Tree Bark as a Biomonitor of Heavy Metal Pollution (Case study: Roadside Gardens of Heidareh Balashahr Village in Hamadan)

The study of heavy metals in plants is done with two objectives of studying food safety and application in biological monitoring and elimination of heavy metals from the environment. The aim of this study was to investigate the concentration of heavy metals zinc, copper and lead in the bark of poplar and walnut trees and surrounding soil samples from road of Heidareh Balashahr village in Hamadan. A total of 40 topsoils and tree barks samples were collected from this area. After initial preparation, the samples were prepared using wet digestion method to analyze the heavy metals and the concentration of heavy metals were determined by using an atomic absorption spectrometer (ASS). In order to data analysis, statistical methods, pollution indices and ratio of indices were used. According to the results the Degree of Contamination (CD), Modified Degree of Contamination (mCD), Potential Ecological Risk (PER), Potential acute Toxicity (∑TU) and Integrated Pollution Index (IPI) indices showed low pollution and Pollution Load Index (PLI) and PINemerow indices showed moderate pollution and precautionary zone, respectively. The highest contribution to potential toxicity was 43.8 and 38.05 percent in the soil around walnut and poplar was related to copper. Also, the highest potential environmental risk was related to lead with 52.3 and 58.08 percent, respectively for the surrounding soil of walnut and poplar. Based on these results, there was only a statistically significant difference between zinc concentrations in the two species (p <0.05). Also, significant positive correlations were observed between the Pb contents in soils and those of poplar bark (p<0.05) that indicated Pb in plant increased with increasing Pb in soil and, so poplar is a more suitable species as a biomonitor and lead accumulator. Despite the contaminants caused by road traffic, food safety of the region's agricultural products should be checked in spatial and temporal monitoring, especially for lead and copper.