Habitat function of agricultural soils as affected by heavy metals and polycyclic aromatic hydrocarbons contamination.

Ecotoxic activity of soils polluted with polycyclic aromatic hydrocarbon (PAH) and heavy metals (HM) was evaluated in pot and laboratory experiments. Plants and soil microorganisms were chosen as test organisms and six different soil materials were used in the study. The applied levels of HM and PAH were aimed to reflect environmental conditions in the "worst case" situation. Zn(2+), Pb(2+) and Cd(2+) were introduced to the soils as an aqueous solution of the mixture of salts at the concentrations corresponding to 1000, 500 and 3 mg kg(-1), respectively. Mixture of four PAH compounds (flourene, anthracene, pyrene and chrysene) as a CH(2)Cl(2) solution was applied at levels of 10-100 mg summation operator 4PAH kg(-1). Population and activity of soil microflora was evaluated as measured of total bacteria counts, intensity of respiration and enzyme activity (dehydrogenases and phosphatases). Effect on plants was evaluated on the base of the growth (plant at an early stage of their development) and yield (mature plant) measurements. The results indicate that combined effect of PAH and heavy metals on soil microorganisms activity and on some plants at an early stage of their development can be stronger than in soils amended with HM or PAH separately. Reaction of tested organisms was related to soil properties, PAH concentration, time and plant species. Mature plants (maize) were insensitive to the applied levels of both group of contaminants.