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Chemical and mineralogical compositions of Asian dust particles

Chemical and mineralogical compositions of Asian dust particles. SHI Zongbo, HE Kebin, MA Yongliang, YANG Fumo Tsinghua University April 4, 2005. Outline. Introduction Methods Results and Discussion. Outline. Introduction Methods Results and Discussion. Asthma symptoms. Hospital

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Chemical and mineralogical compositions of Asian dust particles

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  1. Chemical and mineralogical compositions of Asian dust particles SHI Zongbo, HE Kebin, MA Yongliang, YANG Fumo Tsinghua University April 4, 2005

  2. Outline • Introduction • Methods • Results and Discussion

  3. Outline • Introduction • Methods • Results and Discussion

  4. Asthma symptoms Hospital admissions Death 20 15 % change in health effect indicators 10 Peak flow reduction 5 100 200 300 400 Change in PM10 daily concentrations (microgram/m3) air Impacts of aerosol particles Human Health Climate Visibility

  5. Why individual particles? • Interpreting environmental and health effects of aerosols from bulk rather than individual-particle analyses is like interpreting mortality reports in a war zone from bulk airborne lead concentrations rather than from bullets (Buseck et al., 1999; PNAS). • Briefly, individual particle analysis could provide us with important information that could not be given by the bulk analysis.

  6. What singe particle analysis tell us? Composition Morphology Image analysis Size distribution Mixing state Atmospheric process “fingerprints” Health and climate effect Sources

  7. Outline • Introduction • Methods • Results and Discussion

  8. Sample collection Samples were collected on polycarbonate filters Our samples were collected with R&P PM10 selective head

  9. PM sampling locations Two sampling sites: 10km apart • Chegongzhuang (CGZ) • Tsinghua Univ. (THU) THU CGZ

  10. PM samplers • Low-flow rate • 0.4L/min • Sampling interval • 7 days Tsinghua Chegongzhuang PM10: TEOMsince Sep’00 PM2.5sinceJul’99

  11. Specimen preparation Filter 20nm Au/Pd or 20nm carbon Copper washer Araldite SEMstub a. b. c.

  12. Field Emission Gun-Environmental Scanning Electron Microscopy (FEI)-thin-window Energy Dispersive X-ray Spectrometry

  13. Image Analysis System Number size distribution Number percentage

  14. Outline • Introduction • Methods • Results and Discussion

  15. March 20 2002

  16. Conc. PM10 conc. Conc. Date (month-day/2000) Date (month-day/2002) PM10 conc. PM10 conc. Time (day-hour) Time (day-hour) Temporal PM10 Daily variations Hourly variations

  17. Trace Crustal and trace elements (99’-00’) Crustal • DS week: 4/25 saw a serious dust event with PM10 747 µg/m3 • On 4/27, PM10 rose to > 400 µg/m3 in Taiwan

  18. Dust storm Non-dust storm Mass conc. Dust week vs. non-dust week (DW/LW)－ water soluble ions Anthropogenic ions (SO42-、NO3-、NH4+ 、Cl-): down 48-70% Crustal-related ions (F-、Na+、Mg2+、Ca2+): up 70-80%

  19. Soil dust (reconstructed) • [dust] = 2.20[Al] + 2.49[Si] + 1.63[Ca] + 2.42[Fe] + 1.93[Mg] (K/Fe = 0.6) • Soil: Annual 13 µg m-3,11%; Spring 21 µg m-3, 19%; DW, 39 µg m-3, 42%

  20. Morphology of typical particles collected during Asian dust storm (ADS) episode Spherical coal fly ash Chain-like soot aggregates Irregular mineral

  21. Overview of ADS particles ADS particles collected in Beijing were mainly composed of irregularly shaped minerals.

  22. Chemical compositions of single ADS particles K-feldspar Plagioclase Clay Quartz Aluminosilicate/gypsum Aluminosilicate/dolomite Aluminosilicate/Fe oxide Aluminosilicate/calcite

  23. Mixing state of ADS particles by chemical mapping and EDX analysis Aluminosilicate/gypsum Aluminosilicate/Fe oxide Aluminosilicate/calcite

  24. Number percentages of different types of mineral particles collected during a dust episode No sulfur or low sulfur + Except Na2SO4, all other S-containing particles are associated with Ca Thus, at least some of the sulfur was from processes in the source region. 30% of particles are mineral aggregates

  25. Number size distribution and percentages of different types of particles collected during and after a dust episode

  26. Mineralogy of Asian dust particles

  27. Mineralogy of Asian dust particles

  28. Clay mineral composition of ADS

  29. Clay mineral composition of ADS

  30. Summary • ADS particles collected in Beijing were mainly composed of irregularly shaped minerals. More than 50% of ADS particles were larger than 1mm in ESD. • About 30% of ADS particles are mineral aggregates. • Sulfur in some of the ADS particles was originated from processes in the source region.

  31. Summary • PM10 samples collected during the severe dust storm episodes were characterized by the absence of dolomite, high quartz/clay ratio as well as dominance of illite/smectite mixed layers in clay mineral species. • Dust event was a important contributor to PM2.5 concentration and composition in the spring.

  32. Thanks!

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