ASSESSMENT OF POLLUTION LOAD ON RIVER ONA
Abstract
This study investigates the concentration of 8 trace metal elements in surface water of River Ona at Oluyole Industrial area, to evaluate the impact of industrial effluents on the water. Water samples were collected from 10 sampling points across 3 industrial zones which are Sumal, Amir Plast, and P&G including a residential zone. Each zone featured one raw discharge point and two river sampling points positioned at interval of 3 meters from the raw discharge point.
Results showed a decreasing mean concentration trend of: Iron (Fe) > Lead (Pb) > Nickel (Ni) > Arsenic (As) > Zinc (Zn) > Copper (Cu) > Chromium (Cr) > Cadmium (Cd), with some metals exceeding the permissible limit provided by W.H.O and N.I.S. The Pollution Load Index (PLI), Geo-accumulation Index (Igeo) and the Water Quality Index (WQI) were utilized. The PLI values for the raw stations were; Sumal raw discharge 0.246, Amir Plast raw discharge 0.082, and P&G raw discharge 0.16. For the river water sampling points, the PLI values were; Sumal water sample 0.167, Amir Plast water sample 0.137, and P&G water sample 0.124. The PLI value recorded for all points is less than 1 indicating no pollution. The Igeo value for Zinc, Copper, Chromium, and Cadmium fall in Class ‘0’ In all sampling points, indicating no pollution of these metals. Nickel (Ni) fall in Class 2 in Sumal raw discharge point, indicating moderate contamination. The highest concentration value recorded for Lead (Pb) fall in Class 5 at the residential zone which indicates the area is heavily to extremely contaminated with Pb. Iron (Fe) also fall in Class 3 in Sumal raw discharge point indicating moderately to heavily contaminated. Arsenic (Ar) fall in Class 2 in Sumal water sample and Amir Plast raw sample, indicating moderate contamination and it fall in Class 4 in P&G water sample which indicates heavy contamination of Ar in these points.
The NSF-WQI gave 55.89 index value, which suggest moderate water quality of the River. The result obtained showed additional pollutant in comparison with the industrial raw effluent. These findings highlight the impact of industrial and anthropogenic activities on River Ona and underscore the need for targeted pollution control measures for the protection of the ecosystem and public health.
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