Measurement of ²²²Rn diffusion through sandy soil with solar cells photodiodes as the detector.

An experimental system was developed to study the diffusion rate of radon (²²²Rn) gas through porous media as a function of soil porosity/grain size and soil water content. Columns with different grain sizes, soil water content and soil depths were used. The system used solar cells photodiodes as alpha (α) detectors. This new detector is highly efficient and low cost compared to other known detectors. Soil water content was found to be the most dominant factor affecting the ²²²Rn diffusion rate. A maximum diffusion rate value of (6.5 ± 0.07) × 10⁻6 m²/s was found in dry conditions. The minimum diffusion value of less than (3.9 ± 0.14) × 10⁻7 m²/s was found in 2% soil water content. The experimental results were compared with theoretical calculations done with the "GREEN equation". Two discrepancies were observed: the time to equilibrium state in the measurements was longer compare to the calculated values and the α count rates were lower in the experiment compared with the theoretical calculations. These results can be explained by the differences in the system geometry.

A comprehensive method for aeolian particle granulometry and micromorphology analyses.

The aim of this study was to use a new approach to investigate aeolian particle granulometry and micromorphology. Taking total aeolian deposition into account, we used parameters such as, particle area, perimeter, shape analysis for particle roughness (area/perimeter) and elongation (long/short axis). These parameters were analyzed on temporal and spatial scales at four study sites in the eastern Negev Desert, Israel. The total collection of particles was sorted into three size groups based on particle area to facilitate comparison. The classic definition of particle size (equating particle length with particle diameter) produced relatively small variations among the three size classes (25-38.6%). Our proposed comprehensive method demonstrated significant variation among the three size classes (13.9-60.8%), e.g. the classic method placed 36.4% of the particles in size class two while the new method placed 60.8% of the particles in this size class; the differences were even more significant regarding size class 3 (38.6% vs. 13.9%, respectively). The classic method did not facilitate investigation of particle roughness and elongation. With this new approach, it was possible to clearly define the particles by size class, based on these characteristics. With roughness, the variation among size classes 2 and 3 was about 27%. With elongation, the variation among size classes two and three was about 21%. Applying similar investigation method to study the aeolian particle granulometry and micromorphology can better facilitate more detailed calculation of particle size distribution, roughness and elongation.

Recovery efficiencies of anthrax spores and ricin from nonporous or nonabsorbent and porous or absorbent surfaces by a variety of sampling methods*.

The 2001 anthrax letter cases brought into focus the need to establish the most effective environmental sampling procedures. Results are presented from two studies aimed at establishing the best procedures for everyday surfaces likely to be contaminated after the release of environmentally stable bioaggressive agents, as exemplified by anthrax spores and ricin. With anthrax spores, contact plates, with mean retrieval rates of 28-54%, performed better than other methods by a wide margin for flat nonporous, nonabsorbent surfaces. They also proved best on flat porous, absorbent materials, although recoveries were low (<7%). For both agents, dry devices (swabs, wipes, Trace Evidence Collection Filters) had universally poor retrieval efficiencies with no significant differences between them. Among moistened devices (wipes, swabs, and Sample Collection and Recovery Devices), wipes were generally best, albeit with considerable cross-over among individual readings (highest mean recoveries for anthrax spores and ricin 5.5% and 2.5%, respectively, off plastic).

Heat activation/shock temperatures for Bacillus anthracis spores and the issue of spore plate counts versus true numbers of spores.

Assessing true numbers of viable anthrax spores is complex. Optimal heat activation conditions vary with species, media and germinants. Published time/temperature combinations for Bacillus anthracis spores range from 60 degrees C for 1, post-heating counts were less than their pre-heating counterparts on between 71% and 88% of occasions. A high probability was found of viable spore counts differing significantly from counts determined microscopically, with differences of almost 1 log possible. Viable counts were lower than microscopic counts in 15 of 18 tests.