Surface components of PM2.5 during clear and hazy days in Shanghai by ToF-SIMS

- Comparison between the surface compositions of PM2.5 collected on different weather is demonstrated.
- ToF-SIMS results show hazardous metals like lead can only be detected on hazy day.
- Comparison of two different hazy days is demonstrated by ToF-SIMS.

The compositions of atmospheric particles change greatly on hazy days and could threaten human health. In this study, fine mode particles (PM2.5) were collected and divided according to hazy and non-hazy days in Shanghai from December 8th, 2015 to January 12th, 2016. Versatile ToF-SIMS was performed on the samples to reveal chemical information from the surface of PM2.5. Normalized intensities of Na, Mn, K, V, Al, Fe, Ca, Ti, Cl, NOx and ammonia were higher on clear days while peak intensities of detected bromine and sulfur-contained species were much higher on hazy days. Some hazardous species (Pb, Cr, Ni, As, CHS, SO2) and high-mass aromatic hydrocarbon fractions could only be detected by ToF-SIMS from PM2.5 collected on hazy days. Comparison of metallic elements and phthalates implied that haze pollution in Shanghai was mainly the mixing of coal combustion with vehicle emission. In addition, comparison of different haze pollution was also exhibited. Some nitrogen-containing organic compounds were detected only from PM2.5 of December 15th, and ToF-SIMS ion signals of N2H5+, NH4+, CN−, NO2− and NO3− from PM2.5 of December 15th were much more intense, compared with PM2.5 collected on December 25th.