Impact assessment of agricultural activities on heavy metal accumulation in soil

Use of chemical fertilizers, pesticides and sewage sludge in agriculture lands caused the increase of heavy metals concentration in the soils in many parts of the world. The purpose of this article is studying the impacts of agricultural activities on the accumulation of Cd, Co, Cr, Cu, Ni and Pb in the soil. The soil samples were taken by systematic method from agriculture fields with cultivation period of 65, 35 and 20 years in Hamadan province situated in the west of Iran. The results showed a significant difference between the concentrations of heavy metals, except for Pb, in the soil under different cultivation periods. The trend of heavy metal accumulation for Cd, Co, Cr and Cu was exponential, whereas for Ni and Pb, it was quadratic and linear, respectively. Also, based on calculated contamination factor, the soils considered as none and none to medium pollution classes were generally found in the lands with more length of cultivation.