Oxidative Flow Reactor (OFR) experiments both in the presence and absence of NOx were conducted to investigate the oxidation of n-decane, which is commonly found in vehicular and industrial emissions. The self-developed NO injection system was firstly assembled onto Aerodyne OFR to achieve independent control of NOx and HOx. The distribution characteristics of the photooxidation products covering a full volatility range including Secondary Organic Aerosol (SOA) were investigated using Gas Chromatography Mass Spectrometer (GCMS), Proton Transfer Reactor Mass Spectrometer (PTR-MS), Chemical Ionization Mass Spectrometer (CIMS) coupled with Filter Inlet of Gas and AEROsols (FIGAERO), Aerodyne Long time-of-flight Aerosol Mass Spectrometer (LTof-AMS) and Quantum Cascade Tunable Infrared Laser Differential Absorption Spectrometer (QC-TILDAS) deployed downstream of OFR. The SOA yields were low under low NOx conditions (ranging from 0.3%-4%), first exhibited an increase, followed by a decrease as the level of OH exposure and negligible under high-NOx conditions. The trend reflects functionalization followed by fragmentation in high OH exposure, which is corroborated by the trend of CO concentrations, the O/C ratio, and thorough chemical characterization covered by the instrument suite. Lower SOA yields under high NOx condition can be attributed to the higher volatility of organic nitrates. A series of organic nitrates including decyl nitrates (C10H21ONO2), hydroxy decyl nitrates (C10H20(OH)(ONO2)) and more oxidized C10 nitrates were identified to remain in the gas phase rather than condense to form particles under the conditions in the OFR by FIGAERO-CIMS. Formation of these and analogous nitrates can also titrate NOx, and modifies further oxidation chemistry. We attempt to track the fate of carbon from the n-decane precursor through complex VOC oxidation paths to assess possible impacts on atmospheric chemistry, such as O3 production, which NOx might modulate. Our study suggests that n-decane oxidation is sensitive to NOx in the atmosphere with significant impacts including on SOA yields. Emissions controls on n-decane and other alkanes are presently highly limited while policies seek to lower NOx, we briefly examine the implications of our findings in light of this.

n-Decane oxidation; Oxidative Flow Reactor; Secondary organic aerosol; Organic nitrate; Carbon closure;