The effect of texture and rock fragments on solute transport scale in stony soils

Scale-dependence of solute transport parameters in soil is known to be mainly due to the increasing scale of heterogeneities with transport distance and with the lateral extent of the transport field examined. The main objective of this study was evaluating the role of stones and texture on the transition of local scale to the transport scale. The soil in question contains a significant internal heterogeneity in terms of texture and stones, changing with depth and along the horizontal extent of the experimental area. Spectral analysis was used to quantify the relationship between the solid phase heterogeneities and the scale dependence of the solute transport parameters.. In our study, the moments of BTCs were calculated starting from time-normalized resident concentrations, obtained by time domain reflectometry (TDR) probes at different depths in several soil sites along a transect. The Generalized Transfer Function was used to describe the evolution of solute spreading along the soil profile at each observation site by analyzing the propagation of the moments of the concentration distributions. Our analysis showed that the organization in hierarchical levels of soil variability may have major effects on the differences between solute transport behaviour at transport scale and transect scale, as the transect scale parameters will include information from different scales of heterogeneities.