EFFECT OF SOIL POLLUTION WITH POLYCYCLIC AROMATIC HYDROCARBONS ON MAIZE BIOMASS YIELD AND ACCUMULATION OF SELECTED TRACE ELEMENTS

The research was conducted to assess the effect of artificial soil pollution with polycyclic aromatic hydrocarbons on the amount of produced maize biomass and the accumulation of selected trace elements. Benzo(a)pyrene (BaP), chrysene (Ch) and fluorene (Fl) were added to soil in the liquid form (dissolved in dichloromethane DCM) in doses of 0.1 mg kg(-1) d.m. and 10 mg kg(-1) d.m. The experiment comprised: the control (C) soil with the natural content of the studied PAHs and without a mineral salt supplement; object 0 - soil with the natural content of PAHs and a mineral salt (NPK) supplement, object - I soil with a DCM and mineral salt supplement, object II - soil with a supplement of 0.3 mg PAHs per kg of soil d.m. (0.1 mg BaP + 0.1 mg Ch + 0.1 mg Fl) + mineral salts, the amount of introduced PAHs was equivalent to an elevated content; object III soil with an addition of 30 mg PAHs per kg of soil d.m. (10 mg BaP + 10 mg Ch + 10 mg Fl) + mineral salts, the quantity of PAHs was equivalent to very strong pollution. The test plant was cv. San maize. The dried biomass was crushed in a laboratory mill and mineralized in a chamber furnace (450 C, 5 h). The residue was dissolved in diluted nitric acid 1:2 (v/v). The content of the trace elements (Zn, Cu) in the solutions was assessed with the ICP-AES method on a JY 238 Ultrace apparatus. The quantity of absorbed trace elements was derived from the biomass amount and the content of these elements in the biomass. On the basis of the total maize biomass (shoots and roots), the tolerance coefficient was computed as a ratio of the yield of the plant dry mass in objects C, I, II and III to the yield in the object where NPK medium was introduced to the unpolluted soil (object 0). The pollution coefficient was calculated from on concentrations of the elements in the plant shoots and as a ratio of the elemental content in plants from objects C, I, II and III to the content in object 0. The translocation coefficient was calculated as a ratio of the element content in plant shoots to the content in roots. Soil pollution with the analyzed aromatic hydrocarbons did not inhibit either the growth or the development of maize roots or shoots. The biggest amount of biomass was obtained in the object where the soil was characterized by an elevated content of the analyzed aromatic hydrocarbons. The value of the tolerance index in the objects where the stressor had been introduced was above one, which indicates no effect of soil pollution with PAHs on the plant biomass quantity. The value of the tolerance index below one was achieved only in the control biomass. A significantly higher content of Cu and more of this element absorbed by maize shoots were determined in the objects where dichloromethane and polycyclic aromatic hydrocarbons had been introduced to the soil in comparison with the unpolluted objects. The values of maize shoot biomass contamination with Zn and Cu were visibly higher in the objects where the soil was polluted with aromatic hydrocarbons in comparison to the values obtained in the object where only the mineral medium was supplied to the soil. A similar dependency pertained to the translocation coefficient of zinc and copper.