『Abstract
　The characteristics of nitrate vertical transport in soils collected from Libo and Puding in Guizhou Province were studied by simulating soil column in laboratory. The results were as follows: (1) Vertical transport velocity of nitrate decreased, and the breakthrough curves (BTCs) of nitrate were more dispersed, in each horizon from surface layer to bottom layer in every soil profile. As rocky desertification progressed, the BTCs experienced a gentle up and down trend, and tailing was more obvious. (2) An analytical solute transport model (CXTFIT 2.0) was used to estimate nitrate dispersion coefficient (D) and average pore water velocity (V) from the observed BTCs. The results showed that CXTFIT 2.0 model was suitable in fitting the nitrate transport in these soils. The dispersion coefficient was found to be a function of average pore water velocity. (3) The transport of nitrate was mainly affected by the soil structural coefficient. As soil structural coefficient decreased, nitrate outflow was retarded, and the peak concentration was reduced. Soil bulk density, organic matter, and clay also affected the vertical transport of nitrate. Low bulk density, clay content, and high organic matter content were each associated with faster nitrate transport.

Keywords: Karst regions; Rocky desertification; nitrate; Vertical transport; CXTFIT 2.0; Influencing factors』

Introduction
Materials and methods
　Experimental site
　Basic soil physical and chemical properties
　Measurement of nitrate transport
Results and discussion
　Nitrate BTCs
　The simulating of NO3^--N vertical transport
　Factors influencing NO3^--N vertical transport
　　Structural coefficient
　　Organic matter content
　　Bulk density
　　Clay content
Conclusions
Acknowledgments
References