The migration of extracellular antibiotic resistance genes (eARGs) in porous media is an important pathway for ARGs to spread to the subsoil and aquifer. Biochar (BC) has been widely used to reduce the mobility of soil contaminants, however, its effect on the mobility of eARGs in porous media and the mechanisms are largely unknown. Herein, the effects of BCs synthesized from wheat straw and corn straw at two pyrolysis temperatures (300 °C and 700 °C) on the transport of plasmids-carried eARGs in sand column were investigated. The BC amendments all significantly decreased the mobility of eARGs in the porous medium, but the mechanism varied with pyrolysis temperature. The higher temperature BCs had a stronger irreversible adsorption of plasmids and greatly enhanced the attachment and straining effects on plasmids during transport, thus more effectively inhibited the mobility of eARGs. The lower temperature BCs had weaker adsorption, attachment, and straining effects on plasmids, but induced generation of hydroxyl radicals in the porous medium and thereby fragmented the plasmids and hindered the amplification of eARGs. These findings are of fundamental significance for the potential application of BC in controlling the vertical spread of eARGs in soil and vadose zones.

细胞外抗生素抗性基因（eARGs）在多孔介质中的迁移是ARGs向底土和含水层扩散的重要途径。生物炭 (BC) 已被广泛用于降低土壤污染物的迁移率，但其对多孔介质中 eARGs 迁移率的影响及其机制尚不清楚。在此，研究了在两种热解温度（300°C 和 700°C）下由小麦秸秆和玉米秸秆合成的 BCs 对质粒携带的 eARGs 在沙柱中运输的影响。BC 修正均显着降低了 eARGs 在多孔介质中的迁移率，但其机理随热解温度的不同而不同。较高温度的 BCs 对质粒具有更强的不可逆吸附，并大大增强了运输过程中对质粒的附着和拉紧作用，因此更有效地抑制了 eARGs 的移动性。较低温度的BCs对质粒的吸附、附着和拉紧作用较弱，但会在多孔介质中诱导羟基自由基的产生，从而使质粒片段化，阻碍eARGs的扩增。这些发现对于 BC 在控制土壤和渗流区 eARGs 垂直扩散方面的潜在应用具有根本意义。