Land-use and local activities are the most important factors in the recent chemical changes of the atmospheric environment. This study was conducted in Ile – Ife and environs, an old urban/agrarian area of Osun state Nigeria to characterize the chemical features of rainwater. The goal of the study was to assess the impact of land use activities on rain water composition and the temporal variation of rainwater chemistry. Rainwater samples were collected from twelve different locations representing four land use (Residential, Commercial, Industrial and Agrarian) areas from October 2012 to September 2013. The sampling points included area with vehicular emission (High, moderate and low traffic), agricultural activities (fertilizer and insecticides applications, bush burning etc.), emissions from waste, and Industrial activities. Physico-chemical parameters such as Turbidity, pH, TDS, Conductivity, Oxygen parameters, Alkalinity, Acidity, Hardness and Major ions (Ca2+, Mg2+, K+, Na+, NO3-, SO4-, HCO3-) were determined, predominant ions were identified. Turbidity, pH, Conductivity, TDS, D.O B.O.D, Alkalinity, Acidity Hardness ranged between 2.90 - 42.84 NTU, 5.65 - 7.40, 6.71 – 122.33 µScm-1, 4.10 –73.27 mg/L, 3.60 – 10.60 mg/L, 0.13 – 7.20 mg/L, 0.33 – 22.0 mg/L, 2.00 – 15.00 mg/L, 0.04 – 1.23 CaCO3mg/l respectively. The dominant ions detected in the study were HCO3-, Mg2+, Na+ and Ca2+. Generally, the mean concentration of ions as expressed in milli-equivalent per Litre showed order of dominance as HCO3- &gt; NO3- &gt; SO42- for the anions and Mg2+ &gt; Na+ &gt; Ca2+ &gt; K+ for cations. The study concluded that land use activities had influence on all the chemical composition of rain water in the study area but more on pH, alkalinity, acidity, bicarbonate. Except sulphate and Nitrate, all other parameters recorded high values in dry season (October to March).

Spatial variation of rainwater chemistry in Ile-Ife, Osun State, Nigeria

249th National Meeting (2015)

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