Effect of bioaugmentation on microbial transport, water infiltration, moisture loss, and surface hardness in pristine and contaminated soils.

Three different soils, a clay, a pristine sandy loam and a PCB-contaminated sandy loam, were bioaugmented to determine the influence of clay content and contaminants on the transport of bacteria in unsaturated soils, using surface irrigation water as a transport medium. The results indicate that the transport of the implanted bacteria was influenced negatively more by the presence of PCBs than by the clay content of the soil. Transport was directly related to the frequency of irrigation and length of the intervals between irrigation periods, making these variables important factors to consider when applying bioaugmentation via downward percolating water. Other parameters measured after bacterial bioaugmentation were water infiltration, moisture loss, and surface hardness of these soils. Surface water infiltration was affected more by the soil clay content than by the hydrophobic contaminant. Infiltration was significantly but differently influenced by bioaugmentation, positively in clay, negatively in sandy loam, and negatively (to a lesser extent) in the PCB-contaminated sandy loam soils. Moisture loss was slower in the bioaugmented soil than in the control soils, with this difference being most pronounced in the PCB soil. High moisture loss in the bioaugmented clay soil rendered it the hardest soil for surface penetration.