NO3 chemistry of wildfire emissions: a kinetic study of the gas-phase reactions of furans with the NO3 radical

Furans are emitted to the atmosphere during biomass burning from the pyrolysis of cellulose. They are one of the major contributing volatile organic compound (VOC) classes to OH and NO3 reactivity in biomass burning plumes. The major removal process of furans from the atmosphere at night is reaction with the nitrate radical, NO3. Here, we report a series of relative rate experiments in the 7300 L indoor simulation chamber at Institut de Combustion Aerothermique Reactivite et Environnement, Centre national de la recherche scientifique (ICARE-CNRS), Orleans, using a number of different reference compounds to determine NO3 reaction rate coefficients for four furans, two furanones, and pyrrole. In the case of the two furanones, this is the first time that NO3 rate coefficients have been reported. The recommended values (cm3 molec.(-1) s(-1)) are as follows: furan, (1.49 +/- 0.23) x 10(-12); 2-methylfuran, (2.26 +/- 0.52) x 10(-1)1; 2,5-dimethylfuran, (1.02 +/- 0.31) x 10(-10); furfural (furan-2-aldehyde), (9.07 +/- 2.3) x 10(-14); alpha-angelicalactone (5-methyl-2(3H)-furanone), (3.01 +/- 0.45) x 10(-12); gamma-crotonolactone (2(5H)-furanone), <1.4 x 10(-16); and pyrrole, (6.94 +/- 1.9) x 10(-11). The furfural + NO3 reaction rate coefficient is found to be an order of magnitude smaller than previously reported. These experiments show that for furan, alkyl-substituted furans, alpha-angelicalactone, and pyrrole, reaction with NO3 will be the dominant removal process at night and may also contribute during the day. For gamma-crotonolactone, reaction with NO3 is not an important atmospheric sink.

Automated summary

Furans are important volatile organic compounds emitted during biomass burning. This study found that the reaction of furans with the nitrate radical NO3 is the main removal process for furans in the atmosphere, except for gamma-crotonolactone.