Transport of the pathogenic protozoan Cryptosporidium parvum through soils threatens ground and surface water. C. parvum may be introduced into soils in the maure of infected calves. The presences of other chemicals in the soil applied as or with amendments may affect the transport of the C. parvum oocysts. We hypothesized that surfactants, which are used in many herbicide formulations, decrease water tension and disrupt the air-water interface where oocysts are thought to accumulate. In previous studies we investigated the effect of the anionic surfactant Aerosol-80 on the transport of C. parvum oocysts through four agricultural soils from Utah and Illinois. We found that the presence of the surfactant accelerated the transport of the oocysts through preferential flow paths, but that when connected macropores were not present in the soils, the surfactant retarded the transport of the oocysts through the soil matrix by straining oocyst-surfactant-Ca flocs. In the current work we assess the use of CXTFit to model C. parvum oocyst transport through soil. Using the solute transport model to model particulate transport required adjusting the retardation coefficient (Kd) to account for the solution – column contact time.