## 3 Results and Discussion
### Driving Mechanism of ARG Changes During Different Remediation Methods  
RDA revealed that shifts in microbial community structure were the primary drivers of dynamic changes in LRGs and ARGs in Pb-contaminated soils. Environmental factors such as pH and heavy metal concentrations indirectly influenced the abundances of LRGs and ARGs by altering bacterial communities. As shown in Figure 6, the Pb concentration and pH directly affected several potential hosts of LRGs and ARGs, such as Proteobacteria, Actinobacteria, Acidobacteria, Firmicutes, Bacteroidetes, Deinococcus-Thermus, Planctomycetes, and Tenericutes, as well as _Alishewanella_ and _Gp16_, driving changes in the abundance of many ARGs. In Pb-contaminated soil, LRGs and ARGs dynamics were primarily governed by potential hosts. After exposure to 10 g/kg of Pb, ARGs such as _aad_A2-01, _mph_A-02, _ere_A, _cat_B3, _bla_TEM, _tet_A-02, _tet_D-01, _tet_O-01, and _tet_Q, exhibited significant increases. The research suggested that acidic conditions promoted the removal of ARGs, while high pH levels Pb to the accumulation of ARGs [(38; 39)]. These increases, particularly in _aad_A2-01, _cat_B3, and _mph_A-02, were primarily attributed to elevated Pb concentration and pH, which enriched potential hosts like Proteobacteria, Tenericutes, Deinococcus-Thermus, and Firmicutes, as well as dominant genera such as _Sphingomonas_ and _Gp16_. In remediation systems incorporating Imvite, MgO-Ca(H\({}_{2}\)PO\({}_{4}\))\({}_{2}\), and Imvite-MgO-Ca(H\({}_{2}\)PO\({}_{4}\))\({}_{2}\), ARGs shifts were primarily host-driven. Several ARGs, including _bla_TEM, _df_rA12, _su11, _su12_, and _aad_A2-01, were significantly enriched in the soil. In these systems, the stabilization of Pb and the rise in pH triggered substantial growth in phyla such as Proteobacteria, Bacteroidetes, Firmicutes, Deinococcus-Thermus, and genera like _Pseudomonas_ and _Alishewanella_. These microbial groups, acting as potential hosts, further drove increases in ARGs abundance. Interestingly, while the relative abundances of _Pbr_T and _su12_, as well as _Znt_A and _bla_TEM, were positively correlated in Imvite, MgO-Ca(H\({}_{2}\)PO\({}_{4}\))\({}_{2}\), and Imvite-MgO-Ca(H\({}_{2}\)PO\({}_{4}\))\({}_{2}\), the total abundances of LRGs and ARGs varied between treatments. The total ARGs abundance significantly increased in MgO-Ca(H\({}_{2}\)PO\({}_{4}\))\({}_{2}\) and Imvite-MgO-Ca(H\({}_{2}\)PO\({}_{4}\))\({}_{2}\), but the total LRGs abundance only rose in Imvite. Figure 6: Redundancy analysis between each factor and ARGs after different remediation methods. In the synergistic remediation system combining composite agents with BES, ARGs dynamics were primarily driven by host-related factors. The co-selection of potential hosts under changing environmental conditions likely influenced LRGs and ARGs distributions. Compared with RS, most ARGs, such as _sul2_, _dfr_A12, _aad_A2-01, _ceoA_, _floR_, _tet_B-02, _tet_D-01, _aad_E, _bla_TEM, _tet_S, and _tet_A-02, were significantly reduced. This reduction was due to the decrease in Pb ion concentration induced by BES application [15], leading to a decline in potential host bacteria such as _Pseudomonas_ and _Alishewanella_. Consequently, the relative abundances of ARGs, such as _dfr_A12, _aad_A2-01, _cooA_, _floR_, _tet_D-01, and _tet_B-02 decreased. However, some ARGs, such as _sul1_, were enriched despite the reduction in potential hosts. This may be explained by co-selection mechanisms between LRGs and ARGs. For example, _sul1_ was significantly positively correlated with _Pbr_T, and the increase in _Pbr_T abundance likely drove _sul_1 enrichment. Pb concentration and soil pH influenced the co-selection of ARGs and LRGs, while also impacting microbial community dynamics. Elevated Pb levels exerted substantial selective pressure, favoring bacteria with detoxification mechanisms, such as efflux pumps, which often conferred concurrent antibiotic resistance.