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