## 1 Introduction  
Volatile organic compound (VOC) contaminants, such as chlorinated hydrocarbon (CHC) and petroleum hydrocarbon (PHC) compounds, are commonly found in near-surface soils, and they pose a serious environmental issue owing to their large-scale production and extensive utilization in the manufacturing industry [1; 2; 3]. These VOC vapors can migrate from contaminated near-surface soils into buildings via overlaying building foundations, thereby resulting in higher indoor VOC concentrations than those of the outdoor environment [4; 5]. The inhalation of VOC vapors inside a building is considered to be a significant exposure pathway at VOC-contaminated sites and poses a severe hazard to human health [1; 4; 6; 7]. Under building foundations, several factors influence VOC vapor transport behavior [8; 9]. For instance, previous studies have proposed that soil temperature changes significantly influence VOC transport behaviors [8], and that the diffusive transport rates of VOCs are greater under higher temperatures in static temperature environments [10; 11; 12; 13]. However, owing to the dynamic nature of these environments and/or heterogeneities in the geophysical properties of subsurface soil, the VOC vapor transport behavior may be complex or counterintuitive in some special cases. [PERSON] et al. (2014) [PERSON] et al. (2014) determined an inverse correlation between the subsurface soil temperature and VOC flux changes on the basis of field observations at depths of up to 3 m in near-surface soils. Although the changes in the in situ trichloroethylene (TCE) fluxes were positively correlated with the in situ temperature changes at shallower locations, an inverse correlation was revealed for deeper locations. These findings may be related to those reported by [PERSON] and [PERSON] (2017) [PERSON] and [PERSON] (2017), who observed that changes in the indoor tetrachloroethylene (PCE) concentration were closely correlated with relatively shallow soil temperatures as opposed to deeper soil temperatures at a depth range of approximately 3 m. However, to the best of our knowledge, this inverse correlation under dynamic temperature environments has not been experimentally demonstrated or investigated in the laboratory, as most laboratory investigations on gas-phase diffusive VOC transport experiments in soils have been conducted under static temperature conditions [14; 15; 16; 17; 18; 19; 20; 21; 22]. In a few laboratory-based studies that have considered dynamic environments in near-surface soils, the correlation between temperature and VOC flux changes was generally found to be positive [22; 23; 24]. In the experiments reported by [PERSON] et al. (2003) using a mesocosom-scale simulator facility [24], soil surface temperature changes were driven by diurnal temperature variations (18-24 \({}^{\circ}\)C). Their study showed a correlation between changes in soil surface temperature and total hydrocarbon flux from the soil surface. In another study conducted by [PERSON] and [PERSON] (1993) [PERSON] and [PERSON] (1993), the influences of field conditions, such as temperature and relative humidity (RH) changes above the soil surface, were investigated. In their experiments, the temperature changed diurnally, while the RH was maintained at a relatively constant value. Changes in the benzene flux from the soil surface were also found to be correlated with the temperature changes. Therefore, more extensive investigations must be conducted on the correlation between the soil temperature and VOC flux changes not only for the soil surface but also for the deeper layers, owing to the inconsistent conclusions drawn among previous laboratory experiments and field observations. In this study, we aim to experimentally investigate the occurrence and mechanisms of the inverse correlation between the changes in temperature and the vertical vapor-phase VOC diffusive flux in soils.