Physical Straining of Cryptosporidium parvum Oocysts through Saturated Soils

摘要

The colloid-sized C. parvum oocysts may be physically strained through porous media during transport. However, most of studies on C. parvum oocysts were performed with a constant flux (CF) controlled by a peristaltic pump, in which the unsteady flux caused by the physical straining mechanism was ignored. In this study, we first compared two systems in which oocysts transport through homogenous pure sand or soils either by a CF or by a constant pressure head (CP). The results showed oocysts solution flux (J_o) reduced remarkably in a CP system, but not in a CF system. More oocysts from the effluents in CF system were observed than in CP system, indicating that oocysts breakthrough was overestimated in CF system. Using the CP system, 6 intact soils typical of Ireland were further investigated. One soil had oocyst breakthrough earlier than Br, and J_o was nearly identical to Br~- flux (J_B) due to macropore flow. For the other five soils oocyst breakthrough was later than Br~-, and J_o tended to decrease with pore volume. The decrease of J_B was not found during the experiments. The unsteady-state flux of oocysts solution put forward a new challenge for us how to simulate the colloid-sized pathogen transport in soils.