Mineral dust

Mineral dust is atmospheric aerosols originated from the suspension of minerals constituting the soil. It is composed of various oxides and carbonates. Human activities lead to 30% of the dust load in the atmosphere. The Sahara Desert is the major source of mineral dust, which subsequently spreads across the Mediterranean (where it is the origin of rain dust) and Caribbean seas into northern South America, Central America, and eastern North America, and Europe. Additionally, it plays a significant role in the nutrient inflow to the Amazon rainforest.[1] The Gobi Desert is another source of dust in the atmosphere, which affects eastern Asia and western North America.

Dust Plumes off Western Africa.

Characteristics

Mineral dust is mainly constituted of the oxides (SiO2, Al2O3, FeO, Fe2O3, CaO, and others) and carbonates (CaCO3, MgCO3) that constitute the Earth's crust.

Global mineral dust emissions are estimated at 1000-5000 million tons per year,[2] of which the largest part is attributed to deserts. Although this aerosol class is usually considered of natural origin, it is estimated that about a quarter of mineral dust emissions could be ascribed to human activities through desertification and land use changes.[3]

Large dust concentrations may cause problems to people having respiratory problems. Another effect of dust clouds is more colorful sunsets.

Saharan dust
Satellite photo of a Saharan dust cloud (2000) over the Eastern Atlantic Ocean.

The Sahara is the major source on Earth of mineral dust (60-200 million tons per year). Saharan dust can be lifted by convection over hot desert areas, and can thus reach very high altitudes; from there it can be transported worldwide by winds, covering distances of thousands of kilometers. The dust combined with the extremely hot, dry air of the Sahara Desert often forms an atmospheric layer called the Saharan Air Layer which has significant effects on tropical weather, especially as it interferes with the development of hurricanes.

Graph linking dust to various coral deaths across the Caribbean Sea and Florida.
Images showing Saharan dust crossing the Atlantic.

There is a large variability in the dust transport across the Atlantic into the Caribbean and Florida from year to year. In some years African dust is observed along much of the East Coast of the United States and is visible in the sky. Due to the trade winds, very large concentrations of mineral dust can be found in the tropical Atlantic, reaching the Caribbean; moreover episodic transport to the Mediterranean region.[4] Saharan plumes can form iberulites (a particular tropospheric aggregation of aerosols) when these plumes travel through North Africa and the eastern North Atlantic Ocean, and often reach the circum-Mediterranean areas of Western Europe. In the Mediterranean region, Saharan dust is important as it represents the major source of nutrients for phytoplankton and other aquatic organisms. Saharan dust carries the fungus Aspergillus sydowii and others.[5] Aspergillus borne by Saharan dust falls into the Caribbean Sea and possibly infects coral reefs with Sea Fan disease (aspergillosis). It also has been linked to increased incidence of pediatric asthma attacks in the Caribbean. Since 1970, dust outbreaks have worsened due to periods of drought in Africa.[6] Dust events have been linked to a decline in the health of coral reefs across the Caribbean and Florida, primarily since the 1970s.[7]

Researchers from Hacettepe University have reported that Saharan soil may have bio-available iron and also some essential macro and micro nutrient elements suitable for use as fertilizer for growing wheat. It has been shown that Saharan soil may have the potential of producing bioavailable iron when illuminated with visible light and also it has some essential macro and micro nutrient elements. In this study the impact of various growth media on development of some bread wheat (Triticum aestivum L.) and durum wheat (Triticum durum L.) cultivars have been investigated. As a four different nutrient media, Hewitt nutrient solution [1], illuminated and non-illuminated Saharan desert soil solutions and distilled water have been utilized. Shoot length (cm.seedling-1), leaf area (cm2 seedling-1) and photosynthetic pigments [chlorophyll a, chlorophyll b and carotenoids, mg ml-1 g fresh weight (g fw)-1] have been determined. The results of this study indicate that, wheat varieties fed by irradiated Saharan soil solution gave comparable results to Hewitt nutrient solution.[8]

Effect on hurricane frequency

According to a NASA article,[9] NASA satellites have shown that "the chilling effect of dust was responsible for one-third of the drop in North Atlantic sea surface temperatures between June 2005 and 2006, possibly contributing to the difference in hurricane activity between the two seasons." There were only 5 hurricanes in 2006 compared with 15 in 2005.

It is known that one of the major factors that create hurricanes is warm water temperatures on the surface of the ocean. Evidence shows that dust from the Sahara desert caused surface temperatures to be cooler in 2006 than in 2005.

Asian dust
Aizuwakamatsu, Japan shrouded in Asian Dust on April 2nd, 2007.
Aizuwakamatsu, Japan with clear skies.

In Eastern Asia, mineral dust events that originate in the Gobi Desert (Southern Mongolia and Northern China) during springtime give rise to the phenomenon called Asian dust. The aerosols are carried eastward by prevailing winds, and pass over China, Korea, and Japan. Sometimes, significant concentrations of dust can be carried as far as the Western United States.[10] Areas affected by Asian dust experience decreased visibility and health problems, such as sore throat and respiratory difficulties. The effects of Asian dust, however, are not strictly negative, as it is thought that its deposition enriches the soil with important trace minerals.

An American study analyzing the composition of Asian dust events reaching Colorado associates them to the presence of carbon monoxide, possibly incorporated in the air mass as it passes over industrialized regions in Asia. Although dust storms in the Gobi desert have occurred from time to time throughout history, they became a pronounced problem in the second half of the 20th century due to intensified agricultural pressure and desertification.

North American dust

Mineral dust originates from several sources on the North American continent including the Southwest, the Great Plains, and Alaska. In the Southwest, dust impacts human health,[11][12] visibility,[13][14] lake productivity,[15] and the rate of snowmelt in the Rocky Mountains.[16] Dust deposition has increased dramatically since the early 1800s compared to the natural background [17][18][19] due to the intensification of human activities.[20]

Relationship to drought

Arid and semi-arid regions are naturally prone to dust emissions.[21] Soil moisture is an important variable controlling dust emissions, along with vegetation cover, wind speed and soil type. Several studies based on modern observations show positive relationships (i.e. increasing drought increases dust) between dust and drought conditions in each dust cycle phase, from emissions,[22] to atmospheric burden,[23] to deposition.[24] However, studies based on paleo records of dust deposition (e.g. using lake sediment) that specifically looked at megadroughts show both increases [19] and no change [18][25] in dust deposition. The study by Routson showed an increase in deposition during megadroughts but used a measure of dust concentration rather than accumulation that is affected by the rate of sedimentation. The Routson study instead used dust accumulation rates and found no difference between dust deposition during drought years and megadroughts and deposition during normal hydroclimate conditions. Instead, they found that dust deposition is more likely controlled by transport mechanisms and sediment supply than by hydroclimate. Similarly, Arcusa found no evidence for higher dust deposition during drought on multi-decadal and centennial scales.[25] They also found that sediment supply played a key role as evidenced from a 60% increase in deposition in the 1800s due to accelerating land disturbance.

See also

References
  1. Koren, I.; Kaufman, Y. J.; Washington, R.; Todd, M. C.; Rudich, Y.; Martins, J. V.; Rosenfeld, D. (2006). "The Bodélé depression: a single spot in the Sahara that provides most of the mineral dust to the Amazon forest" (PDF). Environmental Research Letters. 1 (1): 014005. Bibcode:2006ERL.....1a4005K. doi:10.1088/1748-9326/1/1/014005.
  2. Huneeus, N.; Schulz, M.; Balkanski, Y.; Griesfeller, J.; Prospero, J.; Kinne, S.; Bauer, S.; Boucher, O.; Chin, M.; Dentener, F.; Diehl, T.; Easter, R.; Fillmore, D.; Ghan, S.; Ginoux, P.; Grini, A.; Horowitz, L.; Koch, D.; Krol, M. C.; Landing, W.; Liu, X.; Mahowald, N.; Miller, R.; Morcrette, J. -J.; Myhre, G.; Penner, J.; Perlwitz, J.; Stier, P.; Takemura, T.; Zender, C. S. (2011). "Global dust model intercomparison in Aero Com phase I". Atmospheric Chemistry and Physics. 11 (15): 7781. Bibcode:2011ACP....11.7781H. doi:10.5194/acp-11-7781-2011.
  3. Ginoux, P.; Prospero, J. M.; Gill, T. E.; Hsu, N. C.; Zhao, M. (2012). "Global-scale attribution of anthropogenic and natural dust sources and their emission rates based on MODIS Deep Blue aerosol products". Reviews of Geophysics. 50 (3): RG3005. Bibcode:2012RvGeo..50.3005G. CiteSeerX 10.1.1.295.2808. doi:10.1029/2012RG000388.
  4. Stuut,J-B.,Smalley,I.J.,O'Hara-Dhand,K. 2009. Aeolian dust in Europe: African sources and European deposits. Quaternary International 198, 234-245. doi:10.1016/j.quaint 2008.10.007.
  5. Schlesinger, P.; Mamane, Y.; Grishkan, I. (2006). "Transport of microorganisms to Israel during Saharan dust events". Aerobiologia. 22 (4): 259. doi:10.1007/s10453-006-9038-7. "On a spring clear day, the persisting airborne fungi were Alternaria alternata, Geotrichum candidum, Penicillium chrysogenum, and P. glabrum. However, during two dust events the fungal population was dominated by Alternaria alternata, Aspergillus fumigatus, A. niger, A. thomii, Cladosporium cladosporioides, Penicillium chrysogenum, and P. griseoroseum. This study suggests that Saharan and other desert dust events in the East Mediterranean have a significant effect on the airborne microbial populations, which might impact on health, agriculture, and ecology."
  6. Usinfo.state.gov. Study Says African Dust Affects Climate in U.S., Caribbean. Archived 2007-06-20 at the Wayback Machine Retrieved on 2007-06-10.
  7. U. S. Geological Survey. Coral Mortality and African Dust. Retrieved on 2007-06-10.
  8. Yücekutlu, Nihal; Terzioğlu, Serpil; Saydam, Cemal; Bildacı, Işık (2011)."Organic Farming By Using Saharan Soil: Could It Be An Alternative To Fertilizers?" Hacettepe Journal of Biology and Chemistry. 39 (1): 29–38.
  9. Sharan Dust has chilling effect on North Atlantic
  10. University of Utah Department of Meteorology. Dr. Kevin Perry is quoted in BALTIMORE SUN article, "Blowing in the Wind". Retrieved on 2007-06-10.
  11. Tong, Daniel Q.; Wang, Julian X. L.; Gill, Thomas E.; Lei, Hang; Wang, Binyu (2017-05-16). "Intensified dust storm activity and Valley fever infection in the southwestern United States: Dust and Valley Fever Intensification". Geophysical Research Letters. 44 (9): 4304–4312. doi:10.1002/2017GL073524. PMC 6108409. PMID 30166741.
  12. Goudie, Andrew S. (February 2014). "Desert dust and human health disorders". Environment International. 63: 101–113. doi:10.1016/j.envint.2013.10.011. PMID 24275707.
  13. Trijonis, John (January 1979). "Visibility in the southwest—An exploration of the historical data base". Atmospheric Environment. 13 (6): 833–843. doi:10.1016/0004-6981(79)90274-9.
  14. Li, Junran; Kandakji, Tarek; Lee, Jeffrey A.; Tatarko, John; Blackwell, John; Gill, Thomas E.; Collins, Joe D. (April 2018). "Blowing dust and highway safety in the southwestern United States: Characteristics of dust emission "hotspots" and management implications". Science of the Total Environment. 621: 1023–1032. doi:10.1016/j.scitotenv.2017.10.124. PMID 29102198.
  15. Ballantyne, A. P.; Brahney, J.; Fernandez, D.; Lawrence, C. L.; Saros, J.; Neff, J. C. (2011-09-23). "Biogeochemical response of alpine lakes to a recent increase in dust deposition in the Southwestern, US". Biogeosciences. 8 (9): 2689–2706. doi:10.5194/bg-8-2689-2011. ISSN 1726-4189.
  16. Painter, Thomas H.; Skiles, S. McKenzie; Deems, Jeffrey S.; Brandt, W. Tyler; Dozier, Jeff (2018-01-28). "Variation in Rising Limb of Colorado River Snowmelt Runoff Hydrograph Controlled by Dust Radiative Forcing in Snow". Geophysical Research Letters. 45 (2): 797–808. doi:10.1002/2017GL075826.
  17. Neff, J. C.; Ballantyne, A. P.; Farmer, G. L.; Mahowald, N. M.; Conroy, J. L.; Landry, C. C.; Overpeck, J. T.; Painter, T. H.; Lawrence, C. R. (March 2008). "Increasing eolian dust deposition in the western United States linked to human activity". Nature Geoscience. 1 (3): 189–195. doi:10.1038/ngeo133. ISSN 1752-0894.
  18. Routson, Cody C.; Arcusa, Stéphanie H.; McKay, Nicholas P.; Overpeck, Jonathan T. (2019-07-19). "A 4,500‐Year‐Long Record of Southern Rocky Mountain Dust Deposition". Geophysical Research Letters. 46 (14): 8281–8288. doi:10.1029/2019GL083255. ISSN 0094-8276.
  19. Routson, Cody C.; Overpeck, Jonathan T.; Woodhouse, Connie A.; Kenney, William F. (2016-02-17). Zhu, Liping (ed.). "Three Millennia of Southwestern North American Dustiness and Future Implications". PLOS ONE. 11 (2): e0149573. doi:10.1371/journal.pone.0149573. ISSN 1932-6203. PMC 4757576. PMID 26886350.
  20. Abruzzi, William S. (1995-03-01). "The social and ecological consequences of early cattle ranching in the Little Colorado River Basin". Human Ecology. 23 (1): 75–98. doi:10.1007/BF01190099. ISSN 1572-9915.
  21. Pye, K. (1987). Aeolian Dust and Dust Deposits. London: Academic Press. pp. 63–91. ISBN 978-0-12-568690-7.
  22. Okin, Gregory S.; Reheis, Marith C. (May 2002). "An ENSO predictor of dust emission in the southwestern United States: AN ENSO PREDICTOR OF DUST EMISSION". Geophysical Research Letters. 29 (9): 46–1–46-3. doi:10.1029/2001GL014494.
  23. Achakulwisut, Pattanun; Shen, Lu; Mickley, Loretta J. (2017-11-27). "What Controls Springtime Fine Dust Variability in the Western United States? Investigating the 2002-2015 Increase in Fine Dust in the U.S. Southwest: Controlling factors of western U.S. dust". Journal of Geophysical Research: Atmospheres. 122 (22): 12, 449–12, 467. doi:10.1002/2017JD027208.
  24. Reheis, Marith C.; Urban, Frank E. (June 2011). "Regional and climatic controls on seasonal dust deposition in the southwestern U.S." Aeolian Research. 3 (1): 3–21. doi:10.1016/j.aeolia.2011.03.008.
  25. Arcusa, Stephanie H; McKay, Nicholas P; Routson, Cody C; Munoz, Samuel E (2019-09-18). "Dust-drought interactions over the last 15,000 years: A network of lake sediment records from the San Juan Mountains, Colorado". The Holocene: 095968361987519. doi:10.1177/0959683619875192. ISSN 0959-6836.
  • Kubilay and Saydam, "Trace elements in atmospheric particulates over the Eastern Mediterranean: concentration, sources, and temporal variability", Atmospheric Environment 29, 2289-2300 (1995).
  • Morales, "The airborne transport of Saharan dust: a review", Climate Change 9, 219-241 (1986).
  • Loyë-Pilot et al., "Influence of Saharan dust on the rain acidity and atmospheric input to the Mediterranean", Nature 321, 427-428 (1986).
  • Sokolik and Toon, "Direct radiative forcing by anthropogenic airborne mineral aerosols", Nature 381, 681-683 (1996).
  • Tegen and Fung, "Contribution to the atmospheric mineral aerosol load from land surface modification", Journal of Geophysical Research 100, 18707-18726 (1995).
This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.