5. **Adsorption**

Organic matters and clays are the most important factors which contribute to adsorption in aquifer and organic matters are dominant. The adsorption equilibrium of CCl4 is associated with concentration of organics and KOC. Silva (Silva et al., 2000) indicated that pore filling was main factor in solute distribution. The aquifer in Qiligou has the characteristics of high runoff, intense flash and less pore fillings, due to the high burial depth, long-term exploration and large production, which is shown in Fig.5. Therefore, adsorption has less influence on decrease of CCl4.
