Sn. Groudev et al., In situ bioremediation of soils contaminated with radioactive elements andtoxic heavy metals, INT J MINER, 62(1-4), 2001, pp. 301-308
Two experimental plots of an agricultural land contaminated with radioactiv
e elements (uranium, radium thorium) and toxic heavy metals (copper, zinc,
cadmium) were treated by two different biotechnological in situ methods. Th
e soil in this land was characterized by a negative net neutralization pote
ntial, and the soil pH was in a slightly acidic pH range (from 4 to 5). The
contaminants were located mainly in the upper soil layers (mainly in the h
orizon A).
Both methods were connected with the initial solubilization of the contamin
ants. Water acidified with sulphuric acid was used as a leach solution. The
solubilization was mainly a result of the activity of the indigenous soil
microflora. This activity was enhanced by suitable changes in the levels of
some essential environmental factors, such as water, oxygen and nutrient c
ontent of the soil. The first method was then connected with the removal of
the dissolved contaminants from the soil through the soil effluents. The s
econd method was based on the transfer of the contaminants into the deeply
located soil horizon B-2, where they were immobilized mainly as a result of
the activity of the indigenous sulphate-reducing bacteria. Their activity
was enhanced by injecting water solutions of organic compounds into the hor
izon B-2 through boreholes located in the relevant experimental plot. (C) 2
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