Cyanide Emission Research Articles

Modelling CN Zeeman effect observations of the envelopes of a low-mass protostellar disc and a massive protostar

ABSTRACT We use the polaris radiative transfer code to produce simulated circular polarization Zeeman emission maps of the cyanide (CN) J = 1–0 molecular line transition for two types of protostellar envelope magnetohydrodynamic simulations. Our first model is a low-mass disc envelope system (box length L = 200 au), and our second model is the envelope of a massive protostar (L = 104 au) with a protostellar wind and a CN-enhanced outflow shell. We compute the velocity-integrated Stokes I and V, as well as the implied V/I polarization percentage, for each detector pixel location in our simulated emission maps. Our results show that both types of protostellar environments are in principle accessible with current circular polarization instruments, with each containing swaths of envelope area that yield percentage polarizations that exceed the 1.8 per cent nominal sensitivity limit for circular polarization experiments with the Atacama Large Millimeter/submillimeter Array. In both systems, high-polarization (≳1.8 per cent) pixels tend to lie at an intermediate distance away from the central star and where the line-centre opacity of the CN emission is moderately optically thin (τLC ∼ 0.1–1). Furthermore, our computed V/I values scale roughly with the density-weighted mean line-of-sight magnetic field strength, indicating that Zeeman observations can effectively diagnose the strength of envelope-scale magnetic fields. We also find that pixels with large V/I are preferentially co-located where the absolute value of the velocity-integrated V is also large, suggesting that locations with favourable percentage polarization are also favourable in terms of raw signal.

Biological hydrogen cyanide emission globally impacts the physiology of both HCN-emitting and HCN-perceiving Pseudomonas.

Bacteria communicate by exchanging chemical signals, some of which are volatile and can remotely reach other organisms. HCN was one of the first volatiles discovered to severely impact exposed organisms by inhibiting their respiration. Using HCN-deficient mutants in two Pseudomonas strains, we demonstrate that HCN's impact goes beyond the sole inhibition of respiration and affects both emitting and receiving bacteria in a global way, modulating their motility, biofilm formation, and production of antimicrobial compounds. Our data suggest that bacteria could use HCN not only to control their own cellular functions, but also to remotely influence the behavior of other bacteria sharing the same environment. Since HCN emission occurs in both clinically and environmentally relevant Pseudomonas, these findings are important to better understand or even modulate the expression of bacterial traits involved in both virulence of opportunistic pathogens and in biocontrol efficacy of plant-beneficial strains.

Mercury mitigation and unintended consequences in artisanal and small-scale gold mining

The increased research attention on estimating the global mercury use and emissions in artisanal and small-scale gold mining (ASGM) has improved awareness of the problems associated with ASGM. However, little attention has been paid to the specific effects of particular intervention strategies to mitigate global mercury use and emissions in accordance with the Minamata Convention on Mercury. In this study, we examine the effect of each type of intervention (concentrate amalgamation, use of a retort, and the cyanidation technique). The results show that, despite the massive reduction in mercury emissions associated with the implementation of the retort and cyanidation technique, these interventions created new critical issues. As unintended outcome of these interventions, there has been a significant increase in the quantity of global mercury which needs to be properly and permanently managed as a waste (< 1740 Mg in 2050) and also in global hydrogen cyanide emissions (< 46,700 Mg in 2050). The findings of this study indicate that, when taking these measures alone, efforts to mitigate mercury use and emissions in accordance with the Minamata Convention on Mercury generate different risks which, in effect, jeopardize sustainability in ASGM. Comprehensive mercury mitigation strategies which also consider these unintended consequences should be included in the action plans adopted by policymakers at the national level.

Vertically extended and asymmetric CN emission in the Elias 2-27 protoplanetary disk

Context. Cyanide (CN) emission is expected to originate in the upper layers of protoplanetary disks, tracing UV-irradiated regions. This hypothesis, however, has been observationally tested only in a handful of disks. Elias 2-27 is a young star that hosts an extended, bright, and inclined disk of dust and gas. The inclination and extreme flaring of the disk make Elias 2-27 an ideal target to study the vertical distribution of molecules, particularly CN. Aims. Our aim is to directly trace the emission of CN in the disk around Elias 2-27 and compare it to previously published CO isotopolog data of the system. The two tracers can be combined and used to constrain the physical and chemical properties of the disk. Through this analysis we can test model predictions of CN emission and compare observations of CN in other objects to the massive, highly flared, asymmetric, and likely gravitationally unstable protoplanetary disk around Elias 2-27. Methods. We analyzed CN N = 3–2 emission in two different transitions J = 7/2–5/2 and J = 5/2–3/2, for which we detect two hyperfine group transitions. The vertical location of CN emission was traced directly from the channel maps, following geometrical methods that had been previously used to analyze the CO emission of Elias 2-27. Simple analytical models were used to parameterize the vertical profile of each molecule and study the extent of each tracer. From the radial intensity profiles we computed radial profiles of column density and optical depth. Results. We show that the vertical location of CN and CO isotopologs in Elias 2-27 is layered and consistent with predictions from thermochemical models. A north-south asymmetry in the radial extent of the CN emission is detected, which is likely due to shadowing on the north side of the disk. Combining the information from the peak brightness temperature and vertical structure radial profiles, we find that the CN emission is mostly optically thin and constrained vertically to a thin slab at z/r ~ 0.5. A column density of 1014 cm−2 is measured in the inner disk, which for the north side decreases to 1012 cm−2 and for the south side to 1013 cm−2 in the outer regions. Conclusions. In Elias 2-27, CN traces a vertically elevated region above the midplane, very similar to that traced by 12CO. The inferred CN column densities, low optical depth (τ ≤ 1), and location near the disk surface are consistent with thermo-chemical disk models in which CN formation is initiated by the reaction of N with UV-pumped H2. The observed north–south asymmetry may be caused by either ongoing infall or by a warped inner disk. This study highlights the importance of tracing the vertical location of various molecules to constrain the disk physical conditions.

Wind Turbine Blades Using Recycled Carbon Fibers: An Environmental Assessment.

Polymers reinforced with virgin carbon fibers (VCF) are being used to make spar caps of wind turbine (WT) blades and polymers with glass fibers (GF) to make skins of the blade components. Here, we assess the life cycle environmental performance of the hybrid blades with spar caps based on VCF and the shells and shear webs based on RCF (recycled CF) composites (RCF-hybrid). The production of the WT blades and associated reinforced polymers is assumed to occur in Sweden, with their uses and end-of-life management in the European region. The functional unit is equivalent to three blades in an offshore WT with the market incumbent blades solely based on the GF composite or the hybrid option. The RCF-hybrid blades offer 12-89% better environmental performance in nine out of 10 impact categories and 6-26% better in six out of 10 impact categories. The RCF-hybrid blades exhibit optimum environmental performance when the VCF manufacturing facilities are equipped with pollution abatement systems including regenerative thermal oxidizers to reduce ammonia and hydrogen cyanide emissions; spar caps are made using VCF epoxy composites through pultrusion and resin infusion molding, and the blade scrap is mechanically recycled at the end of life. The energy and carbon payback times for the RCF-hybrid blades were found to be 5-13% lower than those of the market incumbents.

On Estimation of Contamination from Hydrogen Cyanide in Carbon Monoxide Line-intensity Mapping

Abstract Line-intensity mapping surveys probe large-scale structure through spatial variations in molecular line emission from a population of unresolved cosmological sources. Future such surveys of carbon monoxide line emission, specifically the CO(1-0) line, face potential contamination from a disjointed population of sources emitting in a hydrogen cyanide emission line, HCN(1-0). This paper explores the potential range of the strength of HCN emission and its effect on the CO auto power spectrum, using simulations with an empirical model of the CO/HCN–halo connection. We find that effects on the observed CO power spectrum depend on modeling assumptions but are very small for our fiducial model, which is based on current understanding of the galaxy–halo connection. Given the fiducial model, we expect the bias in overall CO detection significance due to HCN to be less than 1%.

The Problems of Emission of Hydrogen Cyanide Reduction in the Production of Coke

Escaped in the production of coke hydrogen cyanide is toxic dangerous substance. And control of its content during the process is very difficult. There were considered urgent tasdks associated with a reduction in the negative impact of hydrogen cyanide emissions generated in the production of coke-chemical production that are solved with the help of mathematical modelling. There was offered sert of effective measures to ensure the reduction of hydrogen cyanide emissions by chimneys of coke battareis. There was elaborated mathematical model of formation of hydrogen cyanide, which provides the relationship of vhemical kinetics and thermodynamics of the process, wehich allows to identify ways to ensure stable operation of coke battareis.

IRAS 16293−2422: Evidence for Infall onto a Counterrotating Protostellar Accretion Disk

We report high spatial resolution VLA observations of the low-mass star-forming region IRAS 16293-2422 using four molecular probes: ethyl cyanide (CH3CH2CN), methyl formate (CH3OCHO), formic acid (HCOOH), and the ground vibrational state of silicon monoxide (SiO). Ethyl cyanide emission has a spatial scale of ~20'' and encompasses binary cores A and B as determined by continuum emission peaks. Surrounded by formic acid emission, methyl formate emission has a spatial scale of ~6'' and is confined to core B. SiO emission shows two velocity components with spatial scales less than 2'' that map ~2'' northeast of the A and B symmetry axis. The redshifted SiO is ~2'' northwest of blueshifted SiO along a position angle of ~135° which is approximately parallel to the A and B symmetry axis. We interpret the spatial position offset in red- and blueshifted SiO emission as due to rotation of a protostellar accretion disk, and we derive ~1.4 M☉ interior to the SiO emission. In the same vicinity, Mundy et al. also concluded rotation of a nearly edge-on disk from OVRO observations of much stronger and ubiquitous 13CO emission, but the direction of rotation is opposite to the SiO emission findings. Taken together, SiO and 13CO data suggest evidence for a counterrotating disk. Moreover, archival BIMA array 12CO data show an inverse P Cygni profile with the strongest absorption in close proximity to the SiO emission, indicating unambiguous material infall toward the counterrotating protostellar disk at a new source location within the IRAS 16293-2422 complex. The details of these observations and our interpretations are discussed.

High-Redshift HCN Emission: Dense Star-forming Molecular Gas in IRAS F10214+4724

Hydrogen cyanide emission in the J = 1–0 transition has been detected at redshift z = 2.2858 in IRAS F10214+4724 using the Green Bank Telescope. This is the second detection of HCN emission at high redshift. The large HCN line luminosity in F10214 is similar to that in the Cloverleaf (z = 2.6) and the ultraluminous infrared galaxies Mrk 231 and Arp 220. This is also true of the ratio of HCN to CO luminosities. The ratio of far-infrared luminosity to HCN luminosity, an indicator of the star formation rate per solar mass of dense gas, follows the correlation found for normal spirals and infrared luminous starburst galaxies. F10214 clearly contains a starburst that contributes, together with its embedded quasar, to its overall infrared luminosity. A new technique for removing spectral baselines in the search for weak, broad emission lines is presented.

Ammonia, nitrous oxide and hydrogen cyanide emissions from five passenger vehicles

In this paper, three unregulated components, ammonia, nitrous oxide and hydrogen cyanide, emitted from five passenger vehicles are investigated. With focus upon emission factors from existing production technology, vehicles produced between 1989 and 1998 with considerable mileage (7000 to 280,000) are chosen. Among the five vehicles, four were sold in the European market, whereas one was sold in the US market. The vehicles are tested on a chassis dynamometer. An EU2000 Driving Cycle (NEDC) and a US Urban Driving Cycle (UDC) of the Federal Test Procedure 75 (FTP-75) are used in the study. The regulated emissions are measured using a Horiba Mexa series. Unregulated emissions, ammonia (NH 3), nitrous oxide (N 2O) and hydrogen cyanide (HCN) are analysed by mass spectrometer, gas chromatography and CNT-NA, TIM315-74W method, respectively. Both the unregulated emissions and the regulated emissions show driving cycle dependency; and they are also improved with newer vehicle and emission control technology. However, a gasoline direct injection vehicle (relatively new technology in this study) has rather high regulated emissions, whereas the NH 3, N 2O and HCN emissions are low.

Kinematics of the Sagittarius B2(N-LMH) Molecular Core

Ethyl cyanide (CH3CH2CN) emission and absorption have been imaged with the Very Large Array toward Sagittarius B2(N-LMH) by means of the 515-414 rotational transition at 43.5 GHz (λ ~ 7 mm). The 15 × 14 VLA beam shows two principal sources of ethyl cyanide emission: an unresolved source ~5'' north of the LMH that is kinematically consistent with simple expansion, contraction, or small-scale turbulence, and the resolved LMH core source itself that shows kinematics indicating an edge-on rotating disk that extends ≥3'' (~0.1 pc) in the approximate east-west direction. A search for the 707-606 rotational transition of the amino acid glycine (NH2CH2COOH) at 43.7 GHz toward Sgr B2(N-LMH) gave negative results.

Fate of process solution cyanide and nitrate at three Nevada gold mines inferred from stable carbon and nitrogen isotope measurements

Stable isotope methods have been used to identify the mechanisms responsible for cyanide consumption at three heap-leach operations that process Carlin-type gold ores in Nevada, U.S.A. The reagent cyanide had δ15N values ranging from -5 to -2‰ and δ 13C values from -60 to -35‰. The wide δ13C range reflects the use by different suppliers of isotopically distinct natural-gas feedstocks and indicates that isotopes may be useful in environmental studies where there is a need to trace cyanide sources.In heap-leach circuits displaying from 5 to 98% consumption of cyanide, barren-solution and pregnant-solution cyanide were isotopically indistinguishable. The similarity is inconsistent with cyanide loss predominantly by HCN offgassing (a process that in laboratory experiments caused substantial isotopic changes), but it is consistent with cyanide retention within the heaps as solids, a process that caused minimal isotopic changes in laboratory simulations, or with cyanide oxidation, which also appears to cause minimal changes. In many pregnant solutions cyanide was carried entirely as metal complexes, which is consistent with ferrocyanides having precipitated or cyano-complexes having been adsorbed within the heaps. It is inferred that gaseous cyanide emissions from operations of this type are less important than has generally been thought and that the dissolution or desorption kinetics of solid species is an important control on cyanide elution when the spent heaps undergo rinsing. Nitrate, nitrite and ammonium had δ15N values of 1-16‰. The data reflect isotopic fractionation during ammonia offgassing or denitrification of nitrate–particularly in reclaim ponds–but do not indicate the extent to which nitrate is derived from cyanide or from explosive residues.

On OMC-1 temperatures determined from methyl cyanide observations

An analysis is performed on the J(k) = 12(k)-11(k) and 13(k)-12(k) transitions of methyl cyanide detected by other investigators in the direction of OMC-1. The original interpretation of those observations argues for the presence of two distinct temperature regions or possibly a temperature gradient within the cloud. The analysis presented here demonstrates that the observations of these particular molecular transitions are consistent with a single methyl cyanide emission region with a source kinetic temperature of 121.2 + or - 8.2 K and a molecular rotational temperature of 16.6 + or - 1.8 K.

Evaluation of sampling techniques for cyanide emissions.

Evaluation of sampling techniques for cyanide emissions.

On the oxidation of cyanides in the stack region of the blast furnace

Computed results are reported on the oxidation of KCN particles carried by blast furnace gas through the stack region of the furnace. The calculations were performed on the assumption that the oxidation process is mass transfer controlled, but proper allowance was made for the variable CO/CO2 ratios and temperatures to which the particles are exposed during their passage through the stack. The results of these calculations show that for cyanide particles in the range 0.02 to 0.1 cm in diameter the system may be extremely sensitive both to the temperature profiles and to the CO/CO2 ratios within the stack; thus the control of these parameters could provide a means of controlling cyanide emissions.