Enhanced sustainable remediation of co-contaminated soil and groundwater with lead and arsenic utilizing the willow-vetiver-permeable reactive barrier system

Soil and groundwater pollution are closely linked, necessitating integrated remediation strategies. However, research on the combined use of phytoremediation and permeable reactive barriers (PRB) for the synergistic remediation of lead (Pb) and Arsenic (As) co-contaminated soil and groundwater remains limited. This study investigates the sustainable integrated remediation of Pb and As co-contaminated soil and groundwater through laboratory simulations, utilizing a combination of willow, vetiver grass, and PRB. The study demonstrated a significant reduction in groundwater Pb and As concentrations, from 500 μg L⁻¹ to <0.5 μg L⁻¹ and 0.99 to 2.04 μg L⁻¹, respectively. Soil Pb levels decreased by 13.25–33.76 mg kg⁻¹ compared to initial levels. Notably, plant-derived organic carbon significantly influenced the composition and content of organic carbon in groundwater, ensuring a sustainable carbon supply. Transcriptome profiling of willow leaves indicated up-regulation of genes associated with photosynthesis, arsenate reductase activity, and phagosome function, potentially enhancing As and Pb extraction. Dominant soil and groundwater bacteria, including Roseiflexaceae, Intrasporangiaceae, KD4-96, Bacillus_drentensis, and SBR 1031, exhibited Pb and As immobilization capabilities. Furthermore, GC–MS analysis showed that up-regulated carboxyl-containing organics lowered groundwater pH from >9 to 7.5 by day 35, without compromising As and Pb remediation efficiency. This research provides insights into the sustainable integrated remediation of Pb and As contamination in soil and groundwater.