Comparison of Eluate and Direct Soil Bioassay Methods of Soil Assessment in the Case of Contamination with Heavy Metals

We compared the advantages of eluate and direct soil bioassay methods to reveal the overall toxicity of contaminated soils in a case study with (i) Eutric Fluvisols contaminated with heavy metals; (ii) cultivated Albic Retisols (Loamic, Aric, Cutanic, Ochric) artificially polluted with zinc and lead (550 mg/kg Pb + 880 mg/kg Zn); and (iii) Albic Retisols (Loamic, Cutanic, Ochric) artificially polluted with phosphogypsum (40%). We measured the total and water-soluble species of chemical elements in the samples. Bioassay tests included six different methods. Chemical and biological variables were aggregated by the principal component analysis. It was shown that toxicity values of tested samples in case of eluate test organisms ( Ceriodaphnia affinis, Paramecium caudatum, Scenedesmus quadricauda, and bacterial test system Escherichia coli ) characterized the studied soils as less toxic than direct soil bioassay tests ( Eisenia fetida and Sinapis alba ). Finally, we discussed possible ways to improve the informative value of the ecotoxicological assessment of soils by bioassay tests.