Joint pollution and source apportionment of PM among three different urban environments in Sichuan Basin, China.

The PM were sampled in three different urban environments: (city of) Chengdu, Leshan, and Dazhou, which are located in Sichuan Basin. 8 types of water-soluble ion and 25 types of metal element were measured in each PM sample across the seasons of 2017. The study results suggest that the joint PM pollution among the three cities mainly occurred in autumn and winter, and the air quality of Chengdu and Leshan was largely affected by Dazhou. Overall, the mass concentrations of PM of these three cities exhibited no statistically significant differences. However, Leshan had the highest level of ionic pollution, and the dominant form of inorganic compound in ambient PM was NHNO, and a competitive relationship between form of NHNO and (NH)SO (NHHSO) was found as well. High homology between SO and NO has been observed in all the three cities, and the ratio between [SO] and [NO] indicated that the stationary source contributed the most to ambient PM in Dazhou. The mass concentrations of the total metal elements from the three cities exhibited similar levels, nevertheless, Dazhou had the highest mass fraction of total metal elements in PM. The enrichment factor of each element indicated that the natural source was highly contributory to the crustal elements in PM of all the three cities, whereas Cr, Cu, Se, Mo, Cd, Tl and Bi were primarily originated from anthropogenic source. In addition, the source apportionment of PM suggest that Dazhou had the different factors and factor-contributions comparing with Chengdu and Leshan.