Synergistic removal of morpholine fungicides and cadmium from agricultural water by a biochar-immobilized bacterial-duckweed system: Quantifying roles of biodegradation, adsorption, and phyto-uptake.

The co-contamination of agricultural water by morpholine fungicides (e.g., flumorph and dimethomorph) and cadmium (Cd) poses significant ecological threats, challenging conventional treatment approaches. This study developed an innovative bioremediation system integrating biochar-immobilized microbial consortia with phytoremediation, and quantified the individual contributions of biodegradation, biosorption, phyto-uptake, and biochar-adsorption to the synergistic removal of pesticide and Cd co-contaminants. A novel Cd-tolerant and flumorph-degrading bacterium, Alcaligenes faecalis X4, was combined with a dimethomorph-degrading strain (Bacillus cereus WL08) to form a stable consortium. This consortium was capable of simultaneously metabolizing both fungicides into less toxic products and adsorbing cadmium. The consortium was immobilized on bamboo charcoal to produce a biocomposite (BCI-X4 + WL08), which achieved high removal efficiencies under optimized conditions: 97.65% for flumorph (50 mg/L), 94.23% for dimethomorph (50 mg/L), and 82.68% for cadmium (10 mg/L). Subsequent introduction of duckweed (Lemna minor) contributed an additional 15.40-28.00% removal via phyto-accumulation. Partitioning analysis confirmed true synergistic interactions-rather than merely additive effects-enhancing overall removal by up to 3.27-fold while alleviating oxidative stress in the plants. A compound ecological filter bed incorporating both BCI-X4 + WL08 and duckweed demonstrated practical applicability under outdoor conditions, achieving average simultaneous removal rates of 94.96% (flumorph), 91.43% (dimethomorph), and 85.42% (Cd) across three consecutive seasons, along with improved water quality parameters. This work presents a scalable, eco-friendly strategy for the in situ remediation of surface waters co-contaminated with pesticides and heavy metals, and provides a quantitative assessment of the distinct microbial, plant, and biochar contributions to the synergistic remediation process.