## 3 Results  
### Inverse Correlation between Temperature and Benzene Flux Changes  
Figure 4 shows a comparison of the changes in the RH and corresponding water flux measured at the top (outlet) space, and the benzene concentrations and corresponding fluxes measured for the bottom (inlet) and top spaces between the static (Run 1) and dynamic (Run 2) temperature experiments. In Run 1 under the static temperature condition (Figure 4a), the RH was initially close to 100% and, therefore, increased slightly and gradually with time at a constant temperature owing to the slow evaporation of water. Correspondingly, an insignificant water vapor flux was observed throughout the experiment. The benzene concentration at the bottom decreased with time as a result of benzene intrusion into the soil sample. Simultaneously, the benzene concentration at the top increased with time as a result of benzene emission from the soil sample. As the difference between the bottom and top benzene concentrations generally decreased with time, the bottom and top fluxes decreased in the overall trend. The bottom flux was generally larger than the top flux owing to benzene infiltration into ineffective pore spaces and/or the dissolution of benzene into water within the soil.  
On the other hand, in Run 2 under the dynamic temperature condition (Figure 4b), a decrease and subsequent recovery in the RH occurred in response to the temperature rise and drop, as indicated by the arrows. The decrease in RH may have largely reflected an increase in the amount of saturated water vapor as a result of rising temperature, while the recovery of the RH may have largely reflected a decrease in the amount of saturated water vapor as a result of the decreasing temperature. Peaks of negative and positive water fluxes were shown; therefore, peaks of water condensation and evaporation within the column were also shown. Consequently, the water flux change was inversely correlated with the temperature change. The bottom and top benzene concentrations showed changes similar to those observed in Run 1 under static temperature conditions (Figure 4a). However, the top and bottom fluxes changed differently from those in Run 1. The change in the top benzene flux was largely correlated with temperature change, as can be expected from the larger rate of diffusive transport for VOCs in higher temperature soils reported in previous studies [11; 12; 13]. In contrast, an inverse correlation was found between the changes in the temperature and bottom benzene flux, as indicated by the arrows. It appeared that the onset and termination of the increased bottom benzene fluxes occurred near the peaks of negative and positive water vapor fluxes (i.e., peaks of condensation and evaporation of water).  
\begin{table}
\begin{tabular}{c c c c} \hline
**Experiment** & **Silica Sand** & **Water Content (wt\%)** & **Temperature** \\ \hline Run 1 & Coarser-grained & 10 & Static \\ Run 2 & Coarser-grained & 10 & Dynamic \\ Run 3 & Finer-grained & 10 & Dynamic \\ Run 4 & Coarser-grained & Air-dried (\(\sim\)0.3) & Dynamic \\ Run 5 & Finer-grained & Air-dried (\(\sim\)0.3) & Dynamic \\ \hline \end{tabular}
\end{table}
Table 1: Silica sand, water content, and temperature in each experiment.