A recent study published in BiocharBiochar is a carbon-rich material created from biomass decomposition in low-oxygen conditions. It has important applications in environmental remediation, soil improvement, agriculture, carbon sequestration, energy storage, and sustainable materials, promoting efficiency and reducing waste in various contexts while addressing climate change challenges. More by Dong He, Yujiao Wen, Shangzhi Wei, Shikai Li, Lide Liu, Jinmeng Wu, Zhi Zhou, Nan Zhou, Hongmei Liu, and Zhonghua Zhou, has explored a novel approach to tackle pesticide contamination in soil: converting the residues into plant-available nutrients like ammonium nitrogen (NH4+​−N). This research not only addresses environmental concerns but also offers a sustainable way to provide fertilization for crops.

The study focused on clothianidin (CTD), a widely used neonicotinoid insecticide, known for its persistence in agricultural soils with a half-life ranging from 148 to 6931 days. The research team synthesized Fe3​S4​-loaded biochar (BC@Fe3​S4​) using a one-step hydrothermal method. This material demonstrated excellent catalytic capabilities for activating peroxymonosulfate (PMS), a key component in Advanced Oxidation Processes (AOPs) used for contaminant degradation.

A significant finding was the successful conversion of CTD into NH4+​−N. In a soil-water system containing 20 mg L−1 of CTD, the BC@Fe3​S4​+PMS treatment resulted in an NH4+​−N concentration of up to 3.029 mg L−1. This is a substantial improvement compared to systems without the full treatment, where NH4+​−N levels were considerably lower. The production of NH4+​−N increased with higher initial CTD concentrations, confirming the system’s efficiency in nutrient conversion.

Beyond nutrient conversion, the study investigated the direct impact on plant growth and pesticide residue. When lettuce was grown in soil contaminated with 20 mg kg−1 of CTD, the dry weight of lettuce was 17.3 mg/plant, and concerningly, CTD residue was detected in the lettuce at 2.9228 mg kg−1. However, after treating the same contaminated soil with BC@Fe3​S4​+PMS, the dry weight of lettuce significantly increased to 29.3 mg/plant. This represents a 69.36% increase in dry weight. Crucially, no CTD residue was detected in the lettuce grown in the treated soil. This outcome powerfully demonstrates the dual benefit of the treatment: effective pesticide degradation and enhanced crop growth through nutrient provision.

The mechanism behind this conversion and degradation involves the generation of various reactive oxygen species (ROS), including hydroxyl radicals (OH), singlet oxygen (1O2​), and sulfate radicals (SO4−​). These ROS play a leading role in breaking down CTD into intermediates, which are then further degraded into NH4+​−N, carbon dioxide (CO2​), and water (H2​O). Toxicity assessments using T.E.S.T-QSAR software revealed that the toxicity of CTD and its degradation intermediates to organisms like Fathead minnow and T. pyriformis generally decreased after the BC@Fe3​S4​+PMS treatment, especially due to dechlorination and ring-opening reactions in the degradation pathways.

This research presents a promising strategy for soil remediation and sustainable agriculture. The BC@Fe3​S4​+PMS system offers a feasible approach to remove persistent organic pollutants from agricultural soil while simultaneously converting them into valuable nutrients, thereby improving the farmland’s productive environment. While the study successfully demonstrated these effects in a greenhouse setting, future research should focus on multi-factor optimization, long-term field trials, and further investigation into the specific contribution efficiency of each ROS to fully realize the practical application potential of this innovative technology.

Source: He, D., Wen, Y., Wei, S., Li, S., Liu, L., Wu, J., … & Zhou, Z. (2025). Conversation of pesticide residues into ammonium nitrogen (NH4+​−N) through AOPs and its fertilization effect on lettuce growth. Biochar, 7(88).