Stratospheric dust

The microscopic particles are small enough to rise into the upper troposphere (up to 10 km above the surface of the Earth) and into the stratosphere (10-50 km above the surface) where they may reside for several years before they are eventually removed by meteoric precipitation. During their residence in the stratosphere the microscopic dust particles are transported widely over the Earth. The stratospheric dust particles in the Antarctic and Greenland ice cores are insoluble in water and are composed of clay minerals (Thompson 1977a, b Kumai 1997) and x-ray amorphous oxides and hydroxides aU of which were presumably derived from soil and regohth exposed in deserts and around receding ice sheets at the end of the Pleistocene. 

The larger dust particles (2-80 pm) are composed primarily of volcanic glass and enclosed minerals that were erupted explosively by volcanoes in Antarctica, on the surrounding volcanic islands, and at more distant locations in Indonesia and in South and Central America. These kinds of particles occur in diffuse layers of volcanic ash that was deposited on the ice sheets of East and West Antarctica. The morphology and chemical composition of volcanic particles have been used to identify their sources and to obtain information about the 

The first ice cores from East Antarctica that were available for the study of stratospheric dust were drilled at South Pole in 1974 (Thompson, E.M. 1979) and at Dome C in 1977/78. The South-Pole core was 101 m long and extended 900 years into the past. The seasonal accumulation and resulting stratigraphy of snow at South-Pole Station was described by Gow (1965), whereas Thompson and Mosley-Thompson (1981) published a profile of dust concentrations in the core. 

The study of microparticles in Antarctic ice cores by L.G. Thompson and E. Mosley-Thompson at The Ohio State University (Thompson et al. 1975, 1981 Thompson 1977a, b Mosley-Thompson 1979 Thonpson and Mosley-Thompson 1981) indicated that the concentration of dust particles in ice cores from the South Pole and Dome C in East Antarctica, from Byrd Station in West Antarctica, as well as from Camp Century in northwestern Greenland have certain common characteristics identified in Table 17.13. The conclusions that are derivable from the data include  

The Holocene ice in Greenland is about three times dustier than ice of equivalent age in Antarctica. 

---

Hudson, B., Flynn, G. J., Fraundorf, P., Hohenberg, C. M., Shirck, J. (1981) Noble gases in stratospheric dust particles Confirmation of extraterrestrial origin. Science, 211, 383-6. 

In 1983, the first ahempts to use the ion probe for D/H ratio measurements were made on meteoric samples and stratospheric dust. In 1991, an analytical procednre was... 

De Luim J.J., Dutton E.G., Coulson K.L., DeFoor T.E. and Mendonca B.G., On some radiative features of the El Chichon volcanic stratospheric dust cloud and a cloud of unknown origin observed at Mauna Loa. J. Geophys. Res., 88, 6769-6772 (1983). 

McKeegan KD (1987) Oxygen isotopic abundances in refractory stratospheric dust particles proof of extraterrestrial origin. Science 237 1468-1471... 

Proceedings of 47th Denver X-ray Conference 47 122 Rost D, Stephan T, Jessberger EK (1999) Surface analysis of stratospheric dust particles. Meteoritics and Planet. Sci 34 637-646... 

Despite rather obvious scepticism, a search for traces of the above isotopes was conducted in the natural environment. Materials chosen for analysis were a sample of mostly stratospheric dust (about 120 g) trapped in cabin filters of the two Boeing 767 airliners exploited on the north Atlantic routes between central Europe and east coast of America. This formed our sample 1. Second sample (sample 2) used for background study was approximately 10 g of a spent Dowex-1 resin, previously used for Pu analysis in environmental samples. Since we used approximately 0.3 g of resin/sample the resin we collected originated from about 30 analyses, so it had contact with about 300 g of dissolved soil ashes (typical ignited soil sample weight is 10 g). 

Figure 3 Alpha spectrum of Ds fraction (with Pt, Au, Po isotopes) of stratospheric dust, obtained during 134 days measurement. Upper part displays the high-energy part of spectrum with linear vertical scale, lower pari shows whole spectrum in logarithmic scale (discriminated at 20 counts level) expanded high energy part is marked with black arrows. Vain arrows indicate the positions of searched peaks.

Fig. 8. A porous interplanetary dust particle collected in the stratosphere. The particle is 10 ]lni across and is composed of anhydrous...

Denmark 1.5 days after the explosion. Air samples collected at Roskilde, Denmark on April 27-28, contained a mean air concentration of 241Am of 5.2 pBq/m3 (0.14 fCi/m3). In May 1986, the mean concentration was 11 pBq/m3 (0.30 fCi/m3) (Aarkrog 1988). Whereas debris from nuclear weapons testing is injected into the stratosphere, debris from Chernobyl was injected into the troposphere. As the mean residence time in the troposphere is 20-40 days, it would appear that the fallout would have decreased to very low levels by the end of 1986. However, from the levels of other radioactive elements, this was not the case. Sequential extraction studies were performed on aerosols collected in Lithuania after dust storms in September 1992 carried radioactive aerosols to the region from contaminated areas of the Ukraine and Belarus. The fraction distribution of241 Am in the aerosol samples was approximately (fraction, percent) organically-bound, 18% oxide-bound, 10% acid-soluble, 36% and residual, 32% (Lujaniene et al. 1999). Very little americium was found in the more readily extractable exchangeable and water soluble and specifically adsorbed fractions. 

Tihe atmosphere contains many radionuclides which result from nuclear weapons testing and from natural processes. The nuclear weapons-produced radionuclides include both fission products and activation products from the construction materials of the device. The natural radionuclides include the decay products of radon and thoron, the natural radionuclides in the airborne dust, and the cosmic-ray-produced radionuclides which result from spallation reactions in the atmosphere. Through the determination of the absolute and relative concentrations of this wide spectrum of radionuclides, it should be possible to define the rates of both the long term stratospheric processes and the shorter term tropospheric processes. At the beginning of 1962 a ground-level... 

A maximum of 47% of the total chromium in ferrochrome smelter dust may be bioavailable as indicated by acid/base extraction. About 40% of the bioavailable chromium may exist as chromium(VI), mostly in the form of Cr207"2 or Cr04"2 (Cox et al. 1985). There are no data in the reviewed literature indicating that chromium particles are transported from the troposphere to the stratosphere (Pacyna and Ottar 1985). By analogy with the residence time of general particles with mass median diameters similar to that of chromium, the residence time of atmospheric chromium is expected to be <10 days (Nriagu 1979). 

In addition to meteorites, three other important types of extraterrestrial material are available for analysis interplanetary dust particles (IDPs), micrometeorites, and Stardust samples. Interplanetary dust particles are collected in the stratosphere by high-altitude research aircrafts. Most of these samples are smaller than 20 pm in diameter, although some of the highly porous cluster particles probably exceeded... 

---