Effect of Poplar Sawdust and Its Biochars on the Desorption Process of Cadmium in a Calcareous Soil

Cadmium is one of the most hazardous heavy elements in the environment, and its removal from water and soil environments is necessary and important. In the present study, the effect of poplar sawdust and its biochars at two different temperatures of 300 and 600 0C on the process of cadmium desorption in a silty loam soil was investigated in Lorestan Faculty of Agriculture, in 2021. For this purpose, poplar sawdust and its biochars were added at three levels (zero, 2%, and 4% by weight) to a calcareous soil contaminated with 100 mg/kg of cadmium. Sampling of the treated soils was done 90 days after the soil was contaminated with cadmium and incubated under field moisture conditions. To study cadmium desorption, in different time periods from 5 to 2880 minutes, the samples were extracted by EDTA and the concentration of cadmium in the samples was determined. The results showed that the lowest amount of cadmium desorption was in the 4% sawdust biochar at 600 0C, which showed a decrease of 80.5% compared to the control. Also, cadmium desorption in the sawdust treatment did not show a significant difference compared to the control. Cadmium desorption in all treatments was high in the early times and decreased over time. In other words, 50% of cadmium desorption occurred in the first 2 hours. Based on the R2 (0.94) and SE (0.23), the power function equation was obtained as the best equation predicting desorption of cadmium in the studied soil. Therefore, in this research, the treatment of 4% by weight of sawdust biochar at 600 0C is introduced as the best treatment to reduce soil pollution caused by cadmium.