SOURCE IDENTIFICATION AND VARIATION IN THE CHEMICAL COMPOSITION OF RAINWATER IN THE COASTAL AND INDUSTRIAL AREAS: A CASE STUDY OF IKOT ABASI, SOUTH-EASTERN NIGERIA
Journal: Earth Science Malaysia (ESMY)
Etesin, Usoro Monday, George, Nyakno Jimmy, Ogbonna, Iniobong Joseph, Akpan, Itohowo Okon
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Studies on precipitation Chemistry were carried out with the aim to understand the nature and sources of rainwater at Utaewa (Location 1), a coastal village and Ikpetim, near Ibom Power Station (Location 2), all in Ikot Abasi Local Government Area, southern, Nigeria. These locations respectively represent the coastal and industrial regions. The rainwater samples, collected at these locations, were analyzed for major cations, anions, electrical conductivity and pH with the aim of identification of variation in the physiochemical compositions of the rainwater samples. The analysis of the rainwater samples gave a pH at locations 1 and 2 as 5.62 ± 0.26 and 5.77± 0.25 respectively during the wet season, while the pH of the rainwater at locations 1 and 2 during dry season were 5.41 ± 0.14 and 5.84 ± 0.21 respectively. The pH values indicated acidic water and were below the World Health Organisation (WHO) Standard of 6.5 to 8.5, but close to the World Meteorological Organisation (WMO) optimum pH value of 5.6 for rainwater from unpolluted continental areas. The predominance of 𝐶𝑙−and𝑁𝑎+ were observed in the coastal environment whereas, calcium, sulphate, nitrate and ammonium ions predominate in industrial environment where there are power generating plants, Aluminium smelting company and gas station. The total anion (37.9%) at Utaewa is less influenced by anthropogenic activities whereas total anion (72.5%) at Ikpetim, near Power Plant is influenced by pollutants emitted by anthropogenic activities. The ratio:𝐻+/(NO3- + SO42-) was observed as 0.04 and 0.008 for Utaewa and Ikpetim respectively, which are close to zero, indicating that 99 % of acidity in the rainwater is neutralized in the study area with no consequence of acidity impact on the soil, surface waters and groundwater in the study area. Ca2+ , K+ and Na+ play important roles in neutralization of acidic ions in rainwater. For source identification, correlation matrix analysis was established, which showed that at locations 1 and 2,strong correlation exists between the acidic ions SO42- and NO3-, indicating their origin from anthropogenic activities. This is viewed to be attributed to the similarity in their behaviour in precipitation and the co-emissions of their precursors, which are SO2 and NO2. The major ion enrichment factors (EF) followed the order at location 1 during the dry season;𝐶𝑎2+𝑁𝑎+⁄ (8.58) >𝐾+𝑁𝑎+⁄ (4.32) >𝑆𝑂42−𝑁𝑎+⁄ (0.68) >𝐶𝑙−𝑁𝑎+⁄ (0.11), while the enrichment factor (EF ) during the wet season at location 1 followed the order , 𝐶𝑎2+𝑁𝑎+⁄ (11.92 )>𝐾+𝑁𝑎+⁄ (3.78) >𝑆𝑂42−𝑁𝑎+⁄ (0.88) >𝐶𝑙−𝑁𝑎+⁄ (0.11).