Observations of Isocyanate, Amide, Nitrate, and Nitro Compounds from an Anthropogenic Biomass Burning Event Using a TOF‐CIMS
Smoke contains many substances that are harmful to human health, and local biomass burning events may increase the concentrations of toxic chemicals above healthy exposure limits. In this work, researchers used a CI-TOFMS with iodide reagent ion to measure ambient concentrations of smoke compounds during the bonfire night holiday in the UK.
The instrument was operated with a resolution of around 3.800 m/dm, which, combined with a Kendrick mass defect analysis, was sufficient to identify the chemical formulas of several hundred compounds. In particular, the authors explored measurements of hydrogen cyanide (HCN), isocyanic acid (HNCO), methyl isocyanate, formamide, methyl formamide, and dimethylformamide. In addition to these species, a number of other nitrates and nitrated species were detected, some of which had never been previously reported in the literature, including nitroformic acid, nitroperoxy methane, and trinitrocyclohexane. Background concentrations of these species in ambient air were often only a few parts per trillion, and concentrations in the smoke plume ranged from 15 to 4300 ppt, demonstrating the need for a sensitive instrument with a wide dynamic range.
The real-time measurement from the instrument allowed the researchers to distinguish between several different burning phases, and determine their relative emission factors, and observe that loss processes for amide species are fast. The authors conclude that local biomass burning events produce significant amounts of toxic compounds such as HCN and HNCO, and measurement of these species should be included in pollution assessments.