Pentachlorophenol (PCP) vertical transportation in soil column during its phototransformation on the soil surface was investigated using a new designed photoreactor. Three kinds of soils were used to study the effect of soil water and soil properties. In air-dried sandy loam, no obvious PCP transportation occurred in the soil profile when PCP was phototransformed on the soil surface. And the average removal of PCP in the whole soil column was close to zero after 48 h irradiation. In the moist sandy loam, PCP in the deeper soil could transport to the soil surface with water evaporation and then be transformed during UV irradiation, thus the average PCP removal in the whole soil column was improved. When the initial water contents are 9.3 and 19.2%, the average PCP removal in the sandy loam after 48 h irradiation accounted to 20.9 and 39.9%, respectively. The improving of PCP removal induced by soil water was limited in the clay and silt soils where PCP transportation was impeded because of their higher adsorption capacity. In the silt soil where the initial water content was 19.7%, not only PCP transportation in the deeper soil but also PCP phototransformation on the surface was inhibited seriously because of the high organic matter content of 18%.

The partial phase transformation of nanometer TiO₂ powder from anatase phase to rutile phase was realized by heat-treatment and a new TiO₂ photocatalyst which could be excited by visible light was obtained. The heat-treated TiO₂ powder at different stage of transition crystal was characterized and monitored by XRD, TEM, FT-IR and UV-vis DRS methods. The test of photocatalytic activity of the heat-treated TiO₂ powder was carried out by the photocatalytic degradation of rhodamine B and acid orange II dyes, respectively, in aqueous solution under visible light irradiation. The results indicate that the nanometer TiO₂ photocatalyst heat-treated at 500°C for 60 min shows the highest photocatalytic activity, that is, it can effectively degrade the rhodamine B and acid orange II under visible light irradiation. The remarkable improvement of photocatalytic activity of heat-treated TiO₂ powder at 500°C for 60 min was mainly illustrated by the formation of special interphase between rutile and anatase phases, which not only restrains the recombination of photogenerated electrons and holes, but also reduces the adsorbability of nanometer anatase TiO₂ powder properly for various dyes. Additionally, the effects of dye-assisting chemicals such as Na₂CO₃ and NaCl on the photocatalytic degradation were also studied.