A series of experiments was designed and conducted in the Manchester Aerosol Chamber (MAC) to study the photo-oxidation of single and mixed biogenic (isoprene and α-pinene) and anthropogenic (o-cresol) precursors in the presence of NO_x and ammonium sulfate seed particles. Several online techniques (HR-ToF-AMS, semi-continuous GC-MS, NO_x and O₃ analyser) were coupled to the MAC to monitor the gas and particle mass concentrations. Secondary organic aerosol (SOA) particles were collected onto a quartz-fibre filter at the end of each experiment and analysed using liquid chromatography–ultrahigh-resolution mass spectrometry (LC-Orbitrap MS). The SOA particle chemical composition in single and mixed precursor systems was investigated using non-targeted accurate mass analysis of measurements in both negative and positive ionization modes, significantly reducing data complexity and analysis time, thereby providing a more complete assessment of the chemical composition. This non-targeted analysis is not widely used in environmental science and has never been previously used in atmospheric simulation chamber studies. Products from α-pinene were found to dominate the binary mixed α-pinene–isoprene system in terms of signal contributed and the number of particle components detected. Isoprene photo-oxidation was found to generate negligible SOA particle mass under the investigated experimental conditions, and isoprene-derived products made a negligible contribution to particle composition in the α-pinene–isoprene system. No compounds uniquely found in this system sufficiently contributed to be reliably considered a tracer compound for the mixture. Methyl-nitrocatechol isomers (C₇H₇NO₄) and methyl-nitrophenol (C₇H₇NO₃) from o-cresol oxidation made dominant contributions to the SOA particle composition in both the o-cresol–isoprene and o-cresol–α-pinene binary systems in negative ionization mode. In contrast, interactions in the oxidation mechanisms led to the formation of compounds uniquely found in the mixed o-cresol-containing binary systems in positive ionization mode. C₉H₁₁NO and C₈H₈O₁₀ made large signal contributions in the o-cresol–isoprene binary system. The SOA molecular composition in the o-cresol–α-pinene system in positive ionization mode is mainly driven by the high-molecular-weight compounds (e.g. C₂₀H₃₁NO₄ and C₂₀H₃₀O₃) uniquely found in the mixture. The SOA particle chemical composition formed in the ternary system is more complex. The molecular composition and signal abundance are both markedly similar to those in the single α-pinene system in positive ionization mode, with major contributions from o-cresol products in negative ionization mode.

中文翻译：

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由人为和生物前体混合物形成的次级有机气溶胶颗粒的化学成分

在曼彻斯特气溶胶室 (MAC) 中设计并进行了一系列实验，以研究在NO _x和铵存在下单一和混合的生物（异戊二烯和α-蒎烯）和人为（邻甲酚）前体的光氧化硫酸盐种子颗粒。几种在线技术（HR-ToF-AMS、半连续 GC-MS、NO _x和 O ₃分析仪）耦合到 MAC 以监测气体和颗粒质量浓度。在每个实验结束时，将二次有机气溶胶 (SOA) 颗粒收集到石英纤维过滤器上，并使用液相色谱-超高分辨率质谱 (LC-Orbitrap MS) 进行分析。使用非靶向精确质量分析对负电离和正电离模式下的测量结果进行了研究，研究了单一和混合前体系统中的 SOA 颗粒化学成分，显着降低了数据复杂性和分析时间，从而提供了更完整的化学成分评估。这种非目标分析并未广泛用于环境科学，并且以前从未用于大气模拟室研究。来自α的产品发现 -蒎烯在信号贡献和检测到的粒子成分数量方面主导二元混合α -蒎烯 - 异戊二烯系统。在所研究的实验条件下，发现异戊二烯光氧化产生可忽略不计的 SOA 颗粒质量，并且异戊二烯衍生产品对α-蒎烯-异戊二烯系统中的颗粒组成的贡献可忽略不计。在该系统中唯一发现的任何化合物都不足以被可靠地视为混合物的示踪化合物。来自邻的甲基-硝基儿茶酚异构体 (C ₇ H ₇ NO ₄ ) 和甲基-硝基苯酚 (C ₇ H ₇ NO ₃ )在负电离模式下，在邻甲酚-异戊二烯和邻甲酚-α-蒎烯二元体系中，-甲酚氧化对 SOA 颗粒组成有主要贡献。相反，氧化机制中的相互作用导致在正电离模式下在混合含邻甲酚的二元系统中形成独特的化合物。C ₉ H ₁₁ NO 和 C ₈ H ₈ O ₁₀在邻甲酚-异戊二烯二元体系中产生了很大的信号贡献。邻甲酚-α中的 SOA 分子组成正离子模式下的-蒎烯系统主要由混合物中独特的高分子量化合物（如C ₂₀ H ₃₁ NO ₄和C ₂₀ H ₃₀ O _{3 ）驱动。}三元体系中形成的SOA颗粒化学成分较为复杂。分子组成和信号丰度都与正电离模式下的单一α-蒎烯系统中的分子组成和信号丰度显着相似，负电离模式下邻甲酚产物的主要贡献。