Constituent budget and pollution models of Njaba River and its sediments, SouthEastern Nigeria
Date
2021-12
Authors
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Journal ISSN
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Publisher
Federal University of Technology, Owerri
Abstract
The physical, microbial, and geochemical properties of the Njaba River and its sediments were analyzed using Atomic Absorption Spectrophotometer (AAS), digital meters, and Total Plate Counts. A total of ten (10) surface water samples, five (5) soil samples, and five (5) sediment samples were obtained at five gauge stations (S1 to S5) designated at equal intervals of 2 km along the stretch of the river. The results of the water showed a slightly acidic to alkaline composition (6.44-6.77). This trend was also noticed in the soil samples within the river basin (6.24- 6.64) while the river sediment samples revealed pH values ranging between 6.30-6.52. The Odour of the water was unobjectionable while the appearance was slightly brownish. The presence of heavy metals such as Fe, Al, Si, and Zn was within the acceptable limits. On the other hand, the concentration of Hg which ranged between 0.001-0.071 mg/l and Pb with values between 0.060-0.23 mg/l were above acceptable limits of the FME Standard at most of the stations. The microbial assay of the water, soil, and sediments revealed the presence of organisms such as Ecoli bacteria, pseudomonas, fecal coliform, and fungi. The constituent budget of the Njaba River analyzed at Okwudor and Oguta over a period of eight years (2011 – 2019) and seven years (2012 – 2019) respectively revealed an increasing loading rate of the following constituents( Ca2+ 0.013, Mg2+ 0.70, Na+0.013, K+1.68, SO2-4 0.29, NO 3 0.15, Cl- 2.97, and PO-34 0.063 ) within the Njaba River with a decline in the concentration of HCO 3 (-0.63) at Okwudor and a decline of NO 3 (-0.03) at Oguta Lake. Pollution and ecological assessment models like Contamination Factor (CF), Pollution Load Index, Enrichment Factor, and Geoaccumulation Index(Igeo) were used to infer contamination levels of heavy metals in the soil and stream sediments. The CF results revealed Hg (0.46), Pb(2.35E-4 to 0.02), Al(ND), Zn (5.71E-4 to 1.2E-3)which shows low contamination factor in soil, the same trend was also found in the sediments with Hg (0.277), Pb (2.63E-6), Al (ND), Zn (3.64E-4 to 8.14E-4) and Fe(2.10E-6 to 2.63E-6) while the water samples have very high contamination factor for Pb (6.0 to 23), Hg revealed moderately contamination to very high contamination (0.1 to 7.1), Al (ND), Zn (0.192 to 0.403) and Fe (0.1 to 0.93). The I-geo revealed uncontaminated to moderately contaminated in the soil and stream sediment samples with Hg (0.28),>Pb( 1.57E-4 to 0.01),>Zn( 3.83E-4 to 8.04E-4), and Al(ND) for the soil samples while the stream sediments were in order of Hg (0.277),>Pb (1.15E-3 to 1.27E-3),>Zn (3.64E-4 to 8.14E-4) and Al (ND). The EF revealed low to minimal enrichment for the soil and stream sediment samples with Hg (0), Pb (0.303 to 1.000), Si ( 1.000 to 1.053), Zn (0.491 to 1.000) and Al (0) in soil and Hg (0), Pb (0.907 to 1.000), Si (1.000 to 1.282), Zn (0.051 to 0.114), Fe (0.800 to 1.000) and AL (ND) for stream sediments. The river water is however suitable for agricultural purposes based on the calculated SAR values with the dominant hydrogeochemical facies given as Na+K+Cl water type. In conclusion, there is a need for necessary treatment procedures which should be applied to raise the quality of the river water to the FME standards for safe drinking water for example the pH can be corrected (raised) using sodium bicarbonate (soda ash). The heavy metals can be treated using ascorbic or ion exchange methods while the microbial assay can be improved upon subjection to treatment using chlorine.
Description
The thesis is for the award of the degree of Master of Science (M.Sc.) in Environmental Geology
Keywords
Constituents budget, physico-chemical, water quality index, contamination factor, geo-accumulation Index, Department of Geology
Citation
Abiahu, C. M. G. (2021). Constituent budget and pollution models of Njaba River and its sediments, SouthEastern Nigeria (Unpublished Masters Thesis). Federal University of Technology, Owerri, Nigeria