An enhanced air sparging approach for remediation of VOCs-contaminated low-permeability soils through pore pressure...

Remediating VOCs-contaminated low-permeability soils remains challenging due to restricted air flow and inefficient contaminant mass transfer. This study proposes an enhanced sparging approach that integrates sparging with pressure-relief pipes. By jointly regulating the sparging pressure and backpressure to elevate pore pressure, a more stable and continuous airflow network is established, thereby improving the overall remediation performance. Laboratory model tests reveal that emitted gaseous contaminants at the soil surface show irregular and random distributions under both conventional and proposed sparging approaches, yet the proposed approach yields significantly higher emission concentrations at identical seepage pressures, with average values nearly twice those of conventional sparging. In low-permeability soils, residual contaminants remain randomly dispersed after sparging, but conventional sparging leaves higher concentrations with localized accumulation, reflecting poor removal efficiency. In contrast, proposed sparging, through pore pressure regulation, markedly reduces residual levels, and the effect becomes more pronounced as pore pressure increases, achieving a total removal rate of 80 % compared with 60 % for conventional sparging. Analysis of pore pressure distribution and air saturation reveals that proposed sparging significantly expands high-pressure zones and increases air saturation. Correlation among total removal rates, average pore pressure, and air saturation confirm their strong interdependence, validating the mechanism by which pore-pressure regulation promotes the development of a more stable and continuous airflow network, resulting in improved contaminant removal.