Efeitos da aplicação de resíduo de perfuração de poços de petróleo no desenvolvimento de plantas e no risco de lixiviação de metais

Abstract

The oil and its derivatives have become not only one of the main primary sources of global energy production nut an input for virtually all industrial sectors, and in the next decades this framework will continue to increase. However, the oil exploration has aggravating factors, such as production of wastes, which have various pollutants mainly due to the used fluid. Among the contaminants, barium and sodium are generally in high concentrations. The storage of such residues in inappropriate locations and without proper treatment enhances the risks of soil, groundwater and living beings contamination. Thus, this study aimed to evaluate the effects of soil application of drilling waste from oil wells in the development and absorption of barium and sodium by sunflower and castor plants, and risks of groundwater contamination. The study was carried out in a greenhouse at Federal Rural University of Rio de Janeiro research area. The soil and waste materials were collected during the drilling of the well 7-MGP-98D-BA. Two experiments were established simultaneously, one with plants and the other in leaching columns. For both tests, the dosages of the residues were determined using guiding values proposed by CONAMA (2009), and they were: control - no application of barium, with natural contents of the element in the soil; and the dosages of 300, 3000 and 6000 mg kg-1 from two residue sources. These dosages are respectively related to an application of 16.6, 165.9 and 331.8 Mg.ha-1 of the dryer residue; and 2.6, 25.7 and 51.3 Mg.ha-1 of the centrifuge residue. In the plants test, two species with potential for biodiesel production were used; sunflower (Catissol 01) and castor bean (Al Guarany 2002). Analyses of growth, dry matter production and elements absorption by plants were carried out. In the column leaching test two redox potential (oxidation and reduction) conditions were tested. The redox potential, pH, the analysis of the pseudo total levels and the soil geochemical fractioning, and the analysis of leachate extracts were monitored. It was observed that in the reduction condition an increase in the barium levels for the most labile fractions, and a decrease in the stable fractions, in both residue sources. There was also more sulfate solubilization, consequently increasing the barium levels in the leachate extracts. In relation to sodium, it was observed that the highest percentages removed in the leachate extracts were found in the centrifuge residue and in the oxidation condition. For the dryer residue, the dosages 2 and 3 affected the growth of plants, whereas in the centrifuge residue, the plants only were affected at the highest concentration, due to high sodium levels. This element showed to be the most critical in the waste. The barium absorption by the sunflower and castor bean plants was not affected by increasing dosages of residue.