Phytoextraction of heavy metals and ultrastructural changes of Ricinus communis L. grown on complex organometallic sludge discharged from alcohol distillery

Abstract

The safe disposal and eco-friendly management of distillery sludge discharged after anaerobic digestion of spent wash have become a serious global concern. The present paper aims to investigate the heavy metal phytoextraction potential of Ricinus communis L. thrive on dumped distillery sludge, which was slightly contaminated by heavy metals and organometallic co-pollutants. The results of physicochemical analyses of distillery sludge revealed the presence of high amounts of Fe (62856.32 mg kg −1 ), Zn (178.64 mg kg −1 ), Cu (648.39 mg kg −1 ), Cr (2.32 mg kg −1 ), Cd (1.89 mg kg −1 ), Mn (121.42 mg kg −1 ), Ni (14.32 mg kg −1 ), and Pb (18.51 mg kg −1 ) along with complex co-pollutants. The major recalcitrant organic pollutants detected by GC–MS/MS technique were octadecadienoic acid, 2,3-bis[(TMS)oxy]propyl ester; stigmasterol TMS ether; β -sitosterol TMS ether; docosanoic acid, TMS ester; and heptadecane, 2,6,10,15-tetramethyl. The phytoextraction potential revealed higher accumulation of Fe followed by Cu, Zn, Mn, Ni, and Pb, in root and shoot of R. communis L. It was also noted that the bioaccumulation factor (BAF) and translocation factor (TF) of all tested metals were found to be <1 and >1, respectively which showed strong evidence for high hyperaccumulation and translocation capabilities of this plant. Furthermore, the ultrastructural study of root tissues of R. communis L. showed the formation of multi-vacuoles, multi-nucleolus, and deposition of metal granules in the cell wall and on the plasma membrane’s periphery of roots as adaptive characteristics of plants thriving at organometallic contaminated sludge dumping site. Thus, the study showed a strong indication for the application of Ricinus communis L. as a biotechnological tool for in-situ phytoextraction and restoration of organometallic contaminated sites. • Toxic recalcitrant organic and inorganic pollutants from distillery sludge were detected. • Ricinus communis L. has the potential for phytoremediation of distillery waste. • TEM observations revealed variable heavy metal accumulation strategies. • The study concludes the discharge of sludge is toxic to ecosystem. • Findings will be helpful for monitoring and management of waste contaminated sites.