An evaluation of heavy metal pollution risk in tea cultivation soils of micro-catchments using various pollution indexes under humid environmental condition

Heavy metal contamination risk in agricultural fields has attained considerable importance in recent years especially due to harmful effects on food safety and the ecosystem. The purpose of this present research is to assess the heavy metal contamination risk of some micro-catchments, where tea cultivation has been taken place of Rize province in the Eastern Black Sea Region, by taking into consideration three different approaches. For this aim, 96 soil samples were collected from 29 micro-catchments at a depth of 0-20 cm to evaluate heavy metal concentrations and risk levels of soils. After that, some analyzes were performed to find out the correlation between Cd, Cu, Co, Ni, Zn, Pb and Cr concentrations and physico-chemical properties of soils to determine the risk contamination indices of heavy metal contents and enrichment factor, geo-accumulation index and contamination factors due to natural or anthropogenic effects. According to the study results, the order of the mean heavy metals identified in the soils was determined as Zn > Cu > Cr > Ni > Pb > Co > Cd. On the other hand, according to all three contamination risk models, Cd was identified as the riskiest element in terms of contamination in the catchments, where tea cultivation has been carried out. Also, when the statistical relationship between some physico-chemical characteristic of soils and heavy metals examined, it was identified that a significant positive correlation between clay content of soils and pH, and Cd and Zn, respectively. However, the OM value was positively correlated with Pb and negatively correlated with Co.