Determination Of Fluoride And Selected Metals In The Soils Of Ethiopian Rift Valley And Irrigation Water In The Surrounding Area

The occurrence of dental and skeletal fluorosis among the population in the EthiopianrnRift Valley provided the motivation to investigate occurrence of fluoride in soil andrnwater. The objective of this study was to determine the levels of fluoride in Ethiopian RiftrnValley soils and the nearby irrigation water sources and the correlation of fluoride withrnmetals. Nine soil samples from the surface horizon (0-20 cm) depth and water samplesrnwere collected from high fluoride zone of Ethiopian Rift Valley and one controllingrngroup collected from the College of Natural Sciences (Arat Killo Campus), Addis AbabarnUniversity. The sample was collected by random sampling technique. The soil samplesrnwere air dried, grinded, sieved and weighed, then measured for both fluoride and metalsrncontent. The pH, conductivity, salinity and total dissolved solid in water and soil samplernwere also measured. Fluoride determination was made by fluoride ion selective electrodernand metal determination by flame atomic absorption spectrophotometer. The validationrnof optimized procedure was evaluated using standard addition (spiking) method and anrnacceptable percentage recovery was obtained. The fluoride concentration in water samplernwas found in the range of 0.143-8.03 mg/L which are below the WHO limits of fluoridernconcentration for irrigation (less than 10 mg/L). The water soluble and total fluorides inrnsoil were 2.32-16.2 μg/g and 209-1210 μg/g, respectively. The mean metal concentrationrn(μg/g dry weight basis) range in soil samples and mg/L in water samples respectivelyrnwere: Na (684-6703, 8.64-67.3), Mg (1608-11229, 22.7-66.7), K (1776-4394, 1.11-20.3),rnCa (7547-22998, 16.7-267), Cr (9.79-79.3, 0.071-0.169), Mn (143-700, 0.048-37.2), Corn(50.3-112, 0.354-1.48), Ni (446-1288, 0.274-40.9), Fe (12180-32681, 6.04-47.7), Curn(8.85-45.4, 0.088-0.251) and Zn (30.5-89.2, 0.144-0.562). Fluoride was found to havernsignificant correlation with major metals (Fe, Cu and Cr), but the correlation with otherrntrace metals were not significant.rnKEYWORDS: Fluoride, Metals, Water, Soil, Ethiopian Rift Valley

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