over a minimum of 1 hr, which corresponds to the least time possible with the ultrahigh-volume air sampler previously mentioned, mechanisms related to pickup of particles from the soil surface cannot be studied in real time and with high resolution. To overcome these limitations, two light-scattering instruments were adapted to measure the mass loading of particles in air and the number distribution as a function of particle size over very short periods of time. Both instruments give data in real time, such that it is possible to correlate micrometeorological events of short duration with the concentration of airborne particles. These instruments examine the particle spectrum in the region of 0,1 to 10 um, and do not differentiate between radioactive and nonradioactive particles. Nevertheless, valuable data have been obtained on the mass loading of particles in air as a function of the forces causing pickup from the soil surface, The first instrument employed was a light-scattering-type particle analyzer, This instrument, when used with a pulse-height analyzer, will give particle size histograms over a range of 0.5 to 10.5 ym. Sufficient data can be collected in periods of 2 min or lese. Particle sizes as measured by this technique are related to their physical diameters. If the physical properties of the particles are known, aerodynamic or "effective" particle sizes can be determined. This is necessary for modeling of particle deposition in the human respiratory tract. Details of the instrument and ites application to the GMX experiment are covered by Koval (this report). Another lightscattering device currently employed is the nephelometer. It has extremely fast response (< 1 sec}; however, it does not give particle size distribution data, only relative particle concentration. It ia an exceptional instrument for correlating very short-time duration meteorological events with masse loading of particles in the air. A recently introduced high-volume (20 cfm) cascade impactor was adapted for use in the GMX experiment. This instrument haa five stages which correspond to 1,1, 1.1-2.0, 2.0-3.3, 3.3-7.0, and greater than 7.0 um. The filter papers may be analyzed for total plutonium per stage and total mass for all particles on each stage, Thus, the particles picked up from the soil surface may be characterized according to their serodynamic sizes, and the relationship between plutonium and total mass may be established. Further refinements are being made on this instrument which will reduce reentertainment of particles and improve its particle intake characteristics. Particles that roll or bounce along the soil surface (creep/saltation) may be responsible for the most significant net movement of surface mass compared with other processes. Existing instruments that had been used in agricultural erosion studies and for measuring the movement of sand in windstorms were evaluated. A series of laboratory studies were conducted at LLL on borrowed or copied instruments. Out of thie work, & multistage sampler was developed, capable of collecting the particle fraction moving by creep and particles moving in saltation at varicus levels above the surface. Details on the design and preliminary results are covered by Reichman (this report). i. ube 280 Initial dust devil observations were made with a time-lapse camera adapted for use on an 80-ft tower. The camera was programmed to expose one frame every five sec, Experimentation with optimum camera location and lens selection resulted in ability to view the entire GMX experimental site. This system was developed as a survey tool in order to get an approximate idea of the dust devil population. A visual count fa the GMX and surrounding area during a l-hr period in July, 1973, showed a dust devil population of approximately one dust devil formation per minute, with an average lifetime of about 2 min. An elsborate meteorological data-gathering system, capable of measuring and vertiwind and temperature profiles, fluctuations of the horizontal cal wind structure, soil moisture, soil temperature, humidity, rainfall, up. This and other macellaneous meterological measurements, was set was under the direction of the Air Resources Laboratory-Las Vegas, and is covered in detail by Kennedy and Booth (this report). FUTURE STUDIES of radioA number of problems dealing with understanding redistribution to possible activity at NTS still remain. These problems are related of NTS, and other long-term health and safety issues, future land uses the movement AEC nuclear programs. So far, LLL studies have involved emitters of plutonium at the GMX site, and redistribution of gamma device released from the Schooner cratering event and the Baneberry particles test. To date, the GMX studies have focused on plutonium been has Emphasis carried into suspension by the force of the wind. and measuring on collecting samples of airborme plutonium particles the relationship a number of micrometéorological parameters, such that important driving between air concentrations of plutonium and the constructed. The forces may be understood, and a mathematical model and occasionwind forces studied so far have been diurnal in nature, ally thoge associated with dust storms. Dust Devils devils, which might be There i9, however, another driving force: dust ances for transporting a significant mechanism under certain circumst re. surface radioactive material into the atmosphe to the ground and the Because of the high wind speeds generated close capable of removing and large vertical structure, dust devils are of loose surface material. transporting vertically a significant portion indicate that on the 1973) (1966, Sinclair by ents measurem il Dust-dev of 285 km provides a total average, a typical dust-devil source region 7 x 10° tons of desert mean seasonal vertical dust transport of over larger, for the same gand. This is one to two orders of magnitude e et al., 1972) surface area, than pre-dust storm conditions (Gillett