Air Quality Impact from Petroleum Refinery at Sapugaskanda, Sri Lanka

Abstract

Abstract Being the single largest oil refinery in Sri Lanka and located in an area of mixed land use, the petroleum refinery at Sapugaskanda deserves proper investigation to evaluate the possible impacts on the ambient air quality in the surroundings. The objectives of this study were to (1) measure ambient air quality concerning sulfur dioxide (SO2), nitrogen dioxide (NO2), carbon monoxide (CO), ozone (O3) and particulate matter (PM2.5 and PM10) around the petroleum refinery during major shutdown and normal operation period of the refinery in 2018 (2) identify the compliance concerning the regulated limits (3) investigate the effect of refinery operation or shut down on the concentrations of air pollutants. The results were statistically analyzed. Active monitoring results indicated that normal operation of the refinery are not statistically significantly different from those during the refinery shutdown period (Wilcoxon Signed Ranks Test; for SO2, W = 8, p = 0.094, NO2, W = 11, p = 0.062, O3, W = 7.5, p = 0.125). PM10 and PM2.5 indicated that the ambient concentrations during the refinery shutdown are statistically significantly higher than those during the normal operation period of the refinery (Wilcoxon Signed Ranks Test; W = 1, p = 0.031). According to passive monitoring results, no statistically significant spatial variation of concentrations of SO2 was detected (One-way ANOVA F(4,25) = 1.28, p = 0.30). Temporal variation of concentrations of SO2 was also not statistically significant (One-way ANOVA F(5,24) = 0.44, p < 0.81). For NO2, statistically significant spatial variation of concentrations was not detected (One-way ANOVA F(4,25) = 2.55, p = 0.064). Temporal variation of concentrations of NO2 was also not statistically significant (One-way ANOVA F(5,24) = 0.86, p < 0.51). The measured concentrations were substantially lower than ambient air quality standards established by the Ministry of Environment, Sri Lanka. The maximum concentrations were found 2 km away from the refinery and to the northeast. Air pollutant concentrations can be evaluated over long periods by using the monitoring procedure adopted in this study and hotspots of pollution can be identified. Identification of these hotspots may help to evaluate air quality and to execute proper action plans, especially in locations where industrial and urban pollution coexist.