In this work, we collected samples of lichens from the oaks of Pădurea Troianul, in the area of Teleorman county, to analyze the air quality, using the lichen biodiversity index and its determining factor. We transplanted them to the points to be monitored and analyzed them to detect and quantify the concentration of heavy metals or other toxic substances accumulated in the lichen biomass. This research was conducted at transplant sites, where five sample sites were chosen. We investigated the concentrations of the heavy metals Cd, Pb and Hg, making a comparison between the concentrations indicated by lichens and conventional measurements. The sampling, observation and analysis of lichens, we carried out in the months of September, October and November 2021, because in September the temperatures are higher and the degree of precipitation is lower than in November, so we followed a development of lichens covering different periods in terms of temperature and humidity. The comparison was made starting from the contamination factors obtained and measured in the sampling station. The application of the biomonitoring method allows obtaining an exact index of the purity of the atmosphere based on the tolerance of the transplanted lichens, the results being obtained quickly. Keywords: bioindicators; lichens; heavy metals; transplantation; pollution sources.