## 3 Results and Discussion
### Overview of Metabolites Discovered in Filed Soil (Contaminated Site)
There are microbiologically inhibited metabolites in field soil (contaminated soil) suggested in group A site in the heat map and those metabolites (Table 4), which are based on \(p\)-value  
Figure 3: Partial least squares–discriminant analysis (PLS–DA) including control (not contaminated) and field (contaminated soils) using ultra-high-performance liquid chromatography (UHPLC)–Orbitrap–MS; (control is not contaminated soil located 1 km away from the accident site, field is contaminated soil located from 100 m to 500 m away along the diffusion direction of gas cloud at the accident site). and t.stat (\(t\)-test result) value by screening the variables (metabolites) through \(t\)-test, include selagine, 2-Iodophenol, and 3 beta-(1-pyrrolidin)-5 alpha-pregnant-11,20-dione and are considered major downregulated metabolites in field soil. Moreover, phytocceramide also discovered in sphingolipid metabolism was downregulated in field soil (contaminated soil). According to [24], sphingolipids are common components of cell membranes of eukaryotic microbes, and this plays an important role in cell motility and growth. Sphingolipids are also signaling molecules, regulating many important cellular processes related to apoptosis and autophagy [25]. Inhibition of this metabolism in field soil (contaminated soil) is questionable because upregulation of fatty acid biosynthesis for protecting bacterial cell membrane was discovered in field soil. However, it is clear that bacteria cannot activate sphingolipid metabolism due to chemical stress or unknown reason. Further research is needed to understand the reason why this metabolism becomes inhibited. Figure 4: Heat map visualization of control (not contaminated soil) and field (contaminated soil); a total of 114 variables shown in heat map filtered by \(p\)-value \(<\) 0.05 through \(t\)-test. Metabolites in A site means downregulation of metabolism due to soil contamination and metabolites in B site means upregulation of metabolism due to soil contamination. The metabolites shown in heat map analysis are suggested in Table 4.  
2.1. Propose the Relationship between Toluene Combustion Products and Metabolites in Toluene Affected Soils  
There are several molecules or metabolites discovered in field soil and contaminated soil. These indicate that the combustion products in the gas cloud have still affected the soil even three years passed after the chemical accident. Herein, Table 4 shows molecules or metabolites semi-identified by MassTRIX Web Database. Those semi-identified molecules are determined based on the lowest mass error value, comparing theoretical mass and measuring mass analyzed by high-resolution mode UHPLC-Orbitrap-Mass. Dibenzofuran discovered in field soil is a polycyclic aromatic compound containing two benzene rings fused to a central furan ring. This has been suggested as one of the products from benzene combustion. [PERSON] et al. explained that benzofuran could be formed in presence of phenoxyl radicals with flame combustion [PERSON] et al. (2016). The 1,2-Dichlorobenzene is a molecule containing chlorine atoms with benzene compounds. This is a derivative of benzene as the most remarkable evidence, which proved field soil around chemical fire accident site had been contaminated by gas cloud. This molecule has the lowest t.stat and \(p\)-value, which is the most upregulated metabolite in field soil, compared to control soil (Table 4). This implies a pollutant related to benzene compounds had strongly affected the soil in the past. Figure 5. Metabolic pathway analysis of field Soil (contaminated soil). 1: Alanine, aspartate and glutamate metabolism, 2: Pyrimidine metabolism. 3: Nitrogen metabolism.