Investigation of Pentachlorophenol Vertical Transportation in Soil Column During its Phototransformation on the Soil Surface

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%.