%0 Journal Article
%A Li, Xin
%A Rohrer, F.
%A Brauers, T.
%A Hofzumahaus, A.
%A Lu, K.
%A Shao, M.
%A Zhang, Y. H.
%A Wahner, A.
%T Modeling of HCHO and CHOCHO at a semi-rural site in southern China during the PRIDE-PRD2006 campaign
%J Atmospheric chemistry and physics / Discussions
%V 13
%N 12
%@ 1680-7375
%C Katlenburg-Lindau
%I EGU
%M FZJ-2013-06524
%P 33013 - 33054
%D 2013
%X HCHO and CHOCHO are important trace gases in the atmosphere, serving as tracers of VOCs oxidations. In the past decade, high concentrations of HCHO and CHOCHO have been observed for the Pearl River Delta (PRD) region in southern China. In this study, we performed box model simulations of HCHO and CHOCHO at a semi-rural site in PRD, focusing on understanding their sources and sinks and factors influencing the CHOCHO to HCHO ratio (RGF). The model was constrained by the simultaneous measurements of trace gases and radicals. Isoprene oxidation by OH radicals is the major pathway forming HCHO, followed by degradations of alkenes, aromatics, and alkanes. The production of CHOCHO is dominated by isoprene and aromatic degradation; contributions from other NMHCs are of minor importance. The modeled RGF shows a complex dependence on the VOCs composition, OH and NOx levels, and atmospheric physical processes, which suggest the necessity of careful treatment of RGF as an indicator of anthropogenic or biogenic emissions. Compared to the measurement results, the model predicts significant higher HCHO and CHOCHO concentrations. Sensitivity studies suggest that this discrepancy is to a large extent (>70%) due to the missing consideration of fresh emissions, vertical transport of precursor VOCs, and uptake of HCHO and CHOCHO by aerosols in the model. Insufficient treatments of dry deposition of HCHO and CHOCHO and of vertical dilution of all species in the model account for the rest 30% discrepancy. Our study indicates that, in addition to chemical mechanisms, atmospheric physical processes (e.g., transport, dilution, deposition) have to be well considered for a box model predicting HCHO and CHOCHO concentrations.
%F PUB:(DE-HGF)16
%9 Journal Article
%R 10.5194/acpd-13-33013-2013
%U https://juser.fz-juelich.de/record/141340