Evaluation of urban tree barks as bioindicators of environmental pollution using the X-ray fluorescence technique

Some chemical elements released in nature due to anthropogenic actions are harmful to living beings, and finding efficient and low-cost ways to measure their presence is a challenge. The major goal of this work was to use the barks of urban trees as bioindicators of the presence of these elements. For this purpose, tree barks of sixteen individual trees were collected, including Ipê (Bignoniaceae Family); Sibipiruna (Fabaceae Family); Pine (Pinaceae Family), in the city of Sorocaba, SP, Brazil, in three different districts. Two samples, one of Ipê and another of Sibipiruna, collected in the Mata Atlântica forest in Juquitiba, SP, Brazil, were used as control samples. They were also analyzed; six soil samples were collected in the same places as the tree barks in Sorocaba. The samples were analyzed using the Energy Dispersion X-Ray Fluorescence Spectroscopy technique. The elements studied ranged from Al to Bi. The results were submitted to univariate and multivariate statistical analysis showing that Sibipiruna presented a high concentration of the element Ca. At the same time, Ipê and Pine showed high concentrations of K. In the identified elements, the probable sources of contamination were pointed out, such as elements from the dust of braking automobiles (Al, Si, S, Ti, Fe, Cu, and Ba), elements from the paint used to paint the asphalt (Si, Ca, Cr and Pb) and elements from the tire tread wear (Al, S, Ca and Zn). From the analysis of soil samples and trees, it was found that there was high pollution by the element Pb in the specimens collected in front of the old Saturnia battery factory, located in the district of Éden in the city of Sorocaba, SP, Brazil (Coordinates: Lat 23K253141 m E; Long 23K7405583 m S).