Open AccessStudy of different Carbon Bond 6 (CB6) mechanisms by using a concentration sensitivity analysis
Author(s) -
Le Cao,
Simeng Li,
Luhang Sun
Publication year - 2021
Publication title -
atmospheric chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.622
H-Index - 206
eISSN - 1680-7324
pISSN - 1680-7316
DOI - 10.5194/acp-21-12687-2021
Subject(s) - nox , formaldehyde , ozone , isoprene , chemistry , photochemistry , atmospheric sciences , organic chemistry , physics , copolymer , combustion , polymer
. Since the year 2010, different versions of the Carbon Bond 6 (CB6) mechanism have been developed to accurately estimate the contribution to air pollution by the chemistry. In order to better understand the differences in simulation results brought about by the modifications between differentversions of the CB6 mechanism, in the present study, we investigated the behavior of three different CB6 mechanisms (CB6r1, CB6r2 and CB6r3) insimulating ozone (O3), nitrogen oxides (NOx) and formaldehyde (HCHO) under two different emission conditions by applying a concentration sensitivity analysis in a box model. The results show that when the surface emission is weak, the O3 levelpredicted by CB6r1 is approximately 7 ppb higher than that predicted by CB6r2 and CB6r3, specifically due to the change in the sink of acyl peroxy radicals with high-order carbons (i.e., species CXO3) in the mechanism and the difference in the ozone dependence on the isoprene emission. In contrast, although CB6r1 estimates higher values of NOx and HCHO than the other two mechanisms at an earlystage of the simulation, the levels of NOx and HCHO estimated by these three CB6 mechanisms at the end of the 7 dsimulation are mostly similar, when the surface emission is weak. After the increase in the surface emission, the simulated profiles of O3, NOx and HCHO obtained by CB6r2 and CB6r3 were found to be nearly the same during the simulation period, but CB6r1 tends to estimate substantially higher values than CB6r2 and CB6r3. The deviation between the O3 levels provided by CB6r1 and the other two CB6mechanisms (i.e., CB6r2 and CB6r3) was found to be enlarged compared with the weak-emission scenario because of the weaker dependence of ozone on the emission of isoprene in CB6r1 than those in CB6r2 and CB6r3 in this scenario. Moreover, HCHO predicted by CB6r1 was found to be larger than those predicted by CB6r2 and CB6r3, which is caused by an enhanced dependence of HCHO on the emission of isoprene in CB6r1. RegardingNOx, it was found that CB6r1 gives a higher value than the other two mechanisms, which is caused by the relatively strongerconnection between the NOx prediction and the release of NO and NO2 in CB6r1 due to the change in the product of the reaction between isoprene and NO3 in CB6r1. Consequently, more emitted NOx is involved in the reaction system denotedby CB6r1, which enables a following NOx formation and thus a higher NOx prediction of CB6r1.