Detection of genotoxic effects of heavy metal contaminated soils with plant bioassays

Aim of the present study was the development of a bioassay which enables th e detection of genotoxic effects of heavy metal contaminated soils. In the first part of the present study, the data base on metal effects in plant bi oassays was extended. Four metal salts, namely Cr(VI)O-3, Cr(III)Cl-3, Ni(I I)Cl-2 and Sb(III)Cl-3 were tested comparatively in MN tests with pollen te trad cells of Tradescantia clone #4430 and in meristematic root tip cells o f Vicia faba. With Cr6+ and Ni2+, clear-cut dose-effects were observed in a range between 0.75 and 10.0 mM, whereas this was not the case with Cr3+ (r ange tested 1.25-10.0 mM) and Sb3+ (range 0.30-5.25 mM). In Vicia, negative results were obtained with the four metal salts under all conditions of te st. To compare the mutagenic potencies of the metals, the increases of the regression curves (k-values) were calculated, they indicate the number of M N induced per mM in 100 tetrad cells. The corresponding values for Cr6+ and Ni2+ are 0.87 and 1.05, respectively. It appears that the Tradescantia sys tem is in particular sensitive towards those metal species which cause DNA damage in animals and man such as Cr6+, Cd2+, Ni2+, and Zn2+, whereas no cl ear positive results were obtained with less harmful metal ions such as Cu2 +, Cr3+ Or Sb3+. In the second part of the study, the mutagenic effects of four metal contaminated soils and of two types of standardized leachates (p H 4.0 and pH 7.0) of these soils were tested in Tradescantia and in Vicia. In addition, chemical analyses were carried out to determine the metal conc entrations in the soils and in the extracts. Two of the samples contained h ighly elevated levels of various metals (Zn, Pb, Cu, Cd, Sb, As), one soil came from the Central Austrian Alps and contained high As levels only. Dire ct exposure of Tradescantia plants in the soils resulted in a drastic incre ase of MN frequencies over the background. The lowest effect was seen with the Slovakian soil which contained in particular Sb and As (4.5-fold increa se over the background), with the other soils, the induced frequencies were 11-15-fold over the control values. On the contrary, negative results were obtained upon exposure of Tradescantia cuttings in the leachates and upon implantation of germinated Vicia beans in the soils. The results of the pre sent study indicate that Trad-MN assays with direct exposure of intact plan ts is an appropriate method which enables to detect genotoxic effects of me tal contaminated soils in situ. This simple and fast biomonitoring assays m ight be a valuable supplement to analytical analyses of contaminated soils. (C) 1998 Elsevier Science B.V. All rights reserved.