Estimation and upscaling of dual-permeability model parameters for the transport of E. coli D21g in soils with preferential flow

Abstract

Dual-permeability models are increasingly used to quantify the transport of solutes and microorganisms in soils with preferential flow. An ability to accurately determine the model parameters and their variation with preferential pathway characteristics is crucial for predicting the transport of microorganisms in the field. The dual-permeability model with optimized parameters was able to accurately describe the transport of E. coli D21g in columns with artificial macropores of different configurations and lengths at two ionic strength levels (1 and 20 mM NaCl). Correlations between the model parameters and the structural geometry of the preferential flow path were subsequently investigated. Decreasing the macropore length produced a decrease in the apparent saturated hydraulic conductivity of the macropore domain and an increase in the mass transfer between the macropore and matrix domains. The mass transfer coefficient was also found to be dependent on the configuration of the preferential flow pathway. A linear superposition approach was used to estimate field-scale preferential transport behavior for hypothetical fields with different amounts and configurations of macropores. Upscaling procedures were numerically investigated to predict this field-scale transport behavior from column-scale parameters. The upscaling method provided a satisfactory prediction of the field results under the tested scenarios. This information will be useful in assessing the risks of microbial transport due to preferential flow.

Contamination of water resources by pathogenic bacteria

“…Considerable work recently has been done towards understanding pathogen transport in the vadose zone (Wang et al [2014a]; [2014b]; Unc and Goss [2004]; Darnault et al [2004]). Groundwater can be contaminated by seepage and percolation of contaminated water from the vadose zone (Darnault et al [2004]).…”

“…The presence of straw and coarse organic matter influences the persistence of bacteria, and manure application changes the physical configuration of soil, the soil chemistry, and the properties of the microbial cells, which control the survival and persistence of bacteria in soils. Another recent study by Wang et al ([2014]) assessed the transport of E. coli in soils with preferential flow. The authors reported that a decrease in macropore length resulted in a decreased apparent saturated hydraulic conductivity of the macropore and an increase in the mass transfer.…”

“…The authors reported that a decrease in macropore length resulted in a decreased apparent saturated hydraulic conductivity of the macropore and an increase in the mass transfer. Wang et al ([2014a]; [2014b]) concluded that macropore length has a considerable influence on preferential transport of E. coli .…”

Evaluation of dual permeability of gas flow in municipal solid waste: Experiment and modeling

“…Where is the shape factor, developed by Zimmerman . is the mass transfer coefficient, depended largely on the pore structure and preferential flow pathway . The gas transfer term is ignored in the single‐permeability model, which have “one” permeability and “one” porosity.…”

Experimental and Numerical Investigations of Influence on Overland Flow and Water Infiltration by Fracture Networks in Soil

“…Several previous studies implicate that one-dimensional (1D) preferential flow and transport models are not comprehensive enough to simulate subsurface flow and solute transport in undulating fields and recommend the use of two-dimensional (2D) profile models or three-dimensional (3D) models instead [32][33][34][35]. However, there are a few 2D and 3D models that support simulation of preferential flow and transport.…”