Spectroscopic analysis of heavy metals distribution in selected traditional medicinal plants and soil in Raya Azebo district, Northern Ethiopia

Abstract

The use of traditional medicine is increasing dramatically worldwide. In Ethiopia, people largely depend on the use of traditional medicinal plants as herbal remedies. However, the effectiveness of medicinal plants is affected by the presence of heavy metals. Thus, this study aimed to evaluate the distribution of heavy metals in selected medicinal plant roots and the soils in which they were grown. A total of five root and soil samples in triplicate were used for analysis. A wet digestion procedure involving the use of a mixture of strong acids was used for the analysis of plant and soil samples. Based on the results, the concentrations of Zn (21.82mg/kg) and Fe (7.78mg/kg) were higher in Solanum incanum and Carissa spinarum plant samples, respectively, than in the other plants. The concentrations of Mn, Cu, and Pb ranged from 1.70 ˗ 4.22mg/kg, 1.34 ˗ 3.43mg/kg, and 0.14 ˗ 0.34 mg/kg, respectively, but Cd was detected only in Carissa spinarum (0.15 mg/kg) and in Solanum incunm (0.21mg/kg). Regarding the contents of the metals in the soil samples, Zn (15.45 ˗ 44.3 mg/kg) is the most dominant metal, followed by Mn (9.54 - 23.07mg/kg), Fe (7.58 ˗ 12.68 mg/kg), Cu (3.16 - 12.55 mg/kg), and Pb (0.14 - 2.85 mg/kg) whereas Cd was detected only in Boyegararsa soil (0.21 mg/kg) and Warabaye (0.65 mg/kg) soil samples. The results indicated that the contents of the metals studied did not exceed the permissible limit for medicinal plants set by WHO/FAO. Further studies should be carried out on the bioavailability of toxic heavy metals in traditional herbal medicines.