Properties of biochar-amended soils and their sorption of imidacloprid, isoproturon, and atrazine

Agricultural biomass/waste-based materials could be a potential adsorption-type remediation contributor to environmental pollution induced by pesticides-A critical review

The widespread use of pesticides that are inevitable to keep the production of food grains brings serious environmental pollution problems. Turning agricultural biomass/wastes into materials addressing the issues of pesticide contaminants is a feasible strategy to realize the reuse of wastes. Several works summarized the current applications of agricultural biomass/waste materials in the remediation of environmental pollutants. However, few studies systematically take the pesticides as an unitary target pollutant. This critical review comprehensively described the remediation effects of crop-derived waste (cereal crops, cash crops) and animal-derived waste materials on pesticide pollution. Adsorption is considered a superior and highlighted effect between pesticides and materials. The review generalized the sources, preparation, characterization, condition optimization, removal efficiency and influencing factors analysis of agricultural biomass/waste materials. Our work mainly emphasized the promising results in lab experiments, which helps to clarify the current application status of these materials in the field of pesticide remediation. In the meantime, rigorous pros and cons of the materials guide to understand the research trends more comprehensively. Overall, we hope to achieve a large-scale use of agricultural biomass/wastes.

Those That Remain Caught in the "Organic Matter Trap": Sorption/Desorption Study for Levelling the Fate of Selected Neonicotinoids

With projections suggesting an increase in the global use of neonicotinoids, contemporary farmers can get caught on the "pesticide treadmill", thus creating ecosystem side effects. The aim of this study was to investigate the sorption/desorption behavior of acetamiprid, imidacloprid, and thiacloprid that controls their availability to other fate-determining processes and thus could be useful in leveling the risk these insecticides or their structural analogues pose to the environment, animals, and human health. Sorption/desorption isotherms in four soils with different organic matter (OC) content were modelled by nonlinear equilibrium models: Freundlich's, Langmuir's, and Temkin's. Sorption/desorption parameters obtained by Freundlich's model were correlated to soil physico-chemical characteristics. Even though the OC content had the dominant role in the sorption of the three insecticides, the role of its nature as well as the chemical structure of neonicotinoids cannot be discarded. Insecticides sorbed in the glassy OC phase will be poorly available unlike those in the rubbery regions. Imidacloprid will fill the sorption sites equally in the rubbery and glassy phases irrespective of its concentration. The sorption of thiacloprid at low concentrations and acetamiprid at high concentrations is controlled by hydrophilic aromatic structures, "trapping" the insecticides in the pores of the glassy phase of OC.

Remediation of neonicotinoid-contaminated soils using peanut shell biochar and composted chicken manure: Transformation mechanisms of geochemical fractions

Soil remediation techniques are promising approaches to relieve the adverse environmental impacts in soils caused by neonicotinoids application. This study systematically investigated the remediation mechanisms for peanut shell biochar (PSB) and composted chicken manure (CCM) on neonicotinoid-contaminated soils from the perspective of transformation of geochemical fractions by combining a 3-step sequential extraction procedure and non-steady state model. The neonicotinoid geochemical fractions were divided into labile, moderate-adsorbed, stable-adsorbed, bound, and degradable fractions. The PSB and CCM addition stimulated the neonicotinoid transformation in soils from labile fraction to moderate-adsorbed and stable-adsorbed fractions. Compared with unamended soils, the labile fractions decreased from 47.6% ± 11.8% of the initial concentrations to 12.1 ± 9.3% in PSB-amended soils, and 7.1 ± 4.9% in PSB and CCM-amended soils, while the proportions of moderate-adsorbed and stable-adsorbed fractions correspondingly increased by 1.8-2.4 times and 2.3-4.8 times, respectively. A small proportion (<4.8%) in bound fractions suggested there were rather limited bound-residues after 48 days incubation. The PSB stimulated the -NO2-containing neonicotinoid-degraders, which promoted the degradable fractions of corresponding neonicotinoids by 8.2 ± 6.3%. Degradable fraction of neonicotinoids was the dominant fate in soils, which accounted for 58.3 ± 16.7%. The findings made beneficial theoretical supplements and provided valuable empirical evidence for the remediation of neonicotinoid-contaminated soils.

Unlocking the potential of biochar in the remediation of soils contaminated with heavy metals for sustainable agriculture

Agricultural soils contaminated with heavy metals (HMs) impose a threat to the environmental and to human health. Amendment with biochar could be an eco-friendly and cost-effective option to decrease HMs in contaminated soil. This paper reviews the application of biochar as a soil amendment to immobilise HMs in contaminated soil. We discuss the technologies of its preparation, their specific properties, and effect on the bioavailability of HMs. Biochar stabilises HMs in contaminated soil, enhance the overall quality of the contaminated soil, and significantly reduce HM uptake by plants, making it an option in soil remediation for HM contamination. Biochar enhances the physical (e.g. bulk density, soil structure, water holding capacity), chemical (e.g. cation exchange capacity, pH, nutrient availability, ion exchange, complexes), and biological properties (e.g. microbial abundance, enzymatic activities) of contaminated soil. Biochar also enhances soil fertility, improves plant growth, and reduces the plant availability of HMs. Various field studies have shown that biochar application reduces the bioavailability of HMs from contaminated soil while increasing crop yield. The review highlights the positive effects of biochar by reducing HM bioavailability in contaminated soils. Future work is recommended to ensure that biochars offer a safe and sustainable solution to remediate soils contaminated with HMs.

Biomass based biochar production approaches and its applications in wastewater treatment, machine learning and microbial sensors

Biochar is a stable carbonaceous material derived from various biomass and can be utilized as adsorbents, catalysts and precursors in various environmental applications. This review discusses various feedstock materials and methods of biochar production via traditional as well as modern approaches. Additionally, the biochar characteristics, HTC process, and its modification by employing steam and gas purging, acidic, basic / alkaline and organo-solvent, electro- and magnetic fields have been discussed. The recent biochar applications for real water, wastewater and industrial wastewater for the abstraction of environmental contaminants also reviewed. Moreover, applications in machine learning and microbial sensors were discussed. In the meantime, analyses on commercial and environmental profit, current ecological concerns and the future directions of biochar application have been well presented.

Comprehensive review on lignocellulosic biomass derived biochar production, characterization, utilization and applications

Biochar is an ample source of organic carbon prepared by the thermal breakdown of biomass. Lignocellulosic biomass is a promising precursor for biochar production, and has several applications in various industries. In addition, biochar can be applied for environmental revitalization by reducing the negative impacts through intrinsic mechanisms. In addition to its environmentally friendly nature, biochar has several recyclable and inexpensive benefits. Nourishing and detoxification of the environment can be undertaken using biochar by different investigators on account of its excellent contaminant removal capacity. Studies have shown that biochar can be improved by activation to remove toxic pollutants. In general, biochar is produced by closed-loop systems; however, decentralized methods have been proven to be more efficient for increasing resource efficiency in view of circular bio-economy and lignocellulosic waste management. In the last decade, several studies have been conducted to reveal the unexplored potential and to understand the knowledge gaps in different biochar-based applications. However, there is still a crucial need for research to acquire sufficient data regarding biochar modification and management, the utilization of lignocellulosic biomass, and achieving a sustainable paradigm. The present review has been articulated to provide a summary of information on different aspects of biochar, such as production, characterization, modification for improvisation, issues, and remediation have been addressed.

Effect of fertilization on the degradation and enantioselectivity of fipronil in soil

BACKGROUND

Fertilizers and pesticides are commonly used simultaneously in agriculture. However, the effects of common fertilizers on the dissipation, enantioselectivity, and metabolites of the chiral insecticide fipronil in soil are yet to be reported.

RESULT

An enantioselective method for detecting fipronil enantiomers and their metabolites in different soil matrices was developed using ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The results showed that organic and compound fertilizers significantly decreased the degradation of S- and R-fipronil, whereas phosphate and microbial fertilizers slightly reduced fipronil dissipation. The half-life values for S- and R-fipronil were 43.3 and 28.9 days, 99.0 and 63.0 days, 69.3 and 43.3 days, 46.2 and 30.1 days, and 43.3 and 31.5 days, respectively, in the control and the four fertilizer treatments, respectively. The enantioselectivity of fipronil enantiomers occurred and R-fipronil exhibited preferential degradation with an enantiomeric fraction (EF) of 0.4900-0.6238 in all treatments; but the four tested fertilizers decreased enantioselectivity with EF values changed from 0.4970 to 0.6238 in the control to 0.4900-0.6171 in fertilizer treatments. Two metabolites, fipronil sulfone and sulfide, were produced, and their amounts increased with culture time in all treatments. Fertilization reduced the content of fipronil sulfide and sulfone but hardly reduced the total amount of fipronil and its metabolites.

CONCLUSION

Fertilizers affect the environmental behavior of fipronil in the soil. Fertilization alters the soil bacterial community, which may be an important factor. This influence is relatively complicated and should be comprehensively considered in the environmental risk assessment of pesticides. © 2023 Society of Chemical Industry.

Effects of alkaline biochar on nitrogen transformation with fertilizer in agricultural soil

The loss and negative impacts of nitrogen from fertilized soils remain a global challenge in agricultural field. Ammonium nitrogen (NH4+-N) and nitrate nitrogen (NO3--N) leaching, together with volatile ammonia loss are the main pathways of nitrogen loss. To improve nitrogen availability, alkaline biochar with improved adsorption capacities is a promising soil amendment. This study was objected to investigate the effects of alkaline biochar (ABC, pH 8.68) on nitrogen mitigation, the effects on nitrogen loss, and the interactions among the mixed soils (biochar, nitrogen fertilizer, and soil) under both pot and field experiments. From pot experiments, ABC addition resulted in the poor reservation of NH4+-N which converted to volatile NH3 under higher alkaline environments, mainly occurring in the first 3 days. But after, NO3--N could be largely retained in surface soil by ABC addition. The reservation of NO3--N by ABC offsets the loss of volatile NH3, and ABC ultimately showed positive reservations of nitrogen with fertilization. In the field experiment, the addition of urea inhibitor (UI) addition could inhibit the volatile NH3 loss caused by ABC mainly in the first week. The long-term operation demonstrated that ABC supported persistent effectiveness in reducing N loss, while UI treatment temporarily delayed the N loss through inhibition of fertilizer hydrolysis. Therefore, the addition of both ABC and UI contributed to reserve soil N in layers (0-50 cm) suitable for crop growth thus improving crops growth.

Remediation technologies for neonicotinoids in contaminated environments: Current state and future prospects

Neonicotinoids (NEOs) are synthetic insecticides with broad-spectrum insecticidal activity and outstanding efficacy. However, their extensive use and persistence in the environment have resulted in the accumulation and biomagnification of NEOs, posing significant risks to non-target organisms and humans. This review provides a summary of research history, advancements, and highlighted topics in NEOs remediation technologies and mechanisms. Various remediation approaches have been developed, including physiochemical, microbial, and phytoremediation, with microbial and physicochemical remediation being the most extensively studied. Recent advances in physiochemical remediation have led to the development of innovative adsorbents, photocatalysts, and optimized treatment processes. High-efficiency degrading strains with well-characterized metabolic pathways have been successfully isolated and cultured for microbial remediation, while many plant species have shown great potential for phytoremediation. However, significant challenges and gaps remain in this field. Future research should prioritize isolating, domesticating or engineering high efficiency, broad-spectrum microbial strains for NEO degradation, as well as developing synergistic remediation techniques to enhance removal efficiency on multiple NEOs with varying concentrations in different environmental media. Furthermore, a shift from pipe-end treatment to pollution prevention strategies is needed, including the development of green and economically efficient alternatives such as biological insecticides. Integrated remediation technologies and case-specific strategies that can be applied to practical remediation projects need to be developed, along with clarifying NEO degradation mechanisms to improve remediation efficiency. The successful implementation of these strategies will help reduce the negative impact of NEOs on the environment and human health.

Efficient removal of Tris(2-chloroethyl) phosphate by biochar derived from shrimp shell: Adsorption performance and mechanism study

Tris(2-chloroethyl) phosphate (TCEP) has been detected all over the world as a typical refractory organic phosphate, especially in groundwater. This work applied a calcium-rich biochar derived from shrimp shell as a low-cost adsorbent for TCEP removal. Based on the kinetics and isotherm studies, the adsorption of TCEP on biochar was monolayer adsorbed on a uniform surface, with SS1000 (the biochar was prepared at the carbonization temperature of 1000 °C) achieving the maximum adsorption capacity of 264.11 mg·g^-1. The prepared biochar demonstrated stable TCEP removal ability throughout a wide pH range, in the presence of co-existing anions, and in diverse water bodies. A rapid removal rate of TCEP was observed during the adsorption process. When the dosage of SS1000 was 0.2 g·L^-1, 95% of TCEP could be removed within the first 30 min. The mechanism analysis indicated that the calcium species and basic functional groups on the SS1000 surface were highly involved in the TCEP adsorption process.

Biochar application for remediation of organic toxic pollutants in contaminated soils; An update

Bioremediation of organic contaminants has become a major environmental concern in the last few years, due to its bio-resistance and potential to accumulate in the environment. The use of diverse technologies, involving chemical and physical principles, and passive uptake utilizing sorption using ecofriendly substrates have drawn a lot of interest. Biochar has got attention mainly due to its simplicity of manufacturing, treatment, and disposal, as it is a less expensive and more efficient material, and has a lot of potential for the remediation of organic contaminants. This review highlighted the adverse impact of persistent organic pollutants on the environment and soil biota. The utilization of biochar to remediate soil and contaminated compounds i.e., pesticides, polycyclic aromatic hydrocarbons, antibiotics, and organic dyes has also been discussed. The soil application of biochar has a significant impact on the biodegradation, leaching, and sorption/desorption of organic contaminants. The sorption/desorption of organic contaminants is influenced by chemical composition and structure, porosity, surface area, pH, and elemental ratios, and surface functional groups of biochar. All the above biochar characteristics depend on the type of feedstock and pyrolysis conditions. However, the concentration and nature of organic pollutants significantly alters the sorption capability of biochar. Therefore, the physicochemical properties of biochar and soils/wastewater, and the nature of organic contaminants, should be evaluated before biochar application to soil and wastewater. Future initiatives, however, are needed to develop biochars with better adsorption capacity, and long-term sustainability for use in the xenobiotic/organic contaminant remediation strategy.

Effect of H3PO4-modified biochar on the fate of atrazine and remediation of bacterial community in atrazine-contaminated soil

The application of chemically modified biochar is a promising strategy for the remediation of contaminated (e.g., pesticides) soil. In this study, H₃PO₄ was used to modify peanut shell to improve the remediation performance of biochar. Surface area (980.19 m²/g), pore volume (0.12 cm³/g), and the functional groups (OH, CO, and phosphorus-containing groups) on the biochar were increased by H₃PO₄ treatment. The sorption experimental data were well fitted by Freundlich model, while the sorption affinity (K_f) of H₃PO₄ modified biochar (PBC) for atrazine was 128 times greater than that of the untreated biochar (BC) in the aquatic systems. The K_f values of PBC-amended soil to atrazine were increased by 13.57 times than that of single soil. The strong sorption of PBC on atrazine delayed the degradation of atrazine in soil, and the residual percentage of atrazine in soil and soil-PBC mixture were 4.90% and 71.44% at the end of 60-day incubation, with the degradation half-life increased from 13.3 to 121.6 d. The analysis of high-throughput sequencing results showed that atrazine reduced the diversity of soil microbial community, but the abundance of microorganisms with degradation function increased and became dominant species. The addition of PBC in soil accelerated the microbial remediation of atrazine stress, which may promote the soil nitrogen cycle. Therefore, amendment of atrazine contaminated soil with PBC can reduce the environmental risk of atrazine and benefit the soil microbial ecology.

Biochar changed the distribution of imidacloprid in a plant-soil-groundwater system

The use of biochar has increased, as its physicochemical properties reduce the adverse effects of pesticides. However, few studies have comprehensively investigated the effects of biochar on the distribution of pesticides in a plant-soil-groundwater system. In this study, a biochar produced from rice straw at 550 °C was chosen, and column experiments with five rated of biochar application (application rates = 0.0, 1.0, 2.0, 3.0, and 4.0% w/w for B0-B4, respectively) were conducted to investigate the capacity of biochar to immobilize imidacloprid (IMI) in soil, thereby decreasing its uptake by plants and leaching from soil into groundwater. Our results showed that IMI in plants, leached from soil, and detected in soil accounted for 3.78, 1.76, and 36.4% of the total IMI input, respectively, and the biochar treatments dramatically decreased the IMI distribution to 0.57, 0.11, and 13.4%, respectively. By contrast, the percentage of undetected IMI increased from 58.1% in the B0 treatment to an average of 86.0% in the biochar treatments. Biochar treatments increased IMI immobilization in soil, which could be related to the increased soil carbon content, surface area, cation exchange capacity. This study indicates that biochar with characters of high surface area and porosity can stabilize IMI and reduce its potential to harm plants and groundwater.

Toxicological effects, environmental behaviors and remediation technologies of herbicide atrazine in soil and sediment: A comprehensive review

Atrazine has become one of the most popular applied triazine herbicides in the world due to its high herbicidal efficiency and low price. With its large-dosage and long-term use on a global scale, atrazine can cause widespread and persistent contamination of soil and sediment. This review systematically evaluates the toxicological effects, environmental risks, environmental behaviors (adsorption, transport and transformation, and bioaccumulation) of atrazine, and the remediation technologies of atrazine-contaminated soil and sediment. For the adsorption behavior of atrazine on soil and sediment, the organic matter content plays an extremely important role in the adsorption process. Various models and equations such as the multi-media fugacity model and solute transport model are used to analyze the migration and transformation process of atrazine in soil and sediment. It is worth noting that certain transformation products of atrazine in the environment even have stronger toxicity and mobility than its parent. Among various remediation technologies, the combination of microbial remediation and phytoremediation for atrazine-contaminated soil and sediment has wide application prospects. Although other remediation technologies such as advanced oxidation processes (AOPs) can also efficiently remove atrazine from soil, some potential problems still need to be further clarified. Finally, some related challenges and prospects are proposed.

Acetamiprid fate in a sandy loam with contrasting soil organic matter contents: A comparison of the degradation, sorption and leaching of commercial neonicotinoid formulations

The impacts of neonicotinoids have generally focussed on the responses of the pure active ingredient. Using a selection of two commercial formulations and the active ingredient, we ran three laboratory studies using ¹⁴C-labelled acetamiprid to study the leaching, sorption and mineralisation behaviours of the commercially available neonicotinoid formulations compared to the pure active ingredient. We added ¹⁴C-spiked acetamiprid to a sandy loam soil that had received long-term additions of farmyard manure at two rates (10 t/ha/yr and 25 t/ha/yr) and mineral fertilisers, as a control. We found significant differences in acetamiprid mineralisation across both the SOM and chemical treatments. Sorption was primarily impacted by changes in SOM and any differences in leachate recovery were much less significant across both treatment types. The mineralisation of all pesticide formulations was comparatively slow, with <23 % of any given chemical/soil organic matter combination being mineralised over the experimental period. The highest mineralisation rates occurred in samples with the highest soil organic matter levels. The results also showed that 82.9 % ± 1.6 % of the acetamiprid applied was leached from the soil during repeated simulated rainfall events. This combined with the low sorption values, and the low rates of mineralisation, implies that acetamiprid is highly persistent and mobile within sandy soils. As a highly persistent neurotoxin with high invertebrate selectivity, the presence of neonicotinoids in soil presents a high toxicology risk to various beneficial soil organisms, including earthworms, as well as being at high risk of transfer to surrounding watercourses.

Soil structures and immobilization of typical contaminants in soils in response to diverse microplastics

Microplastics (MPs) accumulation in soil ecosystems has become a worldwide issue. The influence of MPs on soil structures and contaminant transport has not been clearly unraveled. This study conducted soil column experiments covering four different treatments: soil without MPs (CK), soil with 0.5 wt% polyethylene (S+PE), soil with 0.5 wt% polyacrylonitrile (S+PAN), and soil with 0.5 wt% polyethylene terephthalate (S+PET). The interconnections between changes in soil structures and shifts in sorption efficiency for typical hydrophobic organic contaminants (e.g., phenanthrene (PHE)) and heavy metal (e.g., lead (Pb (II)) by soils induced by MPs were explored. MPs-added soils contained fewer macro-aggregates and lower aggregate stability compared to CK. Three MPs, particularly PE, promoted PHE sorption by soils but reduced Pb (II) sorption, which occurred in soils with or without dissolved organic carbon. The comparison between experimental and predicted sorption capacity, as well as the one-point sorption data of different aggregate sizes, showed that such variations in PHE and Pb (II) sorption were related to the shifts in soil aggregates besides from the physical mixture of soils with MPs. This finding is perspective to give an in-depth understanding of the effects of different MPs types on soil micro-environments and transport for contaminants.

Mechanism evolution and prediction of carbamazepine sorption by mangrove plant residue-derived biochars

A mechanism for carbamazepine (CBZ) sorption by mangrove plant residue-derived biochars pyrolyzed at 200-700 °C (referred as MPR200-MPR700) was elucidated in this study. The experimental results demonstrated that the dominant sorption mechanism of biochars for CBZ was evolved from partition to adsorption with increasing pyrolysis temperature. The CBZ concentration-dependent contributions of partition and adsorption were controlled by the relative noncarbonized and carbonized fractions of biochars. The partition medium changed from a polymeric aliphatic fraction (mangrove plant residue [MPR]200-MPR400) to a more condensed aromatic phase (MPR500-MPR600), which made the partition less favorable. Meanwhile, the adsorption was selectively regulated by polarity (MPR200-MPR300) and porosity (MPR400-MPR700) for different biochars. A pragmatic model including the sorbent aromaticity index (H/C) was put forward to predict CBZ sorption to MPR200-MPR700 and other carbonaceous materials reported in the literature. The findings can be helpful in understanding CBZ-biochar interactions and developing effective sorbents (such as biochars) for pollutant sequestration.

Treating Agricultural Runoff with a Mobile Carbon Filtration Unit

Several classes of pesticides have been shown to impair water quality in California, including organophosphates, pyrethroids and neonicotinoids. Vegetative treatment systems (VTS) can reduce pesticide loads and associated toxicity in agricultural runoff, but many water-soluble pesticides such as neonicotinoids are not effectively treated by VTS, and VTS installation is not always an option for growers required to remove non-crop vegetation for food safety concerns. Recent studies have shown that biochar filtration can be used to remove soluble contaminants, especially when coupled with other VTS components. We evaluated a mobile carbon filter system consisting of a trailer-mounted tank containing approximately 600L (~ 180 kg) of biochar. Input water from a 437-hectare agricultural drainage was pre-filtered and treated with biochar during two multi-week study periods. Laboratory toxicity tests and chemical and nutrient analyses were conducted on input and output water. Pesticide concentrations were initially reduced by greater than 99%. Treatment efficacy declined linearly and was expected to remain at least 50% effective for up to 34 weeks. Toxicity was assessed with Ceriodaphnia dubia, Hyalella azteca and Chironomus dilutus. Significant input toxicity was reduced to non-toxic levels in 6 of 16 samples. Some input concentrations of the neonicotinoid imidacloprid and the pyrethroid cypermethrin exceeded organism-specific toxicity thresholds and benchmarks, but the overall causes of toxicity were complex mixtures of agricultural chemicals. Nutrients were not reduced by the biochar. Results demonstrate the utility of biochar in treating agricultural runoff and provide measures of the longevity of biochar under field conditions.

[Bmim]FeCl4 mediated inhibition and toxicity during anaerobic digestion: Dose-response kinetics, biochar-dependent detoxification and microbial resistance

[Bmim]FeCl₄, or 1‑butyl‑3-methylimidazolium tetrachloroferrate, is a typical ionic liquid (IL). Its recyclable, magnetic, multicomponent, and solvent-free nature makes it a particularly attractive ionic liquid for use in industrial processes. Despite its widespread use, the potential hazards that [Bmim]FeCl₄ might pose to the environment, including productive microorganisms, have not been explored. In this study, the dose-response of [Bmim]FeCl₄ in anaerobic digestion (AD) was investigated to assess the potential toxification and biochar-dependent detoxification in microbial communities, including enzymatic activity and molecule docking dynamics. Our results showed that methane production (31.52 mL_max/gVS) was sharply inhibited following [Bmim]FeCl₄ treatment. Moreover, increasing the dosage of [Bmim]FeCl₄ caused more dissolved organic matter (DOM) to be generated. Interestingly, 0.4 g/L of [Bmim]FeCl₄ could stimulate the high activity of microbial hydrolase and ATPase. However, a higher concentration of 2.65 g/L prevented these enzymatic processes from continuing. At the cellular level, higher concentration of [Bmim]FeCl₄ (>0.4 g/L) increased malondialdehyde (MDA) levels, leading to a higher cell lethal rate and weakening of the secondary structures of protein (especially, the amide I region). At the molecular level, the competitive H-bonding in the active sites caused low activity and consummated more energy. At the community level, structural equation modeling (SEM) revealed that [Bmim]FeCl₄ and biochar were the main drivers for microbial community succession. For instance, high [Bmim]FeCl₄ (8 g/L) benefited the growth of Clostridium sensu_stricto (from ≤1% to 27%). It is worth mentioning that biochar reversed the inhibition with high α-diversity, which caused a resurgence in the activity of previously inhibited ATPase and hydrolase. H₂-trophic methanogens (Methanolinea and Methaofastidisoum) were sensitive to [Bmim]FeCl₄ and decreased linearly while acetoclastic methanogens (Methanosaeta) were unchanged. These findings were consistent with the short-term activity tests and further verified by functional analysis.

Effects of different feedstocks-based biochar on soil remediation: A review

As a promising amendment, biochar has excellent characteristics and can be used as a remediation agent for diverse types of soil pollution. Biochar is mostly made from agricultural wastes, forestry wastes, and biosolids (eg, sewage sludge), but not all the biochar has the same performance in the improvement of soil quality. There is a lack of guidelines devoted to the selection of biochar to be used for different types of soil pollution, and this can undermine the remediation efficiency. To shed light on this sensitive issue, this review focus on the following aspects, (i) how feedstocks affect biochar properties, (ii) the effects of biochar on heavy metals and organic pollutants in soil, and (iii) the impact on greenhouse gas emissions from soil. Generally, the biochars produced from crop residue and woody biomass which are composed of lignin, cellulose, and hemicellulose are more suitable for organic pollution remediation and greenhouse gas emission reduction, while biochar with high ash content are more suitable for cationic organic pollutant and heavy metal pollution (manure and sludge, etc.). Additionally, the effect of biochar on soil microorganisms shows that gram-negative bacteria in soil tend to use WB biochar with high lignin content, while biochar from OW (rich in P, K, Mg, and other nutrients) is more able to promote enzyme activity. Finally, our recommendations on feedstocks selection are presented in the form of a flow diagram, which is precisely intended to be used as a support for decisions on the crucial proportioning conditions to be selected for the preparation of biochar having specific properties and to maximize its efficiency in pollution control.

Accessing biochar's porosity using a new low field NMR approach and its impacts on the retention of highly mobile herbicides

Agrowaste biochars [sugarcane straw (SS), rice husk (RH), poultry manure (PM), and sawdust (SW)] were synthesized at different pyrolysis temperatures (350, 450, 550, and 650 °C) to evaluate their potential to retain highly mobile herbicides, such as hexazinone and tebuthiuron that often contaminate water resources around sugarcane plantations. A new low field nuclear magnetic resonance approach based on decay due to diffusion in internal magnetic field (NMR-DDIF) was successfully used to determine biochar's porosity and specific surface area (SSA) to clear the findings of this work. SSA of pores with diameters >5.0 μm increased with pyrolysis temperatures and seemed to dictate biochar's retention, which was >70% of the applied amounts at 650 °C. These macropores appear to act as main arteries for herbicide intra-particle diffusion into smaller pores, thus enhancing herbicides retention. Biochar granulometry had little, but herbicide aging had a significant effect on sorption, mainly of tebuthiuron. However, soils amended with 10,000 kg ha^-1 of the biochars showed low sorption potential. Therefore, higher than usual biochar rates or proper incorporation strategies, i.e., surface incorporation, will be needed to remediate areas contaminated with these highly mobile herbicides, thus precluding their leaching to groundwaters.

Dynamics in imidacloprid sorption related to changes of soil organic matter content and quality along a 20-year cultivation chronosequence of citrus orchards

The on-going and extensive use of neonicotinoids occur in orchards. However, it is still unknown whether and how orchard management affects soil properties, especially the contents and structure of soil organic matter during orchard development, and their further influences on neonicotinoid persistence. Here, surface soil samples were collected from the citrus orchards with different cultivation ages (1, 10, 14, and 20 years), and their physicochemical properties were determined. Changes in the chemical structure of soil organic matter (SOM) were furtherly examined using solid-state CP/TOSS ¹³C NMR. Then, the sorption isotherms of imidacloprid in these soils were investigated. The sorption coefficient (K_d) of imidacloprid at C_e of 0.05 mg/L in the orchard soils increased by 19.4-23.3%, along a 20-year chronosequence of cultivation, which should be mainly ascribed to the increase of SOM. However, the organic carbon-normalized sorption coefficient (K_oc, sorption per unit mass of OM) of imidacloprid declined with increasing cultivation ages. Moreover, the polar and aliphatic domains of SOM had a significantly positive relation to the K_oc of imidacloprid, suggesting its key role in governing imidacloprid sorption. The results highlighted that reasonable management measures could be adopted to control the occurrence and fate of neonicotinoids in soils, mainly by affecting the content and quality of SOM.

Activation of biochar through exoenzymes prompted by earthworms for vermibiochar production: A viable resource recovery option for heavy metal contaminated soils and water

The industrial revolution and indiscriminate usage of a wide spectrum of agrochemicals account for the dumping of heavy metals in the environment. In-situ/ex-situ physical, chemical, and bioremediation strategies with pros and cons have been adopted for recovering metal contaminated soils and water. Therefore, there is an urgent requirement for a cost-effective and environment-friendly technique to combat metal pollution. Biochar combined with earthworms and vermifiltration is a suitable emerging technique for the remediation of metal-polluted soils and water. The chemical substances (e.g., sodium hydroxide, zinc chloride, potassium hydroxide, and phosphoric acid) have been used to activate biochar, which also faces several shortcomings. Studies reveal that extracellular enzymes have been used to activate biochar which is produced by earthworms and microbes that can alter the surface of the biochar. The present review focuses on the global scenario of metal pollution and its remediation through biochar activation using earthworms. The earthworms and biochar can produce "vermibiochar" which is capable of reducing the metal ions from contaminated water and soils. The vermifiltration can be a suitable technology for metal removal from wastewater/effluent. Thus, the biochar has a trick of producing entirely new options at a time when vermifiltration and other technologies are least expected. Further attention to the biochar-assisted vermifiltration of different sources of wastewater is required to be explored for the large-scale utilization of the process.

Conazole fungicides epoxiconazole and tebuconazole in biochar amended soils: Degradation and bioaccumulation in earthworms

Biochar usage in agriculture becomes increasingly important for the improvement of soil properties. However, from the perspective of pesticides, biochar can influence exposure to pesticides of both target and non-target organisms and also pesticides' fate in soil. Our study investigated degradation and bioaccumulation (in the Eisenia andrei earthworm) of two conazole fungicides, epoxiconazole and tebuconazole, added to high- and low-sorbing soils (by means of fungicides' sorption measured beforehand) amended with low-, moderate- and high-sorbing biochars at 0.2% and 2% doses. We aimed to investigate the effects of contrasting soil and biochar properties, different doses of biochar in soil-biochar mixtures, and different compounds on the degradation and bioaccumulation. We also wanted to explore if the beforehand determined sorption of fungicides on individual soils and biochars is manifested somehow in their degradation and/or bioaccumulation in soil-biochar mixtures. The biochars' presence in the soils promoted the degradation of fungicides with a clear effect of dose and soil, but less clear effect of biochar or compound. The bioaccumulation factors were higher in low-sorbing soil variants and also decreased with increasing biochar dose. For low-sorbing soil variants, the bioaccumulation was also influenced by the type of biochar corresponding to its sorbing potential and the possible effect on the bioavailability of the fungicides. Our results show that mixing of biochars with soils changes the fate and bioaccumulation of the conazole fungicides. However, the sorption results from original materials are not straightforwardly manifested in the more complex soil-biota system.

Impact of rice straw biochar addition on the sorption and leaching of phenylurea herbicides in saturated sand column

The application of phenylurea herbicides (PUHs) may lead to the extensive distribution in soils, while the role of straw biochar as a soil amendment on the transport and sorption of PUHs are still unclear. Thus, the transport and sorption behavior of three typical PUHs with rice straw biochar (RSB) was studied in both adsorption simulation experiments of aqueous solution and packed column experiments. The sorption mechanism of RSB to herbicides was investigated through batch sorption studies with three influencing factors including dosage of RSB, pH, and ionic strength (IS) with orthogonal test. The sorption coefficients were improved significantly by increasing the dosage of RSB, while there was no obvious influence by enhancing the pH and IS value. The optimal sorption conditions (pH value at 3, IS at 0.1 M, and RSB dosage at 60 mg) of three herbicides were set and the maximum removal rates of Monuron, Diuron, and Linuron were 41.9%, 25%, and 56.8%, respectively. The co-transport process of RSB and PUHs were investigated under different RSB dosage, pH value, and IS value. The retention effect increased greatly with enhancing the RSB dosage and pH value. However, IS did not have a significant influence on the retention of RSB, and therefore it had little effect on the adsorption capacity, which was consistent with the results of sorption experiments. The breakthrough curves (BTCs) for co-transport were well simulated by the two-site non-equilibrium convection-dispersion equation (CDE). Most of the regression coefficients (R²) were above 0.99, which uncovered the co-transport in packed column were affected by physical absorption and chemical forces. According to the fitting parameters analysis, the RSB particles and PUHs were subjected to a greater resistance and a stronger stability by reducing pH value in porous media. The presence of RSB increased the amount of dynamic sorption sites in the entire co-transport system, which led to a significant promotion of the PUHs' sorption and interception.

Highly efficient removal of imidacloprid using potassium hydroxide activated magnetic microporous loofah sponge biochar

Extensive application of imidacloprid (IMI) in pest control and its undesirable removal efficiency enabled it to be a critical global challenge. Low cost, efficient, sustainable and environment-friendly technologies are urgently needed to be developed to remove IMI from water. A novel adsorbent of potassium hydroxide activated magnetic microporous loofah sponge biochar (KOH+Fe/Zn-LBC) was synthesized, as well as its adsorption capacity and mechanisms for IMI were investigated in this study. KOH+Fe/Zn-LBC had the superior pore structure (surface area and pore volume) and its maximum adsorption capacity for IMI could reach 738 mg g^-1 at 298 K. Kinetics, isotherms, thermodynamics and characterization analysis suggested that pore filling, hydrogen bonding and π-π conjugation were its main adsorption mechanisms. Additionally, the thermodynamic parameters described that IMI adsorption was a spontaneous, endothermic and less random process. Particularly, the magnetic separation of KOH+Fe/Zn-LBC was beneficial for its reuse. Ultrasound and ethanol co-processing could effectively regenerate the used KOH+Fe/Zn-LBC and maintain its stable sustainable adsorption capacity (99.4% of its fresh adsorption capacity after five reuse cycles). Besides, KOH+Fe/Zn-LBC exhibited a stable adsorption capacity and environmental safety in a wide pH range. Therefore, KOH+Fe/Zn-LBC has the potential to be an efficient, green and sustainable adsorbent for neonicotinoids removal.

An Integrated Vegetated Treatment System for Mitigating Imidacloprid and Permethrin in Agricultural Irrigation Runoff

Pyrethroid and neonicotinoid pesticides control an array of insect pests in leafy greens, but there are concerns about the off-site movement and potential water quality impacts of these chemicals. Effective on-farm management practices can eliminate aquatic toxicity and pesticides in runoff. This project evaluated an integrated vegetated treatment system (VTS), including the use of polyacrylamide (PAM), for minimizing the toxicity of imidacloprid and permethrin pesticides in runoff. The VTS incorporated a sediment trap to remove coarse particles, a grass-lined ditch with compost swales to remove suspended sediment and insecticides, and granulated activated carbon (GAC) or biochar to remove residual insecticides. Runoff was sampled throughout the VTS and analyzed for pesticide concentrations, and aquatic toxicity using the midge Chironomusdilutus and the amphipod Hyalella azteca. In simulated runoff experiments, the VTS reduced suspended sediment load by 88%, and imidacloprid and permethrin load by 97% and 99%, respectively. In runoff events from a conventionally grown lettuce field, suspended sediment load was reduced by 98%, and insecticide load by 99%. Toxicity was significantly reduced in approximately half of the simulated runoff events, and most of the lettuce runoff events. Integrated vegetated treatment systems that include components for treating soluble and hydrophobic pesticides are vital tools for reducing pesticide load and occurrence of pesticide-related toxicity.

Behaviour of neonicotinoids in contrasting soils

Neonicotinoids are widely used to control insect pests in agriculture. Their presence in the environment can affect the health of non-target insects and aquatic animals. The behaviour of four neonicotinoids, namely imidacloprid, acetamiprid, thiacloprid and thiamethoxam, has been investigated in soils with contrasting characteristics to understand their migration in soil and ecological risk. Among the study neonicotinoids, thiamethoxam and thiacloprid were found to be the least and most sorbed neonicotinoids by all the soils, respectively (up to 186 time greater adsorption of thiacloprid), and their uptake was affected by the content of organic matter in the soil. Leaching studies in columns confirmed that thiamethoxam leached out of the soils readily, pointing out to a relatively high risk of ground water contamination with possible ecological impact when thiamethoxam is used in soils with low organic matter. In soil column studies, the soil with the lowest organic matter presents the greatest residue of neonicotinoids in the sub-surface (≤5 cm). In contrast the soil richer in organic matter presented most of the contamination deeper down in the column; a factor to be considered in the remediation from soil.

A critical review on the biochar production techniques, characterization, stability and applications for circular bioeconomy

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Recent research on remediation of toxic pollutants by biochar has been summarized.

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The production techniques of the biochar have been narrated.

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Biochar properties, stability and its environmental issues have been analysed.

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Applications of biochar in soil fertility and removing pollutants have been reported.

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The major stumbling block in biochar production is cost of production.

There is an upsurge enthusiasm for utilizing biochar produced from waste-biomass in different fields, to address the most important ecological issues. This review is focused on an overview of remediating harmful contaminants utilizing biochar. Production of biochar utilizing various systems has been discussed. Biochar has received the consideration of numerous analysts in building up their proficiency to remediate contaminants. Process parameters are fundamentally answerable for deciding the yield of biomass. Biochar derived from biomass is an exceptionally rich wellspring of carbon produced from biomass utilizing thermal combustion. Activating biochar is another particular region for the growing utilization of biochar for expelling specific contaminations. Closed-loop systems to produce biochar creates more opportunities. Decentralized biochar production techniques serve as an effective way of providing employment opportunities, managing wastes, increasing resource proficiency in circular bioeconomy. This paper also covers knowledge gaps and perspectives in the field of remediation of toxic pollutants using biochar.

Accumulation characteristics of endosulfan soil residues in soybean and reduction in their phytoavailability by treatment with powdered activated carbon

Powdered activated carbon (PAC) has been utilized for sorptive remediation of environmental sites contaminated with various organic chemicals. In the present study, time-dependent sorption/desorption characteristics of the α- and β-isomers and a sulfate-metabolite of endosulfan (ED) were investigated in PAC-amended soils to determine the optimal PAC amendment dosage. Subsequently, ED phytoavailability to soybean (Glycine max Merr.) plants were examined in the presence or absence of PAC under restricted laboratory conditions. Based on the results of sorption/desorption tests, the optimal dosage of PAC amendment for ED-contaminated soils was determined as 1% (w/w), and at this dosage, all ED residues were sorbed completely onto the PAC-amended soils without any desorption. In soil amended with 1% PAC, the extents of ED accumulated by soybean plants were reduced by 89.4-100.0% within 20 days compared to those extents observed in unamended controls. Moreover, PAC treatment precluded the formation of the toxic metabolite ED-sulfate in either the soil or soybean plants. Therefore, PAC amendment in ED-contaminated soils could be highly effective for limiting uptake of ED into plants from contaminated soil and may be useful as an alternative method to produce safe food resources from contaminated arable soils.

Recent advances in biochar application for water and wastewater treatment: a review

In the past decade, researchers have carried out a massive amount of research on the application of biochar for contaminants removal from aqueous solutions. As an emerging sorbent with great potential, biochar has shown significant advantages such as the broad sources of feedstocks, easy preparation process, and favorable surface and structural properties. This review provides an overview of recent advances in biochar application in water and wastewater treatment, including a brief discussion of the involved sorption mechanisms of contaminants removal, as well as the biochar modification methods. Furthermore, environmental concerns of biochar that need to be paid attention to and future research directions are put forward to promote the further application of biochar in practical water and wastewater treatment.

Comparison of the Relative Efficacies of Granulated Activated Carbon and Biochar to Reduce Chlorpyrifos and Imidacloprid Loading and Toxicity Using Laboratory Bench Scale Experiments

Pesticide loads and associated toxicity can be significantly reduced using integrated vegetated treatment systems, which remove moderately soluble and hydrophobic pesticides, but need a sorbent material to remove more soluble pesticides. Neonicotinoids such as imidacloprid are widely used insecticides, acutely toxic, and have been linked to a range of ecological effects. Laboratory experiments were conducted to test the sorptive capacity of granulated activated carbon and biochar for removing imidacloprid and the organophosphate insecticide chlorpyrifos in a scaled-down treatment system. Simulated irrigation water spiked with individual pesticides was treated with a bench-top system designed to mimic a 600 L carbon installation receiving 108,000 L of flow per day for sixteen days. Biochar reduced insecticides to less than detectable and non-toxic levels. Granulated activated carbon similarly reduced chlorpyrifos, but allowed increasing concentrations of imidacloprid to break through. Both media treated environmentally relevant concentrations, and would be effective if used under conditions with reduced particle loads.

Characterization of peanut-shell biochar and the mechanisms underlying its sorption for atrazine and nicosulfuron in aqueous solution

The aim of the present study was to investigate the sorption of atrazine and nicosulfuron onto several experimentally produced biochars, as well as to understand the influence of biochar structure on sorption mechanisms. Nine biochars were generated by pyrolyzing peanut shell at 300, 450, or 600 °C and exposing samples to each of the several deashing treatments: none, water or HCl. The sorption of atrazine and nicosulfuron by the nine biochars were evaluated. Biochars were characterized via elemental analyzer, BET-N₂ surface area, FTIR and XPS. Three kinetic models were used to fit the sorption kinetics data and both the Freundlich and dual-mode models described the sorption isotherms well. All the biochar samples exhibited high sorption affinity for both atrazine and nicosulfuron. The sorption mechanisms of the biochar included hydrophobic partition, π-π electron donor-acceptor interactions, H-bonding, and pore-filling mechanism, and these mechanisms were dependent on both the degree of biochar carbonization and the concentration of atrazine or nicosulfuron. Ash could bind to atrazine and nicosulfuron by specific interactions but played a negative role in the sorption, especially on high pyrolyzing temperature biochars. These results will facilitate the production of efficient and cheap adsorbents for reducing the risk of atrazine and nicosulfuron.

Sorption of ionic and neutral species of pharmaceuticals to loessial soil amended with biochars

To clarify the impact of biochar amendment on soil sorption for coexisting pharmaceuticals, wheat straw-derived biochars pyrolyzed at 300 and 700 °C (labeled as WS300 and WS700, respectively) were prepared. Batch experiments on ketoprofen (KTP), atenolol (ATL) and carbamazepine (CBZ) sorption to biochars, loessial soil and biochar-amended soils were conducted. The results indicated that sorption affinity of different species of pharmaceuticals to WS300 and WS700 was in the order of cationic ATL > neutral CBZ > anionic KTP. Cationic ATL had the highest sorption to biochars due to electrostatic attraction. Coexisting ATL, CBZ and KTP competed for the shared adsorption sites on carbonized phase of biochars, and π-π interactions were proposed to be the main sorption mechanism. Sorption coefficients (K_d) and nonlinearity of ATL, CBZ and KTP to soil increased when biochar was added (5% by weight), especially for WS700 with higher specific surface area. K_d values of the three pharmaceuticals to WS700-amended soil in either single solute or bisolute system were one to two orders of magnitude higher than those to soil, indicating the promoting role of WS700 in sorption of coexisting pharmaceuticals in soil. The study demonstrated the enhanced and competitive sorption of ionic and neutral species of pharmaceuticals to soil amended with biochars, which is helpful in designing biochar as effective sorbents for immobilization of pharmaceuticals in soil remediation.

The relative importance of different carbon structures in biochars to carbamazepine and bisphenol A sorption

Biochar, a carbon-rich material, has attracted immense attention owing to its applications in soil remediation. However, the mechanisms by which heterogeneous carbon structures of biochars immobilize organic contaminants are not yet fully understood. In this study, the noncondensed aromatic components in biochars were selectively removed through bleaching. Different techniques, such as ¹³C nuclear magnetic resonance, were applied to characterize the biochar compositions, and thus the role of the different carbon structures in organic contaminant sorption was discussed. The aromatic carbon structures in biochars were gradually developed and evolved from noncondensed to condensed structure with increasing pyrolytic temperatures from 300 to 700 °C. Based on elemental analysis, the carbon removed by bleaching decreased from 43.9% to 5.92% with increasing temperatures. After the surface area normalization of the apparent sorption, bleaching increased the sorption of carbamazepine and bisphenol A on biochars produced at 500 °C, but not for those produced at 300 and 700 °C. Bleaching removed noncondensed aromatics and enriched condensed aromatics, which resulted in increased sorption. However, bleaching also resulted in the blockage of micropores in biochars with abundant condensed aromatics, causing decreased sorption. The apparent sorption was determined by the balancing of these two opposite effects.

Biochar Addition Enhances Phenanthrene Fixation in Sediment

Biochar is believed to be promising for soil contaminant stabilization due to its large adsorption capacity. However, study in sediment is rare, especially with the aging effect. In the present study, a plant biomass-derived biochar was added to phenanthrene polluted sediment, in order to investigate its performance in sediment remediation. During the incubation period of 60 days, it was observed that the partition coefficient of phenanthrene increased in sediment either with or without biochar addition, as a result of aging process. Whilst, the biochar-added sediments showed much higher partition coefficients, as well as more curved adsorption isotherms, suggesting larger retention of the contaminant. Under the extreme extraction by strong surfactant, the release ratio of phenanthrene from polluted sediment was significantly reduced from 60% to 5% by 0.5% (w/w) addition of biochar. These results suggested that biochar would be applicable for improving the adsorption of organic pollutant in sediment, and the adsorbed organic pollutant would be stably fixed during aging as a result of the increased affinity.

Quantitative evaluation of relationships between adsorption and partition of atrazine in biochar-amended soils with biochar characteristics

Atrazine (ATZ) adsorption in two natural soils amended with biochars produced from different feedstocks at 300, 500, and 700 °C were investigated; further, the relationships between the surface and partition adsorption capacities of ATZ in biochar-amended soils with biochar characteristics were quantitatively evaluated. The results revealed that high aromaticity, hydrophobicity, and low polarity of biochar facilitated ATZ adsorption. The addition of selected biochars significantly increased the adsorption of ATZ on paddy soil (PS) and black soil (BS) by 5.2–7.5 times and 2.3–4.2 times, respectively. On the contrary, the degree of increase in surface adsorption was much higher than that in partition adsorption, mainly due to the role of the specific adsorption of ATZ on biochar. Meanwhile, the respective contributions of surface and partition adsorptions to the total ATZ adsorption on biochar-amended soil changed with different addition amounts of biochar. The multiple nonlinear regression analysis demonstrated the linear dependence of H/C ratio, (O + N)/C ratio, and specific surface area (SSA) of biochar on the surface adsorption capacity of biochar-amended PS and BS, as well as the linear dependence of organic carbon and ash contents on the partition adsorption capacity of biochar-amended PS and the linear dependence of the H/C ratio and SSA on the partition adsorption capacity of biochar-amended BS. In biochar-amended soil systems, interactions between biochar and soil could affect ATZ adsorption, and organic matter in biochar might compensate for the role of soil organic matter in the competition for adsorption sites with a decrease in the biochar pyrolysis temperature.

Adsorption of atrazine (ATZ) in two natural soils amended with different biochars was investigated, and the relationships of adsorption capacity of biochar-amended soils with biochar characteristics were also quantitatively evaluated.

Impact of biochar amendment in agricultural soils on the sorption, desorption, and degradation of pesticides: A review

Extensive and inefficient use of pesticides over the last several decades resulted in serious soil and water contamination by imposing severe toxic effects on living organisms. Soil remediation using environment-friendly amendments to counteract the presence of pesticides in soil seems to be one suitable approach to solve this problem. Biochar has emerged as a promising material for adsorbing and thus decreasing the bioavailability of pesticides in polluted soils, due to its high porosity, surface area, pH, abundant functional groups, and highly aromatic structure, mainly depending on the feedstock and pyrolysis temperature. However, biochar effects and mechanisms on the sorption and desorption of pesticides in the soil are poorly understood. Either high or low pyrolysis temperature has both positive and negative effects on sorption of pesticides in soil, one by larger surface area and the other by a large number of functional groups. Therefore, a clear understanding of these effects and mechanisms are necessary to engineer biochar production with desirable properties. This review critically evaluates the role of biochar in sorption, desorption, and degradation of pesticides in the soil, along with dominant properties of biochar including porosity and surface area, pH, surface functional groups, carbon content and aromatic structure, and mineralogical composition. Moreover, an insight into future research directions has been provided by evaluating the bioavailability of pesticide residues in the soil, effect of other contaminants on pesticide removal by biochar in soils, effect of pesticide properties on its behavior in biochar-amended soils, combined effect of biochar and soil microorganisms on pesticide degradation, and large-scale application of biochar in agricultural soils for multifunction.

Roles of hydrophobic and hydrophilic fractions of dissolved organic matter in sorption of ketoprofen to biochars

Hydrophobic acid (HoA) and hydrophilic neutral (HiN) are two major fractions of dissolved organic matter (DOM). Their role in the sorption of ketoprofen (KTP) to wheat straw-derived biochars pyrolyzed at 300 °C (WS300) and 700 °C (WS700) was investigated to further probe the mechanisms responsible. WS700 has much higher pore volume and specific surface area (SSA) than WS300. Loading of HoA and HiN resulted in surface coverage of biochars. HoA with larger molecular size led to more pore blockage of biochars than HiN. Higher HoA binding affinity also caused a stronger competition with KTP on biochars. These factors reduced the accessibility of sorption sites for KTP, and significantly inhibited KTP sorption to biochar of lower SSA (i.e., WS300) by HoA. Water solubility (S_w) of KTP was slightly enhanced (3%) in the presence of HoA. In contrast, the presence of HiN reduced (22%) S_w of KTP. The decreased S_w of KTP by HiN exerted a more dominant influence than its competitive and loading effects, thus led to apparent enhanced sorption of KTP, especially to biochar of higher SSA (i.e., WS700). The results demonstrated the diverse effects of HoA and HiN on KTP sorption, which is helpful in understanding pharmaceutical-DOM-biochar interactions and environmental behaviors of pharmaceuticals.

Effects of biochars on the fate of acetochlor in soil and on its uptake in maize seedling

Biochar (BC) can alter the fate and bioavailability of pesticides in soil. In this study, the effects of three types of BCs (made of crofton weed, wood chips and rice hull) on the sorption of acetochlor, a common herbicide, were investigated. The acetochlor sorption constants (K_f value) were 309.96 μg^1-nL^n/kg (biochars made of ricehull, BCR), 3.54 μg^1-nL^n/kg (biochars made of crofton weed, BCH) and 2.27 μg^1-nL^n/kg (biochars made of wood chips, BCW). The persistence of acetochlor was 8 times greater when 1% BCR was added to the soil. Moreover, the half-life of acetochlor increased with increasing amounts of BC in the soil. The soil was amended with BCH (made of crofton weed) for two different aging period (10 d and 20 d) to evaluate the effects of aged BC on acetochlor accumulation in maize seedlings (Zea mays L). Amendment with 10 d-aged BCH in soil decreased the bioaccumulation of acetochlor. However, the concentrations and bioconcentration factors in maize cultivated in 20 d-aged BCH-amended soils were significantly higher than those in soil with no BCH amendments and with 10 d-aged BCH amendments. These results imply that BC aged in soil for a long period can increase the bioaccumulation of acetochlor in plants and the influences of BC on environmental risks of pesticides must be further clarified.

Phosphoric acid pretreatment enhances the specific surface areas of biochars by generation of micropores

Biochars are being increasingly applied in soil for carbon sequestration, fertility improvement, as well as contamination remediation. Phosphoric acid (H₃PO₄) pretreatment is a method for biochar modification, but the mechanism is not yet fully understood. In this work, biochars and the raw biomass were treated by H₃PO₄ prior to pyrolysis. Due to an acid catalysis and crosslink, the micropores of the pretreated particles were much more than those without H₃PO₄ pretreatment, resulting in the dramatical enhancement of specific surface areas of the pretreated particles. Crystalline cellulose (CL) exhibited a greater advantage in the formation of micropores than of amorphous lignin (LG) with H₃PO₄ modification. The formation mechanisms of micropores were: (a) H⁺ from H₃PO₄ contributes to micropores generation via H⁺ catalysis process; (b) the organic phosphate bridge protected the carbon skeleton from micropore collapse via the crosslinking of phosphate radical. The sorption capacities to carbamazepine (CBZ) and bisphenol A (BPA) increased after H₃PO₄ modification, which is ascribed to the large hydrophobic surface areas and more abundant micropores. Overall, H₃PO₄ pretreatment produced biochars with large surface area and high abundance of porous structures. Furthermore, the H₃PO₄ modified biochars can be applied as high adsorbing material as well as P-rich fertilizer.

Sorption of sulfathiazole in the soil treated with giant Miscanthus-derived biochar: effect of biochar pyrolysis temperature, soil pH, and aging period

Agricultural soil was treated with biochar (5% w/w) produced from two pyrolysis temperatures (400 and 700 °C) of giant Miscanthus (GMC-400 and GMC-700, respectively), and the subsequent sorption of sulfathiazole (STZ) was evaluated as a function of pH (2, 5, and 7) and aging period (0, 3, and 6 months). Because sorption was nonlinear, with 0.51 < N < 0.75, the linearized sorption coefficient (K _d^*) was used for the comparison across samples. The K _d^* of GMC-400 treatment (3.96-9.96 L kg^-1) was higher than that of GMC-700 treatment (1.27-3.38 L kg^-1). In laps of aging period over 6 months, the sorption of GMC-400-treated soil had gradually increased to be 3.3 times higher than that of untreated soil, whereas there was no statistical difference for GMC-700 treatment. Results of FTIR and SEM analyses revealed that the number of O-containing functional groups in the GMC-400 treatment increases and the micropores of GMC-700 are deformed over time. Sorption was also pH-dependent in the order of pH 2 > pH 5 > pH 7. The sorption hysteresis (H) index for the GMC-400 treatment was higher at pH 7 (3.99) than at pH 5(2.53), and both values had increased after 6 months (4.18 and 3.17, respectively). The results of this study clearly demonstrate that the sorption of STZ on GMC-treated soils is greatly enhanced, mainly through the greater micropore surfaces, the abundance of hydrophilic functional groups over time, and π⁺-π electron donor-acceptor interaction at low pH.

Biochars change the sorption and degradation of thiacloprid in soil: Insights into chemical and biological mechanisms

One interest of using biochar as soil amendment is to reduce pesticide adverse effects. In this paper, the sorption and degradation of thiacloprid (THI) in a black soil amended by various biochars were systematically investigated, and the mechanisms therein were explored by analyzing the changes in soil physicochemical properties, degrading enzymes and genes and microorganism community. Biochar amendment increased THI sorption in soil, which was associated with an increase in organic carbon and surface area and a decrease in H/C. Amendments of 300-PT (pyrolyzing temperature) biochar promoted the biodegradation of THI by increasing the microbe abundance and improving nitrile hydratase (NHase) activity. In contrast, 500- and 700-PT biochar amendments inhibited biodegradation by reducing THI availability and changing NHase activity and THI-degradative nth gene abundance, and instead promoted chemical degradation mainly through elevated pH, active groups on mineral surface and generation of •OH and other free radicals. Furthermore, THI shifted the soil microbial community, stimulated the NHase activity and elevated nth gene abundance. Biochar amendments also changed soil bacterial community by modulating soil pH, dissolved organic matter and nitrogen and phosphorus levels, which further influenced THI biodegradation. Therefore, the impact of biochars on the fate of a pesticide in soil depends greatly on their type and properties, which should be comprehensively examined when applying biochar to soil.

Isolation and characterization of biochar-derived organic matter fractions and their phenanthrene sorption

Chemical composition and pollutant sorption of biochar-derived organic matter fractions (BDOMs) are critical for understanding the long-term environmental significance of biochar. Phenanthrene (PHE) sorption by the humic acid-like (HAL) fractions isolated from plant straw- (PLABs) and animal manure-based (ANIBs) biochars, and the residue materials (RES) after HAL extraction was investigated. The HAL fraction comprised approximately 50% of organic carbon (OC) of the original biochars. Results of XPS and ¹³C NMR demonstrated that the biochar-derived HAL fractions mainly consisted of aromatic clusters substituted by carboxylic groups. The CO₂ cumulative surface area of BDOMs excluding PLAB-derived RES fractions was obviously lower than that of corresponding biochars. The sorption nonlinearity of PHE by the fresh biochars was significantly stronger than that of the BDOM fractions, implying that the BDOM fractions were more chemically homogeneous. The BDOMs generally exhibited comparable or higher OC-normalized distribution coefficients (K_oc) of PHE than the original biochars. The PHE logK_oc values of the fresh biochars correlated negatively with the micropore volumes due to steric hindrance effect. In contrast, a positive relationship between the sorption coefficients (K_d) of BDOMs and the micropore volumes was observed in this study, suggesting that pore filling could dominate PHE sorption by the BDOMs. The positive correlation between the PHE logK_oc values of the HAL fractions and the aromatic C contents indicates that PHE sorption by the HAL fractions was regulated by aromatic domains. The findings of this study improve our knowledge of the evolution of biochar properties after application and its potential environmental impacts.

Biochar alleviates the toxicity of imidacloprid and silver nanoparticles (AgNPs) to Enchytraeus albidus (Oligochaeta)

The present study investigated the use of biochar for the alleviation of the toxic effects of a nanosilver colloidal dispersion and a chloronicotinyl insecticide. The survival and reproduction of the potworm Enchytraeus albidus were assessed after exposure to imidacloprid and silver nanoparticles (AgNPs). E. albidus was exposed to 0, 25, 50, 100, 200, and 400 mg imidacloprid/kg and 0, 5, 25, 125, and 625 mg Ag/kg for 21 days in 10% biochar amended and non-biochar amended OECD artificial soil. In both exposure substrates, the effects of imidacloprid on survival were significant in the two highest treatments (p < 0.01). No biochar effect was observed as survival was statistically similar in both soils after exposure to imidacloprid. In the case of AgNPs, significant mortality was only observed in the highest AgNP treatments in both the amended and non-amended soils (p < 0.05). Nevertheless, statistically greater survival occurred in the biochar-amended treatment (p < 0.05). Reproduction results showed a more pronounced biochar effect with an EC₅₀ = 22.27 mg imidacloprid/kg in the non-amended soil and a higher EC₅₀ = 46.23 mg imidacloprid/kg in the biochar-amended soil. This indicated a 2-fold decrease in imidacloprid toxicity due to biochar amendment. A similar observation was made in the case of AgNPs where a reproduction EC₅₀ = 166.70 mg Ag/kg soil in the non-amended soil increased to an EC₅₀ > 625 mg Ag/kg soil (the highest AgNP treatment) in the amended soil. This indicated at least a 3.7-fold decrease in AgNPs toxicity due to biochar amendment. Although more studies may be needed to optimize the easing effects of biochar on the toxicity of these chemicals, the present results show that biochar could be useful for the alleviation of the toxic effects of imidacloprid and silver nanoparticles in the soil.

Sorption mechanisms of neonicotinoids on biochars and the impact of deashing treatments on biochar structure and neonicotinoids sorption

To elucidate the sorption affinity of biochars for neonicotinoid pesticides and the influence of biochar structure on sorption mechanisms therein, 24 biochar samples were obtained by pyrolyzing maize straw and pig manure at pyrolyzing temperatures (PTs) of 200-700 °C and by further deashing them using acids, and the sorption of three typical neonicotinoids, imidacloprid, clothianidin and thiacloprid on untreated and acid-deashed biochars were evaluated. All the biochar samples could efficiently adsorb the three neonicotinoids and multiple mechanisms were involved in sorption. With the increasing PTs, hydrophobic partition sorption increased, but had a declined contribution to the total sorption as revealed by a dual-mode model. Besides hydrophobic partition, specific interactions like cation-π electron donor acceptor (EDA) interactions (only for protonated IMI and CLO) and hydrogen bond and contributed much to the sorption on low-PT (≤500 °C) biochars, while the sorption on those high-PT (>500 °C) biochars mainly depended on pore-filling strengthened by cation-π and p/π-π EDA interactions. Thiacloprid showed stronger sorption on untreated biochars compared to imidacloprid and clothianidin, due to its greater ability to form hydrogen bond and hydrophobic interactions. Acid-deashing treatments increased the relative percentage contents of organic carbon, bulk O, aromaticity and O-containing functional groups, surface area and pore volume of biochars. The ash can bind neonicotinoids by specific interactions but played a negative role in the whole sorption on high-PT biochars by covering the inner sorption sites of organic moieties and blocking the micropores in biochars. The results acquired in the present study will help us to get deep insight in the comprehensive sorption mechanisms of polar pesticides on biochar and the effects of biochar structure.

Intensify production, transform biomass to energy and novel goods and protect soils in Europe-A vision how to mobilize marginal lands

The rapid increase of the world population constantly demands more food production from agricultural soils. This causes conflicts, since at the same time strong interest arises on novel bio-based products from agriculture, and new perspectives for rural landscapes with their valuable ecosystem services. Agriculture is in transition to fulfill these demands. In many countries, conventional farming, influenced by post-war food requirements, has largely been transformed into integrated and sustainable farming. However, since it is estimated that agricultural production systems will have to produce food for a global population that might amount to 9.1 billion by 2050 and over 10 billion by the end of the century, we will require an even smarter use of the available land, including fallow and derelict sites. One of the biggest challenges is to reverse non-sustainable management and land degradation. Innovative technologies and principles have to be applied to characterize marginal lands, explore options for remediation and re-establish productivity. With view to the heterogeneity of agricultural lands, it is more than logical to apply specific crop management and production practices according to soil conditions. Cross-fertilizing with conservation agriculture, such a novel approach will provide (1) increased resource use efficiency by producing more with less (ensuring food security), (2) improved product quality, (3) ameliorated nutritional status in food and feed products, (4) increased sustainability, (5) product traceability and (6) minimized negative environmental impacts notably on biodiversity and ecological functions. A sustainable strategy for future agriculture should concentrate on production of food and fodder, before utilizing bulk fractions for emerging bio-based products and convert residual stage products to compost, biochar and bioenergy. The present position paper discusses recent developments to indicate how to unlock the potentials of marginal land.

Sorption, desorption and degradation of neonicotinoids in four agricultural soils and their effects on soil microorganisms

In this study, the sorption, desorption and degradation of three neonicotinoids, imidacloprid (IMI), clothianidin (CLO) and thiacloprid (THI), and their effects on microorganisms in four different agricultural soils were systematically evaluated. The sorption of neonicotinoids on the soils was generally low with distribution coefficients (K_d) up to 16.2L/kg at C_e of 0.05mg/L following the order THI>IMI≈CLO, and the sorption were mainly influenced by the soil organic carbon content. The percentage degradation rates of the pesticides in different soils ranged from 25.4% to 80.9%, all following the order THI>IMI≈CLO. All the three neonicotinoids degraded much faster under non-sterilized conditions than sterilized conditions, indicating considerable contribution of biodegradation. The total degradation or biodegradation of neonicotinoids was the fastest in the soil with the highest organic carbon content, and the neonicotinoids' bioavailability was not the primary influencing factor due to their weak sorption. The chemical degradation was mainly affected by pH and cation exchange capacity. The degradation of neonicotinoids occurred mainly via nitrate reduction, cyano hydrolysis and chloropyridinyl dechlorination. High-throughput sequencing data showed that the microbial community structure and abundance changed greatly in neonicotinoid-spiked soils as compared to the control, which might influence their degradation pathways. Some microbe families associated with the biodegradation of neoniconoids were found, which were all belonging to Proteobacteria and Actinobacteria. The degradation of neoniconoids influenced the soil nitrifying process. The present study provides valuable information for comprehensively understanding the fate of neonicotinoids in soils.

Correlations and adsorption mechanisms of aromatic compounds on biochars produced from various biomass at 700 °C

Knowledge of adsorption behavior of organic contaminants on high heat temperature treated biochars is essential for application of biochars as adsorbents in wastewater treatment and soil remediation. In this study, isotherms of 25 aromatic compounds adsorption on biochars pyrolyzed at 700 °C from biomass including wood chips, rice straw, bamboo chips, cellulose, lignin and chitin were investigated to establish correlations between adsorption behavior and physicochemical properties of biochars. Isotherms were well fitted by Polanyi theory-based Dubinin-Ashtakhov (DA) model with three parameters, i.e., adsorption capacity (Q⁰) and adsorption affinity (E and b). Besides the negative correlation of Q⁰ with molecular maximum cross-sectional areas (σ) of organic compounds, positive correlations of Q⁰ with total pore volume (V_total) and average diameter of micropore (D) of biochars were observed, indicating that adsorption by biochars is captured by the pore-filling mechanism with molecular sieving effect in biochar pores. Linear solvation energy relationships (LSERs) of adsorption affinity (E) with solvatochromic parameters of organic compounds (i. e., α_m and π^∗) were established, suggesting that hydrophobic effect, π-π interaction and hydrogen-bonding interaction are the main forces responsible for adsorption. The regression coefficient (π₁) and intercept (C) of obtained LSERs are correlated with biochar H/C and R_micro, respectively, implying that biochars with higher aromaticity and more micropores have stronger π-π bonding potential and hydrophobic effect potential with aromatic molecule, respectively. However, hydrogen-bonding potential of biochars for organic molecules is not changed significantly with properties of biochars. A negative correlation of b with biochar H/C is also obtained. These correlations could be used to predict the adsorption behavior of organic compounds on high heat temperature treated biochars from various biomass for the application of biochars as sorbents and for the estimating of environmental risks of organic compounds in the present of biochars.