SEASONAL VARIATION OF MONTHLY AIR QUALITY INDICES FOR CALABAR, NIGERIA SUNDAY O. UDO 1 , IGWE O. EWONA 2 , MFON DAVID UMOH 3 * AND CLETUS NZAN AGBOR 4 1 Department of Physics, University of Calabar, Calabar, Nigeria. 2 Department of Physics, Cross River State University of Technology, Calabar, Nigeria. P.M.B. 1123 Calabar, Nigeria. 3 Department of Science Maritime Academy of Nigeria, Oron, Nigeria. 4 Department of Physics University of Calabar, Calabar, Nigeria.. (Received 10 November, 2017; accepted 23 April, 2018) Key words: Air Quality Index, Coeffcient of determination, Ozone, Pollutants, Categorized, September Jr. of Industrial Pollution Control 34(1)(2018) pp 1847-1853 www.icontrolpollution.com Research Article *Corresponding authors email: mfonslago@yahoo.com ABSTRACT Air Quality Index (AQI) for the city of Calabar has been computed for the different seasons of the year covering December 2015 to November 2016. The values obtained from the calculation of the combined AQI shows that the AQI for the different months of the year were categorized as “good”. The highest value of 15.87 was obtained in December 2015 and the least value of 5.06 was obtained in April 2016. The coeffcient of determination obtained for the period of study shows that total suspended particulate (TSP) had the highest effect on the variation of AQI with the value of 87.3%, while temperature with value 1.8% had the least effect on the variation of AQI within the study period. The AQI calculated from the individual pollutants showed that Ozone had the highest value of 18.75 in December 2015 and its least value of 7.81 in March 2016. Carbon monoxide (CO) had the highest value of 29.7 in September 2016 and its least value of 6.06 in April 2016. Sulphur dioxide (SO 2 ) had the highest value of 22.06 in July 2016 and August its least value of 8.8 in December and January 2016. NOx had the highest value of 93.75 in December 2015 and its least value of 0 in April, July, October and November 2016. All the calculated AQI for the individual pollutants were categorized as “Good” except NOx which was categorized as moderate. INTRODUCTION An Air Quality Index (AQI) may be defned as a numerical rating that refects the composite Infuences on overall quality of a number of air quality parameters (Vennapu, 2014). AQI is typically a numerical scale, usually colour coded, intended to convey the likely severity of the adverse health effects at the monitored concentration levels (Cairncross, et al., 2007). Nigeria as a developing country is facing serious air pollution crisis as some major cities have very poor air quality. In Nigeria, Lagos is of particular interest for air pollution studies because of its high population density coupled with intense industrial and commercial activity (Oluyemi and Asubiojo, 2001). Calabar is also gaining attention because of its tourism potentials. The determination of the quality of air is a very important factor in assessing the suitability of the air we breathe. Evaluating Air Quality Index (AQI) is one such method of determining the quality of air in an area (Kumar, et al., 2015). Several Authors have worked on the estimation of AQI such as (Reddy, et al., 2003; Srivastava and Rajasree 2006; Tiwari, 1987; Vennapu, 2014; Kumar, et al., 2015; Murad, et al., 2014; Shivangi, et al., 2015;