研究目的
To understand the effects of cyclic alkenes on the atmospheric environment in polluted urban areas through studying SOA formation from cyclohexene/NOx system with various SO2 concentrations under UV light.
研究成果
The study demonstrated that SOA formation from cyclohexene photooxidation is influenced by SO2 concentration, with a decrease in yield at low SO2 concentrations and an increase at higher concentrations due to acid-catalyzed reactions. The competitive reaction between SO2 and VOCs for OH radicals was identified as a significant factor affecting SOA yield. Organosulfates were identified in the SOA, providing new insights into the chemical composition of aerosols formed under these conditions. These findings contribute to a better understanding of SOA formation in polluted urban environments and highlight the importance of considering both acid-catalysis and competitive reactions in atmospheric models.
研究不足
The study was conducted under controlled laboratory conditions which may not fully replicate the complexity of atmospheric conditions. The experiments were performed at a specific temperature (307±2 K) and low humidity (RH < 10%), which may not represent all atmospheric scenarios. The focus was on cyclohexene as a model compound, and results may not be directly applicable to other VOCs.
1：Experimental Design and Method Selection:
The experiments were performed in a 400 L Teflon FEP film chamber under UV irradiation to simulate the spectrum of the UV band in solar irradiation. The chamber was cleaned by purging with purified dry air before each experiment. Cyclohexene and NOx were introduced into the chamber, and SO2 was added at various concentrations to study its effect on SOA formation.
2：Sample Selection and Data Sources:
Cyclohexene was used as the VOC, with initial concentrations around 500 ppb, and NOx was adjusted to maintain a VOCs/NOx ratio of about
3：SO2 concentrations varied from 0 to 105 ppb. List of Experimental Equipment and Materials:
The chamber was equipped with black light lamps for UV irradiation. Gas concentrations (O3, NOx, SO2) were measured using specific analyzers. Particle number concentrations and size distributions were measured with a scanning mobility particle sizer (SMPS). The chemical composition of SOA was analyzed using FTIR, IC, and ESI-HR-MS.
4：Experimental Procedures and Operational Workflow:
After introducing the reactants, the chamber was irradiated with UV light to initiate photooxidation. Gas and particle phase measurements were taken over time to monitor the reaction progress and SOA formation.
5：Data Analysis Methods:
SOA yield was calculated based on the mass concentration of produced organic aerosol and the mass concentration of reacted cyclohexene. The composition of SOA was analyzed using FTIR for functional groups, IC for inorganic sulfate, and ESI-HR-MS for organosulfates.
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