Assessment of Groundwater Quality in Central India

The groundwater is widely used for irrigation of rice crops. The overuse of groundwater causes depletion of the water quality (i.e. enormous increase in conductivity, hardness and ion and metal contents, etc.) in several regions of the country and world. In this work, the quality of the groundwater in the densestrice cropping area, Saraipali, Chhattisgarh, Central India is discussed. The water is sodic in nature with extremely high electrical conductivity. The mean concentration (n = 30) of F−, Cl−, 3 NO − , 2 4 SO − , 4 NH + , Na+, K+, Mg2+, Ca2+ and Fe in the water was 1.2 ± 0.2, 98 ± 31, 46 ± 15, 56 ± 9, 19 ± 4, 206 ± 25, 9.2 ± 2.3, 39 ± 6, 114 ± 19 and 1.7 ± 0.6 mg/L, respectively. The sources of the contaminants are apportioned by using the factor analysis model. The suitability of the groundwater for the drinking and irrigation purposes is assessed.


Introduction
The urban groundwater has emerged as one of the world's most challenging issues due to large users and contamination with chemicals of geogenic and anthropogenic origins [1].The quality of available groundwater was degraded enormously by enhancing conductivity, alkalinity, hardness and contaminant levels [2]- [15].Hence, in this work, the groundwater quality of the rice growing area, Saraipali block, Mahasamund, Chhattisgarh, India was selected for the assessment and rating.

Study Area
Saraipali (21.33˚N 83.0˚E) is a block in Mahasamund district, Chhattisgarh state, India, including 299 town and villages inclusive of Saraipali town with population of ≈0.3 million.The rice is a main crop of the area with use surplus amount of groundwater to take the multiple crops in a year.The water is hard and become turbid on the storage due to precipitation of the metals i.e.Mg, Ca and Fe into oxides and hydroxides.The health problems (i.e.tiredness, diarrhea, stone formation in kidney and spleen, etc.) in the residence of the studied area due to intake of the groundwater were marked.Therefore, in the present work, the water quality assessment of Saraipali area was chosen.

Sample Collection
The groundwater samples were collected from 30 locations of the town and nearby villages, Figure 1.The water was collected in the post monsoon period, January, 2014 in a 1-L cleaned polyethylene bottle by using established methodology [16].The bottle was ringed thrice with the sampling water prior to collection and filled up to the mouth with the water.The physical parameters i.e. pH, temperature (T), electrical conductivity (EC), reduction potential (RP) and dissolved oxygen (DO) were measured at the spot.

Analysis
The Hanna water analyzer kits was used for the measurement of the physical parameters.The total dissolved solid (TDS) value was determined by evaporation method by prior filtering the water through glass fiber with subsequent drying at the constant weight [16].The total hardness (TH) and total alkalinity (TA) values were analyzed by titration methods [17].The Metrohm ion meter-781 was used for monitoring of F − by using the buffer in a 1:1 volume ratio.The Dionex ion chromatography-1100 was used for the quantification of the ions.Multivariate statistical model i.e. factor analysis (FA) was used for the source apportionment of ions and metals [18].The statistical software STATISTICA 7.1 was employed for the multivariate statistical calculations.
The various water quality indices i.e. sodium adsorption ratio (SAR), sodium hazard (SH) and water quality index (WQI) were used for rating of the water quality.The weighed arithmetic method was employed for computation of the WQI of the groundwater by using four parameters i.e. pH, DO, EC and TDS [19] [20].The following equations were used for calculation of the indices.
The equivalent concentrations of cations were used. WQI Quality rating of the nth water quality parameter.
V n = Estimated value of the nth parameter of a given water.
S n = Standard permissible value of the nth parameter.
V io = Ideal value of the nth parameter of pure water (i.e.0 for all other parameters except pH and dissolved oxygen (7.0 and 14.6 mg/L, respectively).
W n = Unit weight for the nth parameter.

Geology
Chhattisgarh basin is characterized by rocks belonging to Proterozoic aged sandstone, limestone, and dolomite, conglomerate, etc. Siliciclastic-carbonates are deposited in muddy shelf and platformer environment, indicative of more stable tectonic condition.Its deposition is controlled by several cycles of transgressions and regressions.The Proterozoic grouprocks are found to spread over the studied area.The gypsum minerals are found to be more intense than calcareous minerals, containing both toxic and precious elements at traces.The physical characteristics of 30 tube well of Saraipali area is summarized in Table 1.The depth of tube well (n = 30) is moderate, ranging from 24 -63 m with mean value of 32 ± 2 m.The ionic contamination of the water was found to be related with the depth profile of the tube wells and increased as the depth profile was increased (r = 0.59).The age of tube wells was ranged from 7 -25 Yr with mean value of 17 ± 2 Yr.The water quality was also found to be influenced by the age of tube wells.

Physical Characteristics of Water
The chemical characteristics of the groundwater are presented in Table 2.The T, DO, RP and pH value of water (n = 30) was ranged from 19˚C -22˚C, 4.8 -5.4 mg/L, 117 -238 mV and 6.2 -8.3 with mean value of 20.9˚C ± 0.3˚C, 5.1 ± 0.1 mg/L, 187 ± 9 mV and 6.88 ± 0.13, respectively.In some locations, the water was found to be slightly acidic due to higher Cl − and 3 NO − contents.The EC, TDS, TA and TH value of water was ranged from 785 -4589 μS/cm, 651 -2836 mg/L, 159 -610 mg/L and 186 -864 mg/L with mean value of 1946 ± 363 μS/cm, 1411 ± 221 mg/L, 352 ± 45 mg/L and 355 ± 58 mg/L, respectively.The EC value was mainly contributed by the ions i.e.Na + , K + , Cl − ,

Source
The correlation coefficient matrix of the water variables are shown in Table 3.Among them, ions i.e.F − , Cl − , Na + , Mg 2+ and Ca 2+ were found to be well correlated, showing origin from the common sources.The molar ratio of [Na + ]/[Cl − ] was ranged from 1.5 -11 with mean value of 5 ± 1, indicating both geogenic and anthropogenic origins of Na in the water.
The FA model showed the extraction of six factors with account for 84.04% of total variance, Table 4. Factor-1 accounts for 39.27% of the total variance with strong positive loadings of TH, Ca 2+ , Mg 2+ , F − , Cl − , EC and TDS; related to hardness depending on the weathering of fluoride bearing materials such as CaF 2 .Factor-2 explains 14.79% of the total variance with high positive loading of 2 4 SO − , correlated to evaporation of the water.Factor-3 explains 9.06% of the total variance with high positive loading of alkalinity in opposition to Fe. Factor-4 accounts for 8.32% of the total variance with a negative loading of DO.Factor 5 explains 6.87% of the total variance with a negative loading of the variable Age of the tube wells.Factor-6 accounts for 5.74% of the total variance with a high positive loading of NO 3 − , indicating agricultural impacts in the water.

Water Quality
The value of TA, TH, Mg, Ca and Fe content was found to be higher than recommended value of 120, 200, 30, 75 and 0.30 mg/L, respectively [19] [20].The value of SAR, SH and WQI was ranged from 1.8% -28%, 19% -84% and 86% -713% with mean value of 6.6% ± 1.7%, 50% ± 5% and 275% ± 60%, respectively.The  classification of groundwater was grouped on the basis of SH values, excellent (<20%), good (20% -40%), permissible (40% -60%), doubtful (60% -80%) and unsuitable (>80%).It means the water of the studied area was found to be sodic and hard in nature, being unsuitable for the drinking purposes.They could be used for the irrigation purposes but prolonged excessive extraction of the water may cause adverse impacts in rice yields in near future.

Conclusion
The groundwater of Saraipali area is deteriorated rapidly due to its excessive extraction for the irrigation purposes.The water is sodic and hard in nature.The values of EC, TH, TA, Na, Mg, Ca and Fe were observed to be above reported permissible limits.The water is seemed to be unsuitable for the drinking purposes due to high mineralization of the bed-rock elements in the aquifer.The water could be used for the irrigation of the new varieties rice crops required less water with lower ripping life.

Figure 1 .
Figure 1.Representation of sampling locations in Chhattisgarh, India.

Figure 2 .
Figure 2. Spatial variations in sum of total concentration of the ions.

Table 1 .
Geophysical characteristics of tube well and groundwater during January, 2014.

Table 2 .
Chemical characteristics of groundwater during January, 2014, mg/L.

Table 3 .
Correlation coefficient matrix of elements in water.

Table 4 .
Eigenvalues and factor loadings of groundwater.