The Fate, Transport, and Microbial Effects of Veterinary Antimicrobials in the EnvironmentEPA Grant Number: F6A10013
Title: The Fate, Transport, and Microbial Effects of Veterinary Antimicrobials in the Environment
Investigators: Sanders, Sarah Marie
Institution: Auburn University Main Campus
EPA Project Officer: Lee, Sonja
Project Period: September 1, 2006 through September 1, 2008
Project Amount: $106,672
RFA: STAR Graduate Fellowships (2006) RFA Text | Recipients Lists
Research Category: Academic Fellowships , Ecological Indicators/Assessment/Restoration , Fellowship - Biological Systems Engineering , Fellowship - Civil Engineering
The main purpose of my M.S. thesis is to advance the current state of knowledge on veterinary antimicrobial fate and transport processes in soils. The specific questions I plan to answer through research are:
Question 1: What is the mobility and fate of selected individual antimicrobials in selected aquaculture soils from Alabama?
Question 2: How does one antimicrobial affect the fate and transport of another antimicrobial?
Question 3: What is the effect of individual antimicrobials and antimicrobial mixtures on the structure of microbial communities in selected soils?
I have selected two veterinary antimicrobials, Sulfadimethoxine (SDM) and Ormetoprim (OMP), and two Alabama soils with varying physiochemical properties for my research. SDM and OMP were chosen because they have been detected in environmental samples, the SDM/OMP combination is one of the only three U.S. Food and Drug Administration approved aquaculture antimicrobials (sold under the name Romet30®), and are likely to occur in mixtures.
Two different sets of experiments, miscible displacement soil column experiments and batch sorption equilibrium experiments, will be carried out to determine the fate and transport of antimicrobials in the selected soils (Questions 1 & 2). In the soil column experiments the antimicrobial and antimicrobial mixtures will be applied as a step input (in concentrations similar to those observed in the environment) with a tracer solution until the eluent and effluent concentrations are equal. A fraction collector will be used to collect the samples. In the batch sorption equilibrium experiments a known amount of soil will be added to several centrifuge tubes and then each tube will be supplied with varying concentration of antimicrobial or antimicrobial mixture. The soil and solution will be allowed to reach equilibrium and will then be centrifuged. The supernatant will be collected and analyzed. Both, the supernatant from the batch sorption experiments and the effluent from the miscible displacement soil column experiments, will be analyzed using a liquid chromatograph triple quadrupole mass spectrometer (LC/MS/MS). These experiments will be carried out with each soil and each antimicrobial and then for each soil with the antimicrobial mixture.
Phospholipid ester-linked fatty acid (PLFA) analysis, a widely used approach for studying changes in soil microbial community structure, will be performed before and after antimicrobials are introduced to determine the effects the antimicrobials and antimicrobial mixtures have on microbial community structures (Question 3). Gas Chromatography (GC) will be used to analyze these results.
These experiments will produce several types of significant new knowledge regarding the fate, transport, and microbial effects of veterinary antimicrobials in soils. The miscible-displacement experimental results will be modeled using CXTFIT and HYDRUS-1D and will yield estimates of key fate-and-transport parameters, including antimicrobial diffusion-dispersion coefficients, retardation factor, distribution coefficients, and degradation rates. These results will be compared with those of the batch sorption equilibrium experiments for a more realistic view of occurrences in the soil. The results of the PLFA analysis will indicate possible microbial community effects in the selected soils. These experiments will improve our ability to make quantitative predictions of antimicrobial fate and transport in soil and of loadings to receiving water bodies. Further, it will help accurately predict environmental concentrations and microbial and ecological effects.