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NATURAL AEROSOLIC M INERAL DUST S

2007-2009. NATURAL AEROSOLIC M INERAL DUST S. Edward Derbyshire. Before and during a Mongolian dust storm Beijing, China, April 2003. Palaeolakes. Some common dust sources. Tibet. N. Pakistan. Debris fans. Egypt. Yardangs. Karakoram. Glacier forelands. Mongolia.

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NATURAL AEROSOLIC M INERAL DUST S

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  1. 2007-2009 NATURAL AEROSOLIC MINERAL DUSTS Edward Derbyshire Before and during a Mongolian dust stormBeijing, China, April 2003

  2. Palaeolakes Some common dust sources Tibet N. Pakistan Debris fans Egypt Yardangs Karakoram Glacier forelands Mongolia

  3. Impact – Case Studies 1 (Sahara) Non-industrial silicosis (‘Desert Lung’) was found in human lung tissue > 50 yr ago…..autopsy showed high content of fine (<3m) silica dust A radiographic study of 54 Bedouin people in the Negev Desert, showed the incidence of fibrosis to be age related, with progression more notable in women (13 out of 22) than in men (only 4 out of 32), perhaps related to greater exposure to dust in and around family tents. [Bar-Ziv, J, Goldberg, GM. 1974. Simple siliceous pneumoconiosis in Negev Bedouins. Rch. Env. Health 29: 121] Other findings from different parts of North Africa include radiological evidence of multiple micro-nodules scattered throughout the lungs, and considered to be consistent with silicosis.

  4. Impact – Case Studies-1 (Ladakh) Work undertaken in two studies in Ladakh (Norboo et al. 1991; Saiyed et al. 1991) is of particular interest - a region without any mines or industries but in which (like China) dust storms are frequent. Radiographic evidence taken from an equal number of men and women between the ages of 50 and 62 years in two villages (altitudes of 3200m and 3500m) showed important differences resulting from the higher dust concentrations at the lower of the two villages. Several cases of progressive massive fibrosis were found in the lower village, with none in the upper one, suggesting that silicosis may cause appreciable morbidity at lower altitudes. Norboo, T, Angchuk, PT, Yahya, M, Kamat, SR, Pooley, FD, Corrin, B, Kerr, IH, Bruce, N, Ball, KP. 1991. Silicosis in a Himalayan village population: role of environmental dust. Thorax 46: 341-343. Saiyed, HN, Sharma, YK, Sadhu, SG, Norboo, T, Patel, PD, Patel, TS, Venkaiah, K, Kashyap, SK. 1991. Non-occupational pneumoconiosis at high altitude villages in central Ladakh. British Journal of Industrial Medicine 48: 825-829.

  5. Impact – Case Studies-2 Ladakh Mineral dust found on the upper surfaces of wooden roof beams of Ladakhi houses is all <15m, more than 25% by weight being <1m; the silica content is >60%.

  6. Impact – Case Studies-3 (Ladakh) Close correlation between dust storm frequency and number of cases of pneumoconiosis – village with low dust storm frequency: 2.0% of population village with moderate frequency: 20.1% of population village with high dust storm incidence: 45.3% of population The larger of the two Ladakh studies (449 patients older than 50 years: 245 women, 204 men from 3 different villages: Saiyed et al 1991) showed typical cases of pneumoconiosis associated with progressive massive fibrosis and egg-shell calcification of the bronchial glands (indicative of high concentrations of free silica) in 101 cases (22.5% of the population sampled).

  7. Impact – Case Studies-1 North China The large population subjected to frequent dust storms in north China probably includes substantial numbers of people with non-occupational silicosis Hexi Corridor dust pall (ca. 1km thick) over Lanzhou city (pop. 3.5 m), early summer

  8. Impact – Case Studies-2 (North China) Anxi County, Gansu Province, China DATA on DUST* Outdoor dust concentration (TSP) during storms: 42 mg/m3 (cf. recurrent outdoor range for this region 21 – 69 mg/m3) Free silica content in dust: 34 - 61% Total suspended particulates, rural houses: ≤ 3.2 mg/m3 Minghua, Hexi Corridor, China DATA ON PNEUMOCONIOSIS+ Desert margin towns (based on a total of 395 X-radiographs) Incidence in the population in general: 7% Incidence in adults over 40 years of age: >40% Total number of people affected in N. China - unknown

  9. This demands improved understanding of • Dust particle properties – size, shape, mineralogy/geochemistry – laboratory data • Dust sources & pathways – observational data • as a basis for assessment of particle surface reactivity and toxicology • Interest in refining data on these subjects has increased steadily in the past decade, especially for Mid, Central and East Asia, and the peri-Saharan regions.

  10. Particle size 1. Canary Islands Typically, almost 40% of the dust of the calima of March 2004 in Gran Canaria was finer than 10 microns • 2. Dead Sea, Israel • Particle-size distribution of (salt-free) atmospheric deposition over the Dead Sea (Malvern model Mastersizer Laser): • collected on 4th November, 1998; • (b) 23rd March, 1998 and • (c) 20th July, 1998. • [Singer et al. 2003]

  11. Composition Quartz amounts in major dust storms are very similar (60.95% in North Africa), closely matching the global value (58.98%) Si - abundant to dominant element in Saharan dust <10µm Composition Entrainment of material < 2 µm Silt-size aggregates of clay grade particles. Clay grades are detached and transported as aggregates, not as single grains.

  12. Quantitative Mineralogy Saharan dust pall, Lanzarote, June 2002 Courtesy of Johann Engelbrecht Rapid, automated analysis using the Bruker D8 XRD system [Courtesy of Johann Engelbrecht]

  13. OBSERVATIONAL DATA Ground-based. Global synoptic atmosphere circulation data and derived models. Orbital data. LIDAR (Light Detection and Ranging)

  14. Mean number of ‘dust days’ (defined as reduction in visibility by dust to < 1km) 80 in south-west Asia >60 in Turkmenistan and the Karakum >45 in Kazakhstan >30 in the Tarim Basin (Taklamakan), the Hexi Corridor and the Loess Plateau (China) ~30 in parts of North Africa ~20 in the NW Indian sub-continent >15 in central Australia. [after Middleton et al. 1986] after Prospero 2002 The long-term global dust storm frequency shows a distribution of major sources closely similar to other data sources - sources occur in all continents except Europe and Antarctica. [After Prospero 2002]

  15. The altitude effect Canary Is. Example of a “winter pattern” (Sahelian) dust outbreak (26 February–15 March 2000). ambient PM10 levels (TSP). SeaWIFS image &TOMS aerosol index map Dominant meteorological scenario during the winter Sahelian dust outbreaks; 925 and 850 hPa pressure levels, 26 Feb. 2000, 1200 h. [Viana et al. 2002]

  16. Backward trajectory at mid-point of calima of 3 – 8 March 2004 - track across NW Sahara suggestive of summer half-year pattern. However, estimated thickness of dust pall on Gran Canaria and Tenerife only 1 to 1.5 km (i.e. low altitude) is consistent with winter half-year mode, however. [courtesy of Denis D. Rousseau]

  17. Two Chinese dust sources of global importance – Mongolia (pink flow-path) and Taklamakan Basin (yellow flow-path) Dust carried by both airstreams has been recognised in Greenland ice cores…. …..and in the snows of the French Alps (>20,000km pathway)

  18. Dust concentration Description [mg m3] 0.083 Normal background 0.356 ‘Detachment mode’ 1.206 Extensive dust pall 3.955 Ordinary dust storm (Chinese Meteorological Bureau)

  19. Source-specific properties stable during long-range windborne transport • clay mineralogy • major or minor • elemental ratios • rare earth element • (REE) abundances • Sr, Nd and Pb • isotope ratios • (isotope composition • varies with the PSD in • some dust samples, • so PSD measurement • is necessary) • [after Grousset & Biscaye 2005]

  20. EVENT-BASED MODELS On 26–27 March 2003, 50% of the dust particles in Japan came from North Africa, about 30% from the Middle East, and only about 10% from China in the boundary layer. This simulated result is consistent with polarization lidar and sky radiometer observations. [Tanaka et al 2005]

  21. Gran Canarian Dust - Trace Aerosol Composition (at Taliarte site – near sea level) Links between selected elements in Saharan dust and some known lung function conditions and diseases Cancer Cancer suspected Cancer & asthma Emphysema Asthma Other agents – no data for Gran Canaria: As (cancer) and V (asthma)

  22. Biogenic Silica - common in atmospheric dusts Testate amoeba Organic tracers - phytoliths, lacustrine diatoms, pollen, etc. – indicate a continental origin and possibly a specific Climate area – but may not indicate precise source of dust pall Phytolith 15 µm Diatoms typical of those deflated from desiccated Saharan-Sahelian dry lake basins, e.g. Aulacoseira granulata

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