Study on the Characteristics of Horizontal Well Air Sparging and the Behavior of Pollutant Retention

Horizontal well air sparging (HAS) technology provides a promising approach for pollution remediation. In this study, a model experiment assessed the airflow distribution characteristics of HAS under varying air sparging (AS) pressure, tube burial depth, and groundwater flow conditions, while evaluating the retardation effects of HAS on dissolved groundwater contaminants. The results indicated that airflow velocity and diffusion range increased markedly with elevated AS pressure. Deeper AS tube burial depths resulted in more uniform airflow distribution and broader coverage. Groundwater flow significantly affected airflow distribution, as greater water head differences induced a downstream shift in the airflow pattern, resulting in an asymmetric diffusion range. Regarding pollutant retardation, airflow created a physical barrier by reducing permeability and interfacial resistance, effectively hindering pollutant diffusion. Airflow from the AS tube aligned parallel to the flow direction reduced Rhodamine B concentration by 53.1% over 300 min, preventing deeper pollutant migration into the sand layer. Conversely, airflow from the AS tube oriented perpendicular to the flow direction reduced Rhodamine B concentration by 84.38% over the same period, demonstrating superior effectiveness in limiting horizontal pollutant diffusion. These findings provide valuable theoretical insights and practical guidance for implementing HAS technology in groundwater pollution management.