Insights into the biogeochemical transformation, environmental impacts and biochar-based soil decontamination of antimony.

Every year, a significant amount of antimony (Sb) enters the environment from natural and anthropogenic sources like mining, smelting, industrial operations, ore processing, vehicle emissions, shooting activities, and coal power plants. Humans, plants, animals, and aquatic life are heavily exposed to hazardous Sb or antimonide by either direct consumption or indirect exposure to Sb in the environment. This review summarizes the current knowledge about Sb global occurrence, its fate, distribution, speciation, associated health hazards, and advanced biochar composites studies used for the remediation of soil contaminated with Sb to lessen Sb bioavailability and toxicity in soil. Anionic metal(loid) like Sb in the soil is significantly immobilized by pristine biochar and its composites, reducing their bioavailability. However, a comprehensive review of the impacts of biochar-based composites on soil Sb remediation is needed. Therefore, the current review focuses on (1) the fundamental aspects of Sb global occurrence, global soil Sb contamination, its transformation in soil, and associated health hazards, (2) the role of different biochar-based composites in the immobilization of Sb from soil to increase biochar applicability toward Sb decontamination. The review aids in developing advanced, efficient, and effective engineered biochar composites for Sb remediation by evaluating novel materials and techniques and through sustainable management of Sb-contaminated soil, ultimately reducing its environmental and health risks.

Influence of biochar produced from negative pressure-induced carbonization on transformation of potentially toxic metal(loid)s concerning plant physiological characteristics in industrially contaminated soil.

Soil contamination and its subsequent impact on the food chain is a pressing challenge in the present day. The application of biochar has demonstrated a significant and positive effect on soil health, thereby enhancing plant growth and development. However, the application of biochar (BC) produced from negative pressure-induced carbonization to mitigate metal(loid) contamination is a new strategy that has been studied in current research. Results depicted that the application of biochar derived from the negative pressure carbonization (vacuum-assisted biochar (VBC) has a significant (p ≤ 0.05) positive impact on plant growth and physiological characteristics by influencing immobilization and speciation of metal(loid) in the soil system. Moreover, the interactive effect of VBC on physiological characteristics (photosynthesis, gas exchange, and chlorophyll contents) and antioxidant activities of maize (Zea mays L.) was significantly (p ≤ 0.05) positive by confining the translocation and movement of metal(loid)s to the aerial part of the maize plant. X-ray diffraction (XRD) provided information on the structural and chemical changes induced by the VBC-500 °C explaining metal(loid) adsorption onto mineral surfaces and complexation that can affect their mobility, availability, and toxicity in the contaminated soil. Fourier transform infrared spectroscopy (FTIR) further provided a more detailed understanding of the metal(loid)s and biochar complexation mechanisms influenced by VBC-based functional groups -OH, C-Hn, -COOH, CO, C-O-C, CC, C-O, C-H, OH, and C-C in the binding process. These results suggest that the application of biochar prepared at 500 °C under negative pressure-induced carbonization conditions to the soil is the most efficient way to reduce the uptake and transfer of metal(loid)s by influencing their mobility and availability in the soil-plant system.

Spectroscopic fingerprinting, pollution characterization, and health risk assessment of potentially toxic metals from urban particulate matter.

The unprecedented stride of urbanization and industrialization has given rise to anthropogenic input of tiny particulates into the air. Urban particulate matter (PM) armored with potentially toxic metals (PTMs) could be lethal to the environment and human health. Therefore, the present study was planned to investigate the spectroscopic fingerprinting, pollution status and health risk of PM-associated PTMs collected from ten functional areas of Lahore, Pakistan. The diverged results of studied qualitative and quantitative analyses showed distinct compositional and pollution characteristics of PTMs in urban PM with respect to selected functional areas. The XRD results evident the fractional presence of metal-containing minerals, i.e., pyrite (FeS2), calcite (CaCO3), zinc sulfate (ZnSO4), and chalcostibite (CuSbS2). Several chemical species of Zn, Pb, and As were found in PM of various functional areas. However, morphologies of PM showed anthropogenic influence with slight quantitative support of PTMs presence. The cumulative representation of PTMs pollution of all selected areas depicted that Cd was heavily polluted (Igeo=3.21) while Cr (Igeo=1.82) and Ni (Igeo=2.11) were moderately polluted PTMs. The industrial area having high pollution status of Cd (Igeo=5.54 and EF=18.07), Cu (Igeo=6.4 and EF=32.61), Cr (Igeo=4.03 and EF=6.53), Ni (Igeo=5.7 and EF=20.17), and Zn (Igeo=4.87 and EF=11.27) was prominent among other studied areas. The PTMs were likely to pose a high non-cancerous risk in IndAr (HI = 7.48E+00) and HTV (HI = 1.22E +00) areas predominantly due to Zn with HQ > 1. However, Cr was prominent to cause cancerous risks with values beyond the tolerable range (1.00E-04 to 1.00E-06).

Impregnation of biochar with montmorillonite and its activation for the removal of azithromycin from aqueous media.

An inexpensive and environmentally friendly composite synthesized from rice husk, impregnated with montmorillonite and activated by carbon dioxide, was investigated for the removal of azithromycin from an aqueous solution. Various techniques were used to characterize adsorbents in detail. The sorption process was primarily regulated by the solution pH, pollutant concentration, contact duration, adsorbent dose, and solution temperature. The equilibrium data were best analyzed using the nonlinear Langmuir and Sips (R2 > 0.97) isotherms, which revealed that adsorption occurs in a homogenous manner. The adsorption capacity of pristine biochar and carbon dioxide activated biochar-montmorillonite composite was 33.4 mg g-1 and 44.73 mg g-1, respectively. Kinetic studies identified that the experimental data obeyed the pseudo-second-order and Elovich models (R2 > 0.98) indicating the chemisorption nature of adsorbents. The thermodynamic parameters determined the endothermic and spontaneous nature of the reaction. The ion exchange, π-π electron-donor-acceptor (EDA) interactions, hydrogen-bonding, and electrostatic interactions were the plausible mechanisms responsible for the adsorption process. This study revealed that a carbon dioxide activated biochar-montmorillonite composite may be used as an effective, sustainable, and economical adsorbent for the removal of azithromycin from polluted water.

Biogeochemical behaviour and toxicology of chromium in the soil-water-human nexus: A review.

Chromium (Cr) affects human health if it accumulates in organs to elevated concentrations. The toxicity risk of Cr in the ecosphere depends upon the dominant Cr species and their bioavailability in the lithosphere, hydrosphere, and biosphere. However, the soil-water-human nexus that controls the biogeochemical behaviour of Cr and its potential toxicity is not fully understood. This paper synthesizes information on different dimensions of Cr ecotoxicological hazards in the soil and water and their subsequent effects on human health. The various routes of environmental exposure of Cr to humans and other organisms are also discussed. Human exposure to Cr(VI) causes both carcinogenic and non-carcinogenic health effects via complicated reactions that include oxidative stress, chromosomal and DNA damage, and mutagenesis. Chromium(VI) inhalation can cause lung cancer; however, incidences of other types of cancer following Cr(VI) exposure are low but probable. The non-carcinogenic health consequences of Cr(VI) exposure are primarily respiratory and cutaneous. Research on the biogeochemical behaviour of Cr and its toxicological hazards on human and other biological routes is therefore urgently needed to develop a holistic approach to understanding the soil-water-human nexus that controls the toxicological hazards of Cr and its detoxification.

Role of biochar-based free radicals in immobilization and speciation of metals in the contaminated soil-plant environment.

The structure of biochar produced at various pyrolysis temperatures influences metal geochemical behavior. Here, the impact of wheat straw-derived biochar (300, 500, and 700 °C) on the immobilization and transformation of metals in the contaminated soil-plant system was assessed. The findings of the sequential extraction revealed that biochar additives had a substantial influence on the speciation of Cr, Ni, Pb, and Zn in the contaminated soil. The lowest F1 (exchangeable and soluble fraction) + F2 (carbonate fraction) accounted for Cr (44%) in WB-300, Ni (43.87%) in WB-500, Pb (43.79%), and Zn (49.78%) in WB-700 with applied amendments of their total amounts. The characterization results indicated that high pyrolysis temperatures (300-700 °C) increased the carbon-containing groups with the potential to adsorb metals from the soil-plant environment. The bioconcentration and translocation factors (BCF and TF) were less than 1, indicating that metal concentration was restricted to maize roots and translocation to shoots. Reactive oxygen species (ROS) intracellularly influence metal interactions with plants. Electron paramagnetic resonance (EPR) was performed to determine hydroxyl radical generation (•OH) in plant segments to assess the dominance of free radicals (FRs). Consequently, the formation of •OH significantly depends on the pyrolysis temperature and the interaction with a contaminated soil-plant environment. Thus, metal transformation can be effectively decreased in the soil-plant environment by applying WB amendments.

A critical review on biochar-assisted free radicals mediated redox reactions influencing transformation of potentially toxic metals: Occurrence, formation, and environmental applications.

Potentially toxic metals have become a viable threat to the ecosystem due to their carcinogenic nature. Biochar has gained substantial interest due to its redox-mediated processes and redox-active metals. Biochar has the capacity to directly adsorb the pollutants from contaminated environments through several mechanisms such as coprecipitation, complexation, ion exchange, and electrostatic interaction. Biochar's electron-mediating potential may be influenced by the cyclic transition of surface moieties and conjugated carbon structures. Thus, pyrolysis configuration, biomass material, retention time, oxygen flow, and heating time also affect biochar's redox properties. Generally, reactive oxygen species (ROS) exist as free radicals (FRs) in radical and non-radical forms, i.e., hydroxyl radical, superoxide, nitric oxide, hydrogen peroxide, and singlet oxygen. Heavy metals are involved in the production of FRs during redox-mediated reactions, which may contribute to ROS formation. This review aims to critically evaluate the redox-mediated characteristics of biochar produced from various biomass feedstocks under different pyrolysis conditions. In addition, we assessed the impact of biochar-assisted FRs redox-mediated processes on heavy metal immobilization and mobility. We also revealed new insights into the function of FRs in biochar and its potential uses for environment-friendly remediation and reducing the dependency on fossil-based materials, utilizing local residual biomass as a raw material in terms of sustainability.

In vivo phytotoxic effect of yttrium-oxide nanoparticles on the growth, uptake and translocation of tomato seedlings (Lycopersicon esculentum).

The potential toxicity and ecological risks of rare-earth nanoparticles in the environment have become a concern due to their widespread application and inevitable releases. The integration of hydroponics experiments, partial least squares structural equation modeling (PLS-SEM), and Transmission Electron Microscopy (TEM) were utilized to investigate the physiological toxicity, uptake and translocation of yttrium oxide nanoparticles (Y2O3 NPs) under different hydroponic treatments (1, 5, 10, 20, 50 and 100 mg·L-1 of Y2O3 NPs, 19.2 mg·L-1 Y(NO3)3 and control) in tomato (Lycopersicon esculentum) seedlings. The results indicated that Y2O3 NPs had a phytotoxic effect on tomato seedlings' germination, morphology, physiology, and oxidative stress. The Y2O3 NPs and soluble YIII reduced the root elongation, bud elongation, root activity, chlorophyll, soluble protein content and superoxide dismutase and accelerated the proline and malondialdehyde in the plant with increasing concentrations. The phytotoxic effects of Y2O3 NPs on tomato seedlings had a higher phytotoxic effect than soluble YIII under the all treatments. The inhibition rates of different levels of Y2O3 NPs in shoot and root biomass ranged from 0.2% to 6.3% and 1.0-11.3%, respectively. The bioaccumulation and translocation factors were less than 1, which suggested that Y2O3 NPs significantly suppressed shoot and root biomass of tomato seedlings and easily bioaccumulated in the root. The observations were consistent with the process of concentration-dependent uptake and translocation factor and confirmed by TEM. Y2O3 NPs penetrate the epidermis, enter the cell wall, and exist in the intercellular space and cytoplasm of mesophyll cells of tomato seedlings by endocytic pathway. Moreover, PLS-SEM revealed that the concentration of NPs significantly negatively affects the morphology and physiology, leading to the change in biomass of plants. This study demonstrated the possible pathway of Y2O3 NPs in uptake, phytotoxicity and translocation of Y2O3 NPs in tomato seedlings.

Assessing the influence of sewage sludge and derived-biochar in immobilization and transformation of heavy metals in polluted soil: Impact on intracellular free radical formation in maize.

As one of the most common ways to get rid of municipal waste, landfill leachate, waste with complicated compositions and high levels of contaminants, has become a significant threat to the world's environment. Here, the impact of sewage sludge (SS) and derived-biochar (SSB) amendments on the immobilization and potential mobility of heavy metals in a contaminated soil-plant system was investigated. The sequential fractionation findings showed that using SS-2%, SSB-2%, and SSBC-1% reduced the potential mobility of heavy metals while increasing the residual fraction in polluted soils. The translocation and bioconcentration factors showed that heavy metals were slightly transferred into shoots from roots and lowered accumulation in roots from contaminated soils. Fourier transform infrared (FTIR) and X-ray photoelectron spectrum (XPS) comprehensive characterization results indicated the significant role of applied amendments for heavy metals transformation from the exchangeable-soluble fractions to the least available form by lowering their mobility to confirm the adsorption-based complexes, which results in the surface adsorption of heavy metals with functional groups. The electron paramagnetic resonance (EPR) results indicated the dominance of reactive oxygen species (ROS) in the intracellular formation of hydroxyl radicals (•OH) in maize plant roots and shoots. ROS (•OH) generation plays a critical influence in the interaction between the physiological processes of plants and heavy metals. Moreover, all the amendments increased maize growth and biomass production. Our study suggests that alone and combined application of SS and SSB have great potential to remediate heavy metals contaminated soil for environmental sustainability.

Effects of the COVID-19 pandemic on the environment, waste management, and energy sectors: a deeper look into the long-term impacts.

The COVID-19 pandemic not only has caused a global health crisis but also has significant environmental consequences. Although many studies are confirming the short-term improvements in air quality in several countries across the world, the long-term negative consequences outweigh all the claimed positive impacts. As a result, this review highlights the positive and the long-term negative environmental effects of the COVID-19 pandemic by evaluating the scientific literature. Remarkable reduction in the levels of CO (3 - 65%), NO2 (17 - 83%), NOx (24 - 47%), PM2.5 (22 - 78%), PM10 (23 - 80%), and VOCs (25 - 57%) was observed during the lockdown across the world. However, according to this review, the pandemic put enormous strain on the present waste collection and treatment system, resulting in ineffective waste management practices, damaging the environment. The extensive usage of face masks increased the release of microplastics/nanoplastics (183 to 1247 particles piece-1) and organic pollutants in land and water bodies. Furthermore, the significant usages of anti-bacterial hand sanitizers, disinfectants, and pharmaceuticals have increased the accumulation of various toxic emerging contaminants (e.g., triclocarban, triclosan, bisphenol-A, hydroxychloroquine) in the treated sludge/biosolids and discharged wastewater effluent, posing great threats to the ecosystems. This review also suggests strategies to create long-term environmental advantages. Thermochemical conversions of solid wastes including medical wastes and for treated wastewater sludge/biosolids offer several advantages through recovering the resources and energy and stabilizing/destructing the toxins/contaminants and microplastics in the precursors.

Fungi-derived agriculturally important nanoparticles and their application in crop stress management - Prospects and environmental risks.

Nanotechnology has a wide range of agricultural applications, with emphasize on the development of novel nano-agrochemicals such as, nano-fertilizer and nano-pesticides. It has a significant impact on sustainable agriculture by increasing agricultural productivity, while reducing the use of inorganic fertilizers, pesticides, and herbicides. Nano-coating delivery methods for agrochemicals have improved agrochemical effectiveness, safety, and consistency. Biosynthesis of nanoparticles (NPs) has recently been recognized as an effective tool, contrary to chemically derived NPs, for plant abiotic and biotic stress control, and crop improvement. In this regard, fungi have tremendous scope and importance for producing biogenic NPs of various sizes, shapes, and characteristics. Fungi are potential candidates for synthesis of biogenic NPs due to their enhanced bioavailability, biological activity, and higher metal tolerance. However, their biomimetic properties and high capacity for dispersion in soil, water environments, and foods may have negative environmental consequences. Furthermore, their bioaccumulation raises significant concerns about the novel properties of nanomaterials potentially causing adverse biological effects, including toxicity. This review provides a concise outline of the growing role of fungal-mediated metal NPs synthesis, its potential applications in crop field, and associated issues of nano-pollution in soil and its future implications.

Modified and pristine biochars for remediation of chromium contamination in soil and aquatic systems.

Chromium (Cr) contamination in soil and water poses high toxicity risks to organisms and threatens food and water security worldwide. Biochar has emerged as a promising material for cleaning up Cr contamination owing to biochar's strong capacity to immobilize Cr. This paper synthesizes information on biochar modification for the efficient remediation of Cr contamination in soil and water, and critically reviews mechanisms of Cr adsorption on pristine and modified biochars. Biochar modification methods include physical activation via ball milling or ultraviolet irradiation, chemical activation via magnetization, alkali/acid treatment, nano-fabrication or loading of reductive agents, and biological activation via integrating biochars with microorganisms and their metabolites. Modified biochars often have multi-fold enhancement in Cr adsorption/reduction capacity than pristine biochars. Iron (Fe)-supported magnetic biochars have the most promising Cr removal abilities with high reusability of the biochars. Pre-pyrolysis modification with Fe could load Fe3O4 micro-/nanoparticles on biochars, and increase the surface area and electrostatic attraction between chromate anions and biochar surfaces, and reduce Cr(VI) to Cr(III). Post-pyrolysis modification could enrich oxygen-containing functional groups such as CO and -OH on biochar surfaces and promote Cr reduction and adsorption. Future research directions for Cr mitigation using advanced biochar products are discussed in this review.

Morphochemical investigation on the enrichment and transformation of hazardous elements in ash from waste incineration plants.

The transformation of heavy metals in ash from waste incineration plants is significant for ash management. The migration behavior of trace elements in ash after combustion, semidry deacidification, fabric filtration, and chelating agent stabilization was investigated from one waste incineration plant. The hazardous elements Zn, Pb, and As were enriched in raw fly ash (ash produced at a combustion temperature of 850-1100 °C) due to their relatively high volatility. Mercury, Cd, and Pb were captured in fly ash2 and processed by activated carbon and fabric filters. The removal rate of As (71%) was the highest among all studied elements due to a large amount of quinquevalent As removed. However, the average removal rate of elements in fly ash was only 13%. In the finally obtained fly ash3 (after chelating agent stabilization), a larger particle size (~100 µm) was found than that of raw ash. Furthermore, fly ash3 contains HgSO4 and trivalent As, which are toxic and likely to be precipitated when the fly ash3 is next utilized or deposited in a landfill, causing environmental risks.

Phyto-mediated photocatalysis: a critical review of in-depth base to reactive radical generation for erythromycin degradation.

Erythromycin (ERY), designated as a risk-prioritized macrolide antibiotic on the 2015 European Union watch list, is the third most commonly used antibiotic, most likely due to its ability to inhibit the protein. ERY has revealed record-high aquatic concentrations threatening the entire ecosystem and hence demands priority remedial measures. The inefficiency of various conventional ERY degradation methodologies opened up a gateway to advanced technologies. The conventional approach comprising of a chemically formulated, single photocatalyst has a major drawback of creating multiple environmental stresses. In this context, photocatalysis is grabbing tremendous attention as an efficient and cost-effective antibiotic treatment approach. Several studies have ascertained that ZnO, TiO2, Fe3O4, and rGO nanoparticles possess remarkable pollution minimizing operational capabilities. Additionally, composites are found much more effective in antibiotic removal than single nanoparticles. In this review, an attempt has been made to provide a comprehensive baseline for efficient reactive radical production by a phyto-mediated composite kept under a certain source of irradiation. Considerable efforts have been directed towards the in-depth investigation of rGO-embedded, phyto-mediated ZnO/TiO2/Fe3O4 photocatalyst fabrication for efficient ERY degradation, undergoing green photocatalysis. This detailed review provides photocatalytic nanocomposite individualities along with a hypothetical ERY degradation mechanism. It is assumed that derived information presented here will provoke innovative ideas for water purification incorporating green photocatalysis, initiating the construction of high-performance biogenic hierarchical nanocatalysts.

Vulnerability of municipal solid waste: An emerging threat to aquatic ecosystems.

Dumping waste materials into aquatic ecosystems leads to pollution, which directly and indirectly poses a danger to all life forms. Currently, huge quantities of wastes are generated at a global scale with varying constituents, including organic fractions, emerging contaminants and toxic metals. These wastes release concentrated contaminants (leachates), which are lethal for all ecosystems around the globe because they contain varying concentrations of chemical constituents with BOD5 and COD in the order of 2 × 104-2.7 × 104 mg/L, and 3.4 × 104-3.8 × 104 mg/L, respectively. Herein, in-depth knowledge of municipal solid waste dumping into the aquatic ecosystems, changes in physicochemical characteristics, availability of in-/organic contaminants, and long-term unhealthy effects are presented. Moreover, an attempt has been made here to summarize the facts related to identifying the deadly impacts of waste on different ecosystem components. The unresolved challenges of municipal waste management are emphasized, which will help employ suitable waste management techniques and technologies to conserve the everlasting freshwater resources on earth.

Health impacts of indoor air pollution from household solid fuel on children and women.

The inefficient and incomplete combustion of solid fuel (SF) is associated with high levels of indoor air pollutants leading to 3.55 million deaths annually. The risk is higher in women and children, due to their higher exposure duration and unique physical properties. The current article aims to provide a critical overview regarding the use of solid fuel, its associated pollutants, their toxicity mechanisms and, most importantly the associated health impacts, especially in women and children. Pollutants associated with SF mostly include polycyclic aromatic hydrocarbons, particulate matter, nitrous oxide, carbon monoxide and sulfur dioxide, and their concentrations are two- to threefold higher in indoor environments. These pollutants can lead to a variety of health risks by inducing different toxicity mechanisms, such as oxidative stress, DNA methylation, and gene activation. Exposed children have an increased prevalence of low birth weight, acute lower respiratory tract infections, anemia and premature mortality. On the other hand, lung cancer, chronic obstructive pulmonary disease and cardiovascular diseases are the major causes of disability and premature death in women. Indoor air pollution resulting from SF combustion is a major public health threat globally. To reduce the risks, it is important to identify future research gaps and implement effective interventions and policies.

Formation of nitrogen functionalities in biochar materials and their role in the mitigation of hazardous emerging organic pollutants from wastewater.

Emerging organic pollutants (EOPs) are serious environmental concerns known for their prominent adverse and hazardous ecological effects, and persistence in nature. Their detrimental impacts have inspired researchers to develop the strategic tools that reduce and overcome the challenges caused by EOPs' rising concentration. As such, biochar becomes as a promising class of biomass-derived functional materials that can be used as low-cost and environmentally-friendly emerging catalysts to remove EOPs. Herein, in-depth synthetic strategies and formation mechanisms of biochar-based nitrogen functionalities during thermochemical conversion are presented. Most prominently, the factors affecting N-surface functionalities in biochar are discussed, emphasizing the most effective N-doping approach, including intrinsic N-doping from biomass feedstock and extrinsic N-doping from exogenous sources. Moreover, biochar-assisted EOPs removal in line with interactions of nitrogen functionalities and contaminants are discussed. The possible reaction mechanisms, i.e., radical and non-radical degradation, physical adsorption, Lewis acid-base interaction, and chemisorption, driven by N-functionalities, are addressed. The unresolved challenges of the potential applications of biochar-mediated functionalities for EOPs removal are emphasized and the outlooks of future research directions are proposed at the end.

Environmental emission, fate and transformation of microplastics in biotic and abiotic compartments: Global status, recent advances and future perspectives.

The intensive use and wide-ranging application of plastic- and plastic-derived products have resulted in alarming levels of plastic pollution in different environmental compartments worldwide. As a result of various biogeochemical mechanisms, this plastic litter is converted into small, ubiquitous and persistent fragments called microplastics (<5 mm), which are of significant and increasing concern to the scientific community. Microplastics have spread across the globe and now exist in virtually all environmental compartments (the soil, atmosphere, and water). Although these compartments are often considered to be independent environments, in reality, they are very closely linked. Ample research has been done on microplastics, but there are still questions and knowledge gaps regarding the emission, occurrence, distribution, detection, environmental fate and transport of MPs in different environmental compartments. The current article is intended to provide a systematic overview of MP emissions, pollution conditions, sampling and analytical approaches, transport, fates and transformation mechanisms in different environmental compartments. It also identifies research gaps and future research directions and perspectives.

Enthralling the impact of engineered nanoparticles on soil microbiome: A concentric approach towards environmental risks and cogitation.

Nanotechnology is an avant-garde field of scientific research that revolutionizes technological advancements in the present world. It is a cutting-edge scientific approach that has undoubtedly a plethora of functions in controlling environmental pollutants for the welfare of the ecosystem. However, their unprecedented utilization and hysterical release led to a huge threat to the soil microbiome. Nanoparticles(NPs) hamper physicochemical properties of soil along with microbial metabolic activities within rhizospheric soils.Here in this review shed light on concentric aspects of NP-biosynthesis, types, toxicity mechanisms, accumulation within the ecosystem. However, the accrual of tiny NPs into the soil system has dramatically influenced rhizospheric activities in terms of soil properties and biogeochemical cycles. We have focussed on mechanistic pathways engrossed by microbes to deal with NPs.Also, we have elaborated the fate and behavior of NPs within soils. Besides, a piece of very scarce information on NPs-toxicity towards environment and rhizosphere communities is available. Therefore, the present review highlights ecological perspectives of nanotechnology and solutions to such implications. We have comprehend certain strategies such as avant-garde engineering methods, sustainable procedures for NP synthesis along with vatious regulatory actions to manage NP within environment. Moreover, we have devised risk management sustainable and novel strategies to utilize it in a rationalized and integrated manner. With this background, we can develop a comprehensive plan about NPs with novel insights to understand the resistance and toxicity mechanisms of NPs towards microbes. Henceforth, the orientation towards these issues would enhance the understanding of researchers for proper recommendation and promotion of nanotechnology in an optimized and sustainable manner.

Nickel in soil and water: Sources, biogeochemistry, and remediation using biochar.

Nickel (Ni) is a potentially toxic element that contaminates soil and water, threatens food and water security, and hinders sustainable development globally. Biochar has emerged as a promising novel material for remediating Ni-contaminated environments. However, the potential for pristine and functionalized biochars to immobilize/adsorb Ni in soil and water, and the mechanisms involved have not been systematically reviewed. Here, we critically review the different dimensions of Ni contamination and remediation in soil and water, including its occurrence and biogeochemical behavior under different environmental conditions and ecotoxicological hazards, and its remediation using biochar. Biochar is effective in immobilizing Ni in soil and water via ion exchange, electrostatic attraction, surface complexation, (co)precipitation, physical adsorption, and reduction due to the biogeochemistry of Ni and the interaction of Ni with surface functional groups and organic/inorganic compounds contained in biochar. The efficiency for Ni removal is consistently greater with functionalized than pristine biochars. Physical (e.g., ball milling) and chemical (e.g., alkali/acidic treatment) activation achieve higher surface area, porosity, and active surface groups on biochar that enhance Ni immobilization. This review highlights possible risks and challenges of biochar application in Ni remediation, suggests future research directions, and discusses implications for environmental agencies and decision-makers.