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

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.