Effects of Soil Type and Cover Condition on Cryptosporidium parvum Transport in Overland Flow

Overland transport kinetics of pathogens is controlled, in large part, by soil and vegetation. With an increasing number of concentrated animal operations, there is becoming a greater need to dispose of a vast amount of manure in a single, localized area. Animal manure contains a substantial amount of microbial pathogens, including Cryptosporidium parvum that may pose a threat of contamination of water resources. This study examines the kinetics of C. parvum in overland transport and critical factors involved in the design of best management practices, especially vegetative filter strips, to prevent the transport of harmful pathogens to water bodies. Three soil types were tested (Catlin silt-loam, Alvin fine sandy-loam, Darwin silty-clay), spanning the entire spectrum of typical Illinois soils. A 20-min rainfall event was produced using a small-scale (1.07 m?×?0.66 m) laboratory rainfall simulator over a soil box measuring 0.67 m?×?0.33 m. Each soil type was tested for pathogen transport kinetics with bare surface conditions as well as with smooth brome and fescue vegetative covers. Surface runoff, soil cores, and near-surface runoff were each analyzed for infective C. parvum oocysts using cell culture infectivity assays. Results showed that vegetation greatly reduced the recovery of infective oocysts, in addition to delaying the time to the peak recovery. However, there was no clear evidence of any one vegetation type being advantageous over another. The bare soil experiments resulted in a higher recovery of C. parvum oocysts from the Darwin soil compared to other two soils. Analyses of soil cores show a slightly higher recovery of oocysts in the Catlin soil compared to Alvin or Darwin soils.