C - Lublin

adsorbed chemicals to microorganisms, plants and biotest-organisms (Daphnia
magna) remained very low. Mechanisms of the chemical degradation in the ACamended
soil were different.
Biodegradation of DCA. Only a minor reduction in DCA (C 0 =15000 mg/kg)
was found in the untreated control soil after several months and the main DCA
reduction was due to its binding (up to 27%) to soil matrix. Disappearance of DCA
in the treated soil was sharply accelerated. The DCA was microbially degraded
almost totally, that was confirmed by stoichiometric release of chloride-ion and
low accumulation of bound DCA (up to 4%). In spite of some initial population
decreases (from 10 5 to 1 cells/g just after inoculation), the number of the
inoculated strain in soil began increasing and finally reached 10 6 cells/g by 60 d of
incubation. Only trace concentrations of tetrachloroazobenzene were registered in
the contaminated soil after bioremediation, while remarkable amount of the toxic
and persistent metabolit is usually accumulated in DCA contaminated soil.
Biotests with Daphnia magna demonstrated the absent of sharp and chronic
toxicity of this soil after bioremediation. This approach has been successfully
applied for bioremediation of highly contaminated soil after accidental leakage of
herbicide propanil (3,4-dichloro-propianilide) [1,2].
Degradation and binding of TNT. Disappearance of TNT (C 0 =500-2000
mg/kg) was also accelerated after mixing soil with activated carbon, and the largest
effect was at the highest TNT concentration. Within 6 h after AC-amendment,
extractable TNT decreased from 2000 to 1200 in the amended soil compared to
1800 mg/kg in unamended soil (40 and 10% decrease, respectively). After about 7
d, the process slowed but continued until only 4% of the initially added TNT was
detected in the amended soil by 120 d. The final content of total extractable 14 C
(including [ 14 C]TNT and its 14 C-products) in the amended and unamended soils
were 134 and 793 mg/kg, respectively. The content of water-extractable TNT in the
soil sharply decreased to 3% just after AC introduction while its content in the
control was 35%. The initial TNT concentrations in soil solution of the amended
and control soils were 5 and 80 mg/l. The maximum accumulation of TNT
reduction products in amended and unamended soils was similar (about 3% of the
initially added TNT). However, in amended soil they were formed faster
(maximum by 24 d) and finally decreased to 1%, while their concentration in
control remained constant until the end of the incubation. In contrast, the
accumulation of oxidation products in unamended soil was negligible (