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

Abstract

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.

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

“…19 This result is consistent with measurements made during a nationwide bonre event in the UK where HNCO/CO ratios were observed to be 3 times higher during a period when emissions were thought to be dominated by aming combustion compared to smouldering. 58 In addition, this Guy Fawkes Night study found that plumes associated with bonres had maximum mixing ratios of 1.64 ppbv HNCO, a two-order of magnitude enhancement of the mean non-bonre mixing ratio of 0.012 ppbv. 58 Different parameters such as protein content and temperature determine how much HNCO is released during biomass burning.…”

“…60 In the Fort Collins and Manchester data sets, there is an early morning minimum with increasing concentrations throughout the day to a late aernoon maximum. 26,58 One hypothesis for the late aernoon peak observed in some datasets is the production of HNCO through secondary photochemical sources. 26 Support for secondary production comes from two lines of evidence.…”

OH chemistry of non-methane organic gases (NMOGs) emitted from laboratory and ambient biomass burning smoke: evaluating the influence of furans and oxygenated aromatics on ozone and secondary NMOG formation

“…The I-CIMS is sensitive to acids and multifunctional oxygenates (Lee et al, 2014), which are likely to form as secondary NMOGs in biomass burning plumes. I-CIMS has been used to evaluate primary NMOG emissions (e.g., Priestley et al, 2018;Reyes-Villegas et al, 2018;Tomaz et al, 2018), biomass burning emissions aged by nocturnal processes (Ahern et al, 2018;Reyes-Villegas et al, 2018), and primary particle-phase components (Gaston et al, 2016). I-CIMS spectra of the NMOGs resulting from the OH oxidation of biomass burning smoke have yet to be reported.…”

Production of N<sub>2</sub>O<sub>5</sub> and ClNO<sub>2</sub> in summer in urban Beijing, China

“…The UoM-CIMS setup has been described elsewhere (Priestley et al, 2018); a Filter Inlet for Gases and AEROsols (FI-GAERO; Lopez-Hilfiker et al, 2014) was additionally used in this study. The gas-phase inlet of UoM-CIMS consisted of 5 m 1/4 ID PFA tubing connected to a fast inlet pump with a total flow rate of 13 SLM from which the ToF-CIMS sub-sampled 2 SLM.…”