Shawn Ryan

Near-real-time combustion monitoring for PCDD/PCDF indicators by GC-REMPI-TOFMS.

The boiler exit flue gas of a municipal waste combustor was sampled to evaluate an online monitoring system for chlorobenzene congeners as indicators of polychlorinated dibenzodioxin and dibenzofuran (PCDD/PCDF) concentrations. Continuous measurements of chlorobenzene congeners using gas chromatography coupled to a resonance-enhanced multiphoton ionization - time-of-flight mass spectrometry (GC-REMPI-TOFMS) system were compared over 5-min periods with conventional sampling methods for PCDD/PCDF. Three pairs of values were taken every hour over a period of three days to characterize the combustors response to transient operating conditions (shutdowns and startups). Isolation of specific chlorobenzene congeners from other same-mass compounds was accomplished by using a GC column separator ahead of the REMPI-TOFMS. The 50-fold variation of PCDD/PCDF concentration was paralleled by similar changes in monitored compounds of 1,4-dichlorobenzene, 1,2,4-trichlorobenzene, 1,2,3-trichlorobenzene, and 1,2,4,5-tetrachlorobenzene. A correlation of R = 0.85 and 0.89 was established between 40 pairs of simultaneous 5-min GC-REMPI-TOFMS measurements of 1,2,4-trichlorobenzene and 5 min conventional sampling and analysis for the TEQ and Total measures of PCDD/PCDF, respectively. The GC-REMPI-TOFMS system can be used to provide frequent measures of correlative PCDD/PCDF concentration thereby allowing for an understanding of measures to minimize PCDD/PCDF formation and develop operational feedback to limit emissions.

Development of Size-Selective Sampling of Bacillus anthracis Surrogate Spores from Simulated Building Air Intake Mixtures for Analysis via Laser-Induced Breakdown Spectroscopy

Size-selective sampling of Bacillus anthracis surrogate spores from realistic, common aerosol mixtures was developed for analysis by laser-induced breakdown spectroscopy (LIBS). A two-stage impactor was found to be the preferential sampling technique for LIBS analysis because it was able to concentrate the spores in the mixtures while decreasing the collection of potentially interfering aerosols. Three common spore/aerosol scenarios were evaluated, diesel truck exhaust (to simulate a truck running outside of a building air intake), urban outdoor aerosol (to simulate common building air), and finally a protein aerosol (to simulate either an agent mixture (ricin/anthrax) or a contaminated anthrax sample). Two statistical methods, linear correlation and principal component analysis, were assessed for differentiation of surrogate spore spectra from other common aerosols. Criteria for determining percentages of false positives and false negatives via correlation analysis were evaluated. A single laser shot analysis of approximately 4 percent of the spores in a mixture of 0.75 m3 urban outdoor air doped with approximately 1.1 × 105 spores resulted in a 0.04 proportion of false negatives. For that same sample volume of urban air without spores, the proportion of false positives was 0.08.

The formation of polychlorinated dibenzo-p-dioxins/dibenzofurans from carbon model mixtures containing ferrous chloride.

The potential to form polychlorinated dibenzo-p-dioxins/furans (PCDD/F) was investigated in carbon model systems containing ferrous chloride tetrahydrate and a matrix representative of that found in particle emission from the catalytic extraction process (CEP) for wastes. Various types of carbons were used resulting in different PCDD/F yields but, with one exception, similar homologue distributions. Due to the similarity between the turbostratic structure of the carbon in the representative CEP dusts and the carbon blacks used in the model system, experiments were performed using two carbon blacks (termed CBA and CBB). On a mass basis, CBB was more reactive over the temperature range of 275-325 degrees C and reaction times of 20-60 min in the formation of PCDD/F; as well as more adsorptive in terms of the desorption of PCDD/F. On a volume basis, the reactivities and adsorptivities were similar. A maximum in PCDD/F formation occurred at an oxygen concentration of 2% in nitrogen.

Effect of inoculation method on the determination of decontamination efficacy against Bacillus spores

Decontamination studies investigating the effectiveness of products and processes for the inactivation of Bacillus species spores have traditionally utilized metering viable spores in a liquid suspension onto test materials (coupons). The current study addresses the representativeness of studies using this type of inoculation method compared to when coupons are dosed with a metered amount of aerosolized spores. The understanding of this comparability is important in order to assess the representativeness of such laboratory-based testing when deciding upon decontamination options for use against Bacillus anthracis spores. Temporal inactivation of B. anthracis surrogate (B. subtilis) spores on representative materials using fumigation with chlorine dioxide, spraying of a pH-adjusted bleach solution, or immersion in the solution was investigated as a function of inoculation method (liquid suspension or aerosol dosing). Results indicated that effectiveness, measured as log reduction, was statistically significantly lower when liquid inoculation was used for some material and decontaminant combinations. Differences were mostly noted for the materials observed to be more difficult to decontaminate (i.e., wood and carpet). Significant differences in measured effectiveness were also noted to be a function of the pH-adjusted bleach application method used in the testing (spray or immersion). Based upon this work and the cited literature, it is clear that inoculation method, decontaminant application method, and handling of non-detects (i.e., or detection limits) can have an impact on the sporicidal efficacy measurements.

CHAPTER 7:Bacillus anthracis: An Aerobiological Threat

Anthrax has been a prevalent and fatal disease of grazing herbivorous animals such as cattle, sheep, goats, camels, antelopes, horses and bison and has sporadically claimed the lives of humans. Bacillus anthracis, the etiological agent of anthrax, is a non-motile Gram-positive, spore-forming, rod-shaped bacterium. The spores of B. anthracis, which are infectious for mammals, are highly resistant to a variety of environmental conditions, such as heat, cold, ultraviolet and ionizing radiation, pressure and chemical agents. There are four clinical forms of human anthrax based on the portal of entry of the spores, referred to as inhalational, cutaneous, gastrointestinal and injectional. The high mortality rate of untreated inhalational anthrax together with the ease with which spores can be aerosolized has made B. anthracis an attractive biological weapon and is considered by many to be a serious aerobiological threat for an intentional release. The 21st century has been marked by the 2001 anthrax incident in the United States. This incident led to unprecedented advances in anthrax diagnostics, anthrax vaccine development, detection of B. anthracis spores in environmental matrices, decontamination technology and strategies for B. anthracis contamination and anthrax incident waste management.