Evaluating Eucalyptus Sp. Trees Exposed To Chemical Oxidation and Their Potential To Phytoremediate Organic Solvents.

An industrial site in southern Brazil has soil and groundwater contaminated mainly by chlorobenzene and benzene. The initial remediation plan was to use sodium persulfate (chemical oxidation). However, low contaminant concentrations can still remain, and we are exploring the potential of Eucalyptus urograndis to phytoremediate these pollutants. Before planting trees on the site treated with sodium persulfate, we set up a greenhouse experiment to assess the survivorship of Eucalyptus plants exposed to chemical oxidant. The experiment was designed using sodium persulfate solution with a concentration range of 10%, 1%, and 0% (D.I. water), each one under 2 different pH conditions (normal pH, and high pH), with a total of 6 treatments (n=3). The pH was raised to activate the sodium persulfate by adding NaOH. There was two different application of the solution on pots (30 cm height by 4.5 cm of diameter) of plants, containing sand as substrate. At first, 400 mL of solution was added (1/3 of the pot space), and no mortality was notice after 2 weeks. Then, we did a second application, now 1.0 L of solution (pot filled), and there was mortality 3 days after only for two treatments: 10% persulfate at high-pH-solution (pH= 12.8), and 10% persulfate at normal-pH-solution (pH= 4.8). In conclusion, only if the plants are completely immerse on the sodium persulfate at 10% concentration, rapid mortality will be observed. Secondly, we conducted a phytoremediation greenhouse experiment using Eucalyptus and non-planted control (n=4) exposure to a benzene/chlorobenzene solution. Leachate was collected daily from the bottom of the pot and analyzed via Gas Chormotography-Mass Spectrometery (GC-MS) after extraction from the aqueous phase. Our results suggest that the presence of plants increased loss of contaminant on the environment.  Thus, the results from both experiments favor to use Eucalyptus trees on the Site in Brazil.