Remediation potential of Baobab (Adansonia digitata L.) Seedlings grown in sewage sludge contaminated by Heavy Metals

Abstract

Application of sewage sludge to agricultural land is widely practiced and presumed to be beneficial for plants’ growth. However, sewage sludge is often contaminated by heavy metals, organic pollutants, and pathogens. This study assessed the capacity of Adansonia digitata seedlings to accumulate and distribute heavy metals from sewage sludge into their tissue parts. Respective heavy metals concentrations in soil before and after plantings were Cu (55.68; 26.45), Zn (76.22; 48.06), Pb (28.22; 19.58), Ni (22.76; 19.32), Cd (3.11; 1.49), Cr (41.78; 23.39) and As (5.92; 4.71) in mg/kg and these were higher than those from control soil. Heavy metals concentrations (mg/kg) in roots of plants from sewage sludge and control soils were Cu (3.08- 16.01), Zn (4.25-9.83), Pb (1.21-3.74), Ni (0.33-1.57), Cd (0.17-0.93) and Cr (2.23-6.65) while those of the shoots were Cu (4.61-30.11), Zn (5.88-16.22). Pb (1.41-4.86), Ni (0.27-1.56), Cd (0.09- 0.65) and Cr (3.24-10.01). For most of the studied metals, bioaccumulation factor (BCF) values were more than one and generally higher for Cr, Zn, Cu, and Pb. The significant reduction observed in concentrations of heavy metals in soils before and after planting indicated their enrichment in the plant tissues. Bioconcentration factors indicated that Adansonia digitata can be used as bioaccumulation plant. This study has shown the efficacy and ability of Adansonia digitata to accumulate and distribute heavy metals in its tissue parts.

Keywords: Bioaccumulation, heavy metals, enrichment, sewage sludge