Introduction

Groundwater is one of the chief sources of water for the drinking, industrial and cultivation purposes. An increasing population is placing countless demand on the natural water resources (Oladipo et al. 2011). The physical and chemical impurities that harmfully affect the properties of the groundwater may arise due to land application of cultivated chemicals, infiltration from sewage treatment plants and municipal wastes (Rajappa et al. 2011). FAO (1997) defined water as the most valuable natural resources for drinking and is necessary for the maintenance of all living things. Surface water (lakes, dams and rivers) and groundwater (hand pumps, dug wells and boreholes) are the major sources for drinking purposes. Surface water is usually more contaminated than groundwater; therefore the groundwater is the chief source of drinking in rural areas (Chukwu 2008; Adekunle 2009). About 60% people in the Pakistan live in the villages, where groundwater is mostly used for drinking. The Sindh province is facing a several shortage of drinking water due to the dry weather, high evaporation rates and high temperature. The quality of groundwater depends upon geochemistry, movement of elements and also climate of the areas (Bashir et al. 2013). The ion exchange device among groundwater and arrangement of aquifer are responsible for the existence of ions in the water (Aghazadeh and Mogaddam 2010). The availability of safe drinking water is a major issue (Khan et al. 2013). The drinking of contaminated water may cause serious health concerns, including high death rates in developing countries. The many cities of world use groundwater for their daily usage, which is contaminated. Diarrhoea is common in the Pakistan; it is due to utilizing polluted water. It is expected that in future Pakistan will face drinking water challenges (Mashadi and Mohammad 2000). Many factors cause contamination of groundwater as well as surface including industrialization and urbanization. The quality of groundwater in Pakistan is weakening day by day (Iqbal et al. 2013). A number of problems appear due to no proper management of waste water, which is penetrating into the sediment and soil with the passage of time and become a part of groundwater (Asghar et al. 2006).

A number of studies have been carried out to examine the quality of groundwater (Ukpaka and Ukpaka 2016; Majolagbe et al. 2017; Abdulrafiu et al. 2016; MacDonald et al. 2016; Adimalla et al. 2018); including from Pakistan (Noreen et al. 2017; Baig et al. 2009), which reflects the importance of monitoring the water quality including groundwater. The interests in the determination of physicochemical characteristics of hospital effluents (Ramdani et al. 2018), petroleum refinery waste water (Iqbal 2016), textile effluents, industrial effluents and their treatments (Iqbal and Nisar 2015; Iqbal et al. 2015) are attracting considerable attention. Iqbal et al. (2017) have also reported the ecotoxicity assessment and environmental toxicity of waste and river water. Abbas et al. (2018) reported the Vibrio fischeri bioluminescence inhibition assay for ecotoxicity assessment.

The present work investigates the physicochemical parameters including cations and anions and trace metal ions in the groundwater in the study areas and compares the results of parameters with World Health Organization (WHO). The multivariate statistical techniques are examined to  certain similarity among the samples and hydrochemical composition. The work enables to make recommendations concerning the suitability and hazards of the groundwater for human consumption and irrigation.

Materials and methods

Study area

Geography

The total area of District Qambar Shahdadkot is 14.53 lakh hectare with population 13.41 lakh with population growth rate 2.8%. The district is divided into seven talukas which are Qambar, Miro Khan, Shahdadkot, Warah, Sijawal Junejo, Nasirabad and Qubo Saeed Khan; the present study examines three talukas (Shahdadkot, Sijawal Junejo and Qubo Saeed Khan) for water quality assessments. Qambar Shahdadkot shares its borders with three districts of Baluchistan on the west (Khuzdar, Jaffarabad and Jhal Magsi). It is connected with districts Dadu, Larkana and Jacobabad in Sindh province. The district has vast plains, agriculture lands, mountain range of Kirthar and a number of wetlands including Hamal, Drigh and Langh. The Kirthar extends southwards for almost 300 km from the Mula River in east-central Balochistan to Cape Muari (Monze) west of Karachi on the Arabian Sea. Kirthar range is composed of limestone hills. The Kirthar range also has a National Park which is one of the largest Wildlife Parks in the area. It is located between Karachi and Balochistan. This hilly area rises from 4000 to nearly 8000 feet and is surrounded by fossilized remnants from different times of history.

Geology

The famous Hamal Lake is present in the study area. These formations are sandy rocks composed of limestone, claystone and sandstone. During mid-Eocene, marine spread caused the growth of a CO3 shelf in the area of Kirthar. The aquifers of hard rocks are mostly composed of partially cracked sandstone and limestone belonging to Kirthar formations. The limestone is the leading formation. The chief crops of the area are rice and wheat but some crops of sorghum sesame, maize etc, are also found here.

Climate

The climate of Qambar Shahdadkot District is mainly dry, with rainfall varying between 5 and 10 inches in a year and is one of the hottest areas of Sindh province. The reported maximum temperature is 124.88°F in July 2002. May, June and July are the hottest months of the district. About 95 per cent population depends on agriculture. It is also rich in gas reserves.

Samples collection and preservation

The 38 water samples were collected from three talukas: Shahdadkot, Qubo Saeed Khan and Sijawal Junejo, mostly used for human consumption and irrigation. The sampling scheme was designed to collect representative samples and covered the study area. The 14 samples each were collected from Shahdadkot and Qubo Saeed Khan talukas and 10 samples were collected from Sijawal Junejo. The approximate depth of pumps and wells was noted. The water samples were randomly spaced and collected in the clean 1.5-L polythene sampling bottles after allowing pumps to drain for 5 min before collection. The bottles were filled completely and kept in the dark in ice box. Two bottles were collected from each sampling site and immediately taken to the laboratory, one for physicochemical analysis and other for metal analysis. Samples were collected in the mornings between the January and May, 2016 (Table 1). The bottle for metal analysis was acidified with 1 ml of hydrochloric acid/ nitric acid.

Table 1 Name of sampling towns and villages of three talukas of district Qambar Shahdadkot
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Reagent and chemicals

All the chemicals used were for reagent or analytical grade and were used without further purification. The standard solutions were prepared from following: sodium chloride, potassium chloride, calcium carbonate, magnesium chloride, lead nitrate, cadmium nitrate, ferrous ammonium sulphate, cobalt sulphate, sodium nitrite, sodium nitrate, hydrochloric acid (37%), silver nitrate, sodium sulphate, ethylenediaminetetracetic acid disodium (EDTA) and potassium dihydrogen phosphate (Merck, Germany).

Physicochemical procedure

The 28 physicochemical parameters were analysed in the laboratory following standard procedures (APHA 1998). The procedure was appropriately standardized before the sample analysis, including blank determination. Each of the analysis was carried out at least in triplicate.

The analysis of major cations (Na, K, Ca and Mg) in water samples was carried out after dilution of 10–20 times with deionized distilled water, whereas the samples were concentrated ten times by the evaporation of water at 80–90 °C on an electric hot plate, filtered and maintained at 4 °C till further analysis for trace elements. Chloride, alkalinity, total hardness, chemical oxygen demand, (COD), PO4-P, SO4, NO3 and NO2 were determined as reported (APHA 1998; Kazi et al. 1987; Khuhawar et al. 2018). The Orion star 5 conductivity meter (Orion Inc Boston, M.A, USA) was used to evaluate pH, electrical conductivity, total dissolved solids (TDS) and salinity. The electrodes were appropriately calibrated before analysis. The spectrophotometric measurements were taken out on Hitachi 220 UV/Visible (Hitachi (Pvt) Ltd, Tokyo, Japan), double-beam spectrophotometer with 1 cm quartz cuvettes. The elements Na, K, Ca, Mg, Pb, Co, Cr, Mn, Ni, Cd, Fe and Cu were analysed by flame atomic absorption spectrophotometer (FAAS) using a Perkin Elmer AA 800 (Perkin Elmer, Singapore) at the conditions recommended by the manufacturer. The determinations were carried out at least in triplicate (n = 3) with integration time 3 s and delay time 3 s. The equipment was controlled by a computer with WinLab software. Deionized double-distilled water was used for all glassware cleaning and solution preparations, stock solution of the element was prepared from pure metal salt and further solution was prepared by appropriate dilution. The blank determination (without sample) was prepared and analysed simultaneously with the samples throughout the procedures. Anions and cations balance method was used to determining the reliability of the major ions analysis of groundwater (Boyd et al. 2007) and scatter diagram plot of fluoride versus TDS was drawn using (Microsoft Excel 2013). The coefficient correlation (r) was carried out as reported (Batabyal 2014). The cluster analysis was created by ward method (Panda et al. 2006). The principal component analysis (PCA) was analysed (Simeonov et al. 2003) using SPSS statistical software version 22. Piper graph for anions and cations was created by using method (Piper 1953) by Aquachem software.

Analysis of the quality of water for irrigation

The salinity hazard of water is calculated based on of electrical conductivity using Richards method (Richards 1954).

The Na% is extensively applied for evaluating the suitability of groundwater for the irrigation using reported method (Wilcox 1955). The Na% was calculated by formulas

$${\text{Na}}\% = \left[ {\left( {{\text{Na}}^{ + } + {\text{K}}^{ + } } \right)/\left( {{\text{Ca}}^{2 + } + {\text{Mg}}^{2 + } + {\text{Na}}^{ + } + {\text{K}}^{ + } } \right)} \right] \times 100.$$

The sodium adsorption ratio was determined by Todd (1980). The SAR value is determined using the following formula.

$${\text{SAR}} = \frac{\text{Na}}{{\sqrt {\frac{{{\text{Ca}} + + {\text{Mg}} + + }}{2}} }}.$$

The permeability index (PI) was determined to check the quality of water for irrigation using reported method (Doneen 1964). The PI is determined by following equation.

$${\text{PI}} = \left[ {\left( {{\text{Na}}^{ + } + {\text{HCO}}_{3}^{ - } } \right)/\left( {{\text{Ca}}^{2 + } + {\text{Mg}}^{2 + } + {\text{Na}}^{ + } } \right)} \right] \, \times \, 100.$$

Chloroalkaline indices were determined by using method (Schoeller 1977). The CAI-1 was calculated by the below equations.

$$\left( {{\text{CAI}} - 1} \right) = \left[ {{\text{Cl}}^{ - } - \left( {{\text{Na}}^{ + } + {\text{K}}^{ + } } \right)} \right]/{\text{Cl}}^{ - } .$$

Kelly index is applied to measure the suitability of water sample for the irrigation using method (Kelly 1940). KI value was determined by following equation.

$${\text{KI}} = {\text{Na}}^{ + } /{\text{Ca}}^{2 + } + {\text{Mg}}^{2 + } .$$

Residual sodium carbonate (RSC) is used to measure the harmful effect of HCO3 in water using method (Raju 2007). RCS is calculated by following formula.

$${\text{RSC}} = \left( {{\text{CO}}_{3}^{ - } + {\text{HCO}}_{3}^{2 - } } \right) - \left( {{\text{Ca}}^{2 + } + {\text{Mg}}^{2 + } } \right).$$

The chloride–sulphate ratio is applied to measure the suitability of water for irrigation using method (Al-Harbi et al. 2009). Chloride–sulphate ratio was determined by following equation:

$${\text{Chloride}}\;{\text{sulphate}} = {\text{Cl}}^{ - } /{\text{SO}}_{4}^{2 - } .$$

Chloride bicarbonate ratio is applied to measure the suitability of the water for irrigation using method (Al-Harbi et al. 2009). Chloride bicarbonate was determined by following equation:

$${\text{Chloride}}\;{\text{bicarbonate}} = {\text{Cl}} /{\text{HCO}}_{3}^{ - } .$$

The calculations of all the above equations were based on the concentration unit milli equivalent/L.

Results and discussion

The pH results of area varied from 7.0 to 8.37, it showed that pH of all samples was within limits of WHO. The − log of hydrogen ion concentration (pH) is an essential factor in water investigation and calculation of alkalinity, acidity of the any sample and the processes such as corrosion control, coagulation and disinfection (Sujatha et al. 2012). The electrical conductivity (EC) results of area varied from 373 to 18700 µS/cm; the EC of 22 (57.89%) samples was above the limits of WHO. It may be due to the geological nature of study area. EC determines the soluble salts of water in the form of the ions. There is an increase in the value of electrical conductivity due to the presence of salts in water (Trivedi and Goel 1986). The total dissolved solids (TDS) results varied from 238 to 11,968 mg/L; the TDS of 16 (42.12%) samples were within limits of WHO (1000 mg/L). The TDS in water are due to the presence of organic and inorganic salts and substances. The drinking water quality is changed by the presence of soluble salts; water comprising high TDS may have effects on human life. The total dissolved solids (TDS) may disturb the durability and strength of palatability of food cooked (Swamy 1991). The concentration of chloride (Cl) was found from 22 to 5019 mg/L, the Cl of 16 samples was within limits, and 22 samples were above the WHO limits (250 mg/L). The chloride naturally occurs in groundwater as well as surface water. High concentration of chloride (Cl) in water is known to be indicator of contamination (Sharma and Pande 1998). The higher value of chloride (Cl) may be due to the improper discarding of sewage wastes. The excess concentration of chloride causes vascular disease, steel corrosion and salty taste to water and decreases the strength of concrete. The concentration of total hardness (TH) was found between 110 and 3200 mg/L, the TH of 24 samples was within limit and 12 samples above the WHO limit (500 mg/L as CaCO3). TH is defined as the amount of magnesium (Mg) and calcium (Ca) in the water (Jayalakshmi et al. 2011). High concentration of hardness may cause kidney and heart problem. The results of alkalinity were found from 100 to 530 mg/L, the alkalinity of 20 samples was within limits, and 18 samples were above the WHO limits. It is composed mostly of CO3 and HCO3. Very high level of alkalinity may cause operational effects, like foaming. The extremely higher causticity values may result in a form of corrosive effect of the boiler which is called ‘embrittlement’ (Patil et al. 2012). The sulphate (SO4) ions are easily soluble in natural water. Many SO4 ions are yielded by their minerals by oxidation process; sulphate is also present in the industrial wastes. The concentration of sulphate of study area was found from 29 to 2231 mg/L, the sulphate of 19 samples was within limits, and 19 samples above the WHO limit (250 mg/L). Chemical oxygen demand (COD) is quantity of organic pollution in natural water. COD is the quantity of oxygen required for oxidation of the organic substance in the water. It is usually used in the waste water handling but little amount is present in drinking water treatment (Milacron Marketing Co). The results of COD were found from BDL to 48 mg/L; the COD of 10 samples were above the WHO limits. The higher nitrate (NO3) and nitrite (NO2) levels are caused by groundwater pollution from extreme use of fertilizers, animal waste or seepage of sewage. The nitrite (NO2) is of specific health distress in human body due to change of the haemoglobin in our blood to methaemoglobin. This situation is called methaemoglobinemia (Sabo and Christopher 2014). Nitrite NO2 can react with the secondary amines in the human stomach to produce the extremely cancer-causing nitrosocompounds. The concentration of nitrate and nitrite was found from 0.36 to 12.11 mg/L and 0.002 to 3.52 µg/L, respectively. Nitrate of  35 samples were within limits (10 mg/L), but nitrite results of  all samples were above the WHO limits (5 µg/L). The phosphates (PO4) exist in different inorganic forms in both water and soil. The main source of phosphates (PO4) can be anthropogenic depending on activities happening in area (American Public Health Association 1915). The phosphorus (P) is a plants nutrient and also frequently controls the aquatic plant growing in the water. Usually, groundwater comprises less phosphorus levels for the reason of less solubility of the natural phosphate ore and the capability of soils to preserve phosphate. The concentration of total phosphate and orthophosphate was found from 0.018 to 0.95 mg/L and 0.002 to 0.515 mg/L, respectively (Table 2). The total phosphate and orthophosphate of all samples were within limits of WHO.

Table 2 Results of physicochemical parameters
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The sodium (Na) is present in the ground as well as surface water. The presence of sodium (Na) in natural water depends upon the existence of anions in that system and the temperature of area. The high value of sodium imparts taste to the drinking water and may cause high blood pressure and cardiovascular disease (Poverty and Kopka 1995). The concentration of sodium was founded from 19 to 1442 mg/L. The sodium of 21 samples was within limits of WHO (200 mg/L), and 17 samples were above the limits. The concentration of potassium (K) of study area was found from 5 to 150 mg/L. The potassium of 14 samples was within limits, and 24 samples above the WHO limits (12 mg/L). The potassium (K) plays an essential role in the metabolism process of living organism, and it is also an essential micronutrient (animals and plants). Higher concentration may cause kidney, lungs and cardiovascular diseases. The calcium (Ca) and magnesium (Mg) are abundant in soil and rocks. They are moderately dissolved in the surface water and then enter into the groundwater. The Ca and Mg are not of health concerns, unless present in higher amount in drinking water (Kandhro et al. 2015). High concentration of Ca and Mg source of water is hardness. The concentration of calcium and magnesium was found from 17 to 947 mg/L and 15 to 801 mg/L, respectively. The results of calcium and magnesium of 20 samples were within limits of WHO (Ca and Mg 150 and 100 mg/L, respectively) (Table 3).

Table 3 Results of essential, heavy and toxic elements
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The residents are unprotected to lead (Pb) from food and air. The kids are mostly at risk to lead (Pb) exposure; it is permeable from blood brain barricade and has neurotoxin effects even Pb at less level of exposure (Athar and Vohora 1995). The concentration of Pb of study area was found from BDL to 37.4 µg/L; the results of Pb of 30 samples were within limits of WHO (10 µg/L). The chief exposure way of the inorganic Pb is through adsorption by stomach tract and breathing inhalation. The copper (Cu) is important for the creation of enzyme in the human beings. Extremely high dosages of Cu intake effect to mucosal corrosion, irritation, renal damage and harm central nervous system (Ahmed and Krishnamurthy 1990). The concentration of Cu of study area was found from 3.7 to 81.4 µg/L. The Cu results of all samples were within limits of WHO. The cadmium (Cd) has been used in the industries for a long time. The food smoking of cigarettes and water are the main source of Cd. Daily nutritional consumption of Cd is from 40 to 50 µg/day. The concentration of cadmium of study area was found from BDL to 25.9 µg/L; the Cd results of 28 samples were within limits of WHO (3.0 µg/L). The Cd gathers within the liver and kidney over long time. Long period contact with Cd leads to cancer and cardiovascular diseases. It disturbs renal tubular system of the amino acids, sugar and reabsorbing proteins (McLaughlin et al. 1999). The values of chromium (Cr) of study area were found between BDL and 100 µg/L. The results Cr of 22 samples were within limits of WHO (70 µg/L). The daily intake of Cr ranges from 100 to 300 µg/day. The dangerous effects of chromium to human beings are commonly related with hexavalent (Cr+6) form. The chromium poisonousness comprises membrane ulcers and liver necrosis (O’Brien et al. 2003). The nickel is present in small concentration in the groundwater. Daily consumption of Ni through vegetables and food is about 300 µg. The values of nickel of study area were between 6.9 and 140 µg/L; the results Ni of 23 samples were within limits of WHO (70 µg/L). The higher level of nickel causes eosinophilic pneumonitis, conjunctivitis. Ni is comprising prostheses like joint replacements, cardiac valve replacements, pins, dental inlays and cardiac pacemaker wires (Athar and Vohora 1995). The cobalt results of study area were between 0.1 and 60.7 µg/L; the Co results of all samples were within limits of WHO. Low concentration of cobalt is present naturally in surface, sea and groundwater. Nevertheless, high levels of Co in the water and soil may be due to the anthropogenic activities including Co-bearing minerals and mining (Smith and Carson 1981). Manganese (Mn) is necessary nutrient and daily requirement of Mn is approximately 2.5 to 5.0 mg for adults (Athar and Vohora 1995). The results of manganese of study area were between BDL and 95.3 µg/L. The Mn results of all samples were within limits of WHO. Manganese is fairly less harmful to human but may causes serious harming result at higher values. The nervous illness is caused due to the exposure of manganese dust fume to occupation workers (Järup 2003; NRC-NAS 1980). Iron (Fe) is an essential constituent in our body metabolism. It is existing in higher quantity than other trace elements. Iron is a constituent of proteins, haemoglobin and enzymes. The Fe results of study area were between 15.4 and 279 µg/L; the Fe results of all samples were within limits of WHO (Dietary Reference Intake 2001). The average values of heavy metals for all the samples were present in the following decreasing order Fe > Ni > Cr > Mn > Cu > Co > Pb > Cd (Table 3).

The results of arsenic for study area were between BDL and 25 µg/L, the results of As of 37 samples were within limits of WHO and only one sample was above the limit. The exposure to arsenic is mainly due to the intake of drinking water and food. The long-term exposure to As in water is mostly associated with increased threats of hyperkeratosis, skin cancer and pigmentation variations (Järup 2003; Franzblau and Lilis 1989). The fluoride is abundant in earth’s crust as a form of minerals. The large number of human population depends on the geographical site of the inhabitants. The chief causes of fluoride (F−) in groundwater are F− containing rocks which inter in water through weathering and leaching of fluoride. Fluoride (F) is present as calcium fluoride (CaF2), cryolite (Na3AlF6), fluorspar or apatite phosphate [Ca3F (PO4)]3. The concentration of fluoride is five times greater in granite than basalt rock. Similarly, shale has a greater concentration than limestone and sandstone (Maheshwari 2006). The fluoride result of study area was found between 0.25 and 25.7 mg/L (Table 3), the results F− of 15 (39.47%) samples were within limits of WHO (1.5 mg/L), four (10.53%) samples were found in maximum permissible limits of WHO (3.0 mg/L), and 19 (50%) samples were above the maximum limits (> 3.0). The higher concentrations of fluoride in water may have significant health effects. The fluoride results indicated that collected groundwater samples of study area were seriously contaminated by presence of fluoride (F−) ion, whereas distribution pattern indicated high concentration of F− in taluka Shahdadkot and low concentration was found in Sijawal Junejo taluka. The concentration of fluoride (F−) is governed by the solubility of fluoride. High level of fluoride causes fluorosis.

Correlation coefficient

The coefficient of determination was examined of parameters of study area to each other. The pH was less correlated with Cu and As (< 0.5) but was negative correlated with other parameters. Total hardness was good correlated with TDS and Cl (> 0.7), sodium was good correlated with TDS, TH, Cl and sulphate but moderately correlated with alkalinity (0.5–0.7). Calcium and magnesium were good correlated with TDS, Cl, TH and SO4 but moderately correlated with alkalinity. Fluoride was good correlated with alkalinity, moderately correlated with K but less correlated with TDS, Cl, TH, SO4, Cr, Mn, Ni and Pb (< 0.5). The correlation showed that the major parameters were good correlated with each other which indicated that these samples were in the similar locations (Table 4).

Table  4 Correlation determination of the parameters
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Cluster analysis (CA)

The cluster analysis method was used for the 38 water samples of area to know the similarity among sampling locations (Fig. 1). The samples were observed to be grouped into clusters in dendrogram. Group A is based on 16 samples with samples numbers 30, 35, 31, 16, 26, 28, 29, 5, 6, 37, 32, 33, 3, 7, 4, 9 and showed similarity of samples; B group contains 13 samples with numbers 8, 22, 20, 36, 14, 24, 12, 38, 19, 2, 34, 13, 25, 10. The cluster C comprises two groups C1 and C2, the C1 contains three samples 11, 21, 17, and C2 contains four samples 1, 15, 18, 27. It is observed that group C samples have higher values for most of parameters than groups A and B. The group B has higher values in terms of average concentration then group A.

Fig. 1
figure 1

Cluster analysis dendrogram of the samples

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Hydrochemical composition

It was applied to describe the hydrochemical composition structure in two similar triangles with diamond to top in this diagram (Chadha 1999). The cations are grouped as Ca, Mg, Na, K in left trilinear and anions Cl, HCO3, SO4 in right trilinear which indicated the nature of groundwater.

The 38 groundwater samples were applied for the diagram. The piper diagram showed the hydrochemical composition of the study area. The triangle right showed predominance of Cl− towards HCO3− and SO42−, and (triangle left) showed slightly predominance of Na+ and K+ towards Ca2+ and Mg2+. The right side of triangle indicated groundwater samples were rich in chloride, also indicated chloride-type water. The left side of triangle indicated slightly sodium-type water. The Ca2+, Mg2+ and Cl−, SO42− were found at both sides simultaneously, and arrows raised upwards within diamond shape of diagram (Fig. 2). The most of samples gathered upwards Ca2+ and Cl− and also indicated that the water samples were calcium and chloride type.

Fig. 2
figure 2

Piper diagram of the samples

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Scatter diagram analysis

The scatter diagram is used to identify the relationship between two variables on Y and X axis. If the variables are correlated with each other, the curve will be linear, and the diagram showed Y axis indicated the fluoride values and X axis indicated the TDS concentration. The first cluster of dots gathered between TDS 500 and 1000 mg/L; second cluster of dots gathered between TDS 2000 and 3000 mg/L. It is observed that the concentration of fluoride increased with increase in the value of TDS except samples number 13 and 15, where the concentration decreased (Fig. 3).

Fig. 3
figure 3

Scatter diagram of fluoride versus TDS

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Principal component analysis (PCA)

Principal component analysis (PCA) is powerful tool that attempts to describe the variance of the large data set of inter-correlated variables with the smaller data set of independent variables. It extracts an eigenvalues from covariance matrix of original variables and weighted linear combination of original variables. The rotated components matrix for 25 physicochemical parameters of the water samples of study areas are shown in Table 6. It includes loading components for rotated matrix, eigenvalues for six components, and cumulative percent of variance described by each component. It shows that six rotated principal components account together for 89.038% of the total variance of the data set, in which the first component account for 39.971%, second 11.451%, third 11.389%, fourth 9.259%, fifth 9.166% and sixth 7.802% of total variance. The eigenvalues of first component were greater than others and can be used to evaluate the leading of hydrogeochemical process. The component 1 which is based on load 39.971% indicated for parameters conductivity, TDS, salinity, chloride, sulphate, total hardness, sodium, calcium, magnesium, and lead with high positive loading (0.956–0.990), potassium and alkalinity was with medium positive loading (0.503–0.633), and F, Cr, Cu and O-PO4 low positive loading (0.02–0.295). Similarly the component 2 which has 11.451% indicated high loading only for COD and NO3 (0.735–0.757), moderate positive loading for pH (0.507) and low positive loading for calcium, total hardness, sulphate, fluoride, Pb, Fe, Mg, Cr, As, NO3, T-PO4, O-PO4 and alkalinity (0.152–0.473). The component 3 which has loading of 11.389% has good positive loading for F and K (0.833–0.858), moderate positive loading for alkalinity (0.656) and low positive loading for conductivity, TDS, salinity, Ca, Mg, Na, SO4, total hardness, Cd, Fe, Cr, Ni, COD, Mn, NO3, T-PO4, and O-PO4, (0.006–0.375). The component 4 which has loading of 9.259% has good positive loading for Cu and As (0.826–0.869) and low positive loading for conductivity, TDS, salinity, Ca, Mg, Na, SO4, total hardness, Cl, alkalinity, sulphate, Cr, Ni and Pb (0.019–0.201). The component 5 which has loading of 9.166% has good positive loading for O-PO4 and Mn (0.805–0.826), moderate positive loading only for Co (0.522) and low positive loading for conductivity, TDS, alkalinity, Mg, Na, F, Cd, Cr, Ni, COD, NO3, NO2 and T-PO4 (0.005–0.465) (Table 5). The component 6 which has loading of 7.802% has good positive loading for T-PO4 (0.896), moderate positive loading only for pH (0.569) and low positive loading for conductivity, TDS, salinity, alkalinity, T hardness, K, Mg, Cd, Cr, Ni, Mn, COD, NO3 and O-PO4 (0.005–0.465). It reflects the composition of the components within the water bodies at study area.

Table  5 Rotated principal component of the parameters
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Ions balance

The ions balance method was used for the seven major parameters of groundwater, cations Na, K, Ca, Mg and anions Cl, SO4 and HCO3. The pie chart showed predominance of chloride than other parameters 23.86 meq/L, and potassium was found to have the lowest value than other parameters 0.74 meq/L. The ions balance results were in meq/L Na 13.85, K 0.74, Ca 12.05, Mg 14.91, Cl 23.86, SO4 11.27 and HCO3 6.11 meq/L. The sum of cation 41.55 and sum of anions 41.24 meq/L and error percentage 0.75% meq/L were observed in the ions balance equation (Fig. 4).

Fig. 4
figure 4

Pie chart of anions and cations

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Suitability of water for irrigation

Salinity hazard

Low-salinity groundwater (EC < 500 μS/cm) can be used for agriculture of most cultivation, and salinity of soil will not be developed. Only two (5.26%) samples were found in low-salinity category (Fig. 5). Medium salinity (EC 500–1000 μS/cm) may be used for the soils washed with enough volume of water. Most of the crops with moderate quantity of salt may grow without using special procedures for the regulation of the salinity. Four (10.52%) samples were found in medium-salinity category. Water with high salinity (EC 1000–3000 μS/cm) cannot be used on the soils without controlled drainage. Special managing of salinity and selection of crops will require best salt tolerance even for the soils with suitable drainage. Fifteen (39.47%) samples were found in high-salinity category. Very high salinity (EC > 3000 μS/cm) is not fit for crops under normal conditions; nevertheless, it may be used under very special conditions. The soils may be necessary permeable, drainage must be tolerable, and water must be used in extreme quantities in order to certify higher level of soil leaching to be able to cultivate crops that are very high salt tolerant. Seventeen (44.73%) samples were found in very high-salinity category (Fig. 5).

Fig. 5
figure 5

Salinity hazards

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Sodium percentage

The Na% results of water are divided in the three categories (20–40 Na%) good, (40–60 Na%) permissible and (60–80 Na%) doubtful. The Na% of study area was found between (21.6 and 61.3 Na%), 26 samples were within (20–40 Na%) as good, 11 samples were between (40 and 60 Na%) permissible, and only one sample was in (60–80 Na%) doubtful category.

Sodium adsorption ratio (SAR)

The results of SAR in study areas varied from 0.66 to 8.30 meq/L, the SAR values of 33 samples were suitable (SAR < 6), and five samples were above the limits for irrigation (SAR > 6).

Permeability index (PI)

The permeability index PI in the study area was found between 34.2 and 96.6 meq/L. According to the present study, the 17 samples (44.74%) were in high permissibility PI, (75%) Class I which were good for irrigation and 12 samples (31.58%) were between 50 and 75% (Class II), and were suitable for irrigation and nine samples (23.68%) were in less than 50% permissibility (Class III) which were unsuitable for irrigation purposes (Table 6).

Table  6 Suitability of water for irrigation
Full size table

Kelly’s index (KI)

The KI (< 1) showed suitability for irrigation and KI value (> 1) showed high level of Na and not fit for irrigation. Kelly’s index KI in the investigated area was from 0.20 to 1.52 meq/L. According to the present study, 35 water samples were suitable and three were unsuitable for irrigation.

Residual sodium carbonate

RSC is divided in three categories (< 1.25 ‘safe’), (1.25–2.5 ‘marginal’) and (> 2.5 ‘unsuitable’). The RSC value of all samples was founded in ‘safe’ category (< 1.25 meq/L).

Chloroalkaline indices

If CAI-1 value is negative (−), it means the base exchange occurs among Na+ and K+ in groundwater with Ca2+ and Mg2+ in the soils, and if CAI-1 value is positive (+), it indicates there cannot be base exchange. A total of 14 samples CAI-1 values were founded in negative, and 24 samples were founded positive.

Chloride–sulphate ratio (Cl−/SO4 2−)

The chloride–sulphate ratio of the study area was between 0.62 and 6.60 meq/L. If (Cl−/SO42−) is less than one, the sample is suitable for irrigation, and if (Cl−/SO42−) value is higher than 1, it means the sample is salty and not suitable for irrigation. The 33 samples of the present study indicated chloride–sulphate ratio greater than one, and five samples were less than one (Table 6).

Chloride bicarbonate ratio

The chloride bicarbonate in the study area was found between 0.29 and 21.42 meq/L. If chloride bicarbonate ratio is less than one, the sample is suitable, and if ratio is above than 1, the sample is not suitable for irrigation. The 24 samples indicated chloride bicarbonate ratio greater than one and 14 samples were less than one (Table 6).

Conclusion

The present study analysed the groundwater of three talukas of District Qambar Shahdadkot. The samples analysed were compared with standard values of WHO for drinking water. The pH value of all samples was within limits. The results of electrical conductivity and total dissolved solids of 57.89% were higher than WHO limits. The concentration of anions and cations of about half of samples was above the limits. The concentration of fluoride in 50% was above than maximum permissible limits of WHO. The heavy metals like Fe, Mn, Co and Cu of all samples were within permissible limits of WHO, but concentration of Cr 49.42%, Ni 21.05%, Cd 28.94% Pb 18.42% and NO3−-N 7.89% samples was higher than permissible limits of WHO. The heavy metals were present in following decreasing order Fe > Ni > Cr > Mn > Cu > Co > Pb > Cd. The high concentration of Ni, Cr, Pb and Cd may due to the drainage waste water and geological nature of area. The concentration of, NO2−-N, T-PO43−-P and O-PO43−-P and COD of 10 samples were above  than limits; arsenic of only one sample was above the permissible limits of WHO. The concentration of Cl and K 60.52%, hardness 36.84% and SO42− 52.63%, Na, Ca, Mg and alkalinity 47.36% were higher than permissible limits of WHO. The water quality of study area at (57.89%) places is not suitable for human consumption. The taluka Shahdadkot was more contaminated than other two talukas and taluka Sijawal Junejo was less contaminated by TDS and the majority of samples were suitable for human consumption as well as irrigation. However, it could be used for irrigation with controlled drainage, keeping in view the quality of groundwater and the nature of soil.