Use of an avoidance test for the assessment of microbial degradation of PAHs 1 2

1 2 An avoidance test using the soil springtail Folsomia candida was used to assess 3 changes in contamination levels at low doses of PAHs following incubation with 4 indigenous microflora. A soil from a former coke site was diluted to 1% in an unpolluted 5 soil from the same site, which was used as a control, then both substrates were 6 remoistened to 80% field capacity. The diluted soil was previously shown to be strongly 7 repellent to F. candida, although not toxic. After two-month incubation at 20°C, the mixture 8 lost its repellence capacity and became attractive to the test animal, while the global 16 9 PAHs content had decreased to a great extent (50%). PAH disappearance was linked to 10 the occurrence of indigenous microbiota able to degrade hydrocarbons. 11 12