where Ca and Xa are the concentrations of desired and reference elements in the soil samples while Cb and Xb are the concentrations of desired and reference elements in the earth crust. Reference elements are usually taken as Al, Li, Sc, Ti, Zr, Mn and Fe [29]. In this study, Mn was selected as the reference material being the most abundant element observed in the analyzed soil samples. The[Cb]/[Xb] crust ratio was adopted from Wedepohl [30] compositional values for continental earth crust.
Bioaccumulation Factor (BF) was determined as an indication of metal accumulation in plant. BF value greater than 1.0 indicates high accumulation of metal. BF was calculated to determine the amount of metals accumulated by the plant using the formula shown in Eq. (3).