Pressure Gradient Enhanced Air Sparging for VOC ‐Contaminated Soils: Evaluation in a Three‐Dimensional Laboratory Model

This study presents a pressure gradient enhanced air sparging (PGEAS) approach that intensifies local pressure gradients and airflow in contaminated soils. Three‐dimensional laboratory model tests evaluated emitted gaseous contaminant concentrations, residual contaminant distributions, total removal efficiency, and effective removal zones in low‐ and high‐permeability soils. Contaminant distributions were spatially discrete and irregular in low‐permeability soil, but more continuous and geometrically organized in high‐permeability soil. Surface gaseous emissions and residual contaminant distributions jointly revealed permeability‐dependent differences in gas transport and remediation response. In high‐permeability soils, conventional air sparging (CAS) already achieved high removal, and increasing sparging pressure provided limited additional benefit; PGEAS further improved removal, although modestly. In low‐permeability soils, CAS produced weak gaseous emissions and high residual concentrations, whereas PGEAS improved total removal efficiency and effective removal zone, particularly at relatively low injection pressures. Compared with CAS, PGEAS increased total removal efficiency by up to approximately 15 percentage points in high‐permeability soil and 10 percentage points in low‐permeability soil. In low‐permeability soil, it also expanded the effective removal zone by 13–25% and enhanced contaminant removal at relatively low injection pressures. These findings demonstrate the laboratory‐scale potential of pressure gradient enhancement for improving air sparging performance in low‐permeability soils.