PARENT SESSION
4G Ecological risk assessment and quality criteria for contaminated soils
9:00 AM to 7:00 PM, Monday, 07 May 2001

(M/MF171) Microbiology of a soil soaked with water samples coming from dredged sediment storage.

Bedell, Jean-Philippe¹, Uroz, Stephane², Perrodin, Yves¹, ^{1 2}

ABSTRACT- Sampled water (A1, B1, C1) coming from a storage of three types of dredged sediments was obtained and use as soaking water of a soil used in the laboratory. Soil of this study was an agricultural and regional soil constituted by the first 25 cm of depth with 2.5% of organic matter. The three different types of water samples (A1, B1, C1) presented different types and quantity of major pollutants. We can expressed water sample A1 as light polluted, B1 as intermediate polluted (high range of PCB and PAH), and C1 as mixed pollution (heavy metals and organic compounds). Plants used were respectively corn (Zea maïs L.) and rye-grass (Lolium perenne L.). Estimation of total bacteria and fungi population was done after 21 and 42 days-old of soaking with synthetic rain water, and then after 21 days-old of synthetic raining water follow-up by 21 days soaked with samples water (A1,B1,C1). Around 10⁷ C.F.U. by grams of dry soil were obtained for bacterial determination in each treatments and not significant difference exhibited for all water samples tested. Whatever was the water used, first results of the diversity of bacteria in the soil showed the presence and the maintenance of some species as Burkholderia cepacia, Pseudomonas fluorescens and Agrobacterium radiobacter. Moreover, determination of minimal concentration of inhibition (M.C.I.) about zinc were realised with bacterial population in the soil immediately at the end of soaking by the three different water samples. Bacterial populations of the soil soaked by C1 expressed the most resistance about increasing concentration of zinc. Effectively, C.F.U. was detected until 1.5 g/L in case of soil soaked by water C1 and only until 0.5 g/L in soil soaked by water A1 and B1. Microbiological approach of this study showed not an impact on the quantity of bacterial presented in the soil, but an effect of the properties of these bacteria.

Key words: dredged sediments, microbiology, minimal concentration of inhibition, zinc