Michael V. Henley

Formation of Active Chlorine Oxidants in Saline-Oxone Aerosol

The application of oxidative reactions of Oxone® [2KHSO5 KHSO4 K2SO4] as an active decontaminant has been mainly utilized through the aqueous solution. However, little is known about reactivity of aerosolized Oxone particles although the use of appropriate aerosolized oxidants would have significant value in remediating contaminated surfaces. In this study, the feasibility of producing active chlorine species from saline-Oxone aerosols was studied using a 2-m3 Teflon film chamber. To evaluate the oxidative capability of a saline-Oxone aerosol, the aerosol was collected onto filters impregnated with a dye (e.g., metanil yellow) that reacts with active chlorine in the aerosol, and monitored by UV-Visible spectroscopy. Spectral data showed that the dye compound was 86% oxidized by active chlorine within 4 min. There was no significant difference in oxidation capability between with buffer and without buffer system, although the presence of phosphate buffer somewhat retarded the formation rate of active chlorine in saline-Oxone aerosol particles. Saline-Oxone aerosols were found to be highly acidic as determined by UV-Vis spectroscopy, indicating that the aerosol produced mostly an undissociated form of active chlorine species (e.g., HOCl and Cl2) that was susceptible to partitioning into the gas phase. Our study concludes that the aerosolized saline-Oxone is a feasible chlorine oxidant, but the efficiency of such an approach still needs investigation.

Cl2 deposition on soil matrices

Deposition of chlorine gas, Cl(2), on synthetic soil sample matrices was examined in a small chamber to ascertain its potential significance as a chemical sink during large-scale releases. The effects of organic matter, clay and sand mass fractions of the soil matrix, soil packing, and exposure to ultraviolet (UV) light on the observed Cl(2) deposition were examined. Organic matter content was found to be the dominant soil variable investigated that affected Cl(2) deposition; all other variables exhibited no measurable effect. Analytical results from the top 8.5mm of soil columns exposed to Cl(2) were fit to a simple kinetic model with six adjustable parameters. The kinetic model included two reactive bins to account for fast- and slow-reacting material in the soil matrices. The resulting empirical equation agreed with the data to within a factor of two and accurately predicted results from soil mixes not used to optimize the adjustable parameters. Total Cl(2) deposition, assuming a penetration depth of 8.5mm, was calculated to be as high as 160 metric tons per square kilometer for soil with an organic content of 10%, and inferred deposition velocities were as high as 0.5 cm/s for organically rich soil.

Deposition of Cl2 on soils during outdoor releases

Synthetic soil blends were exposed to dense chlorine (Cl2) plumes released at Dugway Proving Ground, UT, during Spring 2010 with the purpose of determining the magnitude of Cl2 deposition onto soil and assessing its potential for attenuating a high-concentration plume. Samples were exposed at varying distances from the release point to include exposure to the pooling liquid (2-3m) and dense vapor (10-17 m). Following exposure, soil samples were cored, fractionated vertically and analyzed for chloride (Cl(-)) to quantify the integrated amount of Cl2 deposited. Cl(-) was detected as deep as 4 cm in samples exposed to dense Cl2 vapor and in the deepest fractions (13 cm) of samples exposed to liquid Cl2. Chloride concentration, [Cl(-)], in the soil samples positively correlated with soil mass fractions of organic matter and water, and while their individual contributions to Cl2 deposition could not be quantitatively determined, the data suggest that organic matter was the primary contributor. [Cl(-)] results from the top vertical fractions (1.3 cm nearest the surface) were used in an analysis to determine the magnitude of deposition as a loss term under low-wind (≤ 1.6m/s) conditions. The analysis revealed up to 50% of a 1814-kg release could be deposited within 20 m from the release point for soil with high organic matter (43%) and/or water content (29%).

The effects of active chlorine on photooxidation of 2-methyl-2-butene.

Active chlorine comprising hypochlorite (OCl⁻), hypochlorous acid (HOCl) and chlorine (Cl₂) is the active constituent in bleach formulations for a variety of industrial and consumer applications. However, the strong oxidative reactivity of active chlorine can cause adverse effects on both human health and the environment. In this study, aerosolized Oxone® [2KHSO₅, KHSO₄, K₂SO₄] with saline solution has been utilized to produce active chlorine (HOCl and Cl₂). To investigate the impact of active chlorine on volatile organic compound (VOC) oxidation, 2-methyl-2-butene (MB) was photoirradiated in the presence of active chlorine using a 2-m³ Teflon film indoor chamber. The resulting carbonyl products produced from photooxidation of MB were derivatized with O-(2,3,4,5,6-pentafluorobenzyl) hydroxyamine hydrochloride (PFBHA) and analyzed using gas chromatograph-ion trap mass spectrometer (GC/ITMS). The photooxidation of MB in the presence of active chlorine was simulated with an explicit kinetic model using a chemical solver (Morpho) which included both Master Chemical Mechanism (MCM) and Cl radical reactions. The reaction rate constants of a Cl radical with MB and its oxidized products were estimated using a Structure-Reactivity Relationship method. Under dark conditions no effect of active chlorine on MB oxidation was apparent, whereas under simulated daylight conditions (UV irradiation) rapid MB oxidation was observed due to photo-dissociation of active chlorine. The model simulation agrees with chamber data showing rapid production of oxygenated products that are characterized using GC/ITMS. Ozone formation was enhanced when MB was oxidized in the presence of irradiated active chlorine and NO(x).

Effect of soil moisture on chlorine deposition.

The effect of soil moisture on chlorine (Cl(2)) deposition was examined in laboratory chamber experiments at high Cl(2) exposures by measuring the concentration of chloride (Cl(-)) in soil columns. Soil mixtures with varying amounts of clay, sand, and organic matter and with moisture contents up to 20% (w/w) were exposed to ≈3×10(4)ppm Cl(2) vapor. For low water content soils, additional water increased the reaction rate as evidenced by higher Cl(-) concentration at higher soil moisture content. Results also showed that the presence of water restricted transport of Cl(2) into the soil columns and caused lower overall deposition of Cl(2) in the top 0.48-cm layer of soil when water filled ≈60% or more of the void space in the column. Numerical solutions to partial differential equations of Ficks law of diffusion and a simple rate law for Cl(2) reaction corroborated conclusions derived from the data. For the soil mixtures and conditions of these experiments, moisture content that filled 30-50% of the available void space yielded the maximum amount of Cl(2) deposition in the top 0.48cm of soil.

Modeling the atmospheric chemistry of TICs

An atmospheric chemistry model that describes the behavior and disposition of environmentally hazardous compounds discharged into the atmosphere was coupled with the transport and diffusion model, SCIPUFF. The atmospheric chemistry model was developed by reducing a detailed atmospheric chemistry mechanism to a simple empirical effective degradation rate term (keff) that is a function of important meteorological parameters such as solar flux, temperature, and cloud cover. Empirically derived keff functions that describe the degradation of target toxic industrial chemicals (TICs) were derived by statistically analyzing data generated from the detailed chemistry mechanism run over a wide range of (typical) atmospheric conditions. To assess and identify areas to improve the developed atmospheric chemistry model, sensitivity and uncertainty analyses were performed to (1) quantify the sensitivity of the model output (TIC concentrations) with respect to changes in the input parameters and (2) improve, where necessary, the quality of the input data based on sensitivity results. The model predictions were evaluated against experimental data. Chamber data were used to remove the complexities of dispersion in the atmosphere.

Detection of pathogenic organisms in food, water, and body fluids

The construction of specific bioluminescent bacteriophage for detection of pathogenic organism can be developed to overcome interferences in complex matrices such as food, water and body fluids. Detection and identification of bacteria often require several days and frequently weeks by standard methods of isolation, growth and biochemical test. Immunoassay detection often requires the expression of the bacterial toxin, which can lead to non-detection of cells that may express the toxin under conditions different from testing protocols. Immunoassays require production of a specific antibody to the agent for detection and interference by contaminants frequently affects results. PCR based detection may be inhibited by substances in complex matrices. Modified methods of the PCR technique, such as magnetic capture-hybridization PCR (MCH-PCR), appear to improve the technique by removing the DNA products away from the inhibitors. However, the techniques required for PCR-based detection are slow and the procedures require skilled personnel working with labile reagents. Our approach is based on transferring bioluminescence (lux) genes into a selected bacteriophage. Bacteriophages are bacterial viruses that are widespread in nature and often are genus and species specific. This specificity eliminates or reduces false positives in a bacteriophage assay. The phage recognizes a specific receptor molecule on the surface of a susceptible bacterium, attaches and then injects the viral nucleic acid into the cell. The injected viral genome is expressed and then replicated, generating numerous exact copies of the viral genetic material including the lux genes, often resulting in an increase in bioluminescence by several hundred fold.

Atmospheric transformation of volatile organic compounds

To be able to understand and predict the concentration of a target compound in the atmosphere one must understand the atmospheric chemistry involved. The transformation of volatile organic compounds in the troposphere is predominantly driven by the interaction with the hydroxyl and nitrate radicals. The hydroxyl radical exists in daylight conditions and its reaction rate constant with an organic compound is typically very fast. The nitrate radical drives the nighttime chemistry. These radicals can scavenge hydrogen from an organic molecule generating secondary products that are often overlooked in detection schemes. Secondary products can be more stable and serve as a better target compound in detection schemes. The gas phase reaction of the hydroxyl radical (OH) with cyclohexanol (COL) has been studied. The rate coefficient was determined to be (19.0 +/- 4.8) X 10-12 cm3 molecule-1 s-1 (at 297 +/- 3 K and 1 atmosphere total pressure) using the relative rate technique with pentanal, decane, and tridecane as the reference compounds. Assuming an average OH concentration of 1 X 106 molecules cm-3, an atmospheric lifetime of 15 h is calculated for cyclohexanol. Products of the OH + COL reaction were determined to more clearly define cyclohexanols atmospheric degradation mechanism. The observed products were: cyclohexanone, hexanedial, 3- hydroxycyclohexanone, and 4-hydroxycyclohexanone. Consideration of the potential reaction pathways suggest that each of these products is formed via hydrogen abstraction at a different site on the cyclohexanol ring.