| Resumo: |
The environmental impact of locating two polluting sources of landfill (refuse dump) and petrochemicals on Alaba stream in Akure, Nigeria was assessed. This was due to the dependence of Alaba inhabitants and its environment on the stream for variety of uses. Twenty physio-chemical parameters were analyzed for wet and dry seasons respectively with three sampling points within 5m intervals from one another of the two polluting sources on the stream. The parameters included: colour, odour, taste, pH, temperature, turbidity, alkalinity, conductivity, dissolved oxygen (DO), biochemical oxygen demand (BOD5) and total solids (TS). Others were chloride (CL-), total dissolved solids (TDS), total suspended solids (TSS), lead (Pb), nitrate (NO3), sulphate (SO4-2), oil and grease, E-coli and faecal coliform. Some of the parameters were determined in-situ while others were determined using APHA (2005) standard procedures and results obtained were subjected to statistical analysis. All the samples investigated contained considerable degree of pollution which asserted the pollution of the stream. The results for dry and wet seasons indicated that the pH has 6.3±0.14 and 6.65±0.58, temperature, 29.8±3.18 and 25.7±1.75, Conductivity, 353.33±15.0 and 256.67±26.58, Alkalinity, 52.83±16.0 and 90.90±20.98, DO, 0.33±0.08 and 0.48±0.01, Turbidity, 57.22±7.15 and 8.10±1.70, BOD, 0.20±0.10 and 0.22±0.11, TS, 0.42±0.22 and 2.61±2.63, TSS, 0.26±0.20 and 2.64±2.91, TDS, 0.18±0.16 and 0.46±0.42. Oil and grease, 12.02±2.86 and 5.33±2.02, E-coli, 55.37±7.45 and 8.99±3.23. Faecal coliform, 241.50±11.64 and 129.83±35.06. Pb, 13.72±7.68 and 11.88±5.20 respectively. Others were Sulphate, 1298.33±422.52 and 1273.33±423.77, Nitrate, 6.40±0.96, Chloride, 0.33±0.12. Most of the values (with the exception of pH and alkalinity) were above maximum permissible levels of FAO, WHO and NSDWQ standards and parameters such as pH, turbidity, DO, BOD, Pb, E-coli and faecal coliform decreased as the distance from the polluting sources increased. Statistical analyses showed significant differences at specified confidence levels and liner correlations among parameters. Treatment of Alaba stream is required to achieve minimum acceptable level for domestic uses for the end-user while public awareness on the dangers inherent in polluting the stream should be embarked upon and enforcing strict compliance to avoid outbreak of water-borne diseases is suggested.
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