BIOTESTING OF HEAVY METAL POLLUTION IN THE SOIL

Chemical pollution of the environment increases sharply globally, and one of the most significant indicator of this increasing pollution is the accumulation of heavy metals in the soil. In mobile forms they can enter the food chain, damaging the environment seriously and posing a risk to human health. The subject of this work is justified by the fact, that a plant biotest method representing the toxicity of heavy metals to the ecosystem, characterizing the heavy metal pollution of soils and applying plant parameters is not available. Thus, it was to develop a laboratory plant biotest method and assessing system suitable to characterize heavy metal polluted areas, on test soils contaminated by cadmium, lead and copper, applying perennial rye-grass (Lolium perenne), as test plant. The basis for a plant biotest method suitable to characterize heavy metal polluted soils was the rapid seedling biotest method developed by Nooman & Fuleky (1991/1992). In the experiments the number of heavy metal loading levels was; increased, applying 0-, 0,75-, 1-, 2- 4x loading levels. 1x loading levels were identical for all three heavy metals with "B" (pollution) limit levels, calculated for air dried soil. A 0x loading means unloaded soil with natural heavy metal content. In addition to shoot heights other plant physiological parameter, were tested as well, i.e. green and dry masses and humidity of the shoots, the mass of the roots and heavy metal content taken up by the shoots and the roots were measured. In the test plants used, the increase of the heavy metal content could be undoubtedly correlated to heavy metal loading levels. The greatest impacts of increased heavy metal loading were observed in the heavy metal content taken up by the shoots and the roots. Heavy metal contents taken tip by the shoots can be much more sensitive indicators of heavy metal pollution of soils,. than the numerical values of soil limit levels. Our results with Cd, Pb and Cu loading of test soils have shown that shoot height reduction of perennial rye-grass (Lolium perenne) can be a well treatable and sensitive indicator of heavy metal pollution level of soils, as it is characteristic for the inhibiting effect of heavy metal pollution and for the acute toxicity level as well. Acute toxicities of heavy metal loading could be easily monitored by the decreasing of green mass.