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