A critical review of different factors governing the fate of pesticides in soil under biochar application

Trace element removal from wastewater by agricultural biowastes: A data analysis on removal efficacy and optimized conditions

Valorization of agricultural biowastes to biosorbents provides an excellent opportunity to recycle these wastes into valuable products and filtration of contaminants, especially potentially toxic trace elements in aquatic ecosystems. Water contamination with potentially toxic trace elements is a widespread global issue. Various agricultural biosorbents have been tested to remove trace elements from wastewater. Despite abundant research, there are scarce studies regarding the critical data analysis on trace elements removal efficiency by agricultural biowastes under various conditions. This review critically delineates the data analysis of recent literature published from 2018 to 2024 for a critical comparison of different agricultural biosorbents and the applied conditions to remove trace elements from aqueous media. Data analysis (based on 1188 observations) revealed that the mean trace element removal by agricultural biowaste-derived biosorbents from contaminated water was 75 %, ranging from 2 to 100 %. The most frequently reported removal efficiencies of agricultural biosorbents were 90-100 %. Notably, few agricultural biosorbents such as banana peel demonstrated the highest removal efficiency of 97 %, followed by cassava peels at 92 %, emphasizing the significance of recycling these materials for sustainable trace element removal from wastewater. Data analysis revealed that the trend for trace element removal from wastewater follows a descending order, with zinc exhibiting the highest removal rate at 81 %, followed closely by lead at 80 %. This trend continues with arsenic at 75 %, nickel and cadmium both at 70 %, and so forth. Thus, agricultural biosorbents play a pivotal role in this process, showcasing their potential in waste valorization and environmental remediation. Hence, the present review article is expected to contribute towards the comparative efficiency of various agricultural biosorbents, and the selection of the best biosorbents, depending on applied conditions for trace element removal from targeted wastewater treatment facilities.

Enhancement of caproate production via carboxylate chain elongation with sequential fermentation facilitated by biochar: A corn stover full-component utilization perspective

In this study, caproate was synthesized from corn stover through sequential fermentation, and biochar was prepared from unhydrolyzable corn stover by pyrolysis to utilize full-component of corn stover. The results indicate that the caproate concentration in the unhydrolyzable corn stover biochar (UCSB) group was 2.2 times higher than that of the control group, and the fermentation start-up time was shortened by 18 days. Mechanistic analysis suggested that the rough surface of UCSB facilitated microbial colonization and reduced product inhibition. Genes expression analysis further demonstrated that UCSB significantly upregulated crucial functional genes responsible for ethanol oxidation and the reverse β-oxidation pathway, ultimately resulting in enhanced caproate production. The successful utilization of UCSB derived from unhydrolyzable solid residue effectively boosted fermentation, leading to a 37 % increase in the carbon utilization efficiency of corn stover. This study offering valuable insights for the high-value and full-component utilization of lignocellulosic biomass.

Dioxin-like polychlorinated biphenyls (dl-PCB) in hydrochars and biochars: Review of recent evidence, pollution levels, critical gaps, formation mechanisms and regulations

Contamination of chars with dioxin-like polychlorinated biphenyls (dl-PCB) significantly limits their use and hinders their deployment in the circular bioeconomy, specifically in applications that may lead to dietary exposure. Here, for the first time, we review the levels of contamination of chars produced from pyrolysis and hydrothermal carbonisation (HTC) with dl-PCB congeners. We conduct a detailed and critical examination of the role played by the processing parameters, such as temperature and residence time, and the reaction mechanisms, to detoxify the biomass under an oxygen-free atmosphere during its valorisation. The PCB-based toxicity of biomass depends mostly on the abundance of dl-PCB in the raw material, and on the dechlorination and other transformation processes that operate during the treatment. The key dechlorination steps make the toxicity of hydrochars pass through a maximum with increasing treatment time, whereas the toxicity of biochars in pyrolysis decreases monotonically. Pyrolysis displays more complex mechanistic pathways of volatilisation, dechlorination, degradation of PCB rings, minor de novo formation of dl-PCB in case of air leaks, and concentrating persistent organic pollutants (POP) in char matrices. In contrast, the mechanisms responsible for the evolution of toxicity in HTC processes comprise the dechlorination, possible chlorine position shift, and biomass densification. The kinetic model developed in this review affords insight into the evolution of the hydrochar toxicity that depends on process temperature and treatment time. The dl-PCB concentrations in treated biomass generally range from 1.06 ng WHO2005-TEQ (kg DM)-1 to 11.7 ng WHO2005-TEQ (kg DM)-1, whereas for biochars produced from contaminated sediments the toxicity varies from 0.00662 ng WHO1998-TEQ (kg DM)-1 to 1.42 ng WHO1998-TEQ (kg DM)-1. DM stands for dry matter, TEQ for toxic equivalency, and WHO1998 means the application of the toxic equivalency factors (TEF) set by the World Health Organization (WHO) in 1998 to calculate the TEQ. Finally, we identify the crucial gaps in the literature, review the regulations governing the use of biomass in feed and in the environment, and provide suggestions for future research. The findings in this article provide both the technical understanding of how to minimise the formation of dl-PCB in the production of chars and suggest modifications to the current guidelines. The latter will increase the consumer's trust in valorised biomass, leading to its wider acceptance in the circular bioeconomy as feed supplements and soil additives.

Biochar for ameliorating soil fertility and microbial diversity: From production to action of the black gold

This article evaluated different production strategies, characteristics, and applications of biochar for ameliorating soil fertility and microbial diversity. The biochar production techniques are evolving, indicating that newer methods (including hydrothermal and retort carbonization) operate with minimum temperatures, yet resulting in high yields with significant improvements in different properties, including heating value, oxygen functionality, and carbon content, compared to the traditional methods. It has been found that the temperature, feedstock type, and moisture content play critical roles in the fabrication process. The alkaline nature of biochar is attributed to surface functional groups and addresses soil acidity issues. The porous structure and oxygen-containing functional groups contribute to soil microbial adhesion, affecting soil health and nutrient availability, improving plant root morphology, photosynthetic pigments, enzyme activities, and growth even under salinity stress conditions. The review underscores the potential of biochar to address diverse agricultural challenges, emphasizing the need for further research and application-specific considerations.

Evaluation of Fenton-like reaction for sorption and degradation of kasugamycin in the presence of biochar

Although the use of biochar as an adsorbent for the removal of various pollutants from wastewater is well established, the use of biochar/modified biochar for the scavenging of antibiotics from aqueous media in the Fenton-like system receives less attention. The highest kasugamycin (KSM) adsorption capacity (5.0 mg g-1) was obtained from the pristine biochar at the lowest initial pH of 3 in Fenton-like system. The Fenton-like system improved the KSM adsorption capacity of pristine biochar by 222.2%, 169.9%, and 159.9% at 25 °C, 35 °C, and 45 °C comparing to control, respectively, and it also increased adsorption capacity by 97.4%, 63.8%, and 56.8% comparing to modified biochar. The amounts of biochar applied and the Fenton-like system affected KSM mineralization and degradation. The KSM degradation products had a significant amount of small molecular organic matter (m/z 384) and a tetrahydropyran structure that was difficult to degrade. The highly efficient degradation of KSM in Fenton-like system can be attributed to the generation of large amounts of hydroxyl radical (·OH) and functional groups (C=C, C=O, etc.).

Exploring the significance of different amendments to improve phytoremediation efficiency: focus on soil ecosystem services

Phytoremediation is recognized as an environmentally, economically and socially efficient phytotechnology for the reclamation of polluted soils. To improve its efficiency, several strategies can be used including the optimization of agronomic practices, selection of high-performance plant species but also the application of amendments. Despite evidences of the benefits provided by different types of amendments on pollution control through several phytoremediation pathways, their contribution to other soil ecosystem functions supporting different ecosystem services remains sparsely documented. This current review aims at (i) updating the state of the art about the contribution of organic, mineral and microbial amendments in improving phytostabilization, phytoextraction of inorganic and phytodegradation of organic pollutants and (ii) reviewing their potential beneficial effects on soil microbiota, nutrient cycling, plant growth and carbon sequestration. We found that the benefits of amendment application during phytoremediation go beyond limiting the dispersion of pollutants as they enable a more rapid recovery of soil functions leading to wider environmental, social and economic gains. Effects of amendments on plant growth are amendment-specific, and their effect on carbon balance needs more investigation. We also pointed out some research questions that should be investigated to improve amendment-assisted phytoremediation strategies and discussed some perspectives to help phytomanagement projects to improve their economic sustainability.

Bifenthrin's Environmental Fate: An Insight Into Its Soil Sorption and Degradation Studies

To fully comprehend each pesticide's behavior and interactions with soil and the environment, a thorough and nuanced analysis of each one is thought necessary. In this study, 10 randomly selected heterogeneous soil samples, each with distinct characteristics, were subjected to sorption trials as well as disintegration tests using biodegradation, hydrolysis, and photolysis. For sorption tests, the batch equilibrium approach was used, which revealed a dependence on the soils' physicochemical characteristics. Bifenthrin's distribution coefficient (K d ) varied from 7.27 to 25.89 μg·ml-1, with R 2 values varying from 0.92 to 0.99. Each soil physicochemical characteristic was associated with the various sorptive outcomes, which suggested an exothermic adsorptive reaction based on the negative thermodynamic values. The hydrolysis, soil-induced biodegradation, and photolysis processes had the shortest half-lives of bifenthrin, measuring 13.5 days, 12 days, and 121.5 days, respectively. According to these findings, bifenthrin has a moderate amount of binding and stability in soil, which makes partial decomposition of parent and daughter molecules challenging. This research advances our knowledge of bifenthrin's deteriorating processes and aids in the creation of cutting-edge strategies for ecological restoration using natural processes.

A critical review of biochar for the remediation of PFAS-contaminated soil and water

Per- and polyfluoroalkyl substances (PFAS) present significant environmental and health hazards due to their inherent persistence, ubiquitous presence in the environment, and propensity for bioaccumulation. Consequently, the development of efficacious remediation strategies for soil and water contaminated with PFAS is imperative. Biochar, with its unique properties, has emerged as a cost-effective adsorbent for PFAS. Despite this, a comprehensive review of the factors influencing PFAS adsorption and immobilization by biochar is lacking. This narrative review examines recent findings indicating that the application of biochar can effectively immobilize PFAS, thereby mitigating their environmental transport and subsequent ecological impact. In addition, this paper reviewed the sorption mechanisms of biochar and the factors affecting its sorption efficiency. The high effectiveness of biochars in PFAS remediation has been attributed to their high porosity in the right pore size range (>1.5 nm) that can accommodate the relatively large PFAS molecules (>1.02-2.20 nm), leading to physical entrapment. Effective sorption requires attraction or bonding to the biochar framework. Binding is stronger for long-chain PFAS than for short-chain PFAS, as attractive forces between long hydrophobic CF2-tails more easily overcome the repulsion of the often-anionic head groups by net negatively charged biochars. This review summarizes case studies and field applications highlighting the effectiveness of biochar across various matrices, showcasing its strong binding with PFAS. We suggest that research should focus on improving the adsorption performance of biochar for short-chain PFAS compounds. Establishing the significance of biochar surface electrical charge in the adsorption process of PFAS is necessary, as well as quantifying the respective contributions of electrostatic forces and hydrophobic van der Waals forces to the adsorption of both short- and long-chain PFAS. There is an urgent need for validation of the effectiveness of the biochar effect in actual environmental conditions through prolonged outdoor testing.

Kinetic study, byproducts characterization and photodegradation pathway of profoxydim in a biochar water soil system

The study focused on the photodegradation of profoxydim, a low-toxicity cyclohexanedione herbicide commonly used in rice crops, under simulated sunlight conditions. Profoxydim's behavior in paddy field conditions is not well understood, and this research aimed to fill that gap, particularly examining the effect of commonly utilized organic amendments such as biochar (BC) on its degradation. Results indicated that profoxydim degrades rapidly, with a half-life of 2.4 ± 0.3 h in paddy water and 1.03 ± 0.1 h in paddy soil. However, when BC was introduced, the degradation slowed significantly, extending the half-lives to 3.1 ± 0.2 h in water and 3.07 ± 0.5 h in soil. The study identified five degradation products (DPs) using TOF mass accuracy measurements and MS/MS spectra fragmentation. Two of these DPs were found to be more stable than profoxydim itself. Additionally, the research proposed a novel photodegradation pathway, highlighting processes such as homolytic C-N bond cleavage, photoisomerization, and photoinduced oxidation. The study's findings contribute new insights into the environmental fate of profoxydim, offering a deeper understanding of its transformation in rice paddy fields and aiding in the assessment of potential risks associated with its residues in agricultural environments.

Global meta-analysis and machine learning reveal the critical role of soil properties in influencing biochar-pesticide interactions

Biochar application in soils is increasingly advocated globally for its dual benefits in enhancing agricultural productivity and sequestering carbon. However, lingering concerns persist regarding its environmental impact, particularly concerning its interactions with pesticide residues in soil. Previous research has fragmentarily indicated elevated pesticide residues and prolonged persistence in biochar-amended soil, suggesting a potential adverse consequence of biochar application on pesticide degradation. Yet, conclusive evidence and conditions for this phenomenon remain elusive. To address this gap, we conducted a comprehensive assessment using meta-analysis and machine learning techniques, synthesizing data from 58 studies comprising 386 observations worldwide. Contrary to initial concerns, our findings revealed no definitive increase in pesticide concentrations in soil following biochar application. Moreover, a significant reduction of 66 % in pesticide concentrations within soil organisms, such as plants and earthworms, was observed. The quantitative analysis identified soil organic matter content as a key factor influencing biochar-pesticide interactions, suggesting that applying biochar to soils rich in organic matter is less likely to increase pesticide persistence. This study provides a critical assessment of the environmental fate of pesticides under biochar application, offering valuable guidance for the optimal utilization of both pesticides and biochar in sustainable agricultural practices.

The adsorption mechanism and optimal dosage of walnut shell biochar for chloramphenicol

Biochar derived from biomass pyrolysis has proven to be an excellent material for pesticide adsorption and can be used as soil amendment for pesticide non-point pollution. However, the adsorption and desorption mechanisms for certain biochar and pesticide are still unclear. In this study, we investigated the properties of biochar derived from walnut (Juglans regia L.) shell (WSB), and used batch equilibrium method to investigate the adsorption and desorption behavior for chlorantraniliprole (CAP). The physical-chemical analysis showed that there were mainly lignin charcoal of alkyl carbon, methoxyl carbon, aromatic carbon, and carboayl carbon as the primary carbon compounds of WSB. The π - π electron donor acceptor interaction, electrostatic interaction, and hydrogen bond were the primary adsorption mechanisms of the WSB adsorption. Batch equilibrium study under 298 K showed that WSB application in the soil significantly improved the adsorption ability for CAP, and the adsorption behavior was a mono-layer adsorption process as Langmuir model fitted the adsorption isotherm data better than the Freundlich model. While Freundlich model analysis showed that WSB addition to the soil changed the isothermal adsorption line from the S style to the L style. The spontaneous degree reaction of sorbents from strong to weak was in the following order: 5%-WSB >7%-WSB >10%-WSB >1%-WSB >3%-WSB > soil > WSB, and the maximum application effect was achieved at 5 % (m/m) WSB dosage mixed with the soil. Therefore, we considered that WSB addition in soil increased its CAP adsorption capacity, and 5 % (m/m) WSB application was the best choice for CAP pollution control. These data will contribute to the adsorption mechanism and the optimal use dosage of WSB for CAP pollution control.

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.

Recent approaches and advancement in biochar-based environmental sustainability: Is biochar fulfilling the sustainable development goals?

This review highlights the application of biochar (BC) for attaining different SDGs (SDG 6: clean water and sanitation, SDG 7: affordable and clean energy, SDG 13: climate action, and SDG 15: life on land). These goals coincide with the various existing environmental problems including wastewater treatment, soil amendment, greenhouse gas remediation, and bioenergy generation. So, the review encompasses the various mechanisms involved in the BC-assisted treatment and reclamation of water, pollutant immobilization and enhancing soil properties, reduction of greenhouse gas emission during the wastewater treatment process and soil amendment mechanisms, bioenergy generation through various electrode material, biodiesel production, and many more. The review also explains the various drawbacks and limitations of BC application to the available environmental issues. Conclusively, it was apprehended that BC is an appropriate material for several environmental applications. More research interventions are further required to analyze the applicability of different BC materials for attaining other available SDGs.

Enhancing herbicide adsorption in low-fertility soil using sugarcane biochar: Insights from Imazapic dynamics

Biochar amendment has emerged as a potential solution for preventing, remediating, and mitigating agricultural compound pollution. This groundbreaking technique not only improves crucial soil properties like porosity, water retention capacity, cation exchange capacity, and pH, but also intricately impacts the interaction and retention mechanisms of polluting molecules. In this study, we investigate the dynamic of the herbicide Imazapic when subjected to applying pyrolyzed biochars, specifically at temperatures of 300 and 500 °C, within the context of a low-fertility soil characterized as dystrophic Yellow Ultisol (YUd) in a sugarcane cultivation area in Igarassu-PE, Brazil. The biochars were produced from sugarcane bagasse by pyrolysis process in a muffle furnace. In laboratory conditions, with saturated soil columns under steady-state, analyses of the mechanisms involved in interaction and transport and determining hydrodispersive parameters for Imazapic were performed by the two-site nonequilibrium transport model using the CXTFIT 2.0 program. Samples of YUd soil amended with biochar pyrolyzed at 300 °C presented a negligible interaction with Imazapic. However, adding biochar pyrolyzed at 500 °C (BC500) to the soil samples enhanced the adsorption coefficient and improved the interaction with Imazapic. This research points out that biochar produced from agricultural waste biomass, such as sugarcane bagasse specifically pyrolyzed at 500 °C, offers a potential means to adsorb herbicides, reducing their leaching to deeper layers of the amended soils and the risk of groundwater contamination and potential environmental negative impacts.

Impact of biochar on the degradation rates of three pesticides by vegetables and its effects on soil bacterial communities under greenhouse conditions

A 28 days pesticide degradation experiment was conducted for broccoli (Brassica oleracea L. var. italica Planch) and pakchoi (Brassica chinensis L.) with three pesticides (chlorantraniliprole (CAP), haloxyfop-etotyl (HPM), and indoxacarb (IXB)) to explore the effects of biochar on pesticide environmental fate and rhizosphere soil diversity. Rice straw biochar (RB) was applied to soil at a 25.00 t ha-1 dosage under greenhouse conditions, and its effects on the degradation of three pesticides in vegetables and in soil were investigated individually. Overall, RB application effectively facilitated CAP and HPM degradation in broccoli by 13.51-39.42% and in broccoli soil by 23.80-74.10%, respectively. RB application slowed the degradation of CAP, HPM and IXB in pakchoi by 0.00-57.17% and slowed the degradation of CAP in pakchoi by 37.32-43.40%. The results showed that the effect of RB application on pesticide degradation in crops and soil was related to biochar properties, pesticide solubility, plant growth status, and soil characteristics. Rhizosphere soil microorganisms were also investigated, and the results showed that biochar application may be valuable for altering bacterial richness and diversity. The effect of biochar application on pesticide residues in crops and soil was influenced by the vegetable variety first, and the second was pesticide characteristics. RB applied to soil at a 25.00 t ha-1 dosage under greenhouse conditions is recommended for broccoli production to ensure food safety. Our results suggested that biochar application in soil could reduce pesticide non-point source pollution, especially for highly soluble pesticides, and could affect soil microorganisms.

Enhancing soil health, microbial count, and hydrophilic methomyl and hydrophobic lambda-cyhalothrin remediation with biochar and nano-biochar

Pesticide contamination and soil degradation present significant challenges in agricultural ecosystems, driving extensive exploration of biochar (BC) and nano-biochar (NBC) as potential solutions. This study examines their effects on soil properties, microbial communities, and the fate of two key pesticides: the hydrophilic methomyl (MET) and the hydrophobic lambda-cyhalothrin (LCT), at different concentrations (1%, 3%, and 5% w w-1) in agricultural soil. Through a carefully designed seven-week black bean pot experiment, the results indicated that the addition of BC/NBC significantly influenced soil dynamics. Soil pH and moisture content (MC) notably increased, accompanied by a general rise in soil organic carbon (SOC) content. However, in BC5/NBC5 treatments, SOC declined after the 2nd or 3rd week. Microbial populations, including total plate count (TPC), phosphate-solubilizing bacteria (PSB), and nitrogen-fixing bacteria (NFB), showed dynamic responses to BC/NBC applications. BC1/NBC1 and BC3/NBC3 applications led to a significant increase in microbial populations, whereas BC5/NBC5 treatments experienced a decline after the initial surge. Furthermore, the removal efficiency of both MET and LCT increased with higher BC/NBC concentrations, with NBC demonstrating greater efficacy than BC. Degradation kinetics, modeled by a first-order equation, revealed that MET degraded faster than LCT. These findings underscore the profound impact of BC/NBC on pesticide dynamics and microbial communities, highlighting their potential to transform sustainable agricultural practices.

Adsorption of sulfamethoxazole and ethofumesate in biochar- and organoclay-amended soil: Changes with adsorbent aging in the laboratory and in the field

Biochars and organoclays have been proposed as efficient adsorbents to reduce the mobility of agrochemicals in soils. However, following their application to soils, these adsorbents undergo changes in their physicochemical properties over time due to their interaction with soil components. In this study, the adsorption capacity of a commercial biochar and a commercial organoclay for the antibiotic sulfamethoxazole (SFMX) and the pesticide ethofumesate (ETFM) was evaluated over aging periods of 3 months in the laboratory and 1 year in the field, subsequent to their application to a Mediterranean soil. The results showed that the adsorption of SFMX and ETFM in the soil amended with the adsorbents was greater than in the unamended soil, but for both chemicals, adsorption decreased with aging of the adsorbents in the soil. Characterization of the adsorbents before and after aging revealed physical blocking of adsorption sites by soil components. The loss of adsorption capacity of the adsorbents upon aging led to higher leaching of SFMX and ETFM in the soil containing field-aged adsorbents, although leaching remained lower than in unamended soil. Our findings reveal that, under the Mediterranean environment studied, the efficacy of the studied materials as adsorbents is maintained to a considerable extent for at least one year after their field application, which would have positive implications in their use for attenuating the dispersion of agricultural contaminants in the environment.

Engineered lignocellulosic based biochar to remove endocrine-disrupting chemicals: Assessment of binding mechanism

The safety and health of aquatic organisms and humans are threatened by the increasing presence of pollutants in the environment. Endocrine disrupting chemicals are common pollutants which affect the function of endocrine and causes adverse effects on human health. These chemicals can disrupt metabolic processes by interacting with hormone receptors upon consumptions by humans or aquatic species. Several studies have reported the presence of endocrine disrupting chemicals in waterbodies, food, air and soil. These chemicals are associated with increasing occurrence of obesity, metabolic disorders, reproductive abnormalities, autism, cancer, epigenetic variation and cardiovascular risk. Conventional treatment processes are expensive, not environment friendly and unable to achieve complete removal of these harmful chemicals. In recent years, biochar from different sources has gained a considerable interest due to their adsorption efficiency with porous structure and large surface areas. biochar derived from lignocellulosic biomass are widely used as sustainable catalysts in soil remediation, carbon sequestration, removal of organic and inorganic pollutants and wastewater treatment. This review conceptualizes the production techniques of biochar from lignocellulosic biomass and explores the functionalization and interaction of biochar with endocrine-disrupting chemicals. This review also identifies the further needs of research. Overall, the environmental and health risks of endocrine-disrupting chemicals can be dealt with by biochar produced from lignocellulosic biomass as a sustainable and prominent approach.

Fabrication of engineered biochar for remediation of toxic contaminants in soil matrices and soil valorization

Biochar has emerged as an efficacious green material for remediation of a wide spectrum of environmental pollutants. Biochar has excellent characteristics and can be used to reduce the bioavailability and leachability of emerging pollutants in soil through adsorption and other physico-chemical reactions. This paper systematically reviewed previous researches on application of biochar/engineered biochar for removal of soil contaminants, and underlying adsorption mechanism. Engineered biochar are derivatives of pristine biochar that are modified by various physico-chemical and biological procedures to improve their adsorption capacities for contaminants. This review will promote the possibility to expand the application of biochar for restoration of degraded lands in the industrial area or saline soil, and further increase the useable area. This review shows that application of biochar is a win-win strategy for recycling and utilization of waste biomass and environmental remediation. Application of biochar for remediation of contaminated soils may provide a new solution to the problem of soil pollution. However, these studies were performed mainly in a laboratory or a small scale, hence, further investigations are required to fill the research gaps and to check real-time applicability of engineered biochar on the industrial contaminated sites for its large-scale application.

Exploring the influence of invasive weed biochar on the sorption and dissipation dynamics of imazethapyr in sandy loam soil

The management of invasive weeds on both arable and non-arable land is a vast challenge. Converting these invasive weeds into biochar and using them to control the fate of herbicides in soil could be an effective strategy within the concept of turning waste into a wealth product. In this study, the fate of imazethapyr (IMZ), a commonly used herbicide in various crops, was investigated by introducing such weeds as biochar, i.e., Parthenium hysterophorus (PB) and Lantana camara (LB) in sandy loam soil. In terms of kinetics, the pseudo-second order (PSO) model provided the best fit for both biochar-mixed soils. More IMZ was sorbed onto LB-mixed soil compared to PB-mixed soil. When compared to the control (no biochar), both PB and LB biochars (at concentrations of 0.2% and 0.5%) increased IMZ adsorption, although the extent of this effect varied depending on the dosage and type of biochar. The Freundlich adsorption isotherm provided a satisfactory explanation for IMZ adsorption in soil/soil mixed with biochar, with the adsorption process exhibiting high nonlinearity. The values of Gibb's free energy change (ΔG) were negative for both adsorption and desorption in soil/soil mixed with biochar, indicating that sorption was exothermic and spontaneous. Both types of biochar significantly affect IMZ dissipation, with higher degradation observed in LB-amended soil compared to PB-amended soil. Hence, the findings suggest that the preparation of biochar from invasive weeds and its utilization for managing the fate of herbicides can effectively reduce the residual toxicity of IMZ in treated agroecosystems in tropical and subtropical regions.

Removal of sulfonylurea herbicides with g-C3N4-based photocatalysts: A review

The accumulation of agricultural chemicals in the environment has become a global concern, of which sulfonylurea herbicides (SUHs) constitute a significant category. Solar-driven photocatalysis is favored for removing organic pollutants due to its high efficiency and environmental friendliness. Graphite carbon nitride (g-C3N4)-based materials with superior catalytic activities and physicochemical stabilities are promising photocatalysts. This review describes the g-C3N4-based materials and their uses in the photocatalytic degradation of SUHs or other organic pollutants with similar structures. First, the fundamentals of g-C3N4-based materials and photocatalytic SUHs degradation are discussed to provide an in-depth understanding of the mechanism for the photocatalytic activity. The ability of different g-C3N4-based materials to photocatalytically degrade SUH-like structures is then discussed and summarized based on different modification strategies (morphology modulation, elemental doping, defect engineering, and heterojunction formations). Meanwhile, the effects of different environmental factors on the photocatalytic performance of g-C3N4-based materials are described. Finally, the major challenges and opportunities of g-C3N4-based materials for the photocatalytic degradation of SUHs are proposed. It is hoped that this review will show the feasibility of photocatalytic degradation of SUHs with g-C3N4-based materials.

Application of mid-infrared spectroscopy to the prediction and specification of pesticide sorption: A promising and cost-effective tool

The cocktail of pesticides sprayed to protect crops generates a miscellaneous and generalized contamination of water bodies. Sorption, especially on soils, regulates the spreading and persistence of these contaminants. Fine resolution sorption data and knowledge of its drivers are needed to manage this contamination. The aim of this study is to investigate the potential of Mid-Infrared spectroscopy (MIR) to predict and specify the adsorption and desorption of a diversity of pesticides. We constituted a set of 37 soils from French mainland and West Indies covering large ranges of texture, organic carbon, minerals and pH. We measured the adsorption and desorption coefficients of glyphosate, 2,4-dichlorophenoxyacetic acid (2,4-D) and difenoconazole and acquired MIR Lab spectra for these soils. We developed Partial Least Square Regression (PLSR) models for the prediction of the sorption coefficients from the MIR spectra. We further identified the most influencing spectral bands and related these to putative organic and mineral functional groups. The prediction performance of the PLSR models was generally high for the adsorption coefficients Kdads (0.4 < R2 < 0.9 & RPIQ >1.8). It was contrasted for the desorption coefficients and related to the magnitude of the desorption hysteresis. The most significant spectral bands in the PLSR differ according to the pesticides indicating contrasted interactions with mineral and organic functional groups. Glyphosate interacts primarily with polar mineral groups (OH) and difenoconazole with hydrophobic organic groups (CH2, CC, COO-, C-O, C-O-C). 2,4-D has both positive and negative interactions with these groups. Finally, this work suggests that MIR combined with PLSR is a promising and cost-effective tool. It allows both the prediction of adsorption and desorption parameters and the specification of these mechanisms for a diversity of pesticides including polar active ingredients.

Mechanisms of adsorption and functionalization of biochar for pesticides: A review

Agricultural production relies heavily on pesticides. However, factors like inefficient application, pesticide resistance, and environmental conditions reduce their effective utilization in agriculture. Subsequently, pesticides transfer into the soil, adversely affecting its physicochemical properties, microbial populations, and enzyme activities. Different pesticides interacting can lead to combined toxicity, posing risks to non-target organisms, biodiversity, and organism-environment interactions. Pesticide exposure may cause both acute and chronic effects on human health. Biochar, with its high specific surface area and porosity, offers numerous adsorption sites. Its stability, eco-friendliness, and superior adsorption capabilities render it an excellent choice. As a versatile material, biochar finds use in agriculture, environmental management, industry, energy, and medicine. Added to soil, biochar helps absorb or degrade pesticides in contaminated areas, enhancing soil microbial activity. Current research primarily focuses on biochar produced via direct pyrolysis for pesticide adsorption. Studies on functionalized biochar for this purpose are relatively scarce. This review examines biochar's pesticide absorption properties, its characteristics, formation mechanisms, environmental impact, and delves into adsorption mechanisms, functionalization methods, and their prospects and limitations.

Risk assessment of pesticide compounds: IPT and TCZ cause hepatotoxicity, activate stress pathway and affect the composition of intestinal flora in red swamp crayfish (Procambarusclarkii)

Isoprothiolane (IPT) and tricyclazole (TCZ) are widely used in rice farming and recently in combined rice-fish farming. However, co-cultured animals are affected by these pesticides. To investigate the organismal effects and toxicity of pesticides, crayfish were exposed to 0, 1, 10, or 100 ppt TCZ or IPT for 7 days. Pesticide bioaccumulation, survival rate, metabolic parameters, structure of intestinal flora, and antioxidant-, apoptosis-, and HSP-related gene expression were determined. Pesticide exposure caused bioaccumulation of IPT or TCZ in the hepatopancreas and muscles of crayfish; however, IPT bioaccumulation was higher than that of TCZ. Both groups showed significant changes in hepatopancreatic serum biochemical parameters. Mitochondrial damage and chromosomal agglutination were observed in hepatopancreatic cells exposed to 100 ppt IPT or TCZ. IPT induced more significant changes in serum biochemical parameters than TCZ. The results of intestinal flora showed that Vibro, Flavobacterium, Anaerorhabdus and Shewanella may have potential for use as a bacterial marker of TCZ and IPT. Antioxidant-, apoptosis-, and HSP-related gene expression was disrupted by pesticide exposure, and was more seriously affected by IPT. The results suggest that IPT or TCZ induce hepatopancreatic cell toxicity; however, IPT or TCZ content in dietary crayfish exposed to 1 ppt was below the food safety residue standard. The data indicated that IPT exposure may be more toxic than TCZ exposure in hepatopancreas and intestines and toxicity of organism are alleviated by activating the pathway of stress-response, providing an understanding of pesticide compounds in rice-fish farming and food safety.

Alginate-encapsulated biochar as an effective soil ameliorant for reducing Pb phytoavailability to lettuce (Lactuca sativa L.)

The alginate-biochar formulation for metal removal from aquatic environments has been widely tried but its use for lowering phytoavailability of metals in the soil-crop continuum is limited. Biochar has been increasingly used as a soil amendment due to its potential for soil carbon sequestration and sorption capacity. Handling of powdery biochar as a soil top-dressing material is, however, cumbersome and vulnerable to loss by water and wind. In this experiment, biochar powder, which was pyrolyzed from oak trees, was encapsulated into beads with alginate, which is a naturally occurring polysaccharide found in brown algae. Both batch and pot experiments were conducted to examine the effects of the alginate-encapsulated biochar beads (BB), as compared to its original biochar powdery form (BP), on the Pb adsorption capacity and phytoavailability of soil Pb to lettuce (Lactuca sativa L.). The BB treatment improved reactivity about six times due to a higher surface area (287 m2 g-1) and five times due to a higher cation exchange capacity (50 cmolc kg-1) as compared to the BP treatment. The maximum sorption capacity of Pb was increased to 152 from 81 mg g-1 because of surface chemosorption. Adsorption of Pb onto BB followed multiple first-order kinetics and comprised fast and slow steps. More than 60% of the Pb was adsorbed in the fast step, i.e., within 3 h. Also, the BB treatment, up to the 5% level (w/w), increased soil pH from 5.4 to 6.5 and lowered the phytoavailable fraction of Pb in soil from 5.7 to 0.3 mg kg-1. The Pb concentrations in lettuce cultivated at 5% for the BP and BB treatments were similar but 63 and 66% lower, respectively, than those of the control soil. The results showed that the encapsulation of biochar with alginate enhanced adsorption by the biochar.

Assessing the effect of organic amendments on the degradation of profoxydim in paddy soils: Kinetic modeling and identification of degradation products

The fate and behavior of herbicides can be altered in an unpredictable way when organic amendments are added to soil as a beneficial management tool. The objective of this work was to investigate the effect exerted by the addition of two different organic amendments (alperujo compost and biochar) to soil in the degradation of one of the most relevant new generation rice herbicides, profoxydim. In unamended soils, the degradation of profoxydim was quite fast and was governed by both chemical (DT50steril soil = from 1.52 to 9.21 days) and microbial (DT50nonsterile soil = from 0.47 to 0.53 days) processes. Alperujo- and biochar-amended soils significantly increased the persistence of the herbicide in both soils, especially in the presence of biochar, due to the high capacity absorption of this amendment, increasing DT90 from 1.92 to 3.54 days for DT90unamended to 41.02-48.41 days for DT90biochar amended. Different kinetics models applied to fit the observed dissipation datasets showed that a HS biphasic model fits well with the dissipation of profoxydim in amended and unamended soils. For the first time, five degradation products (DPs) were identified by HPLC-QTOF-MS/MS in soil and a degradation pathway was described. Main DP was generated via oxidation of the sulfur atom to give rise to the corresponding sulfoxide derivative, with this DP being more persistent than the active substance. These outcomes can be very useful for the assessment of the environmental risk associated with the use of profoxydim in rice crops and the application of organic amendments as potential measures for minimizing the risk of contamination of natural water resources.

Quantification of the effect of biochar application on heavy metals in paddy systems: Impact, mechanisms and future prospects

Biochar (BC) has shown great potential in remediating heavy metal(loid)s (HMs) contamination in paddy fields. Variation in feedstock sources, pyrolysis temperatures, modification methods, and application rates of BC can result in great changes in its effects on HM bioavailability and bioaccumulation in soil-rice systems and remediation mechanisms. Meanwhile, there is a lack of application guidelines for BC with specific properties and application rates when targeting rice fields contaminated with certain HMs. To elucidate this topic, this review focuses on i) the effects of feedstock type, pyrolysis temperature, and modification method on the properties of BC; ii) the changes in bioavailability and bioaccumulation of HMs in soil-rice systems applying BC with different feedstocks, pyrolysis temperatures, modification methods, and application rates; and iii) exploration of potential remediation mechanisms for applying BC to reduce the mobility and bioaccumulation of HMs in rice field systems. In general, the application of Fe/Mn modified organic waste (OW) derived BC for mid-temperature pyrolysis is still a well-optimized choice for the remediation of HM contamination in rice fields. From the viewpoint of remediation efficiency, the application rate of BC should be appropriately increased to immobilize Cd, Pb, and Cu in rice paddies, while the application rate of BC for immobilizing As should be <2.0 % (w/w). The mechanism of remediation of HM-contaminated rice fields by applying BC is mainly the direct adsorption of HMs by BC in soil pore water and the mediation of soil microenvironmental changes. In addition, the application of Fe/Mn modified BC induced the formation of iron plaque (IP) on the root surface of rice, which reduced the uptake of HM by the plant. Finally, this paper describes the prospects and challenges for the extension of various BCs for the remediation of HM contamination in paddy fields and makes some suggestions for future development.

Enantioselective fate and risk assessment of chiral fungicide pydiflumetofen in rice-fish and wheat farming systems

Fungicides have been widely used for reducing the losses caused by plant diseases. Rice and wheat are the most basic food crops, and the potential risks after applying fungicides are worthy of attention. Especially rice-fish farming system is an ecological symbiosis system that is beneficial to both environmental and ecological protection. However, the application of pesticides will stress the ecosystem, and the pesticide residues in rice and fish would be transmitted along the food chain, which is harmful to human health. Here, the enantioselective behaviors of chiral pydiflumetofen in rice-fish and wheat farming systems were clarified. In the rice-fish farming system, pydiflumetofen enantiomers were preferentially attached to the plants, entering the paddy water and settling into the paddy soil, and then accumulating and dissipating in the fish. With the growth of rice, it was transported to rice fruits. The wheat farming system was similar. Enantioselective dissipation occurred in carp (Cyprinus carpio), brown rice and wheat soil, and S-(+)-pydiflumetofen was preferentially dissipated. In other words, R-(-)-pydiflumetofen showed higher concentrations, especially in carp, which meant R-(-)-pydiflumetofen was more easily accumulated in the environment, and posed a greater potential risk to the farming system. The pydiflumetofen residues in brown rice and wheat were lower than MRLs from the EFSA (0.02 mg/kg) and eCFR (0.3 mg/kg), respectively. What deserves attention is that the MRL of pydiflumetofen in fish is not clear. Meanwhile, pydiflumetofen in paddy soil and wheat soil had a persistent residual effect, and the risks could not be ignored. Combined with the previous research, developing S-(+)-pydiflumetofen products will help to reduce the dosage and reduce the risks to environment and people. This study evaluated the environmental fate and risk of chiral pydiflumetofen from the perspective of farming system, and would provide data support for its rational use and risk assessment.

Field assessment of coconut-based activated carbon systems for the treatment of herbicide contamination

Once released into the environment, herbicides can move through soil or surface water to streams and groundwater. Filters containing adsorbent media placed in fields may be an effective solution to herbicide loss in the environment. However, to date, no study has investigated the use of adsorbent materials in intervention systems at field-scale, nor has any study investigated their optimal configuration. Therefore, the aim of this paper was to examine the efficacy of low-cost, coconut-based activated carbon (CAC) intervention systems, placed in streams and tributaries, for herbicide removal. Two configurations of interventions were investigated in two agricultural catchments and one urban area in Ireland: (1) filter bags and (2) filter bags fitted into polyethylene pipes. Herbicide sampling was conducted using Chemcatcher® passive sampling devices in order to identify trends in herbicide exceedances at the sites, and to quantifiably assess, compare, and contrast the efficiency of the two intervention configurations. While the Chemcatcher® passive sampling devices are capable of analysing eighteen different acid herbicides, only six different acid herbicides (2,4-D, clopyralid, fluroxypyr, MCPA, mecoprop and triclopyr) were ever detected within the three catchment areas, which were also the only acid herbicides used therein. The CAC was capable of complete herbicide removal, when the water flow was slow (0.5-1 m3 s-1), and the interventions spanned the width and depth of the waterway. Overall, the reduction in herbicide concentrations was better for the filter pipes than for the filter bags, with a 48% reduction in detections and a 37% reduction in exceedances across all the sampling sites for the filter pipe interventions compared to a 13% reduction in the number of detections and a 24% reduction in exceedances across all sampling sites for the filter bag interventions (p < 0.05). This study demonstrates, for the first time, that CAC may be an effective in situ remediation strategy to manage herbicide exceedances close to the source, thereby reducing the impact on environmental and public health.

A critical review of sustainable pesticide remediation in contaminated sites: Research challenges and mechanistic insights

Incidental pesticide application on farmlands can result in contamination of off-target biota, soil, groundwater, and surrounding ecosystems. To manage these pesticide contaminations sustainably, it is important to utilize advanced approaches to pesticide decontamination. This review assesses various innovative strategies applied for remediating pesticide-contaminated sites, including physical, chemical, biological, and nanoremediation. Integrated remediation approaches appear to be more effective than singular technologies. Bioremediation and chemical remediation are considered suitable and sustainable strategies for decontaminating contaminated soils. Furthermore, this study highlights key mechanisms underlying advanced pesticide remediation that have not been systematically studied. The transformation of applied pesticides into metabolites through various biotic and chemical triggering factors is well documented. Ex-situ and in-situ technologies are the two main categories employed for pesticide remediation. However, when selecting a remediation technique, it is important to consider factors such as application sites, cost-effectiveness, and specific purpose. In this review, the sustainability of existing pesticide remediation strategies is thoroughly analyzed as a pioneering effort. Additionally, the study summarizes research uncertainties and technical challenges associated with different remediation approaches. Lastly, specific recommendations and policy advocacy are suggested to enhance contemporary remediation approaches for cleaning up pesticide-contaminated sites.

An enantioselective study of the behavior of the herbicide ethofumesate in agricultural soils: Impact of the addition of organoclays and biochar

Chiral pesticides that are still commercialized and incorporated into the environment as racemic mixtures of enantiomers require evaluation of the enantioselectivity of their biological activity and environmental fate processes for a better prediction of their field efficacy and environmental risks. In this work, we successfully separated the enantiomers of the chiral herbicide ethofumesate (ETFM), determined their absolute configuration, and characterized their herbicidal activity as well as their adsorption, degradation, enantiomerization, and leaching in Mediterranean agricultural soils. While the herbicidal activity of R-ethofumesate to the sensitive species Portulaca grandiflora was greater than that of S-ethofumesate, the adsorption, degradation, and leaching of the herbicide showed negligible enantioselectivity and enantiomer interconversion did not occur in soils. The adsorption of both enantiomers showed a positive correlation with the soil organic carbon content (r = 0.856, P = 0.015), and their degradation in soils occurred slowly (DT50 > 60 days) and at similar rates independent of their application as individual enantiomers or as a racemic mixture of enantiomers. The addition of three highly adsorptive materials to a scarcely adsorptive soil increased the adsorption of the enantiomers of ETFM and delayed their degradation without affecting the non-enantioselective character of the processes. As a result of their high adsorption capacity, the materials were highly effective in reducing the leaching of both enantiomers of ETFM through soil columns. The results of this work indicate that the application of single-enantiomer ETFM formulations, based on a higher herbicidal activity or a lower toxicity to non-target organisms of the formulated enantiomer, would reduce considerable exposure risks associated with incorporating into the environment the less favorable enantiomer, as this would show long persistence and high leaching potential in soils similar to its optical isomer.

Effects of field-aging on the impact of biochar on herbicide fate and microbial community structure in the soil environment

Biochar can enhance organic carbon storage and mitigate the adverse effects of pesticides in the soil. However, the mechanisms by which field-aging affects the impacts of biochar on herbicide behavior and the composition of microbial communities in the soil remain unclear. This study aimed to investigate the influences of aged and fresh biochar on herbicide behavior and microbial community structure in the soil. Herein, with 14C-labeled technology, aged treatment (soil amended with field-aged biochar), fresh treatment (soil amended with fresh biochar), and control (soil without biochar) were installed to evaluate their treatment capacities. The results showed that the average leaching out and mineralization of simazine in the aged treatment were significantly higher by 4.8% and 1.66% (P < 0.05) compared with the fresh treatment. Relative to the control, the pesticide was significantly adsorbed (P < 0.05) in the aged treatment. The abundance of arbuscular mycorrhizal fungi (AMF) significantly increased by 1.03 and 1.16-fold, whereas fungi increased dramatically by 1.02-fold and decreased by 1.21-fold in the aged and fresh treatments, respectively (P < 0.05). In addition, eukaryotes were effectively reduced by 1.02 and 1.14-fold in these treatments, respectively (P < 0.05). This study suggests that field aging can undermine the impacts of biochar on pesticides and modify the microbial community structure in the soil environment.

A critical review of sustainable application of biochar for green remediation: Research uncertainty and future directions

Biochar, a carbon-rich material produced from the pyrolysis of organic biomass, has gained significant attention as a potential solution for sustainable green remediation practices. Several studies analyze biomass-derived biochar techniques and environmental applications, but comprehensive assessments of biochar limitations, uncertainty, and future research directions still need to be improved. This critical review aims to present a comprehensive analysis of biochar's efficacy in environmental applications, including soil, water, and air, by sequentially addressing its preparation, application, and associated challenges. The review begins by delving into the diverse methods of biochar production, highlighting their influence on physical and chemical properties. This review explores the diverse applications of biochar in remediating contaminated soil, water, and air while emphasizing its sustainability and eco-friendly characteristics. The focus is on incorporating biochar as a remediation technique for pollutant removal, sequestration, and soil improvement. The review highlights the promising results obtained from laboratory-scale experiments, field trials, and case studies, showcasing the effectiveness of biochar in mitigating contaminants and restoring ecosystems. The environmental benefits and challenges of biochar production, characterization, and application techniques are critically discussed. The potential synergistic effects of combining biochar with other remediation methods are also explored to enhance its efficacy. A rigorous analysis of the benefits and drawbacks of biochar for diverse environmental applications in terms of technical, environmental, economic, and social issues is required to support the commercialization of biochar for large-scale uses. Finally, future research directions and recommendations are presented to facilitate the development and implementation of biochar-based, sustainable green remediation strategies.

Degradation of Pesticide Residues in Water, Soil, and Food Products via Cold Plasma Technology

Water, soil, and food products contain pesticide residues. These residues result from excessive pesticides use, motivated by the fact that agricultural productivity can be increased by the use of these pesticides. The accumulation of these residues in the body can cause health problems, leading to food safety concerns. Cold plasma technology has been successfully employed in various applications, such as seed germination, bacterial inactivation, wound disinfection, surface sterilization, and pesticide degradation. In recent years, researchers have increasingly explored the effectiveness of cold plasma technology in the degradation of pesticide residues. Most studies have shown promising outcomes, encouraging further research and scaling-up for commercialization. This review summarizes the use of cold plasma as an emerging technology for pesticide degradation in terms of the plasma system and configuration. It also outlines the key findings in this area. The most frequently adopted plasma systems for each application are identified, and the mechanisms underlying pesticide degradation using cold plasma technology are discussed. The possible factors influencing pesticide degradation efficiency, challenges in research, and future trends are also discussed. This review demonstrates that despite the nascent nature of the technology, the use of cold plasma shows considerable potential in regards to pesticide residue degradation, particularly in food applications.

Environmental fate and metabolic transformation of two non-ionic pesticides in soil: Effect of biochar, moisture, and soil sterilization

Soil moisture, organic matter, and soil microbes are the key considering factors that control the persistence, degradation, and transformation of applied pesticides under varied soil conditions. In this study, underlying influence of these factors was assessed through the fates and metabolic transformation of two non-ionic pesticides (e.g., Phorate and Terbufos) in soils. Concisely, two distinct experiments including a customized batch equilibrium (sorption study), and a lab incubation trial (degradation study) were performed, following the OECD guidelines. As per study findings, biochar (BC) amendment was found to be the most influential factors during sorption study, particularly, 1% BC amendment contributed to achieve the best results. In addition, the non-linearity of sorption isotherm (1/n < 1.0) was revealed through Freundlich isotherm, indicating the strong adsorption of studied pesticides onto the soils. On the other hand, during degradation study, soil moisture initiates the enhanced degradation of parent pesticides and subsequent metabolism. In the presence of 40% water holding capacity (WHC), 1% BC amendment enhances the metabolic transformation, while H2O2 treatment could hinder the process. Additionally, the half-life degradation (t1/2) of phorate and terbufos was controlled by biochar amendment, moisture, and soil sterilization, respectively. Finally, BC can accelerate the metabolic transformation, whereas, phorate underwent a metabolic change into sulfoxide and sulfone while terbufos turned into solely sulfoxide. This pioneering study gathered crucial data for understanding the persistence and metabolic transition of non-ionic pesticides in soils and their patterns of degradation.

When biochar is involved in rhizosphere dissipation and plant absorption of pesticides: A meta-analysis

Clarifying the influences of biochar input on the rhizosphere dissipation and plant absorption of pesticides is a crucial prerequisite for utilizing biochar in the restoration of pesticide-contaminated soils. Nevertheless, the application of biochar to pesticide-contaminated soils does not always achieve consistent results on the rhizosphere dissipation and plant absorption of pesticides. Under the new situation of vigorously promoting the application of biochar in soil management and carbon sequestration, a timely review is needed to further understand the key factors affecting biochar remediation of pesticide-contaminated soil. In this study, a meta-analysis was conducted utilizing variables from three dimensions of biochar, remediation treatment, and pesticide/plant type. The pesticide residues in soil and the pesticide uptake by plant were used as response variables. Biochar with high adsorption capacity can impede the dissipation of pesticides in soil and mitigate their absorption by plants. The specific surface area of biochar and the type of pesticide are critical factors that affect pesticide residues in soil and plant uptake, respectively. Applying biochar with high adsorption capacity, based on specific dosages and soil characteristics, is recommended for the remediation of continuously cultivated soil contaminated with pesticides. This article aims to provide a valuable reference and understanding for the application of biochar-based soil remediation technology and the treatment of pesticide pollution in soil.

28-Homobrassinolide Primed Seed Improved Lead Stress Tolerance in Brassica rapa L. through Modulation of Physio-Biochemical Attributes and Nutrient Uptake

Brassinosteroids (BRs) influence a variety of physiological reactions and alleviate different biotic and abiotic stressors. Turnip seedlings were grown with the goal of further exploring and expanding their function in plants under abiotic stress, particularly under heavy metal toxicity (lead stress). This study's objective was to ascertain the role of applied 28-homobrassinolide (HBL) in reducing lead (Pb) stress in turnip plants. Turnip seeds treated with 1, 5, and 10 µM HBL and were grown-up in Pb-contaminated soil (300 mg kg-1). Lead accumulation reduces biomass, growth attributes, and various biochemical parameters, as well as increasing proline content. Seed germination, root and shoot growth, and gas exchange characteristics were enhanced via HBL treatment. Furthermore, Pb-stressed seedlings had decreased total soluble protein concentrations, photosynthetic pigments, nutrition, and phenol content. Nonetheless, HBL increased chlorophyll a and chlorophyll b levels in plant, resulting in increased photosynthesis. As a result, seeds treated with HBL2 (5 µM L-1) had higher nutritional contents (Mg+2, Zn+2, Na+2, and K+1). HBL2-treated seedlings had higher DPPH and metal tolerance indexes. This led to the conclusion that HBL2 effectively reduced Pb toxicity and improved resistance in lead-contaminated soil.

New and legacy pesticidal persistent organic pollutants in the agricultural region of the Sultanate of Oman

Comprehensive air and surface soil monitoring was conducted for new and legacy organochlorine pesticides (OCPs) to fill the knowledge and data gap on the sources and fate of pesticidal persistent organic pollutants (POPs) in the Sultanate of Oman. DDTs in agricultural soil samples ranged from 0.013 to 95.80 ng/g (mean: 8.4 ± 25.06 ng/g), with a median value of 0.07 ng/g. The highest concentration was observed at Shinas, where intensive agricultural practice is prevalent. The dominance of p,p'-DDT in soil and air reflected technical DDT formulation usage in Oman. Among newly enlisted POPs, pentachlorobenzene had the maximum detection frequency in air (47%) and soil (41%). Over 90% of sites reflected extensive past use of hexachlorobenzene. Major OCP isomers and metabolites showed net volatilisation from the agricultural soil, thereby indicating concurrent emission and re-emission processes from the soil of Oman. However, the cleansing effect of oceanic air mass is the possible reason for relatively lower atmospheric OCP levels from a previous study. Although DDT displayed maximum cancer risk, the level is below the permissible limit. DDT primarily stemmed from obsolete stock and inadequate management practices. Hence, we suggest there is a need for DDT regulation in Oman.

A critical analysis of wastewater use in agriculture and associated health risks in Pakistan

Freshwater shortage and its contamination with various types of pollutants are becoming the most alarming issues worldwide due to impacts on socioeconomic values. Considering an increasing freshwater scarcity, it is imperative for the growers, particularly in semiarid and arid areas, to use wastewater for crop production. Wastewaters generally contain numerous essential inorganic and organic nutrients which are considered necessary for plant metabolism. Besides, this practice provokes various hygienic, ecological and health concerns due to the occurrence of toxic substances such as heavy metals. Pakistan nowadays faces a severe freshwater scarcity. Consequently, untreated wastewater is used routinely in the agriculture sector. In this review, we have highlighted the negative and positive affectivity of wastewater on the chemical characteristics of the soil. This review critically delineates toxic metal accumulation in soil and their possible soil-plant-human transfer. We have also estimated and deliberated possible health hazards linked with the utilization of untreated city waste effluents for the cultivation of food/vegetable crops. Moreover, we carried out a multivariate analysis of data (144 studies of wastewater crop irrigation in Pakistan) to trace out common trends in published data. We have also compared the limit values of toxic metals in irrigation water, soil and plants. Furthermore, some viable solutions and future viewpoints are anticipated taking into account the on-ground situation in Pakistan-such as planning and sanitary matters, remedial/management technologies, awareness among local habitants (especially farmers) and the role of the government, NGOs and pertinent stakeholders. The data are supported by 13 tables and 7 figures.

Pyrolysis Temperature vs. Application Rate of Biochar Amendments: Impacts on Soil Microbiota and Metribuzin Degradation

Biochar-amended soils influence the degradation of herbicides depending on the pyrolysis temperature, application rate, and feedstock used. The objective of this study was to evaluate the influence of sugarcane straw biochar (BC) produced at different pyrolysis temperatures (350 °C, 550 °C, and 750 °C) and application rates in soil (0, 0.1, 0.5, 1, 1.5, 5, and 10% w/w) on metribuzin degradation and soil microbiota. Detection analysis of metribuzin in the soil to find time for 50% and 90% metribuzin degradation (DT₅₀ and DT₉₀) was performed using high-performance liquid chromatography (HPLC). Soil microbiota was analyzed by respiration rate (C-CO₂), microbial biomass carbon (MBC), and metabolic quotient (qCO₂). BC350 °C-amended soil at 10% increased the DT₅₀ of metribuzin from 7.35 days to 17.32 days compared to the unamended soil. Lower application rates (0.1% to 1.5%) of BC550 °C and BC750 °C decreased the DT₅₀ of metribuzin to ~4.05 and ~5.41 days, respectively. BC350 °C-amended soil at high application rates (5% and 10%) provided high C-CO₂, low MBC fixation, and high qCO₂. The addition of low application rates (0.1% to 1.5%) of sugarcane straw biochar produced at high temperatures (BC550 °C and BC750 °C) resulted in increased metribuzin degradation and may influence the residual effect of the herbicide and weed control efficiency.

Wheat straw pyrochar more efficiently decreased enantioselective uptake of dinotefuran by lettuce and dissemination of antibiotic resistance genes than hydrochar in an agricultural soil

Remediation of soils pollution caused by dinotefuran, a chiral pesticide, is indispensable for ensuring human food security. In comparison with pyrochar, the effect of hydrochar on enantioselective fate of dinotefuran, and antibiotic resistance genes (ARGs) profiles in the contaminated soils remain poorly understood. Therefore, wheat straw hydrochar (SHC) and pyrochar (SPC) were prepared at 220 and 500 °C, respectively, to investigate their effects and underlying mechanisms on enantioselective fate of dinotefuran enantiomers and metabolites, and soil ARG abundance in soil-plant ecosystems using a 30-day pot experiment planted with lettuce. SPC showed a greater reduction effect on the accumulation of R- and S-dinotefuran and metabolites in lettuce shoots than SHC. This was mainly resulted from the lowered soil bioavailability of R- and S-dinotefuran due to adsorption/immobilization by chars, together with the char-enhanced pesticide-degrading bacteria resulted from increased soil pH and organic matter content. Both SPC and SHC efficiently reduced ARG levels in soils, owing to lowered abundance of ARG-carrying bacteria and declined horizontal gene transfer induced by decreased dinotefuran bioavailability. The above results provide new insights for optimizing char-based sustainable technologies to mitigate pollution of dinotefuran and spread of ARGs in agroecosystems.

Degradation, adsorption, and bioaccumulation of novel triketone HPPD herbicide tembotrione

Tembotrione is a new triketone HPPD herbicide widely used in Europe, USA, and other areas. However, tembotrione is moderately to highly toxic to algae and daphnia in aquatic ecosystems. In this study, hydrolysis, photolysis, soil degradation, soil adsorption, and bioaccumulation of tembotrione were systematically studied. Hydrolysis experiment revealed that tembotrione was stable in acidic, neutral, and alkaline conditions with half-lives of 231-289 days. The photolysis half-lives of tembotrione were 112-158 days and 76-107 days in pH 4, 7, 9 buffer solutions and on three soils surface, respectively, which demonstrated that tembotrione could be persisted in soil and water. Meanwhile, tembotrione K_foc was 128-196 mL/g, indicating that tembotrione was not easily adsorbed to soil, and the adsorption capacity increased with the decrease in pH. The half-lives of tembotrione in the test soil were 32-48 days, and high organic matter soil is conducive to microbial activity and accelerates the degradation of tembotrione. Moreover, bioaccumulation experiment demonstrated that tembotrione with a BCF of 0.664 to 0.724 had a low risk of exposure to zebrafish. This study is very helpful for the evaluation environmental risk and safe use of tembotrione.

Toxicity sharing model of earthworm intestinal microbiome reveals shared functional genes are more powerful than species in resisting pesticide stress

Earthworm intestinal bacteria and indigenous soil bacteria work closely during various biochemical processes and play a crucial role in maintaining the internal stability of the soil environment. However, the response mechanism of these bacterial communities to external pesticide disturbance is unknown. In this study, soil and earthworm gut contents were metagenomically sequenced after exposure to various concentrations of nitrochlorobenzene (0-1026.7 mg kg^-1). A high degree of similarity was found between the microbial community composition and abundance in the worm gut and soil, both of which decreased significantly (P < 0.05) under elevated pesticide stress. The toxicity sharing model (TSM) showed that the toxicity sharing capacity was 97.4-125.7 % and 100.4-130.2 % for E_genes (genes in the worm gut) and E_met(degradation genes in the worm gut) in the earthworm intestinal microbiome, respectively. This indicated that the earthworm intestinal microbiome assisted in relieving the pesticide toxicity of the indigenous soil microbiome. This study showed that the TSM could quantitatively describe the toxic effect of pesticides on the earthworm intestinal microbiome. It provides a new analytical model for investigating the ecological alliance between earthworm intestinal microbiome and indigenous soil microbiome under pesticide stress while contributing a more profound understanding of the potential to use earthworms to mitigate pesticide pollution in soils and develop earthworm-based soil remediation techniques.

Bacillus-Loaded Biochar as Soil Amendment for Improved Germination of Maize Seeds

Biochar is considered one of the most promising long-term solutions for soil quality improvement, representing an ideal environment for microorganisms' immobilization. Hence there is a possibility to design microbial products formulated using biochar as a solid carrier. The present study was aimed at development and characterization of Bacillus-loaded biochar to be applied as a soil amendment. The producing microorganism Bacillus sp. BioSol021 was evaluated in terms of plant growth promotion traits, indicating significant potential for production of hydrolytic enzymes, indole acetic acid (IAA) and surfactin and positive tests for ammonia and 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase production. Soybean biochar was characterised in terms of physicochemical properties to evaluate its suitability for agricultural applications. The experimental plan for Bacillus sp. BioSol021 immobilisation to biochar included variation of biochar concentration in cultivation broth and adhesion time, while the soil amendment effectiveness was evaluated during maize germination. The best results in terms of maize seed germination and seedling growth promotion were achieved by applying 5% of biochar during the 48 h immobilisation procedure. Germination percentage, root and shoot length and seed vigour index were significantly improved when using Bacillus-biochar soil amendment compared to separate treatments including biochar and Bacillus sp. BioSol021 cultivation broth. The results indicated the synergistic effect of producing microorganism and biochar on maize seed germination and seedling growth promotion, pointing out the promising potential of this proposed multi-beneficial solution for application in agricultural practices.

Performance and mechanisms of biochar-assisted vermicomposting in accelerating di-(2-ethylhexyl) phthalate biodegradation in farmland soil

Biochar and earthworms can accelerate di-(2-ethylhexyl) phthalate (DEHP) degradation in soils. However, little is known regarding the effect of biochar-assisted vermicomposting on soil DEHP degradation and the underlying mechanisms. Therefore, the present study investigated DEHP degradation performance and bacterial community changes in farmland soils using earthworms, biochar, or their combination. Biochar-assisted vermicomposting significantly improved DEHP degradation through initial physical adsorption on biochar and subsequent rapid biodegradation in the soil, earthworm gut, and charosphere. Burkholderiaceae, Pseudomonadaceae, and Flavobacteriaceae were the potential DEHP degraders and were enriched in biochar-assisted vermicomposting. In particularly, Burkholderiaceae and Sphingomonadaceae were enriched in the earthworm gut and charosphere, possibly explaining the mechanism of accelerated DEHP degradation in biochar-assisted vermicomposting. Soil pH, soil organic matter, and humus (humic acid, fulvic acid, and humin) increased by earthworms or biochar enhanced DEHP degradation. These findings imply that biochar-assisted vermicomposting enhances DEHP removal not only through rapid physical sorption but also through the improvement of soil physicochemical characteristics and promotion of degraders in the soil, earthworm gut, and charosphere. Overall, biochar-assisted vermicomposting is a suitable method for the remediation of organic-contaminated farmland soils.

Assessment of soil enzymatic resilience in chlorpyrifos contaminated soils by biochar aided Pelargonium graveolens L. plantation

Chlorpyrifos (CP), a broad-spectrum organophosphorus insecticide, is known for deleterious effects on soil enzymatic activities. Hence, the present study aims to examine the resilience effect of biochar (BC) aided Pelargonium graveolens L. plantation on enzymatic activities of chlorpyrifos contaminated soil. The two chlorpyrifos contaminated agriculture soils (with concentrations: S1: 46.1 and S2: 95.5 mg kg^-1) were taken for the pot experiment. The plant biomass, plant growth parameters, soil microbial biomass, and enzymatic activities such as alkaline phosphatase, N-acetyl glucosaminidase, aryl sulphatase, cellulase, β-glucosidase, dehydrogenase, phenoloxidase, and peroxidase enzymes were  examined. Ecoenzyme activities and their stoichiometry were used to enumerate the different indices including geometric mean, weighted mean, biochemical activity indices, integrated biological response, treated-soil quality index, and vector analysis in all treatments. The results of the study demonstrated that the biochar incorporation enhanced the tolerance of P. graveolens (from 42-45% to 55-67%) in chlorpyrifos contaminated soil and reduced the CP accumulation in plants. A reduction in the inhibitory effect of chlorpyrifos on soil enzymatic activities and plant growth by BC incorporation was observed along with an increase in the activities of ecoenzymes (16.7-18.6%) in soil. The investigation indicated more microbial investments in C and P than that in N acquisition under CP stress. The BC amendment catalyzed the activities of lignin and cellulose-degrading enzymes and enhanced nutrition acquisition. The CP contamination and BC amendment have no significant effect on the oil quality of P. graveolens. The study demonstrated that BC-aided P. graveolens plantation offers sustainable phytotechnology for CP contaminated soil with an economic return.

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 for the removal of contaminants from soil and water: a review

Biochar shows significant potential to serve as a globally applicable material to remediate water and soil owing to the extensive availability of feedstocks and conducive physio-chemical surface characteristics. This review aims to highlight biochar production technologies, characteristics of biochar, and the latest advancements in immobilizing and eliminating heavy metal ions and organic pollutants in soil and water. Pyrolysis temperature, heat transfer rate, residence time, and type of feedstock are critical influential parameters. Biochar’s efficacy in managing contaminants relies on the pore size distribution, surface groups, and ion-exchange capacity. The molecular composition and physical architecture of biochar may be crucial when practically applied to water and soil. In general, biochar produced at relatively high pyrolysis temperatures can effectively manage organic pollutants via increasing surface area, hydrophobicity and microporosity. Biochar generated at lower temperatures is deemed to be more suitable for removing polar organic and inorganic pollutants through oxygen-containing functional groups, precipitation and electrostatic attraction. This review also presents the existing obstacles and future research direction related to biochar-based materials in immobilizing organic contaminants and heavy metal ions in effluents and soil.

Graphical Abstract

Batch adsorption of herbicides from aqueous solution onto diverse reusable materials and granulated activated carbon

This study reports the kinetics and isotherms of the adsorption of five herbicides, MCPA, mecoprop-P, 2,4-D, fluroxypyr and triclopyr, from aqueous solutions onto a range of raw and pyrolysed waste materials originating from an industrial setting. The raw waste materials investigated demonstrated little capability for any herbicide adsorption. Granulated activated carbon (GAC) was capable of the best removal of the herbicides, with >95% removal observed. A first order kinetic model fitted the data best for GAC adsorption of 2,4-D, while a pseudo-first order model fitted the data best for GAC adsorption of fluroxypyr and triclopyr, indicating that adsorption was via physisorption. A pseudo-second order kinetic model fitted the GAC adsorption of MCPA and mecoprop-P, which is indicative of chemisorption. The adsorption of the herbicides in all cases was best described by the Freundlich model, indicating that adsorption occurred onto heterogeneous surfaces.