The Dual Effect of Hematite-Amended Constructed Wetlands: Reducing the Toxicity of SMX Degradation Products and Increasing the Dissemination of Antibiotic Resistance Genes

HighlightsWhat are the main findings?Hematite enhanced the SMX removal while promoting the ARGs dissemination.Hematite increases the SMX degradation pathway and reduced intermediate toxicity.What is the implication of the main finding?Hematite promotes the SMX removal by altering the microbial community structure, while simultaneously enhancing cell-cell adhesion, thereby facilitating the ARGs dissemination.While hematite may alleviate the SMX toxicity, the long-term ecological risks associated with its presence warrant further attention.Iron ore may enhance the treatment performance of antibiotics within constructed wetlands (CWs), but its effects on the toxicity of degradation products and antibiotic resistance genes require further investigation. This study investigated the sulfamethoxazole (SMX) removal efficiency, SMX degradation pathway, and dissemination of antibiotic resistance genes (sul1andsul2) linked to SMX in hematite-amended CW microcosms. Hematite, due to its large specific surface area and formation of high redox potential, promoted SMX removal (99.05–99.26%) by adsorption, thus enhancing microbial biodegradation. The addition of hematite increased SMX degradation pathways and simultaneously attenuated the ecotoxicity of intermediate products. However, hematite also stimulated the production of extracellular polymeric substances by microorganisms, enhancing cell–cell adhesion and increasing membrane permeability, ultimately leading to a rise in the abundance ofsul1andsul2. Therefore, although iron ore provides benefits in practical applications, the potential environmental risks it poses deserve serious consideration.