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Advances in Applied Science Research, 2015, 6(6):36-46

ISSN: 0976-8610 CODEN (USA): AASRFC

Compositional evaluation and quality status of surface waters of MBAT- ABIATI and Oberekkai Creeks of the , Southeastern

Bassey Edem Ephraim* and Ifedayo Olumide Ajayi

Department of Geology, University of , Calabar ______

ABSTRACT

Water samples collected from Mbat-Abbiati and Oberekkai Creeks of the Great Kwa River were subjected to analysis for chemical characteristics, in an effort to determine the suitability of the waters for drinking, irrigation and other purposes. Investigation of the physicochemical properties show that the water displays favorable conditions of temperature, and exhibits low values of total dissolved solids (TDS), electrical conductivity (EC) and salinity, and these boosts the suitability of the surface waters for various purposes. The reduced BOD contents accounts for increased Dissolved Oxygen available for the survival of aquatic organisms in the Creeks. Additionally, the observed slight acidic character of the water appear critical as it is considerably harsh for the sustenance of fauna and flora, and favours dissolution of trace elements which are non-biodegradable and hazardous. Apart from Mg, Fe and Mn, the concentration of most of the studied chemical species in the investigated waters are below the respective permissible limits of the Standard Organization of Nigeria, World Health Organization and Food and Agriculture Organization of Nigeria. Thus, the water is suitable for drinking, irrigation and crop production since both Creeks appear free from any significant pollution or contamination threat regarding - 2 3 - 2+ 2+ + + HCO 3 , SO 4 , PO 4 , Cl , Ca , Mg , Na , K , Cu, Zn and Cr. However, despite the fact that sodium percent (Na %) and alkalinity or sodium hazard (SAR) underlines the suitability of the waters for irrigation purposes, some level of caution must be exercised with respect to Mg, Mn, and Fe contents of the Creek waters before the water can be considered for agricultural purposes. Besides, the accumulation of Mn in the waters is a cause for concern for marine life as it could lead to manganese toxicity in biota. It appears mining/rock quarrying, agricultural and other anthropogenic activities, as well as lithology are responsible for the sourcing of the various major ions, heavy metal, among other chemical character of the surface waters of Mbat-Abbiati and Oberekkai Creek. ______

INTRODUCTION

The Great Kwa River belongs to the System, which comprises major tributaries, notably, the , Akpayafe River and Mbo River. These tributaries drain through the tropical rain forest belt, consisting of thick rain forest to the North, and freshwater/mangrove swamps to the south. The Great Kwa River originates from the western and northwestern highlands of , extends into the Cameroon highlands, and empties into the southeastern corner of the Atlantic Ocean through the Cross River Estuary [1]. Major Creeks are formed as the river and its tributaries drain and sculpture their routes through the freshwater and mangrove terrain of the south. Two of such Creeks includes Mbat-Abbiati and Oberekkai Creeks. These Creeks are located in present-day Akamkpa Local Government Area of , Nigeria. Concerns have risen about solute pollution, heavy metal contamination and the potential impact on food systems and human health associated with these Creeks [2]. This is because runoffs containing agrochemicals from agricultural fields in Mbat-Abbiati and Oberekkai Villages and environs enter the river through these Creeks. Also, Mbat-Abbiati and Oberekkai Creeks are well positioned to receive effluents from the quarrying and mining activities located within the neighbourhood. Besides, increased rate of urbanization, industrialization and other forms of modernization have continued to plague the productive capacities of coastal water bodies such as the Great Kwa River.

36 Pelagia Research Library Bassey Edem Ephraim and Ifedayo Olumide Ajayi Adv. Appl. Sci. Res., 2015, 6(6):36-46 ______

In view of the fact that much of the populace in the catchment area of the river depends on surface waters to meet their water needs, it becomes necessary to determine the suitability of the water of the Great Kwa River and its tributaries for drinking, irrigation and other purposes. Accordingly, the waters of Mbat-Abbiati and Oberekkai Creeks are studied to determine its suitability for drinking, irrigation and for other usage. The standards for the assessments of the drinking water qualities of the waters are derived from the Nigerian Standard for Drinking Water Quality [3], the World Health Organization guideline for drinking water [4] and the Food and Agriculture Organization (FAO) water quality guidelines for agriculture, surface irrigation and drainage [5].

GEOLOGICAL BACKGROUND The study area is an integral part of the Calabar Flank, which is unique in many respects. Geologically, the Calabar Flank is that part of the Southern Nigerian Sedimentary basin that is bounded by the Oban Massif to the North, Abakaliki-Benue trough to the Northwest, Niger Delta to the South, and Cameroon Volcanic ridge to the Northeast [6, 7] (Fig. 1). In terms of lithology, the Calabar Flank is underlain by Cretaceous Sedimentary rock deposits comprising sandstones, limestones, marlstones and shales (Fig. 2). The Mfamosing Limestone Formation, which constitute the main carbonate – bearing deposit occurring within the area, is about 50m thick at outcrop (type section) and 450m thick in the subsurface on the Ituk high [8]. This limestone-bearing Formation is overlain by a thick sequence of black to grey shale unit, called Ekenkpon Formation [9]. This shale Formation is also characterized by minor intercalation of marls, calcareous mudstone and oyster beds. The Ekenkpon shales are overlain by a thick marl unit, the New Netim Marl [9]. This unit is nodular and shaly at the base and is interbedded with thin layer of shales in up-section. The New Netim Marl is unconformably overlain by carbonaceous dark grey shales, the Nkporo Formation [10]. The Nkporo shales cap the Cretaceous sequence in the Calabar flank as its sequence is overlain by pebbly sandstone unit of the Tertiary Benin Formation.

MATERIALS AND METHODS

Study Area The hydrographic areas of the two Creeks are located within the plains of Mbat-Abbiati and Oberekkai in present- day Akamkpa Local Government Area of Cross River State, Nigeria and are delimited by Latitude 5°05’N and 5°06’N and latitudes 8°27’E and 8°29’E, situated within present-day Akamkpa Local Government Area of Cross River State, southeastern Nigeria (Fig. 2). As riverine areas, the study locations are linked to each other and other surrounding communities by water bodies. Thus, boats and canoes are the main mode of transportation in the whole area. However, villages and farm settlements within the area are interconnected by bush paths, thereby making the areas also accessible on foot.

The choice of Mbat-Abbiati and Oberekkai Creeks for the present study was informed primarily by the fact that these Creeks represent, to a large extent, the major water bodies that are useful for drinking and irrigation purposes in the region, as well as serve as important habitats for aquatic organisms. Moreover, the Creeks are located in downstream region to receive effluent from the mining and rock quarrying activities in the area.

Sampling and Analysis The surface water occurring at various locations within the study Creeks were sampled for the purpose of this study. Water samples were collected from the two Creeks, and stored in well-labeled ½-litre water bottles which were previously thoroughly washed and rinsed with distilled water. Six sampling points within each Creeks were strategically selected to account for the Creek area, totaling twelve sampling points for both Creeks. All the sampling points were randomly selected within the main body of each Creek, to provide adequate coverage of the entire Creek surface.

At each sampling point, water samples were taken below the surface and labelled according to each sample location. The water samples for cation (Ca 2+ , Mg 2+ , Na +, and K +) and heavy metals determinations were preserved 2- - - - immediately with an on-site acidification with HNO 3, while water samples for anion (SO 4 , Cl , HCO 3 , NO 3 , F) determinations were not acidified.

Physico-chemical parameters such as temperature, pH and electrical conductivity (EC) were measured directly in the field. Temperature was determined with the aid of a Mercury – in – Glass Thermometer, while pH was measured with a digital pH meter. The accuracy of the pH measurement was given as ±0.05 pH unit. Turbidity was measured with a Spectrophotometer (Dr 3000). Conductivity was measured with a conductivity meter, which gives conductivity ( σ) values in µS cm -1. Salinity was determined with the use of salinity meter (HANNA MODEL). Total Dissolved Solids was determined mathematically by multiplying the value of conductivity by 0.6.

37 Pelagia Research Library Bassey Edem Ephraim and Ifedayo Olumide Ajayi Adv. Appl. Sci. Res., 2015, 6(6):36-46 ______

In the laboratory, Biological Oxygen Demand (BOD) was determined through the difference in Dissolved Oxygen (DO) concentrations after sample incubation at 25°C for five (5) days. Titrimetry method was used in the determination of Total alkalinity of water samples using methyl red indicator and the reagent TL AL7 for a drop wise titration until a change in colour was noticed. Total hardness was determined using the spectrophotometry method at a wavelength of 450nm. A whatman No. 1 filter paper containing residue was oven-dried at 50ºC in a laboratory oven for about 1 hour and was used in the determination of Total Suspended Solids (TSS).

Also, reagents of sodium, sulphate, phosphate and chloride at different volumes were respectively used to evaluate + 2- 2- - the concentration of Na , SO 4 , PO 4 and Cl ions through the spectrophometry technique at different wavelengths. For cations and heavy metal analysis, the ICP-MS (Inductively Coupled Plasma-Mass Spectrometry) technique was used to determine trace to ultra-trace concentrations of elements, and ICP-ES (Inductively Coupled Plasma- Emission Spectrometry) was used to confirm higher concentrations of trace elements. Apart from the ICP-MS and ICP-ES techniques that was conducted at the ACME analytical Laboratory in Vancouver - Canada, all other laboratory procedures were observed at the Cross River Water Board Laboratory in Calabar, Nigeria

RESULTS AND DISCUSSION

Selected physicochemical parameters The physicochemical analyses, including TDS, TSS, major ions, heavy metal abundance and computed parameters (e.g., Na%, SAR) of water from Mbat-Abbiati and Oberekkai Creeks are given in Table 1, while the comparison of the mean concentration of the presented chemical parameters of surface waters with maximum allowable limits for drinking water in Nigeria [3], World Health Organization guideline for drinking water [4] and Food and Agricultural Organization water quality guidelines for agriculture, surface irrigation and drainage [5] are given in Table 2. In addition, the Classification of the investigated waters on the basis of Electrical Conductivity (EC), Total Hardness (TH), Total Dissolved Solids (TDS), Sodium Percent (Na%) and Alkalinity of Sodium Hazards (SAR) is presented as Table 3

Table 1. Chemical data of Physicochemical Characteristics, major dissolved components and heavy metals composition of surface waters from Mbat-Abbiati and Oberekkai Creeks of the Great Kwa River in Southeastern Nigeria

ABBIATI OBBERAKHAI

AW-1 AW-2 AW-3 AW-4 AW-5 AW-6 OW-1 OW-2 OW-3 OW-4 OW-5 OW-6

Temp (°C) 27.5 27.5 27.5 27.4 27.3 27.3 27.5 27.3 27.5 27.3 27.3 27.4 pH 6.14 6.21 6.27 6.36 6.5 6.61 5.62 5.7 5.74 5.81 5.95 6.25 EC(µs/cm) 23.4 25.8 41.5 46.8 39.9 27.3 49.9 58.9 54.7 55.8 55.6 62.5 SAL(mg/L) 0.013 0.012 0.019 0.005 0.007 0.02 0.006 0.008 0.012 0.013 0.008 0.003 TURB(NTU) 2.54 2.2 9.54 4.49 3.34 3.02 5.43 6.63 2.63 3.79 7.61 5.13 ALK(Mg/l CaCO 3) 14.4 14 14.3 14.21 13.18 13.21 14.24 14.25 14.37 14.42 14.44 14.11 Total Hardness (TH) 9.37 11.72 19.98 25.86 11.19 9.34 16.66 19.2 22.34 30.21 15.25 20.45 (Mg/l CaCO 3) BOD(mg/L) 0.17 0.14 0.15 0.14 0.13 0.2 0.32 0.31 0.34 1.96 0.52 0.31 TDS(mg/L) 14.04 15.48 24.9 28.08 23.94 16.38 29.94 35.34 32.82 33.48 33.36 37.5 TSS(mg/L) 0.21 0.11 0.1 0.12 0.11 0.22 0.15 0.11 0.12 0.11 0.1 0.12 Ca 2+ (mg/L) 21.64 21.18 25.09 25.41 24.87 25.32 11.45 12.62 11.77 11.52 12.12 12.5 Mg 2+ (mg/L) 2.11 2.11 2.57 2.55 2.6 2.68 1.23 1.19 1.14 1.06 1.09 1.11 Na +(mg/L) 1.87 1.81 2 1.97 1.96 2.03 1.12 0.89 0.91 0.81 0.87 0.87 K+(mg/L) 0.61 0.63 0.67 0.57 0.36 0.77 0.36 0.43 0.48 0.5 0.54 0.53 Cl -(mg/L) 0.66 0.61 1.02 0.26 0.4 1.06 0.29 0.46 0.62 0.68 0.46 0.12 2- SO 4 (mg/L) 13 17 23 21 20 20 20 6 5 6 5 5 - HCO 3 (mg/L) 17.6 17.1 17.4 17.3 16.1 16.1 17.4 17.4 17.5 17.6 17.6 17.2 2- PO 4 (mg/L) 0.54 0.66 1.79 0.81 1.11 0.92 0.44 0.55 1.17 0.48 18.84 5.21 Cr(mg/L) 0.01 0.02 0.01 0.02 0.04 0 0.02 0.03 0.05 0.05 0.02 0.05 Cu(mg/L) 0.4 0.73 0.73 0.5 0.73 0.7 0.21 0.33 0.18 0.15 0.38 0.42 Fe(mg/L) 0.9 0.73 0.75 0.87 0.35 0.3 3.81 6.32 5.53 3.72 4.12 4.1 Mn(mg/L) 0.77 0.75 2.56 0.69 0.51 0.83 1.2 1.22 1.38 1.02 1.34 1.07 Zn(mg/L) 0.21 0.27 0.15 0.2 0.22 0.5 0.14 0.18 0.21 0.21 0.26 0.25 Na% 15.41 15.55 15.36 15.04 15.44 15.57 16.85 14.04 14.71 13.85 13.82 13.56 SAR 0.23 0.23 0.26 0.25 0.26 0.27 0.18 0.17 0.17 0.16 0.16 0.16

The graphical representation of variations of selected physicochemical parameters in the surface waters are presented as Fig. 3. As shown in Table 2 and Fig 3, the water in both Creeks are relatively warm with consistent temperatures, ranging from 27.3 to 27.5 ºC, and an average of 27.42 ºC for water from Mbat-Abbiati Creek and 27.38 ºC for water from Oberekkai Creek (Table 2). The recorded average temperature lies within the 25 to 30°C range required by fish and other aquatic organisms to grow properly [11].

38 Pelagia Research Library Bassey Edem Ephraim and Ifedayo Olumide Ajayi Adv. Appl. Sci. Res., 2015, 6(6):36-46 ______

Table 2. Statistical summary and their comparison with the NSO and WHO standards for drinking water for surface waters from Mbat- Abbiati and Oberekkai Creeks of the Great Kwa River in Southeastern Nigeria

ABIATI OBERRAKKA FAO SON (2007) WHO (2011) RANGE MEAN (SD) RANGE MEAN (SD) (1985) Temp (°C) 27.30 – 27.50 27.42 (0.10) 27.30 – 27.50 27.38 (0.10) na na na pH 6.14 – 6.61 6.35 (0.18) 5.62 – 6.25 5.85 (0.23) 6.5 – 8.5 na na BOD (mg/L) 0.13 – 0.20 0.16 (0.03) 0.31 – 1.96 0.63 (0.66) na na na TURB(NTU) 2.20 – 9.54 4.19 (2.74) 2.63 – 7.61 5.20 (1.82 5 na na TSS(mg/L) 0.10 – 0.22 0.15 (0.05) 0.10 – 0.15 0.12 (0.02) na na na EC(µs/cm) 23.40 – 46.80 34.12 (9.79) 49.90 – 62.50 56.23 (4.23) 1000 na na TDS(mg/L) 14.04 – 28.08 20.47 (5.87) 29.94 – 37.50 33.74 (2.54) 500 na na SAL(mg/L) 0.01 – 0.02 0.01 (0.01) 0.00 – 0.01 0.01 (0.00) na na na ALK(Mg/l 13.18 – 14.40 13.88 (0.55) 14.11 – 14.44 14.31 (0.13) na na na CaCO 3) HARDNESS 9.34 – 25.86 14.58 (6.79) 15.25 – 30.21 20.69 (5.32) 150 na na (Mg/L CaCO 3) Ca 2+ 21.18 – 25.41 23.92 (1.96) 11.45 – 12.62 12.00 (0.50) na na na Mg 2+ 2.11 – 2.68 2.44 (0.26) 1.06 – 1.23 1.14 (0.06) 0.2 na na Na + 1.81 – 2.03 1.94 (0.08) 0.81 – 1.12 0.91 (0.11) 200 na na K+ 0.36 – 0.77 0.60 (0.14) 0.36 – 0.54 0.47 (0.07) na na na Cl - 0.26 – 1.06 0.67 (0.32) 0.12 – 0.68 0.44 (0.21) 250 na na 2- SO 4 13.00 – 23.00 19.00 (3.52) 5.00 – 20.00 7.83 (5.98) 100 na na - HCO 3 16.10 – 17.60 16.93 (0.67) 17.20 – 17.60 17.45 (0.15) na na na 2- PO 4 0.54 – 1.79 0.97 (0.45) 0.44 – 18.84 4.45 (7.29) na na na Cr 0.00 – 0.04 0.02 (0.01) 0.02 – 0.05 0.04 (0.02) 0.05 0.05 0.1 Cu 0.40 – 0.73 0.63 (0.14) 0.15 – 0.42 0.28 (0.11) 1 2 0.2 Fe 0.30 – 0.90 0.65 (0.26) 3.72 – 6.32 4.60 (1.07) 0.3 na 5 Mn 0.51 – 2.56 1.02 (0.76) 1.02 – 1.38 1.21 (0.14) 0.2 na 0.2-10 Zn 0.15 – 0.50 0.26 (0.12) 0.14 – 0.26 0.21 (0.04) 3 na 2 Na% 15.04 – 15.57 15.34 (0.19) 13.56 – 16.85 14.47 (1.23) – – – SAR 0.23 – 0.27 0.25 (0.02) 0.16 – 0.18 0.16 (0.01) – – –

Table 3. Classification of surface waters from Mbat-Abbiati and Oberekkai Creeks of the Great Kwa River in Southeastern Nigeria on the basis of Electrical Conductivity (EC), Total Hardness (TH), Total Dissolved Solids (TDS), Sodium Percent (Na%) and Alkalinity of Sodium Hazards (SAR)

No of Samples Parameter Range Water Class Mbat-Abbiati Creek Oberekkai Creek Remarks (n = 6) (n = 6) <250 Excellent 6 6 250 – 750 Good – – EC 750 – 2000 Permissible – – Excellent 2000 – 3000 Doubtful – – >3000 Unsuitable – – <75 Soft 6 6 75 – 150 Moderately Hard – – TH(Sawyer et al., 2003) Soft Water 150 – 300 Hard – – >300 Very Hard – – <1,000 Fresh 6 6 1,000 – 3,000 Moderately Saline – – TDS(USGS, 2000) Fresh Water 3,000 – 10,000 Saline – – >10,000 Highly Saline – – <20 Excellent 6 6 20 – 40 Good – – Na%(after Wilcox, 1955) 40 – 60 Permissible – – Excellent 60 – 80 Doubtful – – >80 Unsuitable – – <10 Excellent 6 6 Alkalinity Hazard (SAR) 10 – 18 Good – – Excellent (after Richard, 1954) 18 – 26 Doubtful – – >26 Unsuitable – –

The pH of surface water from Mbat-Abbiati Creek ranges from 6.14 to 6.61 with an average of 6.35 (Table 2 and Fig 3) which shows that majority of the water samples are mildly acidic to alkaline in nature. Similarly, in the Oberekkai Creek, the pH values ranged from 5.6 to 6.25 with an average of 5.85 (Table 2 and Fig 3), which shows slight acidic character. The permissible limit of pH in drinking water, according to the Standard Organization of Nigeria, varies between 6.5 and 8.0 [3]. Among the 12 samples analyzed in this study, 10 of them have pH values that are lower than the permissible range (Table 1). The slightly acidic nature of the water favours the mobility of trace elements which are non-biodegradable and hazardous. This is because pH has a strong effect on dissolution of trace elements which become more mobile in water system having acidic pH and vice versa [12].

39 Pelagia Research Library Bassey Edem Ephraim and Ifedayo Olumide Ajayi Adv. Appl. Sci. Res., 2015, 6(6):36-46 ______

Fig. 1. Geological map sketch of southeastern Nigeria showing the showing the location of the Calabar Flank (modified after Ofomata, 1973)

Figure 2. Geological map of present-day Cross River State in south-eastern Nigeria, showing the geology of study area

40 Pelagia Research Library Bassey Edem Ephraim and Ifedayo Olumide Ajayi Adv. Appl. Sci. Res., 2015, 6(6):36-46 ______

Fig. 3. Graphical representation of variations of selected physicochemical parameters in surface waters of Mbat-Abbiati and Oberrakkai Creeks of the Great Kwa River, Southeastern Nigeria

Biological Oxygen Demand (BOD) is a measure of the biological activities in a water body, and an indication of the organic load, as well as a pollution index, especially for water bodies receiving organic effluent. BOD values for the two investigated Creeks ranged from 0.13 to 1.96mg/L, with mean value of 0.16mg/L for Mbat-Abbiati and 0.63mg/L for Oberekkai. The low BOD values recorded for the Creeks is an indication of the limited levels of organic matter decomposition which often requires oxygen from the water. This decrease in BOD levels will increase the amount of dissolved oxygen available to aquatic organisms for survival in the Creeks.

The electrical conductivity (EC) measured in the water from Mbat-Abbiati Creek ranged from 23.40 to 46.80µs/cm with a mean value of 34.12 µs/cm in samples; while that measured in water samples from Oberekkai Creek ranged from 49.90 to 62.50 µs/cm with an average value of 56.23 µs/cm. All the water samples considered have EC values below the 1000 µs/cm EC permissible limit of the Standard Organization of Nigeria [3]. Indications from Table 3 is that the studied waters are of low salt contents as it classifies under the excellent class. This agree with the low

41 Pelagia Research Library Bassey Edem Ephraim and Ifedayo Olumide Ajayi Adv. Appl. Sci. Res., 2015, 6(6):36-46 ______salinity (0 – 0.02 mg/L) measured within the waters (Table 2, Fig. 3). Thus, based on electrical salinity (EC), the waters are suitable for drinking and agricultural usage.

Fig. 4. Graphical representation of variations of Total Dissolved Solids (TDS) and Total Suspended Solids (TSS) in surface waters at six stations in Mbat-Abbiati and Oberrakkai Creeks of the Great Kwa River in Southeastern Nigeria

Fig. 5. Graphical representation of variations of major dissolved cations in surface waters at six stations in Mbat-Abbiati and Oberrakkai Creeks of the Great Kwa River in Southeastern Nigeria

The total alkalinity and total hardness measured in the waters of the study area ranged between 13.18 – 14.44 mg/L and 9.34 – 30.21mg/L respectively. The water therefore classifies as soft water based on total hardness (TH) [13] (Table 3). The levels of total alkalinity and total hardness for good fish culture lie within the range 20 – 300 mg/L, according to [14]. The results of the present study therefore show that the water generally falls below this range in terms of alkalinity, but is slightly within the range in terms of total hardness. The hardness of the water increases its

42 Pelagia Research Library Bassey Edem Ephraim and Ifedayo Olumide Ajayi Adv. Appl. Sci. Res., 2015, 6(6):36-46 ______boiling point and has no remarkable effects on human beings. It is most likely due to leaching of calcium and magnesium ions into the surface waters [15].

Turbidity of the water samples ranged from 2.20 to 9.54 NTU, with a mean value of 4.19 NTU for Mbat-Abbiati Creek and 5.20 NTU for Oberekkai Creek.

Fig. 6. Graphical representation of variations of major dissolved anions in surface waters at six stations in Mbat-Abbiati and Oberrakkai Creeks of the Great Kwa River in Southeastern Nigeria

Total Dissolved Solids (TDS) and Total Suspended Solids (TSS) The graphical representation of variations of Total Dissolved Solids (TDS) and Total Suspended Solids (TSS) in the surface waters of Mbat-Abbiati and Oberekkai Creeks of the Great Kwa River in Southeastern Nigeria are presented as Fig. 4. As shown (Table 2, Fig 4), the total Suspended Solids (TSS) ranged from 0.10 – 0.22 mg/L, with a mean value of 0.15mg/L for Mbat-Abbiati and 0.12mg/L for Oberekkai Creek. This implies that the total amount of suspended solids in the Creek water is at the barest minimum, thus indicating good water quality status. Similarly, the measured total dissolved solids (TDS) gives an indication of low mineralization as it ranges from 14.04 to 37.50 mg/L, with 20.47mg/L and 33.74mg/L being average values for Mbat-Abbiati and Oberekkai Creeks respectively. Moreover, all the samples considered falls within the range of the fresh water class (Table 3) [16, 17, 18]. Thus, the waters are not only of low mineralization, but suitable for drinking and irrigation purposes as the reported TDS content has no adverse effects on crop production [19].

Major Dissolved Ions The graphical representation of variations of major dissolved cations in the surface waters of Mbat-Abbiati and Oberekkai Creeks of the Great Kwa River in Southeastern Nigeria are presented as Fig. 5, while that for anions in the waters are given in Table 6.

As shown in Fig 5, calcium and magnesium in the waters of the study area ranged between 21.18 – 25.41 mg/L and 2.11 – 2.68 mg/L respectively for surface waters from Mbat-Abbiati Creek. While those of water from Oberekkai Creek ranged between 11.45 – 12.62 mg/L and 1.06 – 1.23 mg/L respectively. The very high proportion of these species in the waters preclude the consideration of weathering of silicate minerals as important contributors of the ions. The ions are most likely sourced from the dissolution of carbonate minerals. The occurrence of vast deposits of limestones as parts of the lithology of the catchment area supports this claim. Na and K concentrations varied between 1.81 – 2.03 mg/L and 0.36 – 0.77 mg/L respectively for surface waters from Mbat-Abbiati Creek. While those of water from Oberekkai Creek ranged between 0.81 – 1.12 mg/L and 0.36 – 0.54mg/L respectively. The measured sodium contents of the water from the two Creeks is below the desirable limits of 200 mg/L for drinking water [3]. In terms of origin, sodium in aquatic systems are largely controlled by saline intrusions, evaporate dissolution and weathering of silicate minerals. However, Na and K in the study area appears to be derived mostly

43 Pelagia Research Library Bassey Edem Ephraim and Ifedayo Olumide Ajayi Adv. Appl. Sci. Res., 2015, 6(6):36-46 ______from the weathering of hard rocks. Thus, the source of Na + and K + in the water are most likely due to weathering of silicate minerals from igneous and metamorphic rocks [20] of the adjoining Oban massif basement. In addition, an insignificant concentration of sodium may be sourced through cation exchange reaction and human activities [21], while potassium can also be sourced from fertilizers and manures from the surrounding agricultural fields. In terms of mean abundance, the concentration of cations in the investigated waters is in the order Ca 2+ > Mg 2+ > Na + > K + for both Creeks.

As shown in Fig 6, there appear to be divergence in the relative abundance of major anions in the investigated 2- - 3- - waters. For instance, the trend for water from Mbat-Abbiati Creek is: SO 4 > HCO 3 > PO 4 >Cl , while the order for - 2- 3- - waters from Oberekkai Creek is HCO 3 > SO 4 > PO 4 >Cl . The sulphate concentration in the waters ranged between 13.00 – 23.00 mg/L and 5.00 – 20.00 mg/L for Mbat-Abbiati and Oberekkai Creeks, respectively. The increase of sulphate in the waters is mainly due to the influence of agricultural and anthropogenic activities [21].

- The HCO 3 ion concentrations vary from 16.10 to 17.6 mg/L with an average value of 16.93 mg/L and 17.20 to 17.60 mg/L with a mean value 17.45 mg/L for Mbat-Abbiati and Oberekkai Creeks, respectively. The source of the bicarbonates in water may be due to the oxidation and decomposition of organic pollutants [22]. However there is no prescribed permissible limit of for this ion.

In the study area, chloride ranged between 0.26 – 1.06 mg/L and 0.12 – 0.68mg/L respectively for surface waters from Mbat-Abbiati and Oberekkai Creeks respectively. The range of chloride is low and typical of tropical freshwaters, even though high levels are not known to be injurious to water organisms [11]). The chlorine in the waters originates from both natural and anthropogenic sources like runoff containing inorganic fertilizers, animal feeds, irrigation drainage and seawater intrusion in coastal area [23, 24, 25, 26]

3- 3- In most natural waters, PO 4 concentrations range from 0.005 to 0.020mg/L [27]. Levels of PO 4 in this study varied between 0.54 – 1.79 mg/L, with a mean concentration of 0.97mg/L for water from Mbat-Abbiati and between 0.44 – 18.84 mg/L with a mean concentration of 4.45 mg/L for water from Oberekkai. These values exceed the levels in most natural waters [27]. High concentrations of phosphate are largely responsible for eutrophic conditions in a water body. Thus, Mbat-Abbiati and Oberekkai Creeks are generally rich in phosphates and this further 2- enhances general nutrient enrichment on the Creeks as evidenced by SO 4 concentrations.

Heavy Metal Abundance The results presented in Table 2 shows that the concentrations of most of the heavy metal in surface waters from Mbat-Abbiati and Oberekkai Creek are within the respective permissible limits of the Standard Organization of Nigeria [3], World Health Organization [4] and Food and Agriculture Organization of Nigeria [5]. The only exception to this assertion are concentrations of iron and manganese which in most cases exceeded values quoted in these standards (Table 2). Worst affected in this regards are contents of Fe and Mn in the Oberekkai Creek waters. The mean values of these heavy metals at different sample locations in Mbat-Abbiati Creek showed Mn to be the most abundant heavy metal, followed by Fe, Cu, Zn and Cr. However, in Oberekkai Creek, the ordering is different as Fe is the most abundant heavy metal, followed by Mn, Cu, Zn and Cr. It appears mining/rock quarrying, agricultural and other anthropogenic activities are mainly responsible for elevated levels of the heavy metals in surface waters of Mbat-Abbiati and Oberekkai Creek.

The levels of Mn in the Creek water varied from 0.51 to 2.56 mg/L, with mean values of 1.02 mg/L and 1.21 mg/L in Mbat-Abbiati and Oberekkai Creeks, respectively. The limit of Mn in water for use in aquatic ecosystems was exceeded by the two Creeks, while Mn concentrations in both Creeks fell below the Nigerian provisional guideline value for drinking water [3]. The accumulation of Mn in the Creek water is a cause for concern as it could lead to manganese toxicity in biota.

The concentration of Iron in the Creek waters ranged between 0.30 and 6.32 mg/L, with average values of 0.65 mg/L and 4.61 mg/L in Mbat-Abbiati and Oberekkai Creeks, respectively. The concentration of Iron in both Creeks was observed to be higher than the 0.2 mg/L maximum contaminant limit (MCL) in fresh water set by [28]. Some level of caution must be exercised with respect to Fe content of the Creek waters before it can be considered for agricultural purposes because at some locations (Table 1), the Fe concentrations exceeded the 5 mg/L standard of the Food and Agricultural Organization [5]. Most ferrous compounds in aquatic environments results from the precipitation of Fe in alkaline and oxidizing conditions [29]. Some contributions may also come from exchangeable Fe which usually relates to adsorbed metals on the sediment surface as these can be easily remobilized into the Creek water [30].

44 Pelagia Research Library Bassey Edem Ephraim and Ifedayo Olumide Ajayi Adv. Appl. Sci. Res., 2015, 6(6):36-46 ______

Copper concentration in the Creek waters varied from 0.15 to 0.73 mg/L, with mean values of 0.63 mg/L and 0.28 mg/L in Mbat-Abbiati and Oberekkai Creeks, respectively. Similarly, the levels of Zn in the Creek water ranged from 0.14 to 0.50 mg/L, with mean values of 0.26 and 0.21 mg/L in Mbat-Abbiati and Oberekkai Creeks, respectively. In addition, the concentration of chromium in the waters varied from 0 to 0.05 mg/L, with an average value of 0.02 ppm and 0.04 ppm in Mbat-Abbiati and Oberekkai Creeks, respectively.

Considering the values quoted as permissible limits in the Nigerian Standard [3], World Health Organization Guideline for drinking water [4] and Food and Agriculture standards [5], it becomes necessary to conclude that there is no detrimental effect for the aquatic ecosystem in both Creeks regarding Cu, Zn and Cr toxicity.

Sodium Percent (Na %) and Alkalinity Hazard (SAR) It was also considered necessary to evaluate the suitability of the surface waters from Mbat-Abbiati and Oberekkai Creek for irrigation purposes, using parameters such as Sodium Percent (Na %) [31] and Alkalinity Hazard (SAR) [32].

Sodium Percent (Na %) is a good indices of irrigation as sodium in water reacts with soils, resulting in the reduction of permeability. This reduction of soil permeability can have adverse effect on irrigation [33]. The sodium content in water can be expressed by the term ‘sodium percent, (Na %)’, which is computed using the formula,

Na% = (Na ++K +) / (Ca 2+ +Mg 2+ +K ++Na +) ×100

Where all the concentrations were in meq/L.

The ‘alkalinity or sodium hazard’ is another very good tool for evaluation of the suitability of water for irrigation purposes. It can be obtained through the sodium absorption ratio (SAR) which is computed using the equation given below, after Karnath [20]:

SAR=Na +/ 1/2 (Ca 2+ +4Mg 2+ ) where all concentrations are expressed in meq/L.

The results of the Sodium Percent (Na %) and sodium absorption ratio (SAR) computation presented in Table 3 show that the surface waters are most suitable for irrigation purposes.

CONCLUSION

Following recent concerns about solute pollution, heavy metal contamination and potential impact on food systems and human health associated with the Great Kwa River and its tributaries, it became necessary to determine the suitability of the waters of Mbat-Abbiati and Oberekkai Creeks for drinking, irrigation and other purposes. Accordingly, water samples from these Creeks were subjected to various analysis for the determination of the chemical characteristics. The results show that the waters displays favorable conditions of temperature, and exhibits low values of total dissolved solids (TDS), electrical conductivity (EC) and salinity. The reduced BOD contents accounts for increased Dissolved Oxygen available for the survival of aquatic organisms in the Creek, while observed slight acidic character of the water appear critical. Considering the mean abundance of the major ions, the concentration of cations in the investigated waters of both Creeks is in the order Ca 2+ > Mg 2+ > Na + > K +, while that 2- - 3- - - 2- 3- - for anions follow the trend: SO 4 > HCO 3 > PO 4 >Cl and HCO 3 > SO 4 > PO 4 >Cl for water from Mbat-Abbiati and Oberekkai Creeks respectively. Among the heavy metals studied, Fe and Mn are the most abundant, followed by Cu, Zn and Cr. Also, apart from Mg, Fe and Mn, the concentration of most of the studied chemical species in the investigated waters are within the respective permissible limits of the Standard Organization of Nigeria, World Health Organization and Food and Agriculture Organization of Nigeria. Thus, the water is suitable for drinking, irrigation and crop production as both Creeks appear free from any significant pollution or contamination threat - 2 3 - 2+ 2+ + + regarding HCO 3 , SO 4 , PO 4 , Cl , Ca , Mg , Na , K , Cu, Zn and Cr. However, despite the fact that sodium percent (Na %) and alkalinity or sodium hazard (SAR) underlines the suitability of the waters for irrigation purposes, some level of caution must be exercised with respect to Mg, Mn, and Fe contents of the Creek waters before the Creek waters can be considered for agricultural purposes. Besides, the accumulation of Mn in the waters is a cause for concern for marine life as it could lead to manganese toxicity in biota. It appears mining/rock quarrying, agricultural and other anthropogenic activities, as well as lithology are responsible for the sourcing of the various major ions, heavy metal, among other chemical character of the surface waters of Mbat-Abbiati and Oberekkai Creek.

45 Pelagia Research Library Bassey Edem Ephraim and Ifedayo Olumide Ajayi Adv. Appl. Sci. Res., 2015, 6(6):36-46 ______

In conclusion, the present study suggests the need for constant monitoring of quality status of water bodies so as to detect when the various chemical species increases beyond tolerable limits. A follow up investigation is recommended to determine the extent to which some of the biotic species including fish and food crops from the study areas appreciates the present quality status of the surface waters of Mbat-Abbiati and Oberekkai Creek.

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