Abstract
This study was carried out to assess the suitability of groundwater for drinking and irrigation purposes by interpreting the hydrochemical species of groundwater samples. Six water samples were collected and assess to determine the concentration of some ions, pollution load index (PLI), contamination factor (CF), water quality index (WQI), sodium adsorption ratio (SAR), magnesium hazard (MH), Kelly ratio (KR) and percentage sodium (%Na). The result revealed that most of the ions have concentrations within the WHO permissible limit for drinking water except biological oxygen demand (BOD), chemical oxygen demand (COD) and , which exceeded the WHO standard in some samples. The mean abundance of the cations is , while that of the anions is . The result reveals that and are the most abundant cation and anion respectively. CF reveals a low concentration (<1) of , , , , and high concentration (>1) of . The values of PLI were very low indicating no pollution. The WQI reveals the samples with excellent (<50) rating, while those above 100 (>100) were rated as poor. The SAR, MH, KR and %Na reveal the groundwater status for irrigation based on the ratings of the indices.
HIGHLIGHTS
Groundwater repository was assessed using the geochemical parameters.
Concentrations of the ions were compared with the WHO standard for drinking water.
Water quality indices (PLI, CF and WQI) were determined.
Irrigation indices (SAR, MH, %Na and KR) were computed.
The results reveal the status of groundwater for domestic and irrigation purposes.
INTRODUCTION
Water plays an essential role in many processes/activities in our society and provides both environmental and economic benefits. Contaminated groundwater poses a serious threat to humans as it may lead to water-borne diseases, which are dangerous to health. Also, agricultural productivity depends on the suitability of the groundwater, which will boost crop yield. Groundwater is an essential natural asset that supports domestic and agricultural purposes and its suitability is of great concern for its sustainability and effective use (George et al. 2015; Obiora et al. 2015; Ekanem et al. 2020). A greater percentage of water supplies for domestic, agricultural and industrial uses are tapped from groundwater, due to its availability and proximity (Ibe et al. 2020; Akakuru et al. 2021). Groundwater quality depends not only on natural factors such as aquifer lithology, groundwater velocity, quality of recharge waters and interaction with other types of water or aquifers but also on human activities and the environment. The quality of groundwater is affected by contaminants such leachates, oil pollution etc, which emanates from different sources and infiltrates into the aquifer units through the pores and crevices of rocks or soils after decomposition and becomes a point source of groundwater pollution (Hossain et al. 2014; Ganiyu et al. 2015; Ibuot et al. 2019). Rocks and sediments contain contaminants, solutes and groundwater flowing through them dissolves these substances thus changing the chemistry of groundwater repositories. Groundwater suitability depends on the hydrogeochemical properties and susceptibility of the aquifer layers to pollution (Wang et al. 2010; Okolo et al. 2018; Ekanem et al. 2020). Also, the aquifer susceptibility depends on porosity, permeability and overburden thickness of geologic formation (George et al. 2014; Obiora et al. 2015; Ibuot et al. 2017; Oni et al. 2017; Ibe et al. 2020).
The groundwater repositories are continuously overstretched by processes such as saltwater intrusion, movement of leachates, oil spillage, surface and subsurface leakages, and leakage from septic tanks (Umar & Igwe 2019; Akakuru et al. 2021). The quality of groundwater is largely controlled by discharge-recharge pattern, nature of host and associated rocks as well as contaminated activities (Mishra et al. 2013; Ibuot et al. 2019). Groundwater contains a high level of dissolved solids due to its contact with aquifer geologic materials. According to Rawat et al. (2018), groundwater quality degradation may be due to geochemical reactions in the aquifers and soils and, also when it is supplied through improper canals/drainages for irrigation. The suitability of groundwater for agriculture depends on the nature of the mineral elements in the water and their impacts on both the soil and plants (Singh et al. 2013; Rawat et al. 2018; Thomas et al. 2020).
Groundwater pollution happens mostly due to percolation of pluvial water and the infiltration of contaminants through the soil (George et al. 2014; Hossain et al. 2014; Ganiyu et al. 2015). The degradation in groundwater quality has been a serious issue in both human health and agriculture sector as it affects agricultural productivity. The excess amount of dissolved elements affect human health when its concentration exceeds the World Health Organization (WHO) permissible limits and also affects plants growth by changing the uptake power of plant due to complex changes that arise out of the osmotic processes. The concentration and toxicity of contaminants determine the extent of threats. The chemicals in the wastes are usually disposed without appropriate measures leaches and percolate into the aquifer layer, which have the potential to change the groundwater chemistry and thus pollute groundwater resources.
Pollution in coastal aquifers is connected to numerous factors such as: hydraulic gradient, groundwater recharge and discharge rate and nature of geological formation (Mosuro et al. 2017; Yetiş et al. 2019). Going by the debilitating effects of contaminated groundwater in the Federal College of Education (Technical), Omoku, this work is designed to evaluate groundwater quality by assessing the physicochemical properties and water quality indices of groundwater samples in the study area and its environs.
Location and geological setting of the study area
MATERIALS AND METHOD
Hydrogeochemical and physical properties of water samples
Groundwater from boreholes located within the vicinity of the study were considered for this study. A total of six water samples were collected from six different boreholes across the area without contamination in the month of February, 2022. The borehole locations were: BH 1, BH 2, BH 3, BH 4, BH 5 and BH 6. The water samples were split into two containers, one for anions and the other for cations to determine their concentration in milligrammes per litre (). The values of pH and alkalinity were measured using a multi-parameter analyser. Alkalinity is a property of water that depends on the presence in the water of some chemicals such as carbonates, bicarbonates and hydroxides (Thomas et al. 2020). The values of electrical conductivity (EC) of the water samples was measured at the point of collection using a Wissenschaftlich-Technische Werkstätten LF91 (Ec) meter. The total dissolved solids (TDS) and dissolved oxygen (DO) were determined at the point collection. The DO was measured with the aid of a dissolved oxygen meter and sensor. The values of the chemical oxygen demand (COD) and biological oxygen demand (BOD) were determine in the laboratory using standard procedures. These containers were initially washed with 0.05 M HCl and filtered through membranes of pores and then rinsed with ionized water. The water samples were acidified with concentrated nitric acid () to homogenize and prevent metallic ions from sticking to the walls. The analysis of the bicarbonates () was carried out using a standard technique of titration to obtain their concentrations. The concentrations of the cations (, , , and ) were determined using the Atomic Adsorption Spectrometer model AA-7000 Shimadzu, Japan ROM version 1.01, while the anions , , ) were determined in the laboratory using the standard procedure of titrimetric method.
Pollution, water quality and irrigation water quality indices
Assessing drinking water quality and pollution level
This study makes use of different indices to assess the water quality of the study area. The indicators include: water quality index (WQI), contamination factor (CF) and pollution load index (PLI).
WQI
CF
PLI
Assessing irrigation water quality
The suitability of groundwater quality for irrigation was determine by utilizing the concentrations of sodium, calcium and magnesium (Raju et al. 2009; Sisir & Anindita 2012). The indicators sodium adsorption ratio (SAR), magnesium adsorption ratio (MAR), Kelly's ratio (KR), sodium percentage (Na%) and magnesium hazard (MH) will be estimated.
SAR
MH
KR
%Na
RESULTS AND DISCUSSION OF RESULTS
Results in Table 1 show the concentrations of both the physical and chemical parameters considered in the water samples collected from six different boreholes within the vicinity of the study area.
S/N . | Parameters . | BH 1 . | BH 2 . | BH 3 . | BH 4 . | BH 5 . | BH 6 . | WHO (2017) . |
---|---|---|---|---|---|---|---|---|
1 | pH | 7.7 | 7.4 | 7.5 | 7.3 | 7.5 | 7.8 | 6.5–8.5 |
2 | EC ( | 19.10 | 53.00 | 14.70 | 23.40 | 36.80 | 27.40 | 500 |
3 | TDS ( | 82.31 | 99.94 | 76.79 | 105.90 | 83.6 | 74.15 | 500 |
4 | Alkalinity ( | 0.10 | 0.05 | 0.06 | 0.06 | 0.18 | 0.07 | 200 |
5 | DO ( | 8.00 | 11.20 | 6.40 | 5.80 | 11.50 | 7.05 | - |
6 | BOD ( | 9.60 | 12.80 | 8.00 | 6.08 | 8.30 | 7.50 | 2 |
7 | COD ( | 32.00 | 42.40 | 26.40 | 28.40 | 23.80 | 36.50 | 10 |
8 | ( | 7.01 | 4.03 | 5.57 | 4.25 | 7.53 | 6.45 | 250 |
9 | ( | 24.14 | 45.44 | 19.88 | 26.85 | 18.37 | 37.72 | 250 |
10 | ( | BDL | BDL | BDL | BDL | BDL | BDL | 200 |
11 | ( | 0.52 | 0.98 | 0.27 | 0.62 | 0.34 | 0.73 | 200 |
12 | ( | 1.70 | 4.72 | 3.56 | 1.58 | 6.81 | 5.06 | 200 |
13 | ( | BDL | 1.33 | 0.03 | 0.27 | 1.20 | 0.46 | 7.5 |
14 | ( | 0.07 | 0.12 | 0.11 | 0.21 | 0.18 | 0.06 | 50 |
15 | ( | BDL | BDL | 0.07 | 0.06 | 0.03 | 0.07 | 0.5 |
16 | ( | 0.49 | 0.03 | 0.25 | 0.18 | 0.23 | 0.09 | 0.3 |
S/N . | Parameters . | BH 1 . | BH 2 . | BH 3 . | BH 4 . | BH 5 . | BH 6 . | WHO (2017) . |
---|---|---|---|---|---|---|---|---|
1 | pH | 7.7 | 7.4 | 7.5 | 7.3 | 7.5 | 7.8 | 6.5–8.5 |
2 | EC ( | 19.10 | 53.00 | 14.70 | 23.40 | 36.80 | 27.40 | 500 |
3 | TDS ( | 82.31 | 99.94 | 76.79 | 105.90 | 83.6 | 74.15 | 500 |
4 | Alkalinity ( | 0.10 | 0.05 | 0.06 | 0.06 | 0.18 | 0.07 | 200 |
5 | DO ( | 8.00 | 11.20 | 6.40 | 5.80 | 11.50 | 7.05 | - |
6 | BOD ( | 9.60 | 12.80 | 8.00 | 6.08 | 8.30 | 7.50 | 2 |
7 | COD ( | 32.00 | 42.40 | 26.40 | 28.40 | 23.80 | 36.50 | 10 |
8 | ( | 7.01 | 4.03 | 5.57 | 4.25 | 7.53 | 6.45 | 250 |
9 | ( | 24.14 | 45.44 | 19.88 | 26.85 | 18.37 | 37.72 | 250 |
10 | ( | BDL | BDL | BDL | BDL | BDL | BDL | 200 |
11 | ( | 0.52 | 0.98 | 0.27 | 0.62 | 0.34 | 0.73 | 200 |
12 | ( | 1.70 | 4.72 | 3.56 | 1.58 | 6.81 | 5.06 | 200 |
13 | ( | BDL | 1.33 | 0.03 | 0.27 | 1.20 | 0.46 | 7.5 |
14 | ( | 0.07 | 0.12 | 0.11 | 0.21 | 0.18 | 0.06 | 50 |
15 | ( | BDL | BDL | 0.07 | 0.06 | 0.03 | 0.07 | 0.5 |
16 | ( | 0.49 | 0.03 | 0.25 | 0.18 | 0.23 | 0.09 | 0.3 |
BDL: Below detectable limit.
Physical and oxygen-related parameters
Hydrogeochemical parameters
The geochemical results (Table 1), the anions in order of abundance are The values of ranged from 4.03–7.53 with a mean of 5.81 and with the WHO standard for drinking water. High concentration of may increase the levels of hardness in groundwater repositories, and may corrode plumbing done with copper. A high concentration of can lead to irritation of the lungs which cause serious disease of the lung. The has values ranging from 18.37–45.44 and a mean value of 26.94 , which were within the WHO permissible limit of 250 . If exceeds 250 , it will produce a salty taste, which is not good for human consumption (Rahman et al. 2015). The concentration in groundwater may be due to the presence of chlorides from rocks, seawater intrusion, or contamination by industrial waste or domestic sewage (Saha et al. 2019). The low concentration of is attributed to low salinity of the groundwater of the study area.
CF
S/N . | Sample No. . | Contamination Factor (CF) . | PLI . | WQI . | |||||||
---|---|---|---|---|---|---|---|---|---|---|---|
. | . | . | . | . | . | . | . | ||||
1 | BH 1 | 0.0280 | 0.0966 | 0.0026 | 0.0085 | 0 | 0.0014 | 0 | 1.6333 | 0 | 544.4482 |
2 | BH 2 | 0.0161 | 0.1818 | 0.0049 | 0.0236 | 0.1773 | 0.0024 | 0 | 0.1067 | 0 | 38.00885 |
3 | BH 3 | 0.0223 | 0.0795 | 0.0014 | 0.0178 | 0.004 | 0.0022 | 0.14 | 0.8333 | 0.000002 | 305.8579 |
4 | BH 4 | 0.0170 | 0.1074 | 0.0031 | 0.0079 | 0.036 | 0.0042 | 0.12 | 1.2667 | 0.000006 | 224.5218 |
5 | BH 5 | 0.0301 | 0.0735 | 0.0017 | 0.0341 | 0.1600 | 0.0036 | 0.06 | 0.7667 | 0.000015 | 269.7245 |
6 | BH 6 | 0.0258 | 0.1509 | 0.0037 | 0.0253 | 0.0613 | 0.0012 | 0.14 | 1.6333 | 0.000008 | 128.8933 |
S/N . | Sample No. . | Contamination Factor (CF) . | PLI . | WQI . | |||||||
---|---|---|---|---|---|---|---|---|---|---|---|
. | . | . | . | . | . | . | . | ||||
1 | BH 1 | 0.0280 | 0.0966 | 0.0026 | 0.0085 | 0 | 0.0014 | 0 | 1.6333 | 0 | 544.4482 |
2 | BH 2 | 0.0161 | 0.1818 | 0.0049 | 0.0236 | 0.1773 | 0.0024 | 0 | 0.1067 | 0 | 38.00885 |
3 | BH 3 | 0.0223 | 0.0795 | 0.0014 | 0.0178 | 0.004 | 0.0022 | 0.14 | 0.8333 | 0.000002 | 305.8579 |
4 | BH 4 | 0.0170 | 0.1074 | 0.0031 | 0.0079 | 0.036 | 0.0042 | 0.12 | 1.2667 | 0.000006 | 224.5218 |
5 | BH 5 | 0.0301 | 0.0735 | 0.0017 | 0.0341 | 0.1600 | 0.0036 | 0.06 | 0.7667 | 0.000015 | 269.7245 |
6 | BH 6 | 0.0258 | 0.1509 | 0.0037 | 0.0253 | 0.0613 | 0.0012 | 0.14 | 1.6333 | 0.000008 | 128.8933 |
Pollution load index (PLI)
WQI
The WQI was determined for all the samples and the results (Table 2) and Figure 5 shows the variation of WQI across the study area. This index helps in the classification of the water samples to know its status and the rating was done according to Akakuru et al. (2022). BH 2 with a WQI value of 38.00885 was rated as being in the excellent class (<50), which implies that the water can be utilized for drinking, irrigation and industrial uses. The water sample from BH 6 was rated as poor (100–200), so it will useful for industrial and irrigation purposes. BH 4, and BH 5 were rated as very poor (200–300), which can be utilized for irrigation purposes. BH 1 with values greater than 300 (>300) was rated as unsuitable and thus needs proper treatment before any use.
SAR
The results in Table 1 were employed in estimating the SAR as presented in Table 3. Sodium is important in irrigation water as it can help improve soil structure, but will have a negative effect on plant growth and crop yield when in excess. Also, alkaline soils may be form when sodium combines with carbonates. The study reveals that SAR concentration varies from 0.41–2.78 with a mean of 1.47. Considering the classification of Todd (1980) and Raju et al. (2009), SAR values that are less than 10 (<100) indicate that all the water samples have excellent water quality for irrigation.
Sample No. . | SAR . | MH . | KR . | %Na . |
---|---|---|---|---|
BH 1 | 2.78 | 100.00 | 7.43 | 22.71 |
BH 2 | 1.15 | 8.28 | 0.68 | 13.71 |
BH 3 | 1.15 | 100.00 | 2.46 | 6.85 |
BH 4 | 1.91 | 100.00 | 2.95 | 25.73 |
BH 5 | 0.41 | 13.04 | 0.25 | 3.99 |
BH 6 | 1.43 | 11.54 | 1.40 | 11.57 |
Sample No. . | SAR . | MH . | KR . | %Na . |
---|---|---|---|---|
BH 1 | 2.78 | 100.00 | 7.43 | 22.71 |
BH 2 | 1.15 | 8.28 | 0.68 | 13.71 |
BH 3 | 1.15 | 100.00 | 2.46 | 6.85 |
BH 4 | 1.91 | 100.00 | 2.95 | 25.73 |
BH 5 | 0.41 | 13.04 | 0.25 | 3.99 |
BH 6 | 1.43 | 11.54 | 1.40 | 11.57 |
MH
Magnesium is important in irrigation water as it is essential in the formation of chlorophyll molecules in plant tissue and also in activation of specific enzymes. Availability of magnesium in soil depends on factors such as rock constituents, amount of weathering, climate of the area etc. The values of MH ranged from 8.28–100 with a mean of 55.48, according the rating of Khodapanah et al. (2009), BH 1, BH 3 and BH 4 have values greater than 50 (MH > 50) and consequently are not recommended for irrigation purposes.
KR
This index also helps in assessing the suitability of groundwater for irrigation purposes. The results in Table 3 show the values of KR ranging from 0.25–7.48 with a mean value of 2.53. BH 1, BH 3, BH 4 and BH 6 have values greater than 1 (>1), thus are rated as not suitable for irrigation purpose due to alkali hazard. BH 2 and BH 5 with values of 0.68 and 0.25 respectively are suitable for irrigation.
%Na
Sodium affects the soil by closing up the pores and this leads to poor water infiltration and wetting of the soil and can cause permeability problems. The %Na index is important in determining groundwater suitability for irrigation purpose. The results in Table 3 show %Na values ranged from 3.99–25.73% with a mean value of 14.09%. This implies that BH 2, BH 3, BH 5 and BH 6 are within the permissible category of excellent (<20%) while BH 1 and 4 are within the good class (20–40%) for irrigation (Khodapanah et al. 2009).
CONCLUSION
The analysis of physical and hydrogeochemical parameters of water samples was carried out within the study area and its environs. The study reveals the concentrations of the physical parameters from which water quality and irrigation indices like WQI, PLI, CF, SAR, MH, %Na and KR were estimated. The concentrations of physical and chemical parameters were within the WHO permissible limit for drinking water except BOD and COD which exceeded WHO standard in all the water samples, and , which also exceeded the WHO standard in sample BH 1. The observed DO values suggest oxic condition (DO 5). The order of abundance of the cations and anions is and respectively. Contamination factor reveal that , , , , have low concentration (<1) while is high (>1) in two of the samples. The values of PLI were low in all the water samples which signifies no pollution. The WQI reveal that water sample with value less than 50 (excellent class) as good for drinking, irrigation and industrial uses. The values of SARS estimated reveals that all the water samples have excellent water quality for irrigation. MH KR and %Na, based on their ratings, reveal the status of the suitability of the water samples for irrigation purpose. We can infer the chemistry of the sediments and the hydrogeologic units, which are controlled by different processes that affect the groundwater status of the area. The various plots displayed the variability of the concentration of the parameters. These indices can serve as tools for predicting the suitability of groundwater for drinking, irrigation and industrial purposes. It is recommended that future research work be carried out to consider and evaluate the concentration of heavy metals, salinity hazard, alkalinity, soluble sodium percentage, residual sodium bicarbonate and permeability index.
ACKNOWLEDGEMENTS
The authors are thankful to Tetfund for sponsoring this research.
DATA AVAILABILITY STATEMENT
All relevant data are included in the paper or its Supplementary Information.
CONFLICT OF INTEREST
The authors declare there is no conflict.