Fabrication of liquid and vapor protective cotton fabrics.

Through microwave-assisted techniques, cotton textiles treated with heptadecafluoro-1,1,2,2-tetrahydrodecyltrimethoxysilane in the presence of high surface area silica nanoparticles create a material capable of repelling bulk liquid challenges while simultaneously adsorbing organic vapors from bulk liquid droplets. Characterizing the contradictory behavior of adsorption of vapors and repellency of liquids is the primary focus of this article. These procedures reveal a quick and simple method for a one-step deposition of a vapor-sorptive, liquid-repellent, Cassie-Baxter surface onto textiles. Packed column breakthrough and single swatch permeation experiments showed that treated materials possess a high affinity for 3-hepten-2-one vapor, while goniometry revealed contact angles in excess of 120° for surface-deposited, 5 µL droplets of several test liquids. Scanning electron micrograph images confirm a lotus-like, nanorough surface, while ATR-FTIR spectra confirm surface fluorocarbon moieties. The performance of so-treated materials lends itself to the application of chemical protective apparel, while the simplicity of the treatment bodes well for potential commercialization.

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).

Ozonolysis of mixed oleic acid/n-docosane particles: the roles of phase, morphology, and metastable states.

The reaction kinetics of ozone with oleic acid (OA) in submicron particles containing n-docosane has been studied using aerosol CIMS (chemical ionization mass spectrometry) to monitor changes in particle composition. Internally mixed particles with X(OA) > 0.72 were found to exist as supercooled droplets when cooled to room temperature. Partial reaction of the oleic acid was seen to completely inhibit further reaction and was attributed to the formation of a metastable solid rotator phase of the n-docosane at the surface. This reaction-induced phase change is believed to prevent further reaction by slowing ozone diffusion into the particle. When these particles were cooled to 0 degrees C before reaction, they reacted to a further extent and did not demonstrate such an inhibition. This shift in reactivity upon cooling is attributed to the formation of the thermodynamically stable form of n-docosane, the triclinic solid. This transition was accompanied by an increase in the n-docosane density, which led to the development of "cracks" through which ozone can diffuse into the particle. The aerosol with X(OA) < 0.72 consisted of an external mixture of particles containing n-docosane in either the rotator or the triclinic solid phase because of the stochastic nature of the rotator --> triclinic transition. The reactivity of the oleic acid was seen to increase with increasing n-docosane content as a larger fraction of the particles underwent the rotator --> triclinic transition and therefore contained cracks at the surface. These findings demonstrate the importance of transient, metastable phases in determining particle morphology and how such morphological changes can influence rates of reactions in organic aerosols.

Kinetics and products from reaction of Cl radicals with dioctyl sebacate (DOS) particles in O(2): a model for radical-initiated oxidation of organic aerosols.

The reaction of Cl radicals with bis (2-ethylhexyl) sebacate (also known as dioctyl sebacate, DOS) particles in the presence of O(2) is studied as a model of radical-initiated oxidation of organic aerosols. The uptake coefficient as measured from the rate of loss of DOS is gamma(DOS) = 1.7 (+/-0.3) indicating that a radical chain is operative. It is observed that nearly all of the detected products, accounting for 86% (+/-12%) of the reacted DOS, remain in the particles indicating that they are not efficiently volatilized. Correspondingly, the particles do not decrease in volume even after 60% of the DOS has reacted; upon further reaction the volume does decrease by up to 20%. Additionally, the mass of a DOS film increases with reaction indicating that the density increases. The two primary products identified are the ketone (38 +/- 10% yield) and alcohol (14 +/- 4% yield) resulting from reactions of alkylperoxy radicals originating from DOS oxidation. The fact that the ketone/alcohol ratio is >1 implies that the Russell mechanism, the typical fate of alkylperoxy radicals in liquids whereby both a ketone and an alcohol are generated, is not the only source of ketones. In fact, the ketone yield demonstrates a Langmuir-Hinshelwood type dependence on the O(2) concentration indicating that 44% (+/-8%) of the ketone is created from the reaction of alkoxy radicals with O(2) at the surface of the particles (at 20% O(2)). While this is a common reaction in the gas phase, it is generally not considered to occur in organic solvents. Furthermore, the appearance of gas-phase H(2)O(2) suggests that peroxy radicals react to form two ketones and H(2)O(2)via the Bennett and Summers mechanism. The absence of aldehyde products, both in the gas phase and in the particles, indicates that beta-scission of the alkoxy radicals is not significant. The results of this study suggest that organic aerosols in the troposphere are efficiently oxidized by gas-phase radicals but that their chemical transformation does not lead to their removal through volatilization.

Measuring rates of reaction in supercooled organic particles with implications for atmospheric aerosol.

The kinetics of heterogeneous reactions involving supercooled organic droplets is reported for the first time. Reactions between ozone and internally-mixed sub-micrometre particles containing an unsaturated alkenoic acid, oleic acid, and an n-alkanoic acid, myristic acid, were studied as a simple model for the oxidation of meat-cooking aerosol. The reactions were followed by monitoring the rate of oleic acid loss using an Aerosol CIMS (chemical ionization mass spectrometry) instrument for real-time particle analysis. Evidence of as much as 32 degrees C supercooling at room temperature was observed depending on particle composition. FTIR spectra of the aerosol also demonstrate features indicative of supercooling. Particles in which crystallization was induced by cooling below room temperature demonstrated decreased reactivity by a factor of 12 compared to supercooled particles of the same composition. This drastic difference in reactivity could have significant implications for the lifetimes of reactive species in ambient aerosol as well as for the accurate source apportionment of particulate matter.

Ozonolysis of oleic acid particles: evidence for a surface reaction and secondary reactions involving Criegee intermediates.

The heterogeneous reactions of ozone with monodisperse oleic acid and methyl oleate particles were studied by monitoring the loss of the condensed-phase species using an aerosol chemical ionization mass spectrometer (Aerosol CIMS). The reaction of ozone with oleic acid was determined to occur at the surface of the particles despite previous assumptions that it reacts in the bulk. The ozonolysis of methyl oleate particles, on the other hand, was found to be limited by the diffusion of ozone and does react in the bulk. The difference in reaction mechanisms is attributed to the larger degree of order in oleic acid known to result from the formation of hydrogen-bonded dimers. The reactive uptake coefficients, gamma, calculated from the rate of loss of the particle species are gamma = (1.38 +/- 0.06) x 10(-3) for oleic acid and gamma = (1.23 +/- 0.10) x 10(-3) for methyl oleate. However, it is found that secondary reactions between Criegee intermediates and the carboxylic acid moiety in oleic acid are responsible for 36% (+/-4%) of its observed loss. Hence, the rate of loss of ozone cannot be equated to the rate of loss of oleic acid. Accounting for this additional reaction the uptake coefficient for ozone on oleic acid particles is calculated to be gamma = (8.8 +/- 0.5) x 10(-4). The magnitude of these secondary reactions quantitatively reconciles discrepancies between previous coated flow tube and particle-based studies, and it illustrates the need to include additional loss mechanisms when calculating uptake coefficients from the rates of loss of particle species. Implications of reactions with Criegee intermediates in atmospheric particles are discussed.

A chemical ionization mass spectrometry method for the online analysis of organic aerosols.

A new technique employing chemical ionization mass spectrometry (CIMS) is described that allows the composition of organic particles to be determined on the time scale of seconds. With this Aerosol CIMS technique, particles are vaporized thermally at temperatures up to 480 degrees C, and the resulting vapor is chemically ionized and detected with a quadrupole mass spectrometer. The separation of the vaporization and ionization steps allows greater control and more flexibility for the detection of condensed phases than with other chemical ionization methods. Consequently, composition can be correlated to volatility, providing an additional dimension of information. The use of a variety of positive and negative reagent ions, such as H(+)(H(2)O)(2), H(+)(CH(3)OH)(2), NO(+), O(2)(+), O(2)(-), F(-), and SF(6)(-), offers flexibility in the detection sensitivity and specificity. Furthermore, the degree of fragmentation of the resulting ion can be controlled, providing more straightforward identification and quantification than with other commonly used methods, such as electron impact ionization. Examples are given of the detection of aerosols consisting of organics with various functionalities, including alkanes, alkenes, alcohols, aldehydes, ketones, and carboxylic acids. Applications of this technique to laboratory studies of atmospherically relevant aerosol reactions are discussed.

The uracil transporter Fur4p associates with lipid rafts.

Sphingolipids are abundant components of eucaryotic membranes, where they perform essential functions. To uncover new roles for sphingolipids, we studied Saccharomyces cerevisiae lcb1-100 cells, which have a temperature-sensitive block in the first step in sphingolipid synthesis. We find that the level of all five species of the sphingoid long chain base intermediates is reduced 2-7-fold in cells grown at a permissive temperature, and the level of complex sphingolipids is reduced 50%. In addition, lcb1-100 cells make no detectable phosphorylated sphingoid bases. After transfer to a restrictive temperature (a heat shock), the level of the major sphingoid bases drops rather than transiently rising, as in wild type cells. These changes affect lcb1-100 cells in multiple ways. Basal uracil transport by Fur4p is reduced 25%, and when cells are heat-shocked, uracil transport activity falls rapidly and is not restored as it is in wild type cells. Restoration requires a functional secretory pathway and synthesis of complex sphingolipids, leading us to hypothesize that Fur4p associates with lipid rafts. The finding that Fur4p is insoluble in TritonX-100 at 4 degrees C and behaves like a raft-associated protein on a density gradient supports this hypothesis. Raft association may be essential for regulating breakdown of Fur4p in response to stresses and other factors that govern uracil transport activity. Our results show that long chain bases do not contribute to the inactivation of Fur4p transport activity after heat stress, but they are essential for some later, but unknown, process that leads to degradation of the protein. Further studies using lcb1-100 cells should reveal new roles of sphingolipids in nutrient uptake and other membrane-dependent processes.