Submitted to: Environmental Protection Agency
Publication Type: Other
Publication Acceptance Date: December 2, 2003
Publication Date: July 10, 2004
Citation: Pachepsky, Y.A., Shelton, D.R. 2004. Comparison of batch and flow experimental data on retention of manure-borne Cryptosporidium Parvum Oocysts in soils. Environmental Protection Agency. (website: http://es.epa.gov/neer/publications/meetings/9-9-2003/pdf/yakov_pachepsky.pdf.) Technical Abstract: Release of the manure-borne Cryptosporidium parvum oocysts is the most probable cause of further ground and surface water contamination with this pathogen. Our objective was to assess the effect of water saturation on transport of manure-borne oocyst through soil cores. Manure seeded with oocysts was applied on the surface of 10-cm columns filled with sandy loam soil and clay loam soils. Cores were initially saturated and an eight-hour rainfall simulation provided saturated flow in one set of columns whereas the other set had suction ca. 5 kPa applied at the bottom. The convective-dispersion model with exponential boundary release, instantaneous adsorption and first-order kinetic removal of oocysts was used to simulate the transport. Transport parameters were found by fitting the van Genuchten analytical solution to the oocyst profile distributions. Oocysts stayed mostly within top 8 cm of soil columns. Cumulative oocyst contents in leachates from unsaturated columns were less than 0.1% whereas the saturated columns allowed breakthrough of 0.4% and 1.3% in sandy loam and clay loam soil cores, respectively. The model mimicked the profile distributions of oocysts very well, but failed to simulate breakthrough of small amounts of oocysts occurring probably due to a preferential flow. Values of retardation coefficient were less than unity in saturated columns and greater than unity in unsaturated columns. Values of the soil partition coefficient Kd derived from the retardation coefficient values were much less than earlier reported values from batch experiments with the same soils. The removal rates were much higher in saturated than in unsaturated columns. Soil water saturation substantially affected the manure-borne oocyst transport.