The aim of this study was to evaluate the quality and hydrochemical characteristics of urban groundwater in Urmia City, northwest of Iran. In order, 59 groundwater samples were collected and analyzed for various anions and cations. Result shows that, mineral weathering, ion exchange and anthropogenic activity are the main hydrochemical processes controlling urban groundwater chemistry. The evaluation of groundwater geochemistry in the flow path beneath the urban area shows that, due to land use changes, the hydrochemical change occurs predominantly in electrical conductivity (EC), Cl and NO3. The EC is increased in the direction of groundwater flow and in the last decade in industrial areas. According to the groundwater quality index values, most of the samples fit into the good quality class and samples with poor quality are located in the old residential, parks and agricultural areas of the city. The calculation of the irrigation water quality indices (Na%, sodium adsorption ratio, permeability index, residual sodium carbonate), and industrial water quality indices (Ryznar stability index, Langelier saturation index, Larson–Skold, Puckorius scaling index) indicated that the quality of water for irrigation purposes could be classified in the excellent to permissible categories. However, as for the industrial uses, the results also revealed that most of the samples could be classified in the aggressive and very aggressive categories.

INTRODUCTION

Sustainability of urban water supplies is a critical challenge for over half the world's population of 7 billion, which lives in urban areas (Howard 2015). Intensive development of urban areas has led to high demand for groundwater resources in arid and semi-arid areas of the world such as Iran, putting these water resources at greater risk of contamination (Aghazadeh & Mogaddam 2010; Esmaeili et al. 2015; Nematollahi et al. 2016). In urban areas, groundwater contamination may be due to natural sources or numerous types of human activities such as urban runoff infiltration, the leakage of wastewater, disposal of domestic sewage, septic tanks, leakage in landfill areas, and industrial activities (Dechesne et al. 2004; Benouara et al. 2016; Nan et al. 2016). Previous researches have shown urbanization and extensive industrial activities have resulted in contamination of aquifers in urban areas (Taniguchi et al. 2007; Kazemi 2011; Martin del Campo et al. 2014; Oiste 2014; Jabal et al. 2015; Rai & Saha 2015; Mohamed & Hassane 2016; Yan et al. 2016). In order to evaluate and manage the groundwater resources in urban areas, it is needed to have an understanding of hydrogeological and hydrochemical properties of the aquifer and also the effect of human activities on the quality of groundwater.

Rapid urbanization has happened in Urmia City, and caused fast growth in this city during the last few years. Therefore, population increase and expansion of urban areas has affected the quality and quantity of groundwater. This study focuses on groundwater contaminations in the urban area of Urmia; it describes the hydrogeochemical changes that are taking place in the groundwater flow and assesses the quality of groundwater for its suitability for drinking, irrigation and industrial purposes.

MATERIALS AND METHODS

Description of the study area

The study area is located in West Azerbaijan province and Urmia Lake basin (Figure 1). Urmia City, with more than 0.7 million population is the second largest city in the northwest of Iran. In the last five decades the population growth has been doubled and expansion of urban areas has been more than five times. According to the investigations, 66.5% of the total 100 km2 of land of Urmia City is used for residential, transportation and social services purposes and 33.5% are gardens, farms, cemeteries, open areas and arid lands (MRUDI 2015) (Figure 1). In 2005 and 2015, the steady growth of built-up area has covered about 47% and 66.5% of the total area under this category, respectively. The agricultural land also covered about 24% and 9% of the area in 2005 and 2015, respectively. Based on the structural division of Iran, the study area is located in the Alborz–Azerbaijan zone (Nabavi 1976). The main lithological units around Urmia City include alternation of limestone, sandstone, conglomerate and marl with age from the Miocene to Oligocene (Figure 2). According to well and borehole logs, the aquifer in the study area is unconfined and consists of gravel, silty sand and clay sediments with medium grain (Aghazadeh et al. 2012). The thickness of the alluvium aquifer is 21–87 m and the depth of groundwater is 1–32 m. (ARWA 2015). The general groundwater flow direction in urban area is from West to East (Aghazadeh et al. 2012). The depth of groundwater in the suburbs area is different between 1 and 17 (Figure 3).
Figure 1

Location and land use map of study area.

Figure 1

Location and land use map of study area.

Figure 2

Geology map of study area and groundwater sample points.

Figure 2

Geology map of study area and groundwater sample points.

Figure 3

Depth of groundwater map in study area.

Figure 3

Depth of groundwater map in study area.

Groundwater sampling and analysis

In this study, 59 samples from water wells and boreholes located in urban and suburb areas were collected and analyzed during May 2015. The collected samples were analyzed for various chemical parameters as defined by the American Public Health Association (APHA 1995). The pH and electrical conductivity (EC) were measured using digital conductivity meters immediately after sampling. Anions and cations (Ca2+, Mg2+, Na+, K+) were analyzed by titration, flame photometer and spectrophotometer methods. Based on the physico-chemical analyses, some important parameters and indices were calculated. Saturation indices for carbonate and sulfate minerals and chemical facies were also computed via computer programmers of PHREEQC and AQUCHEM. In this study, ions ratio, various indices and different graphical representations were used for the classification of water and to study the suitability of groundwater for different purposes. Also, the suitability of the groundwater for drinking uses was evaluated by comparing with World Health Organization guidelines (WHO 2011).

RESULTS AND DISCUSSION

Groundwater chemistry

The findings of chemical analysis on samples are shown in Table 1. Results show that the values of pH in the samples are varied from 6.9 to 8.24 with a mean value of 7.6. These values show that the groundwater in this area is generally neutral to slightly alkaline in nature. According to WHO (2011), standard pH values of all the samples are within the safe limit. Concentration of ions present in the water has a direct effect on the EC. The EC of groundwater varies between 440 and 1,790 μS/cm with a mean value of 933 μS/cm. The variation of EC in the groundwater of the study area is related to anthropogenic activities and geochemical processes. Assessment of electrical conductivity shows that EC increased in the direction of groundwater in urban areas and the mean value in the suburbs is 1,219 mg/l. In 93% of the groundwater samples the enrichments of salts are low (EC < 1,500 μS/cm) and groundwater samples have EC below the standard value given by the WHO standard (1,500 μS/cm). The remaining samples are medium (EC = 1,500 and 3,000 μS/cm) and have EC above standard limit.

Table 1

Summary statistics of the analytical data in the study area

Parameters Units Minimum Maximum Mean Standard deviation Most desirable limits (WHO 2004, 2011Maximum allowable limits (WHO 2004, 2011
pH – 6.9 8.24 7.63 0.22 6.5 8.5 
EC μS/cm 440 1,790 923.58 323.93 1,400 – 
TDS mg/l 337 1,128 539.2 153.74 500 1,500 
Na mg/l 118.0 30.36 25.6 – 200 
mg/l 0.00 31.20 2.99 3.92 – 20 
Ca mg/l 46.00 146.20 90.75 24.43 75 200 
Mg mg/l 12 85.08 23.4 11.25 50 150 
Cl mg/l 10.50 162.95 45.37 30.71 250 600 
HCO3 mg/l 140.30 488.00 299.65 63.18 – 300 
SO4 mg/l 29.00 239.20 65.09 34.93 200 400 
PO4 mg/l 0.00 1.00 0.04 0.18 – 250 
NO3 mg/l 140.3 32.2 18.9 – 45 
TH mg/l 165 605 323.56 87.99 100 500 
TA mg/l 115 400 245.61 51.78 – – 
SAR – 0.2 3.67 0.77 0.76 – – 
%Na 5.1 57.3 17.2 11.9 – – 
RSC meq/l −5.90 0.60 −1.56 1.09 – – 
PI 31.51 80.96 45.47 11.16 – – 
SI calcite – −0.7 1.09 0.41 0.28 – – 
SI dolomite – −0.74 2.07 0.48 0.52 – – 
SI gypsum – −2.3 −1.3 −1.78 0.21 – – 
SI anhydrate – −2.54 −1.6 −2.15 0.20 – – 
SI aragonite – −0.54 0.95 0.24 0.26 – – 
Parameters Units Minimum Maximum Mean Standard deviation Most desirable limits (WHO 2004, 2011Maximum allowable limits (WHO 2004, 2011
pH – 6.9 8.24 7.63 0.22 6.5 8.5 
EC μS/cm 440 1,790 923.58 323.93 1,400 – 
TDS mg/l 337 1,128 539.2 153.74 500 1,500 
Na mg/l 118.0 30.36 25.6 – 200 
mg/l 0.00 31.20 2.99 3.92 – 20 
Ca mg/l 46.00 146.20 90.75 24.43 75 200 
Mg mg/l 12 85.08 23.4 11.25 50 150 
Cl mg/l 10.50 162.95 45.37 30.71 250 600 
HCO3 mg/l 140.30 488.00 299.65 63.18 – 300 
SO4 mg/l 29.00 239.20 65.09 34.93 200 400 
PO4 mg/l 0.00 1.00 0.04 0.18 – 250 
NO3 mg/l 140.3 32.2 18.9 – 45 
TH mg/l 165 605 323.56 87.99 100 500 
TA mg/l 115 400 245.61 51.78 – – 
SAR – 0.2 3.67 0.77 0.76 – – 
%Na 5.1 57.3 17.2 11.9 – – 
RSC meq/l −5.90 0.60 −1.56 1.09 – – 
PI 31.51 80.96 45.47 11.16 – – 
SI calcite – −0.7 1.09 0.41 0.28 – – 
SI dolomite – −0.74 2.07 0.48 0.52 – – 
SI gypsum – −2.3 −1.3 −1.78 0.21 – – 
SI anhydrate – −2.54 −1.6 −2.15 0.20 – – 
SI aragonite – −0.54 0.95 0.24 0.26 – – 

EC, Electrical conductivity; TDS, Total dissolved solids; TH, Total hardness; SAR, Sodium adsorption ratio; RSC, Residual sodium carbonate; %Na, Sodium percent; PI, Permeability index; SI, Saturation index; TA, Total alkalinity.

Total dissolved solids (TDS) in the study area ranges from 337 to 1,128 mg/l. The TDS value of about 57% of the groundwater samples was above the desirable limit of 500 mg/l and 43% of the samples had a TDS value below the desirable limit. The TDS of none of the samples was more than the permissible limit suggested by WHO (Table 1). Based on TDS classification, 43% of samples collected from study area fit the desirable for drinking category (TDS < 500 mg/l), 69% of samples belong to the passable for drinking category (TDS = 500–1,000 mg/l) and only one sample belongs to the useful for agricultural purposes category (TDS = 1,000–3,000 mg/l).

Values of the total hardness (TH) are varied from 165 to 605 mg/l. All the samples have TH values above the most desirable limit and about 8% samples have TH more than the permissible limit suggested by WHO (2011) (Table 1). Based on TH classification (Table 3), 36% of samples of the study area fit the hard category (TH = 150–300 mg/l) and 64% fit the very hard category (TH > 300 mg/l). The Ca2+ and Mg2+ vary from 46 to 146 mg/l and 12 to 85 mg/l, with mean values of 90.7 and 22.4 mg/l, respectively. According to the WHO standard, all samples fall within the desirable limits for Mg2+ (250 mg/l) and Ca2+ (200 mg/l). The Na and K in groundwater samples vary between 10 and 118 mg/l and traces to 31 mg/l, respectively. The ranges of are between 140 and 488 mg/l and it is main anion in groundwater samples. The Cl in groundwater samples of the study area varies from 10.5 to 163 mg/l. The high concentration of Cl in groundwater comes from weathering of minerals such as halite and other sources such as domestic effluents, fertilizers, septic tanks, road salt and leakages from landfills. The concentration in groundwater samples varies from traces to 104 mg/l. About 80% of groundwater samples have concentration below the tolerance limit of 45 mg/l (WHO 2011) and the remaining samples have above tolerance limit.

Hydrochemical evaluation

For evaluating the hydrochemical processes and chemical properties of groundwater in the study area, the major ion chemistry was used to identify the geochemical processes. Correlation between Ca2+ + Mg2+ and Na+ + K+ with TC (total cation) (Figure 4(a) and 4(b)) shows that all of the samples are below the theoretical line (1:1), so in the groundwater of the study area, ion exchange and mineral weathering are the dominant process in the supply of cations. In order to identify the mechanisms of acquiring salinity in semi-arid regions, the Na–Cl relationship has often been used. There is a good correlation between Na and Cl (r = 0.67) (Figure 4(e)) suggesting in some groundwater samples a halite source for Na. The Na/Cl ratio of 46% of the samples was around or above 1, which indicates that that ion exchange process in groundwater samples is prevalent (Figure 4(c)). Figure 4(d) shows that the ion exchange reaction process appears to be responsible for contributing the higher concentration of Na+ in the groundwater. In Figure 4(e), samples show a trend of (Ca2+ + Mg2+)– versus Na+−Cl with a negative slope of less than unity. It suggests that controlling the quality of groundwater depends on the involvement of an ion exchange process and also on the involvement of other processes. If dissolutions of dolomite, calcite and gypsum are the dominant reactions in the system, the graph of Ca2+ + Mg2+ versus will feature a nearly 1:1 line (Brindha et al. 2016). Because of the excess ions, which may be due to anthropogenic input in the groundwater system, ion exchange tends to shift the points to the right. The graph of Ca2+ + Mg2+ versus (Figure 4(f)) shows that most samples fall below the 1:1 ratio line. It also shows the abundance of Ca2+ + Mg2+ relative to . Investigation of the Ca/Mg ratio indicated that dissolution of silicate minerals was one of the prime processes involved in attainment of the current chemical makeup of the groundwater. A Ca2+/Mg2+ ratio that is equal to 1 showed dissolution of dolomite rocks, while a greater ratio may represent a more dominant calcite contribution from the rocks. A Ca2+/Mg2+ ratio greater than 2 may reflects the effect of silicate minerals on the chemistry of groundwater (Ravikumar et al. 2015). In groundwater samples, the Ca2+/Mg2+ ratio is between 0.7 and 6 and the majority of the samples (73%) have Ca2+/Mg2+ ratio above 2, indicating the effect of silicate minerals on the groundwater chemistry. In this study, we used the Gibbs diagram, saturation index (SI) and Piper diagram in order to better understand the hydrochemical processes operating in the groundwater systems and to classify the groundwater.
Figure 4

Graphs of different parameters in groundwater of study area (solid line denotes 1:1).

Figure 4

Graphs of different parameters in groundwater of study area (solid line denotes 1:1).

The chemical data of groundwater samples collected in the study area are plotted in Gibbs diagrams (Gibbs 1970) (Figure 5). The clustering of the data points in Gibbs diagram indicates in all of the samples that the chemical weathering of rock-forming minerals is influencing the groundwater quality.
Figure 5

Mechanisms governing groundwater chemistry in Gibbs diagram.

Figure 5

Mechanisms governing groundwater chemistry in Gibbs diagram.

With respect to a mineral phase, the equilibrium state of water can be determined by calculating an SI using analytical data. The saturation index of a mineral is obtained from Equation (1). 
formula
1
where, IAP is the ion activity product of the dissociated chemical species in solution, Kt is the equilibrium solubility of the product for the chemicals involved at the sample temperature (Parkhurst & Appelo 2013). In Table 1, the SI for calcite, dolomite, anhydrate and gypsum are shown. The results show that 83% of the groundwater samples are saturated and supersaturated with respect to dolomite and 93% saturated and supersaturated with respect to calcite. The saturation index of dolomite and saturation index of calcite values are −0.74 to 2.07 and −0.7 to 1.09, respectively. Figure 6 shows the plots of SI against TDS for all the investigated water. All of the groundwater samples were under-saturated with respect to gypsum and anhydrite.
Figure 6

Plot of SI versus total dissolved solids (TDS).

Figure 6

Plot of SI versus total dissolved solids (TDS).

The plot of chemical data on a Piper diagram (Piper 1944) (Figure 7) shows that the major cation is Ca2+ and that the anions are , Cl. The results show that 86% of samples fall in the Ca, Mg–HCO3 field, 7% in the mixed Ca–Mg–Cl field and the remainder have Na–Cl and Ca–Cl type nature. In groundwater samples, alkaline earths (Ca2+ and Mg2+) significantly exceed the alkali (Na+ and K+), and the weak acids ( and ) exceed the strong acids (Cl and ). The sodium-chloride water type in the study area is because of the ion exchange and also anthropogenic activity. The chemical properties of groundwater and hydrochemical processes in the study area are controlled by both natural geochemical processes and anthropogenic activities.
Figure 7

Chemical facies of groundwater in Piper diagram.

Figure 7

Chemical facies of groundwater in Piper diagram.

Impact of urbanization on groundwater quality

Evolution of groundwater geochemistry in the flow path beneath the urban area in the Urmia aquifer shows that Ca2+, Mg2+, Na+, and do not greatly change and that the hydrochemical change in relation to land use in the study area appears predominantly in EC, Cl, and (Figures 8 and 9). Assessment of electrical conductivity in the study area shows that EC increased in the direction of groundwater flow and that its mean value in the suburbs is 1,219 μS/cm. Figure 9 shows the evolution of the electric conductivity value over time for five wells in the study area during 2001–2015.
Figure 8

Evolution of Ca, Mg, Na, Cl, SO4, HCO3 and NO3 in the flow path beneath the urban area in the Urmia aquifer.

Figure 8

Evolution of Ca, Mg, Na, Cl, SO4, HCO3 and NO3 in the flow path beneath the urban area in the Urmia aquifer.

Figure 9

Evolution of electric conductivity in selected sampling points in industrial and residential area of the Urmia.

Figure 9

Evolution of electric conductivity in selected sampling points in industrial and residential area of the Urmia.

The result shows that due to land use changes, electrical conductivity increased considerably in that period in industrial areas. In that period, EC in groundwater sample 41 and 22 has increased from 790 μS/cm to 1,356 μS/cm and from 780 μS/cm to 1,250 μS/cm, respectively. In groundwater samples of residential areas (samples 46, 52, 58) electrical conductivity has not increased considerably.

Due to the low depth of groundwater, the quality of groundwater in some suburb an areas is affected by penetrated runoff and stormwater (Aghazadeh et al. 2012). High amount of Cl in some groundwater samples of suburbs (34, 46 and 53) could show the effect of the runoff penetration on the quality of groundwater in the region. Bicarbonate concentration in the flow path is between 231 to 348 with an average of 284 mg/l. The result shows that, about 20% of groundwater samples (12 samples) have concentration above the tolerance limit of 45 mg/l. The groundwater samples with high nitrate are located in the old residential (samples 18, 29), park (sample 34) and agricultural area (samples 24, 46) of the city, reaching values of 63–104 mg/l. In this urban area, high nitrate are the possible result of wastewater and urban runoff effluent infiltration and fertilizer application.

Figure 10 illustrates the relationship between various anions and cations with TDS. The result shows that, samples from green space and parks have the lowest ion concentration with the lowest TDS. There are good correlations between sodium, chloride and sulfate ions with total dissolved solids. Concentrations of Na+ and Cl show an increasing trend with increasing TDS. There is also an indistinct grouping with respect to land-use type (Figure 10(a)). In the study area, high Na and Cl concentration in and out of the city is related to use of road deicing salt in winter.
Figure 10

Relationship between cations/anions and TDS in groundwater of the study area.

Figure 10

Relationship between cations/anions and TDS in groundwater of the study area.

It appears that concentration of increases with increase in TDS. The possible sources of in the study area are evaporated rocks, industrial effluents and domestic sewage.

In this study, we used the groundwater quality index (GWQI) for assessment of the variation in groundwater quality and the potential effects of urbanization on the groundwater quality in urban areas. To calculate GWQI, we used pH, TDS, PO4, NO3, TH, Mg, HCO3, Ca, SO4 and Cl parameters. The GWQI was calculated by using a weighted arithmetic index method (Horton 1965; Oiste 2014): 
formula
2
where, wi = weight of each parameter (Table 2) and n = number of parameter 
formula
3
where, qi = quality rating computed according to the formula: 
formula
4
where, Ci = Concentration of each chemical parameter, for each water sample and Si = WHO standard 
formula
5
Table 2

GWQI computation input

Groundwater quality parameter WHO 2004  Weight (wiRelative weight (wi
pH 6.5–8.5 0.1429 
TDS 500 0.1429 
Phosphates 10 0.0357 
Nitrates 45 0.1786 
TH 300 0.1071 
Magnesium 50 0.0357 
Bicarbonate 500 0.1071 
Calcium 75 0.0714 
Chlorides 200 0.1071 
Sulfate 200 0.0714 
    ∑Gwi = 28 ∑GWi = 1.000 
Groundwater quality parameter WHO 2004  Weight (wiRelative weight (wi
pH 6.5–8.5 0.1429 
TDS 500 0.1429 
Phosphates 10 0.0357 
Nitrates 45 0.1786 
TH 300 0.1071 
Magnesium 50 0.0357 
Bicarbonate 500 0.1071 
Calcium 75 0.0714 
Chlorides 200 0.1071 
Sulfate 200 0.0714 
    ∑Gwi = 28 ∑GWi = 1.000 

In this formula, Sli shows the subindex for each parameter.

According to the GWQI values classification (Figure 11), 93% samples of the study area fit into the good quality class and the rest of the samples fit into the poor class (Figure 11). The groundwater samples with poor quality are placed at the old residential, parks and agricultural area of the city. In this urban area, the septic system of the buildings not connected to the central system of sewerage (old residential) and fertilizer application (parks and agricultural) affected groundwater quality.

Water quality

In order to assess the suitability of water for drinking purposes, the hydrochemical parameters of the groundwater in the study area were compared with the specifications recommended by WHO (2011) for drinking water (Table 1).

According to WHO (2011) specification TDS, all of the samples are in the range of the maximum permissible category (Table 1). Based on TH classification, 5% of samples exceeded the maximum allowable limits. The content of and Cl has no known adverse effects on health, however in drinking water it should not exceed the safe limits of 300 mg/l and 250 mg/l respectively. The analytical data shows that in about 54% of the samples, exceeded the safe limits but that Cl was in the safe range in all samples. In 2% of water samples, the concentrations of exceed the desirable limit of 200 mg/l, which restricts its direct use for drinking purposes.

In assessing the suitability of water for irrigation, parameters like sodium percentage (Na %), sodium adsorption ratio (SAR), residual sodium carbonate (RSC), EC, permeability index (PI) and magnesium hazard are important. Wilcox (1955) classified groundwaters on the basis of EC (Table 3). Based on this classification, 34% of the samples belong to the good quality category and 66% of them belong to the permissible category. Stuyfzand (1989) classified water on the basis of concentration of Cl ion into eight divisions, as shown in Table 3. Based on this classification, 32% of groundwater samples were very fresh, 65% were fresh and 3% were brackish. In order to determine the suitability of groundwater for irrigation, SAR and %Na is an important parameter because it is a measure of alkali/sodium hazard to crops. SAR and %Na are defined by Equations (6) and (7) (Subramani et al. 2005). 
formula
6
 
formula
7
where, all ionic concentrations are expressed in meq/l. The SAR values range from 0.2 to 3.7. According to the classification suggested by Richards (1954) based on SAR values (Table 3), all of the samples belong to the excellent category. The %Na in the study area was in the range of 5.1 to 57.2% with an average of 17.2%. According to the Wilcox (1955) classification based on %Na values (Table 3), 74% of samples belong to the excellent category, 18% of samples belong to the good category and 8% of them belong to the permissible category.
Table 3

Classification of groundwater based on total hardness (TH), electrical conductivity (EC), chloride concentration, sodium adsorption ratio (SAR), sodium percent (%Na) and residual sodium carbonate (RSC)

Classification scheme Categories Ranges Percent of samples 
TH (Sawyer and McCartly 1967Soft <75 – 
Moderately hard 75–150 – 
Hard 150–300 36 
Very hard >300 64 
EC (Wilcox 1955Excellent <250 – 
Good 250–750 34 
Permissible 750–2,250 66 
Doubtful 2,250–5,000 – 
Unsuitable >5,000 – 
Cl classification (Stuyfzand 1989Extremely fresh <0.14 – 
Very fresh 0.14–0.85 32 
Fresh 0.85–4.2 65 
Fresh brackish 4.2–8.5 
Brackish 8.5–28 – 
Brackish-salt 28–282 – 
Salt 282–564 – 
Hypersaline >564 – 
SAR (Richards 1954Excellent <10 100 
Good 10–18 – 
Doubtful 18–26 – 
Unsuitable >26 – 
%Na (Wilcox 1955Excellent 0–20 74 
Good 20–40 18 
Permissible 40–60 
Doubtful 60–80 – 
Unsuitable >80 – 
RSC (Richards 1954Good <1.25 100 
Medium 1.25–2.5 – 
Bad >2.5 – 
Classification scheme Categories Ranges Percent of samples 
TH (Sawyer and McCartly 1967Soft <75 – 
Moderately hard 75–150 – 
Hard 150–300 36 
Very hard >300 64 
EC (Wilcox 1955Excellent <250 – 
Good 250–750 34 
Permissible 750–2,250 66 
Doubtful 2,250–5,000 – 
Unsuitable >5,000 – 
Cl classification (Stuyfzand 1989Extremely fresh <0.14 – 
Very fresh 0.14–0.85 32 
Fresh 0.85–4.2 65 
Fresh brackish 4.2–8.5 
Brackish 8.5–28 – 
Brackish-salt 28–282 – 
Salt 282–564 – 
Hypersaline >564 – 
SAR (Richards 1954Excellent <10 100 
Good 10–18 – 
Doubtful 18–26 – 
Unsuitable >26 – 
%Na (Wilcox 1955Excellent 0–20 74 
Good 20–40 18 
Permissible 40–60 
Doubtful 60–80 – 
Unsuitable >80 – 
RSC (Richards 1954Good <1.25 100 
Medium 1.25–2.5 – 
Bad >2.5 – 
In order to determine the hazardous effect of carbonate and bicarbonate on the quality of water for agricultural purposes, RSC and PI have been calculated by the Equations (8) and (9) (Eaton 1950; Ragunath 1987). 
formula
8
 
formula
9
Based on RSC classifications, all of the samples belong to the good category (Table 3). According to PI values, the groundwater in the study area can be classified as class II (25–75%), which means 93% of groundwater is suitable for irrigation, and 7% of the samples, are classified as class I (>75%).
In this study, applied Langelier saturation index (LSI), Ryznar stability index (RSI), Larson–Skold index (L-S index) and Puckorius scaling index (PSI) determine the corrosive and scaling ability of water samples. The LSI is calculated by using Equation (10) (Davil et al. 2009; Kumar et al. 2009). 
formula
10
The saturation pH (pHs) can be calculated as (Equation (11)): 
formula
11
 
formula
12
 
formula
13
 
formula
14
 
formula
15
The positive value of LSI shows that water is over- or super-saturated and this leads to CaCO3 depositing on the surface of the metal and therefore corrosion rates will be negligible. A negative index indicates that water is under-saturated and therefore dissolves CaCO3 and will be considered as corrosive. Calculating the LSI value for groundwater samples in the study area indicated that 10% of the samples are supersaturated and tend to deposit CaCO3 and that 90% of the groundwater samples are under-saturated, which accounts for their slight corrosive nature and tendency to dissolve CaCO3 as a result of low alkalinity and high free CO2 content. The LSI values are given in Table 4. In order to predict scaling tendencies of water, Ryznar (1944) has designed an empirical method to determine stability index. Ryznar stability index can be calculated like LSI as follows (Equation (16)): 
formula
16
Table 4

LSI, RSI, L-S, and PSI index values of water samples in Urmia City

Parameters Range Indication No. of samples Percent 
LSI (saturation capacity) <0 Waters under-saturated with respect to CaCO3 and has a tendency to remove existing CaCO3 protective coatings in pipelines and equipment 53 90 
Water is saturated (in equilibrium) withCaCO3. A scale layer of CaCO3 is neither precipitated nor dissolved – – 
>0 Water is supersaturated with respect to CaCO3 and scale forming may occur 10 
RSI (scaling capacity) <5.5 Heavy – – 
5.5–6.2 Scale – – 
6.2–6.8 No scale – – 
6.8–8.5 Aggressive 36 61 
>8.5 Very aggressive 23 39 
L-SI (interference of Cl and SO4) <0.8 Not interfere 45 76 
0.8–1.2 May interfere 11 19 
>1.2 Interfere 
PSI (scaling capacity) <5.5 Heavy – – 
5.5–6.2 Scale – – 
6.2–6.8 No scale – – 
6.8–8.5 Aggressive 40 68 
>8.5 Very aggressive 19 32 
Parameters Range Indication No. of samples Percent 
LSI (saturation capacity) <0 Waters under-saturated with respect to CaCO3 and has a tendency to remove existing CaCO3 protective coatings in pipelines and equipment 53 90 
Water is saturated (in equilibrium) withCaCO3. A scale layer of CaCO3 is neither precipitated nor dissolved – – 
>0 Water is supersaturated with respect to CaCO3 and scale forming may occur 10 
RSI (scaling capacity) <5.5 Heavy – – 
5.5–6.2 Scale – – 
6.2–6.8 No scale – – 
6.8–8.5 Aggressive 36 61 
>8.5 Very aggressive 23 39 
L-SI (interference of Cl and SO4) <0.8 Not interfere 45 76 
0.8–1.2 May interfere 11 19 
>1.2 Interfere 
PSI (scaling capacity) <5.5 Heavy – – 
5.5–6.2 Scale – – 
6.2–6.8 No scale – – 
6.8–8.5 Aggressive 40 68 
>8.5 Very aggressive 19 32 
According to the results, 61% of the samples are classified into the aggressive category and 39% of them are classified into the very aggressive category (Table 4 and Figure 12).
Figure 12

Evaluation of RSI and PSI Index for the groundwater samples in the study area.

Figure 12

Evaluation of RSI and PSI Index for the groundwater samples in the study area.

Larson & Skold (1958) found that alkalinity tends to reduce the corrosion rates of mild steel and postulated that therefore it is a natural inhibitor that participates in formation of an inhibitor film. The corrosivity of water is increased by chloride and sulfate. Interference of these anions in the formation of a natural inhibitor film is the explanation for this effect.

L-S index is used to describe the corrosiveness of water. The L-S index is the ratio of sulfate and chloride to the alkalinity in the form of bicarbonate and carbonate. 
formula
17
The value of L-S index below 0.8 indicates that chloride and sulfate do not interfere with natural inhibitor film formation while a value greater than 1.2 shows a tendency towards high corrosion. The value of the L-S index between 0.8 and 1.2 indicates that these ions may interfere with natural film formations. According to the obtained results, chloride and sulfate interfere with natural film formation in 76% of the samples, do not interfere with it in 19% of the samples and may interfere with natural film formation in 6% of the samples taken from the study area (Table 4).
To account the buffering capacity and the maximum quantity of precipitation that can bring water to equilibrium, the Puckorius scaling index (PSI) is used (Davil et al. 2009). Conveniently, the numbering systems and general interpretation of PSI are the same as for RSI. 
formula
18
where, pHeq = 1.465 log10 [Total Alkalinity] + 4.54. The result indicated that, 68% of samples are classified in the aggressive category and 32% in the very aggressive category (Table 4 and Figure 12).

CONCLUSIONS

Analysis of hydrochemical data reveals that the main groundwater type is Ca, Mg–HCO3 with alkaline earth metals exceeding the alkali metals and the main processes controlling groundwater chemistry are mineral weathering, ion exchange and anthropogenic activity. The evaluation of groundwater geochemistry in the flow path beneath the urban area shows that, due to land use changes, the hydro-chemical change appears predominantly in EC, Cl, and . The EC is increased in the direction of groundwater flow and due to land use changes it is also, increased considerably in the last decade in industrial areas. The high EC, Cl and NO3 are possibly the result of wastewater, urban runoff effluent infiltration and fertilizer application. According to the GWQI values, the quality of most groundwater samples is good. Both the groundwater samples with high nitrate and with poor quality based on GWQI values are located in the old residential, park and agricultural areas. Based on permissible limits prescribed by WHO for drinking uses, most of the groundwater is suitable for drinking purposes and only in 20% of samples is nitrate above the permissible limit. The calculated values of SAR, RSC, %Na, and PI indicated that the quality of water for irrigation uses is in the excellent to permissible category. The calculation of the LSI, RSI, L-S and PS indices for determining the industrial water quality and the corrosive and scaling ability of groundwater samples in the study area indicated that about 61% of samples can be classified into the aggressive and 39% very aggressive categories.

ACKNOWLEDGEMENTS

The authors of this study gratefully acknowledge the research vice-chancellery of Shahid Chamran University in Ahvaz and the Environmental Protection Agencies of West Azerbaijan for providing the existing relevant data. We would also like to thank Messrs Bakhshipor, Karami, Mosavi and Abdolahzadeh for their kindly help during the field visits, collection and chemical analyses of the samples.

REFERENCES

REFERENCES
Aghazadeh
N.
Nojavan
M.
Mogaddam
A. A.
2012
Effects of road deicing salt (NaCl) and saline water on water quality in the Urmia area, northwest of Iran
.
Arabian Journal of Geosciences
5
(
4
),
565
570
.
APHA
1995
Standard Methods for the Examination of Water and Wastewater
,
19th edn
.
American Public Health Association
,
Washington
, pp.
1
467
.
Azerbaijan Regional Water Authority (ARWA)
2015
Evaluation of groundwater in Urmia plain. Urmia, Iran
.
Benouara
N.
Laraba
A.
Rachedi
L.
2016
Assessment of groundwater quality in the Seraidi region (north-east of Algeria) using NSF-WQI
.
Water Science and Technology: Water Supply
16
(
4
),
1132
1137
.
Brindha
K.
Pavelic
P.
Sotoukee
T.
Douangsavanh
S.
Elango
L.
2016
Geochemical characteristics and groundwater quality in the Vientiane plain, laos
.
Exposure and Health
9
(
2
),
89
104
.
Davil
M. F.
Mahvi
A. H.
Norouzi
M.
Mazloomi
S.
Amarluie
A.
Tardast
A.
Karamitabar
Y.
2009
Survey of corrosion and scaling potential produced water from Ilam water treatment plant
.
World Applied Science Journal
7
,
01
06
.
Dechesne
M.
Barraud
S.
Bardin
J. P.
2004
Indicators for hydraulic pollution retention assessment of stormwater infiltration basins
.
Journal of Environmental Management
71
,
371
380
.
Eaton
F. M.
1950
Significance of carbonate in irrigation water
.
Soil Science
69
(
2
),
123
133
.
Horton
R. K.
1965
An index number system for rating water quality
.
Journal of the Water Pollution Control Federation
37
,
300
305
.
Howard
K. W. F.
2015
Sustainable cities and the groundwater governance challenge
.
Environ. Earth Sci.
73
,
2543
2554
.
Jabal
M. S. A.
Abustan
I.
Rozaimy
M. R.
Najar
H. E.
2015
Groundwater beneath the urban area of Khan Younis City, Southern Gaza Strip (Palestine): hydrochemistry and water quality
.
Arabian Journal of Geosciences
8
,
2203
2215
.
Kumar
H.
Saini
V.
Kumar
D.
Chaudhary
R. S.
2009
Influence of tri sodium phosphate (TSP) anti-salant on the corrosion of carbon steel in cooling water systems
.
Indian Journal of Chemical Technology
16
,
401
410
.
Larson
T. E.
Skold
R. V.
1958
Laboratory studies relating mineral water quality of water on corrosion of steel and cast iron
.
Corrosion
14
,
285
288
.
Martin del Campo
M. A.
Esteller
M. V.
Exposito
J. L.
Hirata
R.
2014
Impacts of urbanization on groundwater hydrodynamics and hydrochemistry of the Toluca Valley aquifer (Mexico)
.
Environmental Monitoring and Assessment
186
,
2979
2999
.
Ministry of Roads and Urban Development of Iran (MRUDI)
2015
Development of Urban Areas in Urmia City
.
Urmia
,
Iran
.
Mohamed
M.
Hassane
A. B.
2016
Hydrochemistry assessment of groundwater quality in Al-Ain city, UAE
.
Environmental Earth Sciences
75
,
353
.
Nabavi
M. H.
1976
Preface Geology of Iran
.
Geology Survey Iran
,
Tehran
.
Nematollahi
M. J.
Ebrahimi
P.
Razmara
M.
Ghasemi
A.
2016
Hydrogeochemical investigations and groundwater quality assessment of Torbat-Zaveh plain, Khorasan Razavi, Iran
.
Environmental Monitoring and Assessment
188
,
2
.
Oiste
A. M.
2014
Groundwater quality assessment in urban environment
.
International Journal of Environmental Science and Technology
11
,
2095
2102
.
Parkhurst
D. L.
Appelo
C. A. J.
2013
User's guide to PHREEQC (ver. 3) A computer program for speciation batch-reaction one-dimensional transport and inverse geochemical calculations
.
US Geo. Surv. Water Resources Invest. Rept.
99
4259
.
Piper
A. M.
1944
A graphic procedure in the geochemical interpretation of water analysis
.
American Geophysical Union Transplantation
25
,
914
928
.
Ragunath
H. M.
1987
Groundwater
.
Wiley Eastern Ltd
,
New Delhi
, p.
563
.
Ravikumar
P.
Somashekar
R. K.
Prakash
K. L.
2015
Suitability assessment of deep groundwater for drinking and irrigation use in the parts of Hoskote and Malur Taluks, Karnataka (India)
.
Environmental Research, Engineering and Management
71
(
1
),
15
26
.
Richards
L. A.
1954
Diagnosis and Improvement of Saline Alkali Soils: Agriculture
(vol. 160. Handbook 60)
.
US Department of Agriculture
,
Washington, DC
.
Ryznar
J. W.
1944
A new index for determining amount of calcium carbonate scale formed by water
.
American Water Works Association
36
,
472
486
.
Stuyfzand
P. J.
1989
Nonpoint source of trace element in potable groundwater in Netherland
. In:
Proceedings of the 18(th) TWSA Water Working
.
Testing and Research Institute KIWA
,
Nieuwegein
.
Sawyer
C. N.
McCartly
P. L.
1967
Chemistry for Environmental Engineering
.
Mc-Graw Hill, p 532
.
Subramani
T.
Elango
L.
Damodarasamy
S.R.
2005
Groundwater quality and its suitability for drinking and agricultural use in Chithar River Basin Tamil Nadu India
.
Environmental Geology
47
,
1099
1110
.
WHO
2004
Guidelines for Drinking Water Quality
.
Geneva
,
Switzerland
.
WHO
2011
Guidelines for Drinking-water Quality
, 4th edn.
Geneva
,
Switzerland
.
Wilcox
L. V.
1955
Classification and use of Irrigation Water (Circular 969)
.
USDA
,
Washington, DC
.
Yan
B. Z.
Xiao
C. L.
Liang
X. J.
2016
Evaluation of site and hydrogeochemistry in an urban groundwater source field
.
Water Science and Technology: Water Supply
16
(
2
),
460
472
.