Location: Contaminant Fate and Transport Research2012 Annual Report
1a. Objectives (from AD-416):
Determine the relationships between manure management and populations of human pathogens and antibiotic resistant bacteria (ARB) that result in new recommendations for best management practices (BMPs); Develop effective methods and practices to protect crops from pathogen contamination; Develop management practices to minimize the transport of pathogens (e.g. E. coli O157:H7, Cryptosporidium, enterococcus, Salmonella) from concentrated dairy and beef cattle operations to water resources.
1b. Approach (from AD-416):
Conduct laboratory and field experiments to examine the important biological, chemical, and physical processes affecting the prevalence and distribution of pathogenic and antibiotic resistant bacteria on representative farms in the Santa Ana River watershed. Studies will be conducted at various scales to determine the persistence (survival) of E. coli O157:H7 in its sources on these farms and assess potential factors influencing pathogen survival in the root zone and contamination of leafy greens. Laboratory scale study will be conducted to quantify critical processes influencing the dissemination of pathogens in the watershed by runoff, streams and rivers. Factors influencing the treatment of contaminated surface waters by sand filtration will also be investigated to more fully assess its capabilities and potential weaknesses. Data obtained from these studies will be used to develop best management practices (BMPs) and low cost treatment technologies for immobilization and inactivation of pathogens from concentrated animal feeding operations (CAFOs) to water and food resources.
3. Progress Report:
Mathematical models to simulate the movement of pathogens through aquifers and soils frequently do not consider the significant influence of transients in solution ionic strength (IS) and velocity on pathogen fate. A sophisticated transport model was modified and theory was developed to mechanistically account for the transport, retention, and release of pathogens with transients in IS and velocity. The calibrated model provided a satisfactory description of the observed release behavior for a range of microbe types and sizes. Furthermore, analysis of fitted model parameters indicates that microscopic heterogeneities on the soil and/or microbe played an important role in pathogen interactions, especially for smaller sized microorganisms. This information will be of interest to scientists and engineers concerned with predicting the fate of pathogens in soils and aquifers. Data on E. coli O157:H7 persistence in major fresh produce-growing soils are limited due to the complexity in datasets generated from different environmental variables and bacterial taxa. Using the Ayasdi Iris platform, which employs Topological Data Analysis (TDA) methods, we have reconstructed the relationship structure of E. coli O157:H7 survival in 32 soils (16 organically, 16 conventionally managed soils) from California (CA) and Arizona (AZ) with a multi-resolution output. Here, we constructed our topological data using three E. coli O157, and three non- E. coli O157 strains to test their persistence in typical agricultural soils collected from 3 major fresh produce growing areas of California and Arizona. This information will be of interest to scientists and growers interested in understanding fate and survival of E. coli O157 and non-E. coli O157 in organically and conventionally managed soils.
Bradford, S.A., Torkzaban, S., Simunek, J. 2011. Modeling colloid transport and retention in saturated porous media under unfavorable attachment conditions. Water Resources Research. 47:W10503. DOI:10.1029/2011WR010812.