PROPOSAL OF SOIL CONTAMINATION LIMITS FOR PERSISTENT ORGANIC XENOBIOTIC SUBSTANCES IN THE CZECH-REPUBLIC

The data about the persistent organic substantes (Dutch list), from 56 0 soil samples (ploughing horizons) have been evaluated. They include mono- and polyaromatic hydrocarbons, chlorinated hydrocarbons (PCB, HC B, DDT and metabolites), styren and oil products. The data have been s tatistically processed (after elimination of samples from Praha and fl uvisols) within two sets: soils from both anthropogenically affected a nd immission-free regions (491 samples), soils from immission-free reg ions of Sumava Mountains and Czech-Moravian Highlands (96 samples), (T ab. I). The upper level of variability of the content of single compou nds has been assessed, based on some procedures (GM.GD(2), empiric per centiles and percentiles derived from the log-normal distribution). Th is reference value derived from the evaluation of the above mentioned two sets is taken for the regional contamination limit, the anthropoge nically diffuse background concentration for the Czech Republic (Tab. II). The exceeding of this reference value indicates the increased inp uts in soils. The concept of our approach is approved by the gained re sults as compared with the similar reference values of German authors (Tab. III). They have no ecotoxicological relevance. Our contamination limits differ both from the old and new Dutch standards, supported by ecotoxicological research.