Enhanced neonicotinoid removal in constructed wetlands using Fungus-Fe/Mn biochar

The environmental persistence and toxicity of neonicotinoids, such as imidacloprid (IMI) and thiamethoxam (THX), pose substantial threats to aquatic ecosystems. This study evaluated the performance of constructed wetlands (CWs) amended with a novel Fungus-Fe/Mn biochar substrate (synthesized by immobilizing the white-rot fungus Phanerochaete chrysosporium onto Fe/Mn-modified biochar) for enhanced removal of IMI and THX from simulated agricultural wastewater. CWs integrated with Fungus-Fe/Mn biochar demonstrated significantly improved removal efficiencies of 73.3 % for IMI and 66.7 % for THX, surpassing those of Fe/Mn biochar alone (66.4 % IMI, 58.1 % THX) and control systems (55.1 % IMI, 37.3 % THX). Mechanistic analysis indicated that removal was facilitated by both substrate adsorption (32.3-37.5 %) and microbial degradation (32.4-35.1 %), with enhanced production of degradation metabolites in the amended systems. Metagenomic analysis revealed increased microbial diversity and the enrichment of biodegradation and pesticide degradation genes, including key genes such as p450 and mnp. Additionally, potential microbial hosts for these genes, such as Rhodococcus and Pseudomonas, were identified. Redox-active Fe³⁺/Fe²⁺ and Mn⁴⁺/Mn²⁺ species additionally promoted electron transfer and rhizosphere iron plaque formation, improving pollutant sequestration and on-situ degradation. These findings highlight the potential of fungus-biochar synergism to overcome the limitations of conventional substrates, offering a scalable and sustainable approach for pesticide remediation in CWs.