Toxic Industrial Chemicals Research Articles

Development of fire model source terms and effects in the Hazard Prediction and Assessment Capability (HPAC) atmospheric transport and dispersion code

This paper describes a model which has been developed to represent the input of the products of combustion of large fires into the atmosphere, for subsequent calculation of the transport and dispersion by atmospheric processes. The objective was to have a model suitable for rapid implementation to support the needs of emergency responders. Consequently, the model characterizes the sources by a small number of parameters, which then define the rest of the model in terms of quantity and rate of release of products of combustion. There are two fundamental situations modeled – a hydrocarbon pool fire, and a building fire. The hydrocarbon pool fire is characterized by the area and mass, while the various forms of building fires are reduced to two: wooden buildings and steel-framed buildings, with further discrimination being made by area and duration of the fire. The building fires are assumed to be driven primarily by cellulosic materials, with the amount of such material being normalized to the floor area with parameters taken from the literature. A certain number of toxic contaminants, with levels as suggested by the firefighting literature, are provided in these models. The analyst can amend these levels, or ignore them, as desired. The models developed have been incorporated into the Defense Threat Reduction Agency (DTRA) Hazard Prediction and Capability (HPAC) code. This code breaks down the hazard prediction process into three components: 1) Generation of a source term describing the introduction of the contaminant to the atmosphere; 2) Transport, dispersion, and deposition of the contaminants by atmospheric processes, and; 3) Computation of the effects of the contaminant, usually at the surface. Source term generation modules includes such things as biological and nuclear warfare, and toxic industrial chemicals (TIC). The present work adds a fire module to the mix. • Fires are parameterized to minimize required inputs. • The model is sufficiently flexible that almost any contaminant can be added. • The building fire model is oriented to combustion of the whole building, rather than the contents of the building. • Atmospheric structural variability effects on transport are accounted for. • Doppler weather radar data from a real-world fire is consistent with this model.

Detection of Volatile Toxic Industrial Chemicals with Classical Ion Mobility Spectrometry and High-Kinetic Energy Ion Mobility Spectrometry.

Due to their high sensitivity and compact design, ion mobility spectrometers are widely used to detect toxic industrial chemicals (TICs) in air. However, when analyzing complex gas mixtures, classical ion mobility spectrometry (IMS) suffers from false-positive rates due to limited resolving power or false-negative rates caused by competitive ion-molecule reactions and the resulting suppression of certain analyte ions. To overcome these limitations, high-kinetic energy IMS (HiKE-IMS) was introduced some years ago. In contrast to classical IMS, HiKE-IMS is operated at decreased pressures of 20···60 mbar and high reduced electric field strengths E/N of up to 120 Td. Under these conditions, the influence of competitive ion-molecule reactions on the prevailing ion population should be less pronounced, thus reducing false negatives. Additionally, effects such as fragmentation and field-dependent ion mobility may help to reduce false positives. In this work, the capabilities and limitations of HiKE-IMS in the field of on-site detection of the volatile TICs NH3, HCN, H2S, HCl, NO2, Cl2, and SO2 are evaluated for the first time. Based on the limits of detection and the extent of spectral and chemical cross-sensitivities in gas mixtures, the results obtained for HiKE-IMS are compared with those obtained for classical IMS. It is shown that HiKE-IMS is less sensitive in comparison to classical IMS. However, when used for TIC detection, the reduced sensitivity of HiKE-IMS is not a major drawback. With values around 1 ppmv, the achievable limits of detection for almost all TICs are below the AEGL-2 (4h) levels. Furthermore, in comparison to classical IMS, it is still striking that HiKE-IMS shows significantly less spectral and chemical cross-sensitivities and thus exhibits considerably lower false-positive and false-negative rates. Overall, it thus turns out that HiKE-IMS is a promising alternative to classical IMS in the field of on-site detection of TICs.

Management of Chemical Terrorism and Chemical Disasters

Though the possibility of terrorist groups obtaining chemical weapons and inflicting mass destruction is relatively low, the relevance of chemical agents remains high since the use of such chemical agents in causing potentially dangerous consequences remains very high. Sporadic chemical attacks and chemical disasters happen all over the world, and they cause long-lasting damages. Easy accessibility to various toxic industrial chemicals and the relatively simple know-how needed to synthesize chemical agents pose a serious threat. However, technological developments and the easy availability of information have empowered the security forces and law enforcement agencies to formulate a responsive mechanism to mitigate the ill effects of chemical disasters. Though the international and national agencies strive hard to ward off the debilitating effects of chemical agents and disasters, such efforts' capability to address the potential risks remains doubtful. This review describes the characteristics and classification of chemical agents and toxic industrial chemicals, their physicochemical properties, detection, decontamination, and response by the security agencies and first responders in addressing the threat to humanity in the form of chemical terrorism and chemical disasters.

Identifying UiO-67 Metal-Organic Framework Defects and Binding Sites through Ammonia Adsorption.

Ammonia is a widely used toxic industrial chemical that can cause severe respiratory ailments. Therefore, understanding and developing materials for its efficient capture and controlled release is necessary. One such class of materials is 3D porous metal-organic frameworks (MOFs) with exceptional surface areas and robust structures, ideal for gas storage/transport applications. Herein, interactions between ammonia and UiO-67-X (X: H, NH2 , CH3 ) zirconium MOFs were studied under cryogenic, ultrahigh vacuum (UHV) conditions using temperature-programmed desorption mass spectrometry (TPD-MS) and in-situ temperature-programmed infrared (TP-IR) spectroscopy. Ammonia was observed to interact with μ3 -OH groups present on the secondary building unit of UiO-67-X MOFs via hydrogen bonding. TP-IR studies revealed that under cryogenic UHV conditions, UiO-67-X MOFs are stable towards ammonia sorption. Interestingly, an increase in the intensity of the C-H stretching mode of the MOF linkers was detected upon ammonia exposure, attributed to NH-π interactions with linkers. These same binding interactions were observed in grand canonical Monte Carlo simulations. Based on TPD-MS, binding strength of ammonia to three MOFs was determined to be approximately 60 kJ mol-1 , suggesting physisorption of ammonia to UiO-67-X. In addition, missing linker defect sites, consisting of H2 O coordinated to Zr4+ sites, were detected through the formation of nNH3 ⋅H2 O clusters, characterized through in-situ IR spectroscopy. Structures consistent with these assignments were identified through density functional theory calculations. Tracking these bands through adsorption on thermally activated MOFs gave insight into the dehydroxylation process of UiO-67 MOFs. This highlights an advantage of using NH3 for the structural analysis of MOFs and developing an understanding of interactions between ammonia and UiO-67-X zirconium MOFs, while also providing directions for the development of stable materials for efficient toxic gas sorption.

International trends in systemic human exposures to 2,4 dinitrophenol reported to poisons centres

Background 2,4 dinitrophenol (DNP) is a toxic industrial chemical that reduces body weight and body fat by uncoupling oxidative phosphorylation but at the risk of severe dose-related toxicity. Increases in human DNP exposures have been reported in the United Kingdom, the United States and Australia in recent years, but little information is available for other countries. This study was performed in collaboration with the World Health Organization (WHO) to establish international rates of systemic DNP-related exposures and deaths, as reported to poisons centres. Methods Poison Centres listed in the WHO Directory of Poison Centres were contacted by email. Data were requested on numbers of enquiries relating to systemic DNP exposure by year, sex and clinical outcome (fatal/non-fatal) for the period January 2010 to September 2020. Results Responses were received from poisons centres in 38 countries which reported 456 separate cases of DNP exposure (303 male, 125 female, 28 sex not reported). Annual case numbers increased from 4 in 2010 to 71 in 2015, with subsequent reductions to 53 in 2019. On a population basis, case rates were higher in Australasia, Europe and North America than in Asia, Africa, and South or Central America, but with substantial differences in rates between countries within the same continent. When mortality data was available, case fatality was high (11.9%, 95% CI 9.0, 15.4) with no significant difference between females (11.3%, 95% CI 6.4, 18.9) and males (12.6%; 95% CI 9.1, 17.1; odds ratio 0.86, 95% 0.45, 1.73, p = 0.72). Conclusions Substantial increases in calls to poisons centres regarding human systemic exposures to DNP internationally between 2010 and 2015, especially those in Europe, Australia and North America, with fatal outcomes common. Countries affected should consider appropriate additional measures to further reduce the risk of human exposure to this hazardous chemical.

Revisiting the 1970 smallpox outbreak in Meschede, Germany: Lessons for a post-COVID world.

When people think about hazards, the types that easily come to their mind include natural hazards, such as earthquakes, tornados, and tsunamis, and manmade ones, such as plane crashes, bomb explosions, and exposure to toxic industrial chemicals. Disease outbreaks are a source of hazards that are often overlooked, and the largely forgotten smallpox was an example of such disease. This article provides a review of the emergency management practices that curtailed the potentially devastating spread of smallpox at Meschede, Germany in 1970. Lessons that can be transferred to the COVID-19 pandemic are also discussed.

High‐throughput computational screening of porous polymer networks for natural gas sweetening based on a neural network

AbstractThe capture and storage of toxic industrial chemicals such as H2S using porous polymer networks (PPNs) has shown promising application because of their high porosity, high surface area, high stability, low‐cost and lightweight. In this work, 17,846 PPNs with the diamond‐like topology were computationally screened to identify the optimal adsorbents for the removal of H2S and CO2 from humid natural gas based on the combination of molecular simulation and machine learning algorithms. The top‐performing PPNs such as hPAFs‐0201 with the highest adsorption performance scores (APS) were evaluated and identified based on their adsorption capacities and selectivity for H2S and CO2. The strong affinity between water molecules and the framework atoms in a few PPNs has a significant impact on the adsorption selectivity of acid gases. Based on decision tree analysis, we found two main design paths of the optimal PPNs for natural gas sweetening, which are the PPNs with LCD ≤ 4.648 Å, Vf ≤ 0.035, and PLD ≤ 3.889 Å, and those with 4.648 Å ≤ LCD ≤ 5.959 Å, ρ ≤ 837 kg m−3. In addition, we constructed different machine learning models, particularly artificial neural network, available to accurately predict the APS of PPNs. 2D projection map of geometrical properties of PPNs using the t‐distributed stochastic neighbor embedding (t‐SNE) method shows that the screened 390 samples exhibit the similar structures. Among the top‐23 PPNs with the highest APS, hPAFs‐0201 has enhanced natural gas sweetening performance due to its strong affinity between the N‐rich organic linkers and acid gases. hPAFs‐0752 shows the highest isosteric adsorption heat of H2S and CO2 (Q°st = 49.84 kJ mol−1), resulting in its second‐highest APS as well as high hydrophilicity. Based on the combination of molecular simulation and machine learning, comprehensive insights into the high‐throughput screening of PPNs in this work will provide new ideas for the design of high‐performance PPNs for gas separation.

Utilizing Zirconium MOF-functionalized Fiber Substrates Prepared by Molecular Layer Deposition for Toxic Gas Capture and Chemical Warfare Agent Degradation.

Metal–organic frameworks (MOFs) are a class of porous organic‐inorganic solids extensively explored for numerous applications owing to their catalytic activity and high surface area. In this work MOF thin films deposited in a one‐step, molecular layer deposition (MLD), an all‐gas‐phase process, on glass wool fibers are characterized by X‐ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and their capabilities towards toxic industrial chemical (TIC) capture and chemical warfare agents (CWA) degradation are investigated. It is shown that despite low volume of the active material used, MOFs thin films are capable of removal of harmful gaseous chemicals from air stream and CWA from neutral aqueous environment. The results confirm that the MLD‐deposited MOF thin films, amorphous and crystalline, are suitable materials for use in air filtration, decontamination, and physical protection against CWA and TIC.

Identification of Novel Simulants for Toxic Industrial Chemicals and Chemical Warfare Agents for Human Decontamination Studies: A Systematic Review and Categorisation of Physicochemical Characteristics.

Chemical simulants have long been used in human trials of mass decontamination to determine the efficacy of decontamination interventions against more toxic agents. Until now, reliance has mostly been on individual chemicals as surrogates to specific agents (e.g., methyl salicylate for sulphur mustard). A literature review was conducted to identify chemicals that had been previously tested on human volunteers and that represent diverse physicochemical characteristics in order to create a repository for chemical simulants. Of the 171 unique chemicals identified, 78 were discounted for the risk they could pose to human volunteers, 39 were deemed suitable for use, and a further 54 were considered to be possible simulants but would require further research. Suitable simulants included both solid and liquid chemicals spanning a wide range of physicochemical properties including molecular weight, octanol/water partition coefficient, vapour pressure, and solubility. This review identifies an array of potential simulants suitable for use in human volunteer decontamination studies and is of relevance to future studies on systemic absorption and surface decontamination.

Fast Sensing of Hydrogen Cyanide (HCN) Vapors Using a Hand-Held Ion Mobility Spectrometer with Nonradioactive Ionization Source.

Sensitive real-time detection of vapors produced by toxic industrial chemicals (TICs) always represents a stringent priority. Hydrogen cyanide (HCN) is definitely a TIC, being widely used in various industries and as an insecticide; it is a reactive, very flammable, and highly toxic compound that affects the central nervous system, cardiovascular system, eyes, nose, throat, and also has systemic effects. Moreover, HCN is considered a blood chemical warfare agent. This study was focused toward quick detection and quantification of HCN in air using time-of-flight ion mobility spectrometry (ToF IMS). Results obtained clearly indicate that IMS can rapidly detect HCN at sub-ppmv levels in air. Ion mobility spectrometric response was obtained in the negative ion mode and presented one single distinct product ion, at reduced ion mobility K0 of 2.38 cm2 V−1 s−1. Our study demonstrated that by using a miniaturized commercial IMS system with nonradioactive ionization source model LCD-3.2E (Smiths Detection Ltd., London, UK), one can easily measure HCN at concentrations of 0.1 ppmv (0.11 mg m−3) in negative ion mode, which is far below the OSHA PEL-TWA value of 10 ppmv. Measurement range was from 0.1 to 10 ppmv and the estimated limit of detection LoD was ca. 20 ppbv (0.02 mg m−3).

Gaps in toxic industrial chemical model systems: Improvements and changes over past 10 years

AbstractTo assess the hazards of the releases of toxic industrial chemicals (TICs) to the atmosphere, comprehensive model systems are often used, which begin with the scenario definition and end with an estimate of health risk. In 2008 and 2010, the US Department of Homeland Security and Defense Threat Reduction Agency sponsored reports that identified knowledge gaps in TIC modeling. The current paper discusses which of the knowledge gaps were satisfactorily resolved in the past 10 years by new theoretical and experimental research, such as the 2010 and 2015–2016 Jack Rabbit field experiments. For example, the linked source emissions and transport and dispersion (T&D) models have been shown, in comparisons with Jack Rabbit II observations, to not have large mean biases. Consequently, the T&D models are less likely to be the cause of model system overpredictions of casualties observed after large TIC accidental releases, such as the Festus, Macdona, and Graniteville chlorine railcar incidents. It may be that the deposition models and/or the health effects models still need improvement. In addition to comments on the knowledge gaps identified 10 years ago, a few new knowledge gaps are addressed, such as indoor T&D and deposition, and estimating the magnitude of the saturation deposition value for various substrates and chemicals.

Comparative efficacy of Reactive Skin Decontamination Lotion (RSDL): A systematic review

Due to threats posed by Chemical Warfare Agents (CWAs) and accidents with Toxic Industrial Chemicals (TICs), the need for highly effective skin decontamination remains relevant. Reactive Skin Decontamination Lotion (RSDL), composed of Dekon 139 and 2,3-butanedione monoxime, has been shown highly effective against CWAs and TICs. This systematic review compares RSDL efficacy to other decontaminating agents. Online search engines PubMed, Web of Science, and Embase were explored, and all literature containing quantitative data, comparing RSDL to other decontaminating agents, investigated. Year of publication, type of study (in vitro or in vivo), model (animal or human), toxin tested, and result of each relevant article were recorded. In total, 15 relevant papers, comprising a total of 18 experimental models, were identified. Nine studies concluded that RSDL was the most effective decontaminant tested against the toxin of interest. Four studies concluded that RSDL was not the most effective decontaminant tested against the toxin of interest. The remaining 5 studies concluded RSDL displayed similar efficacy to at least one of the other decontaminating agents tested against the toxin of interest. There is substantial evidence supporting the efficacy of RSDL as a decontaminating agent. However, there remains to be insufficient data on this important topic, and limitations on the usefulness of current data, when applied to the broad array of potential exposures.

Wearable Chemical Sensor Badge

Objectives Under this program, a wearable chemical detection badge capable of detecting and alarming (visual + audible/vibratory) in the presence of relevant concentrations of toxic industrial chemicals (TICs) in air has been developed and demonstrated for ammonia, chlorine, hydrogen sulfide, and nitrogen dioxide. The badge will alarm via one of the user-chosen alarm modes in the presence of ½ Immediately Dangerous to Life or Health (1/2 IDLH) concentrations of these TICs in under 5 minutes. The technology operates in harsh environmental conditions (10-90% RH, -10 – 50 oC) and in the presence of interferents (e.g. smoke, fuels, bleach and diesel exhaust). The active sampling badge consists of a reusable detection device that is used in conjunction with a disposable colorimetric sensor coupon. The sensor badge is unobtrusive and can be worn in the breathing zone of the user with hands-free operation for up to 8 hours on battery power. Results Small prototype devices (2” x 2” x 0.5”) were manufactured based on feedback from expert first responder personnel. Key points from this feedback include: Must have a low false alarm rate; no nuisance level alarms (e.g. PEL)Alarm must be very visible/noticeableMust be small and unobtrusiveData logging would be beneficial for analysis at a later time Prototype devices and associated sensor coupons were tested in the presence of PEL, ½ IDLH, and multiple IDLH concentrations of the target TIC analytes (ammonia, chlorine, hydrogen sulfide, and nitrogen dioxide) under harsh environmental conditions: -10 oC, ~ 90%RH 23 oC, 10% RH/50% RH/90% RH 50 oC, 10% RH/50% RH/90% RHand in the presence of environmental interferents including smoke (burning wood), diesel exhaust, diesel fuel and bleach. Utilizing four interrogation bands of the visible spectrum and combinatorial colorimetric response alarm criteria, the prototype badges performed well with no false positive or false negative alarms due to environmental interferent exposure, nuisance level (PEL) exposure, or harsh environmental conditions. Conclusion/Significance First Responders under duress need a simple, low-cost, rugged device capable of detecting the presence of harmful levels of Toxic Industrial Chemicals (TICs) with high fidelity while avoiding nuisance level alarms (e.g. OSHA PEL) and false alarms due to environmental contaminants (e.g. smoke, fuels, diesel exhaust). This prototype sensor technology fills an unmet need for the first responder and is adaptable for the incorporation of new sensors in the future. Figure 1

Fluorinated Bisphenol Sorbent Materials for Spectroscopic Chemical Threat Sensing and Photonics Applications

Alcoholic and phenolic hydrogen-bond (HB) acidic absorbents activated by fluorine chemistries have been previously developed at the U.S. Naval Research Laboratory and elsewhere to augment sorbent HB acidity, reduce sorbent HB basicity and target complementary HB basicity of a wide range of hazardous target chemicals. A significant limitation of HB sorbents developed to date has been the propensity for sorbent self-association. This intermolecular bonding between sorbent molecules hinders sorbate access to active HB acid sites in the sorbent, limiting its overall efficacy. Sorbent self-association is evidenced by broadened hydroxyl peaks in the mid-infrared (MIR) region, which can obscure important absorption frequencies that appear upon absorption of an analyte into the sorbent. In this current work our aim is to develop improved HB acidic sorbent compounds which minimize undesired sorbent self-association in order to apply these sorbents to infrared- and Raman-based sensing devices for chemical threat detection.A series of new HB acidic sorbents have been synthesized and the subsequent sorbent-sorbate interactions have been characterized by a number of methods. MIR spectroscopy has been used to help elucidate sorbent-analyte vapor interactions. The newly synthesized sorbents have been challenged with various analyte vapors, including toxic industrial chemicals, chemical warfare agent simulants, and background interferents. A particular focus of these characterization efforts has been to observe the spectral changes that occur in the hydroxyl region of the MIR upon exposure of a sorbent material to an analyte vapor. Analyte binding of an HB base occurs principally at the sorbent hydroxyl site. The resulting redshift of the hydroxyl stretching frequency is characteristic of the basicity of the analyte.These sorbent materials are specifically designed to be selective toward hazardous chemicals through complementary hydrogen-bonding interactions between sorbent and analyte molecules. Generally, common interferents, such as hydrocarbons, have little or no hydrogen-bond basicity, while hazardous chemicals of interest have moderate to high basicity. More strongly HB basic analytes trigger larger redshifts of the hydroxyl absorption frequency. Benchtop FTIR characterization has confirmed that these newly designed sorbent materials are responsive to threat chemicals of interest at low concentrations and largely unresponsive to interferent chemicals, even at relatively high concentrations.Based on the strong affinity of these sorbents to threat chemicals of interest and the significant spectral changes that occur in the MIR upon formation of the hydrogen-bonded complex, these sorbent materials make useful candidates for MIR sensing applications. A frequency shift of the hydroxyl stretch indicates a sorbate has formed a HB with the sorbent. The magnitude of the frequency shift correlates with the basicity of the analyte, which is indicative of the class of compound to which the newly bound chemical belongs. In a sensing application, this feature can provide an alert that a hazardous chemical is present, even if it is an unknown threat. While the hydroxyl region allows for class specificity of unknown compounds, the fingerprint region complexity may facilitate specific analyte recognition. At present, this work has been focused on analysis of the hydroxyl region and distinction of different classes of compounds, but future efforts will turn to the fingerprint region to provide an avenue for specific chemical identification.Raman spectroscopy has also been used to characterize these sorbent materials. Specifically, a technique known as waveguide-enhanced Raman spectroscopy (WERS) has been used, which features the use of highly evanescent, low-loss waveguides with the sorbent material as a top cladding.2 WERS can be achieved using an incredibly small footprint with a sorbent-functionalized nanophotonic waveguide that is approximately a few centimeters long. Using WERS, the differential Raman spectra of the sorbent material interacting with different chemical warfare agent simulants has been measured at parts-per-billion detection levels. The spectra exhibit extrapolated three-sigma detection limits as low as 3 ppb. Continuing efforts are focused on adapting this technique to photonic integrated circuit-based fabrication and chip-scale Raman spectroscopy for trace chemical vapor detection.This presentation will highlight the design of these next-generation sorbents as a tool to facilitate MIR- and Raman-based sensing of threat chemicals. It will focus on analyzing sorbent-analyte spectral interactions and discuss how to exploit these features to develop MIR- and Raman-based sensors.

Designing Oxide Aerogels With Enhanced Sorptive and Degradative Activity for Acute Chemical Threats

Oxide aerogels are pore–solid networks notable for their low density, large pore volume, and high surface area. This three-dimensional arrangement of pore and solid provides critical properties: the high surface area required to maximize the number of active sites and a through-connected porosity that plumbs reactants to the active interior. In decontamination applications where reactivity beyond adsorption is desired to degrade deleterious molecules, oxide aerogels offer multiple avenues to add oxidative power to this unique arrangement of pore and solid. For protection against chemical warfare agents or toxic industrial chemicals, metal-oxide aerogels with their oxide/hydroxide surfaces afford stability under ambient conditions against competing sorbents such as water and oxygen. In this review, strategies to maximize sorptive capacity and degradation rate by modifying surface functionality, compositing with dissimilar oxides, or adding metallic nanoparticles and the subsequent impact on decontamination performance will be summarized and expected directions for future research will be discussed based on the observed trends.

Preliminary assessment of chlorine reactivity with environmental materials accounting for boundary layer and maximum deposition effects

Many toxic industrial chemicals (TICs) such as chlorine and ammonia are very reactive with commonly encountered materials in the environment. The amount of TIC material reacted in the environment is an important factor in determining the impact of a release. Typically characterized with a dry deposition rate in atmospheric dispersion models, the reaction rate has predominately been studied in field scale experiments at concentration levels typical for air pollution (ppm levels). When considering the removal of chlorine by (dry) deposition in an episodic release, gas phase concentrations will be much higher than those associated with air pollution, and near-field reaction of chlorine with local vegetation will be strongly influenced by the response of leaves and other elements of the surface “canopy” to those high concentrations. In this work, standard engineering methods characterizing the rate of mass transfer from a fluid to a surface in conjunction with reaction at that surface are applied. Previous experimental programs that studied the removal of chlorine under conditions relevant to this study show that deposition of chlorine to plant material can reach a limiting maximum so that the plant material can no longer react with gaseous chlorine despite continued exposure. In the analysis presented here, it is shown that the effect of the maximum deposition can be treated using the same approach as has been used to model catalyst poisoning. This study developed a model to account for boundary layer resistance and the impact of maximum deposition in a framework that could be incorporated in atmospheric dispersion models. To test the efficacy of this model, the Controlled Environment Reactivity Test (CERT) apparatus was designed to expose selected environmental materials (substrates including soil, rye grass, white clover, maple leaves, and spruce branches) to chlorine with initial concentration of (nominally) 1000 ppm where the gas phase chlorine concentration can be measured as a function of time to determine relevant modeling parameters. The apparatus was built to control the flow velocity of the chlorine/air mixture over the experimental substrates with turbulence levels that are comparable to the atmosphere. Model parameters were found for the environmental materials tested.

An Amidoxime-Functionalized Porous Reactive Fiber against Toxic Chemicals

The prevalence of toxic chemicals, ranging from chemical warfare agents (CWAs) to toxic industrial chemicals (TICs), emphasizes the importance of developing materials that can address these threats...

Numerical Design and Investigation of Circularly Segmented Air Holes-Assisted Hollow-Core Terahertz Waveguide as Optical Chemical Sensor

In this paper,a polarization-maintaining single-mode rectangular-shaped hollow-core waveguide with four segmented air cladding in the terahertz (THz) regime is presented for detecting various toxic industrial chemicals. A new type of injection moldable cyclic olefin copolymer, commercially named as TOPAS is used as the base fiber material for its high optical transmission and high resistance to other chemicals. The finite element method with a perfectly matched layer as the boundary condition is employed for numerical explorations. The proposed sensor exhibits ultra-high relative sensitivity of 99.73% and ultra-low effective material loss of 0.007 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> at 1.6 THz frequency for Toluene in y polarization. This sensor also evinces a high birefringence of 4.16×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> at 1.6 THz frequency. A maximum V parameter of 2.224 has been found at 2.2 THz which ensures the single-mode propagation of light. The sensor shows a very low confinement loss of 3.2×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-11</sup> dB/m and a high numerical aperture of 0.3574 at 1.6 THz frequency for Hydrogen Sulfide. This paper also concentrates on other important design parameters such as bending loss, mode field radius, beam divergence and effective area for serviceability of the sensor in the THz region. This sensor can be a very good candidate for various chemical detection as well as other applications in the terahertz regime.

The Optoelectronic Nose.

How does one tell the difference between one molecule or mixture of molecules from another? Chemical sensing seeks to probe physical or chemical properties of molecular or ionic species (i.e., analytes) and transform that information into a useful and distinguishable output. The olfactory system of animals is the prototype of chemical sensing. Even for human beings (who are generally more visual than olfactory creatures), the sense of smell is one of our most basic capabilities, and we can discriminate among many thousands, and possibly even billions, of different odors. The chemical specificity of the olfactory system does not come from specific receptors for specific analytes (i.e., the traditional lock-and-key model of enzyme-substrate interactions), but rather olfaction uses pattern recognition of the combined responses of several hundred olfactory receptors.In analogy to olfaction, colorimetric sensor arrays provide high dimensional data from the color changes of chemically responsive colorants as they are exposed to analytes. These colorants include pH responsive dyes, Lewis acid/base indicators, redox dyes, vapochromics, and surface-modified silver nanoparticles. The color difference maps so created provide chemical sensing with high sensitivity (often down to ppb levels), impressive discrimination among very similar analytes, and exquisite fingerprinting of extremely similar mixtures over a wide range of analyte types, both in the gas and liquid phases. Such colorimetric arrays probe a wide range of the chemical reactivity of analytes, rather than the limited dimensionality of physical properties (e.g., mass) or physisorption (e.g., traditional electronic noses). Our sensor arrays are disposable and simple to produce by either inkjet or robotic dip-pen printing onto the surface of porous polymer membranes or even paper.Design of both sensor arrays and optical readers for their analysis has advanced to a fully self-contained pocket-sized instrument, the optoelectronic nose. Quantitative analysis requires appropriate chemometric methods for pattern recognition of data with inherently high dimensionality, e.g., hierarchical cluster analysis and support vector machines. A wide range of applications for the colorimetric sensor arrays has been developed, including personal dosimetry of toxic industrial chemicals, detection of explosives or fire accelerants, monitoring pollutants for artwork and cultural heritage preservation, quality control of foods and beverages, rapid identification of bacteria and fungi, and detection of disease biomarkers in breath or urine. The development of portable, high-accuracy instrumentation using standard imaging devices with the capability of onboard, real-time analysis has had substantial progress and increasingly meets the expectations for real-world use.

Hunting for Toxic Industrial Chemicals: Real-Time Detection of Carbon Disulfide Traces by Means of Ion Mobility Spectrometry

Sensitive real-time detection of vapors produced by toxic industrial chemicals (TICs) represents a stringent priority nowadays. Carbon disulfide (CS2) is such a chemical, being widely used in manufacturing synthetic textile fibers and as a solvent. CS2 is simultaneously a very reactive, highly flammable, irritant, corrosive, and highly toxic compound, affecting the central nervous system, cardiovascular system, eyes, kidneys, liver, skin, and reproductive system. This study was directed towards quick detection and quantification of CS2 in air, using time-of-flight ion mobility spectrometry (IMS); photoionization detection (PID) was also used as confirmatory technique. Results obtained indicated that IMS can detect CS2 at trace levels in air. The ion mobility spectrometric response was in the negative ion mode and presented one product ion, at a reduced ion mobility (K0) of 2.25 cm2 V−1 s−1. Our study demonstrated that by using a portable, commercial IMS system (model Mini IMS, I.U.T. GmbH Berlin Germany) one can easily measure CS2 at concentrations of 0.1 ppmv (0.3 mg m−3) in the negative ion mode, which is below the lowest threshold value of 1 ppmv given for industrial hygiene. A limit of detection (LOD) of ca. 30 ppbv (0.1 mg m−3) was also estimated.