Soil pH and EC
Soil pH in all sample sites was recorded slightly basic. Similar studies conduct in Addis Ababa, Accra (Ghana), Lagos (Nigeria), Maradi city (Niger Republic), and Adama (Ethiopia) solid waste disposal sites show slightly basic pH between 8.17 and 7.37 in the nearby dump sites. It might be due to soil with the high metallic burden (Beyene and Banerjee, 2011; Osei et al., 2011; Abdourahamane et al., 2015 and Kebede et al., 2016 ).
The EC values of soil at Teppi town solid waste dump site indicate the significant presence of trace metal ions or ionizable materials in the soil (Anapuwa and Precious, 2015). Therefore, the sample site 60 meters far from the dump site was recorded the lower EC values may show the low trace metal ions or ionizable materials present in the soil compared to the other sample site. However, the mean values of EC found in this study were less compared to another similar study at Addis Ababa dump site (Beyene and Banerjee, 2011) and the difference may be due to the composition of the waste and the soil condition.
Heavy Metals in Soil Samples
The highest mean values of lead were observed in 10 meters and 30 meters far away from dump site recorded 57.56±0.26 and 52.12±0.02 mg/kg respectively and the values were higher than the limit prescribed by Ethiopian EPA (2003) standard (40 mg/kg). The movement of lead along the distance was favored by a slight nearest to the periphery of the dump site. It may be due to differences in soil pH and organic matter. According to Ashworth and Alloway (2008) and Shiva Kumar and Srikantaswamy (2014), it might be due to the presence of clay particle and organic matter. They are the major contributors towards sorbing of heavy metals. In addition, organic matter is important for the retention of metals by soil solids, thus decreasing mobility and bioavailability.
Ideriah et al. (2010) and Kebede et al. (2016) also substantiate this finding along the distance; however, the concentration was different compared to these study areas. This can be due to adsorption of lead on decomposed organic in sample sites near to dump site that restricts its mobility. In addition, it might be due to differences in the composition of the waste and the age of dump sites. However, the values of lead in this study area was lower compared to other studies done in Addis Ababa, India, and Maradi city (Niger Republic) dump sites which shows 17-852 mg/kg, 42.9-1833.5 mg/kg, and 79.133 mg/kg respectively (Beyene and Banerjee, 2011; Abdourahamane et al., 2015). It was higher than another study conducted by Kebede et al. ( 2016) in Adama city (Ethiopia) dump site which shows 1.033 mg/kg. The difference may be due to the quantity and constitute of municipal solid waste that contains lead contents such as electronic waste, lead batteries, lead-based paints, pipes, plastics were indiscriminately dumped in the dump sites.
The values of cadmium also revealed in all along the distance in sample stations with the lowest value was measured in the 60 meters far from the dump site and the highest value was recorded in 10 meters distance from the dump site showed 2.26±0.21 mg/kg. According to Haberhauer (2007), Ashworth and Alloway (2008), and Abu-Zahra et al. (2010) the highest concentrations with distance variation may be related with sorption of metals into the nature of soil with organic matter and pH. Thus, it was expected to find different concentration in the 10 meters and 30 meters far away from the periphery of the dump site.
The values of cadmium in10 meters, 30 meters, and 60 meters away from the dump site were higher than the limit prescribed by Ethiopian EPA (2003) standard (0.5 mg/kg). In addition, 10 meters and 30 meters away from the dump site were revealed higher values than the limit value prescribed by US EPA standard (1.4 mg/kg).
The finding was substantiated by other studies conducted in Adama and Addis Ababa solid waste dump sites reveal the higher average content of cadmium at nearest to the dump site (Beyene and Banerjee, 2011; Kebede et al., 2016). This indicated that solid waste open dump site contributes to increasing the concentration of heavy metals in the nearest soil. The finding in this study was higher than the findings of Abdourahamane et al. (2015) and Kebede et al. (2016) in Maradi (Niger Republic) and Adama (Ethiopia) dump sites respectively.
However, The finding in this study was lower than another finding of Beyene and Banerjee (2011) in Addis Ababa dump site. The reason might be due to the difference in the age of dump sites and type of cadmium-containing wastes such as paints, batteries, plastics, agricultural use of sludge, fertilizers, galvanized materials, and cadmium plated containers were indiscriminately disposed of in the dump sites.
The values of copper in the study area was higher than the finding of Prechthai et al. (2008), Ideriah et al. (2010) and Beyene and Banerjee (2011). Moreover, the values were higher than the limit prescribed by US EPA standard of 200 mg/kg Haliru et al. (2014) except for the reference site. However, the values of copper in the study area were lower than the limit value prescribed by Ethiopian EPA (2003) standard of 500 mg/kg.
The highest concentration of zinc with distance variation may be related with adsorption of metals into the nature of soil with organic matter, texture, and pH (Fern et al., 2007; Haberhauer, 2007; Abu-Zahra et al., 2010; Shiva Kumar and Srikantaswamy, 2014). The values of zinc in the study area was higher than the finding of Beyene and Banerjee (2011) and Abdourahamane et al, (2015) in Addis Ababa (Ethiopia) and Maradi city (Niger Republic) dump sites shows 131.8 mg/kg and 97.98 mg/kg respectively. It might be due to discharges of smelter slag, wastes, and the use of commercial products such as fertilizers and wood preservatives that contain zinc disposed of in the dump sites.
Zinc demonstrated considerable high mean values in the sample sites unless. It indicating that soil where largely polluted with zinc around the solid waste dump site. According to Haliru et al. (2014), it was revealed higher values than normal concentration in soil. Additionally, it was higher values than the limits prescribed by Ethiopian EPA, US EPA, EU and UK guideline values between 150 and 300 mg/kg.
Physico-chemical and biological parameters of surface water and leachate samples
A study increase in water temperature in the course of leachate, downstream and the point near to dump sites were noticed i.e. 32.00±0.02°C, 27.00±0.2°C, and 27.00±0.5°C respectively. A high in temperature was observed from leachate up to downstream. This might be due to differences in altitude and the presence of the effluents emanated from the open dump site. Since water temperature affects the concentration of biological, physical, and chemical constituents of water, the relatively high temperatures recorded would speed up the decomposition of organic matter in the water (Nartey et al., 2012).
The leachate sample was recorded higher pH (8.5±0.11). This shows that the leachate was alkaline and this was typical of the sample from aged wastes (Osei et al., 2011) and near to dump site and downstream sample sites recorded 8.1±0.11 and 8±0.1 respectively. The higher range of pH indicates higher productivity of water. Another studies conducted by Nkowacha et al. (2011), Karijia et al. (2013), Nirmala Dharmarathne (2013) and Hailemariam and Ajeme (2014 ) in Nigeria, Juba (South Sudan), Sri Lanka, and Addis Ababa (Ethiopia) solid waste dump sites respectively substantiate this finding which shows slightly basic pH in the nearby stream. However, the mean values of pH of water samples varied between 7.6±0.21 and 8.5±0.1were found the limit value prescribed by World Health Organization (2004) between 6.5 and 8.5 and limit value prescribed by Ethiopia EPA (2003) between 6 and 9.
The mean value of TDS in sample point of the upper stream, leachate, near to dump site, and downstream from the dump sites were registered 446.3±0.26, 782.5±0.15, 557.9±0.1, and 495.7±0.1mg/l respectively. The sample points of leachate and near to dump sites were showed higher TDS values than the limit prescribed by WHO (2004) standard (500 mg/l). On the other hand sample point of the upper stream was lower values of TDS. This might be due to the effect of the dump site.
The lowest mean value of turbidity was observed in the upper stream sample site 61.6±0.01 NTU even though it was above the limit prescribed by WHO (2004) standard value (25 NTU). It might be due to indiscriminate disposal of waste into the water bodies. The higher turbidity in the other sites might be due to the influence of open dump site. It was the highest turbidity values than investigated by Gopalkrushna (2011) in and around Akoyo city and Aljaradin and Persson (2012) in Jordan dump sites are reveal between 13.4 and 4.7 NTU and between 40 and 160 NTU respectively in the nearby stream and leachate water.
According to the US EPA (2002) turbidity values between 0.0 and 5.0 NTU show no visible turbidity, no adverse aesthetic effects and no significant risk of infectious disease transmission. The values ˃ 10 NTU have severe aesthetic effects and the water carries an associated risk of diseases due to infectious agents and chemicals absorbed onto particulate matter (Nartey et al., 2012).
Electrical conductivity (EC) is a measure of water capacity to convey electric current. It signifies the amount of total dissolved salts (Gopalkrushna, 2011) and it is also defined as a number of ions (positive and negative) offer in water (Hasan et al., 2016). The sample site of leachate, near to dump site, and downstream sample sites were recorded the maximum EC values than the upper stream. However, they fell under the EEPA (2003) and WHO (2004) acceptable limits of 1000 and 1400 μS/cm respectively.
High EC value was observed in leachate sample 391.35 μS/cm. It indicating the presence of high amount of dissolved inorganic substances in ionized form in and around solid waste dump site (Siddiqui, 2015). In addition, the higher value of EC is a good indicator of the presence of contaminants such as potassium and sulfate (Nazir et al., 2015).
When considering the average value of conductivity in the leachate sample concluded that leachate was the high amount of ionizable material. The result of this study was less than the other studies conducted in Addis Ababa (Ethiopia) and Sri Lanka solid waste dump sites show 1102 μS/cm up to 3720 μS/cm and 1136 μS/cm respectively in the nearby stream (A.Abiye, 2012; Dharmarathne and Gunatilake, 2013). The result of this study was higher than a similar study conducted in Juba (South Sudan) the average values of electrical conductivity show between 89μS/cm and 229μS/cm in the nearby stream (Karijia et al., 2013).
According to EU guidelines, the COD value in drinking water is 5 mg/l (Maqbool et al., 2011). It was observed that the values were higher than the permissible limit in all samples. It indicates the stream water was highly polluted with the chemicals which might have resulted from the solid waste dump site and indiscriminate disposal of solid waste in the nearby stream.
Nitrate values in all the sites were registered higher than the natural background level of 0.23 mg/l. The presence of nitrate may be the result of waste being disposed of at the dump sites and indiscriminate disposal of solid waste into the water body. Thus, contamination of the water bodies with chemicals from the dump sites is likely to occur. It could be attributed to runoff from farms along the banks of the rivers which may contain organic fertilizers.
The values of nitrate in the study area were lower than the similar studies conducted in Addis Ababa (Ethiopia) and Accra (Ghana) solid waste dump sites show nitrate concentration between 2.0-2.2 mg/l and 4.18-30.8 mg/l respectively in the nearby stream (A. Abiye, 2012; Nartey et al. (2012) and higher than another study conducted at Accra (Ghana) nitrate concentration reveal 0.046 mg/l in the upper stream up to 0.418 mg/l in the downstream (Osei et al., 2011). However, the values revealed for all the sample sites did not exceed the limits prescribed by WHO (2004) and EEPA (2003) standards of 20 mg/l and 50 mg/l respectively.
Excess intake of fluoride through drinking water causes fluorosis on the human being (Gopalkrushna, 2011). All sample sites were recorded under the limit prescribed by EEPA (2003) 1 mg/l and WHO (2004) guideline value of 1.5 mg/l except for the leachate (L) sample site the mean value was measured 1.71±0.01 mg/l. However, the remaining site especially the point near to dump site (DS1) and the downstream sample location (DS2) registered the highest concentration compared with the upper stream (0.8±0.01mg/l).
It was the highest result compared with Gopalkrushna (2011) finding lie less than 0.05mg/l in the nearby stream. This might be due to fluoride-containing materials such as wood preservatives, glasses, and enamel indiscriminately dumps in an open dump site and in the nearby stream.
All mean values of sulfate were below the limits prescribed by EEPA (2003) and WHO (2004) standards (200 mg/l). The values were lower than other findings in Akot city and Addis Ababa solid waste dump sites the sulfate concentration varies between 263-62.8 mg/l and 53-342 mg/l respectively (Gopalkrushna, 2011; A.Abiye, 2012) in the nearby stream but the values were higher than another finding in Accra (Ghana) dump site shows sulfate concentration varies b/n 0.2 mg/l in upper stream and 25 mg/l in leachate water (Osei et al., 2011).
The potassium concentration in water samples was lower than 73 mg/l investigated by Kamboj et al., (2013) and potassium concentration in the study area was higher than 15 mg/l to 5.1 mg/l investigated by Gopalkrushna (2011).
The values of BOD5 in the study area were higher than the limits prescribed by EEPA (2003) and WHO (2004) standards of 5 mg/l. In addition, it was higher than a similar study conducted in Accra (Ghana) reveal 1.25 mg/l up to 100 mg/l in the nearby stream and leachate samples respectively (Osei et al., 2011). The high BOD5 values may be attributed to the discharge of organic waste into water bodies resulting in the uptake of DO in the oxidative breakdown of these wastes (Alemayehu, T., 2001). The dump site might be a factor promoting the loading of the water body with organic matter hence, the high BOD5 value.
Heavy Metals in River Water and Leachate Samples
Table 4 shows that the concentration of cadmium in all water samples were below detection limit (<0.02mg/l) and below the limit prescribed by EEPA (2003) and WHO (2004) standards 0.005 and 0.003 mg/l respectively except for leachate sample was revealed 0.3±0.01mg/l. It might be due to the solid waste composition that contained batteries and paints were indiscriminately disposed of in the dump site. It also might be due to the organic matter, pH, and texture of soil (Haberhauer, 2007; Abu-Zahra et al., 2010; Shiva Kumar and Srikantaswamy, 2014) near to dump site which adsorbed the heavy metal and retained on it. Other studies in Accra (Ghana) and India confirm this finding (Raman and Narayanan, 2008; Osei et al., 2011 and Nartey et al., 2012) cadmium concentration in surface water near to the dump site shows lower than 0.003 mg/l.
The concentration of copper in the study sites fell within this range except for the leachate sample showed the highest value of copper was revealed above the limit prescribed by EEPA (2003) and WHO (2004) standards (0.1 mg/l). It also higher value than similar studies conducted in Accra (Ghana) dump site reveal below 0.059 mg/l and lower than another finding in Sri Lanka the values of copper in surface and leachate water near to dump site reveal between 0.08 and 9.9 mg/l (Osei et al., 2011; Nirmala Dharmarathne, 2013 ). Hence, copper levels in the river systems pose no threat to the environment and human health.
The values of zinc in the study area were higher than another study conducted in Accra (Ghana) the concentration of zinc nearby stream is below detection limit (Nartey et al., 2012), however, lower than another finding in Sri Lanka record 0.1-9.9 mg/l in leachate water (Nirmala Dharmarathne, 2013). It might be due to discharges of smelter slag and wastes, and the use of commercial products such as fertilizers and wood preservatives that contain zinc disposed of in the water body and in the nearby dump site.
According to Maqbool et al., (2011) the permissible limit of zinc in water is 0.05 mg/l save for consumer. According to EEPA (2003), the prescribed limit of zinc in surface water lies between 0.003 mg/l and 0.5 mg/l. However, the values of zinc in the study area revealed between the limit prescribed by EEPA (2003) except for the leachate sample exceeded the standard.
According to WHO (2004), the standard value of a nickel is 0.02 mg/l. Nickel values at the site near to dump site (0.08mg/l) and the downstream locations (0.06 mg/l) were slightly greater than the permissible standard limit of WHO (2004) except for the upper stream the lowest concentration of nickel was observed below in detection limits (< 0.04 mg/l). However, the values were lower than the limit prescribed by EEPA (2003) 0.1 mg/l except for the leachate sample. It might be due to indiscriminate disposal of nickel-containing solid wastes such as electroplating, zinc base casting and storage battery indiscriminately dump in open dump site near to the river. Another finding in Abbottabad (Pakistan) and Sri Lanka also authenticate this result nickel value ranges between 0.03 and 9.9 mg/l in the nearby stream and leachate water (Maqbool et al., 2011; Nirmala Dharmarathne, 2013).
The leachate water had the highest lead concentration compared to other streams. In addition, it contained high lead value than the permissible limits of EEPA (2003) and WHO (2004) standard (0.05 mg/l). It might be due to quantity and constitute of municipal solid waste that contains lead contents such as electronic waste, lead batteries, lead-based paints, pipes, and plastics were indiscriminately disposed of in the dump site. Gradually, due to erosion leachate might drain into the stream and increase lead concentration in stream water. Other studies in India and Accra (Ghana) dump sites authenticate this finding (Raman and Narayanan, 2008; Nartey et al., 2012) the lead values are revealed between below detection limit and 0.07mg/l respectively in the nearby surface water.
The values of manganese at leachate and downstream sample sites were higher than the guideline values of EEPA (2003) 0.3 mg/l and WHO (2004) 0.1 mg/l. The presence of manganese might be due to indiscriminate disposal of solid waste in the river and discharge from leachate. In addition, a high amount of manganese may be due to waste containing dry cell batteries, paints, glasses, and ceramics were disposed of in the open dump site and pollution from manganese dioxide cells for which the town has no controlled methods of disposal. The metal may also come from other sources such as domestic wastewater and sewage sludge disposal. Leachate and downstream sites registered the amount above prescribe limits of EEPA (2003) and WHO (2004) standards. However, the finding was lower than another finding of Nirmala Dharmarathne (2013) in Sri Lanka reveal 2.7 mg/l in leachate water near to dump site.