Slide 1

NATURAL AEROSOLIC MINERAL DUSTS Edward Derbyshire Before and during a Mongolian dust storm Beijing, China, April 2003 2007-2009 Slide 2 Tibet Egypt Mongolia N. Pakistan Karakoram Palaeolakes Debris fans Glacier forelands Yardangs Some common dust sources Slide 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 ( 50 yr ago..autopsy showed high content of fine ( Anxi County, Gansu Province, China DATA on DUST* Outdoor dust concentration (TSP) during storms: 42 mg/m 3 (cf. recurrent outdoor range for this region 21 69 mg/m 3 ) Free silica content in dust: 34 - 61% Total suspended particulates, rural houses: 3.2 mg/m 3 Anxi County, Gansu Province, China DATA on DUST* Outdoor dust concentration (TSP) during storms: 42 mg/m 3 (cf. recurrent outdoor range for this region 21 69 mg/m 3 ) Free silica content in dust: 34 - 61% Total suspended particulates, rural houses: 3.2 mg/m 3 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 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 Impact Case Studies-2 (North China) Slide 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. 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. Slide 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): (a)collected on 4th November, 1998; (b) 23rd March, 1998 and (c) 20th July, 1998. [Singer et al. 2003] Slide 11 Si - abundant to dominant element in Saharan dust 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. 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 [After Prospero 2002] Slide 15 The altitude effect Canary Is. Example of a winter pattern (Sahelian) dust outbreak (26 February15 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] Slide 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] 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] Slide 17 Two Chinese dust sources of global importance Mongolia (pink flow-path) and Taklamakan Basin (yellow flow-path) 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) Slide 18 Dust concentration Description [mg m3] 0.083Normal background 0.356Detachment mode 1.206Extensive dust pall 3.955Ordinary dust storm (Chinese Meteorological Bureau) Slide 19 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] Source-specific properties stable during long-range windborne transport clay mineralogy major or minor elemental ratios rare earth element (REE) abundances Slide 20 On 2627 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] On 2627 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] EVENT-BASED MODELS Slide 21 NMinimumMaxMedianDep. typical Mn (ng/m3)632.121096.0250.14141.69 Fe (g/m3)1010.957.001.985.85 Co (ng/m3)1010.1623.001.132.46 Pb (ng/m3)1011.5144.789.907.83 Cu (ng/m3)1011.7663.9311.6412.90 Cd (ng/m3)1010.012.750.240.40 Mg (/m3)1000.03429.3917.5659.94 Al (/m3)1000.30148.604.4015.06 Ca (/m3)780.23786.1023.82119.56 Na (/m3)1000.27802.4870.84103.81 Cr (ng/m3) [but species critical]411.20154.3818.7229.62 Zn (/m3)790.0111.920.501.36 Ni (ng/m3)380.3231.723.385.71 Ti (/m3)380.050.460.150.09 Cancer Emphysema 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 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 suspectedAsthmaCancer & asthma Other agents no data for Gran Canaria: As (cancer) and V (asthma) Slide 22 Diatoms typical of those deflated from desiccated Saharan- Sahelian dry lake basins, e.g. Aulacoseira granulata Biogenic Silica - common in atmospheric dusts Biogenic Silica - common in atmospheric dusts 15 m Phytolith 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