SITE CHARACTERISTICS Trinity Site is located at the northern end of the Tularosa Basin in south-central New Mexico. The region is characterized by low annual precipitation (20-25 cm), high summer _temperatures which commonly exceed 37° C. (mean annual temperature of 15° C.), and severe erosion on exposed ground surfaces. Rainfall accounts for about 90% of annual precipitation at the site, which is situated on flat relief at an elevation above mean sea level of 1,500 m. The area supports grass and shrub vegetation with a ground cover between 15-25%. Soils at GZ are characterized as sandy loam with low soil organic carbon (about 0.5%) and a cation exchange capacity (CEC) of about 17 meg/g dry soil. The plutonium concentration ranges from about 1 pCi/g dry soil in the upper 2.5 cm soil to less than 0.01 pCi/g at lower soil depths (Nyhan et al., 1976). Also, about 98% of the plutonium activity and 78% of the soil mass is associated with particles between 100-2,000 um in diameter in the upper 2.5 cm of soil. The range in plutonium concentration for these particles is between 1-5.3 pCi/g with a coefficient of variation exceeding 1.2 (Nyhan et al., 1976). METHODS AND MATERIALS The measurements at the site were partitioned into 30- to 40-day intervals for determination of mean diurnal temperature and windspeed, soil moisture fraction for the upper 2.5 cm of soil, total precipitation accumulation greater than 0.025 cm, and dust mass collections using the Bagnold sampler installed at the site; the latter were submitted for 239724 °py analysis. Windspeed and temperature measurements were made with an MRI continuous recording instrument, and precipitation was measured in 0.025-cm increments with an MRI precipitation collector. The anemometer of the MRI was placed 75 cm above the ground surface corresponding to the maximum height of the fifth collecting compartment of the Bagnold Sampler. The Bagnold sampler was set to orient to windspeeds greater than 313 cm/sec (7 mph). Because most of the MRI data has not been reduced from the charts, a representative subset was taken for preliminary analysis as it was not possible to consider the total data base at this time. Data were selected from charts beginning with the last complete day and every seventh day previous in each measurement interval. Data abstracted from the charts on the selected days were taken at 0200, 0800, 1600, and 2300 hours for windspeed and temperature measurements. 682