Effects of Biochar on Pesticides Sorption in Soils

Background and Objectives
Pesticides are extensively used in the modern agricultural systems. The inefficient and extensive use of pesticides during the last 5 to 6 decades inadvertently led to serious deterioration of environmental quality with health risk to living organisms, including humans. It is important to use some environmentally friendly and sustainable approaches to remediate, restore and maintain soil quality. 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 adsorption or degradation of 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.
 
Review methodology
ResearchGate, Scopus, Google Scholar, Web of Science, and ScienceDirect.com were used as sources to gather information for this study. These database sites were preferred because these sites are the most complete and contain the most prominent and important research publications. The major search term was "effect of biochar amendment on the bioavailability of pesticide". In this strategy, 40 articles published between 2012 and 2024were chosen. Furthermore, the relevant studies cited in the above publications were examined.
 
Conclusion
The current review highlighted the implications of biochar application in soils to control pesticides fate. Application of biochar to soil greatly affects pesticides sorption/desorption, biodegradation, leaching in soil. The sorption/desorption of pesticides on biochar surfaces depends on the physicochemical characteristics of biochar: (i) chemical structure and composition, (ii) porosity, surface area, (iii) pH and elemental ratios, and (iv) surface functional groups. It has been also observed that all these physicochemical characteristics of biochar rely on the feedstock type and production conditions. Moreover, the sorption capacity of biochar also varies with the type of pesticides. The degradation of pesticides in soil occurs via various reactions such as hydrolysis, photolysis, oxidation, and biodegradation. To advance biochar’s application, mitigate environmental risks from pesticides, and enhance pesticide efficiency, in-depth research on biochar’s adsorption mechanisms is crucial. Factors affecting biochar bioavailability, development of functional products and field production applications should be addressed to provide effective scientific evidence for the safe and rational use of biochar. In the management of pesticide pollution, it may be necessary to combine other technical approaches, such as loading degrading bacteria into biochar to enhance degradation capabilities and using biochar to prepare slow-release formulations to reduce the amount of pesticide used. Although there are still many challenges at present, with the continuous progress of technology and the expansion of applications, it is believed that biochar materials will play a more important role in the future.
 
Future perspectives
The available literature provides ample justification for some key knowledge gaps regarding the use of biochar to control pesticides fate in soil and could be considered to advance our understanding of biochar use for remediation of pesticides in soil. Research is needed on the capacity of modified biochar for sustainable management of land productivity. Moreover, it can be of great importance to classify biochars (including modified biochars) based on their capacity to bind/hold pesticides over time. It is important to explore if the pyrolytic conditions and the type of feedstock affect the efficacy of biochars in degradation of pesticides. Furthermore, the effect of feedstock type and pyrolytic conditions on soil microbial activity is not well-understood and research is warranted to examine these fundamental aspects. The available literature data show that the interactions of biochar, pesticides and soil microbial activity are poorly understood. There is no clear trend of biochar application on soil microbial activity and the role of soil fauna and flora towards pesticide mineralization under biochar application. There exists very limited data regarding the effects of biochars on the mode of action and chemistry of pesticides and how the sorption of pesticides on biochar vary with soil types. Similarly, the data about the role of different organic matter fractions on pesticide sorption are very limited.
Conflict of interest
The authors declare no conflict of interest.
 
Ethical considerations 
The authors avoided data fabrication, falsification, plagiarism, and misconduct.
 
Data Availability Statement
Data is available on reasonable request from the authors.
 
Acknowledgements
The authors would like to sincerely thank the anonymous reviewers for their valuable comments and constructive suggestions, which greatly contributed to improving the quality of this manuscript. The authors also wish to express their gratitude to the editor for their guidance and support throughout the review process.