Cd, Cr, and Co Motion in Soil Treated with Sewage Sludge and Salts of the Metals and their Uptake by Vegetable Crops A Case Study in East Isfahan

Abstract

The concentration of heavy metals in soil is increasing mainly due to the use of fertilizers, pesticides, and urban and industrial wastewaters. Field application of wastewater may contaminate food chains and water resources if environmental standards are not duly observed. The objective of this research was to determine the mass balance and transport of Cd, Cr, Co in a sewage sludge amended calcareous soil. Sewage sludge was applied at 50 t/ha to 4×4 plots in three replications. After 5 years from sludge application, soil samples were collected to a depth of 100 cm at 20 cm increments and analyzed for their total heavy metal concentration. We were not able to recover 100% of the metals added into the soil at a depth of 100 cm. Our results indicate that 14, 38, and 46 percent of Cd, Cr, and Co, respectively, had been lost over five years. The results also show that some of the metals may have moved to depths below 100 cm through preferential flow paths.

Keywords

• Heavy Metal
• Food Chains
• Mass Balance
• Preferential Flow
• sludge