Virus transport in a discrete fracture

Tracer experiments were carried out in a naturally discrete-fractured chalk core with solute tracers Li⁺ and Br^-, and colloidal tracers of two origins-bacteriophages (MS2, φX174 and T4) and fluorescent latex microspheres. The colloidal tracers were either ∼20 nm (MS2, φX174 and microspheres) or ∼200 nm (T4 and microspheres) in size. Both solute and colloidal tracers were injected at a constant flux at the fracture inlet and collected at the outlet to evaluate the form of their breakthrough curves (BTCs). The BTCs of all tracers were compared and analyzed. The BTC analysis displayed significant differences in recovery as a function of tracer size and type. Even within the same colloid size, transport of the microspheres and bacteriophages was dissimilar, likely due to minor differences in density, surface chemistry and shape. More pronounced peaks and recoveries were observed with ∼200 nm compared to ∼20 nm microspheres and phages. Arrival time at the outlet was also size-dependent, with larger microspheres and phages having longer residence times than smaller ones, and solutes being 5-15 times slower than colloids of both sizes. The observed differences were explained by a combination of size and electrostatic interactions that facilitates entrance and transport within the pores in the chalk matrix. Overall, our results clearly demonstrate that fractures are favorable carriers for viruses of different sizes with different surface properties. The viruses' properties were also shown to govern their transport through the fractures.