Modeling of HCHO and CHOCHO at a semi-rural site in southern China during the PRIDE-PRD2006 campaign
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چکیده
HCHO and CHOCHO are important trace gases in the atmosphere, serving as tracers of VOC 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 the 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. Compared to the measurement results, the model predicts significant higher HCHO and CHOCHO concentrations. Sensitivity studies suggest that fresh emissions of precursor VOCs, uptake of HCHO and CHOCHO by aerosols, fast vertical transport, and uncertainties in the treatment of dry deposition all have the potential to contribute significantly to this discrepancy. Our study indicates that, in addition to chemical considerations (i.e., VOC composition, OH and NOx levels), atmospheric physical processes (e.g., transport, dilution, deposition) make it difficult to use the CHOCHO to HCHO ratio as an indicator for the origin of air mass composition.
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Supplement of Modeling of HCHO and CHOCHO at a semi-rural site in southern China during the PRIDE-PRD2006 campaign
متن کامل
Interactive comment on “Modeling of HCHO and CHOCHO at a semi-rural site in southern China during the PRIDE-PRD2006 campaign” by X. Li et al
This manuscript describes their box modeling work constrained by the measurements acquired during PRIDE-PRD2006 campaign. They focused on the importance of source and sink mechanisms to reconcile the observed and modeled HCHO and CHOCHO concentration. The authors claim that fresh emission, vertical and horizontal transport, and aerosol uptake processes are the major reason in the overestimation...
متن کاملInteractive comment on “Modeling of HCHO and CHOCHO at a semi-rural site in southern China during the PRIDE-PRD2006 campaign” by X. Li et al
The major deficiency lies in the assumption of a box model with a well-mixed boundary layer height of about 1 km, and the model calculations being constrained to measurements of OH, NO, NO2, HONO, O3, CO, CH4, C3 – C12 NMHCs. The assumption of a well-mixed boundary layer for long-lived species is appropriate, but not for shortlived (shorter than a few hours) species such as OH, NO, NO2, isopren...
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تاریخ انتشار 2014