Polyester-rayon blend wipes were evaluated for efficiency of extraction and recovery of powdered Bacillus atrophaeus spores from stainless steel and painted wallboard surfaces. Method limits of detection were also estimated for both surfaces. The observed mean efficiency of polyester-rayon blend wipe recovery from stainless steel was 0.35 with a standard deviation of ؎0.12, and for painted wallboard it was 0.29 with a standard deviation of ؎0. It is critical from a public health perspective that the information obtained is accurate and reproducible. The consequences of an inappropriate public health response founded on information garnered by an ineffective sample collection method or procedure has the potential for undesired social and economic impact. Well-developed and validated procedures for the collection and analysis of biological environmental samples are required to provide the necessary level of confidence in agent characterization information provided.Researchers and investigators are aware that the Centers for Disease Control and Prevention (CDC)-recommended procedures for the collection of B. anthracis spores by swab, wipe, and vacuum filtration collection methods (6) underestimate the number of spores on surfaces, and attempts are being made to address the knowledge gap (4,5,18,19). Additionally, a number of studies have been conducted to determine the efficiency of the swab sample collection method (1,2,3,7,8,10,17,18), but limited studies have been conducted to examine the efficiency of the wipe spore collection method (10, 13). A recent study conducted by Sanderson et al. (19) that compared B. anthracis surface sampling results obtained by swab, wipe, and vacuum filtration methods suggests that the wipe collection method outperforms the swab method, but no independent recovery efficiency was established for the wipe method.The objective of this study was to empirically evaluate the wipe surface sample collection method for recovery efficiency with a polyester-rayon blend wipe material and estimate limits of detection for selected nonporous surfaces seeded with dry deposited Bacillus atrophaeus spores. Additionally, a sonication extraction method was evaluated for effectiveness in removing viable spores from the selected wipe collection material. MATERIALS AND METHODSSpore matrix. The material used as the test agent for this study was a powdered matrix containing B. atrophaeus spores (ATCC 9372; formerly Bacillus subtilis var. niger and subsequently "Bacillus globigii") (12) and silicon dioxide particles obtained from the U.S. Army Dugway Proving Ground Life Science Division. The spore material was prepared by cultivating B. atrophaeus in tryptic soy broth (Difco, Detroit, MI) containing 3 mg/liter MnSO 4 (Fisher Scientific, Pittsburgh, PA). After 80 to 90% sporulation, the spore suspension was centrifuged to obtain a spore suspension containing approximately 20% solids. Dry spore material was then prepared from the unwashed spore suspension with a laboratory spray dryer. The spore material was...

Vacuum filter socks were evaluated for recovery efficiency of powdered Bacillus atrophaeus spores from two non-porous surfaces, stainless steel and painted wallboard and two porous surfaces, carpet and bare concrete. Two surface coupons were positioned side-by-side and seeded with aerosolized Bacillus atrophaeus spores. One of the surfaces, a stainless steel reference coupon, was sized to fit into a sample vial for direct spore removal, while the other surface, a sample surface coupon, was sized for a vacuum collection application. Deposited spore material was directly removed from the reference coupon surface and cultured for enumeration of colony forming units (CFU), while deposited spore material was collected from the sample coupon using the vacuum filter sock method, extracted by sonication and cultured for enumeration. Recovery efficiency, which is a measure of overall transfer effectiveness from the surface to culture, was calculated as the number of CFU enumerated from the filter sock sample per unit area relative to the number of CFU enumerated from the co-located reference coupon per unit area. The observed mean filter sock recovery efficiency from stainless steel was 0.29 (SD = 0.14, n = 36), from painted wallboard was 0.25 (SD = 0.15, n = 36), from carpet was 0.28 (SD = 0.13, n = 40) and from bare concrete was 0.19 (SD = 0.14, n = 44). Vacuum filter sock recovery quantitative limits of detection were estimated at 105 CFU m(-2) from stainless steel and carpet, 120 CFU m(-2) from painted wallboard and 160 CFU m(-2) from bare concrete. The method recovery efficiency and limits of detection established in this work provide useful guidance for the planning of incident response environmental sampling for biological agents such as Bacillus anthracis.

Aim:  To evaluate US Centers for Disease Control and Prevention recommended swab surface sample collection method for recovery efficiency and limit of detection for powdered Bacillus spores from nonporous surfaces. Methods and Results:  Stainless steel and painted wallboard surface coupons were seeded with dry aerosolized Bacillus atrophaeus spores and surface concentrations determined. The observed mean rayon swab recovery efficiency from stainless steel was 0·41 with a standard deviation (SD) of ±0·17 and for painted wallboard was 0·41 with an SD of ±0·23. Evaluation of a sonication extraction method for the rayon swabs produced a mean extraction efficiency of 0·76 with an SD of ±0·12. Swab recovery quantitative limits of detection were estimated at 25 colony forming units (CFU) per sample area for both stainless steel and painted wallboard. Conclusions:  The swab sample collection method may be appropriate for small area sampling (10 –25 cm2) with a high agent concentration, but has limited value for large surface areas with a low agent concentration. The results of this study provide information necessary for the interpretation of swab environmental sample collection data, that is, positive swab samples are indicative of high surface concentrations and may imply a potential for exposure, whereas negative swab samples do not assure that organisms are absent from the surfaces sampled and may not assure the absence of the potential for exposure. Significance and Impact of the Study:  It is critical from a public health perspective that the information obtained is accurate and reproducible. The consequence of an inappropriate public health response founded on information gathered using an ineffective or unreliable sample collection method has the potential for undesired social and economic impact.

Radionuclide transport experiments were carried out using intact cores obtained from the Culebra member of the Rustler Formation inside the Waste Isolation Pilot Plant, Air Intake Shaft. Twenty-seven separate tests are reported here and include experiments with 3H, Am, 239Np, 228Th, 232U and 24iPu, and two brine types, AIS and ERDA 6. The 3H was bound as water and provides a measure of advection, dispersion, and water self-diffusion. The other tracers were injected as dissolved ions at concentrations below solubility limits, except for americium. 22 241 Na, 22Na was transported similarly to 3H, which shows it is a conservative tracer in the Culebra samples and can be used as a replacement for 3H to eliminate interference with 24'Pu analysis. 1Two tracers eluted but were moderately retarded, 239Np and 232U. Three tracers, and 241Pu, were not detected in column effluent.Am, "' Th Breakthrough curves for eluting species were fitted to single and dual porosity models. The single porosity model assumed a homogeneous porous medium and advection-dispersion transport. The dual porosity model is similar to the Performance Assessment transport model, SECO-TP. A macro or advective pore space transports solute by advection and dispersion, while a micro or matrix pore space is only accessible by diffusion. Diffusion geomtry is onedimensional. Fitting 3H and 22Na data provided core porosity and solute dispersion coefficients. Fitted parameters for conservative solute showed little difference between single and dual porosity models indicating limited effective distinction between the two. In three cores, single porosity fits provided porosity only 112 to 116 of an independent estimate of the total porosity. In all cores the hydrodynamic dispersion coefficient was an order of magnitude greater than packed columns. This indicates significant preferential flow occurred in the columns and is consistent with dispersion in heterogeneous media.No clear trend is apparent with regard to flow rate dependencies. Likewise, the Salado brine, ERDA 6 did not produced a significant change in retardation relative to AIS.Fitted retardation factors, R for 239Np ranged from to 30 to 78 and from 2 to 18 for 232U, with the single porosity model. In general, good fits could be obtained with the dual porosity model only if the advective porosity was allowed to retard the solute. The dual porosity fit for 232U and 239Np yielded matrix retardation's one to two orders of magnitude greater than the single porosity model. Those higher values may be the best estimates of the dolomite retardation potential. However, since the overall fitting to the elution curve is not clearly better than the single porosity model, the higher retardation is considered unproven by these experiments.Theoretical analysis using the minimum detection limits for 24'Am, 228Th and 24'Pu and the single porosity model provided minimum retardation estimates for the non-eluting species.Minimum R values were 520 to 18,000 for 241Am, 9.1 to 47 for 228Th, and 800 to 38,000 for 2...

The dimensionless aerodynamic particle sizer (APS) response function (normalized particle velocity against particle Stokes number) first reported by Chen et al. (1985) is explored for much larger solid particles (diameters to 35 pm) over a similar range of instrument pressures (624-740 mm Hg) and flow rates (4.2-6.0 L/min). An essentially unique response function is found for low and intermediate Stokes numbers under a variety of operating conditions, including the use of argon as the carrier gas. For large particles, however, non-Stokesian drag effects introduce systematic differences among calibration sets so that a unique response function no longer applies. The largest differences are observed between calibrations performed in air and argon, although even in this case the sizing error amounts to < 12% for a 20-pm polystyrene latex sphere. For intermediate Stokes numbers, a direct consequence of this work is that a reference calibration (channel number against Stokes number) can be used under different ambient conditions by setting the APS to operate at the same nozzle velocity as used in the reference calibration. With the single-velocity method, the factory-supplied calibration relating channel number to aerodynamic diameter can be used for air over a reasonable range of ambient temperatures and pressures. The same calibration can be used with an argon carrier gas provided that the aerodynamic diameters reported by the APS software are adjusted by the square root of the gas viscosity ratio. For the singlevelocity mode of operation, a generalization of a correction proposed by John (1987, 1989) can be made and is shown to reduce by one half the sizing error introduced by non-Stokesian drag.