## 3 Results and Discussion
### Aroma Compounds
#### 3.3.1 Terpenes
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Compound** & **Threshold \({}^{\dagger}\)** & **Hiaodong Peninsula** & **Bohai Bay** & **Huazhuo Basin** & **Loess Plateau** & **Xinjlang** \\ \hline Ethy1 & 7500 [25] & 53,313.6\(\pm\) 12, 126,699.67 c & 70,487.82 \(\pm\) 24,192.58 bc & 88,681.25 \(\pm\) 27,710.30 ab & 120,6908.08 \(\pm\) 39,741.90 a & 116,549.20 \(\pm\) 30,546.87 a \\ Isobutyl acetate & 1600 [25] & 9,48 \(\pm\) 6.33 o & 18,86 \(\pm\) 13.76 a & 9,21 \(\pm\) 13.26 s & 7,24 \(\pm\) 5.50 b & 6,67 \(\pm\) 4.70 b \\ Isoamyl acetate & 30 [25] & 1648.58 \(\pm\) 1016.73 a & 200,30 \(\pm\) 1053.7 a & 832,94 \(\pm\) 399.79 b & 663.18 \(\pm\) 211.84 b & 841.42 \(\pm\) 344.28 b \\ Heylyl acetate & 1000 [27] & 71.17 \(\pm\) 74.33 a & 33.04 \(\pm\) 20.60 ab & 8,85 \(\pm\) 420.10 & 11.30 \(\pm\) 5.50 b & 9.26 \(\pm\) 4.20 b \\ Heylyl acetate & 40 \(\pm\) 0.44 a & 0.09 \(\pm\) 0.00 ab & 0.00 \(\pm\) 0.01 b & 0.00 \(\pm\) 0.00 b & 0.01 \(\pm\) 0.00 b \\ Phenethyl acetate & 250 [25] & 66.68 \(\pm\) 54.04 a & 580 \(\pm\) 50.19 s & 32,50 \(\pm\) 14.62 s & 236.1 \(\pm\) 3.02 b & 37.79 \(\pm\) 191.4 b \\ Acetic acid (mg/L) & 200,000 [25] & 37.31 \(\pm\) 93.85 o & 45.96 \(\pm\) 13.08 bc & 53.17 \(\pm\) 1205 & 61.16 \(\pm\) 17.52 b & 759.99 \(\pm\) 26.30 a \\ Isobutanoic acid & 20,000 [28] & 2001.63 \(\pm\) 794.67 abc & 3005.68 \(\pm\) 1203.91 ab & 3007.84 \(\pm\) 2048.22 a & 1572.45 \(\pm\) 651.55 c & 2102.83 \(\pm\) 560.75 bc \\ Hexanoic acid & 420 [29] & 1654.44 \(\pm\) 405.83 a & 1555.85 \(\pm\) 192.78 a & 1409.18 \(\pm\) 175.35 & 1647.46 \(\pm\) 397.2 a & 1391.26 \(\pm\) 37.36 a \\ Octanoic acid & 500 [29] & 2065.59 \(\pm\) 257.39 a & 1996.46 \(\pm\) 181.01 ab & 1799.26 \(\pm\) 62.86 & 1821.23 \(\pm\) 118.35 b & 1810.82 \(\pm\) 141.07 bc \\ Decanoic acid & 1000 [25] & 2526.69 \(\pm\) 174.88 a & 2460.94 \(\pm\) 98.39 a & 2483.42 \(\pm\) 27.35 b & 2457.84 \(\pm\) 401.3 b & 2385.82 \(\pm\) 467.3 b \\ Supreme & - & 2.36 \(\pm\) 32.22 a & 0.13 \(\pm\) 0.26 b & 0.35 \(\pm\) 0.61 b & 0.60 \(\pm\) 1.07 b & 0.40 \(\pm\) 11.3 b \\ Naphthalene & - & 0.20 \(\pm\) 0.29 b & 1.78 \(\pm\) 2.02 & 0.41 \(\pm\) 0.34 b & 0.44 \(\pm\) 0.19 b & 0.41 \(\pm\) 0.16 b \\ \(\dagger\) He-Acanol & 8000 [25] & 2696.95 \(\pm\) 1012.55 b & 2932.39 \(\pm\) 909.25 b & 436.36 \(\pm\) 154.34 a & 3712.82 \(\pm\) 4134.24 b & 2805.52 \(\pm\) 1068.65 b \\ \(\dagger\)(E)-Heisen-1 & 1000 [30] & 233.28 \(\pm\) 82.64 & 46.413 \(\pm\) 33.86 b & 62.05 \(\pm\) 315.52 b & 7021.21 \(\pm\) 259.55 & 541.88 \(\pm\) 37.32 bc \\ (E)-2-Heven-1-ol & 2,47 \(\pm\) 2.36 b & 136.36 \(\pm\) 4.69 a & 79.1 \(\pm\) 41.88 b & 14.18 \(\pm\) 5.57 a & 9.34 \(\pm\) 8.82 a \\ Nonanal & 15 [31] & 36.16 \(\pm\) 0.91 ab & 33.73 \(\pm\) 128.26 \(\pm\) 30.53 b & 2.86 \(\pm\) 0.52 b & 30.66 \(\pm\) 0.84 b \\ Ethyl lactate & 100,000 [27] & 79,455.87 \(\pm\) 50,234.26 b & 1440.107 \(\pm\) 112,656.14 b & 147,259.32 \(\pm\) 95,952.25 ab & 161,621.62 \(\pm\) 69,005.82 ab & 178,204.86 \(\pm\) 9,665.85 r \(\sharp\) \\ Ethyl 9-deconate & 100 [32] & 60.60 \(\pm\) 101.8 b & 108.33 \(\pm\) 57.16 a & 73.59 \(\pm\) 12.51 b & 71.48 \(\pm\) 103.1 b & 68.47 \(\pm\) 11.99 b \\ Ethyl & 3 [25] & 53.68 \(\pm\) 101.47 b & 60.06 \(\pm\) 5.18 b & 180.82 \(\pm\) 81.76 b & 205.26 \(\pm\) 1832.30 a & 299.00 \(\pm\) 10.97 i a \\ Ethyl 7-octonate & - & 14.41 \(\pm\) 0.61 c & 170.26 \(\pm\) 22.82 a & 149.46 \(\pm\) 6.68 b & 149.48 \(\pm\) 0.78 bc & 15.74 \(\pm\) 11.51 b \\ Ethyl 2-fluoro & - & 207.82 \(\pm\) 166.39 b & 164.16 \(\pm\) 55.48 b & 561.80 \(\pm\) 164.48 a & 663.56 \(\pm\) 463.01 a & 533.49 \(\pm\) 348.75 a \\ Ethyl succinate & 100,000 [33] & 4386.89 \(\pm\) 4118.95 b & 755.53 \(\pm\) 563.54 b & 919.83 \(\pm\) 73.646 b & 9219.74 \(\pm\) 641.19 b & 164.450 \(\pm\) 1264.05 a \\ Ethyl phenylacetate & 650 [34] & 4.86 \(\pm\) 43.33 & 3.53 \(\pm\) 13.82 a & 7.84 \(\pm\) 49.53 a & 7.42 \(\pm\) 5.02 a & 1.59 \(\pm\) 5.02 b \\ Ethyl butanoate & 20 [25] & 1258.88 \(\pm\) 272.63 b & 1696.41 \(\pm\) 319.91 b & 1458.42 \(\pm\) 319.48 b & 1999.73 \(\pm\) 5077.9 a & 1835.93 \(\pm\) 1002.26 ab \\ Ethyl hexanoate & 5 [25] & 788.79 \(\pm\) 213.88 a & 795.16 \(\pm\) 107.9 a & 702.95 \(\pm\) 127.01 & 861.12 \(\pm\) 217.67 & 756.18 \(\pm\) 282.59 a \\ Ethyl heptanoate & 2,04 \(\pm\) 0.97 a & 1.7  
\begin{table}
\begin{tabular}{c c c c c c c} \hline
**Compound** & **Threshold \({}^{\dagger}\)** & **Iiaodong Peninsula** & **Bohai Bay** & **Huaihuo Basin** & **Loose Plateau** & **Xinjiang** \\ \hline Butyrolactone & 100,000 [27] & 7867.33 \(\pm\) 2764.38 c & 7670.68 \(\pm\) 2714.28 c & 14,149.21 \(\pm\) 6066.98 ab & 8700.18 \(\pm\) 2291.87 bc & 15,995.18 \(\pm\) 7491.72 a \\
2-Paramtenhand & 15,000 [36] & 6,70 \(\pm\) 6.80 b & 321.11 \(\pm\) 197.2 ab & 132.67 \(\pm\) 1702.12 a & 65.29 \(\pm\) 62.38 a & 20.87 \(\pm\) 382.5 ab \\ Isobutband & 40,000 [25] & 65,080.99 \(\pm\) 1126.73 a & 57,566.81 \(\pm\) 1114.26 a & 9373.22 \(\pm\) 7667.667 c & 722.849 \(\pm\) 2349.52 a & 709,697.97 \(\pm\) 3074.16 a \\ Isopentand & 65,000 [27] & 155,154.36 \(\pm\) 2943.02 ab & 127,002.67 \(\pm\) 16,205.86 b & 186,864.22 \(\pm\) 4801.015 b & 172,232.42 \(\pm\) 4320.562 ab & 208,170.03 \(\pm\) 826,675 a \\
4-Methyl-1-pentanol & 50,000 [29] & 8.84 \(\pm\) 22.4 ab & 5.91 \(\pm\) 1.34 b & 10.09 \(\pm\) 2.40 a & 8.69 \(\pm\) 2.80 ab & 12.28 \(\pm\) 472.2 \\
3-Methyl-1-pentanol & 50,000 [26] & 6.99 \(\pm\) 347.5 ab & 39.98 \(\pm\) 24.3 b & 104.69 \(\pm\) 39.71 & 86.93 \(\pm\) 70.03 ab & 12.98 \(\pm\) 73.99 a \\
1-Octanol & 20 [37] & 9.95 \(\pm\) 311.0 & 18.28 \(\pm\) 15.21 a & 14,17.63 \(\pm\) 6.84 a & 10.91 \(\pm\) 2.75 ab & 12.64 \(\pm\) 35.3 ab \\
1-Heppanol & 200 [35] & 24.19 \(\pm\) 392.39 & 19.87 \(\pm\) 19.4 b & 46.40 \(\pm\) 17.53 a & 36.41 \(\pm\) 5.39 a & 22.49 \(\pm\) 4.01 b \\ meso-23-butanediol & 150,000 [36] & 35,18.15 \(\pm\) 25.13 a & 22.42 \(\pm\) 413.43 & 35.47 \(\pm\) 301.7 a & 0.25 \(\pm\) 0.67 b & 1.39 \(\pm\) 1.98 b \\ (mg/L) & 800 [36] & 24.42 \(\pm\) 70.2 b & 32.06 \(\pm\) 7.72 a & 24.01 \(\pm\) 51.2 b & 18.72 \(\pm\) 2.87 b & 19.64 \(\pm\) 6.45 b \\
1-Decanol & 40 [40] & 15.03 \(\pm\) 3.00 a & 14.77 \(\pm\) 2.39 a & 12.78 \(\pm\) 16.87 a & 12.77 \(\pm\) 14.18 b & 12.12 \(\pm\) 16.1 b \\ Benzyl alcohol & 90,000 [36] & 382.85 \(\pm\) 113.74 b & 1258.33 \(\pm\) 1270.1 a & 527.21 \(\pm\) 254.85 b & 544.30 \(\pm\) 2654.0 b & 46.11 \(\pm\) 1723.23 b \\
2-Prepylethanol & 10,000 [25] & 226,423.31 \(\pm\) 7850.73 a & 130,275.25 \(\pm\) 2461.30 a & 28,433.94 \(\pm\) 14819.99 a & 17,845.87 \(\pm\) 7045.54 a & 30,107.99 \(\pm\) 235.91.23 a \\
1-Dodecanol & 28 \(\pm\) 0.74 a & 2.37 \(\pm\) 0.56 ab & 18.17 \(\pm\) 0.73 c & 0.88 \(\pm\) 10.06 d & 0.57 \(\pm\) 10.6 d \\ (E)-G-dansarcomene & 0.05 [25] & 15.31 \(\pm\) 5.79 a & 16.59 \(\pm\) 42.74 b & 10.08 \(\pm\) 2.68 & 10.41 \(\pm\) 2.82 b & 9.47 \(\pm\) 17.0 b \\ Methyl octanoate & 200 [38] & 9.86 \(\pm\) 4.62 ab & 11.87 \(\pm\) 19.4 a & 5.86 \(\pm\) 2.66 b & 8.17 \(\pm\) 3.68 a & 7.63 \(\pm\) 4.5 b \\ Propyl octanoate & - & 8.80 \(\pm\) 6.61 ab & 13.21 \(\pm\) 0.22 a & 11.55 \(\pm\) 4.06 b & 5.61 \(\pm\) 7.00 b & 3.27 \(\pm\) 6.05 c \\ Isobutyl octanoate & - & 2.82 \(\pm\) 0.81 & 2.89 \(\pm\) 0.29 a & 2.20 \(\pm\) 0.73 ab & 1.81 \(\pm\) 0.82 b & 1.62 \(\pm\) 10.6 b \\ Isoamyl lactate & - & 144.81 \(\pm\) 114.5 a & 22.07 \(\pm\) 144.04 a & 273.75 \(\pm\) 1265.03 a & 275.88 \(\pm\) 87.64 a & 333.037 \(\pm\) 251.57 a \\ Methyl decanoate & - & 73.20 \(\pm\) 38.38 & 73.67 \(\pm\) 2.79 a & 9.18 \(\pm\) 5.86 d & 80.78 \(\pm\) 229.62 & 6.68 \(\pm\) 8.81 ab \\ Isoamyl octanoate & 125 [29] & 19.78 \(\pm\) 109.6 a & 18.66 \(\pm\) 37.0 a & 9.47 \(\pm\) 2.55 b & 8.34 \(\pm\) 278.8 b & 10.19 \(\pm\) 5.23 b \\ Methyl salicylate & - & 19.13 \(\pm\) 4.49 b & 14.069 \(\pm\) 225.51 a & 29.85 \(\pm\) 14.90 b & 19.66 \(\pm\) 4.49 b & 14.78 \(\pm\) 7.84 b \\ Ethyl isopentyl & - & 169.46 \(\pm\) 136.97 a & 174.63 \(\pm\) 93.52 a & 232.41 \(\pm\) 146.8 a & 190.51 \(\pm\) 76.28 a & 329.11 \(\pm\) 194.12 a \\ succinate & - & 19.43 \(\pm\) 10.9 & 907.62 \(\pm\) 99.15 a & 1330.56 \(\pm\) 825.61 a & 952.80 \(\pm\) 449.08 a & 1157.88 \(\pm\) 923.19 a \\ Linload & 15 [25] & 2.58 \(\pm\) 0.15 c & 4.70 \(\pm\) 2.47 a & 3.63 \(\pm\) 0.37 b & 0.00 \(\pm\) 0.00 d & 3.20 \(\pm\) 0.89 b \\
4-Terpineol & 500 [30] & 1.03 \(\pm\) 0.29 b & 2.20 \(\pm\) 2.36 a & 1.57 \(\pm\) 0.54 b & 1.12 \(\pm\) 0.80 b & 0.99 \(\pm\) 0.66 b \\ \(\beta\)-Citronfield & 100 [25] & 11.72 \(\pm\) 47.9 a & 12.15 \(\pm\) 6.29 a & 6.68 \(\pm\) 3.76 b & 6.25 \(\pmFor terpenes, there were higher average concentrations of \(\beta\)-citronello and geraniol in JDP and BHB regions compared to those in the HZB, LP, and XJ regions, except for geraniol in HZB, which showed no difference between JDP and BHB (Table 2).