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Pollution Status of Awash River and Heavy Metals Levels In Soil and Vegetables Cultivated at Koka and Wonji Farmlands, Ethiopia

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dc.contributor.advisor Leta, Seyoum (PhD)
dc.contributor.author Eliku, Temesgen
dc.date.accessioned 2019-11-08T10:28:55Z
dc.date.available 2019-11-08T10:28:55Z
dc.date.issued 2018-05-05
dc.identifier.uri http://etd.aau.edu.et/xmlui/handle/123456789/20046
dc.description.abstract Among the major rivers in Ethiopia, Awash River which flows from the central highlands through Ethiopia’s major industrial and agro-industrial belt is absorbing most domestic, agricultural and industrial wastes. The purpose of this research work is to assess pollution status of Awash River and levels of heavy metals in soil and in edible portions of vegetables. Physical parameters (WT, pH, turbidity and electrical conductivity) were measured on site. The chemical and the bio-chemical parameters were determined in the laboratory following standard protocols. The quantification of heavy metals in river water, sediment, wastewater, soil and vegetables at different sites of Koka and Wonji Gefersa was done using flame atomic absorption spectrophotometer. The result indicated that the mean value of water temperature, pH, turbidity, NO3-N, TN, DO, BOD in Awash River during dry season were 21.32-23.01 0C, 6.21-8.06, 36.4-72.67 NTU, 0.8-27.87 mg l-1, 2.28-83.43 mg l-1, 3.62-7.58 mg l-1 and 16.22-80.32 mg l-1 whereas the mean values in wet season were 20.6 - 21.9 0C, 6.27-8.13, 95.08-139.61 NTU, 0.48-13.78 mg l-1, 1.22-17.75 mg l-1, 4.25-10.82 mg l-1, and 11.13-38.32 mg l-1 respectively. There were a significant spatial and seasonal variation (P < 0.05) of mean turbidity and NH4-N in Awash River but there was no significant spatial and seasonal variation (P > 0.05) of average TP in Awash River. The result showed that the average values of Fe, Zn, Cu, Pb, Cr and Cd in Awash River during dry season in eight sampling points were 1.11-2.73, 0.74-1.56, 0.82-1.69, 0.41-1.36, 0.36-1.16 and 0.05-0.24 mg l-1 while the mean values in wet season were 1.82-4.12, 0.46-0.91, 0.44-1.01, 0.31-0.83, 0.3-0.98 and 0.03-0.09 mg l-1 respectively. Matrices of correlation coefficient between the metal levels in Awash River revealed that Strong and positive correlations between (Fe/Zn, r = 0.847), (Fe/Pb, r = 0.81), (Fe/Cr, r = 0.824), (Fe/Cd, 0.802), (Zn/Pb, r = 0.82), (Zn/Cd, r = 0.824), (Cu/Cr, r = 0.844) during dry season. The average values of Fe, Zn, Cu, Pb, Cr and Cd in Awash River Sediment during dry season in eight sampling points were 222.27-300.74, 73.32-103.97, 19.01-34.96, 23.7-37.31, 45.96-62.48 VI and 0.53-1.34 mg kg-1 whereas the average concentration during wet season were 229.82-307.05, 66.24-86.89, 20.01-29.0, 25.98-45.19, 45.28-65.91 and 0.37-1.15 respectively. The mean concentrations of heavy metals in vegetable fields’ soil samples obtained from Koka were higher for Pb, Cr, Zn, Cu, and Ni. The overall results of soil samples ranged 0.52–0.93, 13.6–27.3, 10.0– 21.8, 44.4–88.5, 11.9–30.3, and 14.7–34.5 mg kg−1 for Cd, Pb, Cr, Zn, Cu, and Ni, respectively. The concentrations of heavy metals were maximum for Cd, Pb, Zn, Cu and Ni in Cabbage and for Cr in green pepper. The result indicated that Cd has high transfer factor value and Pb was the lowest. The transfer pattern for heavy metals in different vegetables showed a trend in the order: Cd > Zn > Cu > Cr > Ni > Pb. Among different vegetables, cabbage showed the highest value of metal pollution index and French bean had the lowest value. Hazard index of all the vegetables was less than unity. Results of PCA analysis of the four and the five data sets which explained 92.76% and 94.38% of the total variance in wet and dry seasons showed the pollutant sources were mainly related to non-point pollution through agricultural soil runoff and point source of pollution from the industries at the upstream area. Hierarchical cluster analysis grouped the eight sampling stations into three clusters representing different levels of pollution. During dry season, cluster 1 (Site-1 and 6) were located in low pollution region. Cluster 2 (Site-2, 3, 5and 8) corresponded to moderate pollution site. Cluster 3 (Site 4) were in regions of high pollution. Vegetation cover alongside Awash River has to be maintained and enhanced so as to filter pollutants from the runoff or nonpoint sources. Moreover regular monitoring of toxic heavy metals in vegetables by concerned bodies is vital to prevent disproportionate build up in the food chain. en_US
dc.language.iso en en_US
dc.publisher Addis Ababa University en_US
dc.subject Heavy Metals en_US
dc.subject Dry Season en_US
dc.subject Wet Season en_US
dc.subject Transfer Factor en_US
dc.subject Hazard Index en_US
dc.title Pollution Status of Awash River and Heavy Metals Levels In Soil and Vegetables Cultivated at Koka and Wonji Farmlands, Ethiopia en_US
dc.type Thesis en_US


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