ABSTRACT

Water hyacinth, a fast proliferating free-floating aquatic macrophyte and anthropogenic activities can influence the quality of river sediment. The physicochemical parameters of the sediment of Ovia River, a tropical rainforest was assessed for the effects of water hyacinth (Eichhornia crassipes) and anthropogenic activities. Sampling period was from April to September, 2019 and samples were collected from three different stations using flat hand shovel and grab sampler. The samples were analysed using standard procedures. Heavy metals were analysed using flame Atomic Absorption Spectrophotometer. The spatial variation mean ranged from 25.417 – 27°C (sediment temperature), 5.28 – 6.017 (pH), 110.0 – 131.67µS/cm (EC), 0.824 – 2.45% (TOC), 4.08 – 5.30mg/L (nitrate), 1.32 – 3.14mg/L (phosphate), 0.44 – 1.60mg/L (ammonium), 0.062 – 0.103mg/kg (cadmium), 0.498 0.96mg/kg (chromium), 7.22 – 9.11mg/kg (copper), 21.61 – 25.89mg/kg (iron), 0.424 – 1.02mg/kg (lead), 6.49 – 9.679mg/kg (zinc). The results of the seasonal variation mean are 26.33°C and 26.17°C (sediment temperature), 6.1 and 5.1 (pH), 96.67µS/cm and 136.67µS/cm (EC), 0.715% and 2.446% (TOC), 5.987mg/L and 7.233mg/L (nitrate), 1.792mg/L and 5.435mg/L (phosphate), 1.743mg/L and 1.98mg/L (ammonium), 0.088mg/kg and 0.171mg/kg (cadmium), 1.280mg/kg and 1.544mg/kg (chromium), 11.993mg/kg and 12.047mg/kg (copper), 22.611mg/kg and 26.916mg/kg (iron), 1.573mg/kg and 1.420mg/kg (lead), 8.179mg/kg and 13.954mg/kg (zinc) for the dry and wet seasons respectively. Analysis of variance showed that there were no significant difference in spatial and seasonal variation. Contamination degree and pollution load index showed that station 1 and 3 were non-polluted, while station 2 showed low degree of contamination. The Geoaccumulation index showed no pollution with respect to all the heavy metals except for iron. Though findings from this study shows no pollution, Ovia River needs to be kept under close monitoring for increase of pollution due to anthropogenic activities and effective control of water hyacinth is necessary.