Profile of Essential and Non-Essential Metals in Soil and in Khat (<i>Catha Edulis</i> Forsk) Leaves Cultivated in Southern Region, Ethiopia

Abstract

This study was conducted with the objective of determining the quantity of selected essential and nonessential metals; Co, Mg, Ca, Cu, Mn, Cr, Cd, Fe, Zn and K in the leaf and supporting soil of Khat (Catha edulis Forsk). Samples of three Khat types (Konso, Gidole and Koyra) and soils from their root zone collected from three different sites in southern Ethiopia region were analyzed by flame atomic absorption spectrometry. K in soil and Khat sample were also determined by flame atomic emission spectroscopy. Known weight of oven-dried Khat samples were wet-digested using 2 mL of (69–72%) HNO3 and 2 mL of (70%) HClO4 for 130 min at variable temperatures (120–268 °C). Soil was digested by the procedure, 0.5 g samples of soil were digested with concentrated nitric acid, concentrated hydrochloric acid and hydrogen peroxide, using Kjeldahl digestion block under reflux condenser for 3 h at 300 °C. Both the edible portion of khat leaves and the soils of the study farms showed similar accumulation patterns to some extent, in their contents of the studied macro and micronutrients. Regression analysis and pearson correlation (r) results show a positive correlation Coffecient (R2) values ranging from 0.281 up to 0.991 and for pearson correlation (r) values ranging from 0.244-0.951. Although regressions based on the pooled data from the three Khat types are not adequately correlated with total metal soil levels, better fits were obtained when regression models were used for Konso Khat separately. However, no strong correlations between the leaves and other variables are evident except for Ca and Mg metal contents which have r values of 0.971 and 0.991 respectively with (p<0.01) levels. The concentrations of the metals were also compared with recommended maximum permissible limits and some international reports.