Comparison of negative-ion proton-transfer with iodide ion chemical ionization mass spectrometry for quantification of isocyanic acid in ambient air

Woodward-Massey, Robert; Taha, Youssef M.; Moussa, Samar G.; Osthoff, Hans D.

doi:10.1016/j.atmosenv.2014.09.014

Cited by 34 publications

(37 citation statements)

References 47 publications

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“…4. This value compares to similar weak acids like HONO (−40 kJ mol −1 ) and HCN (−42 kJ mol −1 ), but differs from the value of formic acid (−47 kJ mol −1 ) which was the value assumed for HNCO in the Young et al, and the Barth et al, modelling studies (Barth et al, 2013;Sander, 2015;Young et al, 2012).…”

Section: Temperature Dependencementioning

confidence: 88%

“…HNCO has also been detected simultaneously in the gas phase and in cloud water in La Jolla, California (Zhao et al, 2014). From these studies, typical urban concentrations range from below detection limits to approximately 100 pptv, whereas concentrations as high as 1.2 ppbv, enough to be of health concern, have been measured in air masses impacted by biomass burning in Boulder, Colorado (Roberts et al, 2011Woodward-Massey et al, 2014).…”

Section: Introductionmentioning

confidence: 92%

“…Note however that our HNCO lifetime estimates do not consider dry deposition and therefore represent a higher limit, particularly since Young et al, found that dry deposition can be significant for HNCO (Young et al, 2012). Specifically, the lifetime of HNCO in the atmosphere will depend on its partitioning to the aqueous phase K eff H , the temperature T , the pH and liquid water content (LWC) of the aerosol and/or droplet and finally the hydrolysis of HNCO k hyd once in solution.…”

Section: Atmospheric Implicationsmentioning

confidence: 99%

“…Recently reported ambient measurements of HNCO in North America raise concerns of exposure particularly from biomass burning, diesel and gasoline exhaust and urban environments (Brady et al, 2014;Roberts et al, 2011Roberts et al, , 2014Wentzell et al, 2013;Woodward-Massey et al, 2014;Zhao et al, 2014 Figure 7. k hyd as function of temperature and pH generated from Eq.…”

Section: Atmospheric Implicationsmentioning

confidence: 99%

“…Furthermore, the enthalpy of dissolution for HNCO is currently unknown. In lieu of measurements, modelling studies on HNCO have used formic acid's enthalpy of dissolution to model the temperature dependence of HNCO's Henry's Law coefficient (Barth et al, 2013;Young et al, 2012). In our present study, we measure the effective Henry's Law coefficient of HNCO at a range of pH and temperatures to determine its enthalpy of dissolution for the first time.…”

Section: Introductionmentioning

confidence: 99%

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Solubility and reactivity of HNCO in water: insights into HNCO's fate in the atmosphere

et al. 2016

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Abstract.A growing number of ambient measurements of isocyanic acid (HNCO) are being made, yet little is known about its fate in the atmosphere. To better understand HNCO's loss processes and particularly its atmospheric partitioning behaviour, we measure its effective Henry's Law coefficient K eff H with a bubbler experiment using chemical ionization mass spectrometry as the gas phase analytical technique. By conducting experiments at different pH values and temperature, a Henry's Law coefficient K H of 26 ± 2 M atm −1 is obtained, with an enthalpy of dissolution of −34 ± 2 kJ mol −1 , which translates to a K eff H of 31 M atm −1 at 298 K and at pH 3. Our approach also allows for the determination of HNCO's acid dissociation constant, which we determine to be K a = 2.1 ± 0.2 × 10 −4 M at 298 K. Furthermore, by using ion chromatography to analyze aqueous solution composition, we revisit the hydrolysis kinetics of HNCO at different pH and temperature conditions. Three pH-dependent hydrolysis mechanisms are in play and we determine the Arrhenius expressions for each rate to be k 1 = (4.4 ± 0.2) × 10 7 exp(−6000 ± 240/T ) M s −1 , k 2 = (8.9 ± 0.9) × 10 6 exp(−6770 ± 450/T ) s −1 and k 3 = (7.2 ± 1.5) × 10 8 exp(−10 900 ± 1400/T ) s −1 , where k 1 is for HNCO + H + + H 2 O → NH + 4 + CO 2 , k 2 is for HNCO + H 2 O → NH 3 + CO 2 and k 3 is for NCO − + 2 H 2 O → NH 3 + HCO − 3 . HNCO's lifetime against hydrolysis is therefore estimated to be 10 days to 28 years at pH values, liquid water contents, and temperatures relevant to tropospheric clouds, years in oceans and months in human blood. In all, a better parameterized Henry's Law coefficient and hydrolysis rates of HNCO allow for more accurate predictions of its concentration in the atmosphere and consequently help define exposure of this toxic molecule.

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Section: Temperature Dependencementioning

confidence: 88%

Section: Introductionmentioning

confidence: 92%

Section: Atmospheric Implicationsmentioning

confidence: 99%

Section: Atmospheric Implicationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Solubility and reactivity of HNCO in water: insights into HNCO's fate in the atmosphere

et al. 2016

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Photochemical processing of diesel fuel emissions as a large secondary source of isocyanic acid (HNCO)

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Friedman

Fulgham

et al. 2016

Geophysical Research Letters

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Isocyanic acid (HNCO) is a well‐known air pollutant that affects human health. Biomass burning, smoking, and combustion engines are known HNCO sources, but recent studies suggest that secondary production in the atmosphere may also occur. We directly observed photochemical production of HNCO from the oxidative aging of diesel exhaust during the Diesel Exhaust Fuel and Control experiments at Colorado State University using acetate ionization time‐of‐flight mass spectrometry. Emission ratios of HNCO were enhanced, after 1.5 days of simulated atmospheric aging, from 50 to 230 mg HNCO/kg fuel at idle engine operating conditions. Engines operated at higher loads resulted in less primary and secondary HNCO formation, with emission ratios increasing from 20 to 40 mg HNCO/kg fuel under 50% load engine operating conditions. These results suggest that photochemical sources of HNCO could be more significant than primary sources in urban areas.

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Observations of Isocyanate, Amide, Nitrate, and Nitro Compounds From an Anthropogenic Biomass Burning Event Using a ToF‐CIMS

et al. 2018

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Anthropogenic biomass burning is poorly represented in models due to a lack of observational data but represents a significant source of short‐lived toxic gases. Guy Fawkes Night (bonfire night) is a regular UK‐wide event where open fires are lit and fireworks are set off on 5 November. Previous gas phase studies of bonfire night focus on persistent organic pollutants primarily using off‐line techniques. Here the first simultaneous online gas phase measurements of several classes of compounds including isocyanates, amides, nitrates, and nitro‐organics are made during bonfire night (2014) in Manchester, UK, using a time‐of‐flight chemical ionization mass spectrometer (ToF‐CIMS) using iodide reagent ions. A shallow boundary layer and low wind speeds favor pollutant buildup with typical HCN, HNCO, and CH3NCO concentrations of tens of parts per thousand increasing by a factor of 13 to potentially harmful levels >1 ppb. Normalized excess mixing ratios relative to CO for a range of isocyanates and amides are reported for the first time. Using a HNCO:CO ratio of 0.1%, we distinguish emissions from flaming and smoldering combustion and report more accurate normalized excess mixing ratios for the distinct burning phases. While bonfire night is a highly polluting event, NO2 concentrations measured at this location are higher at other times, highlighting the importance of traffic as an NO2 emission source at this location. A risk communication methodology is used to equate enhancements in hourly averaged black carbon and NO2 concentrations caused by bonfire night as an equivalent of 26.1 passively smoked cigarettes.

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Comparison of negative-ion proton-transfer with iodide ion chemical ionization mass spectrometry for quantification of isocyanic acid in ambient air

Abstract: 2014). Comparison of negative-ion proton-transfer with iodide ion chemical ionization mass spectrometry for quantification of isocyanic acid in ambient air. Atmospheric Environment, 98, 693-703.

Cited by 34 publications

References 47 publications

Solubility and reactivity of HNCO in water: insights into HNCO's fate in the atmosphere

Solubility and reactivity of HNCO in water: insights into HNCO's fate in the atmosphere

Photochemical processing of diesel fuel emissions as a large secondary source of isocyanic acid (HNCO)

Observations of Isocyanate, Amide, Nitrate, and Nitro Compounds From an Anthropogenic Biomass Burning Event Using a ToF‐CIMS

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