Investigation of Hydrochemical Characteristics of Groundwater in the Harzandat Aquifer, Northwest of Iran

Environ Monit Assess DOI 10.1007/s10661-010-1575-4

Investigation of hydrochemical characteristics of groundwater in the Harzandat aquifer, Northwest of Iran

Nosrat Aghazadeh · A. A. Mogaddam

Received: 30 November 2009 / Accepted: 15 June 2010 © Springer Science+Business Media B.V. 2010

2+) − 2−) Abstract The Harzandat plain is part of the East Mg and weak acids (HCO3 ,CO3 .The Azerbaijan province, which lies between Marand chemical quality of groundwater is related to and Jolfa cities, northwestern of Iran, and its the dissolution of minerals, ion exchange, and groundwater resources are developed for water the residence time of the groundwater in contact supply and irrigation purposes. The main litho- with rock materials. The results of calculation sat- logic units consist chiefly of limestone, dolomite, uration index by computer program PHREEQC shale, conglomerate, marl, and igneous rocks. In shows that nearly all of the water samples were order to evaluate the quality of groundwater in supersaturated with respect to carbonate minerals study area, 36 samples were collected and an- (calcite, dolomite and aragonite) and undersatu- alyzed for various ions. Chemical indexes like rated with respect to sulfate minerals (gypsum and sodium adsorption ratio, percentage of sodium, anhydrite). Assessment of water samples from residual sodium carbonate, and permeability in- various methods indicated that groundwater in dex were calculated. Based on the analytical re- study area is chemically unsuitable for drinking sults, groundwater in the area is generally very and agricultural uses. hard, brackish, high to very high saline and alkaline in nature. The abundance of the ma- Keywords Groundwater quality · − − 2− · · jor ions is as follows: Cl >HCO3 >SO4 and Harzandat plain Hydrochemical Na+>Ca2+>Mg2+>K+. The dominant hydrochem- Hydrogeochemical processes · Saturation index ical facieses of groundwater is Na−Cl type, and + +) − 2−) alkalis (Na ,K and strong acids (Cl ,SO4 + are slightly dominating over alkali earths (Ca2 , Introduction

Understanding of the aquifer hydraulic properties B and hydrochemical characteristics of water is cru- N. Aghazadeh ( ) cial for groundwater planning and management in Department of Geology, Urmia Azad University, Urmia, 57159-44867, Iran the study area. Generally, the motion of ground- e-mail: [email protected], water along its flow paths below the ground sur- [email protected] face increases the concentration of the chemical species (Domenico and Schwartz 1990; Freeze A. A. Mogaddam Department of Geology, Tabriz University, and Cherry 1979; Kortatsi 2007). The quality of Tabriz, Iran groundwater is the resultant of all the processes Environ Monit Assess and reactions that act on the water from the and its average annual rainfall is about 280 mm, moment it condenses in the atmosphere to the which 70% of it falls during the spring and win- time it is discharged by a well (Arumugam and ter seasons. Groundwater is an important water Elangovan 2009). Hence, the groundwater chem- resource for drinking, agriculture, and industrial istry could reveal important information on the uses in the study area. Low precipitation and over- geological history of the aquifers and the suitabil- exploitation of groundwater resources in recent ity of groundwater for domestic, industrial, and years have caused an extensive groundwater level agricultural purposes. decline in this plain prohibiting further develop- Hydrochemical evaluation of groundwater sys- ment of the aquifer. tems are usually based on the availability of a large amount of information concerning groundwater chemistry. Groundwater chemistry, in turn, Geology and hydrogeology depends on a number of factors, such as general geology, degree of chemical weathering of the From a geological point of view, the investi- various rock types, quality of recharge water, and gated area is located in the Alborz–Azerbaijan inputs from sources other than water–rock inter- zone of Iran, and it is covered by Devonian action. Such factors and their interactions result to Quaternary sediments (Nabavi 1976). Triassic in a complex groundwater quality (Ayenew et al. sedimentary rocks consist of dolomite and thin 2008; Domenico and Schwartz 1990; Giridharan limestone. Jurassic and Cretaceous formations et al. 2008; Guler and Thyne 2004). in the study area chiefly comprise green shale The rapid increase in the population of the and flysch-type sediments. Andesitic, dacitic and country has led to large-scale groundwater devel- rhyodacitic igneous rocks of Devonian age are opments in some areas. Intensive cultivating and outcropped in many mountainous areas. As a urban development has caused a high demand on consequence, the Quaternary deposits are mainly groundwater resources in arid and semiarid re- characterized by silty-muddy layers alternating gions of the world and Iran while putting these re- with sandy and sometimes gravel lenses. The ex- sources at greater risk to contamination (Asghari posed lithological units of the Harzandat plain Moghaddam and Najib 2006; Giridharan et al. range in age from Devonian to Quaternary 2008; Khazaei et al. 2006; Jalali 2007; Tayfur et al. and have different hydrogeological characteris- 2008). In this study, physical, hydrogeological, and tics (Fig. 1). The units of similar hydrogeological hydrochemical data from the groundwater system characteristics are summarized in Table 1 and will be integrated and used to determine the main are qualitatively grouped as impermeable, semi- factors and mechanisms controlling the chemistry permeable, and permeable. of groundwater in the area. The chemical quality In the study area, the Devonian Formations of groundwater is related to both the lithology of and intrusive rocks are impermeable, and the Tri- the area and the residence time of the water in assic formations (limestone, calcareous shale, and contact with rock materials. dolomite) and Eocene Formations (Flysch type sediment, tuff, pyroclastics, and sandstone) are semi-permeable. The red and green gypsiferous Description of the study area marl, green shale, alluvium, and red conglomer- ates are permeable (Aghazadeh and Mogaddam The study area is part of the Aras river drainage 2004). basin and lies between latitudes 38◦35 to 38◦45 N The groundwater of the study area occurs un- and 45◦30 to 45◦45 E (Fig. 1). Harzandat plain der unconfined conditions. The result obtained covers an area of 78.6 km2 (Fig. 1). The area form drilled wells indicates that the thickness of has a cold temperate climate and the air temper- the alluvium aquifer in average is 65 m (Azerbaijan ature is highest in August (24.4◦C) and lowest Regional Water Authority 2004). The maximum in January (−2.6◦C) with an annual average of thickness is about 170 m, which lies in the central 13.2◦C. The climate of the study area is semiarid part of the plain. The general groundwater flow Environ Monit Assess

46 Caspian 45,30 Sea PI Js Hadiy Shahr Re1 38,45 Tehran Re2 Zal I.R.Iran Drd 60 Oryantapeh Mc,s Harzand Re3 Study Area Ea OLv Persian Zonuz Gulf Ec 38,30 Qal Eu Marand

Town 30 Eu Qtr Dad Village Lake Harzand Galingaieh Main Road

Ef 0 4 Km Et,p Shabestar

Ef Tabriz

Eu Urmia Lake

30 Qal Ec LEGEND Emg N Synclinal axis Et,p Eu Fault 45,30 30 38,35 Strike and dip Alluvium(Qal) Pyroclastics(Eu) 45,45

Quat. Travertine(Qtr) Tuff,pyroclastics(Et,p) Village

conglomerate(PI) Andesite(Ea) Shale Plio. Drainage

Jura. Shemshak formation(Js) marl(Emg)

Red conglomerate(Mc,s) - Pale. Eoce. Dolomite and thin limestone Mioc.

Tria. Elika formation(Re1,2,3) Dacit (OLv) Red conglomerate (Ec) Olig. Red sandstone(Es) Andesite dacite(Dad) 0 2 Km Flysch type sediment(Ef) Rhyodacite(Drd)

Fig. 1 Geology and hydrogeology units of the study area direction in the aquifer is from SE to NW (Fig. 2), from the aquifer during the water year 2002– and its depth to water table varies from 6 to 2003 is about five million cubic meters. The mean 46 m below the ground level. Abstraction rate seasonal groundwater levels fluctuations of the

Table 1 Stratigraphic Age Formation Hydrogeologic relations of the geologic properties units in the study area al) showing hydrogeologic Quaternary Alluvium(Q Permeable tr properties Travertine(Q ) Pliocene Poorly consolidate conglomerate(PI) Semipermeable Miocene Red conglomerate(Mc,s) Permeable Oligocene Dacit flows and domes(OLv) Impermeable Eocene Pyroclastics(Eu) Semipermeable Tuff,pyroclastics(Et,p) Semipermeable Andesite(Ea) Impermeable Red and green gypsiferous marl(Emg) Permeable Cretaceous Flysch type sediment(Ku) Semipermeable Jurassic Green shale(Shemshak formation)(Js) Semipermeable Triassic Dolomite and thin limestone(Elika formation)(Re) Semipermeable Devonian Andesite dacite(Dad) Impermeable Rhyodacite(Drd) Impermeable Environ Monit Assess

Fig. 2 Location of N groundwater samples in 38,45 study area

0 5 3 1

0 6 3 1

0 7 3 1 Oryanthapeh

80 13

38,40 Galinghaieh 1410 Harzand 0 142

1 Village 1430

Observation well 1390 Water sample Flow Line

45,30 0 2 Km 45,45 38,35

2−) study area indicates that the maximum and mini- contents. Sulfates (SO4 were estimated using mum water level is in May and September, respec- the colorimetric technique. tively (Aghazadeh 2004).

Results and discussion Materials and methods Groundwater chemistry In order to evaluate the quality of groundwater in study area, groundwater samples were collected The overall groundwater pH and EC values of from 36 shallow and deep wells and springs of the study area are ranging from 6.8 to 8.2 and the area during May 2005. The pH and electrical 990 to 6220 μS/cm, respectively. The large vari- conductivity (EC) were measured using digital ation in EC is mainly attributed to geochemical conductivity meters immediately after sampling. processes prevailing in this region. Total dissolved Water sample collected in the field were ana- solids (TDS) in the study area vary from 653 to lyzed in the laboratory for cations (Ca2+,Mg2+, 4,000 mg/l. The groundwater in the study area + +) − 2− 2− < Na ,K and anions (HCO3 ,CO3 ,SO4 , falls under fresh (TDS 1,000 mg/l) to brackish Cl−) using the standard methods as suggested by (TDS > 1,000 mg/l) types of water (Freeze and the American Public Health Association (APHA Cherry 1979; Hem 1970). The total hardness (as + + 1995). Sodium (Na ) and Potassium (K ) were CaCO3) ranges from 325 to 1,720 mg/l. Cation determined by flame photometer. Total hard- concentrations and ratios can trace water–rock 2+ ness (TH) as CaCO3, Calcium (Ca ), carbon- interaction processes, such as mineral weathering 2−) −) ate (CO3 , bicarbonate (HCO3 , and chloride and cation exchange (Han et al. 2009). In the study (Cl−) were analyzed by volumetric methods. Mag- area, the Na and K concentrations in groundwater nesium (Mg2+) was calculated from TH and Ca2+ range from 66 to 1,127 and 1.17 to 50 mg/l, Environ Monit Assess

Ca HCO3 ering as well as dissolution of carbonic acid in the aquifers (Kumar et al. 2009;Eq.1).

3 2+ −3 CaCO + CO2 + H2O → Ca + 2HCO and Na+K Mg Cl SO4 + −3 CO2 + H2O → H + HCO (1)

Fig. 3 Pie diagram of median values of major ions −) Bicarbonate (HCO3 in the study area ranges from 212 to 1,488 mg/l. The concentration of chloride ranges from 115 to 1,611 mg/l and in- respectively. High concentrations of Na+ in the creases from the recharge to discharge area. Sul- groundwater are attributed to cation exchange fate varies from 125 to 1,248 mg/l. Figure 3 shows among minerals. The concentrations of calcium that Na+ and Cl− are dominant cations and an- range from 54 to 287 mg/l, which is derived from ion, respectively. A further illustration of this is calcium rich minerals like feldspars, pyroxenes, shown in Fig. 3, where the median values of Cl− and amphiboles. The major source of magnesium exceeded 50% of total anions in mille-equivalent (Mg2+) in the groundwater is due to ion exchange unit. The abundance of the major ions in ground- of minerals in rocks and soils by water. The con- water is in following order: Na+>Ca2+>Mg2+>K+ − − 2− 2− centrations of Mg found in the groundwater sam- and Cl >HCO3 >SO4 >CO3 . Minimum, max- ples vary in the range 30–205 mg/l. imum, and average values of physical and chem- The carbonate and bicarbonate concentration ical parameters of groundwater samples are in groundwater is derived from carbonate weath- presented in Table 2.

Table 2 Summary statistics of the analytical data and groundwater samples of the study area exceeding the permissible limits prescribed by WHO for drinking purposes Parameters Units Minimum Maximum Mean SD WHO international standard (1993) Most desirable limits Maximum allowable limits pH – 6.8 8.2 7.52 0.41 7–8.5 9.2 EC μS/cm 990 6,220 3,489 1,843 – – TDS mg/l 653 4,000 2,300 1,372 500 1,500 Na mg/l 66 1,127 471 12.9 – 200 K mg/l 1.17 50 11 0.27 – – Ca mg/l 54 287 161 6.02 75 200 Mg mg/l 30 205 78 3.21 50 150 Cl mg/l 115 1,611 637 12.64 200 600 HCO3 mg/l 212 1,488 479 5.46 – – CO3 mg/l 0 60 10 0.22 – – SO4 mg/l 125 1,248 490 8.06 200 400 TH mg/l 325 1,720 724 413.8 100 500 SAR – 1.2 19.2 7.6 4.37 – – %Na % 28 79 55 12.8 – – RSC meq/l −30.4 4.5 −6.46 7.85 – – PI % 43 82 63.7 11.4 – – CAI,1 meq/l −1.2 0.44 −0.33 0.45 – – CAI,2 meq/l −0.44 0.37 −0.18 0.23 – – SI calcite – −1.08 1.5 0.35 0.59 – – SI dolomite – −0.7 2.95 0.85 0.78 – – SI gypsum – −3.5 −0.32 −1.71 0.67 – – SI anhydrate – −3.27 −0.5 −1.34 0.62 – – EC electrical conductivity, SAR sodium adsorption ratio, CAI chloro-alkaline index, TDS total dissolved solids, RSC residual sodium carbonate, SI saturation index, TH total hardness, PI permeability index, SD standard deviation Environ Monit Assess

Hydrochemical evaluation diagram (Fig. 4a). The data fall below the equiline (1:1), which suggests that an excess of alka- The geochemical variations in the ionic concentra- linity in the water has been balanced by alkalis tions in the groundwater can easily be understood (Na+ + K+), while the sample points lie below when they are plotted along an X–Y coordinate the equiline in a plot of Ca2+ + Mg2+ versus (Guler et al. 2002). Results from the chemical total cation (TCl Fig. 4b). The graph of Ca2+ + analyses were used to identify the geochemical Mg2+ versus TC shows most of the samples far processes and mechanisms in the groundwater below the theoretical line (1:1; Fig. 4b), indicating aquifer system. an increasing contribution of alkalis to the major The chemical data of the groundwater samples ions caused by silicate weathering (Subba Rao 2+ + 2+ − 2− + + + is plotted for Ca Mg vs. HCO3 CO3 2008). In a plot of Na K vs TC (Fig. 6c),

40 (a) 80 (b) 35 70 30 60 25 50 20 40 15 30 Ca+Mg (meq/l) Ca+Mg (meq/l) 10 20 5 10 0 0 0 5 10 15 20 25 30 35 40 01020304050607080 HCO3+CO3 (meq/l) TC(meq/l)

80 (c) 80 (d) 70 70 60 60 50 50 40 40 30 30 Na+K (meq/l) 20 SO4+Cl (meq/l) 20 10 10 0 0 01020304050607080 010203040506070 80 TC (meq/l) Na+K (meq/l)

60 (e) 60 (f) 50 50

40 40

30 30 Na (meq/l) Na(meq/l) 20 20

10 10

0 0 01020304050600 102030405060 Cl(meq/l) Ca (meq/l)

15 (g) 45 (h) 40 10 35 5 30 25 0 20 -5 15

HCO3+SO4(meq/l) 10 -10 5

(Ca+Mg)-(SO4+HCO3) (meq/l) -15 0 -15 -10 -5 0 5 10 15 0 5 10 15 20 25 30 35 40 45 Na- Cl (meq/l) Ca+Mg (meq/l)

Fig. 4 Graphs of different parameters (solid line denotes 1:1) Environ Monit Assess the chemical data of the samples fall below the input in the groundwater system (Cerling et al. equiline and above the Na+ + K+/0.50 TC line. 1989; Fisher and Mullican 1997). The graph of 2+ + 2+ 2− + − This leads to infer that the supply of cations Ca Mg versus SO4 HCO3 (Fig. 4h) via silicate weathering and/or soil salts is more shows that nearly all of samples fall above the 1:1 significant (Stallard and Edmond 1983), whereas ratio line and show a deficiency of Ca2+ + Mg2+ 2− + − + the increase in alkalis with a simultaneous in- relative to SO4 HCO3 . Therefore, Na must − + 2− 2− crease in Cl SO4 (Fig. 4d) reflects a com- balance the excess of negative charge of SO4 − + mon source for these ions from the dissolution and HCO3 ions. Higher concentration of Na of soil salts (Sarin et al. 1989; Datta and Tyagi in the groundwater is an index of ion exchange 1996). The observed excess of Na+ over K+ is process. because of the greater resistance of K+ to chemical weathering and its adsorption on clay minerals (Subba Rao 2008). Chloroalkaline indexes Most of the samples have a Na/Cl ratio around or above 1, indicating that an ion exchange It is essential to know the changes in chemical process is prevalent in the study area (Fig. 4e) composition of groundwater during its travel in (Kumar et al. 2006). The evidence for ion ex- the subsurface (Sastri 1994). The chloro-alkaline change in the development of salinization can lead indexes (CAI) 1, 2 are suggested by Schoeller to release of Na+ from clay products, replacing (1977), which indicate the ion exchange be- Ca2+ that is present in groundwater. Figure 4f tween the groundwater and its host environment. shows the ion exchange reactions, where Na+ is The chloro-alkaline indexes used in the evalua- plotted against Ca2+,inwhichCa2+ levels are tion of base exchange are calculated using the observed between 2.3 and 28 meq/l, while Na+ formulae. levels are found between 2.8 and 54 meq/l. Hence, the ion exchange process appears as responsible 1. Chloro Alkaline Indices 1 + for contributing higher concentration of Na in = C1 − (Na + K) /C1 (2) the groundwater. If the ion exchange is the only controlling process of groundwater composition, 2. Chloro Alkaline Indices 2 2+ + 2+) 2− + the relation between (Ca Mg –(SO4 −) + − − = C1−(Na+K) /(SO +HCO +CO +NO ) HCO3 and Na Cl should show negative 4 3 3 3 linear trend with a slope of unity, considering (3) the participation of cations in the ion exchange reaction (Fisher and Mullican 1997). In Fig. 4g, If there is ion exchange of Na+ and K+ from the samples show a trend of (Ca2+ + Mg2+) – − − water with magnesium and calcium in the rock, (SO 2 + HCO ) versus Na+ − Cl− with a neg- 4 3 the exchange is known as direct when the indices ative slope of less than unity, but they spread are positive. If the exchange is reverse then the above and below the linear trend. This suggests exchange is indirect and the indices are found to that the controlling of groundwater quality de- be negative. The CAI 1, 2 are calculated for the pends not only on the involvement of ion ex- waters of the study area as given in Table 2.From change process but also on the involvement of Eqs. 1 and 2, the 78% of the groundwater sam- other processes. Otherwise, the spreading of samples has negative and 22% positive chloro-alkaline ple points above and below the linear trend should indexes. not be expected. The graph of Ca2+ + Mg2+ versus 2− + − SO4 HCO3 will feature a nearly 1:1 line if dis- solutions of calcite, dolomite, and gypsum are the Hydrochemical facies dominant reactions in the system (Srivastava and Ramanathan 2008). Ion exchange tends to shift The term hydrochemical facies is used to describe 2− + the points right because of the excess of SO4 the bodies of groundwater in an aquifer that differ − HCO3 ions, which may be due to anthropogenic in their chemical composition. The facies are a Environ Monit Assess function of the lithology, solution kinetics, and Saturation index flow patterns of the aquifer (Raju et al. 2009). Large tables of analytical data are usually difficult Saturation indexes are used to evaluate the de- to interpret regarding the variations in water qual- gree of equilibrium between water and miner- ity. Graphs are useful for this purpose and sev- als. Changes in saturation state are useful to eral specialized types are in use. Piper diagram distinguish different stages of hydrochemical evo- is one of them. It provides a convenient method lution and help identify which geochemical reac- to classify and compare water types based on tions are important in controlling water chemistry the ionic composition of different water samples (Coetsiers and Walraevens 2006; Drever 1997; (Chkirbenea et al. 2009).The values obtained from Langmuir 1997). The saturation indexes were de- the groundwater sample analyzing, and their plot termined using the hydrogeochemical equilibrium on the Piper’s diagrams (Piper 1944) reveal that model, PHREEQC for Windows (Parkhurst and the major cation is Na+ and the anion is Cl−.In Appelo 1999). The saturation index of a mineral the study area, the major groundwater types are is obtained from Eq. 4 (Garrels and Mackenzie Na−Cl and mixed Ca, Mg−Cl types, that the al- 1967). kalis (Na+,K+) are significantly dominating over + + SI = log (IAP/Kt) (4) the alkaline earth metals (Ca2 ,Mg2 ; Fig. 5). The sodium-chloride water type in study area is due Where IAP is the ion activity product of the to the low velocity of groundwater, ion exchange, dissociated chemical species in solution, Kt is the long time contacts of water, and formations as well equilibrium solubility product for the chemical as the type of the rocks. involved at the sample temperature. An index

Fig. 5 Chemical facieses of groundwater in Piper Ca+Mg Ca+Mg diagram

50 50

1 4

SO4+Cl SO4+Cl

0 100 0

2 3 Ca+Mg

HCO3+CO3 6 HCO3+CO3 Na+K 50 50 Na+K 50

SO4+Cl

5 7 0 1. Alkaline earths exceed alkalis 2. Alkalis exceed alkaline earths 3. Weak acids > strong acids 9 HCO3+CO3 4. Weak acids < strong acids Na+K 50 5. Carbonate hardness exceeds 50 % 8

6. Non - carbonate hardness exceeds 50 % 7. Non - carbonate alkalie exceeds 50 %

8. Carbonate alkalie exceeds 50 % 100 9. Non one cation anion pair exceeds 50 % Environ Monit Assess

(SI), less than zero, indicate that the groundwater values of SIcal,SIdol,SIgyp,SIanhy are 0.33, 0.85, is undersaturated with respect to that particular −1.16, and −1.33, respectively. mineral. Such a value could reflect the charac- ter of water from a formation with insufficient amount of the mineral for solution or short res- Drinking and irrigation water quality idence time. An index (SI), greater than zero, specifies that the groundwater being supersatu- The analytical results have been evaluated to as- rated with respect to the particular mineral phase certain the suitability of groundwater of the study and, therefore, incapable of dissolving more of the area for drinking and agricultural uses. The drink- mineral. Such an index value reflects groundwa- ing water quality is evaluated by comparing with ter discharging from an aquifer containing ample the specifications of TH and TDS set by the WHO amount of the mineral with sufficient resident (1993). According to WHO (1993) specification time to reach equilibrium. Nonetheless, supersat- TDS up to 500 mg/l is the highest desirable and up uration can also be produced by other factors to 1,500 mg/l is maximum permissible (Table 2). that include incongruent dissolution, common ion Based on this classification, 27% of samples be- effect, evaporation, rapid increase in tempera- long to maximum permissible category, and the ture, and CO2 exsolution (Appelo and Postma remaining samples are exceeding the maximum 1996; Langmuir 1997). In Table 2, the SI for cal- allowable limits. The classification of groundwater cite, dolomite, anhydrate, and gypsum are shown. based on total hardness (Sawyer and McCartly Figure 6 shows the plots of SI against TDS for 1967) shows that all of the groundwater samples all the investigated water. Nearly all water sam- fall in the very hard water category (Table 3). ples were supersaturated with respect to calcite, Maximum allowable limit of TH for drinking is dolomite, and aragonite and all samples under- 500 mg/l and the most desirable limit is 100 mg/l saturated with respect to gypsum and anhydrite, as per the WHO international standard. Based on suggesting that these carbonate mineral phases this classification, it indicates that 73% samples may have influenced the chemical composition of exceed the maximum allowable limits; such water the study area. In Na−Cl water type, the mean (water with TH greater than 80 mg/l) cannot be

Fig. 6 Plots of saturation indexes with respect to some carbonate and sulfate minerals against TDS Environ Monit Assess

Table 3 Classification of Classification scheme Categories Ranges Percent of groundwater based on samples total hardness (TH), < electrical conductivity TH (Sawyer and McCartly 1967) Soft 75 – (EC), chloride Moderately hard 75–150 – concentration, Sodium Hard 150–300 – adsorption ratio (SAR), Very hard >300 100 sodium percent (%Na) EC (Wilcox 1955) Excellent <250 – and residual sodium Good 250–750 – carbonate (RSC) Permissible 750–2250 22 Doubtful 2250–5000 53 Unsuitable >5000 25 Cl− classification (Stuyfzand 1989) Extremely fresh <0.14 – Very fresh 0.14–0.85 – Fresh 0.85–4.23 11 Fresh brackish 4.23–8.46 27 Brackish Brackish- 8.46–28.21 42 Salt 28.21–282.06 20 Salt 282.06–564.13 – Hypersaline >564.13 – SAR (Richards 1954) Excellent <10 83 Good 10–18 11 Doubtful 18–26 6 Unsuitable >26 – Na% (Wilcox 1955) Excellent 0–20 – Good 20–40 5 Permissible 40–60 62 TH total hardness, EC Doubtful 60–80 33 electrical conductivity, Unsuitable >80 – SAR sodium adsorption RSC (Richards 1954) Good <1.25 5 ratio, %Na sodium Medium 1.25–2.5 16 percent, RSC residual > sodium carbonate Bad 2.5 79

used for domestic purposes because it coagulates category, 53% doubtful category, and 25% un- soap lather. suitable category. Stuyfzand (1989) classified wa- The development and maintenance of success- ter on the basis of Cl− ion concentration into ful irrigation projects involve not only the sup- eight divisions as shown in Table 3. Based on this plying of irrigation water to the land but also the classification, 10% of groundwater samples were control of salt and alkali in the soil (Haritash et al. fresh, 27% fresh brackish, 42% and 20% were 2008). Salinity and indexes such as sodium ab- brackish-salt on the basis of Cl− concentration. sorption ratio (SAR), sodium percentage (%Na), SAR is an important parameter for determin- residual sodium carbonate (RSC), and perme- ing the suitability of groundwater for irrigation ability index (PI) are important parameters for because it is a measure of alkali/sodium hazard to determining the suitability of groundwater for crops (Subramani et al. 2005). SAR is defined by agricultural uses (Srinivasa Gowd 2005;Raju Karanth (1987)asEq.5. 2007). Electrical conductivity is a good measure of SAR = Na/ Ca + Mg /2 1/2 (5) salinity hazard to crops as it reflects the TDS in groundwater. The US Salinity Laboratory (1954) classified ground waters on the basis of electrical Where all ionic concentrations are expressed in conductivity (Table 3). Based on this classifica- meq/l. The SAR values range from 1.2 to 19.2. Ac- tion, 22% of samples belong to the permissible cording to the Richards (1954) classification based Environ Monit Assess on SAR values (Table 3), 83% of samples belong designated as class II (25–75%) indicate that the to the excellent category, 11% of them belong to groundwater is unsuitable for irrigation excepting good categoryand the remaining samples belong the two samples, which was classified as class I to the doubtful category. SAR can indicate the (>75%). degree to which irrigation water tends to enter cation-exchange reactions in soil. Sodium replacing adsorbed calcium and magnesium is a hazard Conclusions as it causes damage to the soil structure and be- comes compact and impervious (Raju 2007). The Interpretation of hydrochemical analysis reveals sodium percent (%Na) is obtained by the Eq. 6. that the groundwater in study area is very hard, fresh to brackish and alkaline in nature. The se- %Na = Na + K × 100/ Ca + Mg + Na + K quence of the abundance of the major ions is in the following order: Na+>Ca2+>Mg2+>K+ and (6) − − 2− 2− Cl >HCO3 >SO4 >CO3 . Alkalis slightly exceed alkali earths and strong acids exceed weak Where all ionic concentrations are expressed acids. The compositional relations and mineral in meq/l, according to the Wilcox (1955)clas- saturation states indicate that the dominant con- sification based on %Na values (Table 3), 5% of trol of associated hydrogeochemical processes is samples belong to the good category, 62% of them dissolution of evaporate minerals such as halite belong to permissible category, and the remaining and gypsum, ion exchange and the residence time samples are belong to the doubtful category. of the groundwater in contact with rock materials. RSC has been calculated to determine the haz- In the study area, the dominant hydrochemical ardous effect of carbonate and bicarbonate on the facieses of groundwater is Na−Cl. Ionic concen- quality of water for agricultural purposes and has trations, TDS, EC, and water quality suggest been determined by the Eq. 7. that groundwater residence time is primarily con- RSC = (CO3 + HCO3) − Ca + Mg (7) trolled by the occurrence of different hydrochemical facies. Assessment of water samples according Where all ionic concentrations are expressed in to exceeding the permissible limits prescribed meq/l (Eaton 1950). The classification of irriga- by WHO for drinking purposes indicated that tion water according to the RSC values is wa- groundwater in study area is chemically unsuitable ters containing more than 2.5 meq/l of RSC are for drinking uses. Assessment of water samples not suitable for irrigation, while those having from calculation of chemical indexes like sodium 1.25–2.5 meq/l are doubtful and those with less adsorption ratio, percentage of sodium, residual than 1.25 meq/l are good for irrigation (Table 3). sodium carbonated, and PI indicated that ground- Based on this classification, 5% samples belong water in study area is chemically doubtful to un- to the good category, 16% samples belong to the suitable for irrigation. doubtful category, and 79% belong to unsuitable category. Acknowledgements The authors gratefully acknowledge The PI values also indicate that the groundwa- the Azerbaijan Regional Water Authority for supplying the existing relevant data and also wish to thank M. Oroje ter is unsuitable for irrigation. It is defined as: for the water chemistry analysis. We would like to thank = × + / H. Naseri, A. Alinajhad, M. Najib and A. Zainali for their PI 100 Na HCO3 1 2 kindly help during the field visits and the collection of data. / Na + Ca + Mg (8)

Where all the ions are expressed in meq/l References (Ragunath 1987). WHO (1989) uses a criterion for assessing the suitability of water for irrigation Aghazadeh, N. (2004). Hydrogeological consideration of the Harzandat plain aquifer and preparing of its math- based on permeability index. According to PI val- ematical model (in Persian). Iran: M.S. Thesis, Univer- ues, the groundwater of in the study area can be sity of Tabrze. Environ Monit Assess

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