Study of Changes in Soil Bacteria and Some Heavy Metals in Different Soil Depths in Soil Irrigated with Wastewater

A soil irrigated with wastewater for many years was chosen to collect samples from different soil depths (0-15,16-30, 31-45) cm. Changes of soil bacteria and some heavy metals were determined with different soil depths. Results showed that total bacteria count of surface soil (0-15) cm was higher in soil irrigated with waste water (4.9 x10(6)cfug(-1)soil) while it was (1.5x10(6)cfug(-1) soil) in soil irrigated with river water. Total coliforms ranged from(1.21x10(2)cfug(-1)soil) in surface soil with waste water irrigation and(0.75x10(2) cfug(-1)soil) with river water irrigation. While fecal coliforms were found only in the surface soil irrigated with waste water. The concentration of heavy metals, was affected by continues application of waste water irrigation. These heavy metals decreased with depth due to low mobility in soil. Accumulation of heavy metals occurred in (0-15, 16-30) cm depths. Concentrations of Cd, Pb and Ni in vegetable Crops grown in soil irrigated with wastewater were high. Maximum accumulations of these heavy metals were in Potato, which is considered as a good accumulator of heavy metals.