Assessment of Pollution Index (PI) of Cd, Zn, Cu and Pb in the Soil Irrigated with Municipal Wastewater

Environmental pollution with heavy metals and their transfer to plants is an increasing universal problem. In this study، raw and treated wastewaters were reused for potato cultivation under lysimetric condition. Consequently، a completely randomized test was designed، with four irrigation treatments and three replications. The irrigation treatments were categorized as follows: irrigation with raw wastewater (T1)، treated wastewater (T2)، a combination of 50% raw wastewater and 50% fresh water (T3)، and a combination of 50% treated wastewater and 50% fresh water (T4). The soil of each treatment was sampled in order to assess the Cd، Zn، Cu and Pb pollutions on the basis of the Pollution Index (PI) and to analyze the correlation between the mentioned metals in two soil depths. The results showed that the effects of irrigation treatments on PI of Cd، Pb (p ≤0. 05)، Zn and Cu (p ≤0. 01) amounts were significant. The maximum and minimum values of this index were observed in the T1 and T4 treatments، respectively. The ranking of PI magnitude in all treatments was T1> T3> T2> T4. Also، the results showed that the PI values of the mentioned metals except Cu in the soil depth of 0-10 cm was lower than those in the soil depth of 10-20 cm. The maximum Pearson’s correlation coefficient value was observed between Pb and Cu. Also، the values of this coefficient in soil depth of 0-10 cm were more than those in the depth of 10-20 cm (except the values between Pb and Zn and between Cu and Cd). In this study، the PI values of Pb، Zn and Cu، were lower than 1 and the PI values of Cd were between 2 and 3.