Comparative Study on The Determination of Some Major, Minor-Essential and Toxic Metals From Two Species of Cactus Fruit (Opuntia Ficus Indica and Opuntia Stricta) and Their Supporting Soil Samples Cultivated in Two Zones of Tigray, Northern Ethiopia

A comparative study was carried out for the determination of some selected metals (K, Mg, Ca, Cu, Zn, Ni, Mn, Cd and Pb) in fruits of two cactus species (Opuntia ficus indica and Opuntia stricta) and supporting soil from two zones of Tigray region of northern Ethiopia. After digestion with microwave acid digestion, some selected metals were determined by Flame Atomic Absorption Spectrophotometer. The concentration of metals obtained for these fruits are found to be within the range of WHO and other international guideline limits. Levels of the metals concentration in this study is that, in all the fruit samples, K >Ca > Mg in concentration and the levels of trace metals are, Zn > Mn > Cu > Ni. Concentrations of Cd and Pb are below the method detection limit in all the fruit samples. The metals concentration between the two species (Opuntia ficus indica and Opuntia stricta) cultivated in the same zone are not significantly different (p = 0.05). In the comparison of metals concentration of same species cultivated in different zones, the concentrations of K, Ca and Zn in fruit and soil are significantly higher in Southeastern zone than Eastern zone. Concentrations of Mg in Opuntia ficus indica and soil are significantly higher in Southeastern zone than Eastern zone. The concentrations of Mn in fruit and soil are significantly higher in Eastern zone than Southeastern zone. Concentrations of Mg in Opuntia stricta, concentrations of Ni in both fruits and soil and concentrations of Cu in both fruits are not significantly different in these two zones, but soil of Southeastern zone is significantly higher in Cu concentration than Eastern zone.