Potential ecological risk assessment of heavy metals in archaeology on an example of the Tappe Rivi (Iran)

Ancient soils may be highly polluted with heavy metals because of intensive anthropogenic activities over the centuries. Soils in the archaeological site of Rivi are an example of an ancient soil that is exposed to heavy metal pollution. The current study focused on pollution levels of potentially harmful elements (Fe, Co, Cu, Cr, Cd and Pb) using various indices in the soil of Rivi in North Khorasan province, Iran. For this purpose, a total of 93 soil samples were collected from different parts of site (n = 5) and the pollution level of heavy metals were analyzed based on the Geo-accumulation Index (Igeo), contamination factor (CF), Degree of contamination (Cd), the Pollution Load Index (PLI), and the individual potential risk (Eri). Pollution indices were determined based on local geochemical backgrounds. Results showed that: The mean concentrations obtained in mg/kg were Cu (18.88), Pb (36.20), Cr (28.14). Co (21.00) and Cd (5.31). Cr showed a partially moderate pollution level, Pb showed a slight pollution level, and Co and Cd showed no-pollution level, compared to the classification standard. Based on the Risk index values, for heavy metals in the study area was ranked in the order of: Pb > Cu > Cr > Cd > Co. Co and Cd of ancient soils were mainly originated from the soil parent material and topography of the study area. Cu was mainly originated from human activities, and Cr and Pb may be originated from both natural and anthropogenic factors in the study area. Results of this study can reveal a long-term exposure of ancient humans to these elements, via their activities, which may have played particular role in environmental-pollution tolerance. Therefore, studying the effects of these potentially toxic elements on archaeologist's health, the results are crucial to identifying and dealing with risk during their excavations.