Heavy Metal Analysis in Rainwaters as Indicator of Aerial Pollution

Heavy metals in rainwaters collected in open spaces within residential, industrial and commercial areas in Ibadan, Nigeria were investigated using Atomic Absorption Spectrophotometry to assess the level of aerial pollution of the metropolis. It is observed that Zn has the highest concentration followed by Pb. Results indicated that the concentrations of the analyzed metals were higher at the onset of the rainy period than the latter periods indicating washout of the metals as the rainy season progressed. Results showed that the concentrations of Zn, Pb, Cd, Mn and Cu were higher than their allowable limits; enrichment factor showed moderate to significant enrichment and pollution index values were higher than 1, indicating aerial contamination. Correlation matrix analyses showed that most of the metals had similar chemical affinities/or background values. There was a significant difference between the mean concentrations of metals at the different locations studied (P ≤ 0.05), suggesting that the metals originated from different sources. Three factors were resolved with Positive Matrix Factorization receptor model for the heavy metals in the rainwater samples viz: traffic dust (35%), industrial emissions (39%), metallurgy industry (26%). The study proved metal in rainwater to be a reliable fingerprint of evaluating aerial pollution.