Viral and chemical tracer movement through contrasting soils

Land treatment of animal or human waste can result in chemical and microbial contamination of shallow ground water and/or water-ways. We investigated the fate of a host-specific Salmonella bacteriophage and a nonreactive chemical (Br-) tracer when applied to large intact lysimeter soil cores (500 mm diam. by 700 mm high). The soils included a poorly drained Gley Soil and well-drained Pumice, Allophanic, and Recent Soils. A depth of 30 mm of water containing the bacteriophage and Br- was applied to the soil at a rate of 5 mm h(-1) followed by up to about 1.8 pore volumes of simulated rainfall. Resulting leachates, collected continuously over at least one pore volume were analyzed for the bacteriophage and bromide (Br-) tracers. Bromide moved uniformly through the Pumice and Allophanic Soils with peak concentrations at about 1 pore volume, while the bacteriophage was detected only at trace levels or not at all. In contrast, both Br- and bacteriophage tracers moved rapidly through Gley and Recent Soils, appearing early in the leachate and then tailing off. Such flow patterns in the Gley and Recent Soils are indicative of bypass flow. Coarse soil structure in the Gley Soil, and finger-flow due to water repellency in the sandy Recent Soil are considered responsible for the observed bypass flow in these two soils. Allophanic and Pumice Soils have finer, more porous soil structure leading to a predominance of matrix flow over bypass flow. This study suggests vertical movement of viruses varies significantly with soil type.