WATER RESOURCES RESEARCH GRANT PROPOSAL
Project ID: 2004WI79B
Title: Fate of Representative Fluoroquinolone, Macrolide, Sulfonamide and Tetracycline Antibiotics in Subsurface Environments
Project Type: Research
Focus Categories: None
Keywords: groundwater, antibiotics, organic matter, vadose zone
Start Date: 03/01/2004
End Date: 02/28/2005
Federal Funds: $31,592
Non-Federal Matching Funds: $25,713
Congressional District: 2nd
Joel Alexander Pedersen
1. Specific groundwater problem addressed by research proposal. The PIs intend
to investigate the fate and transport of selected antibiotics in soil and
the vadose zone, including the influence of natural organic matter (i.e.,
a soil factor) on the mobility of antibiotics in subsurface environments.
2. Contribution of research findings to problem solution or understanding. This research will (a) help in assessing the ability of soils to act as potential “sinks” for four major classes of antibiotics (fluoroquinolones, macrolides, sulfonamides and tetracyclines) and
(b) increase understanding of the mobility of these emerging contaminants in soils and subsurface environments as influenced by particle-bound and dissolved natural organic matter.
3. Project Objectives. The goal of this project is to determine the extent to which association of antibiotics with particle-bound and dissolved natural organic matter influences their mobility in soils and subsurface environments. The PIs intend to focus on representative antibiotics from four major classes: fluoroquinolones, macrolides, sulfonamides and tetracyclines. The selected antibiotics have been detected in wastewater influent and effluent in Wisconsin (Karthikeyan, unpublished data) and in streams throughout the U.S. (Kolpin et al., 2002). The specific objectives are to: (1) quantify the extent of sorption of these antibiotics to humic substances associated with hydrous iron and aluminum oxides and smectitic clays; and (2) investigate antibiotic association with dissolved organic matter and how such association facilitates antibiotic transport under unsaturated flow conditions.
4. Approach to achieving objectives. The PIs will employ ciprofloxacin, erythromycin, sulfamethazine and tetracycline as representative fluoroquinolone, macrolide, sulfonamide and tetracycline antibiotics. Natural organic matter differing in physical/ chemical characteristics (e.g., functional group composition, degree of aromaticity/ aliphaticity, molecular size) will be isolated from three Wisconsin soils present in wetland, coniferous forest and prairie settings. Particle-bound organic matter will be prepared by coating the humic substances extracted from the three soils onto common soil minerals, viz., hydrous iron and aluminum oxides and montmorillonite (smectitic clay). Dissolved organic matter (DOM) will be extracted as the water-soluble fraction of these soils. Batch sorption experiments employing radiolabeled antibiotics will be used to quantify the extent of sorption onto organo-mineral complexes. The PIs will measure antibiotic concentrations by both liquid scintillation counting (radioactivity) and high performance liquid chromatography (HPLC) to complete mass balances and determine the significance of transformation reactions in our experiments. Antibiotic association with DOM will be examined using negligible-depletion solid-phase micro-extraction coupled with HPLC. DOM-water distribution coefficients will be obtained for the antibiotics as a function of pH and background cationic composition (e.g., K+, Na+, Ca2+ and Mg2+). The molecular mechanisms responsible for sorptive interactions of antibiotics with DOM will be investigated using a combination of nuclear magnetic resonance and Fourier transform infrared spectroscopy. Unsaturated flow-through experiments will be conducted to examine the potential for DOM-facilitated transport of antibiotics in subsurface environments. Column effluent will be collected as a function of time, and the antibiotic breakthrough curves in the absence and presence of DOM will be obtained.
5. Users of project findings. Potential users of the project findings include environmental regulatory agencies, the regulated community, consultants and the environmental research community.