Isocyanic acid (HNCO) and its fate in the atmosphere: a review

Leslie, Michael David; Ridoli, Melanie; Murphy, J. G.; Borduas-Dedekind, Nadine

doi:10.1039/c9em00003h

Cited by 44 publications

(74 citation statements)

References 107 publications

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“…Because of the importance of isocyanic acid, HNCO, in terrestrial environments [1][2][3] and in the interstellar medium [4], spectra of this molecule and its singly charged ion HNCO + have been widely studied both experimentally and theoretically. A rather complete listing of the earlier spectroscopic work is given in a recent paper by Holzmeier et al [5] on its normal and resonant Auger spectra.…”

Section: Introductionmentioning

confidence: 99%

Double and Triple Ionisation of Isocyanic Acid

Eland

Squibb

Sterling

et al. 2020

Sci Rep

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Double and triple ionization spectra of isocyanic acid have been measured using multielectron and ion coincidence techniques combined with synchrotron radiation and compared with high-level theoretical calculations. Vertical double ionization at an energy of 32.8±0.3 eV forms the 3 A'' ground state in which the HNCO 2+ ion is long-lived. The vertical triple ionization energy is determined as 65±1 eV. The core-valence double ionization spectra resemble the valence photoelectron spectrum in form, and their main features can be understood on the basis of a simple and rather widely applicable Coulomb model based on the characteristics of the molecular orbitals from which electrons are removed. Characteristics of the most important dissociation channels are examined and discussed.

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Section: Introductionmentioning

confidence: 99%

Double and Triple Ionisation of Isocyanic Acid

Eland

Squibb

Sterling

et al. 2020

Sci Rep

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“…HNCO is considered a highly toxic species and has been linked to adverse health effects [(Leslie et al, 2019;Roberts et al, 2011;Suarez-Bertoa and Astorga, 2016;SUVA, 2016;Wang et al, 2007) and references therein], and human exposure to concentrations larger than 1 ppbv is considered as potentially toxic (Roberts et al, 2011). Unfortunately, an air quality standard for HNCO does not exist in most of the countries, whereas an occupational exposure limit has been established by law in only a few countries, including Sweden (SWEA, 2011) and Switzerland (SUVA, 2016).…”

Section: Introductionmentioning

confidence: 99%

“…HNCO emission into the atmosphere is driven primarily by combustion processes based on both natural and anthropogenic activities [(Leslie et al, 2019) and references therein], where the pyrolysis of nitrogen-containing biomass materials during the events of wildfires and agricultural fires leads to the emission of HNCO into the atmosphere. The presence of HNCO in the cigarette smoke has been established via the pyrolysis of urea (cigarette additive), oxidation of nicotine, and oxidation of formamide (Hems et al, 2019;Roberts et al, 2011).…”

Section: Introductionmentioning

confidence: 99%

“…Even the combustion of almost all sorts of common household materials (e.g., fiber glass, rubber, foam, etc.) leads to HNCO emissions along other isocyanates [(Leslie et al, 2019) and references therein]. HNCO emissions from traffic are originating mainly from usage of recent catalytic converters in the exhaust systems of gasoline and diesel based vehicles.…”

Section: Introductionmentioning

confidence: 99%

“…These converters are implemented to control the emission of primary pollutants such as hydrocarbons, carbon monoxide, particulate matter, and nitrogen oxides. However, these implementations have promoted the formation of HNCO via surface-bound chain reactions at different stages of the flue gas exhaust, and additionally due to a HNCO slippage in the most commonly used urea-based SCR (Selective Catalytic Reduction) convertion system [e.g., (Brady et al, 2014;Heeb et al, 2011;Leslie et al, 2019;Suarez-Bertoa and Astorga, 2016)]. The usages of converters in modern vehicles potentially give rise to the emission of HNCO especially in urban regions with a growing density of vehicles.…”

Section: Introductionmentioning

confidence: 99%

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Chemical loss processes of isocyanic acid, HNCO, in the atmosphere

Rosanka

Nguyen

et al. 2020

Preprint

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Abstract. The impact of chemical loss processes of isocyanic acid was studied by a combined theoretical and modeling study. The potential energy surfaces of the reactions of HNCO with OH and NO3 radicals, Cl atoms, and ozone, were studied using high-level CCSD(T)/CBS(DTQ)//M06-2X/aug-cc-pVTZ quantum chemical methodologies, followed by TST theoretical kinetic predictions of the rate coefficients at temperatures of 200–3000 K. It was found that the reactions are all slow in atmospheric conditions, with k(300 K) ≤ 7 × 10−16 cm3 molecule−1 s−1; the predictions are in good agreement with earlier experimental work, where available. The reverse reactions of NCO radicals, of importance mostly in combustion, were also examined briefly. The global model confirms that gas phase chemical loss of HNCO is a negligible process, contributing less than 1 %. Removal of HNCO by clouds and precipitation is a larger sink, contributing for about 10 % of the total loss, while globally dry deposition is the main sink, accounting for ~ 90 %. The global simulation also shows that due to its long chemical lifetime in the free troposphere, HNCO can be efficiently transported into the UTLS by deep convection events. Average daily concentrations of HNCO are found to rarely exceed levels considered potentially toxic, though locally instantaneous toxic levels are expected.the free troposphere, HNCO can be efficiently transported into the UTLS by deep convection events. Average daily concentrations of HNCO are found to rarely exceed levels considered potentially toxic, though locally instantaneous toxic levels are expected.

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Spatially Resolved Measurements of HNCO Hydrolysis over SCR Catalysts

Eck

Lott

Schweigert

et al. 2022

Chemie Ingenieur Technik

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In order to understand deposit formation during urea selective catalytic reduction (SCR) resulting from isocyanic acid (HNCO) formation, the present study investigates the potential of HNCO hydrolysis by spatially resolved gas phase concentration profiles along a single catalyst channel of commercial Cu-zeolite and V-based SCR catalysts. The spatially resolved profiles, obtained in a special hot gas test rig via capillary technique, provide information on reaction rates of HNCO hydrolysis, NH 3 adsorption and NO conversion, hereby revealing a better performance of the standard V-based catalyst regarding the HNCO hydrolysis, which is attributed to the TiO 2 support.

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Isocyanic acid (HNCO) and its fate in the atmosphere: a review

Abstract: Isocyanic acid (HNCO) has recently been identified in ambient air at potentially concerning concentrations for human health. Since its first atmospheric detection, significant progress has been made in understanding its sources and sinks.

Cited by 44 publications

References 107 publications

Double and Triple Ionisation of Isocyanic Acid

Double and Triple Ionisation of Isocyanic Acid

Chemical loss processes of isocyanic acid, HNCO, in the atmosphere

Spatially Resolved Measurements of HNCO Hydrolysis over SCR Catalysts

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