Determination of phytotoxicity of soluble elements in soils, based on a bioassay with lettuce (Lactuca sativa L.)

In this work the different concentrations of soluble elements in soils from natural (peridotitic soils) and anthropogenic (soils affected by a pyrite-mine spill) origin, are used to determine the phytotoxicity in lettuce (Lactuca sativa L.). The solutions are obtained from soil:water extracts (1:1), having neutral pH and high concentrations of As, Pb, Zn, Mn, Co and Ni, with values exceeding the toxic level for soil solution [Bohn HL, McNeal BL, O'Connor GA. Soil Chemistry, Wiley Interscience. Wiley & Sons, New York, 1985]. The variables evaluated are: Seed Germination (SG), Root Elongation (RE), Germination Rate (GR) and Root Necrosis (RN). The most sensitive variables in the bioassay with these solutions are GR and RN, in these cases the solution causes a reduction of 44% and 67%, respectively, in relation to control (distilled water). The test using soil–water solutions is sensitive and reproducible to determine phytotoxicity in lettuce caused by potentially pollutant elements in soils.