Assessment of the lake Gendabi salt for trace elements and toxic heavy metals by energy dispersive x – ray fluorescence spectrometry

This study is the first to analyze elemental contamination in salts from Tanzania. The study has analyzed samples of salts from Lake Gendabi, located in the northern part of Tanzania to determine the elemental concentrations in salts using EDXRF system. The aim of the study was to assess the safety of Gendabi salt for human consumption. Seventy five salt samples were collected from the Lake Gendabi floor and grouped into five grades (G1, G2, G3, G4 and G5) depending on the position of the salt from the lake shore. G1, G2 and G3 salts are reported to be used as table (cooking) salt while G4 and G5 are used for animal feeding as well as industrial productions. In addition to Na and Cl, concentrations of 17 more elements were determined in all five grades of salt. These included 7 toxic metals which are Al, Ni, Cr, Cd, Pb as well as Th and U which are also radioactive. Other elements were S, K, Ca, V, Cu, Mn, Fe, Zn, Br and I. All toxic elements in G1, G2 and G3 salts were in higher concentrations than the Maximum Tolerable Limits (MTLs) set by International Organizations. This is a concern as the salt is used for consumption in many parts of Tanzania. Furthermore, samples from G1 and G2 salts had percentage impurities of 0.67% and 0.51% respectively. This indicates less ability of the salt to retain iodine as the presence of metal impurities above 0.5% by weight, has been reported to negatively affect the stability of I. The Kruskal – Wallis test showed that, except for Mn, Cu, Cd and I, the mean concentrations of all elements varied significantly ( ) from one salt grade to another. The Spearman test showed that the concentrations of Na, Cl, V, Cr, Ni, Cu, Br and Pb increase with the increase of distance from the lake shore whereas those of Ca, Fe, I, Th and U decrease.