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International Journal of Agriculture and Crop Sciences. Available online at www.ijagcs.com IJACS/2013/5-17/1983-1992 ISSN 2227-670X ©2013 IJACS Journal

Effects of geological formation on groundwater quality in Lordegan Region, Chahar-mahal- vaBakhtiyari, Iran Yaser Ostovari*1, Shahram Zare2,Habib Beigi Harchegani 3,Kamran Asgari4 1,3,4. Department of Soil Science, Shahrekord University, (Iran) 2. Department of Irrigation Science, Shiraz University, (Iran) *Corresponding author email: [email protected] ABSTRACT: To study the contamination of groundwater, 32 water samples were collected in an area of 60 km2 and analyzed for major cations and anions. Most of the locations are contaminated by higher concentration of EC, TDS, K and NO3. Major hydro chemical facies were identified using Piper trilinear diagram and Stiff diagram.Na+, Ca2+, HCO3-, Cl- and SO42-dominate the chemical compositions of the groundwater, which have been derived largely from natural chemical weathering of carbonate, gypsum, and anthropogenic activities of fertilizer’s source. In most of water samples, magnesium and bicarbonate were dominant cations and anions, respectively. The water was classified as magnesium-chloride. Considering that the ratio of Mg / (Ca + Mg) was often less than 0.5 in water samples. Therefore, the source of magnesium is dolomite weathering. The major anthropogenic components in the groundwater including Na+, Cl-, SO42- and NO3-, and NO3- being the maincontributors to groundwater pollution in Lordegan area. Key words: Anthropogenic –Groundwater Quality Management - Minerals and Anthropogenic Sources. INTRODUCTION Groundwater is a vital natural resource. Depending on its usage and consumption it can be a renewable or a non renewable resource. It is estimated that approximately one third of the world’s population use groundwater for drinking .Increasing pressure on irrigation water resource makes critical status for groundwater. Agriculture has direct and indirect effects on groundwater chemistry (Bohlke, 2002). About 70% of freshwater resources were used in agricultural purposes. The quality of groundwater in rural areas is sensitive to the contaminants originated from the agricultural chemicals (Chae et al. 2004). The chemical composition of groundwater is controlled by many factors that include composition of precipitation, geological structure and mineralogy of the watersheds and aquifers, and geological processes within the aquifer (Andre et al. 2005). The interaction of all factors leads to various water types. Increased knowledge of geochemical evolution of groundwaterin arid and semi-arid regions could lead to improved understanding of hydrochemical systems in such areas, leading to sustainable development of water resources and effective management of groundwater resource. In Iran, little information is known about the natural phenomena that govern the chemical composition of groundwater or anthropogenic factors (Andre et al. 2005). Increasing knowledge of geochemical processes that control groundwater chemical composition in arid and semi-arid regions could lead to improved understanding of hydrochemical systems in such areas. Understanding relations can improve management and utilization of the groundwater resource by clarifying relations among groundwater quality, aquifer lithology, and recharge type. Groundwater is the primary source of water for human consumption, as well as for agriculture and industrial uses (Jalali, 2009). The aims of this study were to characterize water-rock interaction and its effects on the chemistry of the groundwater and determine the influence of human activities on the hydrogeochemistry of groundwater in Lordegan, Chahar-mahal- vaBakhtiyari, Iran.

Intl J Agri Crop Sci. Vol., 5 (17), 1983-1992, 2013 MATERIALS AND METHODS Study Area Lordegan plain is located between 47050' and 51010' longitudes and 310 18' and 310 37' latitudes with 60 2 Km area in Charmahal-va-Bakhtiari province, Iran (Fig.1). The rainy season extends from October to May, with a maximum during November and February.

Figure1. position of Lordegan plain in Iran

The monthly average of temperatures varying between -1 and 23.45°C and the mean annual value being 15.5 . Soils are generally sandy to clay in texture and mostly classified as Inceptisoil and calcareous. Mineralogically, most of the soils are dominated by illite, smectite, chlorite and vermiculite, typical for most arid andsemi-arid soils. °C

Geology of aquifer Lordegan plain in view of geomorphology is surrounded with Zagros mountain range. Additional to Asmary construction, small portion of Rig anticline of Jahrom construction including lime stones and light gray and massive dolomite stones also compose this plain. Kalar andRig Mountain is located in east and northeast of plain which are composed of Asmary construction. This two mountain that dominantly are composed of carbonate construction that play important role in supply the Lordegan plain aquifer. In west of plain Gorazabad mountain is also located that composed of Bakhtiari construction including Conglomerate and sand stones. In northwest of plain Gachsaran construction is located including red and gray marls along with gypsum. This plain is also composed of quaternary young alluvial constructions. Water samples During summer 2011, thirty groundwater samples were collected from Chahar-mahal- vaBakhtiyari, Iran (Fig.1). Samples were analyzed inthe laboratory for the major water quality parameters employing standard method (APHA, 1998). The pH and electrical conductivity (EC) were measured using pH and electrical conductivity meters, respectively. Calcium and magnesium (titration using standard EDTA), Chloride (by standard AgNO3 titration), 2Carbonate and bicarbonate (by titration with H2SO4 ), Sodium and potassium (by flame photometry), and Sulphate and nitrate (by spectrophotometer) were measured (Rowell, 1994). Total dissolved solids (TDS) was measured by evaporate the 100 ml water and weighting the residual.

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Intl J Agri Crop Sci. Vol., 5 (17), 1983-1992, 2013 RESULTS AND DISCUSSION Groundwater chemistry Minimum EC of this aquifer is more than 250 µS/cm (Table.1) which show that water is located in C2 and -1 C3classes)Wilcox,1955(. The mean of TDS in this aquifer is 271 mg L . In some parts of aquifer, the value of TDS -1 is little more than 500 mg L that have intermediate risk for emitter clogging (Nakayama and Bucks, 1979). Table 1.

-1

Summary statistics of chemical compositions of major ions (mg l ) in the groundwater’s of Lordegan area

Variable

unit

Min

Max

Mean

Ec TDS pH NO3SO42HCO3ClCa2+ Mg2+ K+ Na+

S/cmµ mg/L ― mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L

450 271 7.4 6.2 28.5 114.0 39.7 14.8 19.2 0.7 8.5

960 536 7.8 16.1 131.2 235.2 68.8 46.0 48.8 3.4 17.9

692 385 7.6 10.0 85.3 165.8 115.3 26.7 33.6 1.5 12.3

Standard deviation 121 61 0.13 2.0 50.1 31.1 20.4 8.1 8.5 0.8 2.8

Coefficient of variation 18 16 2 19.9 58.7 18.7 29.7 30.1 25.4 51.0 22.7

pH and alkalinity of water have usually very close and have direct relation with each other. In addition, waters with pH range from 7 to 8.5 usually have medium to high alkalinity (Scoot, 2000). pH value in Lordegan plain aquifer is always alkali ranged from 7.40 to 8. Consequently, the alkalinity of Lordegan plain ground water is variable from medium to very high. Measured major cations (Mg2+ and Ca2+) in the experiment were 46 and 36% of all the cations, respectively.Furthermore, Sodium ions are secondary in importance, was about 17% of all cations but Potassium ions are almost absent (average 1.0% of all the cations) (Table.1). Average amount of major anions (HCO3– and Cl–) in the collected samples were about 44.3 and 30% of all the anions, respectively (Table.1). Additionally, SO42– ions is secondary in importance (22.3%). Nitrate concentrations in the collected samples varied from 6.2 to 16.1 with the average of 10.0 mg L-1. In comparison with the maximum permitted level of NO 3- for drinking water mentioned in WHO’s drinking water guideline (50 mg L-1 ), measured amount of nitrate in samples had lower concentration than standard.

Figure 2. Water type classification in Lordegan area

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Figure 3. Relationship among anions and cations in the groundwater of Lordegan area

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Hydrochemical facies Based on cations and anions, samples water classified in 3 types (CaMgHCO3, CaCl2 and CaHCO3). CaMgHCO3, CaCl2, and CaHCO3 water types were 45, 25 and 30% of the total number of water samples. The CaMgHCO3 type water is dominated in the most part of studied area (Figure 2). The origin of solutes -Water/rock interaction Complex relations between dissolved species can reveal the origin of solutes and the process that generated the observed water compositions. Calcium and Magnesium showed strong positive correlation (r = 0.83) which indicating a same geological formation (Figure 3a). 2+ Ca and HCO3 has not any relation and significant correlation (p>0.05), which indicates that calcite may 2+ not be the source of Ca . It could be expected that a great part of HCO3 originated from dissolution of carbonate rocks in the aquifer through the process of percolating waters enriched with CO 2 after being in contact with the atmosphere (Appelo and Postma, 1996). Dissolution of carbonate releases Ca2+ into solution made Ca–HCO3 water type as a final product.Evaluation of the slops of Ca2+, Mg2+ and Na+ with HCO3- gives valuable information about the stone chimetry of the process (Edmunds et al. 1987). The most common weathering reaction for calcite 2+ is simple dissolution (Drever, 1997), giving a ½ Ca : HCO3 equivalence ratio of 1:1: 2+ CaCO3 + H2CO3 → Ca + 2HCO3 (1) There is significant correlation between Na+ and HCO3- (Fig.3b). All of the water samples of Lordegan area have [Ca2++ Mg2+/HCO3-] equivalent ratios larger than unity, indicating that other anions must be exist and balance the excess of Ca2++ Mg2+ over HCO3-. Calcium and SO42- ions in groundwater are mostly provided by the dissolution of gypsum. A correlation between Ca2+ and SO42- (r = 0.83) shows that most of the groundwater effected by Gachsaran formation (Fig.3c). Correlation between SO42- and Mg2+ (r = 0.80) (Fig. 3d) might be because of a part of the SO42- and Mg2+that be derived by the weathering of an Mg2+ sulphate mineral. High SO42- levels, in combination with high Ca2+ and Mg2+ concentrations, have been explained by weathering of reduced pyrite (Dalai et al. 2002). In general, high concentration of SO42- may be derived either by sulphide or by SO42 weathering (Drever, 1997). Thus, gypsum dissolution and pyrite weathering may both 2contribute to the SO4 load of the groundwater. If Ca2+, Mg2+, SO42- and HCO3- are derived from simple dissolution of calcite, dolomite and gypsum, then a charge balance should exist between the cations and the anions. As indicated in the Fig.3e, a deficiency of (HCO3- + SO42-) relative to (Ca2+ + Mg2+) exists in most of the groundwater samples. Therefore, Cl-, the only other major anion, must balance the excess positive charge of Ca2+ and Mg2+. Figure 4 illustrate relation between Mg2+/Ca2+ and Na+/Ca2+ molar ratios for groundwater (r = 0.61). 2+ Mg /Ca2+ ratios vary from 1.4 to 3.1, while Na+/Ca2+ ratio vary from 0.21 to 1.08. These relations show that most 2+ 2+ well waters are below the Mg /Ca = 3.0 line (Figure4).

Figure 4. Plot of Mg2+/Ca2+ versus Na+/Ca2+ for the ground waters of the Lordegan area

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Intl J Agri Crop Sci. Vol., 5 (17), 1983-1992, 2013 This could probably due to equilibration of ground waters simultaneously with calcite and dolomite (Han and Liu, 2004). The water equilibrated together with calcite and dolomite under room temperature gives an ideal molar Mg2+/Ca2+ ratio about 0.8 (Appelo and Postma, 1996).This is supported by generally positive saturation indices for calcite and dolomite in 30% of water samples. In addition to the combined dissolution of calcite, 2+ dolomite,gypsum and anorthite, weathering of sulphide minerals may also control concentration of observed Ca 2+ and Mg . The Na+–Cl- relationship has often been used to identify the mechanisms for acquiring salinity and saline intrusions in semi-arid regions (Sami, 1992). The high Na+ and Cl - contents detected in certain samples may becauseof dissolution of chloride salts. The dissolution of halite in water release equal concentrations of Na+ and Cl into the solution: + NaCl → Na + Cl (2) A parallel enrichment in both ions indicates dissolution of chloride salts or concentration processes by evaporation. Figure 5a shows the value of Cl- as a function of Na+ in the groundwater samples and there is a strong correlation (r = 0.63) between them. However, some analytical data in Fig. 5 deviate from the expected 1:1relation, + indicating that some part of the Na wasderived from other processes. There is a positive correlation (r = 0.32) + 2between Na and SO4 (Figure 5b) which indicating that the excess of sodium in these samples mostly resulted from dissolution of sodium sulphate minerals.

Figure 5. Plots of Na+ versus Cl- and SO4 2- in the groundwater of the Lordegan area

Na+ released from silicate weathering reactions typically interprets a Na+ /Cl- molar ratio greater than one (Meybeck, 1987). The cation exchange between Ca2+ or Mg2+ and Na+ may also explain the excess concentration of Na+ (Stimson et al. 2001). Samples with value of Na+/Cl- ratio greater than one also show a deficit in Ca2+ + 2+ 2+ + Mg , and this is consistent with a Ca –Na cation exchange process which leads to a softening of the water (Hidalgo and Cruz-Sanjulian, 2001). Calcium and Mg2+ can exchange Na+ on the exchangeable sites of the clay 2+ 2+ + minerals that decrease Ca and Mg and increase Na in groundwater. Industrial and/or agricultural + contamination is also responsible for the increase of Na in groundwater. Antropogenic inputs Chemical composition of groundwater is generally controlled by water/rock interaction and human activities. Variation in TDS in groundwater may be related to land use and pollution (Gillardet et al. 1999). It is well known that NO3-,SO42-, Na+ and Cl- ions are mostly derived from agricultural fertilizers, animal waste, and municipal and industrial sewage. These factors can be related to the TDS variation and can be used to indicate the influence of human activities on the water chemistry (Han and Liu ,2004). Figure 6 illustrate relations between various anions and cations with TDS. There were correlation between TDS and Mg2+ (r = 0.55), Na+ (r = 0.35), Ca2+ (r = 0.50), Cl- (r = 0.69), SO42- (r = 0.52) and NO3- (r = 0.76). TDS + values increase with increasing (NO3 +Cl )/Na molar ratios in groundwater (Fig. 7a). A positive relationship (r = 0.71) between TDS values and (NO3 + Cl )/HCO3- molar ratios exist (Fig. 7b).

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Intl J Agri Crop Sci. Vol., 5 (17), 1983-1992, 2013 Nitrate is an important pollutant in the environment, being generally derived from agricultural fertilizers, + atmospheric input, human and animal excreta and bio-combustion, and also from nitrification of organic N and NH4 2+ (Jeong, 2001; Xiao and Liu, 2002). There is a positive correlation between Ca and NO3 (0.54) (Fig. 8a).

Figure 6. Relationship among TDS and anions/cations in groundwater of Lordegan area

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Figure 7 . Plots showing variations of TDS versus a (NO3- + Cl-)/HCO3- and b (NO3- + Cl-)/Na+ for groundwaters

The inverse trend (r = 0.35) between pH and SO42- (Fig. 8b) suggests that part of SO42- could be the product of biochemical reactions (Gallardo and Tase, 2006). In general, NO3- concentrations presented a similar distribution as SO42- (Fig. 8c), and there was a positive correlation (r = 0.56) between them. Both ions would be introduced with the urea and ammonium-sulphate applied during fertilization of the croplands. These two ions are not adsorbed to the negatively charged sites on soil clay minerals and would rapidly migrate downward to the groundwater. Gallardo and Tase (2006) studied hydrogeology and geochemical characterization of groundwater in a typical small-scale agricultural area of Japan. They found a strong positive correlation (r = 0.75) between NO 3and SO42- and it attributed to the applied fertilizers. CONCLUSIONS This study adds to our understanding of the impact of agriculture on major groundwater resources. Both natural geochemical processes and anthropogenic activities control chemical properties of groundwater in Lordegan region. In addition to ion exchange, the industrial or agricultural impact of Na+ also contributes to the increase in Na+ concentration. The substantial amounts of NO3- and SO42- detected in groundwater are a consequence of fertilizer application and its mobilization into the saturated zone. Regular application of N fertilizers in irrigated cropped land is likely to create a blanket source of NO 3-.Downward migration of this may be facilitated by flood irrigation and large rain events, leading to NO3- contamination of groundwater. Some measures should be taken in advance to prevent spreading of the pollution. The Lordegan region is the agricultural area. The farmer surveys indicate that excessive N application often up to 2–3 timesthan the recommended rate is very common in vegetables crops (Jalali, 2009). In addition, municipal and industrial wastewaters are not properly treated before discharged, which easily contaminated the groundwater. Therefore, large amount of N fertilizer and an inadequate management of N fertilization in addition to low irrigation efficiency are mainly responsible for the NO 3-concentrations in groundwater (Jalali, 2009).Some measurements should be taken in advance to prevent spreading of the pollution. Gallardo and Tase (2006) stated that local authorities could carry out a permanent advisory campaign to promote good agricultural practices by collaborating with the farmers. Farmers might be encouraged to plant crops that can accumulate sizeable amounts of nutrients, while replacing or minimizing the use of highly leachable fertilizers (Gallardo and Tase, 2006).

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Figure 8. Relationship between a Ca2+ and NO3-, b SO42- and pH, and c SO42- and NO3- in groundwater of lordegan area

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