Spatial and Temporal Factors of Air Quality in Surabaya City: An Analysis based on a Multilevel Model

The transport sector has been one of the major sectors to worsen the air pollution in Surabaya City. Air pollution concentrations vary across location and time; however, it hasn’t been clarified yet. To fill in this gap, this study examines spatial and temporal variations of air quality based on a multilevel model. The authors use six air quality datasets (NO, NO2, SO2, O3, CO and PM10), from February 2001 to September 2002, measured with interval 30-mins at five monitoring stations which represent land use characteristics at different locations. Therefore, it is hypothesized that high variance of air quality should be observed among stations. To obtain how land use affects the concentration, the authors use monthly data. A multilevel model was estimated by including a group-level predictor (here, refers to stations) and individual (refers to measurement at the same location). Temporal variations were analyzed by introducing seasonal, day-to-day, and peak concentration time variations. The authors note that the shares of locations are small, indicating that the concentrations do not depend on locations. Also, the model result shows that the air quality related to traffic volume (NO2) is generally lower in suburban areas (Sukomanunggal). Moreover, the quality of SO2 and CO is lower in suburban areas indicating low industrial activities. The authors also notice an upward trend of air pollution, indicating the growth of Surabaya's vehicle volumes. Significant interaction between NO, NO2, and O3 was confirmed. The most obvious meteorological impacts on all air pollutants are coming from all factors. There is the necessity in urban planning management to add green spaces as part of efforts to reduce ambient concentrations.