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. Impacts of aerosol particles
Human Health 20 15 10 5
100
200
300
400
Asthma
symptoms
Hospital
admissions
Death
Peak
flow
reduction
Change in PM10 daily concentrations (microgram/m3) air
% change in health effect indicators
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?
Morphology
Composition
Image analysis
Size distribution
Mixing state
Atmospheric process “fingerprints”
Sources
Health and
climate effect

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
Samples were collected on polycarbonate filters

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

10. PM samplers Tsinghua Chegongzhuang PM10: TEOM since Sep’00
Low-flow rate
0.4L/min
Sampling interval
7 days
PM10: TEOM since Sep’00
PM since Jul’99
Final.ppt

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

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

13. Number size distribution
Image Analysis System
Number size distribution
① 导入FESEM分析得到的数字图像文件；
② 确定比例尺；
③ 输入第一类颗粒物的名称，通常为“烟尘集合体(soot aggregates)”；
④ 使用鼠标分别圈出图像中的所有烟尘集合体，并点击“确定”；
⑤ 重复步骤③、④分别处理燃煤飞灰、矿物颗粒和石膏颗粒；
⑥ 点击“确定”后，系统自动将每一颗粒的等效表面积和等效球形直径(Equivalent Spherical Diameter, ESD)等数据按照颗粒物类型导入Microsoft Excel。
⑦ 如此循环，直到处理完10张图像。
Number percentage
Final.ppt

14. Outline
Introduction
Methods
Results and Discussion

15. March

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

17. Crustal and trace elements (99’-00’)
Crustal and trace elements each show co-varied temporal patterns
Like PM2.5, carbon and ions, all peak correspond to several days’ stagnation in the beginning of heating season.
The mass scatting efficiency (MSE) of dust is about 1/4 that of nss-sulfate. The mean MSE of fine soil dust in the DS week was 2.8 times that of fine sulfate and thereby the dominant light scattering aerosol.
DS week: 4/25 saw a serious dust event with PM µg/m3
On 4/27, PM10 rose to > 400 µg/m3 in Taiwan
Final.ppt

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

19. Soil dust (reconstructed)
adding 16% of the oxides mass to account for other compounds
Weekly conc.: µg m-3
In contrast to PM2.5 mass, the concentrations of soil dust rocketed from winter to spring
soil dust contributed less than 10% of PM2.5 mass for most samples collected in the seasons other than spring and much more than this value during most weeks in the spring.
Soil contribution to PM2.5 mass (41.6%) in DW was 3.6 times the annual mean
high PM2.5 concentrations episodes were usually attributed to anthropogenic other than crustal sources
fine mineral particles were distinctly different from anthropogenic fine particles in sources emissions, atmospheric dispersion, and temporal variations
[dust] = 2.20[Al] [Si] [Ca] [Fe] [Mg] (K/Fe = 0.6 )
Soil: Annual 13 µg m-3,11%; Spring 21 µg m-3, 19%; DW, 39 µg m-3, 42%
Final.ppt

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

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

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

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
Individual mineral
Mineral aggregate
Type
Percentage
Quartz
17.8
Si/Al/Ca
12.6
Plagioclase
8.1
Si/Al/Ca/S
5.7
Clay
Illite/Smectite
11.3
Si/Al/Ca/Mg
2.0
Caly
Other
20.2
Si/Al/Fe
3.2
Ca/Si/Mg
Si/Al>3
4.5
Si/Al/Mg
0.8
K-feldspar
7.3
Si/Al/Ti
0.4
Na2SO4
2.4
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

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

27. Mineralogy of Asian dust particles

28. Mineralogy of Asian dust particles

29. Clay mineral composition of ADS

30. Clay mineral composition of ADS

31. 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.

32. 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.

33. Thanks!