Chemical Transport in Undisturbed Soils Estimated Using Transfer Function Models

Assessment of chemical transport in vadose zone environments is critical for conserving the quality of groundwater. This project evaluated lognormal and convection-dispersion transfer function models with a conservative tracer through soil columns with silt loam soil material. The soil cores were sampled with minimal disturbance to maintain the inherent soil structure prior to running breakthrough curves with computed tomography (CT) imaging. Estimation of transport parameters for these undisturbed, heterogeneous silt loam cores were not significantly improved with group-pixel averages. This was due to transport through the macropores present in the sample cores. With more homogeneous cores, group-pixel averages of 1.0 x 1.0 mm or 2.0 x 2.0 mm were adequate to reduce fluctuations of CT image numbers. When using resident concentration estimates, the estimations improved since most of the chemical moved through the macropores. Applications of transfer function models were used in undisturbed soil columns with a conservative tracer. Assessment of chemicals with adsorption properties may be evaluated in the future.