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Baccharis macraei Hook. & Arn (Asteraceae), commonly known as Vautro, is found in the coastal areas of central-southern Chile, including the industrial zone of Quintero-Puchuncaví, known for the contamination of its soils with heavy metals, which together with other factors generate abiotic stress in plant species, against which they present defensive mechanisms. For this reason, the objective was to evaluate the effect of abiotic stress generated by the proximity of B. macraei to the industrial complex by assessing the physiological and metabolic states reported by the extracts and compounds isolated from the species, as well as the photosynthetic capacity, metal content and production, and antioxidant activity and cytotoxicity against tumorigenic cell lines of the phytoconstituents. To this end, B. macraei was collected at two different distances from the industrial complex, observing that the closer the species is, the greater the concentration of copper in the soil, generating a decrease in the rate of electron transport in situ, but an increase in antioxidant activity with low cytotoxicity. This activity could be due to the presence of flavonoids such as Hispidulin, Cirsimaritina, and Isokaempferida, as well as monoterpenes, oxygenated and non-oxygenated sesquiterpenes identified in this study. [ABSTRACT FROM AUTHOR]

Batch and transport experiments were used to investigate the remediation of loamy sand soil contaminated with Cr(VI) using zero-valent iron nanoparticles (nZVI) stabilized by carboxymethylcellulose (CMC-nZVI). The effect of pH, ionic strength (IS), and flow rate on the removal efficiency of Cr(VI) were investigated under equilibrium (uniform transport) and non-equilibrium (two-site sorption) transport using the Hydrus-1D model. The overall removal efficiency ranged from 70 to over 90% based on the chemical characteristics of the CMC-nZVI suspension and the transport conditions. The concentration and pH of the CMC-nZVI suspension had the most significant effect on the removal efficiency and transport of Cr(VI) in the soil. The average removal efficiency of Cr(VI) was increased from 24.1 to 75.5% when the concentration of CMC-nZVI nanoparticles was increased from 10 to 250 mg L−1, mainly because of the increased total surface area at a larger particle concentration. Batch experiments showed that the removal efficiency of Cr(VI) was much larger under acidic conditions. The average removal efficiency of Cr(VI) reached 90.1 and 60.5% at pH 5 and 7, respectively. The two-site sorption model described (r2 = 0.96–0.98) the transport of Cr(VI) in soil quite well as compared to the uniform transport model (r2 = 0.81–0.98). The average retardation of Cr(VI) was 3.51 and 1.61 at pH 5 and 7, respectively, indicating earlier arrival for the breakthrough curves and a shorter time to reach maximum relative concentration at lower pH. The methodology presented in this study, combining column experiment and modeling transport using the Hydrus-1D model, successfully assessed the removal of Cr(VI) from polluted soils, offering innovative, cost-effective, and environmentally friendly remediation methodologies. [ABSTRACT FROM AUTHOR]

Heavy metal pollution in farmland soil threatens soil environmental quality. It is an important task to quickly grasp the status of heavy metal pollution in farmland soil in a region. Hyperspectral remote sensing technology has been widely used in soil heavy metal concentration monitoring. How to improve the accuracy and reliability of its estimation model is a hot topic. This study analyzed 440 soil samples from Sihe Town and the surrounding agricultural areas in Yushu City, Jilin Province. Considering the differences between different types of soils, a local regression model of heavy metal concentrations (As and Cu) was established based on projection pursuit (PP) and light gradient boosting machine (LightGBM) algorithms. Based on the estimations, a spatial distribution map of soil heavy metals in the region was drawn. The findings of this study showed that considering the differences between different soils to construct a local regression estimation model of soil heavy metal concentration improved the estimation accuracy. Specifically, the relative percent difference (RPD) of As and Cu element estimations in black soil increased the most, by 0.30 and 0.26, respectively. The regional spatial distribution map of heavy metal concentration derived from local regression showed high spatial variability. The number of characteristic bands screened by the PP method accounted for 10–13% of the total spectral bands, effectively reducing the model complexity. Compared with the traditional machine model, the LightGBM model showed better estimation ability, and the highest determination coefficients (R2) of different soil validation sets reached 0.73 (As) and 0.75 (Cu), respectively. In this study, the constructed PP–LightGBM estimation model takes into account the differences in soil types, which effectively improves the accuracy and reliability of hyperspectral image estimation of soil heavy metal concentration and provides a reference for drawing large-scale spatial distributions of heavy metals from hyperspectral images and mastering soil environmental quality. [ABSTRACT FROM AUTHOR]

Sewage sludge should primarily find use in agriculture, reducing the quantity directed towards alternative disposal methods like incineration or deposition in municipal landfills. This study evaluated the agronomic value and the risk of soil and plant tissue contamination with heavy metals in sewage sludge obtained from two wastewater treatment plants (WWTP). The experiment was arranged as a 2 × 5 factorial (two sewage sludges, five sanitation treatments), involving lettuce cultivation in pots over two growing cycles. The two sewage sludges were sourced from the WWTPs of Gelfa and Viana do Castelo and underwent five sanitation and stabilization treatments (40% and 20% calcium oxide, 40% and 20% calcium hydroxide, and untreated sewage sludge). The Gelfa sewage sludge, characterized by a higher initial nitrogen (N) concentration, resulted in greater dry-matter yield (DMY) (12.4 and 8.6 g plant−1 for the first and second growing cycles, respectively) compared to that from Viana do Castelo (11.0 and 8.1 g plant−1), with N release likely being a major factor influencing crop productivity. The high N concentration and the low carbon (C)/N ratio of sewage sludge led to rapid mineralization of the organic substrate, which additionally led to a higher release of other important nutrients, such as phosphorus (P) and boron (B), making them available for plant uptake. Alkalizing treatments further stimulated sewage sludge mineralization, increasing soil pH and exchangeable calcium (Ca), thereby enhancing Ca availability for plants, and indicating a preference for use in acidic soils. Cationic micronutrients were minimally affected by the sewage sludge and their treatments. The concentrations of heavy metals in the sewage sludge, soils, and lettuce tissues were all below internationally established threshold limits. This study highlighted the high fertilizing value of these sewage sludges, supplying N, P, and B to plants, while demonstrating a low risk of environmental contamination with heavy metals. Nevertheless, the safe use of sewage sludge by farmers depends on monitoring other risks, such as toxic organic compounds, which were not evaluated in this study. [ABSTRACT FROM AUTHOR]

Nickel (Ni) is extremely toxic to plants at high concentrations. Phytoliths have the potential to sequester the heavy metals absorbed by plants and act as a detoxification mechanism for the plant. The authors of the present study aimed to evaluate the effects of Ni on the growth and phytolith yield of grasses in two artificially contaminated soils. Two experiments separated by soil types (Typic Quartzipsamment and Rhodic Hapludox) were conducted in a completely randomized design in a 2 × 4 factorial scheme with three replications. The factors were two species of grass (Urochloa decumbens and Megathyrsus maximus) and three concentrations of Ni (20, 40, and 120 mg kg−1) and control treatment. The grasses were influenced by the increase in Ni rates in the soils. Ni exerted a micronutrient function with the addition of 30 mg kg−1 of Ni in soils, but this concentration caused toxicity in grasses. Such a level is lower than the limits imposed by the Brazilian environmental legislation. Higher Ni availability in Typic Quartzipsamment promoted Ni toxicity, with reduced growth and increased phytolith yield in the shoot, increased Ni in the shoot, and Ni occlusion in phytoliths by grasses, in comparison with Rhodic Hapludox. The yield and Ni capture in phytoliths by grasses in Ni-contaminated soils are related to the genetic and physiological differences between grasses and Ni availability in soils. Ni capture by phytoliths indicates that it may be one of the detoxification mechanisms of Urochloa decumbens to Ni contamination, providing additional tolerance. Megathyrsus maximus may be a future grass for the phytoremediation technique in Ni-contaminated soils. [ABSTRACT FROM AUTHOR]

Contamination of soil with heavy metals has become a matter of global importance due to its impact on agriculture, environmental integrity, and therefore human health and safety. Several microbial strains isolated from soil contaminated by long-term chemical and petrochemical activities were found to manifest various levels of tolerance to Cr, Pb, and Zn, out of which Bacillus marisflavi and Trichoderma longibrachiatum exhibited above-moderate tolerance. The concentrations of target heavy metals before and after bioremediation were determined using electrochemical screen-printed electrodes (SPE) modified with different nanomaterials. The morpho-structural SEM/EDX analyses confirmed the presence of metal ions on the surface of the cell, with metal uptake being mediated by biosorption with hydroxyl, carboxyl, and amino groups as per FTIR observations. T. longibrachiatum was observed to pose a higher bioremediation potential compared to B. marisflavi, removing 87% of Cr and 67% of Zn, respectively. Conversely, B. marisflavi removed 86% of Pb from the solution, compared to 48% by T. longibrachiatum. Therefore, the fungal strain T. longibrachiatum could represent a viable option for Cr and Zn bioremediation strategies, whereas the bacterial strain B. marisflavi may be used in Pb bioremediation applications. [ABSTRACT FROM AUTHOR]

Farmland soil quality is a crucial determinant for agricultural productivity, food safety, and human well-being. Among the various contaminants, heavy metals have emerged as pervasive factors significantly impacting farmland quality, attracting widespread societal concern. In this study, we systematically applied multivariate statistical analysis, geostatistical methods, and the positive matrix factorization (PMF) source apportionment technique to elucidate the sources and contributions of eight heavy metals (Cd, Hg, As, Pb, Cr, Cu, Zn, Ni) in farmland soils within an industrialized town. Our findings reveal that Cd, Hg, Pb, and Zn exhibit pollution or enrichment in farmland soils compared to natural background levels, with Hg and Cd surpassing 164.3% and 50.2%, respectively. Notably, Zn demonstrates discernible point-source pollution. Source apportionment results highlight industrial point sources, coal combustion, and agriculture as the primary anthropogenic contributors to heavy metal contamination, with zinc-plating enterprises being the predominant industrial point sources. Addressing the specific issue of point-source pollution from Zn in industrial activities, further analysis establishes a correlation between soil Zn content and the distance from zinc-plating enterprises. Utilizing an atmospheric transport model, we observe that the impact of industrial activities on soil Zn is limited when the distance exceeds 1.5 km, emphasizing the importance of monitoring Zn pollution within areas less than 1.5 km. This study pioneers a progressive source apportionment approach, considering the origins of different heavy metals, pollution levels, distance factors, and the cost-effectiveness of environmental measures. The insights gained provide scientifically sound strategies for future decision making in environmental protection. [ABSTRACT FROM AUTHOR]

Simple Summary: The environmental issue posed by the distribution of plastic is largely due to their fragmentation into micro- and nanoplastics (MNPs), which are spread across aquatic, atmospheric, and terrestrial ecosystems. The discovery that these particles can easily accumulate in aquatic organisms and edible plants has rapidly drawn global attention to their potential impact on human health. Therefore, based on the One Health approach, this paper will first provide an overview of soil contamination as well as human exposure routes and toxicity pathways of MNPs. It then describes the significant role of livestock animals as a critical link between soil and human exposure, focusing on the lack of the available literature and on the role of livestock animals as reservoirs and carriers of MNP contamination along the food chain. The lack of a standardized method to detect, quantify, and characterize plastic particles in different matrices prevents the determination of their realistic load. For this reason, the development of a database where researchers can document data, both on MNP characteristics and assessment procedures, is also suggested with the perspective of training, in the future, artificial intelligence (AI) tools capable of predicting the most abundant/dangerous polymer(s) and help in guiding decisions to reduce risks to global health. Plastic pollution is a global diffuse threat, especially considering its fragmentation into microplastics (MPs) and nanoplastics (NPs). Since the contamination of the aquatic environment is already well studied, most studies have now focused on the soil. Moreover, the number of studies on the exposure routes and toxic effects of MNPs in humans is continuously increasing. Although MNPs can cause inflammation, cytotoxicity, genotoxicity and immune toxicity in livestock animals, which can accumulate ingested/inhaled plastic particles and transfer them to humans through the food chain, research on this topic is still lacking. In considering farm animals as the missing link between soil/plant contamination and human health effects, this paper aims to describe their importance as carriers and vectors of MNP contamination. As research on this topic is in its early stages, there is no standard method to quantify the amount and the characteristics of MNPs in different matrices. Therefore, the creation of a common database where researchers can report data on MNP characteristics and quantification methods could be helpful for both method standardization and the future training of an AI tool for predicting the most abundant/dangerous polymer(s), thus supporting policy decisions to reduce plastic pollution and perfectly fitting with One Health principles. [ABSTRACT FROM AUTHOR]

Long-term coal mining activities have led to severe heavy metal pollution in the soil environment of coal mining areas, posing significant threats to both ecological environments and human health. In this study, surface soil samples were collected from the overlying soil of coal gangue and the surrounding areas of the Panyi coal mine in Huainan. The concentrations of Cd, Zn, Cu, Ni, and Pb elements were determined. A self-organizing map (SOM) and an absolute principal component score multiple linear regression (APCS-MLR) receptor model were employed for the quantitative analysis of the soil's heavy metal pollution sources and contributions. Additionally, this study focused on the analysis of the pathways of the relatively serious pollution of Cd. The results revealed that the average concentrations of heavy metals (Cd, Pb, Zn, Cu, Cr, and Ni) in the study area were 4.55, 0.59, 1.54, 0.69, 0.59, and 0.71 times the local soil background values, respectively. The concentrations of Cd and Zn exceeded the risk screening values at some sampling points, with exceedance rates of 44% and 8%, respectively, indicating a relatively serious Cd contamination. The sources of heavy metals in the soil in the study area were classified into four categories: mining activities, agricultural activities, weathering of natural matrices, and other unknown sources, with average contributions of 55.48 percent, 24.44 percent, 8.91 percent and 11.86 percent, respectively. Based on the spatial distribution of Cd, it was inferred that atmospheric deposition is one of the important pollution pathways of Cd in the study area. Cd profile distribution patterns and a surface water pollution survey showed that the farmland areas were affected by the irrigation water pathway to some extent. The vertical distribution of heavy metal content in the forest area showed a strong disorder, which was related to the absorption function of plant roots. The results of this study can help to improve the environmental management of heavy metal pollution so as to protect the ecological environment and human health. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the efficiency of a geopolymer binder of the type of Na-poly(ferro–silico–aluminate) as a matrix for the stabilization of heavy metals along with their effect on the development of structural performances. The artificial contamination of soil with ions was carried out and used to prepare an alkali-activated iron-rich lateritic soil binder. Further, various microstructural analyses were carried out to explain the stabilization mechanism. The stabilization efficiency was assessed by leaching tests in de-ionized water and hydrochloric acid (0.1 M, HCl). Then, the physical properties were determined to evaluate the impact of heavy metals on the structural performance of the binder. Results demonstrated that the prepared geopolymer binder has the lowest stabilization capacity in an acidic medium (low pH) than in water with high pH. However, the stabilization of Cu ions was effective at 99%, while the Cd ion is barely retained in the matrix. Firstly, the mechanism consists of chemical bonds through ion exchange with sodium of the Na-poly(ferro–silico–aluminate) network. Secondly, through physical interaction with the pore network of the matrix, the heavy metals induced structural deterioration in the geopolymer matrix with a decrease in the compressive strength and bulk density and an increase of both apparent porosity and water absorption. [ABSTRACT FROM AUTHOR]

Heavy metal contamination, associated with the increase in industrial production and the development of the population in general, poses a significant risk in terms of the contamination of soil, water, and, consequently, industrial plants and human health. The presence of ecotoxic heavy metals (HMs) thus significantly limits the sustainable development of society and contributes to the deterioration of the quality of the environment as a whole. For this reason, the stabilization and immobilization of heavy metals is a very topical issue. This paper deals with the possibility of the simultaneous immobilization of heavy metals (Ba2+, Pb2+, and Zn2+) in mortar based on magnesium potassium phosphate cement (MKPC). The structural, mechanical, and hygric parameters of mortars artificially contaminated with heavy metals in the form of salt solutions were investigated together with the formed hydration products. In the leachates of the prepared samples, the content of HMs was measured and the immobilization ratio of each HM was determined. The immobilization rate of all the investigated HMs was >98.7%, which gave information about the effectiveness of the MKPC-based matrix for HM stabilization. Furthermore, the content of HMs in the leachates was below the prescribed limits for non-hazardous waste that can be safely treated without any environmental risks. Although the presence of heavy metals led to a reduction in the strength of the prepared mortar (46.5% and 57.3% in compressive and flexural strength, respectively), its mechanical resistance remained high enough for many construction applications. Moreover, the low values of the parameters characterizing the water transport (water absorption coefficient Aw = 4.26 × 10−3 kg·m−2·s−1/2 and sorptivity S = 4.0 × 10−6 m·s−1/2) clearly demonstrate the limited possibility of the leaching of heavy metals from the MKPC matrix structure. [ABSTRACT FROM AUTHOR]

Soil contamination through heavy metals (HMs) is a serious environmental problem that needs to be addressed. One of the methods of remediating soils contaminated with HMs and reducing the environmental risks associated with them is to immobilize these HMs in the soil using specific amendment(s). The use of biochar as an organic amendment can be an environmentally friendly and practically feasible option, as (i) different types of biomass can be used for biochar production, which contributes to environmental sustainability, and (ii) the functionality of biochar can be improved, enabling efficient immobilization of HMs. Effective use of biochar to immobilize HMs in soil often requires modification of pristine biochar. There are various physical, chemical, and biological methods for modifying biochar that can be used at different stages of pyrolysis, i.e., before pyrolysis, during pyrolysis, and after pyrolysis. Such methods are still being intensively developed by testing different modification approaches in single or hybrid systems and investigating their effects on the immobilization of HMs in the soil and on the properties of the remediated soil. In general, there is more information on biochar modification and its performance in HM immobilization with physical and chemical methods than with microbial methods. This review provides an overview of the main biochar modification strategies related to the pyrolysis process. In addition, recent advances in biochar modification using physical and chemical methods, biochar-based composites, and biochar modified with HM-tolerant microorganisms are presented, including the effects of these methods on biochar properties and the immobilization of HMs in soil. Since modified biochar can have some negative effects, these issues are also addressed. Finally, future directions for modified biochar research are suggested in terms of scope, scale, timeframe, and risk assessment. This review aims to popularize the in situ immobilization of HMs with modified biochar. [ABSTRACT FROM AUTHOR]

The ingestion of vegetables grown in soils or in cultivation substrate contaminated with heavy metals (HMs) and irrigated with wastewater is a potential problem for human health and food quality. The increasing disappearance of fertile soils has led to an increase in the practice of soil-less cultivation and the use of growing substrates, but the choice of the right substrate and its sustainable management is essential to ensure the production of quality and safe vegetables for all while minimizing the impact on the environment and human health. The present study measures the combined effects of different HMs (V, Ni, Cd, Pb, Cu, Cr) on microbial biomass, respiration, and enzyme activities (EAs) in an artificially contaminated commercial growing substrate. The concentrations of HMs were estimated by Atomic Absorption Spectroscopy; enzyme activities via spectrophotometric assays; respiration via CO2 evolution; and microbial biomass C via the fumigation extraction method. The results showed a reduction in both respiration and all enzyme activities. The reduction in EAs highlighted a notable influence on microorganism-mediated C, N, S, and P cycles, strongly reducing substrate health. Microbial biomass did not show significant differences, but the increase in the metabolic quotient highlighted how the toxicity of HMs reduces the energy use efficiency of microbial metabolic processes. [ABSTRACT FROM AUTHOR]

Population expansion within agricultural lands applies pressure on natural resources, particularly water resources, and leads to contamination through different types of pollutants, such as heavy metals, that consequently alter the ecosystem and impact human health. In the present work, several heavy metals in sediment along the Kitchener drain were assessed using different soil quality and health indices; the Kitchener drain is one of the major drains in the Nile Delta. Sediments were collected from six stations along the drain from upstream to downstream. Soil physical and chemical properties were analyzed as well as four metal pollution indices and five ecological risk indices. Additionally, carcinogenic and noncarcinogenic risks for adults and children were evaluated. The data showed that the Kitchener drain is mainly contaminated with Cd, Pb, and Zn, where the concentrations decreased from upstream to downstream. The eco-toxicological indexes showed that Pb, Zn, and Cr were the most hazardous metals along the drain, mainly at upstream stations. The human health risk indices data revealed that the noncarcinogenic risk of the studied metals can be ordered as follows: Co > Cr > Pb > Mn > Ni > Cd > Cu > Zn for adults, while for children it was Cr > Mn > Co > Pb > Ni > Cd > Cu > Zn. The carcinogenic risk data showed that heavy metals ranged from low to medium in all sites, except for Pb and Zn, which have high carcinogenic risks. The present study showed more contamination upstream compared to downstream which can be attributed to urbanization and human activity, as shown from the land use/landcover map. This highlighted that the major drains inside the Nile Delta suffer from different anthropogenic activities that should be taken into consideration by researchers, scientists, and policymakers. Also, the source of heavy metal pollution, particularly upstream, should be controlled or treated before discharge into the drain. On the other side, downstream (toward the Mediterranean Sea), the heavy metals could affect the trophic levels of the marine ecosystem on the Mediterranean Sea which should be taken into consideration. [ABSTRACT FROM AUTHOR]

Phytoextraction is a promising technology for remediating heavy metal-contaminated soil. Continuously screening potential plants is important for enhancing the efficiency of remediation. In this study, fourteen local native plant species and four cultivated plant species, along with their paired soils, were collected from around a copper smelter. The characteristics of soil pollution were evaluated using contaminant factors (CF) and a geoaccumulation index (Igeo). The phytoextraction potential of plants was investigated using the translocation factor (TF) and bioconcentration factor (BCF). The soils around the smelter were very acidic, with a mean pH of 5.01. The CF for copper and cadmium were 8.67–32.3 and 5.45–44.2, and the Igeo values for copper and cadmium were 2.43–4.43 and −0.12–2.29, respectively, indicating that the level of soil contamination was moderate to severe. The copper concentrations in the root (357 mg/kg), shoot (219 mg/kg), and leaf (269 mg/kg) of Elsholtzia splendens Nakai were higher than that in the other species. The cadmium in the shoot (32.2 mg/kg) and leaf (18.5 mg/kg) of Sedum plumbizincicola was the highest, and Phytolacca acinosa Roxb. had the highest cadmium level (20 mg/kg) in the root. Soil total and CaCl2-extractable copper and cadmium were positively correlated with copper and cadmium in the plant roots, respectively. The results of TF and BCF for copper and cadmium suggested that the accumulation and translocation capacities for cadmium were higher than those of copper in the eighteen plant species. Although not all plants met the criteria of being hyperaccumulators, Sedum plumbizincicola, Mosla chinensis Maxim, and Elsholtzia splendens Nakai showed the most potential as candidates for the phytoextraction of copper and cadmium contaminated soils, as indicated by their TF and BCF values. [ABSTRACT FROM AUTHOR]

The contamination of agricultural soil with cadmium (Cd), a heavy metal, poses a significant environmental challenge, affecting crop growth, development, and human health. Previous studies have established the pivotal role of the ZmHMA3 gene, a P-type ATPase heavy metal transporter, in determining variable Cd accumulation in maize grains among 513 inbred lines. To decipher the molecular mechanism underlying mutation-induced phenotypic differences mediated by ZmHMA3, we conducted a quantitative tandem mass tag (TMT)-based proteomic analysis of immature maize kernels. This analysis aimed to identify differentially expressed proteins (DEPs) in wild-type B73 and ZmHMA3 null mutant under Cd stress. The findings demonstrated that ZmHMA3 accumulated higher levels of Cd compared to B73 when exposed to varying Cd concentrations in the soil. In comparison to soil with a low Cd concentration, B73 and ZmHMA3 exhibited 75 and 142 DEPs, respectively, with 24 common DEPs shared between them. ZmHMA3 showed a higher induction of upregulated genes related to Cd stress than B73. Amino sugar and nucleotide sugar metabolism was specifically enriched in B73, while phenylpropanoid biosynthesis, nitrogen metabolism, and glyoxylate and dicarboxylate metabolism appeared to play a more significant role in ZmHMA3. This study provides proteomics insights into unraveling the molecular mechanism underlying the differences in Cd accumulation in maize kernels. [ABSTRACT FROM AUTHOR]

In soil with extremely high contents of Cd (101.87), Pb (26,526.44), and Zn (17,652.63 mg kg−1), we aimed to test the phytostabilization capacity of purslane (Portulaca oleracea) with the use of various soil improvers, both organic (biochar, compost, insect frass) and inorganic (lime and zeolite). Thus, in a 60-day pot experiment, we amended this heavily contaminated soil with the five materials at two rates, 2% and 4%, resulting in 11 treatments (control plus five materials × two rates) replicated 10 times. We found that soil extractions of Cd with DTPA (diethylenetriaminepentaacetic acid) were not affected by any of the amendments, as there was no recorded significant reduction in soil Cd. In the case of Pb, there were even significant increases in its extractability with added biochar, and so was the case for compost at 4%. The reason may be the formation of organometallic complexes with organic substances of low molecular weight eluted by the organic amendments. Similarly, Zn extractability increased significantly compared to the control in the compost and frass treatments. As for purslane shoots, Cd decreased from 61 μg kg−1 fresh weight (FW) at control to 39 at biochar 4%, but the reduction was non-significant. As for Pb, it decreased with biochar but not significantly, while it exhibited a significant decrease in all other treatments. However, in all cases the content of Pb in purslane was well above the European regulation limit of 0.100 mg kg−1 FW (fresh weight) for vegetables and fresh herbs, while Cd fell below the regulation limit of 50 μg kg−1 FW at biochar 4%, compost 4%, and frass 2% and 4% (with control being 62.5 μg kg−1 FW). We conclude that in heavily contaminated soils, although biochar, along with compost and frass, was not entirely unsuccessful, the tested amendments did not reduce satisfactorily toxic elements to sufficiently low levels both in soil and in the test plant (here, purslane) in order to achieve phytostabilization. However, further research is necessary to identify exact mechanisms and to elucidate the role of different biochars. [ABSTRACT FROM AUTHOR]

Human activities have significantly impacted the environment, resulting in a need to restore degraded areas through various remediation techniques. This study aimed to evaluate the effectiveness of saponite in the aided phytostabilisation technique for heavy-metal-contaminated soil. The research was conducted on soil from a post-industrial site characterised by high metal content (Cu, Ni, Cd, Pb, Zn, and Cr) surpassing the established regulatory limits. Saponite was added to the contaminated soil at a ratio of 3% (w/w). The experiment was performed using Lolium perenne L. and Festuca rubra L. due to their adaptability to harsh soil conditions and rapid growth. The results demonstrated that saponite application significantly increased soil pH, which is beneficial for phytostabilisation of heavy metals. Saponite has been found to selectively enhance Ni accumulation in roots while not affecting Pb accumulation in above-ground parts, implying that saponite can effectively regulate heavy metal accumulation in plant biomass. Furthermore, saponite has been observed to significantly decrease soil Cd, Zn, and Cr levels with no impact on Cu, Ni, and Pb levels. Overall, saponite shows promise as an effective and scalable solution for large-scale phytostabilisation projects, contributing to the restoration of degraded soils and the protection of environmental and human health. [ABSTRACT FROM AUTHOR]

In order to study the characteristics and sources of heavy metal pollution within different grassland soil categories in Altay, 147 soil samples were collected in Fuyun County according to grassland type, and the contents of seven heavy metals (Cu, Pb, Cr, Zn, As, Ni, and Cd) were determined. The heavy metal pollution in the soil was evaluated using the Nemerow pollution and geological accumulation index methods. The absolute principal component score–multiple linear regression model (APCS-MLR) model was used to analyze the sources of heavy metals and the contribution rate of the pollution sources. The results showed that (1) the heavy metal content of 0~10 cm soil in the mining area was generally higher than the remaining two layers. Natural grassland was the most seriously contaminated, and the order of its contamination was Zn > Pb > Ni > Cd > Cu > Cr > As. (2) The evaluation results of the comprehensive pollution index showed that Ni and Cd were the main pollutants in five grassland types, and the evaluation results of the geological accumulation index method showed that natural grasslands were more polluted. (3) Three pollution sources were obtained according to the analysis using the APCS-MLR model, including natural and mining activity sources (32.6%), industrial coal combustion and sewage sources (24.7%), and an unknown source (42.7%). The results of the study can provide a basis for pollution control and ecological protection in the grasslands of Altay. [ABSTRACT FROM AUTHOR]

A rising quantity of coal gasification slag (CGS) is produced annually. Land reclamation is a valuable method for efficiently utilizing coal gasification slag on a large scale. The ecological influence of CGS during land reclamation has not been widely investigated. This article covers the entire CGS use cycle for land reclamation, which includes generation, storage, and disposal. The environmental risk of using CGS for land reclamation was assessed by combining four environmental risk assessment methods. The results show no environmental risk for coal gasification coarse slag (CGCS) and coal gasification fine slag (CGFS) at the generation and storage stages. However, a concern remains regarding manganese leaching from CGCS during the storage stage. In the disposal phase, no environmental risk is present when up to 15% of CGCS and CGFS are applied to land reclamation projects. However, the environmental risk of disposing of 100% of CGS in a landfill cannot be disregarded. Conversely, the full-cycle use of CGS for land reclamation carries no environmental risk. [ABSTRACT FROM AUTHOR]

Mining and industrial activity are contributing to the increase in heavy metal (HM) pollution in soils. Phytoremediation coupled to selected rhizosphere microbiota is an environmentally friendly technology designed to promote HM bioremediation in soils. In this study, sunflower (Helianthus annuus L.) was used together with Rhizophagus irregularis, an arbuscular mycorrhizal fungi (AMF), and Cupriavidus sp. strain 1C2, a plant growth promoting rhizobacteria (PGPR), as a phytoremediation strategy to remove Zn and Cd from an industrial soil (599 mg Zn kg−1 and 1.2 mg Cd kg−1). The work aimed to understand if it is possible to gradually remediate the tested soil while simultaneously obtaining significant yields of biomass with further energetic values by comparison to the conventional growth of the plant in agricultural (non-contaminated) soil. The H. annuus biomass harvested in the contaminated industrial soil was 17% lower than that grown in the agricultural soil—corresponding to yields of 19, 620, 199 and 52 g m−2 of roots, stems, flowers and seeds. It was possible to remove ca. 0.04 and 0.91% of the Zn and Cd of the industrial soil, respectively, via the HM accumulation on the biomass produced. The survival of applied microbiota was indicated by a high root colonization rate of AMF (about 50% more than in non-inoculated agricultural soil) and identification of strain 1C2 in the rhizosphere at the end of the phytoremediation assay. In this study, a phytoremediation strategy encompassing the application of an energetic crop inoculated with known beneficial microbiota applied to a real contaminated soil was successfully tested, with the production of plant biomass with the potential for upstream energetic valorisation purposes. [ABSTRACT FROM AUTHOR]

With the rapid development of China's industrialization and urbanization, the problem of heavy metal pollution in soil has become increasingly prominent, seriously threatening the safety of the ecosystem and human health. The development of hyperspectral remote sensing technology provides the possibility to achieve the rapid and non-destructive monitoring of soil heavy metal contents. This study aimed to fully explore the potential of ground and satellite image spectra in estimating soil heavy metal contents. We chose Xushe Town, Yixing City, Jiangsu Province as the research area, collected soil samples from farmland over two different periods, and measured the contents of the heavy metals Cd and As in the laboratory. At the same time, under field conditions, we also measured the spectra of wheat leaves and obtained HuanJing-1A HyperSpectral Imager (HJ-1A HSI) satellite image data. We first performed various spectral transformation pre-processing techniques on the leaf and image spectral data. Then, we used genetic algorithm (GA) optimized partial least squares regression (PLSR) to establish an estimation model of the soil heavy metal Cd and As contents, while evaluating the accuracy of the model. Finally, we obtained the best ground and satellite remote sensing estimation models and drew spatial distribution maps of the soil Cd and As contents in the study area. The results showed the following: (1) spectral pre-processing techniques can highlight some hidden information in the spectra, including mathematical transformations such as differentiation; (2) in ground and satellite spectral modeling, the GA-PLSR model has higher accuracy than PLSR, and using a GA for spectral band selection can improve the model's accuracy and stability; (3) wheat leaf spectra provide a good ability to estimate soil Cd (relative percent difference (RPD) = 2.72) and excellent ability to estimate soil As (RPD = 3.25); HJ-1A HSI image spectra only provide the possibility of distinguishing high and low values of soil Cd and As (RPD = 1.87, RPD = 1.91). Therefore, it is possible to indirectly estimate soil heavy metal Cd and As contents using wheat leaf hyperspectral data, and HJ-1A HSI image spectra can also identify areas of key pollution. [ABSTRACT FROM AUTHOR]

Coal remains a very important source of energy for the global economy. Surface and underground coal mining are the two major methods of coal extraction, and both have benefits and drawbacks. Surface coal mining can have a variety of environmental impacts including ecosystem losses, landscape alteration, soil destruction, and changes to surface and groundwater quality and quantity. In addition, toxic compounds such as heavy metals, radioactive elements, polycyclic aromatic hydrocarbons (PAHs), and other organic contaminants are released in the environment, ultimately affecting the health of ecosystems and the general population. Underground mining has large impacts on underground water supplies and water quality, but generally has less visual surface impacts such as leaving waste and tailings on the surface and subsidence problems. In response to the concern about these environmental issues, many strategies have been developed by scientists and practitioners to minimize land degradation and soil pollution due to mining. Reclamation laws passed in numerous countries during the past 50 years have instituted practices to reduce the impacts of soil pollution including burying toxic materials, saving and replacing topsoil, and vegetating the land surface. While modern mining practices have decreased the environmental impacts, many sites are inadequately reclaimed and present long-lasting soil pollution problems. The current review summarizes progress in comprehending (1) coal mining impacts on soil pollution, (2) the potential risks of soil pollution associated with coal mining, and (3) different types of strategies for remediating these contaminated soils. Research and prospective directions of soil pollution in coal mining regions include refinements in assessing pollutant levels, the use of biochars and other amendments, phytoremediation of contaminated soils, and the release of toxic elements such as mercury and thallium. [ABSTRACT FROM AUTHOR]

Morel is a popular edible mushroom with considerable medicinal and economic value which has garnered global popularity. However, the increasing heavy metal (HM) pollution in the soil presents a significant challenge to morels cultivation. Given the susceptibility of morels to HM accumulation, the quality and output of morels are at risk, posing a serious food safety concern that hinders the development of the morel industry. Nonetheless, research on the mechanism of HM enrichment and mitigation strategies in morel remains scarce. The morel, being cultivated in soil, shows a positive correlation between HM content in its fruiting body and the HM content in the soil. Therefore, soil remediation emerges as the most practical and effective approach to tackle HM pollution. Compared to physical and chemical remediation, bioremediation is a low-cost and eco-friendly approach that poses minimal threats to soil composition and structure. HMs easily enriched during morels cultivation were examined, including Cd, Cu, Hg, and Pb, and we assessed soil passivation technology, microbial remediation, strain screening and cultivation, and agronomic measures as potential approaches for HM pollution prevention. The current review underscores the importance of establishing a comprehensive system for preventing HM pollution in morels. [ABSTRACT FROM AUTHOR]

The issue of agricultural soil pollution is especially important as it directly affects the quality of food and the lives of humans and animals. Soil pollution is linked to human activities and agricultural practices. The main objective of this study is to assess and predict soil contamination by heavy metals utilizing an innovative method based on the adaptive neuro-fuzzy inference system (ANFIS), an effective artificial intelligence technology, and GIS in a semiarid and dry environment. A total of 150 soil samples were randomly collected in the neighboring area of the Bahr El-Baqar drain. Ordinary kriging (OK) was employed to generate spatial pattern maps for the following heavy metals: chromium (Cr), iron (Fe), cadmium (Cd), and nickel (Ni). The adaptive neuro-fuzzy inference system (ANFIS), known as one of the most effective applications of artificial intelligence (AI), was utilized to predict soil contamination by the selected heavy metals (Cr, Fe, Cd, and Ni). In total 150 samples were used, 136 soil samples were used for training and 14 for testing. The ANFIS predicting results were compared with the experimental results; this comparison proved its effectiveness, as a root mean square error (RMSE) was 0.048594 in training, and 0.0687 in testing, which is an acceptable result. The results showed that both the exponential and spherical models were quite suitable for Cr, Fe, and Ni. The correlation values (R2) were close to one in training and test; however, the stable model performed well with Cd. The high concentration of heavy metals was the most prevalent, encompassing approximately 51.6% of the study area. Furthermore, the average concentration of heavy metals in this degree was 82.86 ± 15.59 mg kg−1 for Cr, 20,963.84 ± 4447.83 mg kg−1 for Fe, 1.46 ± 0.42 mg kg−1 for Cd, and 48.71 ± 11.88 mg kg−1 for Ni. The comparison clearly demonstrates that utilizing the ANFIS model is a superior option for predicting the level of soil pollution. Ultimately, these findings can serve as a foundation for decision-makers to develop acceptable measures for mitigating heavy metal contamination. [ABSTRACT FROM AUTHOR]

This document is a preface to a special issue of the Journal of Fungi titled "Heavy Metals in Mushrooms." It highlights the problem of environmental pollution, particularly soil and water pollution, caused by population growth, industrialization, and urbanization. The presence of heavy metals in the environment is a significant concern due to their carcinogenic, mutagenic, neurotoxic, and immunogenic properties. The World Health Organization has identified lead, arsenic, cadmium, and mercury as particularly harmful heavy metals. The document emphasizes the need for scientific studies to monitor and address heavy metal pollution, especially in saprotrophic and ectomycorrhizal fungal species. The special issue includes articles on various topics related to heavy metals in mushrooms, such as molecular tolerance mechanisms, bioremediation, risk assessment, and health risk assessment. The document concludes by calling for a global heavy metal monitoring program and increased monitoring of metals and metalloids in human diets, particularly in edible wild mushrooms. [Extracted from the article]

The heavy metal zinc (Zn) is known to be transmitted in the food chain; however, the effect of Zn stress on beans and herbivorous insects is largely unclear. This study aimed to investigate the resistance of broad bean plants to Zn stress and the consequent changes in their physiological and biochemical metabolism by simulating heavy metal pollution in soil. Simultaneously, the effects of aphid progeny treated with different Zn concentrations on the expression of carbohydrate and related genes were analyzed. The results showed that Zn had no effect on the germination rate of broad beans, but other effects mainly manifested as follows. (1) Chlorophyll content decreased. (2) The total soluble sugar and Zn content in stems and leaves increased with increasing Zn content. (3) The proline content first increased and then decreased with increasing Zn content. (4) The height of the seedlings indicates that low concentrations promote growth and high concentrations inhibit growth. In addition, only the first-generation fecundity decreased significantly when aphids fed on heavy metal broad beans. Continuous high Zn levels increase the trehalose content of aphid F1 and F2, while F3 decreases. These results can not only provide a theoretical basis for exploring the impact of soil heavy metal pollution on ecosystems but also preliminarily evaluate the possibility of broad beans as a means of pollution remediation. [ABSTRACT FROM AUTHOR]

Stomata are one of the important structures for plants to alleviate metal stress and improve plant resistance. Therefore, a study on the effects and mechanisms of heavy metal toxicity to stomata is indispensable in clarifying the adaptation mechanism of plants to heavy metals. With the rapid pace of industrialization and urbanization, heavy metal pollution has been an environmental issue of global concern. Stomata, a special physiological structure of plants, play an important role in maintaining plant physiological and ecological functions. Recent studies have shown that heavy metals can affect the structure and function of stomata, leading to changes in plant physiology and ecology. However, although the scientific community has accumulated some data on the effects of heavy metals on plant stomata, the systematic understanding of the effects of heavy metals on plant stomata remains limited. Therefore, in this review, we present the sources and migration pathways of heavy metals in plant stomata, analyze systematically the physiological and ecological responses of stomata on heavy metal exposure, and summarize the current mechanisms of heavy metal toxicity on stomata. Finally, the future research perspectives of the effects of heavy metals on plant stomata are identified. This paper can serve as a reference for the ecological assessment of heavy metals and the protection of plant resources. [ABSTRACT FROM AUTHOR]

Heavy metals and metalloids (HMs) are environmental pollutants, most notably cadmium, lead, arsenic, mercury, and chromium. When HMs accumulate to toxic levels in agricultural soils, these non-biodegradable elements adversely affect crop health and productivity. The toxicity of HMs on crops depends upon factors including crop type, growth condition, and developmental stage; nature of toxicity of the specific elements involved; soil physical and chemical properties; occurrence and bioavailability of HM ions in the soil solution; and soil rhizosphere chemistry. HMs can disrupt the normal structure and function of cellular components and impede various metabolic and developmental processes. This review evaluates: (1) HM contamination in arable lands through agricultural practices, particularly due to chemical fertilizers, pesticides, livestock manures and compost, sewage-sludge-based biosolids, and irrigation; (2) factors affecting the bioavailability of HM elements in the soil solution, and their absorption, translocation, and bioaccumulation in crop plants; (3) mechanisms by which HM elements directly interfere with the physiological, biochemical, and molecular processes in plants, with particular emphasis on the generation of oxidative stress, the inhibition of photosynthetic phosphorylation, enzyme/protein inactivation, genetic modifications, and hormonal deregulation, and indirectly through the inhibition of soil microbial growth, proliferation, and diversity; and (4) visual symptoms of highly toxic non-essential HM elements in plants, with an emphasis on crop plants. Finally, suggestions and recommendations are made to minimize crop losses from suspected HM contamination in agricultural soils. [ABSTRACT FROM AUTHOR]

Soil contamination by heavy metals such as cadmium (Cd), which is present as a result of agricultural and industrial practices, is a critical problem in many countries around the world. High Cd concentrations in crops during the seedling stage can have a negative impact on performance and growth. The aim of the present study, which involved 59 barley accessions, was to investigate the effects of different Cd concentrations (125, 250, and 500 µM) on the responses of the barley accessions and to identify the biomarker parameters that would aid in the early growth stage selection of the best-performing accession. Barley accessions differed significantly in their morphological and physiochemical characteristics. Compared to the untreated plants, treatments with Cd lowered germination percentages by 1.75–64.28%, 1.67–46.62%, and 1.66–61.90% for concentrations of 125, 250, and 500 μM, respectively. The average of all genotypes showed significant reductions in root length, shoot length, and fresh weight of seedlings, ranging from 37.08% to 77.88%, 18.70% to 44.10%, and 7.69% to 35.87%, respectively. In comparison to untreated plants, the average seed water absorption (WU) increased across all accessions by 42.21% and 20.74%, respectively, under Cd-125 and Cd-250 stress conditions. In contrast, all biochemical measurements increased when Cd concentrations were elevated, with the exception of guaiacol peroxidase (GPA) and catalase (CAT). Across all genotypes, the mean of proline (PC) and sugar (SSC) contents showed the largest increases (123% for PC and 98.63% for SSC) under the Cd-500 stress condition. Three barley accessions: Acsad-14, ABN, and Arabi Aswad, were found to be the most tolerant accessions under all cadmium exposure, whereas the performance of the other tested accessions: Black-Kalar, Bujayl 1-Shaqlawa, and Black-Chiman was inferior. The OMIC analysis identified the biomarker parameters for differentiating the high, moderate, and low tolerant groups as the WU for Cd-125 stress, GPA, WU, CAT, total phenolic content for Cd-250 stress, and all physiochemical traits, with the exception of the CAT feature for Cd-500 treatment. The majority of trait pairings showed significant correlations. Hence, Acsad-14, ABN, and Arabi Aswad barley accessions that had great performance under cadmium conditions can be candidates for selection in a breeding program to improve the growth of plants and output in lands infected by cadmium. It can be concluded that seed water uptake, guaiacol peroxidase, and proline content were biomarker traits that would aid in the early growth stage selection of the best-performing accession under Cd stress conditions. [ABSTRACT FROM AUTHOR]

This study investigated the release of heavy metals from polluted soil under the pore water flow containing nanobubbles (NBs) to simulate natural ebullition. Three types of NBs (CH4, H2, and CO2) were generated in water and characterized, including bubble size, zeta potential, liquid density, and tension. The flow rate used in column tests was optimized to achieve proper soil fluidization and metal desorption or release. The leachate chemistries were monitored to assess the effect of NBs on conductivity, pH, oxidation–reduction potential (ORP), and dissolved oxygen (DO). The results showed that NBs in the pore water flow were significantly more effective in releasing Pb compared to DI water, with CO2 NB water being the most effective and H2 NB water being the least effective. CO2 NB water was also used to rinse column soil contaminated with four different metals (Pb, Cu, Zn, and Cr), which exhibited different leaching kinetics. Moreover, a convective–dispersion–deposition equation (CDDE) model accurately simulated the leaching kinetics and explained the effects of NBs on the key parameters, such as the deposition rate coefficient (Kd), that affect the released metal transport. The findings could provide new insights into soil pollutant release under ebullition and soil remediation using water wash containing NBs. [ABSTRACT FROM AUTHOR]

Mineralogical analysis and laboratory-based leaching tests coupled with speciation modeling were undertaken to quantify the potential for short-term acid generation and the release of trace elements from soils heavily contaminated with mine waste at Rio Tinto. Three different waste materials were considered as case studies: roasted pyrite, copper slags, and leached sulfide ores. The results showed elevated values of net acid generation (up to 663 mmol H+/kg), the major pools being potential sulfidic acidity and acidity retained in jarosite. Remarkable contents of As and toxic heavy metals were found especially in the slag-contaminated soil. Copper, Zn, and Pb were the most abundant metals in the acid leach solutions resulting from mine soil-water interaction, with peak values of 55.6 mg L−1, 2.77 mg L−1, and 2.62 mg L−1, respectively. Despite the high total contents of trace elements occurring in soil, the mobile fraction was limited to maximum release values of 12.60% for Cd and 10.27% for Cu, according to the test leaching. Speciation calculations indicated that free metal ions (M2+) and sulfate species (MSO40) accounted for most of the dissolved load. Acid soil drainage is a secondary source of acid and heavy metals in the mine site and, therefore, an effective land reclamation program should ensure that acidity and metal mobility are reduced to environmentally sustainable levels. [ABSTRACT FROM AUTHOR]

The ecological environment of the remote plateaus has been a challenge plaguing many countries due to global warming, increased human activities, and frequent occurrence of various heavy metal (HM) pollutants. This paper analyzes the primary factors and potential susceptible regions' characteristics related to soil HMs (As, Cd, Pb, Cr, Ni, and Zn) in the southern Tibet Plateau (TP) using Geo-detectors and a set of multi-source data from remote sensing and geographic and geological information. The geoaccumulation index showed that the As pollution was the most serious. The precipitation, pH, geological age (GA), and rock type (RT) were the most critical factors affecting HMs. Additionally, soil HMs were relatively unaffected by land use and clay. Based on the risk detector, the most key impact types (range) of the predominant factors of HM's sources were identified. For example, precipitation (100–200 mm), pH (7–7.5), DEM (>5500 m), RT (ophiolite), and GA (Ordovician) had the highest average concentration of As in each type (ranges) of the predominant factors. This work provides new data on the extent of soil HM contamination in the southern TP and predicts vulnerable areas of HM contamination, providing an important scientific basis for monitoring and managing HM in remote areas at high altitudes. [ABSTRACT FROM AUTHOR]

Soil heavy metal contamination is a severe issue. The detrimental impact of contaminated heavy metals on the ecosystem depends on the chemical form of heavy metals. Biochar produced at 400 °C (CB400) and 600 °C (CB600) from corn cob was applied to remediate Pb and Zn in contaminated soil. After a one month amendment with biochar (CB400 and CB600) and apatite (AP) with the ratio of 3%, 5%, 10%, and 3:3% and 5:5% of the weight of biochar and apatite, the untreated and treated soil were extracted using Tessier's sequence extraction procedure. The five chemical fractions of the Tessier procedure were the exchangeable fraction (F1), carbonate fraction (F2), Fe/Mn oxide fraction (F3), organic matter (F4), and residual fraction (F5). The concentration of heavy metals in the five chemical fractions was analyzed using inductively coupled plasma mass spectroscopy (ICP-MS). The results showed that the total concentration of Pb and Zn in the soil was 3023.70 ± 98.60 mg kg−1 and 2034.33 ± 35.41 mg kg−1, respectively. These figures were 15.12 and 6.78 times higher than the limit standard set by the United States Environmental Protection Agency (U.S. EPA 2010), indicating the high level of contamination of Pb and Zn in the studied soil. The treated soil's pH, OC, and EC increased significantly compared to the untreated soil (p > 0.05). The chemical fraction of Pb and Zn was in the descending sequence of F2 (67%) > F5 (13%) > F1 (10%) > F3 (9%) > F4 (1%) and F2~F3 (28%) > F5 (27%) > F1 (16%) > F4 (0.4%), respectively. The amendment of BC400, BC600, and apatite significantly reduced the exchangeable fraction of Pb and Zn and increased the other stable fractions including F3, F4, and F5, especially at the rate of 10% of biochar and a combination of 5:5% of biochar and apatite. The effects of CB400 and CB600 on the reduction in the exchangeable fraction of Pb and Zn were almost the same (p > 0.05). The results showed that CB400, CB600, and the mixture of these biochars with apatite applied at 5% or 10% (w/w) could immobilize lead and zinc in soil and reduce the threat to the surrounding environment. Therefore, biochar derived from corn cob and apatite could be promising materials for immobilizing heavy metals in multiple-contaminated soil. [ABSTRACT FROM AUTHOR]

Climate change, inadequate possessions, and land degradation all pose obstacles to modern agriculture. In the current scenario, the agriculture industry is mainly dependent on the use of chemical-based pesticides and fertilizers that impact soil health and crop productivity. Moreover, water scarcity leads farmers in drastically affected regions to use heavy metal-enriched water sources mainly originating from industrial sources for field crops irrigation. Soil pollutants can be carried into the human body via dust and water, creating negative health effects varying from simple symptoms, e.g., nausea and diarrhea and reaching death in critical cases. Thus, to clean soil contaminants, and improve soil fertility and agricultural production, alternatives to chemical fertilizers must be developed. Therefore, using beneficial microbes found in plant-associated soil microorganisms offers an effective strategy to alleviate some of these challenges, improving soil fertility, and crop yield, and protecting plants from stress conditions. Through the use of synergistic interactions, the synthetic consortium strategy seeks to improve the stability of microbial communities. In this review, synthetic consortia and their potential use in agriculture were discussed. Further, engineering new effective synthetic consortia was suggested as an effective approach in the concept of environmental bioremediation of soil pollutants and contaminants. [ABSTRACT FROM AUTHOR]

Soil contamination with organic contaminants and various heavy metals has become a global environmental concern. Biochar application for the remediation of polluted soils may render a novel solution to soil contamination issues. However, the complexity of the decontaminating mechanisms and the real environment significantly influences the preparation and large-scale application of biochar for soil ramification. This review paper highlights the utilization of biochar in immobilizing and eliminating the heavy metals and organic pollutants from contaminated soils and factors affecting the remediation efficacy of biochar. Furthermore, the risks related to biochar application in unpolluted agricultural soils are also debated. Biochar production conditions (pyrolysis temperature, feedstock type, and residence time) and the application rate greatly influence the biochar performance in remediating the contaminated soils. Biochars prepared at high temperatures (800 °C) contained more porosity and specific surface area, thus offering more adsorption potential. The redox and electrostatic adsorption contributed more to the adsorption of oxyanions, whereas ion exchange, complexation, and precipitation were mainly involved in the adsorption of cations. Volatile organic compounds (VOCs), dioxins, and polycyclic aromatic hydrocarbons (PAHs) produced during biochar pyrolysis induce negative impacts on soil alga, microbes, and plants. A careful selection of unpolluted feedstock and its compatibility with carbonization technology having suitable operating conditions is essential to avoid these impurities. It would help to prepare a specific biochar with desired features to target a particular pollutant at a specific site. This review provided explicit knowledge for developing a cost-effective, environment-friendly specific biochar, which could be used to decontaminate targeted polluted soils at a large scale. Furthermore, future study directions are also described to ensure a sustainable and safe application of biochar as a soil improver for the reclamation of polluted soils. [ABSTRACT FROM AUTHOR]

Heavy metals and flooding are among the primary environmental factors affecting plants and microorganisms. This review separately considers the impact of heavy metal contamination of soils on microorganisms and plants, on plant and microbial biodiversity, and on plant–microorganism interactions. The use of beneficial microorganisms is considered one of the most promising methods of increasing stress tolerance since plant-associated microbes reduce metal accumulation, so the review focuses on plant–microorganism interactions and their practical application in phytoremediation. The impact of flooding as an adverse environmental factor is outlined. It has been shown that plants and bacteria under flooding conditions primarily suffer from a lack of oxygen and activation of anaerobic microflora. The combined effects of heavy metals and flooding on microorganisms and plants are also discussed. In conclusion, we summarize the combined effects of heavy metals and flooding on microorganisms and plants. [ABSTRACT FROM AUTHOR]

Purpose. The problem of heavy metal Cd pollution in the soil is still very serious. The widely used treatment measure is in situ passivation chemical remediation technology. Some studies have shown that the single application of phosphate or silicate can control soil cadmium pollution, but few studies have been conducted on the effect of the thermal activation temperature of nano phosphate and silicate-combined application on the transformation of Cd form in the soil. Materials and methods. Cadmium-contaminated soil was indoor-simulated, after which the 2.0% soil-weight dose of potassium dihydrogen phosphate was mixed with thermal activation nano serpentine or nano zeolite (potassium dihydrogen phosphate: thermal activation nano serpentine or nano zeolite = 1:2) at different temperatures (0, 350, 550, 700, 850 °C) and compared with the simulated cadmium-contaminated soil without adding a mixture of phosphate and silicate; cadmium content in soil was determined by Tessier five-step continuous extraction method after incubating for 0, 7, 14, 28, and 56 d in jars in the constant-temperature box. Results and discussion. Thermal activation temperature of nano phosphate and silicate could reduce the amount of exchangeable Cd content in the soil to a different degree; the content of Cd in carbonate-bound form, Fe–Mn–oxide-bound form, organically-bound form, and residual form increased. The order of effect of nanoscale potassium dihydrogen phosphate and serpentine or zeolite thermal activation temperature on remediation of Cd contaminated soil is nPS700-2.0 > nPS550-2.0 > nPS850-2.0 > nPS350-2.0 > nPS0-2.0, nPF700-2.0 > nPF550-2.0 > nPF850-2.0 > nPF350-2.0 > nPF0-2.0 (n, P, S, and F represent nanometer, KH2PO4, serpentine, and zeolite, respectively; 0, 350, 550, 700, and 850 represent different activation temperatures T); 700 °C treatments performed better than other thermal activation temperature treatments, and nPS700-2.0 was better than nPF700-2.0. Conclusion. Thermal activation temperature of nano phosphate and silicate-combined application can stabilize heavy metal Cd to some extent and promote the transition of Cd from a bioavailable state to a biounavailable state. The results showed that the combined application of thermal activation temperature of nano phosphate and silicate has a certain potential to control soil cadmium pollution. [ABSTRACT FROM AUTHOR]

In Poland's largest mining district, the Upper Silesian Coal Basin, there is a growing interest in resource development by small operators. Some concession areas are not yet directly affected by the mining industry. The objects of this research are two such areas and the goal is to determine a load of heavy metals (HM) in soils prior to mining projects and to assess the extent of their contamination at this stage. The metals studied were Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn, while HM contamination was assessed using the Contamination Factor (CF), Contamination Degree (CD), Pollution Load Index (PLI), and Geoaccumulation Index (Igeo). The Ecological Risk Potential Index (ER) and Comprehensive Potential Ecological Risk Index (PERI) were also employed. The pre-mining areas are close to an area where mining was terminated before 2000. For this area, we performed the same set of analyses as for the pre-mining areas studied. HM concentration levels and pollution indices in post-mining areas are significantly higher than in pre-mining areas. The results obtained in the post-mining area give an idea of the expected type and scale of potential threat to soils from mining and can form the basis for monitoring environmental contamination in subsequent investment and operation phases, as well as help develop and implement timely methods to prevent the increase in heavy metal immission to soils during mining activities. We believe that the presented approach of assessing the condition of soils starting at the pre-mining stage can support the sustainable management of energy resources in the cases studied and elsewhere. [ABSTRACT FROM AUTHOR]

Symbiotic associations with arbuscular mycorrhizal fungi (AMF) offer an effective indirect mechanism to reduce heavy metal (HM) stress; however, it is still not clear which AMF species are more efficient as bioremediating agents. We selected different species of AMF: Rhizoglomus custos (Custos); Rhizoglomus sp. (Aznalcollar); and Rhizophagus irregularis (Intraradices), in order to study their inoculation in wheat grown in two soils contaminated with two levels of HMs; we tested the phytoprotection potential of the different AMF symbioses, as well as the physiological responses of the plants to HM stress. Plants inoculated with indigenous Aznalcollar fungus exhibited higher levels of accumulation, mainly in the shoots of most of the HM analyzed in heavily contaminated soil. However, the plants inoculated with the non-indigenous Custos and Intraradices showed depletion of some of the HM. In the less-contaminated soil, the Custos and Intraradices fungi exhibited the greatest bioaccumulation capacity. Interestingly, soil enzymatic activity and the enzymatic antioxidant systems of the plant increased in all AMF treatments tested in the soils with both degrees of contamination. Our results highlight the different AMF strategies with similar effectiveness, whereby Aznalcollar improves phytoremediation, while both Custos and Intraradices enhance the bioprotection of wheat in HM-contaminated environments. [ABSTRACT FROM AUTHOR]

This work is a novel trial to integrate geostatistics with fuzzy logic under the geographic information system (GIS) environment to model soil pollution. Soil samples from seventy-one soil profiles in the northern Nile Delta, Egypt, and were analyzed for total concentrations of Cd, Co, Cu, Pb, Ni, and Zn. Metal distribution maps were generated using ordinary kriging methods. They were normalized by linear and non-linear fuzzy membership functions (FMFs) and overlain by fuzzy operators (And, OR, Sum, Product, and Gamma). The final maps were validated using the area under the curve (AUC) of the receiver operating characteristic (ROC). The best-fitted semivariogram models were Gaussian for Cd, Pb, and Ni, circular for Co and Zn, and exponential for Cu. The ROC and AUC analysis revealed that the non-linear FMFs were more effective than the linear functions for modeling soil pollution. Overall, the highest AUC value (0.866; very good accuracy) resulted from applying the fuzzy Sum overly to the non-linearly normalized layers, implying the superiority of this model for decision-making in the studied area. Accordingly, 92% of the investigated soils were severely polluted. Our study would increase insight into soil metal pollution on a regional scale, especially in arid regions. [ABSTRACT FROM AUTHOR]

Cadmium (Cd) or nickel (Ni) were applied as a foliar spray (1 µM solution over one month) to mimic air pollution and to monitor metabolic responses and oxidative stress in the pteridophyte species. Exogenous metals did not affect the metal content of the soil and had relatively little effect on the essential elements in leaves or rhizomes. The amounts of Cd and Ni were similar in treated leaves (7.2 µg Cd or 5.3 µg Ni/g DW in mature leaves compared with 0.4 µg Cd or 1.2 µg Ni/g DW in the respective control leaves), but Ni was more abundant in rhizomes (56.6 µg Ni or 3.4 µg Cd/g DW), resulting in a higher Cd translocation and bioaccumulation factor. The theoretical calculation revealed that ca. 4% of Cd and 5.5% of Ni from the applied solution per plant/pot was absorbed. Excess Cd induced stronger ROS production followed by changes in SOD and CAT activities, whereas nitric oxide (NO) stimulation was less intense, as detected by confocal microscopy. The hadrocentric vascular bundles in the petioles also showed higher ROS and NO signals under metal excess. This may be a sign of increased ROS formation, and high correlations were observed. Proteins and amino acids were stimulated by Cd or Ni application in individual organs, whereas phenols and flavonols were almost unaffected. The data suggest that even low levels of exogenous metals induce an oxidative imbalance, although no visible damage is observed, and that the responses of ferns to metals are similar to those of seed plants or algae. [ABSTRACT FROM AUTHOR]

One of the most significant challenges that global decision-makers are concerned about is soil contamination. It is also related to food security and soil fertility. The quality of the soil and crops in Egypt are being severely impacted by the increased heavy metal content of the soils in the middle Nile Delta. In Egypt's middle Nile Delta, fifty random soil samples were chosen. Inverse distance weighting (IDW) was used to create the spatial pattern maps for four heavy metals: Cd, Mn, Pb, and Zn. The soil contamination levels in the research area were assessed using principal component analysis (PCA), contamination factors (CF), the geoaccumulation index (I-Geo), and the improved Nemerow pollution index (In). The findings demonstrated that using PCA, the soil heavy metal concentrations were divided into two clusters. Moreover, the majority of the study region (44.47%) was assessed to be heavily to extremely polluted by heavy metals. In conclusion, integrating the contamination indices CF, I-Geo, and In with the GIS technique and multivariate model, analysis establishes a practical and helpful strategy for assessing the hazard of heavy metal contamination. The findings could serve as a basis for decision-makers to create effective heavy metal mitigation efforts. [ABSTRACT FROM AUTHOR]

Forest fires are a major concern in Mediterranean areas, where factors such as slope and aspect determine the degree of water and nutrient retention and their availability in soil. In this work, we analysed the effects of slope and aspect on minor soil elements. The study area was located in Ódena (NE Iberian Peninsula) in a typical Mediterranean forest. Four geomorphologically representative and contrasting soil profiles were sampled from different slopes and aspects. Eleven samples were taken from each profile at different depths. The amount of extractable aluminium (Al), iron (Fe), manganese (Mn), zinc (Zn), boron (B), and lead (Pb) and the calcium (Ca):Al ratio in all horizons of each profile were determined. The results showed that Al, Fe, and Pb and the Ca:Al ratio were mainly affected by slope, whereas Mn, Zn, and B were especially conditioned by aspect. This type of study aims to determine which areas have to be managed in order to avoid not only soil contamination by heavy metals but also a shortage of certain essential nutrients for plant regeneration and, thus, improved soil quality. [ABSTRACT FROM AUTHOR]

Heavy metal contamination in agricultural land is an alarming issue in Vietnam. It is necessary to develop suitable remediation methods for environmental and farming purposes. The present study investigated the effectiveness of using peanut shell-derived biochar to remediate the two heavy metals Zn and Pb in laboratory soil assays following Tessier's sequential extraction procedure. The concentration of heavy metals was analyzed using Inductively coupled plasma mass spectrometry (ICP-MS). This study also compared the effectiveness of the blend of biochar and apatite applied and the mere biochar amendment on the chemical fractions of Pb and Zn in the contaminated agricultural soil. Results have shown that the investigated soil was extremely polluted by Pb (3047.8 mg kg−1) and Zn (2034.3 mg kg−1). In addition, the pH, organic carbon, and electrical conductivity values of amended soil samples increased with the increase in the amendment's ratios. The distribution of heavy metals in soil samples was in the descending order of carbonate fraction (F2) > residue fraction (F5) > exchangeable fraction (F1) > Fe/Mn oxide fraction (F3) > organic fraction (F4) for Pb and F5   ≈   F2 > F1 > F3 > F4 for Zn. The peanut shell-derived biochar produced at 400 °C and 600 °C amended at a 10% ratio (PB4:10 and PB6:10) could significantly reduce the exchangeable fraction Zn from 424.82 mg kg−1 to 277.69 mg kg−1 and 302.89 mg kg−1, respectively, and Pb from 495.77 mg kg−1 to 234.55 mg kg−1 and 275.15 mg kg−1, respectively, and immobilize them in soil. Amending the biochar and apatite combination increased the soil pH, then produced a highly negative charge on the soil surface and facilitated Pb and Zn adsorption. This study shows that the amendment of biochar and biochar blended with apatite could stabilize Pb and Zn fractions, indicating the potential of these amendments to remediate Pb and Zn in contaminated soil. [ABSTRACT FROM AUTHOR]

Pseudomonas biofilms have been studied intensively for several decades and research outcomes have been successfully implemented in various medical and agricultural applications. Research on biofilm synthesis and composition has also overlapped with the objectives of environmental sciences, since biofilm components show exceptional physicochemical properties applicable to remediation techniques. Especially, exopolysaccharides (ExPs) have been at the center of scientific interest, indicating their potential in solving the environmental issues of heavy metal land and water contamination via sorptive interactions and flocculation. Since exposure to heavy metal via contaminated water or soil poses an imminent risk to the environment and human health, ExPs provide an interesting and viable solution to this issue, alongside other effective and green remedial techniques (e.g., phytostabilization, implementation of biosolids, and biosorption using agricultural wastes) aiming to restore contaminated sites to their natural, pollution-free state, or to ameliorate the negative impact of heavy metals on the environment. Thus, we discuss the plausible role and performance of Pseudomonas ExPs in remediation techniques, aiming to provide the relevant available and comprehensive information on ExPs' biosynthesis and their usage in heavy metal remediation or other environmental applications, such as wastewater treatment via bioflocculation and soil remediation. [ABSTRACT FROM AUTHOR]

Soil and air pollution are main problems posing a serious threat to human health. Traditional physical and chemical soil remediation methods affect the soil ecosystem and are rather costly. Since the main purpose of soil remediation is not only to remove pollutants but also to restore soil health, the method of phytoremediation is becoming extremely relevant. Phytoremediation is an environmentally friendly and natural process of removing pollutants from the environment. Cleaning up contaminated sites and enabling re-use without harming future users requires the implementation of environmentally friendly and economically attractive technologies. Phytoremediation does not adversely affect the structure and biological life of the soil. Concerning on-site cleaning in situ. Hyperaccumulator plants can accumulate heavy metals from the soil, which is the so-called phytoextraction. The ability of trees and shrubs to effectively remove solid particles from the air has also been proven. However, it is not always possible to grow large plants in polluted areas. Therefore, the main goal of the research was to explore previous studies on the phytoremediation capability of herbaceous plants, in particular, their phytoextraction capacity. Another major issue was to study the main methods of improving plant phytoextraction. The results obtained show that grass can be a good solution for natural ecosystem cleanup. It is also necessary to pay attention to the impact of phytoextraction-improving substances on soil health. [ABSTRACT FROM AUTHOR]

The promotion and gradual replacement of fossil fuels with renewable sources increasing the competition between food and fuel. Therefore, energy crops could be produced on unproductive marginal land due to unfavorable conditions, such as limitations in nutrient and water availability or the presence of contaminants such as hydrocarbons or heavy metals. In the case of soils contaminated with heavy metals, one option could be the use of plants to extract or immobilize the contaminants in the soil in a process called phytoremediation. Carthamus tinctorius L. is an annual herbaceous plant with a deep root system, and the oil extracted from the seeds is an excellent oil for conversion into biofuel. It appears suitable to be used in the phytoremediation process, increasing the opportunity to valorize polluted areas and reducing the risk of abandonment of these lands. In this study, C. tinctorius was tested in soils contaminated with zinc, cadmium, lead, and nickel at different concentrations to evaluate the effects on yield and heavy metal content in the different parts of the plant. The experiment highlights the tolerance of Safflower to the cultivation in heavy-metal-polluted soil; in fact, a low reduction in biomass yield was observed. Among the evaluated heavy metals, the higher susceptibility was observed at the highest concentrations of zinc and cadmium. Generally, safflower concentrates heavy metals in the belowground biomass. The relative low concentrations of heavy metals in some parts of the aboveground biomass could suggest the possibility of using it as a feedstock for bioenergy conversion. [ABSTRACT FROM AUTHOR]

Coal mining activities have a series of impacts on the local eco-environment, such as air pollution due to the release of toxic gases, contamination of soil with heavy metals, disturbance and contamination of surface and subsurface water, and damage to land resources with surface subsidence and accumulation of solid waste materials. This study investigated the distribution of heavy metals in mining sites by analyzing the heavy metal content in soil samples from different sites in the Dahuangshan mining area of the southern Junggar coalfield (Xinjiang, China). The results show that area C has the highest Cu content; and area B has the highest Mn content, the highest Zn content, the highest As content, and the highest Cd content, which indicate that area B underwent potential multiple heavy metal contamination. It also shows that the Cd is the major heavy metal for all three areas. The different eco-environmental indices, including the Nemerow comprehensive pollution index, the geo-accumulation index, and the potential ecological risk index, all show the same results, i.e., that Cd is the major potential contaminant in all three types of soil. [ABSTRACT FROM AUTHOR]

The aim of this study was to determine the activity and structure of microbial communities in soils contaminated with heavy metals (HMs). To achieve this goal, soil samples were taken from two contaminated sites (i.e., Piekary Śląskie and Bukowno) in Poland. A wide range of methods were applied, including: total and metal-tolerant culturable bacteria enumeration; microbial community structure analysis using the phospholipid fatty acid method (PLFA); denaturing gradient gel electrophoresis (PCR-DGGE); and metabolic activity using BIOLOG and EcoPlateTM. Our studies showed that HMs negatively affected microbial community structure and activity in polluted soils. Apart from the contamination with HMs, other soil parameters like soil pH and water also impacted microbial community structure and growth. Metal-tolerant bacterial strains were isolated, identified and tested for presence of genes encoding HM tolerance using the polymerase chain reaction (PCR) methodology. Contamination with HMs in the tested areas was found to lead to development of metallotolerant bacteria with multiple tolerances toward Zn, Ni, Cd and Cu. Different genes (e.g., czcA, cadA and nccA) encoding HM efflux pumps were detected within isolated bacteria. Culturable bacteria isolated belonged to Proteobacteria, Actinobacteria and Bacteroidetes genera. Among non-culturable bacteria in soil samples, a significant fraction of the total bacteria and phyla, such as Gemmatimonadetes and Acidobacteria, were found to be present in all studied soils. In addition, bacteria of the Chloroflexi genus was present in soil samples from Piekary Śląskie, while bacteria of the Firmicutes genus were found in soil samples from Bukowno. [ABSTRACT FROM AUTHOR]