## 5 Contribution to SOA Formation
The SOA yields generated from the oxidation of C\({}_{12}\)-C\({}_{17}\) long-chain alkanes by OH radicals range from 20 to 88% [83; 84; 85; 86; 87; 88; 89]. In contrast, the oxidation of n-dodecane initiated by chlorine atoms exhibits a super-stoichiometric characteristic, reaching a yield of 110-165% [90]. Dibenzothiophene, as a typical aromatic IVOC, maintains stable SOA formation efficiency at the level of 32% [91]. Systematic studies by the [PERSON] team have shown that high NOx conditions can generally increase the SOA yields of different structural C\({}_{12}\) alkanes [84]. This phenomenon is particularly prominent in the chlorine atom oxidation pathway of n-dodecyl to n-tetradacyl cyclohexanes, where the SOA yield reaches 90.14% in high NOx conditions, nearly double that of the 47.39% in low NOx conditions. This confirms the SOA formation advantage of this reaction pathway in urban atmospheric pollution scenarios [13]. Additionally, the introduction of dioctyl adipate seed can enhance the gas-particle partitioning efficiency, increasing the SOA yield by 5-15% [85; 87]. Compared to low-humidity environments, elevated relative humidity \begin{table}
\begin{tabular}{c c c} \hline
**IVOC Precursors** & **SOA Tracers** & **Indicator for Sources** \\ \hline \multirow{4}{*}{Nap} & 4-nitrophthalic acid & \multirow{4}{*}{PAHs} \\  & 4-nitro-1-naphthol & \\  & 2,4-dinitro-1-naphthol & \\  & Phthalic acid & \\ \hline \(\upbeta\)-caryophyllene & \(\upbeta\)-caryophyllinic acid & Sesquiterpenes \\ \hline \end{tabular}
\end{table} 
Table 2: Currently identified SOA tracers capable of indicating species of IVOCs. (RH \(>\) 40%) can reduce the SOA yield by 11-55%, by increasing the aerosol liquid water content and altering the gas-particle partitioning coefficients [85; 90]. The SOA derived from dodecane shows weak sensitivity to temperature, which is attributed to the extremely low volatility of its oxidation products, making it difficult for conventional temperature fluctuations to significantly change the condensation phase transition threshold of the products [86]. The process of IVOC oxidation leading to SOA formation involves complex chemical reaction mechanisms. Currently, research in this field remains relatively limited, with mechanism exploration primarily conducted through laboratory simulations. The current research on SOA formation pathways mainly focuses on the chain oxidation processes of long-chain alkanes, the cyclic structure transformation mechanisms of PAHs, and the formation pathways of oxidation products from sesquiterpenenes (represented by \(\beta\)-caryophyllene) (Figure 5). Long-chain alkanes generate SOAs in the atmosphere through reactions with different oxidants, with the oxidation mechanisms varying depending on the type of oxidant [7]. The reactions of long-chain alkanes with OH- typically occur during the daytime, beginning with the abstraction of hydrogen atoms from alkane molecules by OH- to form alkyl RO\({}_{2}\). In low NOx conditions, RO\({}_{2}\) mainly reacts with HO\({}_{2}\) to form peroxides (ROOH). ROOH can generate various products through reactions with OH- or photolysis, including carbonyl compounds and dihydroxy peroxides, which may further participate in the formation of atmospheric particulate matter. In high NOx conditions, RO\({}_{2}\) mainly reacts with NO to form alkyl nitrates (AN) and alkoxy radicals (RO). RO can further decompose or react with O\({}_{2}\) to form carbonyl compounds, which tend to remain in the gas phase, thereby reducing particle formation. The reaction of long-chain alkanes with Cl atoms mainly occurs during the day in coastal and marine regions. Cl atoms initiate the oxidation process by abstracting hydrogen atoms, generating RO\({}_{2}\), which reacts with RO\({}_{2}\) to form RO. RO mainly reacts with O\({}_{2}\) to form carbonyl compounds or decomposes to produce small molecules with higher volatility, contributing relatively less to SOAs.