MACRO AND MICRO CHARACTERISTICS OF LATERITE CON-TAMINATED BY PHOSPHORUS IN MOVEMENT AND TRANSFORMA-TION CONDITION

The movement and transformation of laterite contaminated by phosphorus are investigated in this paper. Soil column migration tests are carried out on Yunnan laterite with sodium hexametaphosphate associated with the influence of the depth of soil column tests. It shows that the relative quality and clay content decrease as the depth increase. The liquid limit, plastic limit and plasticity index decrease as the depth increase, their minimum values appear in the boundaries moisture content. The beta sodium tecto-dioxoferrate is generated, its maximum value appears in the phosphorus content. The ferrous oxide content has seriously changed on the surface of soil column. The microstructure images show that the structural unit of laterite contaminated by phosphorus have changed from compactly squamose structure to honeycomb structure and then to incompactly bee coagulation structure. The maximum value appears in the void ratio of the microstructure images. The iron and aluminum ion concentration of soaking solution on the surface of soil column gradually increase as time gone. Few iron and aluminum ion are found in seepage solution. The mechanism towards laterite contaminated by phosphorus could be accounted for hydrolyzation, adsorption-complexation, reduction-oxidation and salification. The changes of transportation and transformation characteristics of laterite contaminated by phosphorus may be the result of those comprehensive actions.