Atmospheric PM_2.5 near an Urban-Industrial Complex during Air-pollution Episodes with Various Meteorological Conditions

This study investigates the atmospheric fine particulate matter (PM_2.5) issue caused by the multi-effect of complicated sources, terrain, and meteorology at Southern Taiwan. Three sampling stations represent an urban, a rural, and a coastal sites near an urban-industrial complex. The atmospheric PM_2.5 were measured during a pollution episode from November to February, when the reference samples were collected in April. The sample was collected with a constant-flow sampler with the Federal Reference Method performance. After determining the PM_2.5 mass, their chemical compositions of ions, metals, and carbons were analyzed for the different properties caused by the multi-factors. The chemical mass balance (CMB) model was employed to evaluate the emission contributions. Additionally, an inverse trajectory model is used to analyze the pollutant transport and support the CMB results. The air-pollution episodes occurred within the winter to spring. The PM_2.5 were composed of 51–69% ions, 18–31% carbonaceous species, and 1.5–3.0% metals. The SO₄^2–, NH₄⁺, and NO₃^– contributed 92–96% of the ions. Most of the organic/elemental carbon ratios were low, suggesting more primary carbon emissions. The metal contents were minor and dominated by Fe and Zn. The CMB model indicated the PM_2.5 were dominated by 24% secondary SO₄^2–, 14.7% traffics, 8.3% petrochemical emissions, 6.8% soil dust, and 4.5% sintering plant emission. For non-episode days, the PM_2.5 were contributed by 34.9% traffics, 30% the secondary SO₄^2-, 10.3% secondary NO₃^-, and 6.8% soil dust. Nevertheless, the frequent sea-land breeze might lead to more powerful wind eddies and bring the primary PM_2.5 and the aerosol precursors from the emission areas. Consequently, the uncontrollable meteorological changings would lead to the pollution issues at the lowly convective area. Therefore, the averaging emissions of the PM_2.5 and precursors should be lowered; meanwhile, the rapid controls of the primary emissions are suggested when the high-level PM_2.5 are forecasted.