## 1 Introduction  
Contamination caused by petroleum leakage occurring during oil production, transportation, refinement, and mishandled storage is widespread [1; 2; 3; 4; 5]. Benzene, toluene, ethylbenzene, and xylene (BTEX) are volatile organic compounds in petroleum that result in neurotoxicity, genotoxicity, and reproductive toxicity [6; 7; 8]. Due to its mutagenic and high migration, BTEX leads to the deterioration of aquatic and terrestrial environment quality when released into the environment and causes adverse effects on human health when absorbed by breathing, touching, or swallowing [9; 10; 11]. Natural attenuation processes, such as biomineralization, adsorption, advection, dispersion, and volatilization, can all decrease the number of contaminants in an aquifer [12; 13; 14]. Since biomineralization uses microorganisms to convert BTEX into inorganic substances, it is considered an environmentally friendly technology [15; 16]. In the 1960s, scientists found that some bacteria could use BTEX as their source of carbon energy, thus decomposing the BTEX into CO2 and water, which confirmed that it could be aerobically degraded [17; 18]. However, the underground environment is usually anaerobic, and the anaerobic mineralization of BTEX is more feasible and practical. BTEX can be biodegradable with NO3-, Mn4+, Fe3+, and SO4-, and CO2 as terminal electron acceptors [19; 20; 21; 22]. As NO3- dissolves well in water, and denitrification yields the highest energy, NO3- can easily be applied for anaerobic mineralization [23; 24; 25; 26]. The mineralization mechanism of BTEX under denitrification conditions is as follows: BTEX acts as both a carbon source and energy for the growth and reproduction of bacteria, and NO3- acts as an electron acceptor to convert hazardous materials to CO2 and H2O, leading to the mineralization of BTEX [27; 28]. The BTEX mineralization equations are as follows:  
\[\mathrm{C_{6}H_{6}+6 NO_{3}^{-}+6H^{+}}\to 6\mathrm{CO_{2}+3N_{2}+6H_{2}O} \tag{1}\]  
\[\mathrm{C_{7}H_{8}+7.2 NO_{3}^{-}+7.2H^{+}}\to 7\mathrm{CO_{2}+3.6N_{2}+7.6H_{2}O} \tag{2}\]  
\[\mathrm{C_{8}H_{10}+8.4 NO_{3}^{-}+8.4H^{+}}\to 8\mathrm{CO_{2}+4.2N_{2}+9.2H_{2}O} \tag{3}\]  
It was previously believed that this mineralization could solve the problem of BTEX pollution. However, mineralization impacts the water-rock interaction, especially in the dissolution and precipitation of carbonate rocks. Studies in this area have found that transforming BTEX to inorganic C involves a series of reactions, resulting in a decreased pH and the dissolution of carbonate mineral calcite [29]. Two main aspects influence the dissolution and precipitation of CaCO3 via biomineralization. First, under denitrification conditions, BTEX is converted into neutral or acidic organic compounds, which induce a variety of pH levels [30; 31]. Second, BTEX is converted into end-product CO2 (Equations (1)-(3)), which, together with H+ from the water, forms H2 CO3 and causes the pH to decrease (Equations (4)-(8)) [27]. \[\mathrm{CO_{2}+H_{2}O}\leftrightarrow\mathrm{H_{2}CO_{3}} \tag{4}\]  
\[\mathrm{H_{2}CO_{3}}\leftrightarrow\mathrm{H^{+}+HCO_{3}}^{-} \tag{5}\]  
\[\mathrm{HCO_{3}}^{-}\leftrightarrow\mathrm{H^{+}+CO_{3}}^{2-} \tag{6}\]  
\[\mathrm{H_{2}O}\leftrightarrow\mathrm{H^{+}+OH^{-}} \tag{7}\]  
\[\mathrm{CaCO_{3}}\leftrightarrow\mathrm{Ca^{2+}+CO_{3}}^{2-} \tag{8}\]  
Currently, most studies show that the degradation of BTEX promotes the dissolution of calcium carbonate, whether this is demonstrated through indoor column experiments or field data collection [32; 33]. Moreover, several studies suggest that the pH could rise slightly as CO2 is degassed from water and autotrophic microbial metabolism occurs, resulting in carbonate precipitation and removal [34; 35]. Until now, few studies have quantitatively analyzed the effect of BTEX mineralization on the dissolution and precipitation of CaCO3. Therefore, based on hydrogeochemical and organic biomineralization theory, a mechanism model was revealed.