Spatial Variability of Fluoride in Groundwater and Soils in Some Areas of Arak Plain

Fluoride (F-) is an essential element for human and some animals. The fluoride concentration in irrigation water is an important index for water quality. The objective of the present study was to determine spatial variability of fluoride in groundwater and soils of some areas in Arak plain. Therefore, during two seasons, autumn (2007) and the end of spring (2008), 87 and 92 water samples were collected from the wells, in the study area, respectively. Furthermore thirty soil samples were taken from the same positions. Fluoride concentrations in groundwater and soil samples around Arak city was measured by Ion Selective Electrode (ISE) method. The results show that the average fluoride of water samples during two seasons ranged from 0.3 to 0.06 mg/L which is below the standard level (1.5). These values were suitable for irrigation. Generally, spatial distribution in groundwater and isopiezometry maps indicated that fluoride increased where groundwater flow lines were centralized. Besides, fluoride concentration has increased in the rural zones and discharge areas. Average concentration of fluoride in agricultural and industrial areas were 1.5 and 7.5 mg/Kg respectively. Maximum concentration of fluoride belonged to industrial areas with 26.5 mg/Kg showing significant difference in 1 % scale in comparison with agricultural zone. There was negative correlation between fluoride with lime values and positive correlation with pH.