Modeling Study of PM2.5 Source Apportionment over the Caofeidian Industrial Zone and Surrounding Areas

The impacts on air quality and source apportionment of PM2.5 in Beijing-Tianjin-Hebei region during the autumn and winter of 2016 after the establishment of the Caofeidian industrial zone were investigated using the nested air quality prediction modeling system (NAQPMS). The model results agreed well with the observed PM2.5_{concentrations and meteorological factors．The local emission of Caofeidian was one of the main contributors of PM2.5, and its average percentages in winter and autumn were 17.8% and 25.8%, respectively. The results showed that Caofeidian was mainly affected by short-distance neighbor transport when the PM2.5 concentrations were under 75 μg/m³, and the total contributions from Tangshan and Tianjin reached 23%-53%. However, when the PM2.5 concentrations in Caofiedian were above 75 μg/m³, the contributions from long-distance transport, which were mainly from central and southern Hebei, became dominant. In general, the Caofeidian industrial zone had a relatively small PM2.5 contribution to the surrounding areas. The contributions from Caofeidian only accounted for 3%-7% in Tangshan and Tianjin and were almost negligible in the remaining land areas. During pollution episodes, the emission of primary particulate matter significantly decreased, while the contributions from secondary-production increased, including inorganic salts and organic aerosols in PM2.5, compared with those during good air quality period. The contribution of secondary sulfate in Caofeidian area in autumn was 22% on average, which was significantly higher than that in winter. Therefore, while focusing on reducing the primary emission of PM2.5 in Beijing-Tianjin-Hebei areas, controlling SO2 and NOx can also effectively improve the air quality in this region}