Occurrence and Impact of Heavy Metals on Groundwater Sources: A Case Study of Two Communities in Nasarawa State, Nigeria

Abstract

Heavy metals are major contaminants in groundwater, and they have potentials for toxicity even at low concentrations with health hazards. This led to the determination of heavy metal concentrations and evaluation of HMPI and MI of groundwater sources in Keffi and Karu to ascertain the suitability for domestic usage. Heavy metals, Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn, were determined using AAS. The results obtained showed that Cd, Cr and Pb had mean concentrations higher than the SON recommended limit. Statistical analyses at p < 0.05 showed that there were no significant differences between heavy metal contents in water from boreholes and wells in Keffi and Karu. HMPI were 77.33 and 92.08 for borehole and hand dug well water respectively in Keffi and 105.27 and 127.41 for borehole and hand dug well water respectively in Karu. The values from Keffi are lower than the critical value of 100, while those of Karu are slightly higher. MI for borehole and hand dug well waters was 0.564 and 0.606 respectively in Keffi and for Karu, the values were 0.634 and 0.723 respectively and are all less than 1. These suggest that the water sources are not affected with heavy metal pollution when compared to the water quality classification scheme adopted.

1. Introduction

One of the most important substances in the life of living organisms is water [1]. It is of very great value because of the roles it play in living organism: aid digestion, flushing of wastes from the body, transportation of nutrients, regulation of body temperature and maintenance of other bodily functions [2]. The establishment of stable human settlements, rural, semi-urban and urban areas, is dependent largely on the readily available portable water sources [3]. Over the decades, there has been an increased demand for water that is of good quality, and this could be attributed to ever increasing human population, urbanisation and industrialisation [3].

In developing countries, these increased demands for water lead to the use of any available water sources to meet the daily water need of inhabitants. The known sources of water are either surface water (rivers, dams, lakes, pond and a few others) or groundwater (boreholes, hand-dug wells and spring) [4]. The surface water sources are readily accessible, because to have access to the groundwater sources, energy in some forms would have to be expended and in some cases requires funds needed for digging. However, there are many settlements where the surface water sources are not available as well as the pipe-borne supply; therefore, the inhabitants are left with no option but to resort to groundwater sources for their daily water need. Groundwater forms a vital domestic and agricultural water sources in rural and urban communities of most developing countries, Nigeria inclusive [5]. Groundwater storage is better with the sedimentary aquifer compared to crystalline basement. Boreholes fail at a high rate in the basement and in areas with basement complex; hand-dug well is always the main source of water [6].

The source of groundwater is the water cycle, and the water is always stored in the aquifer beneath the earth surface. Water that falls as precipitation (rain or snow) flows along the surface of the ground, and it infiltrates into the ground of the surface and is stored in the spaces of soil pores and the fractures of rock formations as groundwater. Due to this reason, groundwater is always believed to be comparatively cleaner than surface water systems that receive contaminants directly [6].

In the recent past, the contamination of groundwater sources has become an issue of very serious environmental concern [7]. There is a vast range of contaminants that affect groundwater sources, and heavy metals are of a particular interest since they have potentials for toxicity even at low concentrations. Although some are essential mineral elements and very important to life (Fe, Cu, Zn and a host of others), at elevated levels, they could become deleterious with associated health risks [8]. Heavy metals are chemical elements, metals or metalloid with a specific gravity five times that of water and have potentials for toxicity. The major source of heavy metals in potable water is the contamination of groundwater and surface water sources [9]. Many heavy metals are natural constituents of the environment. However, elevated levels of these heavy metals in the environment could be attributed to the anthropogenic activities of man. Groundwater contamination could come from industrial sewage, proliferation of dumpsites for domestic wastes without due consideration to government rules, mining, agricultural run-off and a few other factors [9].

It is of utmost importance to assess the metal contents in water from either surface or groundwater sources. This is because even though the trace element could be very essential to animals and humans for biochemical activities, when present at levels higher than recommended limits, it could lead to some morphological disorders in humans, such as mutagenic effect, reduced growth, increased mortality and a host of others [10, 11]. The use of dumpsites as farmland is a common practice in urban and sub-urban centres in Nigeria because decayed and composted wastes enhance soil fertility [12]. These wastes often contain heavy metals in various forms and at different contamination levels. Some heavy metals like As, Cd, Hg and Pb, which are particularly hazardous to plants, animals and humans [13], could find their ways into these water bodies through leaching as well as runoff waters. Also, from farmlands that had agrochemicals and fertilisers applied on them, these agro-based products contain metals like Cu, Mg, Mn, Pb or Zn, which could eventually be found in groundwater through run-off and infiltration [14].

Heavy metals are given serious concern because they are not biodegradable, largely immobile in soil and tend to concentrate and persist for a long time in the environment [15]. Due to the non-biodegradable nature of heavy metals at elevated levels, they could easily undergo bioaccumulation. There is a bioaccumulation of chemical specie in a biological system when there is an increase in the concentration of specie in the biological system compared to its concentration naturally in the environment [16]. One of the easiest means by which metals get to living organism is through water and, if present at elevated levels, is associated with serious health risks. For instance, some are carcinogenic and could cause neurological disorder, liver and kidney dysfunctions and a lot of other serious health challenges; hence, there is the need to assess the metal contents of groundwater sources [17].

Several research works have been done within and outside the shores of Nigeria to assess the metal contents of groundwater sources. These include the evaluation of heavy metals in groundwater, South of Najaf, Iraq [4], the evaluation of heavy metals in groundwater around Keshere and its environs, upper Benue Trough, North-eastern Nigeria [18], the determination of heavy metals in borehole and hand-dug well in selected areas of Mubi, Adamawa state, Nigeria [9] and a host of others.

The government is solely responsible for the provision of potable water in Nasarawa State just like in almost all states in Nigeria, and in most cases, it is characterised by low productivity and few areas covered, and there is always inefficiency and ineffectiveness in the delivery. Most citizenry that do not benefit from the provisions by the government, therefore, depend on the available sources, groundwater (wells and boreholes) whose quality cannot be certified satisfactorily. And, as such, cases of water-associated health problems abound due to drinking and other domestic usage of water from these sources. This study is geared towards investigating the heavy metal contents in water from these sources in accordance with the requirements of the Standards Organisation of Nigeria (SON) [19] to ascertain the suitability of water from boreholes and hand-dug well in Keffi, Karu and their environs for domestic purpose.

2. Materials and methods

2.1 Study area

Keffi and Karu Local Government Areas (LGAs) are part of the 13 local government areas in Nasarawa State, Nigeria. The location of Nasarawa State on the World Map is latitude 8° 00′ to 8° 30′N and longitude 8° 30′ to 9° 00′E. The temperature of the study area could be described to be generally very warm with high humidity (Figure 1). There are two seasons in the area: dry season (October to March) and the rainy season (April to September). A high percentage of the population from the communities in these areas depends largely on groundwater sources (boreholes and hand-dug wells) for their daily water need. Then, others that reside in the headquarters of the local government areas rely on boreholes and deep hand-dug wells sank by individuals and the government for their daily water supply. Pipe-borne water supply is available in some places with epileptic operations. The communities used for this study are AgwanLambu/High Court, DadinKowa/Angwan Kwara, Yelwa and City centre all in Keffi and Uke, Auta-Balefi, Masaka, Ado/New Nyanya/Karu and Mararaba all in Karu Local Government Area.

Figure 1.

Map of Nasarawa State showing Keffi, Karu (study Areas) and other LGAs.

2.2 Sample collection, treatment and preservation

Samples were taken from boreholes and hand-dug wells in both Keffi and Karu Local Government Areas. Samples of water were collected two times in a day for a period of two weeks. Variation in the day and time samples were collected was observed in order to take care of changes that might occur at irregular intervals at the point of collection. Samples of water from borehole were collected from the taps bringing water from the borehole, and those of the hand-dug wells were collected with the use of a fetcher. All the samples collected were stored in clean 1500-cm³ white plastic containers that had been properly washed by soaking overnight in 0.1-mol/dm³ nitric acid solution and washed with soap solution. They were then rinsed with deionised water and concentrated nitric acid before being filled with deionised water to the locations designated for sampling. The containers were then emptied and rinsed with the samples to be collected severally before the sample collection proper. The sample containers were covered (air tight), properly labelled and immediately transported to the laboratory awaiting digestion and metal analysis [20].

2.3 Digestion of water samples for metal analysis

Water sample, 250 cm³, was measured into an evaporating dish and concentrated HNO₃ measuring 5.0 cm³ was added. The mixture was digested for about 1 hour on a heating mantle in a fume cupboard at temperatures of 90–95°C, and the quantity was reduced to 25 cm³ with a colour that is characteristics of a complete digestion. The clear digest was brought down and allowed to cool. It was filtered using Whatman filter paper no. 1 into a 50-cm³ volumetric flask that had been washed with an acid and properly rinsed with deionised water. The filtrate was made up to the mark with deionised water and kept awaiting metal analysis with atomic absorption spectrophotometer (AAS) [21].

2.4 Metal analysis

Heavy metals such as Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn in the digested water samples were determined using atomic absorption spectrophotometer (AAS) (ICE 3000AA0213410.VI.30 System).

2.5 Statistical analysis

Data obtained from the study were subjected to statistical tools such as mean, standard deviation, and correlation using SPSS.

2.6 Heavy metal pollution index (HMPI)

Countries, institutions and organisations have always provided recommended standard limits for different heavy metals in water for the purpose of being able to ascertain the quality of water with respect to individual metal contents. However, this does not give any information on the pollution level of metals in water with regard to all the metals that are detectable [18]. Heavy metal pollution index (HMPI) is a technique that determines the quality of water by providing information on the influence of each detectable metal on the overall quality of water. The values for ranking are 0–1, and the importance of each quality considerations is inversely proportional to the standard permissible limits [18].

The stages involved in the calculation of unit weight of the ith parameter, the calculation of the quality rating for each parameter and the addition of these sub-indices in the overall index are as follows:

$$\mathit{Wi}=\frac{k}{\mathit{Si}}$$E1

where Wi is the unit weight for the ith parameter, Si is the recommended standard limit for the ith parameter and k is the proportionality constant. The quality rating for individual parameter Qi can be evaluated as follows:

$$\mathit{Qi}=\frac{100\times \mathit{Mi}}{\mathit{Si}}$$E2

where Qi is the sub-index of the ith parameter, Mi is the concentration of the ith heavy metal, Si is the recommended standard limit for the ith parameter and 100 is the critical pollution index value

$$\text{HMPI}=\frac{\sum \left(\mathit{Qi}\times \mathit{Wi}\right)}{\sum \mathit{Wi}}$$E3

where HMPI is the heavy metal pollution index, Qi is the sub-index of the ith parameter and Wi is the unit weight for the ith parameter [18].

2.7 Metal index (MI)

Metal index when evaluated for drinking water gives information of the likely additive effects of all the detectable heavy metals in water on the health of humans and that greatly aid the determination of the overall quality of water. MI can be computed as follows:

$$\mathrm{MI}=\frac{\mathit{Mi}}{\mathit{Si}}$$E4

where MI is the metal index, Mi is the observed metal level in water and Si is the highest recommended permissible limit. MI is a tool used to determine the quality and suitability of water that is meant for drinking. The classification of water quality using metal index are; <3.0 very pure, 0.3–1.0 pure, 1.0–2.0 slightly affected, 2.0–4.0 moderately affected, 4.0–6.0 strongly affected and >6.0 seriously affected [18].

3. Results and discussion

Table 1 shows the sample locations in the study area, Tables 2 and 3 show the concentrations of heavy metals in samples of water from boreholes and hand-dug wells, respectively, in Keffi and Tables 4 and 5 show the concentrations of heavy metals in samples of water from boreholes and hand-dug wells, respectively, in Karu.

Location		Borehole water sample	Hand-dug well water sample
Keffi	Angwan Lambu/High Court	S1	S6
	Dadin Kowa/ Angwan Kwara	S2	S7
	Tudun Amama	S3	S8
	Yelwa	S4	S9
	City Centre	S5	S10
Karu	Uke	S11	S16
	AutaBalefi	S12	S17
	Masaka	S13	S18
	Ado/New Nyanya/Karu	S14	S19
	Mararaba	S15	S20

Table 1.

Sampling locations in Keffi and Karu, Nasarawa State, Nigeria indicating sample numbers.

Location
Parameters	S1	S2	S3	S4	S5	Mean	SON Standard [19]
Cd	0.061	0.032	0.037	0.035	0.032	0.039	0.003
Cr	0.050	0.045	0.052	0.048	0.056	0.050	0.050
Cu	ND	ND	ND	ND	ND	-	1.00
Fe	0.097	0.176	0.096	0.117	0.084	0.114	0.30
Mn	0.056	0.054	0.049	0.058	0.055	0.054	0.200
Ni	ND	ND	ND	ND	ND	-	0.020
Pb	0.015	0.009	0.012	0.005	0.003	0.009	0.01
Zn	0.090	0.184	0.089	0.078	0.084	0.105	3.00

Table 2.

Mean values of heavy metal contents in borehole water samples in Keffi LGA.

Location
Parameters	S6	S7	S8	S9	S10	Mean	SON Standard [19]
Cd	0.035	0.046	0.037	0.037	0.044	0.039	0.003
Cr	0.050	0.056	0.064	0.049	0.055	0.055	0.050
Cu	ND	ND	ND	ND	ND	-	1.00
Fe	0.067	0.075	0.099	0.086	0.247	0.115	0.30
Mn	0.056	0.062	0.057	0.049	0.065	0.058	0.200
Ni	ND	ND	ND	ND	ND	-	0.020
Pb	0.015	0.012	0.014	0.011	0.009	0.012	0.01
Zn	0.105	0.067	0.099	0.086	0.247	0.121	3.00

Table 3.

Mean values of heavy metal contents in hand-dug well water samples in Keffi LGA.

Location
Parameters	S11	S12	S13	S14	S15	Mean	SON Standard [19]
Cd	0.056	0.033	0.041	0.035	0.022	0.037	0.030
Cr	0.05	0.045	0.052	0.048	0.056	0.051	0.050
Cu	0.055	0.059	0.054	0.061	0.065	0.059	1.00
Fe	0.097	0.186	0.096	0.119	0.084	0.116	0.30
Mn	0.056	0.054	0.049	0.058	0.058	0.055	0.200
Ni	0.018	0.019	0.017	0.016	0.019	0.018	0.020
Pb	0.018	0.009	0.016	0.005	0.008	0.011	0.01
Zn	0.090	0.184	0.089	0.078	0.094	0.107	3.00

Table 4.

Mean value of heavy metal contents in borehole water samples in Karu LGA.

Location
Parameters	S16	S17	S18	S19	S20	Mean	SON Standard [19]
Cd	0.039	0.046	0.036	0.039	0.041	0.040	0.03
Cr	0.057	0.065	0.064	0.049	0.055	0.058	0.050
Cu	0.055	0.065	0.054	0.06	0.075	0.062	1.00
Fe	0.067	0.075	0.012	0.086	0.257	0.099	0.30
Mn	0.046	0.062	0.075	0.051	0.068	0.060	0.200
Ni	0.019	0.021	0.017	0.018	0.019	0.019	0.020
Pb	0.015	0.012	0.014	0.017	0.019	0.015	0.01
Zn	0.109	0.065	0.0959	0.106	0.247	0.125	3.00

Table 5.

Mean value of heavy metal contents in hand-dug well water samples in Karu LGA.

The mean values of cadmium in water samples from boreholes and hand-dug wells in Keffi were 0.039 and 0.039 mg/L, respectively, while for Karu the mean cadmium values were 0.037 and 0.04 mg/L, respectively. All these values are higher than the range of 0.00–0.011 mg/L reported for cadmium in Azare groundwater system [22] but are lower than the mean value of 0.08 mg/L of cadmium in water reported for stream water in Bauchi metropolis [23]. But the values are higher than the value of 0.003 mg/L recommended as the acceptable permissible limits by the SON [19] for cadmium in water that can be used domestically and industrially. Cadmium in water may be due to the mineralisation of cassiterite and also as a result of the use of insecticides, fertilisers and pesticides for farming and could be leached into groundwater systems. It could also come from wastes and effluents generated domestically like used batteries and other waste materials and eventually find its way into the water systems. High intake of cadmium via water is associated with toxicity to the kidney [19].

The mean values of chromium in water samples from boreholes and hand-dug wells in Keffi were 0.05 and 0.055 mg/L, respectively, while for Karu the mean cadmium values were 0.051 and 0.058 mg/L, respectively. All these values are within the range of 0.00–0.29 mg/L for chromium in boreholes and hand-dug well in both dry and wet seasons reported for selected rivers in Nasarawa State [24]. These values are lower than majority of the mean values for water samples from three different streams that had not detected, 0.93, 1.58 and 0.65, 0.49, 1.12 mg/L for dry and wet seasons, respectively, reported for groundwater sources in Okene Local Government Area, Kogi State [25]. Apart from the mean value of chromium in water from boreholes in Keffi, all the other values are slightly higher than the value of 0.05 mg/L recommended as the acceptable permissible limits by the SON [19] for chromium in water that can be used domestically and industrially. Chromium comes from wastes and effluents generated domestically. The deficiency of chromium causes impaired insulin function, hence increased insulin secretion and the risk of diabetes mellitus. High intake of chromium that is more than the recommended standards causes cancer [19].

Copper was not detected in water samples from both boreholes and hand-dug wells in Keffi but was, however, detected in boreholes and hand-dug wells in Karu and had mean concentrations of 0.59 and 0.62 mg/L, respectively. These values are higher than the mean value of 0.51 mg/L for copper in water reported for water sources in Bauchi metropolis [23] as well as the mean value of 0.1669 ± 0.1414 for copper in the groundwater systems of Azare [22]. The mean values from this study are lower than the value of 1.00 mg/L recommended as the permissible tolerable limits, and a concentration higher than this limit is always associated with gastrointestinal disorder [19].

The mean values of iron in water samples from boreholes and hand-dug wells in Keffi were 0.114 and 0.115 mg/L, respectively, while for Karu the mean iron values were 0.116 and 0.099 mg/L, respectively. The mean values from this study are lower than the value of 0.30 mg/L recommended as the permissible tolerable limits [19]. Iron is one of the components of haemoglobin responsible for the transport of oxygen in the body. It also aids in the oxidation of carbohydrates, proteins and fats as well as helping to prevent anaemia [26]. The concentration of iron, which is more than the acceptable limits, supports iron-dependent bacteria to cause deterioration in water quality [27]. Iron sources are domestically generated wastes, runoffs and probably the geological formations of the location under investigation. The level of iron can be reduced or removed completely from water through aeration [28].

The mean values of manganese in water samples from boreholes and hand-dug wells in Keffi were 0.054 and 0.058 mg/L, respectively, while for Karu the mean iron values were 0.055 and 0.060 mg/L, respectively. These values are lower than the mean values recorded for boreholes and hand-dug wells in dry and wet seasons, which were 0.42 mg/L for boreholes and 0.34 mg/L for hand-dug wells in dry season and 0.36 mg/L fore boreholes and 0.44 mg/L for hand-dug wells in wet season [25]. The values are also lower than 0.34 mg/L for manganese in water reported for water sources in Bauchi metropolis [23]. The mean values from this study are lower than the value of 0.20 mg/L recommended as the permissible tolerable limits [19]. Manganese is found in the environment due to the activities and from domestic wastes. High level of manganese in water above the recommended tolerable limits causes neurological disorder [19].

Nickel was not detected in water samples from both boreholes and hand-dug wells in Keffi but was, however, detected in boreholes and hand-dug wells in Karu and had mean concentrations of 0.018 and 0.019 mg/L, respectively. These mean values are slightly lower than mean value of 0.02 mg/L for nickel in water reported for water sources in the metropolis of Bauchi, Nigeria [23]. The mean values from this study are lower than the value of 0.020 mg/L recommended as the permissible tolerable limits, and a level higher than this is associated with possible carcinogenic effects [19]. Nickel comes from activities that originate from mechanic workshops, dumpsites and fertiliser-rich sewage sludge [23].

The mean values of lead in water samples from boreholes and hand-dug wells in Keffi were 0.009 and 0.012 mg/L, respectively, while for Karu the mean iron values were 0.011 and 0.015 mg/L, respectively. All these values are lower than the mean concentration of lead, 0.1100 ± 0.1097 mg/L, in groundwater systems of Azare [22] as well as the mean concentration of 0.048 mg/L for lead in water sources [23]. The concentrations of lead from this study are all higher than the recommended tolerable limits of 0.01 mg/L except for lead level in boreholes in Keffi, and anything above this limit can cause cancer, interfere with vitamin D metabolism, affect mental development in infants and is toxic to the central and peripheral nervous system. Sources of lead in the environment are mechanic, battery charger workshops as well as car wash spots and wastes generated domestically.

The mean concentrations of zinc in water samples from boreholes and hand-dug wells in Keffi were 0.105 and 0.121 mg/L, respectively, while for Karu the mean iron values were 0.107 and 0.125 mg/L, respectively. These mean concentrations are within the same range with the mean concentrations for zinc in boreholes from three different locations, which are 0.10, 0.11 and 0.12 mg/L reported for groundwater sources in Benin City, Edo State and Agbor, Delta State, all in Nigeria [20]. The mean values from this current work are lower than the recommended permissible limits of 3.00 mg/L [19].

Tables 6 and 7 shows the results of statistical analysis for test of significance between heavy metal contents of borehole water samples and hand-dug well water samples from Keffi Local Government Area and Karu Local Government Area, respectively. From the results shown, there were no significant differences between all the heavy metal contents in borehole and hand-dug well in both Keffi and Karu. The p-values for all heavy metal contents did not conform to p < 0.05, with the implication that for all the parameters, there were no significant differences between the borehole water samples and the hand-dug well water samples from Keffi Local Government Area and Karu Local Government Area. This could be attributed to the fact that in each location or study area, the geologic formation of the soil is the same for places where boreholes or hand-dug well had been drilled.

Metals	Borehole water (Mean of mean ± SD) mg/L	Well water (Mean of mean ± SD) mg/L	t-value	p-value
Cd	0.039 ± 0.122	0.039 ± 0.005	–0.068	0.948
Cr	0.050 ± 0.004	0.055 ± 0.006	–1.414	0.195
Cu	0.000 ± 0.000	0.000 ± 0.000	–	–
Fe	0.114 ± 0.037	0.115 ± 0.075	–0.021	0.983
Mn	0.054 ± 0.003	0.058 ± 0.006	–1.086	0.309
Ni	0.000 ± 0.000	0.000 ± 0.000	–	–
Pb	0.009 ± 0.005	0.012 ± 0.002	–1.390	0.202
Zn	0.105 ± 0.044	0.121 ± 0.072	–0.417	0.687

Table 6.

Heavy metals in borehole and well water samples in Keffi LGA (p < 0.05).

Metals	Borehole Water; (Mean of mean ± SD) mg/L	Well Water; (Mean of mean ± SD) mg/L	t-value	p-value
Cd	0.037±0.012	0.040 ± 0.004	–0.482	0.643
Cr	0.051 ±0.004	0.058 ± 0.007	–2.229	0.056
Cu	0.059 ± 0.005	0.062 ± 0.009	–0.692	0.508
Fe	0.116 ± 0.378	0.099 ± 0.093	1.093	0.306
Mn	0.055 ± 0.004	0.060 ± 0.012	–0.966	0.362
Ni	0.018 ± 0.001	0.019 ± 0.002	–1.132	0.290
Pb	0.011± 0.006	0.015 ± 0.003	–1.524	0.166
Zn	0.107 ± 0.043	0.125 ± 0.071	–0.475	0.648

Table 7.

Heavy metals in borehole and well water samples in Karu LGA (p < 0.05).

Table 8 shows the mean HMPI and MI of water from Keffi and Karu Local Government Areas. HMPI was used in the characterisation of water from boreholes and hand-dug wells from Keffi and Karu Local Government Areas. The characterisation gave values that were compared with the critical values to assess the extent of heavy metal pollution [18]. The mean HMPI values calculated were 77.33 and 92.08 for borehole water and hand-dug well water, respectively, in Keffi and 105.27 and 127.41 for borehole water and hand-dug well water, respectively, in Karu. The values from Keffi are lower than the critical value of 100, while those of Karu are slightly higher. Higher values are indication of pollution of water from the Karu. The discrepancy could be attributed to the fact that some parameters, such as Cu and Ni, were not detected in water samples from Keffi but were detected in the ones from Karu. The HMPI for both water sources is high, and it signifies that the source of the contaminants could be infiltration of runoffs from dumpsites of domestic wastes.

Parameters	Keffi		Karu
	BHW	HDWW	BHW	HDWW
HMPI	77.33	92.08	105.27	127.41
MI	0.564	0.606	0.634	0.723

Table 8.

HMPI and MI of water samples from Keffi and Karu LGAs.

BHW: Borehole water; HDWW: Hand-dug well water; HMPI: Heavy metal pollution index; MI: Metal index.

MI values for borehole and hand-dug well waters were 0.564 and 0.606, respectively, in Keffi, and for Karu the values were 0.634 and 0.723, respectively. These values, however, suggest that the water sources from the study area are pure and not affected with heavy metal pollution when compared to the water quality classification scheme adopted [18].

4. Conclusion

Water is very important in the lives of humans and other living organisms, and accessibility and availability of this water that is of good quality is always a serious problem. This informed the research to ascertain the suitability of water from boreholes and hand-dug wells in the study area for domestic and industrial purposes.

Results of metal analysis for all the water samples from the study areas showed that cadmium, chromium and lead had mean concentrations higher than the recommended tolerable limits prescribed by regulatory bodies, while all the other metals studied had mean values lower than the recommended concentrations. The statistical analyses done at 95% confidence limit (p < 0.05) showed that there were no significant differences between heavy metal contents in water samples from boreholes and wells from Keffi and Karu. HMPI evaluated for the water samples revealed that Keffi water sources were not polluted, but the Karu ones were slightly polluted. However, the MI evaluated for the samples revealed that groundwater sources in Keffi and Karu are pure and not affected by heavy metals.