Ecotoxicological activity of soils polluted with polycyclic aromatic hydrocarbons (PAHS) - Effect on plants

Contamination of agroecosystems with PAHs may affect an ability of a soil to sustain a natural biocenosis or agriculture and create a toxicological risk to plants cultivated in the area. The aim of this study was to evaluate the ecotoxicological activity of soils polluted with PAHs with the respect to their effect on plants. Three different soils (chernozem, rendzina and brown soil) artificially contaminated with the mixture of four PAH compounds (fluorene, anthracene. pyrene and chrysene) at the levels of Sigma 4PAHs of 1, 10, 50 and 100 mg kg(-1) were used in the study (laboratory bioassays). Three of the tested plant species (wheat - Triticum vulgare Vill. oat - Avena sativa L and maize - Zea mays L) were from the monocotyledonous category and three (tomato - Lycopersicon esculentum Miller. bean - Phaseolus vulgaris L and sunflower - Helianthus annus L.) from the dicotyledonous category. Contamination of the soil with PAHs at the level below 10 mg kg(-1) stimulated rather than inhibited the growth of the plants at the early stages of their development. The lowest observed level of soil contamination with PAH significantly inhibiting (EC20) plant growth (tomato in sandy soil) was about 20 mg of Sigma 4PAH per kg of soil while EC20 values for most of the other plants tested exceeded 100 mg kg(-1). Phytotoxic activity of soils was negatively related to soil organic matter content regulating concentration of PAHs in the soil water phase.