Ecotoxicological Hazard Assessment of Solid-Phase Samples

Abstract:

14 samples originating from Estonia, collected from the oil-shale region (7), oil-polluted sites (4), presumably non-polluted areas (2) and 1 sediment sample from the harbor were studied for the toxicity and presence of the priority pollutants. The soil aqueous extracts were analyzed with a test battery of organisms of different trophic levels (photobacteria, crustacea, algae and protozoa). Particle-bound toxicity was evaluated using photobacterial Flash-Assay. The microbiological activity of the soils was evaluated by the total number of heterotrophic bacteria, dehydrogenase activity and ATP content in the soils.

The soils were extracted for 24 h (1 part of soil+3 parts of water) and extract/slurry exposed at 50% to the test organisms. The extract/slurry was considered toxic when its L(E)C20

Concentrations of heavy metals, oil products and PAHs in the soils were analyzed and compared to the Estonian permitted limit values. In general there was a correlation between the level of the pollutants and toxicity of the soils. The control soils chosen (one from the oil-shale region) proved clean both, chemically and toxicologically. Within 10 toxic samples in 2 soils the concentration of heavy metals/oil products/PAHs did not exceed the permitted level for the usage in the living zone.

The Flash-Assay indicated the presence of particle-bound highly adsorbed toxicants in 4 soil samples (all from the oil-shale region). For two of these soils the solid-phase Flash-Assay was the only test in the battery indicating the toxicity.

The test battery applied was sensitive, contained organisms of different trophic levels and yielded additional information (to the chemical data) on the toxic hazard of the polluted soils. The comparison of the toxicity of the soil slurries and extracts enabled to distinguish between the particle-bound and water-extractable toxicities that is important when the different exposure routes are assessed.