Abstract:
An experiment was conducted to study the distribution and accumulation of Pb, Ni, Co, Cu, Zn, Mn and Fe throughout sandy soils treated with industrial wastes. Surface and subsurface soil samples were collected from three sites namely; Aldahy, Almota and Alsenayh, which representing the major agricultural soils of Qassim, central region of Saudi Arabia. These sites have been used for dumping domestic and industrial wastes for more than 20 years to evaporate and infiltrate solid and liquid industrial waste. The obtained results indicated that, the application of industrial wastes resulted in a marked increase in the total amount of studied metals. Maximum concentrations of metals were found in the surface 30 cm of the soil where Fe > Mn > Zn > Ni > Pb > Cu > Co in most cases. Most movement and amount of metals recovered from soil were predominantly limited to the upper 30 cm depth. The DTPA fraction of metals was relatively small comparing either to the total soil content and/or the 0.5 N HNO3 extractable fractions. For example, the average DTPA extractable Pb was highest (3.37 μg g-1) in Almota soils, 2.41 μg g-1 Aldahy soil and 1.08 μg g-1 in Alsenayh soil. The respective Pb values extracted by 0.5 N HNO3 for the three sites were 6.75, 5.37 and 4.49 μg g-1. Total Pb values were 23.23, 21.77 and 17.63 μg g-1, respectively. All the three forms were highest in Almota area and lowest in Alsenayh area. The average Ni content of the three soils was more or less in the same range as Pb. However, total Ni values were 2 to 3 times higher in Alsenayh soils. Though, these values were still low as compared to the contaminated reported levels but it indicated that these have been contaminated with the dumping of industrial waste. The values of Co for DTPA, HNO3 and total extracts were relatively low when compared to Pb and Ni. Average DTPA content was 0.65 μg g-1 for Alsenayh while it was 0.64 μg g-1 for Aldahy and 2.02 μg g-1 for Almota soils. The data shows a high accumulation of these metals in contaminated area. Accumulation rate was highest for Ni, Cu, Co, Pb followed by Fe, Zn and Mn.