Assessment of Some Physicochemical Parameters and Heavy Metals in Hand-Dug Well Water Samples of Kafta Humera Woreda, Tigray, Ethiopia

Groundwater is one of the most important sources of drinking water in Kafta Humera Woreda; hence, it is important to assess the quality of these water sources. The aim of this study was to assess the levels of some physicochemical parameters and heavy metals in hand-dug well water sources of Kafta Humera Woreda. The results showed that the physicochemical concentrations of the hand-dug well water samples were given as follows: temperature, 27.67 ± 0.15 to 28.30 ± 0.25°C; pH, 6.90 ± 0.33 to 8.20 ± 0.36; dissolved oxygen, 5.60 ± 0.06 to 6.2 ± 0.04 mg/L; turbidity, 1.67 ± 0.02 to 1.89 ± 0.03 NTU; EC, 148.50 ± 0.89 to 932.00 ± 0.98 μS/cm; TDS, 105.80 ± 0.62 to 664.28 ± 0.70 mg/L; total hardness, 71.80 ± 3.05 to 295.30 ± 2.38 mg/L; total alkalinity, 75 ± 5.0 to 215 ± 5.0 mg/L; calcium, 12.02 ± 0.82 to 75.88 ± 0.93 mg/L; magnesium, 9.80 ± 0.80 to 25.70 ± 0.17 mg/L; potassium, 0.130 ± 0.003 to 0.86 ± 0.04 mg/L; sodium, 2.20 ± 0.16 to 12.75 ± 0.87 mg/L; chloride, 12.86 ± 0.02 to 42.72 ± 0.20 mg/L; sulfate, 17.24 ± 0.96 to 118.67 ± 0.46 mg/L; phosphate, 0.018 ± 0.005 to 0.020 ± 0.002 mg/L; and nitrate, 1.86 ± 0.03 to 5.43 ± 0.06 mg/L. Generally, the concentrations of most physicochemical parameters of the hand-dug well water samples of Kafta Humera Woreda were within the permissible limit of World Health Organization and Ethiopian Standard Agency guideline for drinking water. The statistical Pearson's correlation analysis on the water quality parameters revealed that all parameters are more or less correlated with each other. Electrical conductivity and total dissolved solids of the water samples were found to be significantly correlated with total hardness (r = 0.989), total alkalinity (r = 0.827), calcium (r = 0.988), magnesium (r = 0.881), sodium (r = 0.995), potassium(r = 0.996), chloride (r = 0.998), sulfate (r = 1), and nitrate ions (r = 0.972). Out of the selected seven heavy metals, Fe, Cu, Zn, Mn, Cr, Cd, and Pb, only iron was detected in all water samples and its concentration was above the permissible limit of WHO and ESA for drinking water. Therefore, the government should adopt some treatment technologies such as sedimentation and aeration to minimize the concentration of iron for safe drinking the water to the community of Kafta Humera Woreda.


Introduction
Water is one of the most important compounds of the ecosystem, and all living organisms on Earth need water for their survival and growth. It is also used for drinking, cooking, agricultural activities, and industrial activities; transportation and recreation are among the most uses of water [1]. Water can be obtained from surface water sources such as freshwater, lakes, rivers, streams, and groundwater sources such as hand-dug well and borehole water. Groundwater is a major source of water for domestic use in both urban and rural areas of the world. It contains over 90% of the freshwater resources and it is an important reserve of good quality water [2]. Groundwater quality has become an important water resources issue due to rapid increase of population, rapid industrialization, unplanned urbanization, and too much use of fertilizers and pesticides in agriculture [3]. Good quality of water is essential for life, but the occurrence of physicochemical parameters and heavy metals above the permissible standards make it unsafe for drinking.
e quality of drinking water should be checked at regular time interval because due to the use of contaminated drinking water, human population suffers from a variety of waterborne diseases [1]. e majorities of the populations in developing countries are inadequately supplied with potable water and are thus bound to use water from sources like shallow wells and boreholes that have high potential of contamination and provide the unsafe water for domestic and drinking purposes [4]. e availability and amount of freshwater continue to decrease from time to time in Africa. In Sub-Saharan African countries, the requirements of water for domestic and industrial purposes are usually not met.
e natural chemical quality of groundwater is generally good, but at higher concentration a number of constituents can cause problems for water use [5].
In Ethiopia, the most common source of drinking water used to supply major urban and rural communities is obtained from hand-dug wells, boreholes, and shallow wells and covers about 85% of the public supply [6]. Hand-dug well water source is the major source of water for drinking and other domestic purposes for the community of Kafta Humera community (Kunama Adigoshu, Hagere selam, May Woyni, and Habesha Adigoshu. However, the physicochemical parameter and heavy metal concentrations of the hand-dug well water sources have not been tested before in the study area and to compare the results with the minimum requirement of World Health Organization (WHO) and the Ethiopian Standard Agency (ESA). erefore, the aim of this study is to assess the levels of some physicochemical parameter and heavy metal concentrations of hand-dug well water samples of Kafta Humera Woreda, Tigray, Ethiopia.

Description of the Study Area.
Water samples were collected from Western Zone of Tigray Region, Kafta Humera Woreda specifically Kunama Adigoshu, Hagere Selam, May Woyni, and Habesha Adigoshu Kebelles (Figure 1). It is located 587 km Northwest of Mekelle, the capital city of Tigray Region, bordering Sudan on the West and Eritrea on the North. Geographically, the area lies between 13°40′ N and 14°27′ N and between 36°27′ E and 37°32′ E with an elevation varying from 550 m to 2800 m above sea level. e annual rainfall in the area ranges from 500 to 1500 mm. e relative humidity is highest during the months of rain (June-July) and lowest at the end of the dry season in April [7]. Based on the 2007 national census conducted by the central statistical agency of Ethiopia, the Woreda has a total population of 92,167 [8].

Sampling and Preservation.
Water samples were collected from four sampling sites Kafta Humera Woreda (Kunama Adigoshu, Hagreselam, May Woyni, and Habesha Adigoshu) on May 2019. Simple random sampling method was employed on selecting the four hand-dug wells' water from each site of the study area. Water samples were collected in 2 L polyethylene plastic bottle previously washed with detergents, acidified with 5% HNO 3 for 24 h, rinsed twice with distilled water, and then finally rinsed with sample water three times before filling the sample water [9]. Samples from the wells were obtained by direct immersion of plastic containers into the reservoir handled by 10 m rope and the fetched water was poured immediately into the polyethylene plastic sample containers. Finally, all the collected samples from the study area were labeled, preserved in ice box at temperature of 4 to 10°C to avoid any contamination, and transported to Mekelle University, College of Natural and Computational Science, School of Geochemistry laboratory and Ezana Mining Analytical Laboratory Development P.L.C for analysis. Standard methods [10] were used for sample collection, handling, and preservation to ensure data quality and consistency.

Analysis of Physicochemical Parameters in the Water
Samples.
e water samples were analyzed for physicochemical parameters such as temperature, pH, turbidity, dissolved oxygen (DO), electrical conductivity (EC), total dissolved solids (TDS), total alkalinity, total hardness, calcium, magnesium, sodium, potassium, chlorine, sulfate, phosphate, and nitrate using standard analytical methods [11]. e pH and total dissolved solids were measured using pH meter (HI-99130, Italy). Electrical conductivity was measured using conductivity meter (JENWAY, multi-3410, UK). Turbidity was measured using turbidimeter (AL 250T-IR, Germany). e temperature of the water samples was measured on-site using mercury thermometer. Dissolved oxygen was determined using multi parameter (Multi-3410, Germany). e total alkalinity was determined using titrimetric method. Total hardness, calcium, and magnesium hardness were determined using EDTA titrimetric method. Chloride concentration was determined using argentometric titration method. e cations potassium and sodium were determined using flame photometry (JENWAY, PFP7, UK). e anions sulfate, phosphate, and nitrate were measured using UV-visible spectrophotometer (Lambda, CE1021, and Australia) [11].

Analysis of Heavy Metal in the Water Samples.
Exactly 50 mL of filtered aliquot water sample was pipetted into a digestion flask and mixed with 10 mL of 68% HNO 3 and then allowed to heat on hot plate for about six hours at a temperature of 80°C until the volume was reduced to onefifth of its original volume. e solution was cooled, filtered using Whatman number 41 filter paper, and then diluted to 100 mL volumetric flask using distilled water. e concentrations of heavy metals were determined using FAAS (AA240FC, Australia) at the analytical laboratory of Ezana Mining Development P.L.C, Mekelle, Ethiopia [12].

Data Analysis.
e physicochemical parameters and heavy metals were compared with WHO and Ethiopian Standard Agency (ESA) guidelines for drinking water. e relationships between the physicochemical parameters and heavy metals in the water samples were established using Pearson product correlation coefficient (r) at 1% level of significance. Data collected was statistically analyzed using Statistical Package for Social Sciences (SPSS version 23) [13].

Results and Discussion
e mean values of different selected physicochemical parameter and heavy metal concentrations are tabulated in Tables 1 and 2. 3.1. Temperature. Temperature measures the degree of coldness or hotness of a substance [14]. e temperature of the well water samples varied between 27.67°C and 28.30°C (Table 1). Similar studies conducted in selected Hand-Dug Wells for Water Quality in Ilesa Metropolis, Southwest Nigeria, scored temperature value of 28.04 ± 0.12°C [16]. e values of temperature for all well water samples were above the permissible limit of WHO for drinking water, 25°C [14]. ese higher water temperatures could be attributed to the environmental temperature as well as other climatic conditions prevailing in the study area at the time of collecting sample. Higher water temperature increases chemical reactions in the aquifer such as weathering of rocks which leads to the release of the chemical contaminants in water and decreases the level of dissolved in aquatic level [17]. Temperature has a negative correlation with dissolved oxygen (r � −0.708) and pH (r � −0.666), but positive correlation with turbidity (r � 0.892), electrical conductivity (r � 0.532), and TDS (r � 0.532) ( Table 3).

Turbidity.
Turbidity is a measure of the degree to which the water loses its transparency due to the presence of suspended particles. e turbidity values of the well water samples varied between 1.67 NTU and 1.89 NTU (Table 1)  International Journal of Analytical Chemistry samples had values which were within the permissible limit of WHO and ESA for drinking water below 5 NTU [14,15]. Similarly, the drinking water quality in the State of Perak, Malaysia, indicates that the turbidity of all the samples studied was below the maximum standard limit of 5NTU [18]. e occurrence of suspended soil, sediment, carbonbased substance, inorganic material, and other invisible living things enhances turbidity. Highly turbid water reduces light penetration to the wells, therefore affecting the level of photosynthesis aquatic plants. is increasing in water temperature is due to absorption of sunlight [19]. Turbidity has a significant negative correlation with dissolved oxygen (r � −0.867) at p < 0.01 (Table 3).

Electrical Conductivity.
Conductivity is a measure of the conducting ability of water and it is determined by the presence of ionic species in the water. Electrical conductivity value for all the sampling sites varied from 148.5 to 932 μS/ cm (Table 1). e measured EC value indicates that all examined water samples had values which were within the permissible limit of WHO 750 μS/cm and ESA 1500 μS/cm for drinking water except Kunama Adigoshu well water source in WHO [14,15].
ese results are higher in conductivity than the average conductivity value of the drinking water in the State of Perak, Malaysia, which is 102.1 μS/cm [18]. e presence of a slightly high value of electrical conductivity in the water sample shows that contaminations due to dissolve ions are high, because electrical conductivity is directly proportional to the total dissolved solids. is may be due to the soil type and geology of the study area or the wastes entering from the surrounding water sources [20]. Electrical conductivity shows significant correlation with ten parameters such as sulfate ion and TDS (r � 1), total hardness (r � 0.989), total alkalinity (r � 0.827), calcium (r � 0.988), magnesium (r � 0.881), potassium (r � 0.996), sodium (r � 0.995), chloride (r � 0.998), and nitrate ions (r � 0.972) at p < 0.01. is shows that the presence of these ions in dissolved form in water can increase the electrical conductivity of water (Table 3).

Total Dissolved Solids.
Total dissolved solids are the amount of mobile charged ions, including minerals, salts, or dissolved metals in a given volume of water in mg/L. e mean total dissolved solids (TDS) obtained from well water samples were from 105.80 mg/L to 664.30 mg/L ( Table 1). All the measured well water samples recorded TDS concentration     [14,15]. ese results are in agreement with a study conducted in India; total dissolved solids values ranged from 146 mg/L to 467 mg/L [21]. High level of TDS in groundwater may be due to dissolution of weathered materials from rock formation [22]. e occurrence of high values of TDS in certain well water samples could be unpleasant to consumers and may cause excessive scaling in water heaters, boilers, and household equipment [23]. Total dissolved solids show significant positive correlation with ten parameters such as sulfate ion and EC (r � 1), total hardness (r � 0.989), total alkalinity (r � 0.827), calcium (r � 0.988), magnesium (r � 0.881), potassium (r � 0.996), sodium (r � 0.995), chloride (r � 0.998), and nitrate ions (r � 0.972) at p < 0.01. is shows that the presence of these ions in dissolved form in water can increase the amount of total dissolved solids in water (Table 3).

pH
. pH values of the well water samples varied between 6.9 ± 0.32 and 8.2 ± 0 36 ( Table 1). All the wells recorded pH values within the acceptable limit of WHO and ESA standards 6.5-8.5 [14,15]. Similar results were recorded from groundwater sources of Dire Dawa City, Eastern Ethiopia, which were within the permissible pH limits (6.5-8.5) [24]. e pH has a negative significant correlation with turbidity (r � -0.848), but strong positive correlation with dissolved oxygen (r � 0.869) value at p < 0.01 (Table 3).

Dissolved Oxygen.
Dissolved oxygen is an important water quality parameter and it is an indicator of water contamination. e small amount of dissolved oxygen in water indicates the microbial contamination or corrosion of chemical substances in the aquifer [25]. e dissolved oxygen values of the well water samples varied between 5.6 mg/L and 6.2 mg/L ( Table 1). From the analyzed result, all well water samples recorded dissolved oxygen values within the acceptable limit of WHO standard for drinking water, 5-7 mg/L [14]. ese results are similar to a study conducted in groundwater around Singrauli Coalfield Areas, Singrauli district of Madhya Pradesh (India); it varies from 4.98 to 5.72 mg/L [21]. e level of dissolved oxygen in natural water highly reduced with increasing of water temperature and high organic concentrations as a result of increased decomposer activities [26].

Total Alkalinity.
Alkalinity is a measure of the ability of water to neutralize acids and it mainly occurs due to the presence of carbonates and bicarbonates in the water . e concentrations of total alkalinity in the well water samples varied between 75 mg/L and 215 mg/L (Table 1). e measured values of total alkalinity in all well water samples were above the permissible limit of WHO (120 mg/L) for drinking water, except Hagere Selam well water sample [14]. However, the total alkalinity of all well water samples was within the permissible limit of ESA 200 mg/L [15]. ese results are in line with a study conducted in Greece where water alkalinity varied from 23.56 to 267.00 mg/L [27]. Total alkalinity has a positive significant correlation with calcium (r � 0.78), magnesium (r � 0.887), sodium (r � 0.813), potassium (r � 0.829), chloride (r � 0.805), and sulfate(r � 0.838) at p < 0.01. is indicates that the presence of these ions in dissolved form in water can increase the amount of total alkalinity of water (Table 3).

Total Hardness.
Hardness of water is caused by the presence of dissolved polyvalent metallic ions, predominantly calcium ions (Ca 2+ ) and magnesium ions (Mg 2+ ). e values of total hardness concentrations recorded in the well water samples varied between 71.80 mg/L and 295.33 mg/L ( Table 1). ese amounts of total hardness concentrations are within the maximum allowable limit of WHO and ESA for drinking water 300 mg/L [14,15]. Higher water hardness concentration in groundwater may be due to the dissolution rocks containing gypsum and dolomite which are responsible for water hardness [27]. Similar results were observed in Guya Village and its surrounding area, Tigray, Northern Ethiopia; hardness values varied from 170.00 to 327.50 mg/L [28]. Hardness has a significant positive correlation with calcium (r � 0.978), magnesium (r � 0.939), sodium (r � 0.985), potassium (r � 0.984), chloride ion (r � 0.981), sulfate ion (r � 0.992), and nitrate ion (r � 0.937) at p < 0.01 (Table 3). is implies that the presence of these ions in water may have a direct effect on hardness values. e hardness observed in the hand-dug well water samples of the study area may be permanent hardness, because it has a strong positive correlation with permanent hardness causing ions such as chloride, sulfate, and nitrate salts.

Calcium and Magnesium
Ion. Calcium and magnesium ions are the major constituents of various types of rock and they are the most common constituents present in natural waters ranging from zero to several hundred mg/L [29]. e highest calcium amount (75.88 mg/L) of the well water was recorded at Kunama Adigoshu whereas the lowest value (12.02 mg/L) was found in Hagere Selam well water sample ( Table 1). All the wells recorded calcium ions within the acceptable limit of WHO and ESA standard for drinking water, 100 mg/L [14,15]. Calcium ion (Ca 2+ ) can occur naturally in groundwater through the dissolution of carbonate minerals and the decomposition of the sulfate, phosphate, and silicate minerals. High calcium concentrations in water may lead to the formation of solid scales in pipes and kitchen utensils and increased soap consumption [30]. e concentration of magnesium ions in the wells varied between 9.80 mg/L and 25.70 mg/L (Table 1). From the analyzed result, all the well water samples recorded magnesium ions within the permissible limit of WHO and ESA constants, 50 mg/L, for drinking water [14,15]. e main sources of magnesium in the underground water sampled may be attributed to geological sources such as dolomite and other magnesium containing compounds in sediments and soils of the water samples [18]. Calcium and magnesium have a significant positive correlation with potassium, sodium, chloride, sulfate, and nitrate ions ( Table 3).

Sodium and Potassium Ion.
e natural source of sodium and potassium in groundwater was from the weathering of rocks, but the elevated quantities in contaminated water may be attributed to the release of waste water [23]. e amount of sodium ions in well water samples varied between 2.20 mg/L and 12.75 mg/L (Table 1). e amount of sodium recorded in all well water samples was below the maximum permissible limit of WHO and ESA for drinking water, 200 mg/L [14,15]. e potassium levels recorded in the study areas were very low ranging from 0.13 mg/L to 0.86 mg/L (Table 1). e concentration of potassium obtained from all well water samples was far below the maximum permissible limit of WHO and ESA constant, 10 mg/L, for drinking water [14,15]. Similar results were recorded in the groundwater of Dire Dawa City, Eastern Ethiopia, concentration of sodium (7.31 mg/L-74.94 mg/L) and potassium (0.55 mg/L-3.33 mg/L) [24]. Sodium shows a significant positive relationship with chloride (r � 0. 994), sulfate (r � 0.996) and nitrate (r � 0.968) values. Potassium value has a positive strong correlation with sodium (r � 0.987), chloride ion (r � 0.996), sulfate (r � 0.995), and nitrate ion (r � 0.971) at p < 0.01.

Chloride Ion.
Chlorides enter into surface and groundwater from both anthropogenic and natural sources such as from run-off wastes from human activities, discharges of wastewaters into water bodies, use of inorganic fertilizers, landfill leachates, and septic tank effluents [31]. e concentration of chloride ion in the well water samples varied between 12.86 mg/L and 42.72 mg/L (Table 1). e level of chloride ion recorded in all water samples was within permissible limit of WHO and ESA for drinking water, 250 mg/L [14,15]. ese slight variations in the concentrations might be due to different levels of chloride salts in the soil and sediments or a result of differences in degree of wastes entering into the hand-dug wells [32]. e findings of this study are similar to hand-dug wells in Hantebet Catchment, Tigray, and Northern Ethiopia, varying from 15.45 to 49.44 mg/L [33]. Chloride value has a positive strong correlation with sulfate ion (r � 0.997) and nitrate ion (r � 0.982).
is shows that other factors governing the loading of these ions may directly affect chloride distribution at p < 0.01.

Sulfate, Phosphate, and Nitrate Ions.
e concentration of sulfate ion in the well water samples varied between 17.24 mg/L and 118.67 mg/L (Table 1). From the analyzed result, the sulfate level of all well water samples was within the permissible limit of WHO and ESA for drinking water 250 mg/L [14,15]. e high sulfate content of some well water samples of the study area may be due to the presence of sulfate containing minerals such as gypsum (CaSO 4 ·2H 2 O) and anhydride (CaSO 4 ) in the sites [34]. Sulfate has a positive strong correlation value with nitrate (r � 0.966) at p < 0.01. e phosphate levels obtained in the well water samples of the sampling area were very low, ranging from 0.018 to 0.073 mg/L (Table 1). e concentrations of phosphate in all well water samples were within the permissible limit of WHO and ESA for drinking water, 2 mg/ L [14,15]. e low concentration of the phosphate in the well water samples might be due to the geology of the area [32]. e nitrate levels in the well water samples ranged from 1.86 to 5.43 mg/L ( Table 1). All the well water samples recorded nitrate ion concentration within the permissible limit of WHO and ESA for drinking water, 45 mg/L and 50 mg/L, respectively [14,15]. Nitrate level in groundwater may be attributed to the introduction of sewages of humans and animals from the surrounding of the well, because it is very close to human residents. Sulfate has a significant positive correlation with nitrate value (r � 0.966) at p < 0.01.

Iron.
Iron was the only heavy metal detected in all well water samples of the study area. e concentration of iron measured in all well water samples varied from 0.33 mg/L to 1.86 mg/L ( Table 2). From the analyzed result, all the well water samples had iron concentration above the permissible limit of WHO and ESA for drinking water, 0.3 mg/L [14,15]. e higher value of iron from the study areas could also be from the natural sources. is may be due to the weathering of minerals, soil type, and sediments which are iron-rich materials [32]. Iron may not pose any health hazards but gives a bitter taste to the water when present in large concentrations. People consuming water sources with high concentration of iron were suffering from taste, color, corrosion of plumbing systems, and liver diseases. However, those exposed to low concentration would be highly susceptible to anemia [34]. A similar study conducted in handdug wells of Ilaro and Aiyetoro, Ogun State, Southwestern Nigeria, showed ranges from 0.26 to 1.37 mg/L [35].
e elements of Cu, Zn, Mn, Cd, Pb, and Cr were below the detection limit in all hand-dug well water samples of the study area. erefore, these elements may not have an immediate threat to the health of individuals in the study area who drink this water.

Concluding remarks
e aim of this study was to assess the level of some physicochemical parameters and heavy metals of water samples from hand-dug well water sources of Kafta Humera Woreda, specifically, Kunama Adigoshu, Hagere Selam, May Woyni, and Habesha Adigoshu Kebelles, Tigray Region, Ethiopia. e results showed that the concentrations of most physicochemical parameters of the water samples, such as turbidity, pH, total hardness, total alkalinity, calcium, magnesium, potassium, sodium, chloride, sulfate, phosphate, and nitrate ions, were within the permissible limit of the World Health Organization and Ethiopian Standard Agency guideline for drinking water with the exceptions of some physicochemical parameters, such as temperature in all hand-dug wells, total dissolved solids, and electrical conductivity in Kunama Adigoshu hand-dug well water sample which was above the WHO permissible limit, but within the permissible limit of ESA for drinking water. e International Journal of Analytical Chemistry concentrations of total alkalinity were above the WHO permissible limit in all hand-dug well water samples except in Hagere Selam hand-dug well water source. Out of the selected seven heavy metals, Fe, Cu, Zn, Mn, Cr, Cd, and Pb, only iron (Fe) was detected in all water samples and its concentration was above the permissible limit of WHO and ESA for drinking water. Generally, the water quality of the four hand-dug well water samples was good with the exception of some physicochemical parameters and heavy metals. It is recommended to check the quality of the water sources regularly in the study area. is assessment of some physicochemical and heavy metal quality of water is necessary but not sufficient to determine its suitability for drinking purpose. As such, it is recommended that further research should be a study of other trace heavy metals like mercury, arsenic, and biological parameters to confirm the study reliability.
Data Availability e datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.

Conflicts of Interest
e authors declare no conflicts of interest.