Investigation of nighttime ground level ozone concentrations in industrial and rural area

Ground level ozone (O3) is the most pervasive global air pollutant due to its adverse effect on human health and crop yields. In this study, the variation of nighttime ground level ozone concentration was determined in Jeli, Kelantan and Kemaman, Terengganu. The concentration and the variation of nighttime O3, NO2, NO and meteorological factors were determined using the descriptive analysis and time-series analysis. Besides that, the mechanism of nighttime O3 removal chemistry was investigated using the diurnal plot. The most significance factor to enhance the nighttime removal chemistry was identified using multiple linear regression (MLR). The MLR model was used to fit the observed data obtained from monitoring sites. The study showed the nighttime O3 concentration in Jeli was lower than that for Kemaman due to the high efficiency of NOx titration. Over the monitoring period, the highest nighttime O3 concentration recorded was 35.87 and 150 ppb in Jeli and Kemaman, respectively. The presence of nighttime O3 removal reaction in Jeli contributed to the low O3 concentration. In contrast, the low rate of nighttime O3 removal reaction in Kemaman probably due to low NO2 and NO concentrations as the main factor to control the nighttime O3 removal chemistry. The R2 for primary and secondary data was moderate (0.73 and 0.67), indicating the selected variables have explained more possibilities in the variation of O3 concentrations.