Saturday, 15 July 2006

Evaluation of the Fitorremediation in Soil Polluted by Diesel.

Osmar R. Brito, Alex G. Pavanelli, Carmen L.B. Guedes, Lucimara J. Koga, and Rafael M. Brito. UEL, Dept of Agronomy, PB 6001, Z C. 86051-990, Londrina, Brazil

Petroleum and its derivatives have been causing contamination of the soil in several areas in the world. Different alternatives have been proposed to minimize the pollutant effects of these products, however, most of the time the costs are high. Among the lower cost alternatives the biorremediation and the fitorremediation are proposed. The fitorremediation is a method that can be used to clean places with superficial and moderate contamination. This technology is based on the stimulation of the soil microorganisms by the plant roots or in the direct capture of the pollutant and integration to the metabolism. The study was carried out with the objective of evaluating the potential of some vegetable species of common occurrence in the environment to remedy polluted soils with commercial diesel. The experiment was installed in greenhouse atmosphere, being used vessels with capacity of two kg of soil. Sandy soil collected of the surface layer of 0-20cm was used. The studied treatments resulted of the combination of six vegetable species jack bean (Canavalia ensiformis), tanzania grass (Panicum maximum Jacq cv Tanzânia), finger millet (Eleusine coracana) brachiaria (Brachiaria decumbens), jamaican crabgrass (Digitaria horizontalis) and showy crotalaria (Crotalaria spectabilis)) and five soil contamination levels with diesel (0 - 1 - 2 - 3 and 4% volume/mass). Each treatment was repeated four times. A completely randomized design was used. Diesel aromatic components content in the polluted soil was accomplished through analysis by synchronous fluorescence spectroscopy of the soil extracts. The profile of the spectra was evaluated at 0 (installation date) and 45 days after the seed sowing in the soil with 1 and 2% of contamination. The aerial part dry matter production of the studied plants varied significantly with the species and contamination levels of the soil with diesel. Those variations can be attributed to the genetic and morphologic characteristics of each species, as well , the certain individual resistance of each one of them. The jack bean, tanzania grass , finger millet and brachiaria were the species that presented the largest aerial part dry matter production, in the control and in the polluted soil with up to 1%. In soil with 2% of contamination only the jack bean and jamaican crabgrass survived and maintained the production of aerial part biomass. For 4% of contamination, emergency was not observed for none of the tested species. Except for the showy crotalaria, the other tested species presented effect on the polluting diesel of the soil, reducing the amount of composed with one and two aromatic rings. Key words: Fitorremediation, diesel, HPAs.

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