Springs are natural outlets through which groundwater emerges at the ground surface as concentrated discharge from an aquifer are one of the most conspicuous forms of natural return of groundwater to the surface [1]. Conditions necessary to produce springs are many and are related to different combinations of geologic, hydrologic, hydraulic, pedological, climatic and even biologic controls [2]. Springs while flowing downhill from their origins, have formed their own narrow riparian zones on either side of their flow-paths. These riparian zones usually have heavy vegetation growth. Undoubtedly, these plant growths and the seeping spring waters augment the groundwater recharge of the blower aquifers to support the life of the existing springs issuing from these aquifers. Freshwater from the spring could be directly discharged onto the ground surface, directly into the beds of rivers or streams or into the ocean below sea level. Springs are used both for drinking and irrigation purposes by the local inhabitants both at higher elevations and in foothill zones (Figure 1). Spring water was associated in the public mind with exceptional quality and even considered holy in some places. Bottling of spring water has become a blooming business across the world [3]. Apart from tapping springs for drinking/irrigation purposes, they also sustain thousands of other life forms vital to a balanced ecosystem [1]. The importance of springs have gone beyond just being sources of domestic and municipal water supply but also sources for foreign exchange earnings as they serve as places for tourist attraction and industrial establishment where safe drinking water could be bottled [4]. Water chemistry to a large extent, is influenced by elemental distribution often determined by the lithologic effects, climate, groundwater flow and anthropogenic activities [5,6].

Figure 1: Map of Ekiti State showing the study area-Effon.

The sources of water for any specific purpose are not as important as the suitability of the water for the desired purpose as the exposed springs can be contaminated through anthropogenic activities. With increasing human population, industrialization, urbanization and the consequent increase in demand for water for domestic and industrial uses, the increase in the implication of polluted water on man and the environment have been on the increase and have been severally studied [7,8]. Assessment of Effon Psammite spring water is therefore necessary as increased knowledge of processes that controls chemical compositions of the spring water can improve the understanding of its usability status apart from guide against outbreak of water borne diseases. This study is therefore aimed at evaluating the quality characteristics as well as examining the possible use of Effon Psammite ridge spring as a potable source of water (Figure 2).

Figure 2: Geologic Map of Ekiti-State, Nigeria.

The study area (Ekiti Basement Complex Area) is within the Precambrian-Lower Proterozoic Basement Complex terrain of southwestern Nigeria [9,10]. It is located on coordinates: Latitudes 7°38.678’N and 7°49.914’N, Longitudes 4°54.658’E and 4°57.478’E. Highest elevation is about 523 m above mean sea level. Effon Psammite is an extensive quartzite ridge that cut across Ido, Ajinare, Ita-Ido, Itawure, and Effon Alaaye.

The principal rock units in the area include Precambrian migmatitegneiss- schist complex constituting over 60% of the sampling localities into which other rocks intruded during the Pan-African orogeny. Among the rocks that intruded into the migmatite-gneiss-schist complex were the charnockite, fine grained granite and porphyritic granite. All the rocks which have previously been described as Younger metasediments belong in this group e.g., Effon Psammite Formation [9]. The Effon Psammite Formation is a belt of quartzites, quartze schists and granulities which occurs largely east of Ilesha and runs for nearly 180 km in general NNE-SSW direction. The topography of the area is the undulating type, dotted with different outcrops in several places. Most of the rocks in the area are well exposed and are as high as 250 m above sea level and there is prevalence of erosion gullies along hill slopes and valleys.

The drainage system over the area consisting of the basement rocks are usually marked with the proliferation of many smaller river channels. The channels of these smaller streams are dry for many months especially from November to May. There is a major river in the study area called River Oyi and Owawa in Aiyegunle village. The drainage pattern in the south-eastern part of the area where topography is dominated by series of ridges is the trellis type which suggests that the drainage here is structurally controlled whereas, the drainage pattern in other parts of the study area is dendritic, due to homogeneity of the rocks and absence of structures. The Effon Psammite is a NNE-SSW trending ridge highly foliated, jointed, schistose ridge often showing interesting sedimentary structures. The intense deformation structures of these rocks permit adequate aquifer properties needed to generate the springs. Consequently, the quartzite belt stretching NNE-SSW is considered as good aquifer. The surrounding schistose units occur as low yielding aquicludes. Ekiti State has so many springs, amongst which are: Ikogosi warm spring in Ikogosi-Ekiti, Arinta spring in Ipole-Ekiti and Arioye and Afeni springs in Efon-Alaye-Ekiti. The springs have history of continuous supply of water throughout the year and are therefore targeted for hydrochemical assessment since they are used for domestic purposes especially during dry season when most surface water and shallow wells might have dried off.

Fifteen (15) water samples were collected in thoroughly cleaned polyethylene bottles of 1.5 liter capacity. Prior to collection, the bottles were washed with distilled water and subsequently rinsed thoroughly with the sample water. The samples were collected up to top without leaving any space so as to prevent premature release of dissolved gases during the transit period. The samples were preserved with few drops of Nitric acid (HNO₃). After sampling, the lids of the containers were immediately replaced to minimize contamination and escape of gases. The samples were then stored in a cooler and transported to the laboratory for analysis. All analysis was carried out at a standardized laboratory using International regulatory methods. The evaluation of water quality was in accordance with regulatory standard. The approach ensures that the samples collected were tested in accordance with agreed requirements using competent personnel as well as appropriate equipment and materials.

Field Parameters such as pH, Electrical conductivity and temperature were determined on the field due to their unstable nature. These were carried out using Multi-parameter TestrTm 35 series. Cation concentrations were measured by the Buck Scientific Model 210 VGP Atomic Absorption Spectrophotometer (AAS) while the anions were analyzed using colrimetric method. The software SPSS version 17.0 was used for statistical analyses. Graphical plots (Piper and Schoeler diagrams) were employed to unravel the hydrochemical characteristics and evolution of the spring water.

Except for pH values that is mildly acidic in some locations, all the cations, anions and electrical conductivity are below the WHO (2004) recommended standards for drinking water. The water is slightly acidic to slightly alkaline and could be classified as fresh water [11,12]. These characteristics make the water suitable for both domestic and industrial usage.

The cations range as follows: Ca²⁺ (1.6 – 16.0), Mg²⁺ (0- 7.53), Na⁺ (5.58 – 13.32), K⁺ (0.19-20.9), while the anions are as follows: HCO₃^- (10.0-79.0), Cl^- (5.0 – 24.0), PO₃^- (3.7 – 14.95), SO₄^2- (4.0 – 9.2), NO₃^- (0.12 – 9.27) (Table 1). The mean concentration of the cations is in the order Na⁺ > Ca²⁺ > K⁺ > Mg²⁺ while for anions, HCO^3-> Cl^- > PO³ - > SO₄^2- > NO^3-. 47% of the water are alkali water predominantly SO₄^2- - Cl^-, 20% are alkali water predominantly HCO₃^-, 27% are earthalkaline water predominantly SO₄^2- while 7% are earth alkaline water predominantly HCO₃ ^-, and SO₄^2-. Table 2 is the descriptive statistical summary of the analytical data.

Table 1: Results of Water Quality Analysis in Effon Psammite Ridge Spring.

Table 2: Descriptive Statistical Summary of the Analytical Data.

The water is mildly acidic to alkaline due to dissociation of bicarbonate and the following water types: Na-SO₄-Cl, Na-HCO₃, Ca- Na-SO₄ and Ca-Mg-HCO₃-SO₄ which is a reflection of geology and climate of the study area. The mildly acidic to alkaline indices revealed that the springs water has undergone ion exchange between Na + K ions in the water with Ca and Mg of soil during the residence time of the water. Generally, the low values of the conductivity are mainly attributed to geochemical processes prevailing in the area. The springs are being recharged from recent precipitation that has low water-rock interactions and low residence time within the aquiferous zones. The hydrochemical trend signifies low mineralized water with low water rock interactions and residence time. Based on these water types and the presence of Na⁺, concentration of cations is geogenic in origin and might have come from the interaction of water and the rock or introduced from weathering of rocks into the spring water.

Water chemistry and types

The result of chemical analysis was used to classify the water types present in the Effon Psammite Springs of the study area. Based on the predominance of both cations and anions, a plot on the Piper’s Trilinear diagram was made. Trilinear plotting systems developed by Piper [13] were used in the study of the water chemistry and quality. Piper diagrams are a combination of cation and anion triangles that lie on a common baseline. A diamond shape between them is used to replot the analyses as circles whose areas are proportional to their TDS [14-20]. The position of an analysis that is plotted on a piper diagram can be used to make a tentative conclusion as to the origin of the water represented by the analysis. The diamond part of a piper diagram may be used to characterize different water types. Generally, groundwater can be divided into four basic types according to their placement near the four corners of the diamond. Water that plots at the top of the diamond is high in ca²⁺ + Mg²⁺ and Cl^-+ SO₄²⁺, which results in an area of permanent hardness. Water that plots near the left corner is rich in ca²⁺ + Mg²⁺ and HCO₃^- and is the region of water of temporary hardness [20-26]. Water plotted at the lower corner of the diamond is primarily composed of alkali carbonates (Na⁺+ K⁺ and HCO₃-+CO₃^2-). Water lying near the right-hand side of the diamond may be considered saline (Na⁺ + K⁺ and Cl^- + SO₄²⁺). The water types in the study area were thus designated according to the area in which they occur on the diagram segments (Figure 3). These diagrams reveal the analogies, dissimilarities and different types of waters in the study area, which are shown in Figures 3 and 4. From the interpretation of this plot, several water types were delineated [27-33]. The water types are Na-SO₄-Cl, Na-HCO₃, Ca-Na-SO₄, Ca-Mg-HCO₃-SO₄. Based on these water types and the presence of Na⁺, concentration of cations is geogenic in origin and might have come from the interaction of water and the rock or introduced from weathering of rocks into the groundwater. Piper Trilinear and Durov diagrams (Figure 3 and 4 shows the water types while (Figure 5) is the Stiff diagram showing chemical ions of Effon Spring Water) [34,35].

Figure 3: Piper Trilinear Diagrams for Spring Water Samples.

Figure 4: Durov Diagram of the Effon Psammite Spring Water.

Results also show that strong correlation exist between Na⁺ and EC (r=0.793), K⁺ and EC (r=0.905), TH and Mg²⁺ (r=0.901), Na⁺ and K⁺ (r=0.857), K⁺ and NO₃^- (r=0.909), Ca²⁺ and Mg²⁺ (r=0.632), Ca²⁺ and NO₃^- (r=0.6580). Weaker correlations were obtained between Ca²⁺ and EC (r=0.589), Mg²⁺ and EC (r=0.561), K⁺ and Suspended solids (r=0.563) (Table 3) [36].

Table 3: Correlation analysis results for the samples.

This investigation has revealed that except for pH values that are mildly acidic to slightly alkaline in some locations, the physico- chemical characteristics of the spring waters are below the WHO recommended standards for drinking water. The low values of the conductivity are mainly attributed to geochemical processes prevailing in the area. These characteristics make the water suitable for both domestic and industrial usage. The mean concentrations of the cations follow the order: Na⁺ >Ca²⁺ >K⁺ >Mg²⁺ while for anions, HCO₃^- >Cl^- >PO₃^- >SO₄^2- >NO₃^-. The water is mildly acidic to alkaline due to dissociation of bicarbonate with the following water types: Na-SO₄^-Cl, Na-HCO³, Ca-Na-SO₄ and Ca^- Mg-HCO₃-SO₄ which are a reflection of geology and climate of the area.

The mildly acidic to alkaline indices revealed that the spring water has undergone ion exchange between Na + K ions in the water with Ca and Mg of soil during the residence time of the water. The springs are being recharged from recent precipitation that has low water-rock interactions and low residence time within the aquiferous zones. The hydrochemical trend signifies low mineralized water with low waterrock interactions and residence time. Based on these water types and the presence of Na⁺, the concentrations of cations are geogenic in origin and might have come from the interaction of water and the rock or introduced from weathering of rocks into the spring water.

It is recommended that effective development of springs should involve thorough examination of their seasonal discharges, including during the summer. In case water supply exceeds use, the surplus waters may be stored for future use in horticulture and to irrigate crop land. Since springs are yet to receive substantial attention, care must be taken to protect the spring from contamination.