Effect of Elemental Sulphur on Heavy Metals Solubility and Remediation by Plants in Calcareous Soils

Abstract

Sewage sludge application may lead to the accumulation of a number of potentially harmful components, such as heavy metals, in the applied sludge possibly resulting in phytotoxic effects, soil and water contamination, and accumulation of heavy metal in food supplies. A pot experiment was conducted to compare the relative efficiency of elemental sulphur application in enhancing Ph and Cd phyto-extraction, and to increase Ph and Cd desorption from heavy metal-contaminated soil. Two rates of elemental sulphur (S) applied at 0 (SO) and 300 (S300) mmol kg(-1) soil with three rates of each metal at 0, 200, and 400 mg kg(-1) Pb(NO3)(2) and 0, 50 and 100 mg kg(-1) Cd (CdCl2). Six corn plants were grown for 42 days in pots of contaminated calcareous soil. Results indicated that with S application at 300,mmol S kg(-1) soil pH decreased by 0.5 unit, and solubility of both Ph and Cd was significantly increased. The concentration of Fe, Mn, Zn, Cu, Ph and Cd in maize shoots and roots were increased with increasing rates of heavy metals. However, the concentrations of Pb and Cd in shoots and roots were higher with application of S than without S. Root Fe, Mn and Zn uptake rates were higher than those of shoot, whereas Pb and Cd uptake of shoot was greater than that of roots in corn plants. Plant yield was also significantly affected by application of S and heavy metals. With heavy metal addition, the shoot and root biomasses were decreased with rates of heavy metal increase, either with or without application of S. The removal of Pb and Cd by maize uptaken from the soil increased by application of S within a growth period of only 42 days. As a conclusion, it can be said that sulphur application facilitated Fe, Mn, Zn,Cu, Pb and Cd phyto-extraction, and this may provide an effective soil decontamination strategy in calcareous soils.