In pursuant to the collected groundwater samples (79 numbers) from various parts of the 15 km radius of SIPCOT estate was examined in January 2021 (COVID-19) pandemic period. The addition of TZ+ (cations) and sum of TZ- (anions) equilibrium shows the charge equilibrium inaccuracy proportion [Hemant Pathak and Limaye 2012]. The inaccuracy percentage is amid +1 percent to +10 percent by little exemption as some particles illustrates the unusually elevated concentration occur in the period. Occurrence of inaccuracy in chemical assess of groundwater is also due to the reagent employed, confines of the techniques and the utensil used available of fifth in refined water and so on. The relationship associative among TZ+ and TZ− is about 0.5 to 0.8 TDS. The EC proportion various as of 0.4 to 0.8. The rate of mean, minimum, maximum and limiting values with classifications in the study period are given in Table 1.
The pH analysis of groundwater samples from various sampling points of the study is revealed that the values fall between 6.72 to 8.05 (Table 1). The entire study region of groundwater pH values is within the limit of WHO standards. The ranges of EC in the study area vary from 556 µS/cm to 8560 µS/cm for January-2021 COVID-19 pandemic period. The inner area of 5km radius of SIPCOT (Sample well no. 43,52&53), 5-10km (Samples well no. 15,25,33,36,45,49,50,60,70) and 10-15km (Sample well no. 4,13,14,22,23,31,58,66, 68,69,72,75,76) shows very high EC value for this period as seen in Figure 5. Since these wells are located near the discharge the waste water streams of industries, dense residential area and chemical weathering of rock and minerals [Hemant Pathak and Limaye 2012].
Table 1
Results of Groundwater parameters based on the WHO 2017 and Basic statistical analysis
Elements | WHO Standard-2017 | Wells exceeding permissible limits out of 79 Samples | Pandemic Period (January 2021) |
Most desirable | Maximum allowable | Not permissible | Average | Minimum | Maximum |
Electrical Conductivity | <1500µS/cm | - | >1500µS/cm | 4,13,14,15,22,23,25,31,33,36,43,45,49,50,52,53,58,60,66,68,69,70,72,75,76 (25) | 1548.84 | 556 | 8560 |
Total Dissolved Solids | <500mg/L | 500 to 1500mg/L | >1500mg/L | 14,25,31,49,52,58,60,66,69,70,72,76 (12) | 1084.00 | 389 | 5992 |
pH | 6.5 to 8.5 | - | < 6.5 and >8.5 | All samples within Most desirable limits | 7.43 | 6.74 | 8.05 |
Calcium (Ca2+) | <75mg/L | 75 to 200 mg/L | >200 mg/L | 14,52,58,60,70,72,76 (7) | 111.96 | 46.4 | 435.2 |
Magnesium (Mg2+) | <50mg/L | 50 to 150 mg/L | >150 mg/L | 52,72 (2) | 51.64 | 14.4 | 218.88 |
Sodium (Na+) | <200mg/L | - | >200 mg/L | 58,60,66,70,72 (5) | 120.56 | 17 | 1000 |
Potassium (K+) | <10mg/L | - | >10mg/L | 2,4,5,6,13,14,15,22,24,25,30,31,33,36,38,39,40,42,44,45,48,49,50,52,53,55,56,58,60,61,64,66,67,68,69,70,71,72,73,75,76,79 (42) | 19.35 | 5 | 400 |
Iron (Fe2+/3+ mg/L | <0.3mg/L | | >0.3mg/L | 5,6,17,19,20,37,60,70,71,77 (10) | 0.21 | 0 | 2.6 |
Bicarbonate (HCO3−) | <300mg/L | 300 to 500 mg/L | >500 mg/L | 72 (1) | 318.48 | 84 | 3020 |
Nitrate (NO3−) | <45mg/L | - | >45mg/L | All samples within Most desirable limits | 12.15 | 5 | 42 |
Chloride (Cl−) | <200mg/L | 200 to 600 mg/L | >600mg/L | 14,49,52,58,60,66,70,72,76 (9) | 229.92 | 44 | 1200 |
Sulfate (SO42−) | <400mg/L | - | >400mg/L | 52,72 (2) | 134.90 | 34 | 450 |
Fluoride (F−) | <1.5mg/L | - | >1.5mg/L | 4,16,17,24,28,29,30,38,43,47,51,55,64,70,72 (15) | 1.14 | 0.2 | 2.8 |
Total Alkalinity | <500mg/L | - | >500mg/L | 72 (1) | 318.48 | 84 | 3020 |
Total Hardness | <100mg/L | 100 to 500 mg/L | >500mg/L | 4,13,14,15,22,23,25,31,34,36,43,45,49,50,52,58,60,63,66,68,69,70,72,75,76 (25) | 495.06 | 184 | 2000 |
The analysis of TDS in the study area reveals that the value is in the ranges from 389mg/L to 5992mg/L for January-2021, COVID-19 pandemic period (Figure 5). It is also found that higher value of TDS of water samples from 5km radius of SIPCOT (Sample well no.52), 5-10km (Samples well no. 25,49,60 and 70) and 10-15km (Sample well no. 14,31, 58,66,69,72,76) as seen in Figure 6. Hence, the analysis of the parameters EC and TDS reflects the intrusion of industries and chemical weathering of rocks and minerals effluent into the groundwater [Manoj et al 2020]. It also causes health issues like kidney stone in humans [Garg et al 2009].
The total alkalinity analysis in the study area reveals that the value is estimated between 84 mg/L and 3020 mg/L for the season as represented in the figures 7 which is well (Sample well no.72) over the permissible limit of WHO. Hence, from the analysis of the parameter, the total alkalinity reflects the soil gases that dissolve in rain, surface water, and groundwater [Durgadevagi and Annadurai 2016].
In the study area, the range of total hardness is 184-2000 mg/L. The inner area of 5km radius of SIPCOT (Sample well no.34, 43 & 52), 5-10 km (Samples well no.15, 25, 36, 45, 49, 50, 60, 63, 66 & 70) and 10-15km (Sample well no.4, 13, 14, 22, 23, 31, 58, 68, 69, 72, 75 & 76) shown very high total hardness in Figure 8 and Table 1 (WHO 2017).
The calcium content analysis of the study area is shown in the Table 1. The influence is that the minimum value of calcium is 46.40mg/L which extends to a maximum of 435.20mg/L. Very high Ca2+ value of samples is located within 5km radius of SIPCOT (Sample well no.52) due to industrial effluents. From 5-10km (Samples well no.60 & 70) due to discharge the waste water streams of industries. From 10-15km (Sample well no.14, 58, 72 & 76) due to lineament act as chemical weathering of rocks and addition domestic sewage as seen in Table 1.
The analysis of results in Table 1 reveals that the concentration of Mg is present in the range of 14.40–218.88mg/L from the spatial distribution of magnesium that is shown in Table 1. It is found that nearly 99% of the study area is much good for the concentration of Mg within the most desirable and maximum allowable limit of WHO-2017. The concentration of Na in the region varies from 17 to 1000 mg/L. Table 1shows that 94% of the study area contains the sodium levels within the prescribed limit of WHO standards. And remaining 6% of the study area is under high risk of sodium concentration.
Considering the quality of water in the region, it is found that the concentration of Potassium is ranged from 5 to 400mg/L (Table 1). 15% of the samples contain the potassium levels within the prescribed limit of WHO standards. And remaining 85% of the samples are under high risk of sodium concentration. Although, Na+ and K+ ions are naturally found in groundwater, industrial and household waste also add ions to groundwater [Garg et al 2009].The concentration of Fe2+/3+ in the region varies from 0 to 2.60mg/L. Table 1shows that 80% of the samples contains the iron levels within the prescribed limit of WHO standards. And remaining 20% of the samples are under high risk of iron concentration. The result shows that the value of NO3 varies from 5 to 42mg/L for the COVID-19 pandemic period (Table 1). Hence, the region under investigation is least affected by Nitrate content as the consistence of nitrate is below the permissible value of 45mg/L.
The inner area of 5km radius of SIPCOT Sample well no.52 is high concentration of chloride, due to industrial effluents. From 5-10km area is observed the sample well nos. 49, 60 & 70 is above consumption value, due to influence of house hold sewage. From 10-15km (Sample well no. 14,58,66,72&76) show very high Cl− value for the pandemic period. It is representing percolating as of top most strata due to manufactures and household activities and arid weathers, such addition of Cl− to the groundwater by mixing with higher chloride water nearby formation and Cl− leached from fluid inclusion (or) inter-granular salts [Cheong et al 2012] as seen in Table 1.
The result of analysis that is shown in Table 1 reveals that the concentration of SO4 ranges between 34–450mg/L and from the spatial distribution of sulfates, it is found that 99.88% of the study area is much better for the concentration of SO4 is within the most desirable limit of WHO-2017.
The study area fluoride content ranges from 0.20 to 2.80 mg/L in groundwater. The fluoride concentration of various sampling points is almost 89% of the groundwater samples in the study area are not affected by fluoride content (less than the prescribed limit of WHO). And only 11.30% of the samples is susceptible to fluoride content that is greater than the permissible limit of drinking water (Sample nos. 4,16,17,24,28,29,30,38,43,47,51,55,64,70,72). The fluoride content of the not permissible samples ranges from 1.6 to 2.80 mg/L (Table 1) in the study region.
Integration Study Of Spatial Maps
The systematic union analysis was carried out on the GIS platform utilizing maps of various cations such as Ca2+, Mg+2, Na+, K+ and Fe2+/3+ and Anions like HCO3−, Cl−, SO42− and F−. The main cations and anions quality of groundwater is shown by the integrated output maps Figures 9 and 10. Figure 9 demonstrates that 1.55% of the study region has cations levels that are within the most desired limit, whereas 87.49% of the area is underline by maximum allowable class for drinking uses. Furthermore, 10.95 percent of the research region is at high risk of cation concentration.Not permissible class of samples is located within 5km radius of SIPCOT (Sample well no.52) due to industrial effluents. From 5-10km (Samples well no.60 & 70) due to discharge the waste water streams of industries. From 10-15km (Sample well no. 58, 66 & 72) due to lineament act as chemical weathering of rocks and addition domestic sewage as seen in Figure 9.
The integrated anion content concentration of various sampling points is mapped as the spatial distribution in Figure 10 which shows that almost 23.01% of the groundwater in the study area is most desirable class; maximum allowable category is 67.85%. And only 9.14% of the study area is susceptible to anion content that is greater than the permissible limit of drinking water (Sample nos. within 5km radius area as 43, 51 and 52; 5 to 10 km radius area is 24, 28, 55, 60, 64; 10 to 15 km radius area as 4, 14, 29, 38,66, 72). It is representing percolating as of top most strata due to manufactures and household activities and arid weathers, such addition of anions to the groundwater by mixing with higher anions water inter-granular salts.
Piper Trilinear Diagram
The piper (Figure 11) plot shows that 97.47% of the samples in Ca2+-Mg2+-Cl−-SO42− type indicate the predominance of anthropogenic impact [Srinivasamoorthy et al 2011]. The association of Na+-K+-HCO3− is 94.94% of the samples correspondingly. It is mainly due to feldspar weathering processes/ion exchange processes [Sekaran et al 2019].The plot shows that 62.03% and 30.38% of the samples signify the mixed (CaMgCl and Ca-Cl−) category respectively. These types indicate the predominance of anthropogenic impact. Few locations indicate CaHCO3 and Na-Cl− categories. Percolation meteoric water initiates bicarbonate to the groundwater.
The cation triangle plot reveals that the majority of the samples fall in ‘No dominant’ (92.41%).
The anion triangle plot reveals that 56.96% of the samples are represented as ‘No dominant’. The second dominating (40.50%) anion is Cl− ion next to HCO3− in the study area (Figure 11). In general, alkali exceeds alkali earth indicating control of water chemistry by strong acid along with weathering of feldspar enriched rocks and SIPCOT estate industries effluents.
Correlation Analysis
Correlation between the various chemical constituents was conceded out for pandemic period (COVID-19) with respect to open wells and tube wells in order to locate the closely related positive and negative ion from their correlation coefficient. Table 2illustrates that the EC and TDS shows good positive correlation between Na+ (r = 0.92), NO32− (r = 0.92), Mg2+ (r = 0.92), Cl− (r = 0.86), Ca2+ (r = 0.92), SO42− (r = 0.81), K+ (r = 0.79), HCO3− (r = 0.73) and negative correlation with pH (r=-0.12).
While the Ca+2, Mg2+ is positive correlation with Cl− (r = 0.93) reflecting the influencing man-made activities [Thivya et al 2013]. Na+, K+ is positive correlation with HCO3− (r = 0.97) indicates chemical weathering [Prasanna et al 2010] of as illustrated by the Piper trilinear diagram (Figure 11).
Total Hardness showed good positive correlation with Ca2+, Mg2+ (r = 1.00), Cl− (r = 0.93), NO32− (r = 0.92), SO42− (r = 0.90) and showed negative correlation with pH (r= -0.10). Higher values of TH concentration in groundwater samples might be due to maximum salt concentration. T.Alk shows good positive correlation with K+ (r = 0.97), HCO3− (r = 1.00), Na+ (r = 0.92), NO32− (r = 0.51) and negative correlation with Fe2+/3+, pH (r=-0.01, -0.04) influencing of agricultural activities and industrial effluents or sewage infiltration [Cheong et al 2012]. pH is negative relation with other parameters.
Table 2
Inter-elements correlation matrix for groundwater
Correlation Matrix - Marked correlations are significant at p< .05000 N=79 |
Variable | Ca | Mg | Na | K | Fe | Cl | HCO3 | SO4 | NO3 | F | pH | EC | TDS | T.Alk | TH |
Ca | 1.00 | | | | | | | | | | | | | | |
Mg | 0.99 | 1.00 | | | | | | | | | | | | | |
Na | 0.70 | 0.71 | 1.00 | | | | | | | | | | | | |
K | 0.55 | 0.55 | 0.90 | 1.00 | | | | | | | | | | | |
Fe | 0.04 | 0.04 | 0.10 | -0.01 | 1.00 | | | | | | | | | | |
Cl− | 0.93 | 0.93 | 0.66 | 0.40 | 0.10 | 1.00 | | | | | | | | | |
HCO3 | 0.47 | 0.47 | 0.87 | 0.97 | -0.01 | 0.29 | 1.00 | | | | | | | | |
SO4 | 0.90 | 0.90 | 0.61 | 0.47 | 0.11 | 0.80 | 0.38 | 1.00 | | | | | | | |
NO3 | 0.92 | 0.91 | 0.79 | 0.56 | 0.13 | 0.91 | 0.51 | 0.82 | 1.00 | | | | | | |
F | 0.14 | 0.16 | 0.33 | 0.35 | 0.05 | 0.05 | 0.41 | 0.15 | 0.16 | 1.00 | | | | | |
pH | -0.10 | -0.11 | -0.10 | -0.10 | 0.07 | -0.15 | -0.04 | -0.08 | -0.08 | 0.01 | 1.00 | | | | |
EC | 0.92 | 0.92 | 0.92 | 0.79 | 0.08 | 0.86 | 0.73 | 0.81 | 0.92 | 0.26 | -0.12 | 1.00 | | | |
TDS | 0.92 | 0.92 | 0.92 | 0.79 | 0.08 | 0.86 | 0.73 | 0.81 | 0.92 | 0.26 | -0.12 | 1.00 | 1.00 | | |
T.Alk | 0.47 | 0.47 | 0.87 | 0.97 | -0.01 | 0.29 | 1.00 | 0.38 | 0.51 | 0.41 | -0.04 | 0.73 | 0.73 | 1.00 | |
TH | 1.00 | 1.00 | 0.71 | 0.55 | 0.04 | 0.93 | 0.47 | 0.90 | 0.92 | 0.15 | -0.10 | 0.93 | 0.93 | 0.47 | 1.00 |
Cl− and SO42− are established to tolerate statistically the important correlation with most of the parameter representatives seal alliance of these factors with each other. So, the parameter, EC, can provide an excellent sign of a numeral with associated factors. Poor correlation subsists among K, HCO3− and other ions. This indicates the chemical disintegration process that stimulate beside by the release of second stage salt formation. It might be the principal supplier in support of those particles.
Factor Analysis
The factor analysis for the January-2021 (COVID-19 Pandemic Period) was conceded away and the results show complexity in chemical nature of the area. The association of the ion in Factor 1 with the total variance of 63.24% representing high positive loadings on Ca, Mg, Cl−, and SO4 which clearly indicates that these ions observed in the investigated outcome of groundwater is associated with the rock weathering and domestic discharges and industrial effluents. NO3, EC, TDS, TH indicates that the alkalinity observed in the investigated outcome of groundwater is associated with the huge quantity of chemical fertilizers used in irrigation [Selvakumar et al 2017]. This shows that the EC is managed by this chief ion of calcium, magnesium, chloride and sulphate. This factor can be clarified by the large habitation instance of groundwater, better rock water interaction and superior solvent of minerals [Le et al2017].
Factor 2 stands for Na, K, HCO3 plus T.Alk by 14.98% of total variance (Table 3). This factor indicates that the pollution from agricultural land using fertilizers or due to sodium, potassium and bi-carbonates processes that normally occur on bore well water point in soils segment, where natural substances and O2 are copious along with secondary dissolution [Selvakumar et al 2017].
Seventy-nine samples of groundwater were taken from principal component analysis and the correlation matrix is demonstrated in Table 4 and Figure20 which signifies the resolved initial PC, its Eigen values and % variance associated in every PC. Scree plot (Figure 12) demonstrates the three-dimension loading plots of factor score [Dudeja et al 2013]. Eigen values superior of one are considered, and the initials of three prime mechanisms are the most chief components that represent 63.24% percent variables in water quality including in the period of study.
Table 3
Variable | Factor 1 | Factor 2 |
Ca | 0.954 | 0.246 |
Mg | 0.952 | 0.251 |
Na | 0.578 | 0.769 |
K | 0.344 | 0.911 |
Fe | 0.114 | -0.036 |
Cl | 0.964 | 0.082 |
HCO3 | 0.240 | 0.958 |
SO4 | 0.892 | 0.170 |
NO3 | 0.904 | 0.307 |
F | -0.017 | 0.546 |
pH | -0.131 | -0.017 |
EC | 0.832 | 0.550 |
TDS | 0.832 | 0.550 |
T.Alk | 0.240 | 0.958 |
TH | 0.956 | 0.249 |
Expl.Var | 7.255 | 4.478 |
Prp.Totl | 0.484 | 0.299 |
Eigenvalue | 9.487 | 2.247 |
% Total variance | 63.244 | 14.980 |
Cumulative Eigenvalue | 9.487 | 11.734 |
Cumulative % | 63.244 | 78.224 |
Drinking Water Quality Index (Wqi)
The Drinking Water Quality Index (DWQI) spatial distribution map for the period is shown in figure 13which emphasis that the very high risk for drinking in the zones which are closer to the SIPCOT estate where noticed; one in southeastern part (5-10 km radius) and another in southwest corner (10-15 km radius) of the study area.
The quality of groundwater based on TDS and TH diagram is presented in six segments such as soft saline, soft brackish, soft fresh, hard saline, hard brackish and hard fresh water categories respectively [Elumalai et al 2017]. This diagram reveals that 67.09% of the samples fall under ‘Hard fresh water’ category which is mainly due to the presence of weathering processes/ion exchange processes. Rest of 32.91% of the water samples were fall in ‘Hard brackish water’ (Figure 14) respectively. Hard brackish groundwater area is the direct influence of the SIPCOT effluents.
In this diagram, Cl− is plotted in X-axis and NO3 is plotted in Y-axis. This plot (Figure 15) indicates four different types of hydro-geochemical process type 1 (less than 6.6% of the Cl− and NO3), type 3 (6.6–10% of the Cl− and NO3), type 2 (10 % to 40 %) and type 4 (More than 40%) in the study. The plot reveals that 82.28% of the groundwater samples fall under type 1; it has a good quality of water. Rests 17.72% of the samples have a bad quality of groundwater. Thus, above data indicates the impact of SIPCOT effluents on groundwater chemistry.