Microbially Mediated Abiotic Transformation of the Antimicrobial Agent Sulfamethoxazole under Iron-Reducing Soil Conditions

• Published in: Environmental science & technology Vol. 45; no. 11; pp. 4793 - 4801
• Main Authors: Mohatt, Jessica L, Hu, Lanhua, Finneran, Kevin T, Strathmann, Timothy J
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 01-06-2011
• Subjects: Agronomy. Soil science and plant productions; Anti-Infective Agents - chemistry; Anti-Infective Agents - metabolism; Antimicrobial agents; Applied sciences; Biodegradation, Environmental; Biogeochemistry; Biological and medical sciences; Biological and physicochemical properties of pollutants. Interaction in the soil; Biotransformation; Earth sciences; Earth, ocean, space; Electrons; Engineering and environment geology. Geothermics; Environmental Processes; Exact sciences and technology; Fundamental and applied biological sciences. Psychology; Iron; Iron Compounds - chemistry; Iron Compounds - metabolism; Livestock; Manures; Oxidation-Reduction; Pollution; Pollution, environment geology; Soil and sediments pollution; Soil and water pollution; Soil Microbiology; Soil Pollutants - chemistry; Soil Pollutants - metabolism; Soil science; Soils; Sorption; Sulfamethoxazole - chemistry; Sulfamethoxazole - metabolism; Drug; Microbial activity; Pollutant behavior; agricultural waste; Agricultural soil; Chemical degradation; Farmyard manure; Veterinary medicine; Soil pollution; beneficiation; Antimicrobial agent; sustainable development; Sulfamethoxazole; Selfpurification; Sulfonamides; Waste reuse; Micropollutant; Antiinfectious; organic compounds; Animal waste; waste management
• ISSN: 0013-936X; 1520-5851
• DOI: 10.1021/es200413g

Large quantities of antimicrobial agents used in livestock production are released to soils by land application of manure, but only limited information is available on mechanisms that contribute to antimicrobial fate in soils under variable biogeochemical conditions. Dissipation of the sulfonamide antimicrobial sulfamethoxazole was examined in soil microcosms incubated under different terminal electron-accepting conditions (aerobic, nitrate-reducing, Fe(III)-reducing, and sulfate-reducing). Somewhat unexpectedly, sulfamethoxazole dissipation was fastest under Fe(III)-reducing conditions, with concentrations decreasing by >95% within 1 day. The rapid transformation was attributed to abiotic reactions between sulfamethoxazole and Fe(II) generated by microbial reduction of Fe(III) soil minerals. Separate experiments demonstrated that sulfamethoxazole was abiotically transformed in Fe(II)-amended aqueous suspensions of goethite (α-FeOOH(s)), and observed rate constants varied with the extent of Fe(II) sorption to goethite. Sulfamethoxazole transformation is initiated by a 1-electron reductive cleavage of the N–O bond in the isoxazole ring substituent, and observed products are consistent with Fe(II)-mediated reduction and isomerization processes. These findings reveal potentially important, but previously unrecognized, pathways that may contribute to the fate of sulfamethoxazole and related chemicals in reducing soil environments.