Pathogen Transport and Fate Processes in the Environment at Different Scales

An understanding of pathogen transport and fate in the environment is needed to assess the risk of contamination of water and food resources, and to develop control strategies and treatment options.  This presentation discusses advances to better understand and predict the fate of pathogens in the subsurface at different spatial and temporal scales.   Adhesive interactions of pathogens with surfaces are demonstrated to be strong functions of nanoscale and microscale heterogeneities, interface geometry, and solution and solid phase chemistries.   Pathogen retention and release are shown to be sensitive to these factors as well as spatial variability in hydrodynamic conditions. Pore-network models have been used to account for retention processes, including attachment, straining, and hydrodynamic bridging.  Alternatively, machine learning algorithms have been trained on extensive databases to predict retention parameters.  Steady-state and transient release from episodic changes in solution chemistry and water saturation can greatly impact the long-term fate of pathogens. Ongoing efforts to account for governing physicochemical factors into continuum scale models at the column, hillslope, and watershed scales are highlighted.