Page Banner

United States Department of Agriculture

Agricultural Research Service

Research Project: Protection of Food and Water Supplies from Pathogen Contamination

Location: Contaminant Fate and Transport Research

2012 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.


4. Accomplishments


Review Publications
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.

Ibekwe, A.M., Leddy, M.B., Bold, R.M., Graves, A.K. 2011. Bacterial community composition in low-flowing river water with different sources of pollutants. FEMS Microbiology Ecology. 79:155-166.

Ibekwe, A.M., Lesch, S.M., Bold, R.M., Leddy, M.B., Graves, A.K. 2011. Variations of indicator bacteria in a large urban watershed. Transactions of the ASABE. 54(6):2227-2236.

Ibekwe, A.M., Murinda, S.E., Graves, A.K. 2011. Genetic diversity and antimicrobial resistance of Escherichia coli from human and animal sources uncovers multiple resistances from human sources. PLoS One. 6(6):1-12.

Torkzaban, S., Wan, J., Tokunaga, T.K., Bradford, S.A. 2012. Impacts of bridging complexation on the transport of surface-modified nanoparticles in saturated sand. Journal of Contaminant Hydrology. 136-137:86-95.

Ibekwe, A.M., Murinda, S.E., Graves, A.K. 2011. Microbiological evaluation of water quality from urban watersheds for domestic water supply improvement. International Journal of Environmental Research and Public Health. 8:4460-4476.

Bradford, S.A., Kim, H. 2012. Causes and implications of colloid and microorganism retention hysteresis. Journal of Contaminant Hydrology. 138-139:83-92.

Wang, D., Paradelo, M., Bradford, S.A., Peijnenburg, W.J., Chu, L., Zhou, D. 2011. Facilitated transport of Cu with hydroxyapatite nanoparticles in saturated sand: Effects of solution ionic strength and composition. Water Research. 45:5905-5915.

Ma, J., Ibekwe, A.M., Wang, H., Xu, J., Leddy, M., Yang, C., Crowley, D.E. 2012. Assimilable organic carbon (AOC) in soil water extracts using Vibrio Harveyi BB721 and its implication for microbial biomass. PLoS One. 7(5): e28519. DOI: 10.1371/journal.pone.0028519.

Shange, R.S., Ankumah, R.O., Ibekwe, A.M., Zabawa, R., Dowd, S.E. 2012. Distinct soil bacterial communities revealed under a diversely managed agroecosystem. PLoS One. 7(7):e40338. doi:10.1371/journal.pone.0040338.

Ibekwe, A.M., Ma, J., Murinda, S.E. 2016. Bacterial community composition and structure in an urban river impacted by different pollutant sources. Science of the Total Environment. 566-567:1176-1185. doi: 10.1016/jscitotenv.2016.05.168.

Wang, D., Bradford, S.A., Harvey, R.W., Hao, X., Zhou, D. 2012. Transport of ARS-labeled hydroxyapatite nanoparticles in saturated granular media is influenced by surface charge variability even in the presence of humic acid. Journal of Hazardous Materials. 229-230:179-176.

Last Modified: 10/16/2017
Footer Content Back to Top of Page