The use of soil/sediment suspensions (slurries) instead of exposure to 'dry' soils is the joint nominator for the contact microbiotests that use e.g., soil bacterial populations , photobacteria [36, 43], algae [44, 45], ostracods [46, 47] as well as recombinant luminescent sensor bacteria for heavy metals [24, 48, 49].
Toxicity was analyzed using a battery of microbiotests with species representing different trophic levels (photobacteria, micro-algae, protozoa, rotifers and crustaceans) and biodegradability of each phenol (2.5 mM) was studied with acclimated and not acclimated activated sludge to the phenolic compounds, whereas the efficiency of detoxification was evaluated by residual toxicity of the incubation medium using photobacteria.
The most sensitive tests were crustaceans (Daphnia and Thamnocephalus) and photobacteria (V.
As the content of water-soluble sulphides in V0 and K0 was 42-110 mg/l in the aqueous extract (Table 11), it is possible that the residual toxicity of the neutralized leachates to photobacteria (2.9 and 3.7 TU, respectively; Table 10) was caused by sulphides.
The old semicokes were only slightly alkaline (pH up to 10), and thus the neutralization did not reduce the toxicity of their water extracts to photobacteria (Table 10).
The toxicity of two river waters (Kohtla and Purtse), influent and effluent of Kiviter WWTP, 6 natural leachates sampled from ditches surrounding semicoke heaps, 4 semicoke heap pore waters and 12 groundwaters (mostly from upper horizons and at maximum distance of 500 m from semicoke dumps) was studied with a battery of tests (algae, crustaceans, protozoa, rotifers and photobacteria, Table 12).
In parallel, the toxicity of the leachate to photobacteria was measured .
The two leachates studied contained 78 and 195 mg phenols/L and were toxic to photobacteria, daphnia and rotifers (LC50 1-9%).