Real-time geochemistry of urban aerosol during a heavy dust episode by single-particle aerosol mass spectrometer: Spatio-temporal variability, mixing state and spectral distribution_中国颗粒学会

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Partic. vol. 53 pp. 197-207 (December 2020)
doi: 10.1016/j.partic.2020.02.001

Real-time geochemistry of urban aerosol during a heavy dust episode by single-particle aerosol mass spectrometer: Spatio-temporal variability, mixing state and spectral distribution

Lijuan Shena, Feng Haob, Meng Gaoc, Honglei Wanga,d,*, Bin Zhua, Jimei Gaob, Yufei Chengb, Fei Xieb

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hongleiwang@nuist.edu.cn

Highlights

    • SPAMS were simultaneously observed in Hohhot and Nanjing. • Dust intensity (impacted time) weakened (lengthened) with extension of transport distance. • Spectrum peak was 0.12 μm larger in the dust episode of Nanjing. • Proportions of EC-secondary and EC-nitrate particles decreased in the dust episode.

Abstract

A heavy dust episode occurred from May 3 to 8, 2017 in China, with an influenced area exceeding 1.63 million km2. In this work, the mixing state of aerosols and their spectral distributions were simultaneously observed in the sand source region of Hohhot and the long-range dust transport region of Nanjing by using a single-particle aerosol mass spectrometer (SPAMS). The duration time of this dust episode was 37–40 h in Hohhot and prolonged to 51–104 h in Nanjing. Totals of 336,135 (Hohhot) and 235,840 (Nanjing) particles in PM2.5 were successfully ionized to identify 10 main particle classes. During this episode, aerosol particles including OCEC (30.65%), K (22.42%), K-CN (17.03%), sodium (9.46%), heavy metal (8.96%), EC-sulfate (3.46%) and Al (3.22%) were prevailing in Hohhot and were dominated by EC-sulfate (22.26%), OCEC (15.21%), heavy metal (11.96%), K (13.68%), sodium (12.27%), Al (10.54%) and EC (9.02%) in Nanjing. The spectral distribution peaked at 0.66 μm during the dust episode in Nanjing, 0.12 μm larger than the peak size in the non-dust episode. Strong signals at −62[NO3]− and −61[HCO3]−/−61[C5H]− for aerosol particles were observed in Hohhot and Nanjing respectively. The proportions of K-CN, sodium, heavy mental, OCEC and EC-sulfate particles in the dust episode of Hohhot were 2.75, 1.41, 1.80, 1.22 and 1.28 times as large as the values in the non-dust episode. For Nanjing, the fractions of EC-sulfate, EC, Al particles in the dust episode were 10.55, 4.65 and 1.46 times higher than values in the non-dust episode. The proportions of EC-secondary and EC-nitrate particles were found to decrease in the dust episode in the two regions.

Keywords

Dust storm; Mixing state; Spectral distribution; Aerosol; SPAMS