Phytoremediation of Hexavalent Chromium in Effluent Tannery Sludge and Chromium Contaminated Soils using Ricinus Communis Plant

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Heavy metal pollution is a global problem of expanding apprehension due to its toxic effects on the environment which in turn adversely affects Flora and Fauna. Tanning industries have a sludge effluent that is highly contaminated with chromium which is mostly disposed in sludge pits hence polluting the environment. Given the use of chromium in the tanning process and handling of solid wastes in tanning industries, there is high chromium contamination both in the soils surrounding tanning industries and high chromium levels in the tannery effluent sludge after treatment process. The objective of this research is therefore to establish the concentration of chromium VI in tannery effluent sludge; determine the chromium phytoremediation potential of Ricinus Communis (castor oil plant) and Compare efficacy of citric acid as a chelating agent in phytoremediation of chromium VI from chromium contaminated soil and tannery sludge. Samples of tannery sludge were collected from Aziz tannery in Nairobi, and the concentration of Hexavalent Chromium determined using Atomic Absorption Spectrophotometer (AAS). The Ricinus communis seeds were be collected from local castor oil bean plant farmers within Kenya, Germinated, and the Seedlings were transferred to trial pots and watered twice a day and weeded as it deemed necessary. On, thirtieth, forty fifth and sixtieth days the plants were harvested from the pots, cleaned using faucet water and deionized water, and isolated into shoots, stems and roots ready for analysis using the AAS. Bio- Concentration Factor (BCF) and Translocation Factor (TF) were calculated to give the indication of the phytoremediation potential of Ricinus Communis plant. The roots of the Ricinus Communis plant planted in the Tannery sludge had the highest Hexavalent Chromium accumulation. Furthermore, out of the six pots, the Hexavalent Chromium concentrations were high at the roots compared to the areal parts in five of the ports after 30 days and on the 45th day the highest concentrations were accumulated in the roots of the plant that were planted on the tannery sludge, mixture of tannery sludge and red soil, and the mixture of tannery sludge, red soil and chelate. This means that the plant can be used for phytostabilization of chromium contaminated soils hence reducing the mobility of the heavy metal by accumulation of the contaminants by the plant roots. Basically, since the translocation factors were all greater than one at the exposure time of 60 days; this means that Ricinus communis plant has potential for phytoremediation by phytoextraction of chromium with exposure time of between 60 to 75 days. This agrees with Reference [1] on the study on stabilization of tannery sludge amended soil using Ricinus Communis where they concluded that Ricinus Communis plant is suitable for growth in heavy metal rich tannery sludge soil vis a vis for phytosytabilization of the heavy metals The Ricinus communis plant, demonstrated potential for phytoremediation of hexavalent chromium by both Phyto stabilization and phytoextraction which may be attributed to its tolerance and considerable biomass production