Sorption, degradation, and transport of sulfamethazine in soils and manure-amended soils

Agricultural fields, surface waters and ground water can be contaminated with antibiotics through the application of antibiotic-contaminated swine manure. One of the more common antibiotics used for the swine industry is sulfamethazine (SMZ). The focus of this dissertation is to investigate the fate and transport of SMZ in soils in the presence of manure when applied to the fields. Sorption coefficients of SMZ for five local soils from Iowa with organic carbon (OC) contents ranging from 0.1 % to 3.8 % and solution pHs ranging from 5.5 to 9 were determined using batch sorption experiments. Sorption data fitted well to a linear sorption model but not to a non-linear Freundlich model. The linear sorption coefficients (Kd) were found to decrease with an increase in soil-solution pH. In addition, the Kd values were found to increase with an increase in % OC of soil at a given pH. At pH 5.5, Kd values were 0.58 L kg−1 and 3.9 L kg−1 for soils with 0.1 % OC and 3.8 % OC, respectively. Hydrophobic sorption was probably involved for pH \u3c 7.4 due to the unionized form of SMZ while some surface sorption was probably involved for pH \u3e 7.4 due to the ionized form of SMZ. A mechanistic model and a linear regression model incorporating soil properties and fractions of ionized SMZ were developed and found to estimate Kd values of other studies. Inhibitory effects of SMZ on anaerobic microbial respiration were observed at SMZ concentration of 50mg kg−1 while inhibition of aerobic microbial respiration was observed at between 50 and 100mg kg−1. The availability-adjusted first-order model but not simple first-order kinetics was found to fit the data well. Half-lives of SMZ ranged from 1.2 to 6.6 days and 2.3 to 15.1 days under aerobic and anaerobic conditions, respectively. The fate of 14C-SMZ in soil showed that 70 to 91 % of 14C-SMZ was bound to soils. Only 0.1 to 1.5 % of 14C-SMZ was completely mineralized to 14CO2 with the highest mineralization under aerobic conditions. The metabolites accounted for 5 to 10 % of SMZ and were found to be N4-acetylsulfamethazine and desamino sulfamethazine. Leaching of SMZ from soils and from manure-amended soils were investigated using topsoil mixed with SMZ or with SMZ−contaminated manure to a concentration of 7.25 mg kg−1 soil. The first simulated rainfall event applied to soil cores at 1, 4 and 7 days after the application of SMZ was followed by a second rain event, three days after the first rain event. Concentrations of SMZ in leachate were found to be the highest for first day after rainfall with concentration of 432 ± 167 μg L−1. Concentrations of SMZ in the leachate decreased with longer time duration between application of SMZ and the first rain event. The results showed that manure in the soils did not impact the leaching of SMZ and that colloid-facilitated transport of SMZ was unlikely. This study suggested that SMZ is expected to leach from manure-amended soils or manure even though SMZ may be degraded or bound to the soils

Fate and effect of antibiotics in beef and dairy manure during static and turned composting

Manure composting has general benefits for production of soil amendment, but the effects of composting on antibiotic persistence and effects of antibiotics on the composting process are not well-characterized, especially for antibiotics commonly used in dairy cattle. This study provides a comprehensive, head-to-head, replicated comparison of the effect of static and turned composting on typical antibiotics used in beef and dairy cattle in their actual excreted form and corresponding influence on composting efficacy. Manure from steers (with or without chlortetracycline, sulfamethazine, and tylosin feeding) and dairy cows (with or without pirlimycin and cephapirin administration) were composted at small scale (wet mass: 20-22 kg) in triplicate under static and turned conditions adapted to represent US Food and Drug Administration guidelines. Thermophilic temperature (>55°C) was attained and maintained for 3 d in all composts, with no measureable effect of compost method on the pattern, rate, or extent of disappearance of the antibiotics examined, except tylosin. Disappearance of all antibiotics, except pirlimycin, followed bi-phasic first-order kinetics. However, individual antibiotics displayed different fate patterns in response to the treatments. Reduction in concentration of chlortetracycline (71-84%) and tetracycline (66-72%) was substantial, while near-complete removal of sulfamethazine (97-98%) and pirlimycin (100%) was achieved. Tylosin removal during composting was relatively poor. Both static and turned composting were generally effective for reducing most beef and dairy antibiotic residuals excreted in manure, with no apparent negative impact of antibiotics on the composting process, but with some antibiotics apparently more recalcitrant than others

Sorption and Photodegradation Processes Govern Distribution and Fate of Sulfamethazine in Freshwater−Sediment Microcosms

The antibiotic sulfamethazine can be transported from manured fields to surface water bodies. We investigated the degradation and fate of sulfamethazine in pond water using 14C-phenyl-sulfamethazine in small pond water microcosms containing intact sediment and pond water. We found a 2.7-day half-life in pond water and 4.2-day half-life when sulfamethazine was added to the water (5 mg L–1 initial concentration) with swine manure diluted to simulate runoff. Sulfamethazine dissipated exponentially from the water column, with the majority of loss occurring via movement into the sediment phase. Extractable sulfamethazine in sediment accounted for 1.9–6.1% of the applied antibiotic within 14 days and then declined thereafter. Sulfamethazine was transformed mainly into nonextractable sediment-bound residue (40–60% of applied radioactivity) and smaller amounts of photoproducts. Biodegradation, as indicated by metabolite formation and 14CO2 evolution, was less significant than photodegradation. Two photoproducts accounted for 15–30% of radioactivity in the water column at the end of the 63-day study; the photoproducts were the major degradates in the aqueous and sediment phases. Other unidentified metabolites individually accounted for \u3c7% of radioactivity in the water or sediment. Less than 3% of applied radioactivity was mineralized to 14CO2. Manure input significantly increased sorption and binding of sulfamethazine residues to the sediment. These results show concurrent processes of photodegradation and sorption to sediment control aqueous concentrations and establish that sediment is a sink for sulfamethazine and sulfamethazine-related residues. Accumulation of the photoproducts and sulfamethazine in sediment may have important implications for benthic organisms

Sorption, degradation, and transport of sulfamethazine in soils and manure-amended soils

Agricultural fields, surface waters and ground water can be contaminated with antibiotics through the application of antibiotic-contaminated swine manure. One of the more common antibiotics used for the swine industry is sulfamethazine (SMZ). The focus of this dissertation is to investigate the fate and transport of SMZ in soils in the presence of manure when applied to the fields. Sorption coefficients of SMZ for five local soils from Iowa with organic carbon (OC) contents ranging from 0.1 % to 3.8 % and solution pHs ranging from 5.5 to 9 were determined using batch sorption experiments. Sorption data fitted well to a linear sorption model but not to a non-linear Freundlich model. The linear sorption coefficients (Kd) were found to decrease with an increase in soil-solution pH. In addition, the Kd values were found to increase with an increase in % OC of soil at a given pH. At pH 5.5, Kd values were 0.58 L kg−1 and 3.9 L kg−1 for soils with 0.1 % OC and 3.8 % OC, respectively. Hydrophobic sorption was probably involved for pH 7.4 due to the ionized form of SMZ. A mechanistic model and a linear regression model incorporating soil properties and fractions of ionized SMZ were developed and found to estimate Kd values of other studies. Inhibitory effects of SMZ on anaerobic microbial respiration were observed at SMZ concentration of 50mg kg−1 while inhibition of aerobic microbial respiration was observed at between 50 and 100mg kg−1. The availability-adjusted first-order model but not simple first-order kinetics was found to fit the data well. Half-lives of SMZ ranged from 1.2 to 6.6 days and 2.3 to 15.1 days under aerobic and anaerobic conditions, respectively. The fate of 14C-SMZ in soil showed that 70 to 91 % of 14C-SMZ was bound to soils. Only 0.1 to 1.5 % of 14C-SMZ was completely mineralized to 14CO2 with the highest mineralization under aerobic conditions. The metabolites accounted for 5 to 10 % of SMZ and were found to be N4-acetylsulfamethazine and desamino sulfamethazine. Leaching of SMZ from soils and from manure-amended soils were investigated using topsoil mixed with SMZ or with SMZ−contaminated manure to a concentration of 7.25 mg kg−1 soil. The first simulated rainfall event applied to soil cores at 1, 4 and 7 days after the application of SMZ was followed by a second rain event, three days after the first rain event. Concentrations of SMZ in leachate were found to be the highest for first day after rainfall with concentration of 432 ± 167 μg L−1. Concentrations of SMZ in the leachate decreased with longer time duration between application of SMZ and the first rain event. The results showed that manure in the soils did not impact the leaching of SMZ and that colloid-facilitated transport of SMZ was unlikely. This study suggested that SMZ is expected to leach from manure-amended soils or manure even though SMZ may be degraded or bound to the soils.</p

The influence of sulfathiazole on the macroalgae Ulva lactuca

Sulfonamides (SA) are a class of antibiotics routinely found in environmental matrices and therefore their role as contaminants should be investigated in non-target organisms. With this purpose the present experimental work has evaluated the exposure of the chlorophycean Ulva lactuca L. to sulfathiazole (STZ), a SA drug commonly used in aquaculture, at two concentrations representing prophylactic (25 lgmL 1) and therapeutic (50 lgmL 1) administrations. Results showed that STZ exhibits high stability in seawater with only 18% degradation over the 5 d assay at both dosages tested. Also, macroalgae demonstrated an efficient uptake capacity with constant internal concentrations after 24 h regardless of the external solutions and thus should be considered as a bioindicator species in risk assessment. Both STZ concentrations induced a slight inhibition of the macroalgae growth after 96 h.This work was funded by FEDER through the Operational Program for Competitiveness Factors – COMPETE and by FCT – Portuguese Foundation for Science and Technology under the Grant attributed to Sara Leston (SFRH/BPD/91828/2012) and through the Project PTDC/AGR-ALI/122119/2010