2010 Annual Report 1a.Objectives (from AD-416) The overall objective of this project is to improve our understanding of and ability to predict the transport and fate of pathogenic microorganisms at various spatial scales (from pore to plot scale). 1b.Approach (from AD-416) Laboratory experiments will be designed to test specific hypotheses with regard to mechanisms controlling pathogen transport and fate in the environment. The specific experimental approaches and techniques will depend on the research question. For example, we may use measurements of electrophoretic mobility, hydrophobicity, surface charge density, enzyme treatment, FTIR, and TEM imaging to examine surface properties of pathogens that influence their interaction in the environment. We may use batch, micromodel systems, DLVO calculations, pore-scale flow and transport simulation techniques, and saturated and unsaturated column experiments to examine mechanisms of pathogen transport, retention, and survival. Information collected from laboratory studies will be used to refine and improve the predictions of models for pathogen transport and fate. Existing models for pathogen transport and survival will be modified to simulate field scale behavior. Documents SCA with UC Riverside. 3.Progress Report Research has been initiated to modify a pore network model to simulate colloid and microorganism transport and fate in porous media. To date we have compared network simulation results to detailed pore-scale water flow simulations to verify that the cumulative density function of applied hydrodynamic shear has been correctly captured in the network model. We are currently developing a particle trajectory model for the constricted tube geometry. This model will be used to accurately capture the underlying physics of microorganism transport and retention in this relatively simple geometry. The results will then be incorporated into the network model to provide a powerful tool to upscale pore-scale physics to larger spatial scales. Drs. Bradford and Simunek coordinate the work schedules and objectives for all personnel that are funded through this SCA and meet with them on a regular basis to discuss progress. UC Riverside provides Dr. Bradford with a SCA budget on a monthly basis.