SEASONAL VARIATIONS OF ALKALINITY OF SURFACE WATERS IN PARTS OF AKWA IBOM STATE, SOUTH- SOUTH, NIGERIA

Alkalinity of surface waters is a measure of the capability of water to neutralize the level of acidity of water. This is really an expression of buffering capacity of water. Alkalinity is important for fish and aquatic life because it protects or buffers against rapid pH changes. Living organisms, especially aquatic life, function best in a pH range of 6.0 to 9.0. Calcium carbonate saturation indices (Langelier) commonly are used to evaluate the scale-forming and scale-dissolving tendencies of water, and is related to alkalinity of water. Higher alkalinity levels in surface waters will buffer acid rain and other acid wastes from anthropogenic activities and prevent pH changes that are harmful to aquatic life. For protection of aquatic life the buffering capacity should be at least 20 mg/L CaCO3. This study aims at the determination of seasonal variations of total alkalinity, total hardness and langelier saturation index of surface waters in Uyo, Ikot Ekpene and Eket , by computer aided potentiometry. From the results of alkalinity determination, it is significant that all the locations have higher than 20 mg/L total alkalinity, that falls within the limit of moderate alkalinity ( 50 mg/L – 160 mg/L ) , as the optimum alkalinity of surface waters for the protection of aquatic life and the surface waters not being negatively impacted by anthropogenic activities going on in these areas. Also, the p H of the surface waters in the studied locations in both seasons were less than 8.3, indicating that the dominant alkalinity was bicarbonate alkalinity. The total hardness determined in the surface waters of the studied locations during both rainy and dry seasons were within the water hardness classification of moderately hard ( 60 – 120 mg/L CaCO3 ) according to United State Geological Survey. The Langelier saturation index of surface waters determined in the study locations in both the rainy and dry seasons were outside the optimum range of – 0.5 to + 0.5, indicating that all the surface waters in the study areas are calcium carbonate dissolving and under -saturated with calcium carbonate, thereby have corrosive potential on metal substrates, also difficult in forming calcium carbonate scales. The seasonal variations in total alkalinity, Langelier saturation index and total hardness in the surface waters from Uyo, Ikot Ekpene and Eket were not significant at P ≤ 0.05.