The Effect of Sewage Sludge and its Biochars on the Availability and Desorption Characteristics of Copper in a Contaminated Calcareous Soil

The aim of this study was to investigate the effect of different levels of sewage sludge and its biochars on availability and release kinetics of Cu in a contaminated calcareous soil. For this purpose, the sewage sludge and its biochars produced at two temperatures including 400 and 600 0C were added to a contaminated calcareous soil at 0, 0.5 and 1% levels (w/w), and samples were incubated for 5 months. The kinetics of Curelease was determined by successive extraction with DTPA-TEA in periods of 1 to 504 h in the amended and control soils. Results showed that the desorbed Cu from the soils treated with 0.5 and 1% sewage sludge significantly increased (p < 0.05) as compared to the control soil, whereas, the amount of Cu desorbed from soils treated with 0.5 and 1% biochar produced at 400 and 600 0C significantly decreased (p < 0.05), as compared with the control soil. Desorbed Copper from treated soil with 1% biochar produced at 600 0C was reduced 54.2% as compared to the control soil. The comparsion of release rate constants indicated that the highest and lowest desorption rate of Cu were observwd in 1% sewage sludge and 1% biochar produced at 600 0C treatments respectively. Overall, the results demonstrated that the conversion of sewage sludge to biochar is a suitable method for its management and it can be used for stabilization and remediation of Cu contaminated soils.