O uso de Tillandsia recurvata (L.) L. como biomonitora de zinco (Zn) atmosférico na área urbana de Londrina, PR

Abstract

The urbanization and the natural and constant growth of cities, especially vehicle and industry expansion, causes several environmental disturbances, such as deforestation, threat to wild populations, and the continuous atmospheric and environmental pollution. This situation demands from the government preventive and regulatory actions, as well as pollution mitigating. Tillandsia recurvata (L.) L. is an aerial epiphytic bromeliad that lives on trees or telephone wiring. Its body is formed mainly by linear leaves profusely covered with absorptive trichomes, that take out nutrients directly from the atmosphere. This capability has proposed the use of epiphytic plants as air pollution biomonitors. T. recurvata is very common and abundant in Londrina and for this reason this species was selected to carry out a monitoring study of air pollution by zinc. In this study, five sites from different areas were chosen to monitor air pollution by zinc, based on the vehicular traffic variation as well as the presence of industries. Two sites were set up in residential areas with light traffic flow, one site was set up in the central area where the traffic flow is heavy and two other sites in the industrial areas. For every site 5 points were determined for sample collection. Three composite samples per site were collected from the tree branches at 1,5 to 2,5 m from the ground, each composed by two or three individuals. Prior to chemical analyses, the samples were manually cleaned by removing extraneous materials and oven dried at 70°C until reaching constant weight. After this procedure, the samples were placed to muffle kiln to produce the ashes. Fifty mg of the ashes were accurately weighed and kept in the refrigerator in polystyrene test tubes with nitric acid (HNO3) for 72 hours. The solution was filtered and submitted to determination of zinc by flame atomic absorption spectrometry. The Zn concentration ranged between 0,4255 mg.g-1 to 3,8936 mg.g-1, reaching levels significantly higher than those listed as toxic to grown plants. The obtained data also showed that the residential sites presented lower concentration for Zn and the highest concentrations were observed at the central area, where there is a higher vehicular traffic, what can be associated to the presence of anthropogenic emission sources. The possible deterioration of the vehicle’s fuel tanks migth contributes to release Zn to the atmosphere. The results indicated a promising potential of these species as biomonitors of air pollution as well as the need for monitoring the quality of the air in Londrina.