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While the potential of biochar (BC) to immobilize potentially toxic elements (PTEs) in contaminated soils has been studied and reviewed, no review has focused on the potential use of BC for enhancing the phytoremediation efficacy of PTE-contaminated soils. Consequently, the overarching purpose in this study is to critically review the effects of BC on the mobilization, phytoextraction, phytostabilization, and bioremediation of PTEs in contaminated soils. Potential mechanisms of the interactions between BC and PTEs in soils are also reviewed in detail. We discuss the promises and challenges of various approaches, including potential environmental implications, of BC application to PTE-contaminated soils. The properties of BC (e.g., surface functional groups, mineral content, ionic content, and π-electrons) govern its impact on the (im)mobilization of PTEs, which is complex and highly element-specific. This review demonstrates the contrary effects of BC on PTE mobilization and highlights possible opportunities for using BC as a mobilizing agent for enhancing phytoremediation of PTEs-contaminated soils.

The use of thermal methods has become common in modern geomaterial analysis laboratories. The simultaneous thermal analysis (STA) represents a valid support for the definition of the physical behavior of concerned samples, once subjected to a temperature variation. This chapter discusses the thermal behaviors of key mineralogical phases present in soils, in order to provide the readers with a valuable tool for optimizing the compatibility and applicability of the STA method in judicial forensic test purposes. To this end, the chapter presents literature evidences and case studies, including those from the authors’ own studies, where the STA methods have been successfully used in the judicial forensic field.

Tropical soils are often deeply weathered and vulnerable to degradation having low pH and unfavorable Al/Fe levels, which can constrain crop production. This study aims to examine nitrogen-enriched novel biochar co-composts prepared from rice straw, maize stover, and gram residue in various mixing ratios of the biochar and their feedstock materials for the amelioration of acidic tropical soil. Three pristine biochar and six co-composts were prepared, characterized, and evaluated for improving the chemical and biological quality of the soil against a conventional lime treatment. The pH, cation exchange capacity (CEC), calcium carbonate equivalence (CCE) and nitrogen content of co-composts varied between 7.78–8.86, 25.3–30.5 cmol (p+) kg−1, 25.5–30.5%, and 0.81–1.05%, respectively. The co-compost prepared from gram residue biochar mixed with maize stover at a 1:7 dry-weight ratio showed the highest rise in soil pH and CEC, giving an identical performance with the lime treatment and significantly better effect (p < .05) than the unamended control. Agglomerates of calcite and dolomite in biochar co-composts, and surface functional groups contributed to pH neutralization and increased CEC of the amended soil. The co-composts also significantly (p < .05) increased the dehydrogenase (1.87 µg TPF g−1 soil h−1), β-glucosidase (90 µg PNP g−1 soil h−1), and leucine amino peptidase (3.22 µmol MUC g−1 soil h−1) enzyme activities in the soil, thereby improving the soil’s biological quality. The results of this study are encouraging for small-scale farmers in tropical developing countries to sustainably reutilize crop residues via biochar-based co-composting technology.

Development of polymeric magnetic adsorbents is a promising approach to obtain efficient treatment of contaminated water. However, the synthesis of magnetic composites involving multiple components frequently involves tedious preparation steps. In the present study, a magnetic chitosan-palygorskite (MCP) nanocomposite was prepared through a straight-forward one pot synthesis approach to evaluate its lead (Pb2+) removal capacity from aqueous solution. The nano-architectural and physicochemical properties of the newly-developed MCP composite were described via micro- and nano-morphological analyses, and crystallinity, surface porosity and magnetic susceptibility measurements. The MCP nanocomposite was capable to remove up to 58.5 mg Pb2+ g−1 of MCP from water with a good agreement of experimental data to the Langmuir isotherm model (R2 = 0.98). The Pb2+ adsorption process on MCP was a multistep diffusion-controlled phenomenon evidenced by the well-fitting of kinetic adsorption data to the intra-particle diffusion model (R2 = 0.96). Thermodynamic analysis suggested that the adsorption process at low Pb2+ concentration was controlled by chemisorption, whereas that at high Pb2+ concentration was dominated by physical adsorption. X-ray photoelectron and Fourier transform infrared spectroscopy results suggested that the Pb adsorption on MCP was governed by surface complexation and chemical reduction mechanisms. During regeneration, the MCP retained 82% Pb2+ adsorption capacity following four adsorption–desorption cycles with ease to recover the adsorbent using its strong magnetic property. These findings highlight the enhanced structural properties of the easily-prepared nanocomposite which holds outstanding potential to be used as an inexpensive and green adsorbent for remediating Pb2+ contaminated water. Refereed/Peer-reviewed

Refereed/Peer-reviewed Biochar has been widely used for in situ remediation of sediments in recent years because of its advantages including suitable surface area, pore structure, and abundant surface oxygen-containing functional groups. Nevertheless, leaching of some hazardous components of biochar, e.g., potentially toxic elements (PTEs), polycyclic aromatic hydrocarbons, persistent free radicals, dioxins-like compounds, etc., can pose ecological risks to the water–sediment system. In this review, the applications and associated mechanisms of biochar in the remediation of PTEs- and organic pollutants contaminated sediment systems have been illustrated and critically discussed. Additionally, the potentially hazardous constituents in biochar were summarized and the effects of biomass and production conditions on their bioavailability were reviewed. Furthermore, the effects of biochar addition on water/sediment eutrophication, phytotoxicity, benthic damage, and microbial community changes were discussed. On this basis, the monitoring and assessment measures of the potential risks of biochar were summarized, and the corresponding avoidance strategies for different risks were proposed. This paper aims to provide a baseline reference and guidance implications for the biochar selection, toxicity detection, and evaluation in the field of sediment remediation.

Refereed/Peer-reviewed Veterinary antibiotics (VAs) are emerging contaminants in soils as they may pose high risks to the ecosystem and human health. Identifying VAs accumulation in soils is essential for assessing their potential risks. Therefore, we investigated the distribution of VAs in soils from vegetable fields and evaluated their potential ecological and antimicrobial resistance risks in the Chongqing region of the Three Gorges Reservoir area, China. Results indicated that twenty-six species of VAs, including nine sulfonamides (SAs), seven quinolones (QNs), four tetracyclines (TCs), four macrolides (MLs), and two other species of VAs were detected in soils, with their accumulative levels ranging from 1.4 to 3145.7 μg kg−1. TCs and QNs were the dominant VAs species in soils with high detection frequencies (100% TCs and 80.6% for QNs) and accumulative concentration (up to 1195 μg kg−1 for TCs and up to 485 μg kg−1 for QNs). Risk assessment indices showed that VAs (specifically SAs, TCs, and QNs) in most vegetable soils would pose a medium to high risk to the ecosystem and antimicrobial resistance. Mixture of VAs posed a higher risk to soil organisms, antimicrobial resistance, and plants than to aquatic organisms. Modeling analysis indicated that socioeconomic conditions, farmers’ education levels, agricultural practices, and soil properties were the main factors governing VAs accumulation and environmental risks. Farmers with a high educational level owned large-scale farms and were more willing to use organic fertilizers for vegetable production, which eventually led to high VAs accumulation in vegetable soil. These findings would provide a reference for sustainable agricultural and environmental production under the current scenario of chemical fertilizer substitution by organic products and green agricultural development.

Levels of toxic trace elements (TTE) are increasing in soil systems in the modern era of agricultural mechanization and industrial revolution via anthropogenic activities. TTE-contaminated soil does not only have adverse impacts on soil health but also on plants, higher animals, and humans via food-chain contamination, leading to crop failure and several kinds of human and animal diseases. To maintain soil health for future generations and sustainable crop production, keeping our soil alive and protecting its biological components are of utmost importance. Many technologies have been used in the recent past for the mitigation of soil TTE, but slow remediation processes and expensive remediation methods have raised concerns about their limitations. Some remediation methods may lead to further secondary contamination of the soil. Innovative approaches are needed, and the use of endophytes serves as a potential tool to reclaim TTE-contaminated soil by minimizing their toxic effects and maximizing benefits to crops via improved nutrient cycling. The present chapter highlights the significance of endophytes for soil health restoration in TTE-contaminated soil for optimizing crop growth and productivity.

Refereed/Peer-reviewed The phytoextraction with hyperaccumulator plant species has been found as a novel approach for cleaning up of arsenic (As)-contaminated soils. However, proper management strategy should be developed to enhance the phytoextraction potential of hyperaccumulator and minimize the bioavailability and As contamination to agricultural crops. A greenhouse study was evaluated to assess the effectiveness of phosphatic fertilisers viz. di-ammonium phosphate (DAP) and single superphosphate (SSP) with successive two growing cycles on As removal by Chinese brake fern (Pteris vittata L.) from the contaminated Typic Haplustepts soils of West Bengal, India. Present study evaluated the influence of phytoextraction by the fern (P. vittata) on redistribution of As in different fraction (water soluble, exchangeable, aluminium, iron and calcium bound) in soil as well as total and Olsen's extractable fraction in soil and its subsequent impact on rice crop. Among the five fractions, water soluble fraction and Fe-bound As was found in higher magnitude than the other As bound fractions viz. Al-bound, Ca-bound and exchangeable fraction. This fern was grown in As contaminated soils in successive two growing cycles (four months each), and the total As removal from the soil were measured. The removal values of As varied from 6.4 to 13.5% after the first growing cycle and from 10.6 to 23.9% after the second growing cycle. The phytoextracted soils were reused for rice cultivation to reveal the effect of phytoextraction on As accumulation in rice. In this enhanced process of phytoextraction by P. vittata, the phosphatic fertilizers, DAP was contributed greater than SSP in enhancing the more As uptake by the fern as confirmed by our previous study and followed by a significant decrease in available fraction of As in soil and reduced availability for accumulation in rice. Combining the process of two successive cycles phytoextraction with phosphate (DAP) management strategy leads to reduced bio-available fraction in the soil may serve better for soil with medium levels of As contamination. However, these cycles phytoextraction could be prolong with adjustable soil amendments for high As contaminated soil to attain safe limits of As in the soil and reduced the risk of rice consumption in the arsenic affected areas. Combining the process of two successive cycles phytoextraction with phosphate (DAP) management strategy leads to reduced bio-available fraction in the soil may serve better for soil with medium levels of As contamination. However, these cycles phytoextraction could be prolong with adjustable soil amendments for high As contaminated soil to attain safe limits of As in the soil and reduced the risk of rice consumption in the arsenic affected areas.

Refereed/Peer-reviewed Poly- and perfluoro alkyl substances (PFAS) are a group of man-made, notoriously persistent, and highly toxic contaminants in the environment reported worldwide. Many adsorbents including granular activated carbon, graphene, biochar, zeolites, and clay minerals have been tested for PFAS removal from water, but most of these materials suffer from high cost and/or poor removal performance. Here, we synthesized, characterized, and examined the efficiency of PCN-222(Fe), a new porous metal organic framework (MOF) with high water stability, for adsorptive removal of a frequently occurring PFAS, perfluorooctane sulfonate (PFOS), from water. The adsorption isotherm and kinetic studies revealed high PFOS adsorption capacity of PCN-222 (2257 mg/g), with rapid PFOS removal rate (within 30 min). The structure of PCN-222 was unaffected in water in the pH range of 2–10 but disintegrated and lost its PFOS removal ability at pH > 10. The PFOS adsorption on PCN-222 was an endothermic reaction. Electrostatic attraction was a dominant mechanism for PFOS adsorption at < 1694 mg/g PFOS concentration, while hydrophobic interaction accompanied with hydrogen-bonding was responsible at ≥ 1694 mg/g PFOS concentration. The interlayer morphology of PCN-222 did not change due to increasing PFOS loading. The findings of this study demonstrated superior features of PCN-222 over other conventional adsorbents for its potential application in removing PFOS from contaminated water to reduce PFOS transfer from water to living organisms.

We are racing to manage a phenomenally increasing volume of organic wastes from urban, industrial and agricultural entities. Composting is one of the preferred ways to convert biodegradable wastes into nutrient-rich soil conditioners. The age-old technique of composting process is being improved with innovative scientific means. Biochar, a widely studied soil amendment, is a carbonaceous material that can hold nutrients from endogenic/exogenic sources. Biochar-compost, a biochar-complemented compost, may provide a wide range of benefits expected from both materials. Compost and biochar can improve physicochemical and microbiological attributes of soils by supplying labile and stable carbons, and nutrients. Compost may also supply beneficial microbes. This means biochar-compost is a synergic soil amendment that can improve soil quality, increase crop production, and remediate contaminated soils. Having stable carbon, large reactive surface with nutrient loads, biochar can interact widely with organic biomass and modify physicochemical and-microbial states during a composting process while making biochar-compost. Production and application methods of biochar, compost and biochar-compost are covered for agricultural and contaminated soils. Metal and organic contaminations are also discussed. A case study on making and field-testing a mineral-enhanced biochar and a biochar-compost to improve rice yield, is presented at the end.

Refereed/Peer-reviewed Silicon nanoparticles (SiNPs) have been widely used to immobilize toxic trace metal(loid)s (TTMs) in contaminated croplands. However, the effect and mechanisms of SiNP application on TTM transportation in response to phytolith formation and phytolith-encapsulated-TTM (PhytTTM) production in plants are unclear. This study demonstrates the promotion effect of SiNP amendment on phytolith development and explores the associated mechanisms of TTM encapsulation in wheat phytoliths grown on multi-TTM contaminated soil. The bioconcentration factors between organic tissues and phytoliths of As and Cr (> 1) were significantly higher than those of Cd, Pb, Zn and Cu, and about 10 % and 40 % of the total As and Cr that bioaccumulated in wheat organic tissues were encapsulated into the corresponding phytoliths under high-level SiNP treatment. These observations demonstrate that the potential interaction of plant silica with TTMs is highly variable among elements, with As and Cr being the two most strongly concentrated TTMs in the phytoliths of wheat treated with SiNPs. The qualitative and semi-quantitative analyses of the phytoliths extracted from wheat tissues suggest that the high pore space and surface area (≈ 200 m² g⁻¹) of phytolith particles could have contributed to the embedding of TTMs during silica gel polymerization and concentration to form PhytTTMs. The abundant Sisingle bondO functional groups and high silicate-minerals in phytoliths are dominant chemical mechanisms for the preferential encapsulation of TTMs (i.e., As and Cr) by wheat phytoliths. Notably, the organic carbon and bioavailable Si of soils and the translocation of minerals from soil to plant aerial parts can impact TTM sequestration by phytoliths. Thus, this study has implications for the distribution or detoxification of TTMs in plants via preferential PhytTTM production and biogeochemical cycling of PhytTTMs in contaminated cropland following exogenous Si supplementation.

Refereed/Peer-reviewed Metal halide perovskite solar cells (PSCs) have gained extensive attention in the field of solar photovoltaic technology over the past few years. Despite being a remarkable alternative to fossil fuels, solar cells may have detrimental effects on the environment and human health owing to the use of toxic materials during manufacturing. Although modern metal-halide-based PSCs are stable and have encapsulation to prevent the release of potentially toxic materials into the environment, their destruction due to strong winds, hail, snow, landslides, fires, or waste disposal can result in the exposure of these materials to the environment. This may lead to the contamination of soil and groundwater, and uptake of potentially toxic elements by plants, subsequently affecting humans and other living organisms via food chain contamination. Despite worldwide concern, the environmental and ecotoxicological impacts of metal-halide-based PSCs have not been comprehensively surveyed. This review summarizes and critically evaluates the current status of metal-halide-based PSC production and its impact on environmental sustainability, food security, and human health. Furthermore, safe handling and disposal methods for the waste generated from metal-halide-based PSCs are proposed, with a focus on recycling and reuse. Although some studies have suggested that the amount of lead released from metal halide PSCs is far below the maximum permissible levels in most soils, a clear conclusion cannot be reached until real contamination scenarios are assessed under field conditions. Precautions must be taken to minimize environmental contamination throughout the lifecycle of PSCs until nontoxic and similarly performing alternative solar photovoltaic products are developed.

Biochar, a potential alternative of infield crop residue burning, can prevent nutrient leaching from soil and augment soil fertility. However, pristine biochar contains low cation (CEC) and anion (AEC) exchange capacity. This study developed fourteen engineered biochar by treating a rice straw biochar (RBC-W) first separately with different CEC and AEC enhancing chemicals, and then with their combined treatments to increase CEC and AEC in the novel biochar composites. Following a screening experiment, promising engineered biochar, namely RBC-W treated with O3-HCl-FeCl3 (RBC-O-Cl), H2SO4-HNO3-HCl-FeCl3 (RBC-A-Cl), and NaOH-Fe(NO3)3(RBC-OH-Fe), underwent physicochemical characterization and soil leaching-cum nutrient retention studies. RBC-O-Cl, RBC-A-Cl, and RBC-OH-Fe recorded a spectacular rise in CEC and AEC over RBC-W. All the engineered biochar remarkably reduced the leaching of NH4+-N, NO3- -N, PO43--P and K+ from a sandy loam soil and increased retention of these nutrients. RBC-O-Cl at 4.46 g kg-1 dosage emerged as the most effective soil amendment increasing the retention of above ions by 33.7, 27.8, 15.0, and 5.74 % over a comparable dose of RBC-W. The engineered biochar could thus enhance plants' nutrient use efficiency and reduce the use of costly chemical fertilizers that are harmful to environmental quality. Refereed/Peer-reviewed

Refereed/Peer-reviewed Imogolite belongs to the family of nanotubular metal oxides which are useful for the construction of new materials in nanotechnology. This study aims to develop a simple waste valorization method to obtain imogolite from cement kiln dust (CKD) via solubilization of CKD and subsequent precipitation of imogolite (Imo-CKD) in a hydrothermal process. The newly synthesized Imo-CKD and a conventional imogolite (Imo) showed similar diameter (Ø) and length (L) of nanotubes [Ø≅ 1.9 nm and L ≅ 200 nm] and crystallinity grade but different values of isoelectric point (IEP) [IEPImo−CKD=8.86 and IEPImo=9.92]. The shift in the IEP value of Imo-CKD to a lower value was attributed to the presence of allophane as a subproduct during Imo-CKD synthesis. Arsenite [As(III)] removal from water by both the imogolites was a rapid (t ≤ 20 min) and spontaneous process. The kinetic As(III) removal data obeyed the pseudo-second order model, while surface diffusion also controlled the As(III) adsorption process. The activation energy (Ea > 40 kJ mol−1) suggested a chemical adsorption of As(III) in both materials. The Imo-CKD (0.377 mmol g−1) removed As(III) from water more efficiently than Imo (0.334 mmol g−1), despite the formation of allophane byproduct in the synthesis process. Results of this study can promote the reuse of inexpensive CKD as a viable alternative to replace costly tetraethyl orthosilicate for imogolite synthesis and use of imogolite for water pollutant removal.

Numerous harmful chemicals are introduced every year in the environment through anthropogenic and geological activities raising global concerns of their ecotoxicological effects and decontamination strategies. Biochar technology has been recognized as an important pillar for recycling of biomass, contributing to the carbon capture and bioenergy industries, and remediation of contaminated soil, sediments and water. This paper aims to critically review the application potential of biochar with a special focus on the synergistic and antagonistic effects on contaminant-degrading microorganisms in single and mixed-contaminated systems. Owing to the high specific surface area, porous structure, and compatible surface chemistry, biochar can support the proliferation and activity of contaminant-degrading microorganisms. A combination of biochar and microorganisms to remove a variety of contaminants has gained popularity in recent years alongside traditional chemical and physical remediation technologies. The microbial compatibility of biochar can be improved by optimizing the surface parameters so that toxic pollutant release is minimized, biofilm formation is encouraged, and microbial populations are enhanced. Biocompatible biochar thus shows potential in the bioremediation of organic contaminants by harboring microbial populations, releasing contaminant-degrading enzymes, and protecting beneficial microorganisms from immediate toxicity of surrounding contaminants. This review recommends that biochar-microorganism co-deployment holds a great potential for the removal of contaminants thereby reducing the risk of organic contaminants to human and environmental health Refereed/Peer-reviewed

Refereed/Peer-reviewed Microalgae can add value to biological wastewater treatment processes by capturing carbon and nutrients and producing valuable biomass. Harvesting small cells from liquid media is a challenge easily addressed with biofilm cultivation. Three experimental photobioreactors were constructed from inexpensive materials (e.g. plexiglass, silicone) for hybrid liquid/biofilm cultivation of a microalgal-bacterial consortia in aquaculture effluent. Three light regimes (full-spectrum, blue-white, and red) were implemented to test light spectra as a process control. High-intensity full-spectrum light caused photoinhibition and low biomass yield, but produced the most polyhydroxybutyrate (PHB) (0.14 mg g−1); a renewable bioplastic polymer. Medium-intensity blue-white light was less effective for carbon capture, but removed up to 82 % of phosphorus. Low-intensity red light was the only net carbon-negative regime, but increased phosphorus (+4.98 mg/L) in the culture medium. Light spectra and intensity have potential as easily-implemented process controls for targeted wastewater treatment, biomass production, and PHB synthesis using photosynthetic consortia.

Adsorption behavior of ranitidine hydrochloride (RT) on a Ca-montmorillonite (SAz-1) was studied in aqueous system through batch experiments. The adsorption kinetics revealed that the equilibrium reached within 0.25 h and the data fitted well to the pseudo-second order kinetic equation (R2 = 0.98). The maximum RT adsorption capacity of SAz-1 was 369.2 mg/g and the adsorption isotherm data fol-lowed the Langmuir model (R2 = 0.99). The adsorption of RT and desorption of exchangeable cations from the clay mineral were linearly correlated, suggesting that cation exchange was the dominant mechanism of RT adsorption. The XRD examination of RT-adsorbed SAz-1 samples (unsaturated/saturated) after heat-ing enabled the calculation of RT occupied area in the interlayer of the clay mineral. The results suggested that adsorbed-RT at low loading rate could lay on the internal surfaces in a free style to reduce the basal spacing (d001 value) of SAz-1. When the RT loading rate was increased, a limited surface space enforced more RT molecules to lay in a tilted style and caused interlayer swelling of SAz-1 increasing the d001 value. The trend of rising decomposition temperature of RT with increasing RT loading rates confirmed intercalation of RT molecules in SAz-1. Infrared spectral analysis revealed the participation of amide and furan groups of RT in binding between RT and SAz-1. Thus, this study indicated that SAz-1 is an effi-cient adsorbent to remove RT from contaminated water, and the chain-like molecular structure of RT could cause an irregular change in the basal spacing of swelling type clay minerals. (c) 2022 Elsevier Inc. All rights reserved. Refereed/Peer-reviewed

The fungicide chlorothalonil (CTL) and its metabolite hydroxy chlorothalonil (OH-CTL) constitute a risk of soil and water contamination, highlighting the need to find suitable soil remediation methods for these compounds. Surfactants can promote the bioavailability of organic compounds for enhanced microbial degradation, but the performance depends on soil and surfactant properties, sorption-desorption equilibria of contaminants and surfactants, and possible adverse effects of surfactants on microorganisms. This study investigated the influence of five surfactants [e.g., Triton X-100 (TX-100), sodium dodecyl sulphate (SDS), hexadecyltrimethylammonium bromide (HDTMA), Aerosol 22 and Tween 80] on the sorption-desorption, degradation, and mobility of CTL and OH-CTL in two volcanic and one non-volcanic soil. Sorption and desorption of fungicides depended on the sorption of surfactants on soils, surfactants' capacity to neutralize the net negative charge of soils, surfactants’ critical micellar concentration, and pH of soils. HDTMA was strongly adsorbed on soils, which shifted the fungicide sorption equilibria by increasing the distribution coefficient (Kd) values. Contrarily, SDS and TX-100 lowered CTL and OH-CTL sorption on soils by decreasing the Kd values, which resulted in an efficient extraction of the fungicide compounds from soil. SDS increased the degradation of CTL, especially in the non-volcanic soil (DT50 values were 14 and 7 days in natural and amended soils, with final residues

Refereed/Peer-reviewed High price of chemical potassium (K) fertilizers together with low K use efficiency in weathered tropical soils necessitates the exploration of alternative K fertilizer sources. Effectiveness of low-grade silicate mineral powders (SMP) as a natural K fertilizer in a highly weathered tropical soil was evaluated in this study via laboratory and pot experiments by growing oat (Avena sativa L) and palmarosa (Cymbopogon martini var. motia). Five SMP materials (two mica, one feldspar and two greensand) were obtained from quarry mining sites across India. The total K content in the SMP followed the order: feldspar (12.3%) > waste mica (5.98–8.03%) > greensand (3.77–4.46%). The amount of K released from SMP by chemical extractants was in the following order: water < 0.01 M citric acid < 1 M ammonium acetate < 1 M nitric acid, which indicated that SMP was a slow-release K source. Of the five SMP materials, one waste mica, the feldspar and one greensand were included in the plant growth experiments based on their high K contents. Water and 0.01 M citric acid extractable K from SMP showed the best correlation with K uptake by plants. Compared to feldspar (19.7–22.5%) and greensand (5.4–7.5%), the K recovery from waste mica (39.3–42.5%) was notably higher in both palmarosa and oat. Soil K pool was significantly recharged with waste mica application as evident from higher exchangeable and non–exchangeable K in soil than chemical fertilizer treatment. Application of SMP, particularly waste mica and feldspar, also increased the soil pH and cation exchange capacity by releasing basic cations and improving their retention in the tropical soil. By using low-grade SMP in agriculture, it is thus possible to achieve green recycling of mining wastes as K fertilizer while improving crop production and amending poor quality soils.

Refereed/Peer-reviewed Soil microorganisms and physicochemical properties are considered the two most influencing factors for maintaining plant diversity. However, the operational mechanisms and which factor is the most influential manipulator remain poorly understood. In this study, we examine the collaborative influences of soil physicochemical properties (i.e., soil water, soil organic matter (SOM), salinity, total phosphorus and nitrogen, pH, soil bulk density and fine root biomass) and soil microorganisms (fungi and bacteria) on plant diversity across two types of tree patches dominated by big and small trees (big trees: height ≥ 7 m and DBH ≥ 60 cm; small trees: height ≤ 4.5 m and DBH ≤ 20 cm) in an arid desert region. Tree patch is consists of a single tree or group of trees and their accompanying shrubs and herbs. It was hypothesized that soil physicochemical properties and microorganisms affect plant diversity but their influence differ. The results show that plant and soil microbial diversity increased with increasing distances from big trees. SOM, salinity, fine root biomass, soil water, total phosphorus and total nitrogen contents decreased with increasing distance from big trees, while pH and soil bulk density did not change. Plant and soil microbial diversity were higher in areas close to big trees compared with small trees, whereas soil physicochemical properties were opposite. The average contribution of soil physicochemical properties (12.2%–13.5%) to plant diversity was higher than microbial diversity (4.8%– 6.7%). Salinity had the largest negative affect on plant diversity (24.7%–27.4%). This study suggests that soil fungi constrain plant diversity while bacteria improve it in tree patches. Soil physicochemical properties are the most important factor modulating plant diversity in arid desert tree patches.

usc Microplastics have become a global concern, and soil acts as a major sink for plastic pollution. Due to rapid development of soil microplastics research, various analysis methods have been developed, but require proper consistency and standard procedures. The objective of this study was to appraise a quality assessment concerning soil microplastics from a methodological perspective. Nine studies were selected for the quality assessment exercise based on methodological investigations on soil microplastics and were evaluated based on the adapted Criteria for Reporting and Evaluating Ecotoxicity Data (CRED) method. The highest score obtained by an individual study was 21 while the lowest was 14, leaving a wide score gap which indicated inconsistency amongst the studies. Criterion with the highest average score of 2.0 was obtained for sample size and data reporting. The lowest average score of 0.89 was for the negative control. In conclusion, the total average scores for all eleven criteria were 1.56. Current quality assessment perceived that there was room for improvement and betterment of quality assurance for studies on microplastics and a form of guideline on methodological aspects of soil microplastics studies. It was suggested that future microplastics studies should methodically include quality assurance/quality control (QA/QC) protocols in every process to ensure that good quality data is produced and applied in the risk assessment process. Refereed/Peer-reviewed

Refereed/Peer-reviewed Humic substances with or without chemical modification can serve as environmentally benign and inexpensive adsorbents of potentially toxic trace elements (PTTEs) in the environment. The present study investigated the absorption of Pb, Zn, Cu and Ni by natural and potassium persulfate (K2S2O8) modified humic acids (HAs) isolated from a lowland peat through batch experiments. The adsorption of the studied PTTEs on the natural HA was satisfactorily described by the Langmuir isotherm model with maximum monolayer adsorption capacities of 318.2, 286.5, 225.0 and 136.8 mmol/kg for Pb, Cu, Zn and Ni, respectively. A thorough characterization of the natural and modified HA using 13C nuclear magnetic resonance spectroscopy demonstrated that the chemical modification of natural HA with K2S2O8 led to an increase in the content of carboxyl groups, and ketone and quinoid fragments in the HA structure. Consequently, the modified HA absorbed 16.3, 14.2, 10.6 and 6.9% more Pb, Ni, Zn and Cu, respectively, than the original natural HA. The isotherm data modeling together with adsorbent characterization suggested that the adsorption of PTTEs was controlled mainly by chemisorption mechanisms where inner-sphere complexations of metal ions with HA functional groups took place.

Results from earlier laboratory and field experiments were interrogated for the possibilities of sequestration, or long term accumulation, of carbon from excess greenhouse gases in the atmosphere. In the laboratory study, samples of three (top)soils dominated by kaolinite and illite (together), smectite, and allophane were examined for the adsorption and desorption of dissolved organic carbon (DOC). Adsorption and desorption of DOC were carried out on clay fractions extracted physically and after first native organic matter and then iron oxides were removed chemically. Labeled organic material was added to the soils to assess the priming effect of organic carbon (OC). In the field, changes in OC were measured in sandy soils that had been amended by additions of clay for between 3 and 17 years, both through incorporation of exogenous clay and delving of in situ clay. The laboratory experiments demonstrated that a portion of DOC was held strongly in all soils. The amount of DOC adsorbed depended on clay mineral types, including Fe oxides. Much adsorbed DOC was lost by desorption in water and a substantial amount of native OC was lost on priming with new OC. Addition of clay to soils led to increased OC. Therefore, addition of clay to soil may enhance net sequestration of C. Organic carbon close to mineral surfaces or within micro aggregates is held most strongly. Carbon sequestration may occur in subsoils with unsaturated mineral surfaces. However, incorporation of carbon into macroaggregates from enhanced plant growth might be most effective in removing excess carbon from the atmosphere, albeit over the short-term. Refereed/Peer-reviewed

Abstract There has been more than 75% rise in the number of extreme weather events such as drought and flood during 2000–2019 compared to 1980–1999 due to the adverse effects of climate change, causing significant deterioration of the soil and water quality. Simultaneously, the growing human population has been exerting pressure on available water and soil resources due to overuse or unplanned use. While greenhouse gas emissions have intensified, the fertility of agricultural soils has declined globally due to the exposure of soils to frequent flooding, desertification, and salinization (resulting from extreme weather events). The current review aims to give an overview of damages caused to the soil–plant system by extreme weather events and provide a perspective on how biochar can repair the damaged system. Biochar is known to improve soil fertility, increase crop productivity and mitigate greenhouse gas emissions via sustainable recycling of bio-waste. Beneficial properties of biochar such as alkaline pH, high cation exchange capacity, abundant surface functional groups, remarkable surface area, adequate porosity, excellent water holding capacity, and sufficient nutrient retention capacity can help repair the adverse effects of extreme weather events in the soil–plant system. This paper recommends some cautious future approaches that can propel biochar’s use in improving the soil–plant systems and promoting sustainable functioning of extreme weather-affected areas via mitigation of the adverse effects. Graphical Abstract

Nanoplastics are drawing a significant attention as a result of their propensity to spread across the environment and pose a threat to all organisms. The presence of nanoplastics in water is given attention nowadays as the transit of nanoplastics occurs through the aquatic ecosphere besides terrestrial mobility. The principal removal procedures for macro-and micro-plastic particles are effective, but nanoparticles escape from the treatment, increasing in the water and significantly influencing the society. This critical review is aimed to bestow the removal technologies of nanoplastics from aquatic ecosystems, with a focus on the treatment of freshwater, drinking water, and wastewater, as well as the importance of transit and its impact on health concerns. Still, there exists a gap in providing a collective knowledge on the methods available for nanoplastics removal. Hence, this review offered various nanoplastic removal technologies (microorganism-based degradation, membrane separation with a reactor, and photocatalysis) that could be the practical/effective measures along with the traditional procedures (filtration, coagulation, centrifugation, flocculation, and gravity settling). From the analyses of different treatment systems, the effectiveness of nanoplastics removal depends on various factors, source, size, and type of nanoplastics apart from the treatment method adopted. Combined removal methods, filtration with coagulation offer great scope for the removal of nanoplastics from drinking water with >99 % efficiency. The collected data could serve as base-line information for future research and development in water nanoplastics cleanup. Refereed/Peer-reviewed

Purpose: Similar to fresh- and brackish water aquaculture ponds, commercial shrimp farming in degraded saline areas holds the potential to bury carbon (C) in the sediments. However, studies on the mechanisms of sediment C dynamics and C-flux in response to inland saline aquaculture management practices are still scarce. Therefore, the objectives of the present study are to quantify the C burial rate in inland saline aquaculture ponds and assess the impact of inland saline aquaculture on sensitive C fractions in the bottom sediment of the ponds. Materials and methods: The sediment samples (n = 12 from each pond) were collected from six shrimp farming ponds (1000 m2 area of each pond) of different ages. The sediment depth, sediment accumulation rate and the levels of total carbon (TC), total organic carbon (TOC) and sediment oxidizable organic carbon (SOC) and its different fractions were determined using standard procedures. The data were analysed by one-way analysis of variance (ANOVA), followed by the Duncan's multiple range test for comparing the means, and the Pearson correlation test was used to assess the relationship between the different pond sediment parameters and SOC content. Results and discussion: The results revealed that the annual C accumulation rates varied from 902 to 1346 kg C ha−1 year−1 in 7-year-old earthen ponds (EPs) and bottom cemented ponds (BCPs), respectively. The sediment C fractions, including TC, TOC, SOC and its fractions (very labile, VLc; labile, Lc; less labile, LLc), and non-labile carbon (NLc)) were progressively increased over the pond age. The inland saline aquaculture practices over the years increased both active (AC) and passive carbon (PC) pools in the pond sediments, helped in the restoration and improvement of sediment quality and enhanced C sequestration potential of the sediments. Furthermore, a significant increase in the level of particulate organic carbon (POC) in BCPs justified that the non-ploughing practices at BCPs facilitated the formation of macro- and micro-aggregates, thereby increasing the C retention and stability of the pond sediments. Conclusion: This study suggested that the shrimp farming ponds in semi-arid saline soils represented considerable C burial hotspots, enhanced the stable passive C pools and improved the sediment quality. Refereed/Peer-reviewed

usc This study aims to understand how properties of modified aluminosilicate geomaterials influence the antibacterial performance of nanocomposites when prepared with bimetallic nanoparticles (NPs). Copper/silver (Cu/Ag) bimetallic NPs were synthesized in the presence of imogolite (Imo), montmorillonite (Mtt), or zeolite (Zeo) using a simple one-pot method and characterized for their crystal phases, micro- and nanomorphologies, particle size, elemental composition, and electrophoretic mobility. The antibacterial activity was evaluated through minimum inhibition concentration assays of NPs and nanocomposites for Gram (−) Escherichia coli and Gram (+) Staphylococcus aureus bacteria. Deposition of metallic Cu0, Ag0, and cuprite NPs was confirmed in Zeo_Cu/Ag and Imo_Cu/Ag nanocomposites, whereas only Cu0 and Ag0 were identified in Mtt_Cu/Ag. The bimetallic NPs were more uniformly distributed on Zeo and Mtt than Imo. Particle sizes of 28.1 ± 5.0, 9.4 ± 2.3, 10.1 ± 1.7, and 12 ± 1.3 nm were determined for Cu/Ag NPs, Imo_Cu/Ag, Mtt_Cu/Ag, and Zeo_Cu/Ag, respectively. The release rate of Cu and Ag ions from Zeo_Cu/Ag was higher than those of pristine Cu/Ag NPs and the other two nanocomposites. The antimicrobial action of bimetallic NPs and nanocomposites was dose-dependent in relation to the concentration of concerned materials and their stability in the medium. The physicochemical characteristics of Zeo resulted in a homogeneous distribution and low oxidation and agglomeration of Cu/Ag NPs, consequently increasing the antibacterial activity. Results of this study highlight the benefits of using a geomaterial support to achieve high antibacterial activity of bimetallic NPs, which could help reduce the consumption of pure Cu/Ag salts in NP-based antibacterial applications. Refereed/Peer-reviewed

Antimony (Sb) is introduced into soils, sediments, and aquatic environments from various sources such as weathering of sulfide ores, leaching of mining wastes, and anthropogenic activities. High Sb concentrations are toxic to ecosystems and potentially to public health via the accumulation in food chain. Although Sb is poisonous and carcinogenic to humans, the exact mechanisms causing toxicity still remain unclear. Most studies concerning the remediation of soils and aquatic environments contaminated with Sb have evaluated various amendments that reduce Sb bioavailability and toxicity. However, there is no comprehensive review on the biogeochemistry and transformation of Sb related to its remediation. Therefore, the present review summarizes: (1) the sources of Sb and its geochemical distribution and speciation in soils and aquatic environments, (2) the biogeochemical processes that govern Sb mobilization, bioavailability, toxicity in soils and aquatic environments, and possible threats to human and ecosystem health, and (3) the approaches used to remediate Sb-contaminated soils and water and mitigate potential environmental and health risks. Knowledge gaps and future research needs also are discussed. The review presents up-to-date knowledge about the fate of Sb in soils and aquatic environments and contributes to an important insight into the environmental hazards of Sb. The findings from the review should help to develop innovative and appropriate technologies for controlling Sb bioavailability and toxicity and sustainably managing Sb-polluted soils and water, subsequently minimizing its environmental and human health risks. Refereed/Peer-reviewed

usc The accumulation of microplastics (MPs) and nanoplastics (NPs) in terrestrial and aquatic ecosystems has raised concerns because of their adverse effects on ecosystem functions and human health. Plastic waste management has become a universal problem in recent years. Hence, sustainable plastic waste management techniques are vital for achieving the United Nations Sustainable Development Goals. Although many reviews have focused on the occurrence and impact of micro- and nanoplastics (MNPs), there has been limited focus on the management of MNPs. This review first summarizes the ecotoxicological impacts of plastic waste sources and issues related to the sustainable management of MNPs in the environment. This paper then critically evaluates possible approaches for incorporating plastics into the circular economy in order to cope with the problem of plastics. Pollution associated with MNPs can be tackled through source reduction, incorporation of plastics into the circular economy, and suitable waste management. Appropriate infrastructure development, waste valorization, and economically sound plastic waste management techniques and viable alternatives are essential for reducing MNPs in the environment. Policymakers must pay more attention to this critical issue and implement appropriate environmental regulations to achieve environmental sustainability. Refereed/Peer-reviewed

Biochar is produced as a charred material with high surface area and abundant functional groups by pyrolysis, which refers to the process of thermochemical decomposition of organic material at elevated temperatures in the absence of oxygen. The carbon component in biochar is relatively stable, and, hence, biochar was originally proposed as a soil amendment to store carbon in the soil. Biochar has multifunctional values that include the use of it for the following purposes: soil amendment to improve soil health, nutrient and microbial carrier, immobilising agent for remediation of toxic metals and organic contaminants in soil and water, catalyst for industrial applications, porous material for mitigating greenhouse gas emissions and odorous compounds, and feed supplement to improve animal health and nutrient intake efficiency and, thus, productivity. This article provides for the first time an overview of the multifunctional values and unintended consequences of biochar applications. Refereed/Peer-reviewed

Fast weathering of parent materials and rapid mineralization of organic matter because of prevalent climatic conditions, and subsequent development of acidity and loss/exhaustion of nutrient elements due to intensive agricultural practices have resulted in the degradation of soil fertility and productivity in the vast tropical areas of the world. There is an urgent need for rejuvenation of weathered tropical soils to improve crop productivity and sustainability. For this purpose, biochar has been found to be more effective than other organic soil amendments due to biochar's stability in soil, and thus can extend the benefits over long duration. This review synthesizes information concerning the present status of biochar application in highly weathered tropical soils highlighting promising application strategies for improving resource use efficiency in terms of economic feasibility. In this respect, biochar has been found to improve crop productivity and soil quality consistently through liming and fertilization effects in low pH and infertile soils under low-input conditions typical of weathered tropical soils. This paper identifies several advance strategies that can maximize the effectiveness of biochar application in weathered tropical soils. However, strategies for the reduction of costs of biochar production and application to increase the material's use efficiency need future development. At the same time, policy decision by linking economic benefits with social and environmental issues is necessary for successful implementation of biochar technology in weathered tropical soils. This review recommends that advanced biochar strategies hold potential for sustaining soil quality and agricultural productivity in tropical soils. Refereed/Peer-reviewed

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 Cdouble bondO 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. Refereed/Peer-reviewed

The accumulation of plastics in the soil ecosystem poses an increasing environmental concern worldwide. However, little is known about the effect of plastic concentrations on soil properties and soil biota. In this study, we investigated the effect of low-density polyethylene (LDPE) microplastics (MPs) on the chemical and microbial properties of agricultural soil using a set of microcosm experiments. The soil was incubated for 100 days with LDPE at concentrations of 0%, 0.1%, 1%, 3%, 5%, and 7% at 25°C with 70% water-holding capacity. Along with soil chemical analysis, we conducted an analysis of soil microbial properties on the first day and again after 100 days of incubation. LDPE concentrations of ≥1% significantly (p