Various types of biochar have been widely used to remediate soil contamination from heavy metals (HMs) and to reduce HM mobility and bioavailability in soils in recent years. Most researchers have ...paid attention to the beneficial effects of biochar during the remediation process, but few have emphasized their negative effects and the challenges for their application. In this review, the negative effects and challenges of applying biochar for the remediation of HM-contaminated soils are thoroughly summarized and discussed, including the changeable characteristics of biochar, biochar over-application, toxic substances in biochar, activation of some HMs in soils by biochar, nonspecific adsorption, and the negative influences of biochar on soil microorganisms and plants. In addition, further research directions and several recommendations (standardization, long-term field experiments, mechanisms research and designer biochars) were also proposed to enable the large-scale application of biochar for the remediation of HM-contaminated soils.
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•This manuscript reviewed the potential challenges of biochar in remediation of HMs.•The changeable properties of biochar inhibit the application of biochar.•Further research directions and some recommendations are proposed.•Biochars is still a low-cost and environmentally friendly amendment for HM remediation.
The occurrence of pesticides in soil has become a highly significant environmental problem, which has been increased by the vast use of pesticides worldwide and the absence of remediation ...technologies that have been tested at full-scale. The aim of this review is to give an overview on technologies really studied and/or developed during the last years for remediation of soils contaminated by pesticides. Depending on the nature of the decontamination process, these techniques have been included into three categories: containment-immobilization, separation or destruction. The review includes some considerations about the status of emerging technologies as well as their advantages, limitations, and pesticides treated. In most cases, emerging technologies, such as those based on oxidation-reduction or bioremediation, may be incorporated into existing technologies to improve their performance or overcome limitations. Research and development actions are still needed for emerging technologies to bring them for full-scale implementation.
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•Many soils impacted by pesticide pollution due to their increasing use worldwide•Point-source or diffuse pollution define the selected technology.•The majority of scientific studies are still at the lab-scale stage.•Lack of full-scale remediation technologies based on their complete degradation•Scaling up new technologies is needed to know their real cost and efficacy.
Microplastic contamination in soil has received increasing attention since excessive plastic debris has been emitted directly into the terrestrial environment. Once released into the terrestrial ...environment, microplastics can be aged via photo- and thermally-initiated oxidative degradation, hetero-aggregation, and bioturbation. Aging affects the physiochemical properties of microplastics with the increase of surface roughness and oxygen-containing groups, which could enhance the sorption and mobility of microplastics in the soil and groundwater environment. However, the interactions among aging, sorption, and transport of microplastics in the terrestrial system have not been unveiled. This review clarifies the key processes of microplastics transport pathways in soil and groundwater ecosystems influenced by aging and sorption under various scenarios. Co-transport of microplastics and sorbed contaminants are also addressed to help understand the risks associated with heavy metals, organic contaminants, and engineered nanoparticles in the soil environment. Overall, this review elaborates the most pressing research limitations on the present literature and highlights the future perspectives to investigate the possible broad transport pathways of microplastics in soil.
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•Aging significantly changes physiochemical properties of microplastics.•The transport of aged microplastics was enhanced in the soil-groundwater environment.•Microplastics can co-transport with soil contaminants by serving as vectors.•Microplastics may transport into groundwater and thus increase the potential risk.
Soil contamination is one of the main threats to ecosystem health and sustainability. Yet little is known about the extent to which soil contaminants differ between urban greenspaces and natural ...ecosystems. Here we show that urban greenspaces and adjacent natural areas (i.e., natural/semi-natural ecosystems) shared similar levels of multiple soil contaminants (metal(loid)s, pesticides, microplastics, and antibiotic resistance genes) across the globe. We reveal that human influence explained many forms of soil contamination worldwide. Socio-economic factors were integral to explaining the occurrence of soil contaminants worldwide. We further show that increased levels of multiple soil contaminants were linked with changes in microbial traits including genes associated with environmental stress resistance, nutrient cycling, and pathogenesis. Taken together, our work demonstrates that human-driven soil contamination in nearby natural areas mirrors that in urban greenspaces globally, and highlights that soil contaminants have the potential to cause dire consequences for ecosystem sustainability and human wellbeing.
Potentially toxic elements such as heavy metals are ubiquitous in the environment. Risk-based environmental management relies upon identifying pollution sources, pathways, and the exposed population. ...In a Chinese urban setting, many residents live in high-rise buildings without private gardens. Therefore, the main residential risk of exposure to contaminated soils and dusts may be associated with public open spaces. As children are the most vulnerable receptor, playgrounds represent an important yet often overlooked exposure point. The present study assessed plausible sources of heavy metals at children's playgrounds in a representative metropolitan environment. Soil and equipment dust samples were collected from 71 playgrounds across Beijing, which were analyzed for 11 different heavy metals. Principal component analysis (PCA) was used to identify the latent constructs which control heavy metal variability and reflect potential sources. Cluster analysis (CA) was conducted to group sampled locations, which provided further insights on plausible sources. The main factors extracted from the PCA were then subject to geostatistical analysis. The systematic combination of GIS with multivariate statistical analysis proved valuable for elucidating anthropogenic and natural sources. Elevated Be, V, Cr, Mn, Co, Ni, As in playground soils were found to derive mainly from the natural background (spatial autocorrelation = 2 km), while elevated Cu and Pb was attributed to traffic activities (spatial autocorrelation = 17 km), especially along the routes of Beijing's inner ring-roads, the major roads toward the northwest and northeast, and the international airport. These results suggest that heavy metals in playground equipment dust may derive mainly from atmospheric deposition of air pollution of both natural and anthropogenic origin (spatial autocorrelation = 11–13 km). Among them, Be, V, Mn, Co, Cu, As, Pb were attributed to atmospheric pollution deriving from the north of Beijing, brought by the prevailing northern wind in the winter season; whereas, Cr and Ni may possibly be brought from the southeast by the summer season winds. Knowledge of anthropogenic vs. natural origins of heavy metals in playgrounds is critical in assessing health impact and designing policy instruments for metropolitan areas.
•Knowledge of anthropogenic vs. natural origins of heavy metals is critical.•Systematic combination of GIS with multivariate statistical analysis proved valuable.•Playgrounds represent an important yet often overlooked exposure point.•Cu and Pb in playground soils were attributed to traffic activities.•Most heavy metals in playground dusts may naturally derive from the north of Beijing.
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•MPs impacts on Cd adsorption and desorption in a farmland soil were first studied.•Adding MPs decreased soil adsorption capacity for Cd, but increased Cd desorption.•MPs impacts ...depended on MPs dose and particle size, and solution pH.•Addition of MPs may increase the mobility of Cd in soil, resulting in additional risks.
Microplastics (MPs) in terrestrial ecosystems particularly agroecosystem are attracting increasing attention worldwide. However, the influences of MPs on adsorption and desorption of contaminants in agricultural soils remain unknown. Here, batch experiments were conducted to study the effects of polyethylene MPs on Cd adsorption and desorption in a farmland soil under varying conditions. Both Cd adsorption and desorption in soils with or without MPs reached equilibrium within 120 min. Cd adsorption kinetics followed the pseudo-second order model, and the adsorption isotherm fitted to the Langmuir model more precisely than the Freundlich model. Overall, addition of MPs decreased Cd adsorption but increased desorption, and the effects varied with MPs dose and particle size, and solution pH. MPs-induced decrease in Cd adsorption and increase in Cd desorption were more pronounced at higher MPs dose and larger particle size, but varied differently from solution pH. EDS analysis confirmed Cd adsorption on MPs surface. Both MPs before and after Cd adsorption showed similar XRD patterns, indicating MPs maintained a high crystallinity and no new crystalline phases formed. In conclusion, the input of MPs into soil might enhance the mobility of Cd via mitigating soil adsorbing capacity, thereby posing additional risks of Cd to agroecosystem.
Researchers are increasingly concerned about antimony (Sb) in ecosystems and the environment. Sb primarily enters the environment through anthropogenic (urbanization, industries, coal mining, cars, ...and biosolid wastes) and geological (natural and chemical weathering of parent material, leaching, and wet deposition) processes. Sb is a hazardous metal that can potentially harm human health. However, no comprehensive information is available on its sources, how it behaves in soil, and its bioaccumulation. Thus, this study reviews more than 160 peer-reviewed studies examining Sb's origins, geochemical distribution and speciation in soil, biogeochemical mechanisms regulating Sb mobilization, bioavailability, and plant phytotoxicity. In addition, Sb exposure effects plant physio-morphological and biochemical attributes were investigated. The toxicity of Sb has a pronounced impact on various aspects of plant life, including a reduction in seed germination and impeding plant growth and development, resulting from restricted essential nutrient uptake, oxidative damages, disruption of photosynthetic system, and amino acid and protein synthesis. Various widely employed methods for Sb remediation, such as organic manure and compost, coal fly ash, biochar, phytoremediation, microbial-based bioremediation, micronutrients, clay minerals, and nanoremediation, are reviewed with a critical assessment of their effectiveness, cost-efficiency, and suitability for use in agricultural soils. This review shows how plants deal with Sb stress, providing insights into lowering Sb levels in the environment and lessening risks to ecosystems and human health along the food chain. Examining different methods like bioaccumulation, bio-sorption, electrostatic attraction, and complexation actively works to reduce toxicity in contaminated agricultural soil caused by Sb. In the end, the exploration of recent advancements in genetics and molecular biology techniques are highlighted, which offers valuable insights into combating Sb toxicity. In conclusion, the findings of this comprehensive review should help develop innovative and useful strategies for minimizing Sb absorption and contamination and thus successfully managing Sb-polluted soil and plants to reduce environmental and public health risks.
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•This review examines antimony (Sb) entry into soil, its distribution, and chemical forms.•This describes influence of Sb exposure on plant physiology, biochemistry and growth.•The effectiveness and cost efficiency of Sb remediation strategies have been discussed.•Advances in genetic and molecular techniques to combat Sb toxicity are also described.
This comprehensive review examines recent trends in phytoremediation strategies to address soil radionuclide contamination by cesium (Cs) and strontium (Sr). Radionuclide contamination, resulting ...from natural processes and nuclear-related activities such as accidents and the operation of nuclear facilities, poses significant risks to the environment and human health. Cs and Sr, prominent radionuclides involved in nuclear accidents, exhibit chemical properties that contribute to their toxicity, including easy uptake, high solubility, and long half-lives. Phytoremediation is emerging as a promising and environmentally friendly approach to mitigate radionuclide contamination by exploiting the ability of plants to extract toxic elements from soil and water. This review focuses specifically on the removal of 90Sr and 137Cs, addressing their health risks and environmental implications. Understanding the mechanisms governing plant uptake of radionuclides is critical and is influenced by factors such as plant species, soil texture, and physicochemical properties. Phytoremediation not only addresses immediate contamination challenges but also provides long-term benefits for ecosystem restoration and sustainable development. By improving soil health, biodiversity, and ecosystem resilience, phytoremediation is in line with global sustainability goals and environmental protection initiatives. This review aims to provide insights into effective strategies for mitigating environmental hazards associated with radionuclide contamination and to highlight the importance of phytoremediation in environmental remediation efforts.
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•Soil contamination by radionuclides presents significant environmental and public health hazards.•Phytoremediation:eco-friendly method to extract cesium and strontium from soil.•Physiological and molecular mechanisms of radionuclide accumulation in plants is crucial for enhancing phytoremediation.
In the current study, we conducted a field experiment using the test plant, Brassica chinesis L. (pak choi), to investigate the effect of sugarcane bagasse-derived biochar on the bioavailability of ...cadmium (Cd), copper (Cu) and lead (Pb), and the health of soil microbiota in a contaminated soil. Biochar application significantly (P < 0.05) increased pak choi yield. Bioavailability of heavy metals to plant shoots and roots decreased with increasing biochar application rates (at 0, 1.5, 2.25 and 3.0 t ha−1). Sequential extraction of the biochar-treated and -untreated soil revealed that exchangeable Cd reduced whereas organically-bound fraction increased with increasing biochar rate. The labile fractions of Cu and Pb decreased, but the residual fraction increased in biochar-treated soils compared to the control. Urease, catalase and invertase activities, and the populations of bacteria and actinomycetes were significantly enhanced, whereas fungi population declined in biochar-treated soils. This study highlights that sugarcane bagasse biochar has the potential to support the remediation of soils contaminated with heavy metals, and as such can improve the yield and quality of agricultural crops.
•Sugarcane bagasse biochar amendment reduced availability of Cd, Cu and Pb in soils.•Heavy metals were less labile in the biochar-treated soils.•Biochar amendment induced an increase in soil enzyme and microbial activity.•Edible part of pak choi was safer for human consumption after biochar amendment.
Background: Removal of mineral pollutants from polluted soil is considered to be major environmental concern in the modern era. The present study aimed to investigate the capability of lead uptake ...and transfer in various organs of Crataegusaronia and Juniperuspolycarposseedlings and determine the effects of lead accumulation on some of the quantitative indices of these plant species. Methods: Three-year-old saplings were exposed to various concentrations of lead (zero, 200, 300, and 400 ppm) (No3)2 in the sprouting period in a completely random project in triplicate. Afterwards, the lead uptake value was measured in various organs of C. aronia and J. polycarpus (roots, stems, and leaves) using an atomic absorption device. Results: The analysis of variance indicated that the features of C. aronia and J. polycarpus saplings (e.g., stem length, basal diameter, and root length) were significantly influenced by lead contamination (P < 0.05). Moreover, the saplings of both varieties had high capacity for lead uptake in their roots, stems, and leaves. Conclusion: According to the results, the seedlings of C. aronia and J. polycarpus could be used as stabilizing varieties for the removal of lead from polluted soil. It is also notable that J. polycarpus is a more effective lead absorbent compared to C. aronia.
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