Fate and Transport of Pathogen Indicators from PasturelandsEPA Grant Number: F6A10611
Title: Fate and Transport of Pathogen Indicators from Pasturelands
Investigators: Soupir, Michelle L.
Institution: Virginia Polytechnic Institute and State University
EPA Project Officer: Lee, Sonja
Project Period: September 1, 2006 through September 1, 2008
Project Amount: $111,172
RFA: STAR Graduate Fellowships (2006) RFA Text | Recipients Lists
Research Category: Academic Fellowships , Ecological Indicators/Assessment/Restoration , Fellowship - Biological Systems Engineering
The U.S. EPA has identified pathogens as a leading cause of impairments in rivers and streams in the U.S. Pathogens originate from many different sources, but agricultural practices have been cited as the primary contributor to pathogen impairments of rivers and streams. In an attempt to reduce pollutant loading to the nation’s water bodies, TMDLs are being developed to assess water quality problems, identify pollution sources, and determine pollution reductions needed to restore and protect rivers, streams and lakes. Currently, Nonpoint Source (NPS) pollution models are most frequently used to determine the maximum allowable loading rates of bacteria from the identified sources. Most current NPS models completely ignore bacterial subsurface transport and typically simulate bacterial transport to surface waters as a dissolved pollutant. First order decay is most often used to express bacterial die-off, but others have found that bacterial after-growth might occur following excretion or land application of waste.
The goal of this research project is to investigate the fate and transport of E. coli and Enterococcus from pasturelands to improve current NPS modeling efforts. The specific objectives of this study are to: 1) Evaluate various laboratory methods for dispersing E. coli and Enterococcus from particles and for partitioning between particle sizes; 2) Quantify partitioning between E. coli and Enterococcus sorbed to particles in overland flow; 3) Develop die-off equations for E. coli and Enterococcus in cowpies on pasturelands; 4) Study simulated in-stream partitioning between settable and suspended pathogen indicators.
To meet the stated research objectives a combination of laboratory research, field sampling activities, and modeling is needed. Laboratory investigations were initiated to compare different physical and chemical dispersion techniques and screen pore sizes and optimal centrifugation speeds were tested prior to applying these methods to field samples. Runoff samples from pastures, treated with cowpies, will be collected and analyzed for water quality indicators to determine if relationships exist between these indicators and bacterial partitioning ratios. Weather data and bacterial concentrations in the cowpies will also be monitored for an extended period of time to determine bacterial die-off rates and to determine if incorporation of environmental factors will improve the modeling of this process.
The partitioning coefficients and die-off equations developed through this research will have broad impacts on development of new management practices and/or refinement of existing practices implemented to reduce the movement of bacteria from agricultural lands to downstream water bodies. In addition, the research findings will be used to improve the predictive capabilities of existing computer simulation models currently used in TMDL development.