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Preferential Flow and Transport of Cryptosporidium parvum Oocysts through the Vadose Zone

Experiments and Modeling

^a Department of Biological and Environmental Engineering, Riley-Robb Hall, Cornell University, Ithaca, NY 14853
^b INRA, Unité d'Agronomie de Laon-Peronne, 02007 Laon Cedex, France
^c USDA-ARS, Campbell Natural Resource Conservation Center, Watkinsville, GA 30677
^d Department of Microbiology, Cornell University, Ithaca, NY 14853
^e Laboratory of Geoenvironmental Engineering and Science, Department of Crop and Soil Sciences, Cornell University, Ithaca, NY 14853

View larger version (66K): [in a new window]   Fig. 1. Schematic illustration of the apparatus used in the laboratory experiments.

View larger version (74K): [in a new window]   Fig. 2. Examples of blue dye distribution for various locations in the columns and at different flow rates: (a) the distribution zone, (b) immediately above the capillary fringes, and (c) in the capillary fringes. The number of fingers formed was different for the various flow rates: (d) 1 cm h–1 in Exp. I, (e) 2 cm h–1 in Exp. I, and (f) for the column with hydrophobic sand in Exp. II.

View larger version (22K): [in a new window]   Fig. 3. Breakthrough curves and model prediction of Cl– and C. parvum oocysts in regular and water-repellent 12/20 silica sand. Initial concentrations in the applied feces was 12.5 g Cl– L–1 and 3.5 x 108 C. Parvum oocysts L–1. (a) 0.3 cm h–1 rainfall (regular sand, Exp. I), (b) 1 cm h–1 rainfall (regular sand, Exp. I), (c) 2 cm h–1 rainfall (regular sand, Exp. I), (d) 1 cm h–1 rainfall (water-repellent sand, Exp. II), and (e) 1 cm h–1 rainfall (regular sand with two water-repellent layers, Exp. II).

View larger version (25K): [in a new window]   Fig. 4. Water saturation profile and spatial distribution of C. parvum oocysts in 12/20 silica sand resulting from a 2 cm h–1 rainfall event (Exp. I).

View larger version (14K): [in a new window]   Fig. 5. Breakthrough curves and model prediction of Cl– and C. parvum oocysts in undisturbed soil columns for Exp. III. Initial concentrations in the applied feces was 12.5 g Cl– L–1 and 3.5 x 108 C. Parvum oocysts L–1. (a) 12-cm Hudson soil column, (b) 20-cm Hudson soil column, and (c) 30-cm Arkport soil column.

View larger version (13K): [in a new window]   Fig. 6. Soil column flow rate from 20-cm Hudson soil column A.