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United States Department of Agriculture

Agricultural Research Service

Title: Field Transport of Cryptosporidium Surrogate in Small Catchments Used for Grazing Lands

Authors
item Amirtharajah, A -
item Young, M -
item Pennell, K -
item STEINER, JEAN
item Fisher, Dwight
item ENDALE, DINKU

Submitted to: American Water Works Association Research Foundation
Publication Type: Research Notes
Publication Acceptance Date: September 21, 2001
Publication Date: N/A

Interpretive Summary: Cryptosporidium parvum is a small pathogenic parasite. It has been found in many drinking water sources. The inactive form, known as an oocyst, is excreted in the feces of infected animals and humans into the environment. The transport mechanism of C. parvum oocysts through soil to reach and contaminate water bodies is not well understood. This research used polystyrene microspheres as surrogates to C. Parvum oocysts under field an controlled laboratory conditions to investigate potential mechanisms for their transport. A 40x30-m site at the outlet of an 8-ha grazing catchment just above a spring was intensively instrumented to monitor hydrologic events and microsphere transport after injecting the surrogate near the soil surface 14-m upstream of the spring. A few microspheres were detected on few occasions at sampling sites of the field, especially after rainfall events. This suggests that very small number of these surrogate particles travel through preferential flow paths at field sites. The column studies focused on transport of surrogate microspheres through well characterized sand media and soil media from the field site. The vertical migration of the microspheres in the column studies was minimal. This suggests the migration of C, Parvum oocysts through fine-textured soils is likely to be minimal. The parameters measured from column studies were used as input variables in a 1-D hydrological transport model (HYDRUS-1D), and indicated that reasonable prediction could be made of soil water content, and the limited movement and depth penetration of solutes (surrogate particles) would occur based on antecedent water storage and rainfall.

Technical Abstract: The potential migration of Cryptosporidium parvum, a small (4-6 æm) and known emerging pathogen, through soils to surface waters has rarely been studied. A field and complementary controlled laboratory column study investigated transport behavior of C. Parvum oocyst surrogate in form of similar sized polystyrene microspheres. The field site was a 30 by 40-m portion of a small catchment used for grazing research situated just upstream of a spring. A 0.5 by 1.0-m site 14-m upstream of the spring was injected with the surrogate. The hydrologic balance (rainfall, evapo- transpiration, soil water, soil water potential, groundwater and spring flow) was characterized. The microspheres were detected and counted in water samples collected from zero-tension lysimeters, wells, flow-through- centrifuge and spring. The column studies focused on transport of surrogate microspheres through well characterized sand media and soil media afrom the field site. The vertical migration of the microspheres in the column studies was minimal suggesting the migration of C, Parvum oocysts through fine-textured soils is likely to be minimal. A few microspheres were detected on few occasions at sampling sites of the field, especially after rainfall events. This suggests that very small number of these surrogate particles travel through preferential flow paths at field sites. Parameters obtained from the column studies were used as input variables in a 1-D hydrological transport model (HYDRUS-1D), and indicated that reasonable prediction could be made of soil water content, and the limited movement and depth penetration of solutes (surrogate particles) would occur based on antecedent water storage and rainfall.

Last Modified: 7/28/2014
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