Avaliação da toxicidade de formas inorgânicas do arsênio na minhoca Eisenia andrei (Bouché, 1972)

Abstract

Arsenic is a naturally occurring trace element in the environment and its presence and interactions can be dangerous for the biota from anthropogenic activities or natural processes. In the soil, earthworms are key organisms for nutrient cycling and the presence of toxic compounds, such as arsenic, can compromise local ecological processes. This element can be found in the soil in organic and inorganic forms, these being arsenite (As3+) and arsenate (As5+). The objective of the study was to evaluate the toxicity of arsenite and arsenate using the Californian earthworm Eisenia andrei as a model organism exposed in natural and tropical artificial soil (SAT). Acute toxicity tests were performed with increasing concentrations of As3+ and As5+ in order to assess the mortality of earthworms and estimate the lethal concentration 50% (CL50) and 10% (CL10), an escape behavior test and an assay with sublethal concentrations of these contaminants aiming to assess damage to biomolecules (lipids and DNA). The CL50 values for arsenite were 21.27 mg / kg in natural soil and 19.0 mg / kg in SAT and for arsenate they were 76.18 mg / kg in natural soil and above 120 mg / kg in SAT. In the escape behavior test, this behavior was shown to be significantly higher in natural soil and for earthworms exposed to arsenite, while lipid damage and DNA damage were significantly higher in animals exposed to arsenite, but with no differences in relation to the two types of tested soil. The results obtained in the present study show the impact of arsenic exposure on the health of the earthworm Eisenia andrei, especially in the form of arsenite and alert the public authorities that the legal limits should, whenever possible, consider the different chemical species of the contaminants.