BACTERIAL TRANSPORT AND PHENANTHRENE BIODEGRADATION IN SOIL AND AQUIFER SAND

Remediation of contaminated soil by inoculated bacteria requires movement of the bacteria to the site of contamination. Addition of a phenanthrene-metabolizing Psudomonas sp. to the surface of 1.5-cm columns of sterile or nonsterile soil or aquifer sand resulted in the rapid mineralization of phenanthrene present in the top 0.4 cm of sand or soil columns receiving intermittent or no water Bow. However, the surface-inoculated pseudomonad mineralized little of the substrate present in the bottom 0.4-cm portion of nonsterile soil or aquifer sand that had been sterilized prior to inoculation, although mineralization occurred at the bottom of nonsterile aquifer sand. Little biodegradation was evident if the bacterium and the substrate were both at the bottom part of columns of soil and aquifer sand receiving intermittent Bows of water, although rapid biodegradation occurred at this site in soil if the water flow was constant. Only approximate to 1% of the added cells passed through the soil after passage of approximate to 1.5 pore volumes of water, although approximate to 4% passed through the aquifer sand. We suggest that bacteria added to the soil surface or to aquifer solids for biodegradation may not be transported sufficiently to reach organic pollutants at sites distant from channels or macropores.