Soil Spatial Variability of Fluoride as Affected by Land Uses Essay

Abstract— Fluoride (F) is an essential element for life. At low concentrations, it is generally believed that fluoride deficiencies can arise, but at high fluoride concentrations other deleterious effects can certainly transpire. This study was conducted to evaluate F content and its spatial variability in Isfahan province. This area covers different land uses including agricultural, industrial, urban and uncultivated lands. Two hundred and fifty five topsoil samples (0- 20 cm) in a study area of 6800 km ² were collected. Total fluoride and water soluble fluoride were measured. The results of this research showed that two forms of soil F were controlled by intrinsic factors such as parent material and extrinsic factors such as fertilization. The total fluoride concentration in 96% of the data was less than the globule suggested average (200 mg kg†¾Ã‚ ¹) and water soluble fluoride concentration in 72 % of the samples exceeded the suggested averaged(0.5 mg kg†¾Ã‚ ¹). Key words- water soluble fluoride; total fluoride; kriging; spatial distribution I. INTRODUCTION Fluorine is one of the essential micronutrient for both human and animals. It is present in soils, rocks, water and the biological chains of animal and plant lives [13]. The F concentrations vary in relation to many factors such as geogenic and anthropogenic processes. A large number of industries emit F in atmosphere, including brick and tile manufactures, steel and aluminum manufacture and the production of phosphoric acid, super phosphate fertilizer and elementary phosphorus [9]. Application of phosphate fertilizers, sewage sludges and some pesticides also bring F to soil [6] but the majority of any added F becomes fixed by one or more of soil components [11] and F may... ...ater soluble fluoride in the soils were 100.7 and 0.9 mg kg†¾Ã‚ ¹, respectively. Also, the results of this study show that the urban and agricultural activities have significantly increase the concentration of F in surface soils of the study region. The application of phosphate fertilizers and sewage sludge and some pesticides in our study agricultural land bring fluoride to the soil. On the other hands, in urban and industrial regions, fluoride is brought to the soil surface by fall out of particulate fluorides and through absorption of fluorides in rain and snow. But the soils in central Iran are alkaline and calcareous. So, most of the added fluorides to the soil is either effectively fixed by the soil component such as clay, Ca and P. Anthropogenic activities were an important factor controlling the spatial distribution of soil F concentration.