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. KEY WORDS: Fluoride, Metals, Water, Soil, Ethiopia Bull. Chem. Soc. Ethiop. 2014, 28(2), 229-244.DOI: http://dx.doi.org/10.4314/bcse.v28i2.7
Highlights
Fluoride has beneficial effects at low concentrations in drinking water, and other sources, when teeth are being formed; fluoride safely strengthens the enamel, the hard outer 'shell' of the tooth
The main objectives of this study were to determine the levels of fluoride in Ethiopian Rift Valley soils including: (i) to correlate the soil properties like pH, conductivity, salinity and total dissolved solid (TDS) with the fluoride contents of Ethiopian Rift Valley soil and (ii) to correlate the fluoride concentration in soil and nearby water sources used for irrigation
The loading of fluoride on the soil arising from the use of the water for irrigation and fluoride from other sources has no negative effect on the human, because the water soluble fluoride is in the range of 2.6-16 μg/g soil which are within range of water soluble fluoride recommendation of FAO, EPA, and WHO [1]
Summary
Fluoride has beneficial effects at low concentrations (less than about 2 mg daily intakes) in drinking water, and other sources, when teeth are being formed; fluoride safely strengthens the enamel, the hard outer 'shell' of the tooth. This, in turn, stops cavities from forming and teeth from decaying. Taken in quantity (just over 2 mg of fluoride) is extremely toxic and dangerous. Fluoride can be one of the most volatile and active harmful chemicals in the body. Against any age group, but its effects are especially harmful to developing children and the elderly. The detrimental effects of fluoride are varied [1]
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