Soil Bacterial Abundance and Diversity of Uranium Impacted Area in North Western Pirin Mountain

ABSTRACT

The former uranium mine Senocos (Blagoevgrad district, Bulgaria) has been exploited until 1991 when it was closed and later (1994–1997) reclaimed. Recently, the reclamation is compromised due to the erosion of protective layers and the mine wastes continue to affect the area resulting in increased radiation and uranium concentration in mine area. Soil bacterial abundance in more radioactive environment of mine remains unchanged (on average ((8.52±5.1) x 10⁸ cell g⁻¹) compared to the control ((8.76±3.5) x 10⁸ cell g⁻¹) in contrast to their dehydrogenase activity which decreases more than two times. Physiological and species diversity of bacterial mine communities are also affected by the pollution as it is expressed by lower values of Shannon indices compared to the control communities. All carbon sources in BIOLOG assay except 2-hydroxy benzoic acid are available for control bacterial communities and the number of unavailable carbon sources increases linearly with increasing the concentration of uranium in soil. The high levels of radionuclide pollution decrease the biodiversity to 3–4 species (66% of total) in the most polluted point of the mine territory (SPS(5)).

Keywords:

• bacterial abundance
• bacterial diversity
• community level physiological profile (CLPP)
• uranium mining