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).

Reverse osmosis processing of organic model compounds and fermentation broths.

Post-treatment of an anaerobic fermentation broth was evaluated using a 150 gal/day, single cartridge prototype reverse osmosis (RO) system. Baseline tests were conducted at 25 degrees C using six organic model compounds representing key species found in the fermentation broth: ethanol, butanol, acetic acid, oxalic acid, lactic acid, and butyric acid. Correlations of the rejection and recovery efficiencies for these organic species, individually and in simulated mixtures, were obtained as a function of feed pressure with and without recirculation of the retentate. The actual fermentation broth obtained from a continuous-flow biohydrogen process was treated by the RO system under the operating conditions similar to those used in the baseline tests, resulting in greater than 95% removal of total organic carbon. These results are encouraging and useful for further studies on the feasibility of incorporating the RO technology into an integrated and field deployable wastewater management and water recovery system.

Inactivation of biological agents using neutral oxone-chloride solutions.

Bleach solutions containing the active ingredient hypochlorite (OCl-) serve as powerful biological disinfectants but are highly caustic and present a significant compatibility issue when applied to contaminated equipment or terrain. A neutral, bicarbonate-buffered aqueous solution of Oxone (2K2HSO5.KHSO4.K2SO4) and sodium chloride that rapidly generates hypochlorite and hypochlorous acid (HOCl) in situ was evaluated as a new alternative to bleach for the inactivation of biological agents. The solution produced a free chlorine (HOCl + OCl-) concentration of 3.3 g/L and achieved > or =5.8-log inactivation of spores of Bacillus atrophaeus, Bacillus thuringiensis, Aspergillus niger, and Escherichia coli vegetative cells in 1 min at 22 degrees C. Seawaterwas an effective substitute for solid sodium chloride and inactivated 5 to 8 logs of each organism in 10 min over temperatures ranging from -5 degrees C to 55 degrees C. Sporicidal effectiveness increased as free chlorine concentrations shifted from OCl- to HOCl. Neutrally buffered Oxone-chloride and Oxone-seawater solutions are mitigation alternatives for biologically contaminated equipment and environments that would otherwise be decontaminated using caustic bleach solutions.

Use of in situ-generated dimethyldioxirane for inactivation of biological agents.

Dimethyldioxirane (DMDO), generated in situ by adding acetone to an aqueous solution containing potassium peroxymonosulfate (Oxone) at neutral pH, was investigated for inactivation of biological warfare agent simulants. The DMDO solution inactivated bacterial spores, fungal spores, vegetative bacterial cells, viruses, and protein by 7 orders of magnitude in less than 10 min. The kill rates of DMDO were more pronounced when compared to kill rates of buffered Oxone alone. Conditions for the use of DMDO as a biological decontaminant were optimized by evaluating the effects of age and temperature on open systems. DMDO effectiveness was compared to that of current decontaminant solutions such as DS2 (used by the U.S. military), bleach, and hydrogen peroxide and was shown to be superior in achieving a 7-log kill of Bacillus atrophaeus, a Bacillus anthracis spore simulant. The results demonstrate the potential for DMDO to fill the need for a noncorrosive, nontoxic, and environmentally safe decontaminant.

Determination of in situ-generated dimethyldioxirane from an aqueous matrix using selected ion monitoring.

There is a growing interest in utilizing in situ-generated dimethyldioxirane (DMDO) as an oxidant for synthetic purposes and bleaching and decontamination applications, but the ability to quantify the organic cyclic peroxide species is often complicated by the presence of other reactive components, peroxymonosulfate and acetone, within the solution matrix. This paper is the first to report the use of a MS method for the quantitation of DMDO from these complex matrices by utilizing an isothermal 30 degrees C GC program in conjunction with selected ion monitoring (SIM). The volatile organic species is sampled from the headspace of closed batch system vials and quantified by measuring the abundance of m/z 74. The method achieves a practical quantitation limit (PQL) for DMDO of 0.033 mM, and methyl acetate is identified as a minor decomposition product from the aqueous sample matrix, contributing 9% towards the overall DMDO measurements. The spectroscopic method makes use of common analytical instrumentation and is capable of measuring other in situ-generated dioxiranes, such as those generated from 2-butanone and [2H6]acetone.

Fate of ammonia in the atmosphere--a review for applicability to hazardous releases.

The physical and chemical mechanisms responsible for the removal of ammonia from the atmosphere have been reviewed. Capture by atmospheric moisture (clouds, rain, fog), surface water (rivers, lakes, seas), and deposition on vegetation and soil constitute the main pathways for ammonia removal from the troposphere. Ammonia catalyzes the atmospheric oxidation of sulfur dioxide to sulfur trioxide and reacts rapidly with acidic components of the atmosphere (sulfuric, nitric, and hydrochloric acids). The ammonium salts formed are the main components of smog aerosols and thus affect the opacity of the atmosphere and the earth radiation budget. Slow oxidation of ammonia in the atmosphere plays only a minor role in its removal. The data obtained for ammonia reactions under normal atmospheric conditions are generally applicable to model chemical reactions occurring during massive release of ammonia in the atmosphere, provided the impact of high ammonia concentration on the mass transfer processes that control some of these reactions, are taken into account.