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Dust Flux (dust + flux)

Distribution by Scientific Domains

Earth and Environmental Science	50%

Selected Abstracts

Aeolian dust dynamics in agricultural land areas in Lower Saxony, Germany

EARTH SURFACE PROCESSES AND LANDFORMS, Issue 7 2001
Dirk Goossens
Abstract The dynamics of fine aeolian dust emitted from agricultural land was investigated over 15 months near Grönheim, Lower Saxony, Germany. The following aspects were studied: airborne dust concentration, the ratio of mineral versus organic dust, the vertical distribution of the particles in the atmosphere, horizontal and vertically integrated horizontal dust flux, vertical dust flux, dust deposition at ground level, grain-size distribution of the mineral dust component, and vertical distribution of organic matter in the dust. Standard meteorological parameters (wind speed and direction, precipitation) were measured as well. Dust activity in Grönheim is high in spring (March,May) and autumn (October,November) and low to very low during the rest of the year. There is a strong relationship between the periods of tillage and the intensity of dust activity. Also, there is high dust activity during wind erosion events. For the year 1999, dust emission due to tillage was 6·6 times higher than dust emission due to wind erosion. A dust transport of 15·8 ton km,1 a,1 was calculated for the first 10 m of the atmosphere in 1999. Total dust transport (in the entire mixing layer) was estimated between 16 and 20 ton km,1 a,1. About 25,30 per cent of this dust is mineral dust, emitted from the fields during tillage or during wind erosion events. In spring and autumn there is a strong vertical stratification in the airborne sediment, with much (coarse) dust in the lower air layers and significantly less (and finer) dust at higher altitudes. In summer and winter, when there is no local dust production, there is no stratification: equal amounts of dust are transported at all heights. The stratification in spring and autumn is exclusively caused by the mineral part of the dust. The organic particles are much better mixed in the atmosphere because of their lower density. Copyright © 2001 John Wiley & Sons, Ltd. [source]

Characteristics of cometary dust tracks in Stardust aerogel and laboratory calibrations

METEORITICS & PLANETARY SCIENCE, Issue 1-2 2008
M. J. Burchell
An optical scan of the entire collector surface revealed 256 impact features in the aerogel (width >100 ,m). Twenty aerogel blocks (out of a total of 132) were removed from the collector tray for a higher resolution optical scan and 186 tracks were observed (track length >50 ,m and width >8 ,m). The impact features were classified into three types based on their morphology. Laboratory calibrations were conducted that reproduced all three types. This work suggests that the cometary dust consisted of some cohesive, relatively strong particles as well as particles with a more friable or low cohesion matrix containing smaller strong grains. The calibrations also permitted a particle size distribution to be estimated for the cometary dust. We estimate that approximately 1200 particles bigger than 1 ,m struck the aerogel. The cumulative size distribution of the captured particles was obtained and compared with observations made by active dust detectors during the encounter. At large sizes (>20 ,m) all measures of the dust are compatible, but at micrometer scales and smaller discrepancies exist between the various measurement systems that may reflect structure in the dust flux (streams, clusters etc.) along with some possible instrument effects. [source]

Opportunities for the stratospheric collection of dust from short-period comets

METEORITICS & PLANETARY SCIENCE, Issue 11 2002
Scott MESSENGER
These comets have had the rare characteristics of low eccentricity, low inclination orbits with nodes very close to 1 AU. Dust from these comets is directly injected into Earth-crossing orbits by radiation pressure, unlike the great majority of interplanetary dust particles collected in the stratosphere which spend millennia in space prior to Earth-encounter. Complete dust streams from these comets form within a few decades, and appreciable amounts of dust are accreted by the Earth each year regardless of the positions of the parent comets. Dust from these comets could be collected in the stratosphere and identified by its short space exposure age, as indicated by low abundances of implanted solar-wind noble gases and/or lack of solar flare tracks. Dust from Grigg-Skjellerup probably has the highest concentration at Earth orbit. We estimate that the proportion of dust from this comet will reach at least several percent of the background interplanetary dust flux in the >40 ,m size range during April 23,24 of 2003. [source]

The development and application of luminescence dating to loess deposits: a perspective on the past, present and future

BOREAS, Issue 4 2008
HELEN M. ROBERTSArticle first published online: 28 AUG 200
Loess deposits preserve important records of Quaternary climate change and atmospheric dust flux; however, their full significance can only be revealed once a reliable chronology is established. Our understanding of loess-palaeosol sequences and the development of luminescence dating techniques have progressed hand-in-hand over the past 25 years, with each subject informing the advancement of the other. This article considers the development and application of luminescence dating techniques to loess deposits from the early days of thermoluminescence (TL) to the optically stimulated luminescence (OSL) methods utilized today. Recent technological and methodological advances have led to a step-change in the accuracy and precision of quartz OSL ages; this has led to an expansion of high-resolution luminescence studies, which in turn are informing loess studies and challenging some of the basic ideas regarding the nature of loess records, their formation and their significance. Future luminescence research efforts are likely to focus on extending the age range of luminescence techniques, possibly by utilizing new luminescence signals; this, again, will allow investigation of the long-term variability of loess records in comparison with other long records of climate change to which they are frequently compared. [source]