Seasonality, Collinearity and Quality Assessment of the Physicochemical Properties of Okoro River Estuary, South Eastern Nigeria

Aim: To decipher the effect of season on the water quality of Okoro River estuary.

Study Design: The study was designed to cover two wet and two dry seasons for 24 months. Triplicate samples were taken per month and mean taken to represent each month. Fifteen (15) physicochemical parameters were measured for 24 months.

Place and Duration of Study: The study was carried out in Okoro River estuary, Southeastern Nigeria between April 2011 and March 2013.

Methodology: The analyses of physicochemical properties followed standard protocol in American Public Health Association (APHA).

Results: Nine physicochemical variables: temperature, pH ,TSS, TDS , DO, water hardness, Na and rainfall varied significantly between rainy and dry season (p<0.05), while six variables: BOD5 THC, Ni, K, Cu and Zn were not significantly different (p>0.05) between the two seasons. The result also showed collinerity among the physicochemical parameters. Salinity fluctuated from 24.10‰ in the rainy season to 30.90‰ in the dry season. Temperature ranged from 24.7ºC to 34.4ºC with mean annual water temperature of 28± 1.934ºC. Water temperature decreases with increase in rainfall. The pH values indicate slightly alkaline nature with mean of 7.38± 0.58. The geochemical indices of the three metals (Ni, Cu and Zn) ranged between 0.06 – 0.26 mg/l and showed signs of trace metal pollution. BOD ranged from 2.01 – 4.22 mg/l with a mean value of 3.04± 0.54 while DO ranged from 6.1 – 8.24 mg/l with a mean value of 7.24± 0.72 mg/l. The maximum value of 716.0 mg/l recorded for sodium indicated saline intrusion in the estuary. The total hydrocarbon content (THC) level of 0.01-2.65 mg/l indicated that the estuary is suffering from oil pollution. The pollution content in the estuary was as a result of anthropogenic perturbation. The water of the estuary was found to be hard (418.68 ± 90.6 mg/l) and may not serve as good source of drinking for the community since the value is higher than 300 mg/l recommended by WHO, 2011 but could serve as an excellent source of natural resources development.

Conclusion: The results revealed that most of the physicochemical parameters were significantly different at (p=0.05) between the dry and rainy seasons. Positive and negative associations indicated natural selection and connection of the physicochemical and environmental parameters in the ecological system.