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

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

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.

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

Outline Introduction Methods Results and Discussion

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

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

PM samplers Tsinghua Chegongzhuang PM10: TEOM since Sep’00 Low-flow rate 0.4L/min Sampling interval 7 days PM10: TEOM since Sep’00 PM2.5 since Jul’99 Final.ppt

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

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

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

Outline Introduction Methods Results and Discussion

March 20 2002

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

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 PM10 747 µg/m3 On 4/27, PM10 rose to > 400 µg/m3 in Taiwan Final.ppt

Dust week vs. non-dust week (DW/LW) － water soluble ions Dust storm Non-dust storm Mass conc. 2001-2002 Anthropogenic ions (SO42-、NO3-、NH4+ 、Cl-): down 48-70% Crustal-related ions (F-、Na+、Mg2+、Ca2+): up 70-80% Final.ppt

Soil dust (reconstructed) adding 16% of the oxides mass to account for other compounds Weekly conc.: 4-39 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] + 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% Final.ppt

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

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

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

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

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

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

Mineralogy of Asian dust particles

Mineralogy of Asian dust particles

Clay mineral composition of ADS

Clay mineral composition of ADS

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.

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.

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