizosphere were influenced by AM and nZVI treatments. The study revealed the counteractive effects of AM and nZVI on plant metal(loid) uptake and uncovered details of metal(loid) behavior in the AM fungal-root-nZVI system, calling into question about nZVI implementation in mycorrhizospheric systems.

Comprehensive mechanistic and modeling approaches are needed to effectively evaluate sorption of metal ions from aqueous solutions. However, such a complex study using layered double hydroxides has not yet been presented. Therefore, adsorption modeling was performed coupled with solid state analyses describing the mode of zinc and lead removal by magnesium-iron layered double hydroxides, and an excellent removal efficiency for both metal ions was observed. The maximal adsorbed concentration, as established by the Langmuir model, increased with the increasing magnesium/iron molar ratio. The pH-dependent sorption was fitted by the diffuse layer model, which described the formation of monodentate inner-sphere complexes, indicating strong binding between metal ions and the layered double hydroxides surface. Based on the solid state analyses of materials with high surface concentrations of zinc (1.44 mmol g−1) and lead (1.65 mmol g−1), respectively, the whole sorption mechanism was also influenced by other processes, i.e., precipitation (lead) and surface accumulation/precipitation/isomorphic substitution (zinc). Transmission electron microscopy-based elemental mapping showed a heterogeneous distribution of zinc and lead on the surface of particles. Low-temperature Mossbauer spectra were nearly identical for the studied materials before/after zinc and lead sorption indicating no structural changes in incorporated iron. Generally, we suggest that these layered double hydroxides are highly effective sorbents for metal ions from aqueous solutions. Furthermore, we propose a comprehensive mechanistic/modeling approach as a powerful tool for describing the mechanism of metal ions binding on layered double hydroxides in contaminated waters.

Various stabilizing amendments are used and tested for immobilization of metals and metalloids in contaminated soils. Although the soil moisture level may fundamentally drive these stabilizing agents' performance, most laboratory studies do not provide consistent data for different moisture regimes. In addition, the possible influence of applied stabilizing materials on the soil's physical and hydraulic properties and associated changes in soil chemistry is virtually unknown. For this reason, this study aimed to investigate the stabilizing potential of two immobilizing agents (amorphous Mn oxide – AMO, and AMO-biochar composite – AMOchar) toward As, Cd, Pb, and Zn in two contaminated soils at two different soil moisture regimes (unsaturated and saturated conditions). At the same time, changes in saturated hydraulic conductivity (Ks), soil swelling, and saturated water content were evaluated. The soil moisture conditions essentially affected all the studied parameters, including both physical and chemical properties. Under the saturated condition, the contents of As, Cd, Pb and Zn in soil solution were elevated compared to the unsaturated condition. The stabilizing effectiveness of the AMO/AMOchar strongly depended on the moisture regime (saturated vs. unsaturated conditions) and type of contaminant based on its binding mechanism in soil. The release of Cd and Zn was reduced by AMO and AMOchar after 10 weeks under both moisture regimes due to an induced pH increase, decreasing the contents of Cd and Zn in soil solution in maximum by 87% (AMOchar, saturated conditions) and 74% (AMO, unsaturated conditions), respectively. Under the saturated conditions, only AMO was effective at immobilizing Pb and As, decreasing their release by 58% and 53%. The application of AMOchar led under full saturation to a significant redox (Eh) drop (minimum value of 181 mV), followed by the dissolution of soil Fe oxides and the associated release of bound Pb and As. As a result, the contents of Pb and As in soil solution increased compared to control by 78% and 248%, respectively. This decline in Eh may be a consequence of the observed AMOchar swelling. However, additional factors, such as changes in the soil microbiology, probably contributed to the overall effect. The study demonstrates the fundamental role of soil moisture content in the stabilizing agents' performance and highlights the need for future interdisciplinary studies aiming at physical/geochemical/biological aspects of soil systems together.

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 (~65–93% of the control) except for one sample with the lowest solution pH. Nano zero-valent iron was also successful in Sb immobilisation (~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 (~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.

Several efficient stabilizing amendments have been recently proposed for the remediation of metal(loid)-contaminated soils. However, information on their interactions with plants, which is a crucial factor in soil environments, are still scarce. An amorphous manganese oxide (AMO) synthesized from organic compounds and nano zerovalent iron (nZVI) have been previously tested as promising stabilizing agents usable both for the stabilization of metals and As. Experiments with rhizoboxes were performed in order to evaluate their influence on the mobility of metal(loid)s in the bulk soil and rhizosphere of sunflower (Helianthus annuus L.) together with their impact on metal uptake and biomass yield. Generally, AMO proved more efficient than nZVI in all stages of experiment. Furthermore, the AMO effectively reduced water- and 0.01 M CaCl2-extractable fractions of Cd, Pb and Zn. The decreased bioavailability of contaminating metal(loid)s resulted in significant increase of microbial activity in AMO-amended soil. Together with metal(loid) extractability, the AMO was also able to significantly reduce the uptake of metals and ameliorate plant growth, especially in the case of Zn, since this metal was taken up in excessive amounts from the control soil causing strong phytotoxicity and even death of young seedlings. On the other hand, AMO application lead to significant release of Mn that was readily taken up by plants. Resulting Mn concentrations in biomass exceeded toxicity thresholds while plants were showing emergent Mn phytotoxicity symptoms. We highlight the need of such complex studies involving plants and soil biota when evaluating the efficiency of stabilizing amendments in contaminated soils.

The use of Ni and Cu isotopes for tracing contamination sources in the environment remains a challenging task due to the limited information about the influence of various biogeochemical processes influencing stable isotope fractionation. This work focuses on a relatively simple system in north-east Norway with two possible endmembers (smelter-bedrock) and various environmental samples (snow, soil, lichens, PM10). In general, the whole area is enriched in heavy Ni and Cu isotopes highlighting the impact of the smelting activity. However, the environmental samples exhibit a large range of δ60Ni (−0.01 ± 0.03‰ to 1.71 ± 0.02‰) and δ65Cu (−0.06 ± 0.06‰ to −3.94 ± 0.3‰) values which exceeds the range of δ60Ni and δ65Cu values determined in the smelter, i.e. in feeding material and slag (δ60Ni from 0.56 ± 0.06‰ to 1.00 ± 0.06‰ and δ65Cu from −1.67 ± 0.04‰ to −1.68 ± 0.15‰). The shift toward heavier Ni and Cu δ values was the most significant in organic rich topsoil samples in the case of Ni (δ60Ni up to 1.71 ± 0.02‰) and in lichens and snow in the case of Cu (δ65Cu up to −0.06 ± 0.06‰ and −0.24 ± 0.04‰, respectively). These data suggest an important biological and biochemical fractionation (microorganisms and/or metal uptake by higher plants, organo-complexation etc.) of Ni and Cu isotopes, which should be quantified separately for each process and taken into account when using the stable isotopes for tracing contamination in the environment.

We studied Fe-Mn concentric nodules from Cutanic Luvisol in the northern part of Namibia, where agricultural fields are irrigated with the drainage water from the Kombat Cu-Pb-(Zn) mine (pH 7, metal concentrations in μg l − 1 : Fe 7, Mn 10, Zn 7, Cu 18). Concentric nodules (0.5–2 cm in size) were mostly found towards the bottom of the sampled soil profile (Btcg2 horizon, depth 100–120 cm). Comparisons with the bulk chemical composition of the soil matrix showed that Fe-Mn nodules were enriched in metals, metalloids and other trace elements (with a few exceptions, enrichment factors varied in the range 1.3–6.4). The concentrations of the elements of interest in the Fe-Mn nodules were as follows (mg kg − 1 ): As 23.1, Ba 3840, Cd 6.83, Cu 450, Pb 597, Zn 137. The X-ray diffraction analysis indicated that the nodules were composed of quartz, goethite, hematite, illite/mica, pyrochroite, lithiophorite and birnessite. The scanning electron microscopy (SEM) observations confirmed that the internal structure of the nodules with concentric rings reflected seasonal changes in the redox conditions. Spot analyses and X-ray elemental maps performed using energy/wavelength dispersion spectrometry (EDS/WDS) showed that the concentrations of metalloids were rather low except for the slightly elevated Ba concentrations, which were observed only within the Mn oxide-rich zones. Selective extractions were used to understand the partitioning of trace elements within the individual phases. Whereas Mn oxides sequestered the majority of the Cd (up to 98%), Ba, Pb and rare earth elements (REEs) (up to 78%), other metals such as Cu and Zn exhibited much lower values (47–65%) and, together with oxyanionic species (As, Cr, V), were also significantly bound to Fe oxides. The pH-static leaching test conducted in the pH range 2–12 indicated that the majority of the trace elements were mostly leached under acidic conditions with the exception of As, which was highly solubilized at pH 12 (up to 17%). Whereas Ba, Cd, Cu and Zn were significantly released under acidic conditions (up to 12%), the leaching of Pb was almost negligible over the entire pH range. Our results show that Fe-Mn nodules act as significant traps for trace metals in Luvisols irrigated by mine water. However, an abrupt decrease in the pH and changes in the redox conditions may cause the dissolution of Fe-Mn nodules and subsequent release of contaminants into the soil system.

Mobilization of micro-and macronutrients and their uptake by Zea mays L. and Triticum aestivum L. in response to EDTA additions to risk metal contaminated agricultural soil was monitored over a three year period on the field scale. EDTA addition effectively increased the mobility of total water-soluble micronutrients (Cu, Fe, Mn) and macronutrients (Ca, Mg, P) in soil extracts. Mobilization was highest in the first year and decreased strongly over time. Elements with a high affinity for EDTA (Cu and Fe) were slightly increased two years after application of EDTA down the soil profile, indicating the possibility of nutrient discharge into the groundwater and thereby a loss of soil fertility. Nutrient concentrations in grain and straw of T. aestivum were higher for Cu and Fe up to two years after EDTA application whereas Mg concentrations were lower.

Samples of lichens, snow and particulate matter (PM10, 24 h) are used for the source identification of air pollution in the heavily industrialized region of Ostrava, Upper Silesia, Czech Republic. An integrated approach that uses different environmental samples for metal concentration and Pb isotope analyses was applied. The broad range of isotope ratios in the samples indicates a combination of different pollution sources, the strongest among them being the metallurgical industry, bituminous coal combustion and traffic. Snow samples are proven as the most relevant indicator for tracing metal(loid)s and recent local contamination in the atmosphere. Lichens can be successfully used as tracers of the long-term activity of local and remote sources of contamination. The combination of PM10 with snow can provide very useful information for evaluation of current pollution sources.

Recent investigations show that carbon-based and metal-based engineered nanomaterials (ENMs), components of consumer goods and agricultural products, have the potential to build up in sediments and biosolid-amended agricultural soils. In addition, reports indicate that both carbon-based and metal-based ENMs affect plants differently at the physiological, biochemical, nutritional, and genetic levels. The toxicity threshold is species-dependent and responses to ENMs are driven by a series of factors including the nanomaterial characteristics and environmental conditions. Effects on the growth, physiological and biochemical traits, production and food quality, among others, have been reported. However, a complete understanding of the dynamics of interactions between plants and ENMs is not clear enough yet. This review presents recent publications on the physiological and biochemical effects that commercial carbon-based and metal-based ENMs have in terrestrial plants. This document focuses on crop plants because of their relevance in human nutrition and health. We have summarized the mechanisms of interaction between plants and ENMs as well as identified gaps in knowledge for future investigations.

In this study, samples of soil and particulate matter obtained from the highly industrialized region of Ostrava, Czech Republic, are used for the toxicity evaluation of the selected metal(loid)s (Cd, Cr, Cu, Ni, Pb, Zn, As). We investigated the samples from sites supposedly affected the most by the local pollution sources using mineralogical techniques (XRD, SEM/EDS) to understand the solid speciation of the contaminants as the crucial factor affecting their release. Although the bulk composition was defined by common silicates and oxides that are rather resistant to leaching, the presence of tiny Ni, Pb, and/or Zn sulfate-like droplets indicated a potential increase of the solubility of these metals. In vitro tests simulating gastric and lung fluids were used to assess the exposure risk for humans, as well as metal(loid) bioaccessibility. Based on the results, the potential risk for the observed age group (3-year-old children) could be recognized, particularly in the cases of As, Pb and Cd for both oral and inhalation exposure. Arsenic exhibits high bioaccessibility (7.13–79.7%, with the median values of 10.6 and 15.6 for SGL and SLF, respectively), high daily intake (1.4- to 8.5-fold higher than the tolerable daily intake) and high concentrations in atmospheric PM10 (2.5 times the tolerable concentration in air). In contrast, Ni exceeded tolerable concentrations in the atmosphere up to 20-fold, but its bioaccessibility remained relatively low (0.1–22%), and Ni did not pose a major threat to human health. Cadmium, Pb and As originating from industrial activities and domestic heating have been suggested to be the most important pollutants (tolerable daily intake was exceeded by up to 74-, 34- and 8-fold for Cd, Pb and As, respectively).

The remediation of a soil contaminated with Zn, Pb and Cd was tested by using biochar (BC), nano zero-valent iron (nZVI) and a combination of these two (BC + nZVI). Each amendment was individually applied to the soil at 2 wt%. We tested the influence of (i) the used amendments, (ii) time, and (iii) soil moisture conditions on the metal availability and soil physico-chemical parameters using various extraction methods, as well as soil pore water samplings. We found that metal availability was mainly affected by pH under the influence of time and water content. Among the tested treatments, BC was the most successful, resulting in the lowest amounts of the target metals in the pore water and the smallest temporal changes in metal concentrations and pH in the soil. The use of nZVI efficiently decreased water-extractable Pb in the short- and long-term. The BC + nZVI treatment also yielded promising results regarding the immobilisation of the studied metals. Time provoked a general decrease in pH, which occasionally increased the available metal concentrations. Raising the soil water content increased the pH and subsequently lowered the available metal concentrations in the pore water. The mechanisms of metal stabilisation were further investigated by SEM/EDS. The results indicated that the used soil amendments enhanced the binding of Zn, Pb, and Cd on Fe/Mn/Al oxides/hydroxides, which in turn resulted in the stabilisation of the target metals.

In this study, the importance of Sb behavior under different pH conditions has been addressed with respect to its stabilization in aqueous solutions using Mg-Fe layered double hydroxides (LDHs). The Sb(V) adsorption onto Mg-Fe LDHs was performed at different initial Sb(V) concentrations and pH values (pH 5.5, 6.5 and 7.5). The removal rate and the maximal adsorbed amount increased with decreasing pH values. Moreover, the surface complexation modeling (SCM) predicted preferable formation of monodentate mononuclear and bidentate binuclear complexes on the Mg-Fe LDH surface. Spectroscopic (X-ray diffraction analysis, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy) and microscopic (scanning electron microscopy and energy-dispersive X-ray spectroscopy) techniques were used to further specify the adsorption mechanisms. The influence of chemical adsorption, surface-induced precipitation of brandholzite Mg[Sb(OH)6]2·6H2O, formation of brandholzite-like phases and/or anion exchange was observed. Moreover, Sb(V) was nonhomogeneously distributed on the Mg-Fe LDH surface at all pH values. The surface complexation modeling supported by solid-state analyses provided a strong tool to investigate the binding arrangements of Sb(V) on the Mg-Fe LDH surface. Such a complex mechanistic/modeling approach has not previously been presented and enables prediction of the Sb(V) adsorption behavior onto Mg-Fe LDHs under different conditions, evaluating their possible use in actual applications.

Biochar-based materials are currently intensively studied and used as highly efficient sorbents. While “pure” biochars can exhibit important adsorption properties for some metal(loid)s, the efficiency for others can be limited. For this reason, several modifications have been developed in order to increase their efficiency, selectivity for different elements or even their stability. These composites include, for example, magnetic modification with Fe oxides, nano zero-valent Fe, layered double hydroxides, and Mn oxides. This chapter aims to review the potential of these composite materials and the responsible mechanisms for metal(loid) sorption.

This study investigates redox transitions associated with the adsorption of Cr(VI) on commonly occurring soil components (silicates, oxides and humic acids) and their synthetic mixtures by coupling the mechanistic surface complexation modeling with spectroscopic and isotopic analyses. The mixtures of soil components were prepared to reflect the composition of the real anthroposol sample, determined by X-ray Powder Diffraction (XRD), total organic carbon (TOC) measurement and extraction methods. The effect of different initial Cr(VI) concentrations (2×10−2, 5×10−4, 10−4, 10−5, and 10−6M), background electrolyte (10−3, 10−2, and 10−1M KNO3), pH values (3–9), and sorbate/sorbent ratios (2g/L - 20g/L) were investigated. Maghemite and ferrihydrite were confirmed to be the main phases controlling Cr(VI) adsorption with increasing Cr(VI) concentration. Humic acids were primarily responsible for Cr(VI) reduction, especially at low pH values. The reduction of Cr(VI) was also proved in case of illite and kaolinite by XAS and isotopic analyses. Illite revealed higher reduction capacity in comparison with kaolinite based on XAS measurements. Chromium isotopic fractionation, resulting from Cr(VI) reduction, was the highest in the case of humic acids, followed by kaolinite and illite. However, a dissolution of intrinsic Cr originally present within kaolinite and illite might affect the final Cr isotopic composition of the supernatants due to its different Cr isotopic signature. In general, the combination of three different approaches was confirmed to offer more comprehensive information about Cr(VI) adsorption and/or reduction in soils. Detailed studies using soil mixtures can help to predict how the soil components affect Cr(VI) behavior in natural soils and possibly could improve the environmental remediation processes. Keywords: Chromate reduction, Soil component mixtures, Adsorption modeling, Cr isotopes, X-ray absorption spectroscopy

Although the potential of natural zeolites for water and soil remediation has been widely studied, the use of synthetic zeolites, especially from by-product/waste materials, is still rather scarce. Therefore, we present a complex study investigating the adsorption mechanisms of Zn(II) on natural (ZC), synthetic (13X), and perlite by-product (ZP) zeolites under different conditions including laboratory solutions, extracted soil solutions and real metal-rich soils. Adsorption mechanisms in laboratory solutions were studied by a combination of adsorption modeling, including a non-electrostatic modeling with two surface sites corresponding to cation exchange and surface complexation (NEM-CE/SC); desorption experiments and comprehensive solid-state analyses. Based on the obtained results, the adsorbed amount and strength of binding decreased in the order of synthetic > perlite by-product > natural zeolite. In the case of natural zeolite, the prevailing effect of CE is expected. Contrarily, the influence of both CE and SC is expected for synthetic zeolites. The experiments in soil solutions showed sufficient sorption efficiency and chemical stability of all materials with a slight pH increase after the application of both synthetic zeolites. Soil incubation experiments showed reversible binding of Zn on natural zeolite and a significant influence of irreversible binding on both synthetic zeolites. Based on the obtained results, zeolites prepared from a perlite by-product material are promising soil amendments. However, their application to real soils needs to be thoroughly evaluated according to specific properties of the given soil due to a potential pH increase and elevated salinity levels caused by leaching of exchangeable cations.

A surface-modified amorphous manganese oxide (SM-AMO) was prepared to increase the stability of a previously studied promising stabilizing agent and to compare its immobilizing efficiency with respect to contaminating metals with the original material. To synthesize the SM-AMO, the AMO surface was synthetically covered with a coating of MnCO 3 because newly formed rhodochrosite precipitates were previously found to increase the stability of AMO particles in soils. A preliminary experiment evaluating the long-term stability of both materials in pure water suggested higher stability for the SM-AMO particles, showing a smaller release of Mn compared to the original AMO. An adsorption kinetics study focused on As, Cd, Pb and Zn showed lower adsorption rates and adsorption capacity for Zn, probably as a result of partial surface passivation. In comparison to these results for simple controlled systems, different effects were recorded when the two materials were applied to contaminated soils. When incubated in soil, a constantly lower mass loss was recorded in the case of SM-AMO. There were no significant differences in the release of Mn and DOC into the soil solution or in the stabilizing efficiency with regard to contaminating metal(loid)s between the original and surface-modified materials. Concerning the potential solid phase transformations in soil conditions, we observed a gradual equilibration between the surface composition of both materials. While the newly formed rhodochrosite precipitated on the AMO surface, the MnCO 3 coatings on SM-AMO gradually dissolved. Both amendments also effectively supported microbial activity, especially in the more contaminated soil sample. Thus, despite the smaller mass loss, the effectiveness of both materials is comparable in the long term.

The application of nanomaterials is progressively moving away from the experimental into practical areas. Nanoparticles have the potential to aggregate, and their interaction with plant root surfaces has been hypothesized to be a key factor in their phytotoxic effects. In an attempt to better explain their effects on plant physiology, this work investigated why nano zerovalent Fe (nZVI) and nano-maghemite (nFe2O3) affect differently the nutritional status of plants, through distinct effects on the root functionality. A hydroponic experiment, together with an incubation experiment, helped to relate the reduction of the root water uptake with the potential blockage of root nutrient uptake by each nanomaterial. The treatment with 100 mg L−1 nFe2O3 inhibited a 40% the root hydraulic conductivity (Lo) of tomato plants (Solanum lycopersicum L.), which could explain the reduction in the Mo and Zn concentrations in their shoots. On the other hand, compared to nFe2O3, nZVI seems to be less harmful since no effects on Lo were detected for the exposed roots, or regarding a shoot nutrient composition. So, even when iron nanoparticles are considered non-toxic to plants, their adherence to the root surface could explain some adverse effects in plants.

This paper discusses Cd(II) and Pb(II) sorption efficiency of biochars modified by impregnation with magnetic particles. All selected biochar characteristics were significantly affected after the modification. More specifically, the cation exchange capacity increased after the modification, except for grape stalk biochar. However, the changes in the pH value, PZC, and BET surface after modification process were less pronounced. The metal loading rate was also significantly improved, especially for Cd(II) sorption on/in nut shield and plum stone biochars (10- and 16-times increase, respectively). The results indicated that cation exchange (as a metal sorption mechanism) was strengthened after Fe oxide impregnation, which limited the desorbed amount of tested metals. In contrast, the magnetization of grape stalk biochar reduced Pb(II) sorption in comparison with that of pristine biochar. Magnetic modification is, therefore, more efficient for biochars with well-developed structure and for more mobile metals, such as Cd(II).