Preferential transport of Cryptosporidium parvum oocysts in variably saturated subsurface environments. Water Environ. Res

ABSTRACT: When oocysts of the protozoan Cryptosporidium parvum contaminate drinking water supplies, they can cause outbreaks of Cryptosporidiosis, a common waterborne disease. Of the different pathways by which oocysts can wind up in drinking water, one has received little attention to date; that is, because soils are often considered to be perfect filters, the transport of oocysts through the subsoil to groundwater is generally ignored. To evaluate the significance of this pathway, a series of laboratory experiments investigated subsurface transport of oocysts. Experiment 1 was carried out in a vertical 18-cm-long column filled either with glass beads or silica sand, under conditions known to foster fingered flow. Experiment 2 involved undisturbed, macroporous soil columns subjected to macropore flow. Experiment 3 aimed to study the lateral flow on an undisturbed soil block. The columns and soil samples were subjected to artificial rainfall and were allowed to reach steady state. At that point, feces of contaminated calves were applied at the surface along with a known amount of potassium chlorid