Influence of Humic Acid and Superabsorbent Usage on Lead Phytoextraction from Contaminated Soil by Brassica napus L.

Phytoextraction can provide an effective in situ technique for removing heavy metals from polluted soils. The objective of this study was to investigate effects of humic acid and superabsorbent on phytoextraction of lead from contaminated soil by Brassica napus L. (i.e., rapeseed). A pot experiment was carried out in a completely randomized block design with three replications in a greenhouse using Pb contaminated soils with 17, 417 and 817 mg Pb.kg(-1) soil. Humic acid (0 and 125 g in 7 kg soil) and superabsorbent (0 and 5 g in 7 kg soil) were applied to lead-contaminated soil. Then, seeds were planted. Results showed that root and shoot dry weight of rapeseed was not affected by increasing lead concentration up to 817 mg.kg(-1) even with addition of humic acid and superabsorbent. Lead concentration in roots was enhanced significantly (p < 0.05) with humic acid usage. Uptake of lead in roots and its translocation to shoots also increased with increasing total lead concentration in soil. Superabsorbent application seemed to be beneficial for in situ remediation of soil via adsorption of the toxic metal on its surface and preventing movement in the soil profile. It decreased uptake of lead in to the plant and reduced phytoextraction efficiency.