Aerosol storms

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. 

The suspension of aerosols during dust storms from the Owens Dry Lake in California has been a subject of great concern to residents in the Owens Valley. 

In order to obtain quantitative data on particulate air quality in the Owens Valley, a study sponsored by the California Air Resources Board was conducted by the Air Quality Group at UCD. The primary objective was to determine the impact of the dry lake bed on the average particulate concentration and on the dust storm particulate concentrations in the valley. In order to accomplish this, it was necessary to determine the elemental composition of the dry lake bed and to determine the average weekly and dust storm concentration of aerosols. 

Weekly monitoring of particulate aerosols began on February 20, 1979, and ended on June 18, 1979. A total of seventeen weeks of monitoring were conducted during this period. Samplers were run for seven consecutive days each week at a flow rate of ten liters per minute, except during dust storm episodes. During dust storms, samples were collected dally at a flow rate of ten liters per minute. Samples during dust storms were collected on April 6,7,16,17,23,24, 1979. 

Effect of Dust Storm Episodes on the Average Weekly Aerosol Concentrations. The total and fine gravimetric mass averaged over all sites for each week, is depicted in Figure 6. The error bars for the Owens Valley curves represent the standard deviation of the mean. The errors on the Mono Lake curve represent the sampling system error of 15%. The mean weekly values do not include the three dust storm episodes sampled separately, but do include several additional dust storms. Table I lists all the dust storms reported by the sampler operators. 

These dust storm aerosol measurements are not Included in the weekly average concentration in Figure 7. 

Figures 4 and 7 indicate the spatial profile of total and fine aerosol mass for the weekly monitoring and the dust storm episode studies, respectively. The total mass concentration peaks at Keeler and declines sharply north of the lake bed.

As an indication of the effect of dust storm episodes on the aerosol concentration in the valley, the per cent Increase in the weekly total mass, coarse sulfur, chlorine, silicon, and iron concentration during a dust storm was computed. In addition, the absolute Increase in these quantities was also computed. The results of this analysis are shown in Table II. These data also indicate that a significant increase in aerosol concentration due to suspended lake bed materials occurs as far downwind as Independence. In order to quantify this effect, the sulfur to iron (S/Fe) and chlorine to iron (Cl/Fe) ratio at each site was examined. At Keeler, all the coarse sulfur and iron measured at the sampling site are suspended from the lake bed. At any site... 

The Owens Lake brine analysis of Table V Indicates that the Na/S ratio should be approximately 3.8 for lake bed materials, which agrees quite well with the ambient ratio measured at Keeler. The above data suggests that airborne sulfur aerosols measured in the Owens Valley are in the form of sulfates which are suspended from the efflorescent crust on the Owens Lake bed. Therefore, if we assume that all the sulfur measured at each site is in the form of sulfate, then during a dust storm, the sulfate standard for the state of California (25pg/m ) is violated near the Owens Lake. It should be noted that the sulfate standard was developed for very fine acidic aerosols. The sulfates measured here are larger and basic particles, so their toxicity may be different from particles for which the standard was written. The calculated sulfate levels at each site during a dust storm are listed in Table VI. 

Reid, J. S., R. G. Flocchini, T. A. Cahill, and R. S. Ruther, Local Meteorological, Transport, and Source Aerosol Characteristics of Late Autumn Owens Lake (Dry) Dust Storms, Atmos. Environ., 28, 1699-1706 (1994). 

The radioactivity ratio of potentially unfractionated fission product radionuclides in precipitation should be independent of the amounts of aerosol and water vapor removed from the air masses. For an air mass containing uniformly mixed radioaerosols from the same nuclear explosion, the ratios should be the same by time and collection-site latitude along the coast. The ratios at storm date may be calculated for depositions following a specifically known atmospheric nuclear explosion with known initial production quantities. The presence of longer lived radio-... 

Global aerosol levels as measured by the Earth Probe, ADEOS, tfra/Nimbus-7 satellites can befound at this web address. Scientists use this data to observe a wide range of phenomena, such as desert dust storms, forest fires, and biomass burning. 

Aerosols, tiny pieces of liquids or solids suspended inside a gas, are both natural and human-made. Natural atmospheric aerosols come from erupting volcanoes, storms that stir up dirt, forest fires, pollinating plants, salt from sea spray, and more. Most of the aerosols in the atmosphere come from natural sources. 

Andreae, M.O., Charlson, R.J., Bruynseels, F., Storms, H., Van Grieken, R. and Maenhaut, W. (1986) Internal mixture of sea salt, silicates and excess sulfate in marine aerosols. Science, 232, 1620-1623. 

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