Pollutant Transport within the Vadose Zone of Natural Soils: With Focus on the Interactions of Individual Soil Horizons

Increasing impervious surfaces in the urban landscape has created a need for stormwater management practices that control both volume and peak flow rate. Infiltration systems are preferred because they address both issues. However, the potential for groundwater contamination is a concern when siting an infiltration practice. In addition, soil is not homogeneous and its variety of layers provides a heterogeneous environment for pollutant removal. This study, started in November 2007 and to be completed by October 2008, is using undisturbed natural soil columns of a Wharton silt loam and Leetonia loamy sand to treat stormwater runoff from roofing, parking lots and sidewalk. This research is a temporal study of runoff treatment and soil accumulation as a function of soil horizon and resultant soil chemistry. Early water results show leaching of total nitrogen and removal of total phosphorus by all soil horizons of both soil types. Potassium and sulfate removal has been seen in the AB/A1A2 and OAB/OA1A2 soil horizon columns of both soils but may only be temporary. The lower horizons and the entire profile are able to retain the leaching potassium and sulfate from the organic horizon. All soil horizons of both soil types have lowered the pH of influent stormwater and increased conductivity, turbidity, color, and hardness.