Psidium guajava as a bioaccumulator of nickel around an oil refinery, southern Brazil

To evaluate the potential of Psidium guajava as a biological accumulator of air pollutants, saplings were exposed at nine sites receiving atmospheric emissions from an oil refinery (five within, four outside the industrial area) and another reference site located at the Federal University of Rio Grande do Sul, 27 km from the refinery. Exposures lasted about 3 months each, coincided with the seasons, and totaled five exposures between 2005 and 2006. The following parameters were evaluated: dry weight of leaves, stems, and roots, leaf area, rate of relative height increase, Ni and S contents, maximum assimilation rate, and carboxylation efficiency invivo. P. guajava was found to be an efficient accumulator of Ni, since highly significant differences were observed (P<0.001) between sites within the industrial area and the reference site for all periods of exposure and a significant negative correlation between distance from emission source and Ni content. The S content showed significant differences (P<0.05) only at sites within the industrial area for two exposures. The dry weight, leaf area, rate of relative height increase, maximum assimilation rate, and carboxylation efficiency did not present significant differences for any period of exposure. In view of the above, we conclude that P. guajava is a good bioaccumulator for Ni.