Evaluation of the Spatial Variation of Rainwater Quality in Parts of Akwa Ibom State of Nigeria Using Chloropleth Map

Studies on the effects of oil exploration activities in Akwa Ibom State of Nigeria have shown that the air quality has been negatively impacted over the years. The quality of rainwater is a function of the prevailing air quality in any area where it falls. Rainwater is an alternative water supply for most of the local population. This study evaluated the spatial variation of rainwater quality in selected locations in parts of Akwa Ibom State within the months of March, July and November using temperature, pH, colour, NO₃, Fe, Pb, Cd, and Mn as indices. Control locations in the northern part of the State were also selected. Results showed that rainwater quality in study locations in the south (5.1-5.7) was more acidic than in the north (5.4 - 6.9). Generally, values of quality parameters in the study locations were higher than their values in the control locations and followed the pattern March > November > July values. Critical levels of heavy metals were observed (Fe: 0.21 - 0.62 mg/l; Pb: 0.12 - 0.90 mg/l; Cd: 0.01 - 0.05 mg/l; Mn: 0.02 - 0.07 mg/l in study locations) and Fe: 0.1 - 0.90 mg/l; Pb: 0.01 - 0.60 mg/l; Cd: 0.00 - 0.003 mg/l and Mn: 0.01 - 2.10 mg/l in control locations). It was also established that rainwater contaminant levels are a function of the frequency and intensity of the rainfall; the levels in this study expectedly reduced with an increased rainwater intensity. Wind action and lithogenic effects played a role in the dry periods.