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 util ises photobacteria in direct contact with soil particles during the exposur e, was evaluated on four soil samples. Samples HTNT1 and HTNT2 originated f rom former military sites in Germany, and were highly contaminated with nit roaromatics (approximately 20g/kg), lead and polycyclic aromatic hydrocarbo ns. Samples LMKW1 and LMKW2, from bioremediation stacks in Germany, were ma inly contaminated with mineral oils. The solid-phase flash assay was applie d to soil-water slurries, and the results were compared with the toxicity d ata for soil-water extracts obtained by using various conventional ecotoxic ological tests, in which photobacteria, crustaceans, protozoa and algae wer e 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 t ests applied, with the majority of EC20 values being lower than 1%. The sol id-phase flash assay (1 minute of extraction and 30 seconds of exposure tim e) gave comparable results to the conventional tests. Therefore, this flash assay could be applied as a fast screening test in parallel with conventio nal 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 r ange-finders for these slower and more expensive tests.