## 5 Contribution to SOA Formation
Additionally, although the reaction of long-chain alkanes with NO\({}_{3}\): is relatively slow, it is still signifi  
Figure 4: The SOA yield of certain components within IVOCs based on multi-laboratory studies. The white dots in the figure indicate individual values, while the columns illustrate a range of values. Purple indicates a yield of 0–10%, pink indicates a yield of 10–50%, orange indicates a yield of 50–100%, and yellow represents the yield exceeds 100%. cant due to the higher concentration of NO3: in the nighttime atmosphere. The products generated from the reaction of long-chain alkanes with NO3 radicals are mainly nitrate compounds, which have lower volatility and can significantly enhance SOA formation. PAHs primarily generate epoxides, nitro compounds, and chlorinated products through reactions with OH:, NO3', and CI atoms [92; 93; 94; 95; 96; 97; 98]. For example, acenapthrene reacts with OH: to form acenapthrenyl radicals, which can further react with O2 to generate peroxy radicals, ultimately forming low-volatility products that promote SOA formation. The reaction of acenapthrene with NO3: generates NO3-acenapthrene adducts, which can decompose to form 2,3-epoxyacenapthrene and 4,5-epoxyacenapthrene. The reaction of acenapthrene with CI atoms produces chlorinated products, such as 2-chloroanthracen-1-one and 1-chloropyren-2-one. Sesquiterpenes like \(\beta\)-caryophyllene mainly generate cyclic and ring-opening products through reactions with O3 and NO3, such as \(\beta\)-caryophyllone aldehyde, \(\beta\)-norcaryophyllone aldehyde, \(\beta\)-caryophyllonic acid, and \(\beta\)-nocaryophyllonic acid [99]. These products further react in the atmosphere to form low-volatility substances, promoting SOA formation. Additionally, the products generated from the reaction of \(\beta\)-caryophyllene with NO3 include nitro compounds and epoxides, such as 1-nitroanthracene and 9-nitroanthracene. These products, with their high stability and low volatility in the atmosphere, significantly contribute to SOA formation. The uncertainty in regard to model usage mainly stems from the insufficient accuracy of the emission factors, the inadequate temporal and spatial resolution of emission inventories, imperfect secondary oxidation reaction mechanisms, and inaccuracies in key kinetic parameters. Traditional air quality models have long underestimated SOA concentrations due to the neglect of IVOC emissions and oxidation mechanisms. By integrating IVOC emission inventories, optimizing kinetic parameters (such as the 2D-VBS), and incorporating aging mechanisms, the accuracy of SOA simulation results can be significantly improved. For example, [PERSON] et al. optimized smog chamber experimental parameters using a 2D-VBS box model and applied the scheme to a regional multiscale air quality model (CMAQ). They found that the introduction of aerosol aging and IVOC oxidation mechanisms increased OA  
Figure 5: Oxidation mechanisms of common IVOCs species. and SOA concentrations in eastern China by approximately 40% and 10 times, respectively, greatly enhancing model performance [12]. [PERSON] et al., when simulating pollution in the Beijing-Tianjin-Hebei region during the winter of 2014, significantly improved the SOA simulation results after incorporating the IVOC emission inventory, with IVOCs contributing 40.1% to SOAs [100]. [PERSON] et al. further corroborated this conclusion, with their model showing a 161% increase in SOA simulation concentrations in the Pearl River Delta region after introducing the IVOC emission inventory [31]. The optimization of kinetic parameters is a key aspect of model improvement. The 2D-VBS model, through its dual-dimensional (oxidation state and volatility) parameterization scheme, more accurately characterizes the gas-particle partitioning of IVOC oxidation products. In forested areas, the model achieved closure between simulated and measured SOA values after incorporating IVOC emissions and oxidation pathways [101], directly verifying the dominant role of IVOCs in natural-source SOA formation.