Geochemistry of soil around a fluoride contaminated area in Nayagarh District,Orissa, India: Factor analytical appraisal

Fluoride contamination in soil was studied in the vicinity of a hot spring in Nayagarh district of Orissa. Both bulk soil from 0 to 30 cm depth and profile soils from 0 to 90 cm depth were analyzed for total fluoride (F_t) and 0.01 M CaCl₂ extractable fluoride (F_ca), major elements, pH, EC and Organic Carbon (OC). High concentrations of both F_t and F_ca were observed in the area surrounding the hot spring and the village of Singhpur. Principal factor analysis (PFA) on the parameters of the bulk soils suggests that two major chemical processes due to three factors, control the soil geochemistry of the area. Factor-1 contributes 37.11% of the total variance and is strongly loaded with Al, Si, Fe, F_tand F_ca, and explains the fluoride enrichment of the soil, whereas the second and the third factors contribute 16.6 and 12.2%, respectively and explain the controlling process of carbonate precipitation and soil alkalinity. Multiple regression analysis of the scores of the factors was performed to derive a fluoride contamination index in soil. The magnitude of the factor effect on the contamination index follows the order of Factor-1 > Factor-2 > Factor-3. The spatial distribution of the contamination index is used to classify the area into highly contaminated, moderately contaminated and uncontaminated zones.