Toxicity Assessment of Contaminated Soil Using Seeds as Bioindicators

The evaluation soil quality after bioremediation processes solely on chemical data does not include the effects of toxic substances in organisms. Thus, ecotoxicological assays with seeds are applied to assess the effect of toxic substances in organisms according to their germination sensitivity. The objective of this study was to evaluate a contaminated soil with diesel, biodiesel and waste lubricat oil in ecotoxicological bioassays using seeds of Cucumis sativus (cucumber), Brassica oleracea (kale) and Barbarea verna (cress) as test organisms. The sample of contaminated soil was buried to allow contact with microorganisms that are naturally present in the soil and can be capable to biodegrade the contaminant. Each soil sample was removed monthly and the potential toxicity of contaminants was evaluated by examining germination rates according to biodegradation time in soil. The results indicate that the species Barbarea verna is not a good test organism due to its low germination rate. The study suggest that the contact of waste lubricant oil and diesel with the embryo was hampered by the seed coats and the hydrophobicity these substances, preventing the entry of substances which may be toxic to the embryo. Also, Cucumis sativus and Brassica oleracea showed that after two months of biodegradation, biodiesel is the most toxic contaminant during seed development.