Determination of Heavy Metal Concentrations and Their Potential Sources in Selected Plants: Xanthium strumarium L. (Asteraceae), Ficus exasperata Vahl (Moraceae), Persicaria attenuata (R.Br) Sojak (Polygonaceae), and Kanahia laniflora (Forssk.) R.Br. (Asclepiadaceae) from Awash River Basin, Ethiopia

Abstract

The objective of this study was to determine the concentrations, potential sources and evaluate the risks of heavy metals in selected plants from Awash River Basin, Ethiopia. A total of 57 samples were analyzed from four different plant species. Microwave-assisted digestion was applied to digest the samples and the concentration of nine elements namely: Al, Cr, Ni, Cu, Zn, As, Cd, Hg, and Pb were analyzed using Inductively Coupled Plasma-Mass Spectrometry (ICP- MS) (Thermos X SERIES2). The obtained data were analyzed using Statistical Package for Social Sciences (SPSS IBM version 20). The recorded mean concentration of heavy metals in the plants were 1.934, 0.023, 0.023, 0.045, 0.129, ND, 0.025, ND, and 0.009 mg/kg in Xanthium strumarium L.(Asteraceae); 0.834, 0.036, 0.024, 0.021, 0.090, ND, 0.002, 0.001, and 0.006 mg/kg in Ficus exasperata Vahl (Moraceae); 1.603, 0.018, 0.019, 0.025, 0.133, 0.005, 0.006, 0.002, and 0.012 mg/kg in Persicaria attenuata (R.Br) Sojak (Polygonaceae); and 0.557, 0.010, 0.010, 0.024, 0.098, ND, 0.012, 0.020, and 0.004 mg/kg in Kanahia laniflora (Forssk.) R.Br. (Asclepiadaceae) for Al, Cr, Ni, Cu, Zn, As, Cd, Hg, and Pb, respectively. Pearson's correlation analysis indicated that there was a strong positive correlation between Al–Ni (r = 0.927^**) and Zn–Cu (r = 0.764^**) at α = 0.01 significant level. Principal component analysis (PCA) indicated that the sources of heavy metals in the plants were associated with anthropogenic factors. The mean concentrations of all elements except Cd in Xanthium strumarium L. (Asteraceae) and Pb in Ficus exasperata Vahl (Moraceae) were below the permissible limit of FAO/WHO (2001 /2005).

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