The effect of pumice on reduction of cadmium uptake by spinach irrigated with wastewater

Increasing demand for irrigation water and scarcity of fresh water has caused significant increase in the reuse of urban and industrial wastewater throughout the world. Heavy metals in wastewaters are the main factors in the contamination of water and soil. The objective of this study was to evaluate the effect of application of pumice as soil amendment on the uptake of Cd by spinach (Spinach oleracea L.) under irrigation with wastewater (containing 10 mg/L Cd). The experiment was conducted as a completely randomized design in a greenhouse with 3 replications in the research station of Isfahan University of Technology. Different levels of pumice (0, 4% and 8% w/w soil) were added to the soil. Results indicated that the addition of 4% and 8% of pumice in soil, decreased 30.19% and 46.17% Cd uptake in plants, respectively. The transfer factor into roots and shoots of spinach were significantly reduced (p < 0.05) in pumice treatments compared to the control. The percentage of DTPA extractable Cd in soils amended with pumice significantly decreased (p < 0.05) and this resulted in lower Cd accumulation in plants. Irrigation with wastewater containing Cd decreased the yield in comparison to irrigation with freshwater. So, it seems that pumice, as a cost-effective adsorbent, poses potential for immobilization and reduction of phytoavailability of Cd in polluted soils.