## 3 Results and Discussion
### Effect of Soil pH on Odor Activity Value (OAV) of Key Compounds in Tea Leaves  
The aroma of a compound is closely related to its OAV value. When the OAV value of a compound is \(>\)1, it indicates that the compound makes an actual contribution to the aroma, and the higher the OAV value, the greater the contribution is [14; 42]. Odor characteristics are analyzed and presented via compounds that contribute to the tea aroma in the aroma formation process [15; 43]. In-depth analyses of the OAV values and odor characteristics of compounds are important for revealing the effect of soil pH on the formation of tea aroma. The results of this study showed (Tables S4-S7) that the contents of key compounds in tea leaves grown in soils with different pH levels were 11.984 \(\mathrm{\SIUnitSymbolMicro g}\)/kg at a pH of 3.29, accounting for 52.18% of the total compound content; 17.935\(\mathrm{\SIUnitSymbolMicro g}\)/kg at a pH of 4.13, accounting for 57.95% of the total compound content; 28.228 \(\mathrm{\SIUnitSymbolMicro g}\)/kg at a pH of 4.74, accounting for 61.05% of the total compound content; and 34.410 \(\mathrm{\SIUnitSymbolMicro g}\)/kg at a pH of 5.32, accounting for 57.27% of the total compound content. Furthermore, when the soil pH was 3.29, 12 compounds had OAV values greater than 1, with a total OAV value of 1611.45, among which the top three contributing compounds were geranoid (65.66%), \(\alpha\)-ionone (10.60%) and \(\beta\)-ionone (10.27%),  
Figure 1: Effects of soil pH on volatile compounds in tea leaves. Note: P1—soil pH of 3.29; P2—soil pH of 4.13; P3—soil pH of 4.74; P4—soil pH of 5.32. (**A**) GC-MS map of volatile compounds in tea tree leaves; (**B**) Venn diagram analysis of volatile compounds in tea tree leaves; (**C**) Analysis of volatile compound contents in tea tree leaves. and their total contribution rate was 86.53% (Figure 2A, Table S4). When the soil pH was 4.13, 11 compounds had OAV values greater than 1, and the total OAV value was 2342.90, among which the top three contributing compounds were geraniol (70.80%), \(\beta\)-ionone (12.21%) and \(\alpha\)-ionone (9.70%), and their total contribution rate was 92.71% (Figure 2A, Table S5). When the soil pH was 4.74, 12 compounds had OAV values greater than 1, and the total OAV value was 3445.46, among which the top three contributing compounds were geraniol (74.97%), \(\beta\)-ionone (8.52%) and \(\alpha\)-ionone (7.72%), and their total contribution rate reached 91.21% (Figure 2A, Table S6). When the soil pH was 5.32, 12 compounds had OAV values greater than 1, and the total OAV value was 4563.82, among which the top three contributing compounds were geraniol (77.18%), \(\beta\)-ionone (9.03%) and \(\alpha\)-ionone (6.83%), and their total contribution rate reached 93.04% (Figure 2A, Table S7). It can be seen that with the decrease in soil pH (5.32 to 3.29), the total OAV value of the aroma compounds in the tea leaves showed a downward trend (4563.82 to 1611.45), and the aroma of the tea leaves decreased. Secondly, it was found that geraniol, \(\beta\)-ionone and \(\alpha\)-ionone were the major compounds contributing to the aroma of the tea leaves, showing that the total contribution rate of the three compounds to the aroma was more than 86.53%. Many scholars also found that geraniol, \(\beta\)-ionone and \(\alpha\)-ionone were the main components of the aroma characteristics of tea leaves, especially geraniol [44; 45]. [PERSON] et al. [46] found that the aroma of yellow tea was mainly formed by six compounds with OAV values greater  
Figure 2: Analysis of odor activity values of key compounds and their odor characteristics of tea leaves in soils with different pH. Note: P1: Soil pH 3.29; P2: Soil pH 4.13; P3: Soil pH 4.74; P4: Soil pH 5.32; (**A**) Analysis of OAV values of key compounds; (**B**) OAV value analysis of odor characteristics of key compounds. than 1, among which geraniol and \(\beta\)-ionone contributed the most. [PERSON] et al.