研究目的
Investigating the impact of molecular structure on secondary organic aerosol formation from aromatic hydrocarbon photooxidation under low NOx conditions.
研究成果
The study demonstrates that the molecular structure of aromatic hydrocarbons significantly impacts SOA formation under low NOx conditions. The ortho position promotes SOA formation, while the para position suppresses it. Aromatic oxidation increases with alkyl substitute chain length and branching structure. The carbon dilution theory was extended to serve as a standard method for determining the extent of oxidation of alkyl substituted aromatic hydrocarbons.
研究不足
The study was conducted under controlled laboratory conditions which may not fully replicate atmospheric conditions. The focus was on low NOx conditions, and the findings may not be applicable under high NOx conditions.
1：Experimental Design and Method Selection:
The study utilized the UC Riverside/CE-CERT indoor dual 90 m3 environmental chambers for photooxidation experiments under low NOx conditions. Experiments were conducted at dry conditions (RH <
2：1 %), in the absence of inorganic seed aerosol and with temperature controlled to 27 ± 1 ?C. Sample Selection and Data Sources:
Twelve different eight to nine carbon aromatic hydrocarbons were studied.
3：List of Experimental Equipment and Materials:
A known volume of high purity liquid hydrocarbon precursors was injected through a heated glass injection manifold system and flushed into the chamber with pure N
4：NO was introduced by flushing pure N2 through a calibrated glass bulb filled to a predetermined partial pressure of pure NO. Experimental Procedures and Operational Workflow:
All hydrocarbons and NO are injected and well mixed before lights are turned on to start the experiment.
5：Data Analysis Methods:
Particle size distribution was monitored by dual custom built Scanning Mobility Particle Sizers (SMPS). Particle effective density was measured with an Aerosol Particle Mass Analyzer (APM-SMPS) system. Particle volatility was measured by a Dekati? Thermodenuder Volatility Tandem Differential Mobility Analyzer (VTDMA). Particle-phase chemical composition evolution was measured by a High Resolution Time of Flight Aerosol Mass Spectrometer (HR-ToF-AMS).
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