Fluoride Contamination of Groundwater and Skeleton Fluorosis in Central India

In country like India, the groundwater is widely used for drinking purposes. In central India, the groundwater is hard and contaminated with F− and other elements above the permissible limits and found to be linked with prevalence of the fluorosis diseases. In this work, the groundwater quality Balod district, Chhattisgarh, India is investigated for assessment of water quality for drinking purposes. The concentration (n = 50) of F− was ranged from 1.5 14.0 mg/L with mean value of 3.9 ± 0.8 mg/L. The causes of prevalence of skeleton fluorosis in human of the studied area are described.


Introduction
Ground water is an important resource for drinking agriculture purposes.Groundwater uses and applications are often related to its composition, which is increasingly influenced by human activities.In fact the water quality of groundwater was affected by many factors including precipitation, surface runoff, groundwater flow, and the characteristics of the catchment area.The over extraction of groundwater caused huge weathering of the metamorphic rocks.In several regions of the country, the groundwater was contaminated with F − beyond permissible limit of 1.5 mg/L with linking of fluorosis diseases in human [1]- [15].The Balod district, Chhattisgarh, India is a rice producing area, taking multiple crops by using the water resources.The water is hard with contamination of F − , Cl − and Fe at hazardous levels.In this work, the groundwater quality of Balod district (area ≈ 4000 km 2 ) is described.

Study Area
The Balod district included five blocks: Balod, Gurur, Gunderdehi, Dondi Lohara and Dondi.The area of the district is ≈4000 km 2 with population of 1.3 million.The materials i.e. buildings, metals, pipes, etc. are corroded due to acidic nature of water.The residents of the studied area were suffering with the fluorosis diseases due to mineralization of F − .In present investigation, the Balod district of Chhattisgarh state, central India has been selected for groundwater quality studies to assess the contaminants.

Sampling and Hydrological Parameters
The groundwater sampling network, based on water uses and contamination sources is shown in Figure 1.The hydrological parameters (i.e.age and depth) of 50 tube wells were recorded in January 2016.The water sample was collected in the cleaned narrow polyethylene 250-mL bottle in duplicate during January 2016 [16].The physical parameters i.e. temperature (T), pH, dissolved oxygen (DO), reduction potential (RP) and electrical conductivity (EC) were measured at the spot.The samples were dispatched to the laboratory for the analysis by subsequent refrigerating at −4˚C.

Analysis
The total dissolved solid (TDS) was determined by the evaporation method.The total hardness (TH) value of the water was analyzed by the titration method [17].The F − content of the water was monitored by the Metrohm ion meter-781 using the CDTA buffer in a 1:1 volume ratio.The content of other ions were measured by the Dionex ion chromatography-1100 equipped with appropriate anion and cation exchange columns and conductivity detector.The Fe content was analyzed by using the GBC flame AAS.The sources of the contaminants in the water were apportioned by the statistical analysis.

Physical Characteristics of Tube Well and Water
The physical parameters (i.e.age and depth of tube wells) and habitant population were recorded with the help of public health engineering department, and data are presented in Table 1.The total population residing in the studied is ≈130000.The age and depth of tube wells were ranged from 4 -25 Yr and 37 -85 m with mean value of 11.6 ± 1.5 Yr and 50 ± 3 m, respectively.The most of tube wells of the studied area are young with shallow depth.The higher population density is observed in the Balod town.The value of T, pH, DO, RP, EC, TDS and TH of the water (n = 50) was ranged from 23˚C -28˚C, 6.1 -8.6, 10 -12 mg/L, 146 -298 mV, 101 -1278 μS/cm, 470 -3018 mg/L and 60 -732 mg/L with mean value of 25.0˚C ± 0.3˚C, 7.4 ± 0.2, 10.9 ± 0.2 mg/L, 212 ± 7 mV, 506 ± 70 μS/cm, 1345 ± 180 mg/L and 210 ± 35 mg/L, respectively.

Spatial Variation in Water Quality
The spatial variation in physiochemical parameters of the water is shown in Figure 2 and Figure 3.The water was found to be acidic in the Gurur block.The remarkably high content of F − , Cl − , Na + , Mg 2+ and Ca 2+ was marked in the water of Gunderdehi block.However, the water of two blocks i.e.Dondi and Dondi Lohara becomes reddish when exposed to the air due to hydrolysis of the Fe(III) into oxides and hydroxides.

Sources of Contaminants in Water
The correlation matrix of elements in the water of Gunderdehi block is summarized in Table 4.The content of F − ions had good correlation with the 4 NH + , Na + , K + and Mg 2+ ions, indicating existence of F − in the geo media as Barberiite, bararite, ferruccite, sellatite, cryolite, hieratite, etc.Other ions i.e.Cl − , 2 4 SO − , Na + , K + , Mg 2+ and Ca 2+ were partially correlated, showing origin from multiple sources i.e. geogenic, mining, agriculture, etc.

Toxicities
Three elements i.e.F − , Fe and Ca 2+ were found in all locations above permissible limit of 1.5, 0.3 and 75 mg/L, respectively [18] [19].In Gunderdehi block, Cl − was found at hazardous levels, >250 mg/L, may be due to mineralization.The skeletal fluorosis (i.e.hyperostosis, osteopetrosis and osteoporosis) was observed due to long term ingestion of F − contaminated water by the residents of the studied area, Figure 4.

Conclusion
The groundwater of the Balod district, Chhattisgarh, central India was found to be contaminated with Fe, F − , Cl − and Ca 2+ above permissible limits, which rendering water not suitable for the drinking purposes.The higher prevalence rate of fluorosis diseases was observed in the Gunderdehi and Balod blocks.

Figure 2 .
Figure 2. Spatial variation in physical parameters of water.

Figure 3 .
Figure 3. Spatial variation in chemical parameters of water.

Table 1 .
Details of tube wells and population exposed to F − contamination.

Table 2 .
Physical parameters of ground water in January, 2016.

Table 3 .
Distribution of ions in groundwater during January, 2016, mg/L.

Table 4 .
Correlation matrix of elements in groundwater of Gunderdehi block.