Heavy metals distribution in different soil series of district Swabi, Khyber Pakhunkhawa, Pakistan

The present research was carried out with the main aim to evaluate the levels of heavy metals in some contaminated or expected to be contaminated by industrial effluents and some non contaminated soils of district Swabi. A total of 30 soil samples were collected from 15 different selected soil series of Swabi area at 0-15 cm and 15-30 cm depths and analyzed for various chemical properties using standard analytical techniques and for extractable heavy metals Zn, Cu, Fe, Cr, Co, Ni, Cd and Pb using Atomic Absorption Spectrophotometer. All soil samples were found non saline having EC values between 0.13-0.56 dsm-1. Soil reaction or pH value ranged from 7.21-8.60 except Mansabdar soil which had pH value of 9.21. It was found that swabi soil was moderately to strongly calcareous in nature, alkaline in reaction having deficient to marginal in organic matter content. Furthermore all soil samples were found almost adequate in Fe, Cu and Zn for most of agriculture crops. The higher concentrations of Ni (22.21 and 21.9 mg kg-1) and Cr (8.02 and 5.11 mg kg-1) at both surface and sub surface were recorded in Gadoom Amazai soils located near ghee mills and many other industries. Higher levels of heavy metals were observed in contaminated soils as compared with non contaminated soils. Decreased in concentration levels of metals were observed in majority of soils with increase in depth. No correlation was found between AB-DTPA extractable heavy metals and soil chemical properties and it might be due to samples collected from different locations with different thermodynamic characteristics.