Alkaline biosolids and EDTA for phytoremediation of an acidic loamy soil spiked with cadmium

A greenhouse experiment was conducted to investigate the growth of Brassica juncea and Cd phytoextraction in a mimicked Cd contaminated acidic loamy soil amended with alkaline biosolids, prepared from sewage sludge and coal fly ash, in the presence and absence of EDTA at 2 mmol kg−1. The acidic loamy soil was spiked with 0, 5, 20, 50 and 100 mg Cd kg−1 in the form of CdCO3 and then amended with 4% alkaline biosolids (w/w). Alkaline biosolids and 0.12% CaCO3 amendments resulted in a higher biomass than unamended soil spiked with 20 mg kg−1 Cd where plants did not survive and of the two amendments, alkaline biosolids amendment had higher plant dry weight yield and phytoextraction of Cd. Adding 2 mmol kg−1 EDTA to alkaline biosolids amended soil significantly increased the solubility of Cd ions by 9- to 29-fold, but plant Cd accumulation decreased by a factor of 24–48%. The results indicate that alkaline biosolids amendment is an effective approach for assisting growth of B. juncea and phytoextraction of Cd from the contaminated acidic loamy soil, but further application of chelating agents did not enhance the phytoextraction efficiency of Cd.