Ecotoxicological study of Lithuanian and Estonian wastewaters: selection of the biotests, and correspondence between toxicity and chemical-based indices.

The toxicity of industrial and urban wastewater (WW) samples collected in Lithuania and Estonia was evaluated by using a suite of biological tests comprising the Algaltoxkit F with Selenastrum capricornutum, the Charatox with Nitellopsis obtusa, Daphtoxkit F with Daphnia magna, Thamnotoxkit F with Thamnocephalus platyurus, Protoxkit F with Tetrahymena thermophila and the Microtox with Vibrio fischeri. The Charatox and Thamnotoxkit F tests showed highest relative sensitivity, responding to 80-90% of samples, respectively, and both expressed good discrimination capacity between samples. Principal Component and pairwise correlation analysis allowed to select test-battery consisting of Charatox, Thamnotoxkit and Microtox. The WW toxicity was evaluated by means of cumulative indices such as average toxicity (AvTx) and two indices derived from the PEEP-index (Environ. Toxicol. Water Qual. 8 (1993) 115). In addition to these integrated evaluations of test-battery response, WW toxicity was evaluated according to the most sensitive test (MST) in the battery. The linear regression analysis between cumulative toxicity indices and chemical-based indices (derived from comparison of WW chemical concentrations and their respective maximum allowable concentration) revealed positive linear relationships (r(2)=0.7-0.8), while toxicity evaluation based on the MST was less positively related with chemical analysis data (r(2)=0.5-0.6). Although better coincidence between the toxicity and chemical-based assessments was achieved when information from all tests in the battery was assembled, the prediction of toxicity from chemical data was still limited. In search of suitable test-battery for the screening of certain type of WWs, a preliminary study comprising excessive suite of tests might be useful.

Study of the environmental hazard caused by the oil shale industry solid waste.

The environmental hazard was studied of eight soil and solid waste samples originating from a region of Estonia heavily polluted by the oil shale industry. The samples were contaminated mainly with oil products (up to 7231mg/kg) and polycyclic aromatic hydrocarbons (PAHs; up to 434mg/kg). Concentrations of heavy metals and water-extractable phenols were low. The toxicities of the aqueous extracts of solid-phase samples were evaluated by using a battery of Toxkit tests (involving crustaceans, protozoa, rotifers and algae). Waste rock and fresh semi-coke were classified as of "high acute toxic hazard", whereas aged semi-coke and most of the polluted soils were classified as of "acute toxic hazard". Analysis of the soil slurries by using the photobacterial solid-phase flash assay showed the presence of particle-bound toxicity in most samples. In the case of four samples out of the eight, chemical and toxicological evaluations both showed that the levels of PAHs, oil products or both exceeded their respective permitted limit values for the living zone (20mg PAHs/kg and 500mg oil products/kg); the toxicity tests showed a toxic hazard. However, in the case of three samples, the chemical and toxicological hazard predictions differed markedly: polluted soil from the Erra River bank contained 2334mg oil/kg, but did not show any water-extractable toxicity. In contrast, spent rock and aged semi-coke that contained none of the pollutants in hazardous concentrations, showed adverse effects in toxicity tests. The environmental hazard of solid waste deposits from the oil shale industry needs further assessment.

Toxicological Investigation of Soils with the Solid-phase Flash Assay: Comparison with Other Ecotoxicological Tests.

A new direct-contact toxicity test, the solid-phase flash assay, which utilises photobacteria in direct contact with soil particles during the exposure, was evaluated on four soil samples. Samples HTNT1 and HTNT2 originated from former military sites in Germany, and were highly contaminated with nitroaromatics (approximately 20g/kg), lead and polycyclic aromatic hydrocarbons. Samples LMKW1 and LMKW2, from bioremediation stacks in Germany, were mainly contaminated with mineral oils. The solid-phase flash assay was applied to soil-water slurries, and the results were compared with the toxicity data for soil-water extracts obtained by using various conventional ecotoxicological tests, in which photobacteria, crustaceans, protozoa and algae were used as test organisms. The LMKW1 and LMKW2 samples were not toxic (EC20 > 12.5%) according to all the tests applied, except for the Photobacterium phosphoreum conventional luminescence-inhibition test for LMKW1 (15-minute EC20 = 5.4%(. The HTNT1 and HTNT2 samples were toxic according to all the tests applied, with the majority of EC20 values being lower than 1%. The solid-phase flash assay (1 minute of extraction and 30 seconds of exposure time) gave comparable results to the conventional tests. Therefore, this flash assay could be applied as a fast screening test in parallel with conventional toxicity tests that use soil 24-hour extracts. The flash assay results will be ready by the start of the conventional assays, and could serve as range-finders for these slower and more expensive tests.

Predicting the Toxicity of Oil-shale Industry Wastewater by its Phenolic Composition.

The chemical composition and toxicity of five phenolic wastewater samples collected from the Kohtla-Järve (Estonia) oil-shale industry region were analysed. The total phenolic contents (HPLC data) of these samples ranged from 0.7mg/l to 195mg/l. A total of 11 phenolic compounds were found in the wastewater samples, the most abundant being phenol (up to 84mg/l) and p-cresol (up to 74mg/l). Artificial phenolic mixtures were also composed, to mimic the content of phenolic compounds in the wastewater samples. The theoretical toxicities of these artificial mixtures were calculated by using the toxicities of the individual phenolic constituents to photobacteria (the BioTox™ test) and were assumed to have an additive mode of action. From the BioTox data, the additive toxic effects of phenolic compounds in the artificial mixtures were confirmed to be highly probable. The toxicities of the wastewater samples and their artificial phenolic analogues (mixtures) were studied by using a battery of Toxkit microbiotests (Daphtoxkit F™ magna, Thamnotoxkit F™, Protoxkit F™ and Rotoxkit F™) and three photobacterial tests (Microtox™, BioTox™ and Vibrio fischeri 1500). The wastewaters were classified as toxic (two samples), very toxic (two samples) and extremely toxic (one sample). Comparison of the test battery responses showed that the industrial wastewaters were 2-28-fold more toxic than the respective artificial phenolic mixtures. The photobacterial tests proved to be the most appropriate for screening purposes. This was the first attempt to use a test battery approach in the toxicity testing of Estonian wastewaters. The study showed that the toxicity of oil-shale industry wastewaters could not be predicted solely on the basis of their phenolic composition, since only 7-50% of their toxicity was shown to be due to phenolic compounds. It is true, to a certain extent, that the majority of environmental samples are usually very complex and contain various types of pollutants. As even a full chemical analysis (which is very expensive) can easily miss the constituent(s) with the greatest toxic effect(s), the use of toxicity tests in parallel to chemical analysis should be encouraged.