Influence of perlite/biosolid composition on growth and uptake of Cd and Mn by radish (Raphanus sativus L.) under greenhouse conditions

The effects of different perlite/biosolid compositions upon the uptake of Cd and Mn, and the growth of radish plants (Raphanus sativus L) was investigated by using inductively coupled plasma optical emission spectroscopy, and inductively coupled plasma mass spectrometry (ICP-OES and ICP-MS). Mn and Cd were added in soluble forms to perlite/biosolid compositions. Notably, Mn concentrations in different plant parts were found to increase with increase in biosolid compositions, in the order [Mn](leaves) > [Mn](shoot) > [Mn](roots). This is plausible for Mn, in conformity with the essential role Mn plays during photosynthesis, in metabolic processes, and oxidation-reduction processes in cells. Results indicate that Mn concentrations in plant parts increased up to similar to 50% (wt/wt) perlite/biosolid application rates. In contrast the Cd uptake concentrations in plant parts decreased in the order [Cd](roots) > [Cd](shoots) > [Cd](leaf). Thus, toxic Cd tends to be sequestered in the roots vis-a-vis Mn that is translocated to the leaves. These results suggest that radish plants sequester Cd in the roots. Biosolids therefore play an important role in sequestering and binding of Cd. The observed concomitant increase in biomass yields implicates the rich contribution of N and P from biosolids. The results from the greenhouse experiments lead to the conclusion on the role played by the biosolids in cleanup and remediations for Cd and Mn, which increased in plant parts with composted wastewater sludge-compositions.