| dc.description.abstract | Aerosol metal elements frequently act as tracers in source identification. The study uses the data of “PM2.5 chemical composition monitoring and analysis study” in 2017 to investigate the variations of PM2.5 mass concentration, metal element compositions at the six stations of Banqiao (BQ), Zhongming (ZM), Douliu (DL), Chiayi (CY), Xiaogang (XG), and Hualien (HL). Enrichment factor (EF) coupling with the coefficient of determination between pairs of the metal elements was first adopted to infer source contributions. Secondly, the ratios of the selected metal elements, lanthanoid triangular plots, and Conditional Bivariate Probability Function (CBPF) were for the inferences on the contributions from the refinery, fuel burning, traffic emissions, and ship emissions. Thirdly, Positive Matrix Factorization (PMF) combining with Conditional Probability Function (CPF) was used to quantify source contributions.
The results showed that PM2.5 mass concentrations of the monitoring stations varied from high to low in the order of XG > DL > CY > ZM > BQ >HL. The high to low order of the total metal element concentrations were roughly the same. The dominant metal elements in mass concentration are Na, K, Fe, Ca, Al, Mg, and Zn. The average concentrations of Pb, Ba, and Ga at the CY station and Na, Fe, Al, Mg, and Zn at the XG stations were the highest of each element in the six stations. In terms of spatial source distribution, the metal elements with similar contributing sources for DL and CY stations were the most in the six stations. The metal elements of Tl, Rb, and Cs were with similar contributing sources at the ZM, DL, and CY stations.
All stations were obviously under the influences of winds from traffic emissions. The BQ, DL, XG, and HL stations were additionally subject to the influences of fuel oil burning. As for the influence from oil refinery emissions, the south and southeast winds to the XG station were responsible for it. The daily average of La/PM2.5 ratio increased much when affected by oil refinery emissions. Meanwhile, the hourly values of SO2 also went high. Since the XG and HL stations near a harbor, ship emissions affect them significantly when the winds coming from the harbor. The metal elemental ratios of V/Ni and La/Ce were in the ranges of ship emission characteristics, and SO2 concentration rose accordingly with evident peak values when under the influence of ship emissions.
In summarizing the results from the methods of determination coefficient, the metal elemental ratio, and PMF source apportionment, all the six stations were significantly affected by traffic emissions, mineral industry, and biomass burning. In particular, the steel industry influenced the BQ, ZM, CY, and XG stations evidently. The DL and HL stations were under the influences of coal combustion and coal-fired power plants, while the ZM, CY, XG and HL stations were subject to the influences of fuel oil combustions. | en_US |