For the entire sampling site, PLI is determined as the nth root of the product of the n CF. This empirical index provides a simple, comparative means for assessing the level of heavy metal pollution.
· Contamination Factor(CF) = C heavy metal / C background
Dividing concentration of each HM in soil by the baseline or background value (concentration in unpolluted soils)
The contamination levels may be classified based on their intensities on a scale ranging from 1 to 6 (0=none, 1=none to medium, 2=moderate, 3=moderately to strong, 4=strongly polluted, 5=strong to very strong, 6=very strong) . The highest number indicates that the metal concentration is 100 times greater than what would be expected in the crust.
in which: Ci is the concentration of an ith element in sample, Cp is the concentration of proxy element in the same sample, Bi and Bp are reference values of ith and proxy, element, respectively. Common proxy elements are Al, Fe, Ti, Sr, etc. EF