Modelling the absorption spectra of polycyclic aromatic hydrocarbons over Seoul, South Korea
Pinto da Silva, Luís | Dias, Tiago B. | Esteves da Silva, Joaquim C.G.
The effects of light-absorbing atmospheric particles on climate forcing have been integrated into climate models, but the absence of brown carbon (BrC) in these models has led to differences between model predictions and measured data. Herein, we have used density functional theory (DFT) to generate models for the atmospheric absorption of polycyclic aromatic hydrocarbons (PAHs), major contributors to BrC light absorption, found over Seoul (South Korea), considering their seasonal and yearly variation. Winter was found to be the most problematic season, with significant absorption from the PAHs, while the absorption was more moderate in the autumn and in the spring. In the summer, the absorption is relatively quite weak. This is in line with the higher concentration of PAHs during winter, followed by autumn and spring, while being lower during summer. Moreover, these models showed that PAHs absorb strongly in the UVA and UVB regions of the UV spectrum, followed by moderate absorption in the UVC region and weak absorption in the visible region. Nevertheless, only absorption at the UVA and the visible region should be relevant for climate forcing. Finally, fluoranthene and benzo[a]anthracene are the most relevant contributors for UVB absorption, while benzo[a]pyrene, benzo[g,h,i]perylene, indeno[1,2,3-cd]pyrene and benzo[k]fluoranthene are the main responsible for absorption in the visible region. Thus, our modelling approach allowed us to identify which should be the most relevant PAHs for climate forcing on this region of the globe.Show more [+] Less [-]