The groundwater in the Uddanam area has been examined in terms of physicochemical properties, and the drinking, irrigation, and human health hazard indexes have been derived as a result. These parameters are described more below:
Hydrogen–ion Concentration (pH):
The pre-monsoon pH of the study area's groundwater ranges from 5.90 to 7.90 with a mean value of 7.07, and the post-monsoon pH ranges from 5.9 to 7.9 with a mean value of 7.19, respectively. It is indicating that the groundwater is slightly acidic to alkaline in nature Due to the interaction of groundwater water with minerals and rock formation in the study area (Adimalla, & Wu, 2019). In the spatial distribution diagram, the higher pH range of the value s lies in the NW direction, whereas the lowest values fall in the SW direction (Figure 3a-o & Figure 4a-o)
EC and TDS
In this study, Pre-monsoon EC values varied from 282 to 2404 with a mean value of 1016.23 (mg/L). Post-monsoon EC values range from 245 to 2000 with a mean value of 945.15 (mg/L) respectively. Pre-monsoon TDS levels in the study region vary from 183.3 to 1562.60 with an average value of 660.55(mg/L), whereas post-monsoon TDS values range from 159.25 to 1300 with an average value of 617.24(mg/L).The groundwater in the area appears to be moderately mineralized, and the EC and TDS values indicate that the water has enough time to interact with the solidmedia in the specified area (Kumar, 2014). In the spatial distribution diagram, the higher pH range of the values lies NW direction, whereas the lowest values fall in the NE direction.
Total Alkalinity (TA) carbonate and Bi-carbonate
In this study, pre-monsoon total alkalinity of groundwater ranges from to 160 mg/L to335 mg/L with a mean value of 256.33 mg/L, and post-monsoon total alkalinity of groundwater ranges from 163 mg/L to 342 mg/L with a mean value of 277.17 mg/l, respectively. The mineral calcite found in rocks and dissolved CO2 in groundwater may be the source of alkalinity. The concentration of CO32- in groundwater was found in traces, while the concentration of HCO3- in the pre-monsoon varies from 80 to 533 mg/L, with an average value of 253.23 mg/L, and in the post-monsoon HCO3-ranges from 61.35 mg/l to 577 mg/l, with a mean value of 195.75 mg/L respectively. Anthropogenic activities contributing more bicarbonate to groundwater are likely possible in areas with moderate to high levels of total alkalinity. In the spatial distribution diagram, the higher pH range of the values lies in the SW direction, whereas the lowest values fall in the NE direction.
Total Hardness (TH)
In the pre-monsoon, the total hardness of the groundwater in this area ranged from 213.40 mg/L to 842.90 mg/L as CaCO3, with a mean value of 389.50 mg/L, whereas during post-monsoon TH varies between 118.5 mg/L and 675.10 mg/L as CaCO3, with a mean value of 337.96 mg/L.Due to high quantities of calcium and magnesium, the groundwater seems to be hard. The lower TH range of the values fall in the southern direction, whereas the higher TH range is in the central and northern direction.
Major ion chemistry
In the study area, the concentrations of Ca2+ in groundwater for pre-monsoon are found in the range of 38 mg/L to 265mg/L with a mean value of 87.38, Whereas, in the post-monsoon concentrations of Ca2+ in groundwater range between 25.65 mg/L to 170 mg/l with an average value of 78 mg/L, respectively, in which the majority of the wells (65%) fell permissible and the remaining (35%) exceeded the BIS standards. The main reason is due to the dissolution of the calcite, the Khondalite group of rocks. Mg2+ ion concentrations in pre-monsoon varies from 12 mg/L to 83.94 mg/L the average concentrations of Mg2+ recorded as 42.16 mg/l, whereas for post-monsoon in groundwater the Mg2+ concentrations varied from 3.4 mg/L to 78 mg/l, and the mean value of 35.0 mg/L, respectively. In the spatial distribution diagram, the higher Ca2+ is found in the entire study area with excess values found in western areas, whereas the higher Mg2+ range of the values lies NE direction, while the lowest values fall in the SW direction.
Na+ and K+ in the ranges in the Pre-monsoon concentrations are as follows: Na+ ranges between 35 mg/l to 185 mg/l with an average of 95.62mg/L, whereas, for post-monsoon samples, the concentrations of Na+ range between 22.99 mg/L to 187.00 mg/L, with an average of 88.71 mg/L and in pre-monsoon, concentrations of K+ varies between 7 mg/l to 42 mg/l with an average of 13.79 mg/L, whereas in the post-monsoon, the ionic concentrations of K+ ranges between 3.92 mg/l to 27.0 mg/l with a mean of 13.2 mg/L, respectively. In the spatial distribution diagram, the higher Na+ range of the value s lies SE direction, and the lowest values fall in the NE direction, whereas the higher K+ values lies NE and SW direction.
The most prevalent cation in groundwater is Na+, which is followed by Ca2+and Mg2+. K+ has the lowest concentration in groundwater.In groundwater, Na+ concentrations are considerably higher than K+ concentrations. The Na+ may also be contributed to groundwater from rainwater rich in sodium content from a coastal area (Balaji et al, 2019). The seawater ingression may also cause to increase in sodium content in groundwater. Anthropogenic sources such as domestic and industrial waste and wastewater are also rich in Na+ and if percolated into groundwater can significantly contribute to raising the concentration of Na+ in groundwater. Groundwater can get enriched with K+ as a result of agricultural operations if potassium fertilizers are widely employed. When organic matter decomposes and leaches from the soil, the K+ absorbed by plants can also serve as a source of K+ in groundwater. (Golla et al. 2019).
Pre-monsoon chloride (Cl-) concentrations in the groundwater in this study locality range from 48 mg/L to 343.97 mg/L with an average value of 157.95 mg/L, whereas post-monsoon samples have chloride concentrations that range from 2.3 mg/L to 326.0 mg/L with an average value of 132.67 mg/L.For pre-monsoon samples, the concentration of SO42- in the groundwater in the following research ranges from 10 mg/L to 87 mg/L, with a mean of 36.52 mg/L. The concentration of SO42 in post-monsoon samples, however, varies from 11 mg/L to 89 mg/L with an average value of 38.06 mg/L.Groundwater in the field of study may contain SO42- due to atmospheric precipitation, agricultural activity such as the use of fertilizer and pesticides, and other factors. In the spatial distribution diagram, the higher Cl- values are seen in the central region and the lowest values are seen in NE and SW directions. Whereas the higher SO42- range of the values lies in a central region, whereas the lowest values fall in the NE and SW direction.
The nitrate values for the Pre-monsoon area range from 16 mg/L to 74 mg/L with an average of 42.66 mg/L whereas for post-monsoon samples the nitrate values are ranges from 16 mg/L to 77 mg/L with a mean value of 42.20 mg/L in pre-monsoon (Marchand et al, 2002). The pre-monsoon values of fluoride in the groundwater of this study region ranging from 0.19 to 1.0 mg/L with a mean of 0.42 mg/L, while post-monsoon concentrations ranging from 0.24 to 1.0 mg/L with an average of 0.49 mg/L.
In the study area, the silica values for pre-monsoon range from 15 mg/L to 57 mg/L with an average of 32.67mg/L, respectively. Whereas in post-monsoon the silica values varied from 21 mg/l to 116 mg/l with a mean of 51.73 mg/l, respectively. It shows the study area may face problems with access silicon ion concentration. The weathering of the silicate group of minerals, which is mostly produced from the rock water of the research area, is the primary cause of the silica present in the area (Hem, 1959).
Irrigation water quality classification:
In irrigation water quality percent sodium and sodium absorption are very important factors in determining the appropriateness of water for irrigation.
Wilcox diagram
Calculating the Na+% is another way of evaluating the suitability of groundwater for agricultural use. (Wilcox, 1955), since soil's permeability is decreased when Na+ concentration reacts with it (Todd and Mays, 2005). Except for one sample that falls into the unfit group during both monsoons, the sodium percentage values of the remaining groundwater samples, both in the pre-and post-monsoon categories, are good to permissible for irrigation use (Figure 4.0)
USSL classification
All of the samples exhibit low to medium SAR levels both before and after the monsoon, according to the USSL diagram's plotting of SAR statistics. The 50 samples were divided into two fields: C2-S1 (53.33 percent) and the remaining C3-S1(40%) and C4-S1. The USSL diagram classifies the C3-S1 field as having a reasonably good water type for irrigation usage. This indicates that no expected alkali risk to crops exists (Figure 5.0).
Piper diagram
It is a description of the research area's groundwater facies. Using the piper diagram, the facies indicate the pre-date and post-monsoon periods. The piper diagram, which shows the major cations and anions, can be used to understand the hydrochemical dynamics of groundwater (Figure 6.0). The three main hydrochemical facies in pre- and post-monsoons are Ca-HCO3, Ca-Mg-HCO3, and Ca-Mg-Cl.
Nitrate (NO32-) health risk assessment
Nitrate contamination of groundwater causes thyroid abnormalities, methemoglobinemia in newborns, and possibly some carcinogenic effects, which are health issues linked to ingesting nitrate (Bahadoran, et al. 2015). The nitrate health risk assessment was chosen to evaluate the potential health impacts on humans.
Risk calculations were performed with all samples with Eqs. 1 and 2 depends on the water consumption of children, teens, and adults. In this investigation, the chronic daily dose (CDD) and hazard quotient (HQ) for nitrate intake through oral water consumption were taken into account. The total health risk assessment was derived from the below equitation (Thomson B, 2007).
CDD oral=CW × IR × EF × ED/ABW×AT ------------- (1)
HQ= CDD oral× RfD --------------------- (2)
This equation's explanation is as follows:
CDD Oral CDD refers to the chronic daily dose (mg/kg-day); IR stands for the ingesting ratio; Nitrate concentration in drinking water is represented by Cw (mg/l), exposure frequency is given by EF (years/days), and exposure duration is represented by ED (years); BW stands for a person's body weight in kilograms; The standard dosage for nitrate (1.6 mg/kg-day) is specified by the abbreviations RfD and AT, which stand for average lifetime (years) which is advised in accordance with the USEPA's (United States Environmental Protection Agency) and IRIS's (Integrated Risk Information System's) respective recommendations (Aravinthasamy, et al. 2019;Molagamudi, 2022)
The total hazard quotient for nitrate was computed using Esq. (3)
HQ oral= CDD/RFD ---------- (3)
Using the overall hazard index and non-carcinogenic risk (THI), the USEPA has set an upper permitted limit (EPA US) (2015). The total hazard health index value is unacceptable if it is more than 1.The percentages of children, men, and women impacted by the pre- and post-monsoon nitrate total hazard index in the study area are 94%, 53%, 37%, and 94%, 51%, 29%, respectively (Table 3&4).
HQ Dermal: By using following equation, the hazard quotient was employed to determine the nitrate health risk through dermal ingestion.
HQ Dermal=Cw × SA × Kp × F × ETs × EF × ED/BW × AT × 1000 -------- (4)
Dermal contact does not have a substantial impact on the targeted area for different groups of people, such as adults, women, and men (Table 3&4).
Sources of ions
Based on the analyzed results scatter and bi-variate plots were portrayed to distinguish the sources and controlling processes for groundwater chemistry. From the result, it is evident that Cl- and NO32- are of anthropogenic sources (Figure 7a&b). And the remaining ions may release into the water by carbonate dissolution and silicate weathering (Figure 7c-e).
Gibbs diagram:
The mechanisms responsible for controlling the groundwater chemistry are studied using Gibbs's diagram. The ratios (1) (Na+ + K+) / (Na+ + K+ + Ca2+) and (2) Cl- / (HCO3- + Cl-) were plotted against TDS (Figure 8.0). The area closest to the centre of Gibb's graph has the highest point density both pre and post-monsoons. The dominance of this cluster of points shows the lithological interactions with percolating precipitated water into the sub-surface which is further evaluated by scatter plots (Figure 7e). Hence, it could be concluded that the chief mechanism controlling the chemistry of groundwater in the study area is the rock-water interaction (Gibbs, 1970).