Particle Transport in Saturated Fractured Media: Effect of Flow Velocity and Fracture Aperture

Thisstudy examines the transport of micron-sized particlesin fractured chalk at high flow velocities, which has the potentialto contaminate groundwater and may have important implications forenvironmental and human health. Transport of micron-sized particles in fractured rockscan potentiallycontaminate groundwater and may have important implications for environmentaland human health. This study aimed to understand the transport ofkaolinite particles and the fluorescein tracer through fractured chalk,particularly at high flow velocities and using various fracture apertures.Laboratory experiments were conducted and results were fitted to amodel based on the advection-dispersion equation. The dispersion,attachment, and detachment parameters were evaluated and correlatedwith the flow velocity and fracture aperture. The results revealedthe influence of hydrodynamic forces. Kaolinite particles traveledfaster than fluorescein due to the size exclusion effect and higherdispersion of fluorescein. The size exclusion effect globally decreasedwith flow velocity, while dispersion of kaolinite and fluoresceinincreased. Kaolinite and fluorescein dispersed more in the narrowerfracture. The attachment coefficient increased with flow velocity,and it is fracture aperture independent. The detachment coefficientincreased with flow velocity and was higher in the narrower fracturedue to higher shear stress. The study findings highlight the importanceof considering high flow velocities and fracture aperture effect inunderstanding micron-sized particle transport mechanisms in chalkfractures, which is essential for assessing risks to groundwater resourcesand improving environmental protection.