Contaminant Dispersion in Agricultural Soils as Influenced by Land Management Practices

Abstract:

Flow and transport processes in agricultural soils are of paramount importance for groundwater quality and environmental health. We hypothesize that the structural heterogeneity generated by different land management practices has a significant influence in the transport and spread of pesticide and fertilizer contaminants in agricultural soils. In this work, we provide a statistical description of advection-dominated dispersion in soils characterized by two common land management practices—ploughed and no tillage—and present a flow and transport model that upscales pore-scale statistics to the resulting macroscopic transport behavior. First, we obtain the digital pore space geometry of representative soil samples from micro-CT scanning. Second, we investigate the dispersion and velocity distribution of tracer particles by direct numerical simulations (DNS) in each sample. Finally, we parameterize a Continuous Time Random Walk model from pore-scale Langrangian statistics of particle trajectories to predict the temporal evolution of dispersion for each sample. A foundational understanding of the differences in pore-scale particle dynamics of soils subjected to different land management practices can significantly advance our ability to model contaminant transport in agricultural lands.