Correlation among fluoride and metals in irrigation water and soils of Ethiopian rift valley

Abstract

The levels of fluoride and selected metals in Ethiopian Rift Valley soils and irrigation water in the nearby sources were determined by fluoride ion selective electrode and flame atomic absorption spectrophotometer, respectively. The pH, conductivity, salinity and total dissolved solids in water and soil samples were also determined. Accuracy of the optimized procedure was evaluated using standard addition (spiking) method and an acceptable percentage recovery was obtained. The fluoride concentrations in water samples were found in the range of 0.14-8.0 mg/L which is below the WHO limit of fluoride concentration for irrigation (less than 10 mg/L). The water soluble and total fluorides in soil were 2.3-16 μg/g and 209-1210 μg/g, respectively and are within the ranges recommended by FAO and WHO. The range of metal concentration in soil samples (μg/g dry weight basis) and in water samples (mg/L) respectively were: Na (684-6703, 8.6-67), Mg (1608-11229, 23-67), K (1776-4394, 1.1-20), Ca (7547-22998, 17-267), Cr (9.8-79, 0.07-0.17), Mn (143-700, 0.05-37), Co (50-112, 0.35-1.5), Ni (446-1288, 0.27-41), Fe (12180-32681, 6.0-48), Cu (8.9-45, 0.09-0.25) and Zn (31-89, 0.14-0.56). Fluoride was found to have significant correlation with major trace metals (Fe, Cu and Cr), but the correlation with other trace metals was not significant. © 2014 Chemical Society of Ethiopia.