LEACHING EXPERIMENT STUDY ON WEATHERING CHARACTERISTICS OF CARBONATE ROCKS IN KARST ROCKY DESERTIFICATION AREA

Karst rocky desertification(KRD)has been posing a threat to the ecological environment and restraining the sustainable development of local economy and society in China's karst areas. The development of rocky desertification is closely related to not only the soil surface runoff loss and underground leakage but also the formation of the overlying red clay. To explore the weathering characteristics of carbonate rocks and its relationship with Karst rocky desertification, the limestone and the dolomite samples collected from the Zhenfeng-Guanling Huajiang Rock Desertification Demonstration Area were carries for leaching experiments. The results show that,(1)The wet-hot conditions can increase the dissolution rate of carbonate, and the increasing extent of dolomite is larger than that of limestone; the particle size has no significant effect on the limestone, while the particle size has a significant effect on the elution rate of dolomite, showing that the smaller the particle size, the faster the dissolution rate. There is a strong correlation between the total leaching rate of carbonate rocks and the leaching rate of Ca²⁺. (2)Limestone is more prone to dissolution than dolomite. Differential dissolution occurs intensely on the surface and interior of limestone, forming a large number of dissolved pores(pores and holes),resulting in very serious soil erosion. Rocky desertification is prone to occur in the area and the degree of rocky desertification is serious. The control of rocky desertification in limestone area should pay attention to the differential dissolution of limestone, retain the existing soil and improve the ability of water conservation of geological body to accelerate weathering. Dolomite joints and fissures are well developed, which are prone to physical weathering and disintegration, forming uniform gravel and gravel soil. The broken fine particles are beneficial to weathering, but the surface soil layer is thin and the water retention is poor, so it is difficult for plants to grow. In dolomite desertification area, water retention ability of the soil should be improved, wet weathering environment should be created, to promote dolomite weathering.