Avaliação da ecotoxicidade de fenol e fenol degradado por radical ânion sulfato utilizando os organismos girardia tigrina, eisenia fetida e vibrio fischeri

Abstract

Sodium persulfate (PS) photoactivated by solar radiation is responsible for the formation of the sulfate anion radical (SO4-•), a highly reactive species used in advanced oxidation processes (AOPs) for water and soil treatment, in order to degrade persistent organic compounds. The present study evaluated the ecotoxicity of this process applied to phenol degradation, using as test organisms two aquatic bioindicators: Girardia tigrina (planarian) and Vibrio fischeri (bioluminescent bacteria), and one terrestrial, Eisenia fetida (earthworm). For this, a test with planarian was first performed to identify the individual LC50 of the phenol and PS reagents, which resulted in LC50 values of 194.0 mg.L-1 and 396.4 mg.L-1, respectively. The assays using V. fischeri and E. fetida were performed after the phenol degradation assays by PS at dosages of 238 and 2380 mg.L-1 + solar radiation for 6 hours, in addition to the isolated assays using the reagents phenol and PS. In this assay, the phenol degraded by PS (2380 mg.L-1) + solar radiation showed 98% degradation, while at the PS concentration of 238 mg.L-1 it was 53%. The assay with V. fischeri demonstrated that both the isolated and combined assays were capable of inhibiting the bioluminescence of the bacteria; however, according to the method used, the isolated assays with phenol and PS (238 mg.L-1) were not considered toxic to these organisms (inhibition <20%). The phenol degraded by PS (238 mg. L-1) + solar radiation was the one that showed the greatest inhibition (42.67%) even when compared with the phenol degraded by PS (2380 mg. L-1) + solar radiation (24.67%) and the isolated test with PS at a dosage of 2380 mg. L-1 was able to inhibit 28.27%. According to the escape test with E. fetida, the phenol degraded by PS (2380 mg. L-1) + solar radiation was the one that showed the greatest toxicity, with 88% escape, while the phenol and the degraded phenol (238 mg. L-1) showed no significant difference in relation to the control. Thus, it was concluded that the acute toxicity tests with planaria, as well as the tests with V. fischeri and E. fetida demonstrated that the concentration of 2380 mg.L-1 PS is very high, requiring tests with lower PS dosages and longer exposure times to solar radiation to reduce the impacts of the proposed treatment.