The long-term assessment of air quality on an island in Malaysia

This study aims to evaluate the air quality on Langkawi Island, a famous tourist destination in Malaysia, using 13 years of data (1999-2011) recorded by the Malaysian Department of Environment. Variations of seven air pollutants (O₃, CO, NO, NO₂, NO_x, SO₂ and PM₁₀) and three meteorological factors (temperature, humidity and wind speed) were analysed. Statistical methods used to analyse the data included principal component regression (PCR) and sensitivity analysis. The results showed PM₁₀ was the dominant air pollutant in Langkawi and values ranged between 5.0 μg m^-3 and 183.2 μg m^-3. The patterns of monthly values showed that the concentrations of measured air pollutants on Langkawi were higher during the south-west monsoon (June-September) due to seasonal biomass burning activities. High CO/NO_x ratio values (between 28.3 and 43.6), low SO₂/NO_x ratio values (between 0.04 and 0.12) and NO/NO₂ ratio values exceeding 2.2 indicate the source of air pollutants in this area was motor vehicles. PCR analysis grouped the seven variables into two factor components: the F1 component consisted of SO₂, NO and NO_x and the F2 component consisted of PM₁₀. The F1 component (R² = 0.931) indicated a stronger standardized coefficient value for meteorological variables compared to the F2 component (R² = 0.059). The meteorological variables were statistically significant (p < 0.05) in influencing the distribution of the air pollutants. The status of air quality on the island could be improved through control on motor vehicle emissions as well as collaborative efforts to reduce regional air pollution, especially from biomass burning.