Potencial para o uso da espécie nativa, Baccharis dracunculifolia DC (asteraceae) na fitorremediação de áreas contaminadas por arsênio

Abstract

Arsenic (As) is ubiquitous in the environment under the concentrations of 10 mg kg-1 in non-contaminated soil. The occurrence of anthropogenic arsenic is mainly due to mining activities. As arsenic is highly toxic to soil, water and all biological community, As contamination is a serious environmental problem that requires the use of remediation techniques. On the search for efficient, low cost and simple techniques, plants have been tested for their ability to remove or reduce the availability of this element in the environment. Such technique is called phytoremediation. In this context, to identify potentially suitable species for restoration of contaminated areas, this study used the species Baccharis dracunculifolia as a model, aiming to evaluate (1) the degree of resistance of B. dracunculifolia to the As, and (2) characterize the mechanisms of resistance and sensitivity involved, thus evaluating the potential of this species for phytoremediation. Plant and soil samples were collected from four areas in Nova Lima, Minas Gerais that have histories of arsenic pollution from mine tailings. Experiments were conducted in a greenhouse at the Universidade Federal de Minas Gerais. The treatments consisted of the application of doses of arsenic as sodium arsenate state (Na2HAsO4 .7H2O). B. dracunculifolia individuals were subjected to the following concentrations: 0, 5, 10, 25, 50, 100 and 200 mg L-1As. This study was conducted in two stages. In the first stage, seed germination experiments were conducted to evaluate the influence of different concentrations of As on the germination and early development of seedlings. In the second stage, plants were kept in individual pots with substrate containing sand, soil, vermiculite and organic matter and subjected to the same concentrations of arsenic. After 60 days, the plants were harvested and the dry matter and the contents of As in leaves, steams and roots were determined. The factors of bioacumulation (FBA) and transference of arsenic for the aerial part (FT) helped characterizing the responses of the plants to As. The results showed that in the early stages of seedling development, B. dracunculifolia shows sensitivity to high concentrations of arsenic. The results indicated that the species survived to very high levels of As in soil, demonstrating resistance/tolerance mechanisms to the element, although plants grown in As contaminated soils presented some symptoms of toxicity, reduced growth and changes in nutritional status. More studies should be performed with this species in order to better understand the tolerance mechanisms involved, so that B. dracunculifolia could be included as a candidate for techniques of phytoremediation.