Decontamination of Bacillus anthracis Spores at Subzero Temperatures by Complete Submersion.

Introduction: Bacillus anthracis, the etiological agent of anthrax, produces long-lived spores, which are resistant to heat, cold, pH, desiccation, and chemical agents. The spores maintain their ability to produce viable bacteria even after decades, and when inhaled can cause fatal disease in over half of the clinical cases. Owing to these characteristics, anthrax has been repeatedly selected for both bioweapon and bioterrorism use. In the event of a bioterrorism attack, surfaces in the vicinity of the attack will be contaminated, and recovering from such an event requires rapid and effective decontamination. Previous decontamination method development has focused mainly on temperatures >0°C, and have shown poor efficacy at subzero temperatures. Methods: In this study, we demonstrate the use of calcium chloride (CaCl2) as a freezing point depression agent for pH-adjusted sodium hypochlorite (NaOCl) for the effective and rapid decontamination of B. anthracis Sterne strain spores at subzero temperatures. Results: We show the complete decontamination of 106 B. anthracis Sterne strain spores at temperatures as low as -20°C within 2.5 min by submersion in solution containing 25% (w/v) CaCl2, 0.50% NaOCl, and 0.40% (v/v) acetic acid. We also demonstrate significant reduction in number of spores at -28°C. Conclusions: The results show promise for rapidly decontaminating equipment and materials used in the response to bioterrorism events using readily available consumer chemicals. Future study should examine the efficacy of these results on complex surfaces.

Large area decontamination after a radiological incident.

Effective decontamination of large-scale areas such as roads and parking lots after an accidental or intentional radiological incident is important in order to contain the spread of contamination and avoid the need for long-term evacuation of urban areas. As a simulation, large coupons (surface area 3600 cm2) made of concrete patio stone and aged asphalt (from a parking lot) were contaminated with either 60Co or 137Cs solutions and then decontaminated. The decontamination process consisted of a six-component water-based chemical formulation applied using a common house-hold carpet cleaner. Tests were carried out to compare the effectiveness of decontamination using deionized water (simulating rain fall) and chemical formulation. Test results showed that rain fall prior to decontamination lowered the effectiveness of a subsequent decontamination regardless of the surface type or radionuclide. Tests were also carried out to determine if the decontamination effectiveness increased with multiple applications. Using multiple applications of the chemical formulation, the removal of 60Co from concrete patio stone and aged asphalt were 65 ±â€¯2% and 70 ±â€¯3%, respectively, while the removal of 137Cs was 53 ±â€¯3% from asphalt surfaces and 21 ±â€¯8% from concrete patio stone. This paper summarizes the work carried out to prepare for the tests, presents the test results and compares the process to several other processes in terms of effectiveness and suitability for application on a large scale.

Zwitterionic, cationic, and anionic perfluoroalkyl and polyfluoroalkyl substances integrated into total oxidizable precursor assay of contaminated groundwater.

The total oxidizable precursor (TOP) assay can be useful for integrating precursors to perfluoroalkyl acids (pre-PFAAs) into the assessment of sites contaminated by per- and polyfluoroalkyl substances (PFAS). Current research gaps include risks of instrumental matrix effects due to the complexity of post-oxidation extracts, potential reproducibility issues during TOP itself, and limited information for zwitterionic and cationic pre-PFAAs. We first investigated a suitable method for the analysis of groundwater samples, using liquid chromatography high-resolution mass spectrometry (UHPLC-HRMS). Initial sample pre-treatment through filtration could affect the dissolved PFAS concentrations and was therefore avoided. Amending the postoxidation samples with methanol allowed for improved precision and low instrumental matrix effects. We also documented the oxidation yields of 23 anionic, neutral, zwitterionic, and cationic precursor compounds of PFAAs. These precursor compounds were amenable to TOP conversion. The total oxidative yield of 6:2 fluorotelomer sulfonamidoalkyl betaine (6:2 FTAB), for instance, was 80 mol%, with C3-C5 PFCAs as major oxidation products (minor: C6-C7 PFCAs). The method was applied to determine a wide range of PFAS (n = 41) without oxidation as well as ΔPFCA via persulfate oxidation in AFFF-impacted groundwater samples from fire-equipment testing sites in Ontario and Newfoundland, Canada. Summed PFAS concentrations as high as 5 mg L-1 were reported before oxidation, and post-oxidation increases of PFCAs up to + 2300% were observed. A significant contribution of increases in individual PFCAs was attributed to precursors such as 6:2 FTAB, fluorotelomer sulfonates (6:2 FtS, 8:2 FtS), perfluorooctane sulfonamidoalkyl amine (PFOSAm), and perfluorohexane sulfonamide (FHxSA) at the active firefighting training site.

Decontamination of select infrastructure materials after a radiological incident using a water-based formulation.

This paper summarizes the results of the decontamination of the infrastructure materials concrete, limestone, brick and asphalt contaminated with 60Co, 85Sr, 137Cs and 241Am. The paper focuses on the effect of differences in substrate properties and of the pH of the radionuclide solution used for surface contamination on adsorption or ion exchange of the radionuclides and how these factors affect the decontamination effectiveness. A six-component chemical formulation was used and a process effectiveness of up to 76% was obtained depending on the substrate and radionuclide. Asphalt was the easiest material to decontaminate because of its more hydrophobic nature. Concrete and limestone (and to some extent brick) were less effectively decontaminated as their porous surfaces allowed penetration of radionuclides into water-filled pores in the substrate facilitating adsorption or ion exchange and making them difficult to remove. Brick was the most difficult material to decontaminate because the major component of brick is clay which retains most mono- and divalent ions. The removal of 60Co, 85Sr and 137Cs from the surfaces of concrete, limestone and brick increased when the pH of the radionuclide solutions was moderately acidic to neutral compared to when they were highly acidic. The variability in the test results was similar to that observed in other studies using other decontamination methods, attributed to the inhomogeneity of the substrates used and considered representative of real infrastructure materials.

Comparative study on adsorption of perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA) by different adsorbents in water.

Perfluorinated compounds (PFCs) are emerging environmental pollutants. Perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA) are the two primary PFC contaminants that are widely found in water, particularly in groundwater. This study compared the adsorption behaviors of PFOS and PFOA on several commercially available adsorbents in water. The tested adsorbents include granular activated carbon (GAC: Filtrasorb 400), powdered activated carbon, multi-walled carbon nanotube (MCN), double-walled carbon nanotube, anion-exchange resin (AER: IRA67), non-ion-exchange polymer, alumina, and silica. The study demonstrated that adsorption is an effective technique for the removal of PFOS/PFOA from aqueous solutions. The kinetic tests showed that the adsorption onto AER reaches equilibrium rapidly (2 h), while it takes approximately 4 and 24 h to reach equilibrium for MCN and GAC, respectively. In terms of adsorption capacity, AER and GAC were identified as the most effective adsorbents to remove PFOS/PFOA from water. Furthermore, MCN, AER, and GAC proved to have high PFOS/PFOA removal efficiencies (≥98%). AER (IRA67) and GAC (Filtrasorb 400) were thus identified as the most promising adsorbents for treating PFOS/PFOA-contaminated groundwater at mg L(-1) level based on their equilibrium times, adsorption capacities, removal efficiencies, and associated costs.

The release of lindane from contaminated building materials.

The release of the organochlorine pesticide lindane (γ-hexachlorocyclohexane) from several types of contaminated building materials was studied to assess inhalation hazard and decontamination requirements in response to accidental and/or intentional spills. The materials included glass, polypropylene carpet, latex-painted drywall, ceramic tiles, vinyl floor tiles, and gypsum ceiling tiles. For each surface concentration, an equilibrium concentration was determined in the vapour phase of the surrounding air. Vapor concentrations depended upon initial surface concentration, temperature, and type of building material. A time-weighted average (TWA) concentration in the air was used to quantify the health risk associated with the inhalation of lindane vapors. Transformation products of lindane, namely α-hexachlorocyclohexane and pentachlorocyclohexene, were detected in the vapour phase at both temperatures and for all of the test materials. Their formation was greater on glass and ceramic tiles, compared to other building materials. An empiric Sips isotherm model was employed to approximate experimental results and to estimate the release of lindane and its transformation products. This helped determine the extent of decontamination required to reduce the surface concentrations of lindane to the levels corresponding to vapor concentrations below TWA.

Adsorption of cesium on cement mortar from aqueous solutions.

The adsorption of cesium on cement mortar from aqueous solutions was studied in series of bench-scale tests. The effects of cesium concentration, temperature and contact time on process kinetics and equilibrium were evaluated. Experiments were carried out in a range of initial cesium concentrations from 0.0103 to 10.88 mg L(-1) and temperatures from 278 to 313 K using coupons of cement mortar immersed in the solutions. Non-radioactive cesium chloride was used as a surrogate of the radioactive (137)Cs. Solution samples were taken after set periods of time and analyzed by inductively coupled plasma mass spectroscopy. Depending on the initial cesium concentration, its equilibrium concentration in solution ranged from 0.0069 to 8.837 mg L(-1) while the respective surface concentration on coupons varied from 0.0395 to 22.34 µg cm(-2). Equilibrium test results correlated well with the Freundlich isotherm model for the entire test duration. Test results revealed that an increase in temperature resulted in an increase in adsorption rate and a decrease in equilibrium cesium surface concentration. Among several kinetic models considered, the pseudo-second order reaction model was found to be the best to describe the kinetic test results in the studied range of concentrations. The adsorption activation energy determined from Arrhenius equation was found to be approximately 55.9 kJ mol(-1) suggesting that chemisorption was the prevalent mechanism of interaction between cesium ions and cement mortar.

Kinetic and equilibrium studies of cesium adsorption on ceiling tiles from aqueous solutions.

A series of experiments were performed to quantify the adsorption of cesium on ceiling tiles as a representative of urban construction materials. Adsorption was carried out from solutions to mimic wet environmental conditions. Non-radioactive cesium chloride was used as a surrogate of the radioactive (137)Cs. The experiments were performed in the range of initial cesium concentrations of 0.114-23.9 mg L(-1) at room temperature (21°C) around three weeks. Solution samples were taken after set periods of time and analyzed by inductively coupled plasma mass spectrometry (ICP-MS). The quantity of adsorbed Cs was calculated by mass balance as a function of time. Two kinetic and three equilibrium models were employed to interpret the test results. Determination of kinetic parameters for adsorption was carried out using the first-order reaction model and the intra-particle diffusion model. Adsorption equilibrium was studied using Langmuir, Freundlich and three-parameter Langmuir-Freundlich adsorption isotherm models. A satisfactory correlation between the experimental and the predicted values was observed.