Facilitated Transport of Antibiotics by Biochar Under Rainfall Simulations

Andrea J Funk, Purdue University

Abstract

Antibiotic treatments in livestock operations are widely used in order to maintain a healthy herd and a healthy environment for livestock. From an agronomic perspective, the spreading of manure onto agricultural fields is beneficial to the soil as a renewable source of fertilizer by increasing organic matter and providing nutrient inputs for crops. However, the use of antibiotics can be excessive, resulting in manures containing residual antibiotics contaminating soils and waterways. Thus, there is a need to improve existing or develop new management practices to minimize the losses of antibiotics from manure entering waterways and groundwater. Biochar is a carbon-rich material produced from the oxygen-free pyrolysis of biomass. Generally, biochars have high surface area and sorb organic compounds and trace metals; thus, it is reasonable to hypothesize that biochars sorb antibiotics. The main goal of this research was to investigate if incorporated biochar to soil facilitates the transport of antibiotics under simulated rainstorm events. The specific objectives were to investigate the losses of surface-applied antibiotics to soils with different (1) application rates of biochar and rainfall intensities, and (2) if the losses were antibiotic type-dependent. The antibiotics, lincomycin, monensin, and tylosin were chosen because of their different chemical properties and to represent a wide range of family of antibiotics used in livestock in the U.S. Midwest. Softwoodderived biochar, at rates 0, 1, and 2% (w/w), was incorporated into a mollisol, followed by the spraying of a mix solution of antibiotics (target concentration of 1000 μg L-1 per antibiotic) on the soil surface to mimic surface-applied manure practices. Simulated rainfall consisted of a 45- min rainstorm event of either 50 or 100 mm hr-1 to represent “normal” and “worst-case scenario” rainstorm events in the U.S. Midwest, respectively. Surface runoff and drainage samples were collected to quantify the losses of antibiotics associated with the biochar, sediment, and water lost during the rainstorm events. Runoff losses of biochar accounted for < 0.3% of total applied to the soil. Of the total antibiotics applied, <0.05% was accounted in the biochar (loss via surface runoff), indicating that antibiotic loss via facilitated transport by biochar was minimal. Of the three antibiotics used in this study, surface losses associated with biochar follow the order tylosin > monensin > lincomycin. Drainage antibiotic losses were as follows: monensin > lincomycin > tylosin; conversely, antibiotic losses from water runoff were of the order lincomycin > monensin > tylosin. Lastly, antibiotic losses in sediment were as follows: tylosin > lincomycin > monensin. Tylosin had the lowest recoveries in drainage and water runoff due to its strong adsorption capabilities to soil. Monensin had the highest losses in drainage but the lowest in sediment, instead partitioning to soil and biochar in the boxes. Lincomycin had the highest recovery in water runoff but the lowest recoveries in soil and biochar from boxes, explained by its hydrophilic properties making it mobile in the soil. The 100 mm hr-1 rainfall intensity increased the losses of lincomycin by 30% and of monensin by 50%, relative to the 50 mm hr-1 ; however, tylosin losses were not affected by the rainfall intensity.

Degree

M.Sc.

Advisors

Johnston, Purdue University.

Subject Area

Agriculture|Agronomy|Animal sciences|Hydrologic sciences|Meteorology|Microbiology|Pharmaceutical sciences|Water Resources Management

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