C - Lublin

BIODEGRADATION OF ORGANIC CHEMICALS IN SOIL IN THE
PRESENCE OF ACTIVATED CARBON
Vasilyeva G.K., Strijakova E.R., Subocheva S.A., Nikolaeva S.N.
INTRODUCTION
One of the reasons for low effectiveness of soil bioremediation is the high
toxicity of chemical contaminants to microbes and plants. The amendment to soil
with some natural adsorbents can reduce chemical toxicity. Activated carbon (AC)
is one of the best adsorbents for many organic chemicals because of its
hydrophobicity, high specific surface, and microporous structure.
The objective of this research is to demonstrate the reduction in toxicity of
three classes of pollutants (chloroanilines, polynitroaromatics and polychlorinated
byphenils) and to study mechanisms of their accelerated biodegradation and
detoxification in soil in the presence of activated carbon.
RESULTS AND DISCUSSION
Laboratory experiments with 3,4-dichloroanilines (DCA), 2,4,6-tirinrotoluene
(TNT) and polychlorinated biphenyls (PCB) were conducted with several types of
soil from Russia and the USA. Soil samples were artificially or naturally
contaminated with these chemicals with the initial concentrations from 500 to
15000 mg/kg. Some samples were inoculated with microorganisms able to degrade
these chemicals (e.g. Pseudomonas aeruginosa reducing TNT and some
commercial rizosphere microorganisms degrading PCB) or with strains able to use
these chemicals as a sole source of carbon, nitrogen and energy (Pseudomonas
denitrificans and other strains growing on DCA). A fractionated analysis of the
soil was carried out to determine water extractable, solvent extractable and
unextractable (bound) fractions of the chemicals. HPLC, GC and chromatomassspectrometer
were used for analytical determination of the chemicals and their
metabolites in soil.
It was demonstrated that these microorganisms could grow in highly
contaminated soils and transformed the chemicals only after soil amendment with
appropriate brand and dose of activated carbon. The adsorbent maintained low
toxic concentrations of the chemicals in soil solution to degrading microorganisms
and plants. Meantime the adsorbed chemicals were mostly available to degrading
microorganisms, however the rates of degradation of the chemical residues were
slower than those at the beginning of the process. Nevertheless the toxicity of the
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