N-152. Microbial Communities of Deep Groundwater Ecosystem after an Extensive Uranium Leaching in the Stráž pod Ralskem Site - Czech Republic

V. Libova1, O. Korotkevych1, A. Benakova1, J. Charvat2, P. Franta3, P. Rossi4, M. V. Brennerova1;
1Inst. Microbiol., Prague, CZECH REPUBLIC, 2DIAMO, Stráž pod Ralskem, CZECH REPUBLIC, 3Nuclear Res. Inst., Řež, CZECH REPUBLIC, 4EPFL – LBE, Lausanne, SWITZERLAND.

The Stráž pod Ralskem region is a part of the Bohemian Cretaceous Basin. The geological profile of the site consists of Quaternary river sediments, Middle Turonian sandstone, Lower Turonian siltstone and Cenomanian collector formed by friable sandstone containing Uranium bearing minerals and upper fucoid sandstone forming an overlying back of the ore. Both classical deep mining and in-situ Uranium leaching took place for about 30 years. The chemical enrichment was carried out by injection of technological solutions with 50-60 g/L sulfuric acid into the deep layers of the Cenomanian aquifer. The amount of dissolved matter is estimated at 4 million tons. Overflow of the highly contaminated Cenomanian groundwater to the Turonian collector endangers the sources of drinking water, as groundwater is the only source of drinking water in Northern Bohemia. Studies on microbial activities may have implication for the selecting of appropriate sanitation measures in the region. Water samples were taken from Turonian and Cenomanian wells (19 to 223 meters below the surface, respectively). Bacterial community structures, based on the 16S rRNA gene pools, were analyzed with denatured gradient gel electrophoresis (DGGE). Numerical ecology tools were applied for correlating the phylogenetic profiles with environmental variables, such as geological structure, water chemistry and pollutant concentrations. Our results clearly show that the bacterial community profiles clustered according to their geological origin. The largest cluster was composed of eight Cenomanian samples, correlating with a very low pH (< 2), the highest conductivity and the highest concentration of SO42- (up to 59 000 mg/L), NH4+ (up to 1 253 mg/L), NO3- (up to 920 mg/L) and total Fe (up to 2 576 mg/L). Two smaller clusters of Turonian origin were correlating with intermediate levels of the above mentioned environmental variables. The diversity of dissimilatory sulfite reductase genes was studied equally and correlated with environmental variables.
This research was supported by the Ministry of Industry and Trade of the Czech Republic, Grant No.FT-TA3/070.