Sorption and mobility of metronidazole, olaquindox, oxytetracycline and tylosin in soil

Dissipation of Three Veterinary Antimicrobials in Beef Cattle Feedlot Manure Stockpiled over Winter

Dissipation of veterinary antimicrobials is known to occur during aerated windrow composting of beef cattle manure. However, it is unclear if a similar dissipation occurs during stockpiling. Chlortetracycline, tylosin, and sulfamethazine are three of the most commonly used veterinary antimicrobials in beef cattle production in western Canada. Their dissipation in stockpiled manure was investigated over 140 d during winter in Alberta, Canada. Beef cattle housed in pens were administered 44 mg of chlortetracycline kg feed (dry weight), 44 mg of chlortetracycline + 44 mg sulfamethazine kg feed, 11 mg of tylosin kg feed, or feed without antimicrobials (control). Manure samples were extracted using pressurized liquid extraction, and the extracts were analyzed for chlortetracycline, sulfamethazine, and tylosin by LC-MS-MS. Dissipation of all three antimicrobials in the manure was explained by exponential decay kinetics. Times for 50% dissipation (DT) were 1.8 ± 0.1 d for chlortetracycline alone or 6.0 ± 0.8 d when mixed with sulfamethazine, 20.8 ± 3.8 d for sulfamethazine, and 4.7 ± 1.2 d for tylosin. After 77 d, <1% of initial chlortetracycline and <2% of sulfamethazine remained. Tylosin residues were more variable, decreasing to approximately 12% of initial levels after 28 d, with 20% present after 77 d and 13% after 140 d. Temperatures within stockpiles reached maximum values within 6 d of establishment and varied with location (bottom, 62.5°C; middle, 63.8°C; and top, 42.9°C). Antimicrobials in the manure did not inhibit microbial activity, as indicated by temperature and mass losses of carbon (C) and nitrogen (N). The C/N ratio in the manure decreased over the stockpiling period, indicating decomposition of manure to a more stable state. Dissipation of excreted residues with DT values 1.8 to 20.8 d showed that stockpiling can be as effective as windrow composting in mitigating the transfer of these three veterinary antimicrobials into the environment during land application of processed manure.

Potential of Biological Processes to Eliminate Antibiotics in Livestock Manure: An Overview

Simple Summary

Beside their use to treat infections, antibiotics are used excessively as growth promoting factors in livestock industry. Animals discharge in their feces and urine between 70%–90% of the antibiotic administrated unchanged or in active metabolites. Because livestock manure is re-applied to land as a fertilizer, concerns are growing over spread of antibiotics in water and soil. Development of antibiotic resistant bacteria is a major risk. This paper reviewed the potential of anaerobic digestion to degrade antibiotics in livestock manure. Anaerobic digestion can degrade manure-laden antibiotic to various extents depending on the concentration and class of antibiotic, bioreactor operating conditions, type of feedstock and inoculum sources.

Abstract

Degrading antibiotics discharged in the livestock manure in a well-controlled bioprocess contributes to a more sustainable and environment-friendly livestock breeding. Although most antibiotics remain stable during manure storage, anaerobic digestion can degrade and remove them to various extents depending on the concentration and class of antibiotic, bioreactor operating conditions, type of feedstock and inoculum sources. Generally, antibiotics are degraded during composting > anaerobic digestion > manure storage > soil. Manure matrix variation influences extraction, quantification, and degradation of antibiotics, but it has not been well investigated. Fractioning of manure-laden antibiotics into liquid and solid phases and its effects on their anaerobic degradation and the contribution of abiotic (physical and chemical) versus biotic degradation mechanisms need to be quantified for various manures, antibiotics types, reactor designs and temperature of operations. More research is required to determine the kinetics of antibiotics’ metabolites degradation during anaerobic digestion. Further investigations are required to assess the degradation of antibiotics during psychrophilic anaerobic digestion.

Sorption/desorption behavior of oxytetracycline and sulfachloropyridazine in the soil water surfactant system

Sorption/desorption of antibiotics, oxytetracycline (OTC), and sulfachloropyridazine (SCP) was investigated in the presence of a nonionic surfactant Brij35. Batch sorption experiments indicated that Freundlich equation fits sorption isotherms well for OTC. The sorption coefficients, KF, values were computed as 23.55 mL g(−1) in the absence of Brij35 and 25.46 mL g(−1) in the presence of Brij35 in the monomer form (below critical micelle concentration CMC, of 74 mg L(−1)). However, the KF values reduced to 12.76 mL g(−1) in the presence of Brij35 at 2.5 g L(−1). Therefore, irrigation with surfactant-rich water may increase the leaching potential of OTC. In the case of SCP, the KF value, in the absence of Brij35, was 19.95 mL g(−1). As a result of increasing the concentration of Brij35 to 0.25 g L(−1) (about 2.5 CMC), KF values first increased and reached a maximum value of 95.49 mL g(−1) and then reduced to 66.06 mL g(−1), at surfactant concentration of 5 g L(−1). Unlike OTC, the presence of surfactant in irrigation water is likely to decrease SCP leaching. In the case of OTC, hysteresis was found at Brij35 concentrations below CMC. However, OTC desorbed readily from soil (no hysteresis) at Brij35 concentrations above CMC. In the case of SCP, no hysteresis was found in the presence of the surfactant, both below and above CMC. Further, the obtained values of the efficiency coefficient (E), reveals that Brij35 had the potential to release more OTC from the soil (E > 1) as compared to SCP (E < 1). From these results, it can be concluded that regular use of manure on agricultural soils, especially in regions where poor quality irrigation water is used, can increase OTC contamination of water resources.

Occurrence, distribution and bioaccumulation of antibiotics in the Liao River Basin in China

The occurrence and distribution of 19 antibiotics including ten sulfonamides, four quinolones, three tetracyclines and two macrolides in water, sediment, and biota samples from the Liao River Basin, China were investigated in the present study. The samples were collected in May 2012, and laboratory analyses revealed that antibiotics were widely distributed in the Liao River Basin. Macrolides made up the majority of antibiotics in the water ranging from not detected (ND) to 3162.22 ng L(-1), while tetracyclines and macrolides were the predominant antibiotics in the sediments, ranging from ND to 404.82 μg kg(-1) (mean 32.11 μg kg(-1) dw) and ND to 375.13 (mean 32.77 μg kg(-1) dw), with detection frequencies of 37.3% and 38.1%, respectively. In biological samples, quinolones were the most frequently detected antibiotics (57.1-100%), with concentrations ranging from 286.6-1655.3 μg kg(-1). The highest bioaccumulation factor (BAF) of 45407 L kg(-1) was found for enrofloxacin. The phase distribution calculation showed that tetracyclines were the most strongly adsorbed antibiotics in the sediment, with the highest pseudo-partitioning coefficient values, ranging from 1299 to 1499 L kg(-1). The geographical differences of antibiotic concentrations were largely due to anthropogenic activities and the sewage discharges from the local cities along the rivers.

Sorption of selected veterinary antibiotics onto dairy farming soils of contrasting nature

The sorption potential for three sulfonamides (SAs), sulfamethoxazole (SMO), sulfachloropyridazine (SCP) and sulfamethazine (SM) and a macrolide, tylosin tartrate (TT) was assessed on six New Zealand dairy farming soils of contrasting physico-chemical properties. Kinetics studies showed that the sorption was rapid in the first few hours of the contact time (0-2h for SA and 0-4h for TT) and thereafter apparent equilibrium was achieved. Batch sorption isotherm data revealed that the degree of isotherm linearity (N) for SCP and SM varied between 0.50 and 1.08 in the six soils. Isotherms of both TT and SMO were mostly non-linear with the degree of non-linearity for TT (N=0.38-0.71) being greater than for SMO (0.42-0.75) in all soils except Manawatu (TT) and Te Kowhai (SMO) where a linear pattern was observed. Concentration-dependent effective distribution coefficient (Kd(eff)) values for the SMO, SCP and SM antibiotics in the soils ranged from 0.85 to 16.35 L kg(-1), while that for TT was 1.6 to 1,042 L kg(-1). The sorption affinity for all soils followed an order: TT>SCP>SM>SMO. Remarkable high sorption for tylosin in Matawhero soil as compared to other soils was attributed to the presence of oxygen containing acidic polar functional groups as evident in the FT-IR spectra of the soil. Furthermore, it was hypothesised that sorption of TT onto soils was mostly driven by metal oxide-surface mediated transformations whereas for sulfonamides it was primarily due to hydrophobic interactions.

The environmental release and fate of antibiotics

Antibiotics have been used as medical remedies for over 50 years and have recently emerged as new pollutants in the environment. This review encompasses the fate of several antibiotics in the environment, including sulfonamides, nitrofurans, terfenadines, cephalosporins and cyclosporins. It investigates the cycle of transfer from humans and animals including their metabolic transformation. The results show that antibiotic metabolites are of considerable persistence and are localized to ground-water and drinking water supplies. Furthermore, the results also show that several phases of the cycle of antibiotics in the environment are not well understood, such as how low concentrations of antibiotic metabolites in the diet affect humans and animals. This review also shows that improved wastewater decontamination processes are remediating factors for these emerging pollutants. The results obtained here may help legislators and authorities in understanding the fate and transformation of antibiotics in the environment.

The influences of pH and ionic strength on the sorption of tylosin on goethite

As one of the widely used antibiotics in the world, the environmental risks of tylosin (TYL) received more and more attention. In order to assess its environmental fate and ecological effects accurately, it is necessary to understand the sorption properties of TYL on the soils/sediments. The sorption of TYL on goethite at different pH and ionic strength conditions were measured through a series of batch experiments and the sorption data of TYL were fitted by Freundlich and dual-mode sorption models. It was obvious that sorption was strongly dependent on pH and ionic strength. Sorption capacity of TYL increased as the pH increased and ionic strength decreased. The pH and ionic strength-dependent trends might be related with complexation between cationic/neutral TYL species and goethite. The sorption affinity of TYL on goethite decreased as ionic strength increased, which only occurred at higher TYL concentrations, suggested that inner complex might have dominated process at low concentrations and outer complex might occur at higher concentrations of TYL. Spectroscopic evidence indicated that tricarbonylamide and hydroxyl functional groups of TYL might be accounted for the sorption on mineral surfaces. The experimental data of TYL sorption could be fitted by surface complexation model (FITEQL), indicating that ≡FeOH with TYL interaction could be reasonably represented as a complex formation of a monoacid with discrete sites on goethite. The sorption mechanism of TYL might be related with surface complexation, electrostatic repulsion, and H-bounding on goethite. It should be noticed that the heterogeneous of sorption affinity of TYL on goethite at various environment to assess its environment risk.

Assessing antibiotic sorption in soil: a literature review and new case studies on sulfonamides and macrolides

The increased use of veterinary antibiotics in modern agriculture for therapeutic uses and growth promotion has raised concern regarding the environmental impacts of antibiotic residues in soil and water. The mobility and transport of antibiotics in the environment depends on their sorption behavior, which is typically predicted by extrapolating from an experimentally determined soil-water distribution coefficient (K_d). Accurate determination of K_d values is important in order to better predict the environmental fate of antibiotics. In this paper, we examine different analytical approaches in assessing K_d of two major classes of veterinary antibiotics (sulfonamides and macrolides) and compare the existing literature data with experimental data obtained in our laboratory. While environmental parameters such as soil pH and organic matter content are the most significant factors that affect the sorption of antibiotics in soil, it is important to consider the concentrations used, the analytical method employed, and the transformations that can occur when determining K_d values. Application of solid phase extraction and liquid chromatography/mass spectrometry can facilitate accurate determination of K_d at environmentally relevant concentrations. Because the bioavailability of antibiotics in soil depends on their sorption behavior, it is important to examine current practices in assessing their mobility in soil.

Occurrence and sources of antibiotics and their metabolites in river water, WWTPs, and swine wastewater in Jiulongjiang River basin, south China

In this study, the occurrence and sources of five cataloged antibiotics and metabolites were studied in Jiulongjiang River basin, south China. Nineteen antibiotics and 13 metabolites were detected in water samples from 16 river sampling sites, wastewater from 5 swine-raising facilities, and effluent from 5 wastewater treatment plants (WWTPs). The results showed that 12 antibiotics and 6 metabolites were detected in river water samples. Sulfonamides (SAs) and their metabolites were detected at high concentrations (8.59-158.94 ng/L). Tetracyclines (TCs) and their metabolites were frequently detected in swine wastewater, and the maximum concentration was up to the level in milligram per liter. Macrolides (MLs) and β-lactams (β-Ls) were found in all WWTP effluent samples and some river samples, while they were never found in any of the swine wastewater samples. SAs and quinolones (QNs) were detected in all samples. Hierarchical cluster analysis of 16 surface water samples was applied to achieve the spatial distribution characteristics of antibiotics in the Jiulongjiang River. As a result, two categories were obviously obtained. Principal component analysis and redundancy analysis showed that TCs and SAs as well as their metabolites were the major antibiotics in Jiulongjiang River, and they mainly originated from swine wastewater, while the QNs, MLs, and β-Ls in the Jiulongjiang River came from WWTP effluent.

Pharmaceuticals and personal care products in the aquatic environment in China: a review

Pharmaceuticals and personal care products (PPCPs) have been detected as contaminants of emerging concern ubiquitously in the aquatic environment in China and worldwide. A clear picture of PPCP contamination in the Chinese aquatic environment is needed to gain insight for both research and regulatory needs (e.g. monitoring, control and management). The occurrence data of 112 PPCPs in waters and sediments in China has been reviewed. In most cases, the detected concentration of these PPCPs in waters and sediments were at ng/L and ng/g levels, which were lower than or comparable to those reported worldwide. A screening level risk assessment (SLERA) identified six priority PPCPs in surface waters, namely erythromycin, roxithromycin, diclofenac, ibuprofen, salicylic acid and sulfamethoxazole. The results of SLERA also revealed that the hot spots for PPCP pollution were those river waters affected by the megacities with high density of population, such as Beijing, Tianjin, Guangzhou and Shanghai. Limitations of current researches and implications for future research in China were discussed. Some regulatory issues were also addressed.

Sorption of tylosin on clay minerals

The equilibrium sorption of tylosin (TYL) on kaolinite and montmorillonite was measured at different solution pH using batch reactor systems. The results showed that all the sorption isotherms were nonlinear and that the nonlinearity decreased as the solution pH increased for a given clay. At a specific aqueous concentration, the single-point sorption distribution coefficient (KD) of TYL decreased rapidly as the solution pH increased. A speciation-dependent sorption model that accounted for the contributions of the cationic and neutral forms of TYL fit the data well, suggesting that the sorption may be dominated by both ion exchange and hydrophobic interactions. The isotherm data also fit well to a dual mode model that quantifies the contributions of a site-limiting Langmuir component (ion exchange) and a non-specific linear partitioning component (hydrophobic interactions). X-ray diffraction analyses revealed that the interlayers of montmorillonite were expanded due to the uptake of TYL. TYL molecules likely form a monolayer surface coverage.

Electrochemical degradation of the antibiotic metronidazole in aqueous solution by the Ti/SnO2-Sb-Ce anode

Metronidazole (MNZ) is an antibiotic pollutant with a high occurrence in the ambient medium. In this study, the anode material Ti/SnO2-Sb-Ce prepared in the lab was employed to investigate the feasibility of the electrochemical process to treat antibiotic in wastewater. The result showed that metronidazole could be effectively removed using Ti/SnO2-Sb-Ce. The degradation efficiency of 88% was obtained under the current density 1.6 mA cm(-2), pH = 5.6 (not adjusted), electrolyte (Na2SO4) concentration of 0.2 M for electrolysis 2 h. The removal percentage was higher by 17% compared with the control when the bare Ti was applied. Meanwhile, the energy consumption on Ti/SnO2-Sb-Ce was about one-seventh of that on Ti. The characterization of the material was conducted by the thermal field emission scanning electron microscope (FE-SEM), energy-dispersive X-ray spectrometer (EDS) and cyclic voltammetry (CV). The Ti/SnO2-Sb-Ce anode displayed compact, multi-porous morphology and good redox reversibility. The influencing factors such as current density, pH, concentration of Na2SO4, initial MNZ concentration were studied to obtain main factors and optimum conditions. In addition, a preliminary study on the mechanism of the electro-oxidation was carried out. The results demonstrate that chemisorbed oxygen has a dominant role in MNZ removal.

Sorption, Leaching, and Surface Runoff of Beef Cattle Veterinary Pharmaceuticals under Simulated Irrigated Pasture Conditions

The use of veterinary pharmaceuticals in beef cattle has led to concerns associated with the development of antibiotic resistance in bacteria and endocrine disruption in aquatic organisms. Despite the potential negative consequences, data on the transport and mitigation of pharmaceuticals in grazed watersheds with irrigated pasture are scarce. The objective of this study was to assess the transport of common beef cattle pharmaceuticals (oxytetracycline, chlortetracycline, and ivermectin) via surface runoff and leachate from manure amended to grass-vegetated soil boxes under irrigated pasture conditions. The transport of pharmaceuticals from animal manure in surface runoff and soil leachate was relatively low and appears to be limited by desorption and transport of pharmaceuticals entrained in the manure. In surface runoff, less than 4.2% of applied pharmaceuticals in manure (initial concentration: 0.2 mg kg of manure) was detected after 3 wk of irrigation. Concentrations of pharmaceuticals in surface runoff and leachate never exceeded 0.5 μg L. The major portion of pharmaceuticals (up to 99%) was retained in the manure or in the soil directly beneath the manure application site. Based on the minimal transport of oxytetracycline, chlortetracycline, and ivermectin, the risk of significant transport for these targeted beef cattle pharmaceuticals to surface water and groundwater from manure on irrigated pasture appears to be relatively low.

Effects of pH and metal ions on oxytetracycline sorption to maize-straw-derived biochar

Biochars produced from biomass residues have been recognized as effective sorbents to hydrophobic compounds, but knowledge on sorption of antibiotics to biochar and its mechanisms are still inadequate. Sorption of oxytetracycline (OTC) in aqueous solution to maize-straw-derived biochar, and the effect of pH and metal ions, was investigated in batch experiments, and the main sorption mechanisms were elucidated using FTIR and zeta potential measurements. The results showed that sorption of OTC on biochar was highly pH-dependant. The amount of sorbed OTC first increased and then decreased with increasing pH, and maximum sorption was achieved at pH 5.5. Cu(2+) enhanced the sorption of OTC, while Pb(2+) slightly reduced the sorption under acidic conditions. Other metal ions had no significant effect on the sorption of OTC to biochar. Surface complexation, through π-π interaction and metal bridging, was the most important sorption mechanism although cation exchange might have played a role.

Occurrence and partition of antibiotics in the liquid and solid phases of swine wastewater from concentrated animal feeding operations in Shandong Province, China

Swine wastewater represents an important pollution source of antibiotics in the environment; however, regional data about residual antibiotics in swine wastewater are very limited at present. This study investigated the concentrations of three classes of commonly used veterinary antibiotics, including five sulfonamides (SAs), three tetracyclines (TCs) and one macrolide (tiamulin, TIA), in swine wastewater collected from 21 concentrated animal feeding operation (CAFO) sites in Shandong Province, China. Both the liquid and solid (i.e., suspended solids) phases of swine wastewater were analyzed to determine the total concentration of each studied antibiotic. Results indicate that sulfamethazine had the highest median concentration (14.56 μg L(-1)), followed by oxytetracycline (OTC, 8.05 μg L(-1)) and chlortetracycline (CTC, 6.01 μg L(-1)). The maximum detected concentration reached up to 2.02 mg L(-1) (OTC) and the highest detection frequency was 95.1% (CTC). The median concentrations and detection frequencies of antibiotics in winter samples were generally higher than those in summer samples (except CTC). The log Kd values were in the range of 1.31-1.96 for SAs, 2.05-2.33 for TCs, and 1.54-1.58 for TIA in swine wastewater. More TCs (14-28%) preferred to partition in the solid phase than SAs (2-10%) and TIA (5-10%), indicating that the suspended solids of swine wastewater may not be ignored.

Tracking Change: A Look at the Ecological Footprint of Antibiotics and Antimicrobial Resistance

Among the class of pollutants considered as 'emerging contaminants', antibiotic compounds including drugs used in medical therapy, biocides and disinfectants merit special consideration because their bioactivity in the environment is the result of their functional design. Antibiotics can alter the structure and function of microbial communities in the receiving environment and facilitate the development and spread of resistance in critical species of bacteria including pathogens. Methanogenesis, nitrogen transformation and sulphate reduction are among the key ecosystem processes performed by bacteria in nature that can also be affected by the impacts of environmental contamination by antibiotics. Together, the effects of the development of resistance in bacteria involved in maintaining overall ecosystem health and the development of resistance in human, animal and fish pathogens, make serious contributions to the risks associated with environmental pollution by antibiotics. In this brief review, we discuss the multiple impacts on human and ecosystem health of environmental contamination by antibiotic compounds.

Effect of nonionic surfactant Brij 35 on the fate and transport of oxytetracycline antibiotic in soil

In many parts of the world, river water is used for irrigation. Treated, partially treated, and even untreated water from wastewater treatment plants is discharged directly into rivers, thereby degrading the quality of the water. Consequently, irrigation water may contain surfactants which may affect the fate and transport of chemicals such as pesticides and antibiotics in agricultural soils. A field lysimeter study was undertaken to investigate the effect of the nonionic surfactant, Brij 35, on the fate and transport of an antibiotic, Oxytetracycline, commonly used in cattle farms. Nine PVC lysimeters, 1.0 m long × 0.45 m diameter, were packed with a sandy soil to a bulk density of 1.35 Mg m(-3). Cattle manure, containing Oxytetracycline, was applied at the surface of the lysimeters at the recommended rate of 10 t/ha. Each of three aqueous Brij 35 solutions, 0, 0.5 and 5 g L(-1) (i.e., 'good,' 'poor' and 'very poor' quality irrigation water) were each applied to the lysimeters in triplicate. Over a 90 day period, soil and leachate samples were collected and analyzed. Batch experiment results showed that the presence of the nonionic surfactant Brij 35 significantly reduced the sorption coefficient of OTC from 23.55 mL g(-1) in the aqueous medium to 19.49, 12.49 and 14.53 in the presence of Brij 35 at concentrations of 0.25, 2.5 and 5 g L(-1), respectively. Lysimeter results indicted the significant downward movement of OTC at depths of 60 cm into soil profile and leachate in the presence of surfactant. Thus, the reuse of wastewater containing surfactants might enhance the mobility of contaminants and increase ground water pollution.

Sorption of sulfadiazine on Brazilian soils

Antimicrobials, among them sulfonamides are widely used in veterinary medicine and can contaminate the environment. The degree to which antimicrobials adsorb onto soil particles varies widely, as does the mobility of these drugs. Sulfadiazine (SDZ) was used to study the adsorption-desorption in Brazilian soil-water systems, using batch equilibrium experiments. Sorption of SDZ was carried out using four types of soils. Adsorption and desorption data were well fitted with Freundlich isotherms in log form (r>0.999) and (0.984<r<0.999), respectively. An adsorption-desorption hysteresis phenomenon was apparent in all soils ranging from 0.517 to 0.827. The experimental results indicate that the Freundlich sorption coefficient (K(F)) values for SDZ ranged from 0.45 to 2.6 μg(1-1/n)(cm(3))(1/n)g(-1).

A Review of the Use of Organic Amendments and the Risk to Human Health

Historically, organic amendments—organic wastes—have been the main source of plant nutrients, especially N. Their use allows better management of often-finite resources to counter changes in soils that result from essential practices for crop production. Organic amendments provide macro- and micronutrients, including carbon for the restoration of soil physical and chemical properties. Challenges from the use of organic amendments arise from the presence of heavy metals and the inability to control the transformations required to convert the organic forms of N and P into the minerals available to crops, and particularly to minimize the losses of these nutrients in forms that may present a threat to human health. Animal manure and sewage biosolids, the organic amendments in greatest abundance, contain components that can be hazardous to human health, other animals and plants. Pathogens pose an immediate threat. Antibiotics, other pharmaceuticals and naturally produced hormones may pose a threat if they increase the number of zoonotic disease organisms that are resistant to multiple antimicrobial drugs or interfere with reproductive processes. Some approaches aimed at limiting N losses (e.g. covered liquid or slurry storage, rapid incorporation into the soil, timing applications to minimize delay before plant uptake) also tend to favor survival of pathogens. Risks to human health, through the food chain and drinking water, from the pathogens, antibiotics and hormonal substances that may be present in organic amendments can be reduced by treatment before land application, such as in the case of sewage biosolids. Other sources, such as livestock and poultry manures, are largely managed by ensuring that they are applied at the rate, time and place most appropriate to the crops and soils. A more holistic approach to management is required as intensification of agriculture increases.

Environmental Risk Assessment of antimicrobials applied in veterinary medicine-A field study and laboratory approach

The fate and environmental risk of antimicrobial compounds of different groups of veterinary medicine pharmaceuticals (VMP's) have been compared. The aim was to demonstrate a correlation between the physical and chemical properties of active compounds and their metabolism in target animals, as well as their fate in the environment. In addition, the importance of techniques for manure management and agricultural practice and their influence on the fate of active compounds is discussed. The selected active compounds are shown to be susceptible to at least one environmental factor (sun, water, bacterial or fungal degradation) to which they are exposed during their life cycle, which contributes to its degradation. Degradation under a number of environmental factors has also to be considered as authentic information additional to that observed in the limited conditions in laboratory studies and in Environmental Risk Assessment calculations.

Prioritization of chemicals in the aquatic environment based on risk assessment: analytical, modeling and regulatory perspective

The extensive and intensive use of chemicals in our developed, highly technological society includes more than 100,000 chemical substances. Significant scientific evidence has lead to the recognition that their improper use and release may result in undesirable and harmful side-effects on both the human and ecosystem health. To cope with them, appropriate risk assessment processes and related prioritization schemes have been developed in order to provide the necessary scientific support for regulatory procedures. In the present paper, two of the elements that constitute the core of risk assessment, namely occurrence and hazard effects, have been discussed. Recent advances in analytical chemistry (sample pre-treatment and instrumental equipment, etc.) have allowed for more comprehensive monitoring of environmental pollution reaching limits of detection up to sub ng L(-1). Alternative to analytical measurements, occurrence models can provide risk managers with a very interesting approach for estimating environmental concentrations from real or hypothetical scenarios. The most representative prioritization schemes used for issuing lists of concerning chemicals have also been examined and put in the context of existing environmental policies for protection strategies and regulations. Finally, new challenges in the field of risk-assessment have been outlined, including those posed by new materials (i.e., nanomaterials), transformation products, multi-chemical exposure, or extension of the risk assessment process to the whole ecosystem.

Quantitatively modeling soil-water distribution coefficients of three antibiotics using soil physicochemical properties

Using 14 parameters featuring soil physicochemical properties and the partial least squares (PLSs) regression method, three quantitative models were respectively developed for the soil-water distribution coefficients (logK(d)) of oxytetracycline (OTC), sulfamethazine (SMZ) and norfloxacin (NOR) in 23 Chinese natural soil samples from cultivated lands in 19 provinces of China. The cross-validated correlation coefficients (Q(cum)(2)) of three models are 0.866, 0.765 and 0.868, and the standard deviations (SDs) are 0.16, 0.21 and 0.15 respectively. The high Q(cum)(2) and low SD values indicate that three models have high robustness and precise predictability. Six parameters including pH, clay content, free Fe oxides (DCB-Fe), free Al oxides (DCB-Al), Ca content and Al content are greatly significant in the OTC model, three ones including pH, clay content and DCB-Fe are greatly significant in the SMZ model, and five ones including pH, clay content, DCB-Fe, Ca content and organic matter (OM) are greatly significant in the NOR model. The high VIP values of pH (1.17-1.24), clay content (0.81-1.10) and DCB-Fe (0.90-0.99) show that the three sorts of soil physicochemical properties play dominant roles in governing the partition balance between soil and water of three antibiotics.

Uptake of oxytetracycline, sulfamethoxazole and ketoconazole from fertilised soils by plants

This study was performed to investigate the potential for a set of two antibiotics and one antifungal compound to be taken up from the soil by plants. Plants are used for animal or human consumption, and so the measured concentrations in the plant material will be used to model potential human exposure to these compounds. The uptake by two types of plants (grass and watercress) from two types of soil was studied. The compounds used for these experiments were sulfamethoxazole, oxytetracycline and ketoconazole at concentrations of 5 and 10 mg kg(-1) in the soil. The compounds of interest were extracted out of the plant matrix by applying accelerated solvent extraction. Analyses were carried out by a LC-MS/MS. From the results, it was concluded that the plant materials used for this study were able to take up sulfamethoxazole and ketoconazole when the soil was contaminated with these compounds at a concentration ranging from 5 to 10 mg kg(-1). Sulfamethoxazole was detected in all samples, at levels ranging from 7 to 21 µ kg(-1) for grass and 4 to 7.5 µ kg(-1) for watercress. For ketoconazole, the results showed low absorption. Oxytetracycline was not detected in any sample. A partition-limited model approach was applied for the comparison of experimental and estimated data, and the relationship between physicochemical properties of the compounds and plant uptake was highlighted.

Sorption of tetracyclines onto natural soils: data analysis and prediction

Residues of tetracyclines reach soils as a result of animal waste application. Sorption is a key process in transport, fate, and effects of contaminants in the environment. In this work, we have attempted to predict the sorption of four widely used tetracyclines (oxytetracycline, tetracycline, chlortetracycline, and doxycycline) from soil physicochemical properties. Batch sorption experiments were performed on 15 natural soils with a broad range of physicochemical properties, and the data were fitted to several isotherm models. Multivariate analysis methods were conducted to identify the main factors affecting the sorption distribution coefficients (K (d)) of the tetracyclines at two aqueous concentration levels (100 and 400 μg L(-1)). All four tetracycline sorption isotherms in alkaline and acidic soils were well described by the Freundlich and Langmuir equation, respectively. At intermediate soil pH (from 5.3 to 7), oxytetracycline and tetracycline exhibited Freundlich behavior, whereas chlortetracycline and doxycycline followed a Langmuir model. Two partial least squares (PLS) models were developed. The first one uses five soil descriptors as input variables; the second uses, pH, cation exchange capacity (CEC), and log K (d,OTC). Both models satisfactorily predicted distribution coefficients within a factor of 1.5. Sorption of tetracyclines in soil is governed by several factors, in the following order of importance: solution speciation, CEC (dominant at acidic-neutral soil pH), transition metal content, and texture. The PLS models indicated that tetracycline sorption can be predicted using a minimal set of soil descriptors including oxytetracycline sorption data.

Sorption and desorption of salinomycin sodium in clay, loamy sand, and sandy soils

Salinomycin sodium (BIO-COX) is polyether ionophore, commonly used in the poultry industries for the prevention of coccidial infections and promotion of growth. Salinomycin sodium (SAL-Na) is very toxic, and may be fatal, if swallowed, inhaled, or absorbed through the skin than many other antibiotics, thus evaluating their fate in the soil environment is of importance. Sorption of SAL-Na was measured in clay, loamy sand, and sandy soil at different pH 4, 7, and 9, and desorption with phosphate buffer (pH 7) using batch equilibration technique. SAL-Na was sorbed by all the soils studied, the sorption of SAL-Na by the sandy soil increased as the pH decreased, while the sorption of salinomycin in clay and loamy sand soil increased as the pH increased. Desorption of salinomycin from the soil with phosphate buffer (pH 7) over the 24 h period was 80-95% of the amount added. The similar trend was observed in desorption with pH 4, 7 and at different concentrations and slight less desorption was observed in pH 9. When compared to clay and loamy sand soil, sandy soil was recorded maximum (95%) desorption.

Sorption of tetracycline on organo-montmorillonites

Tetracycline (TC) is a veterinary antibiotic that is frequently detected as pollutant in the environment. Powerful adsorbents are required for removing TC. The present paper compares the TC adsorption capacity of Na-montmorillonite (Na-mont) with six organo-montmorillonites (organo-monts). Three quaternary ammonium cations (QACs) with different alkyl-chain lengths were used as modifiers. Powder X-ray diffraction indicated that the d(001) values of organo-monts increased with increasing the QACs loading and alkyl-chain length. The CECs of the organo-monts were substantially lower than that of Na-mont and decreased with QACs chain length and increased loading. The modeling of the adsorption kinetics revealed that the processes of TC adsorption on the tested samples could be well fitted by the pseudo-second-order equation. The maximum adsorption capacities of TC on the organo-monts (1000-2000mmol/kg) were considerably higher than that on Na-mont (769mmol/kg). Both the Langmuir and Freundlich model could fit the adsorption isotherms. The TC adsorption to the organo-monts increase significantly with decreasing the pH below 5.5 because of the electrostatic interaction, and a high QACs loading performed better than a low loading at around pH 3.

Effect of biochar amendment on tylosin adsorption-desorption and transport in two different soils

The role of biochar as a soil amendment on the adsorption-desorption and transport of tylosin, a macrolide class of veterinary antibiotic, is little known. In this study, batch and column experiments were conducted to investigate the adsorption kinetics and transport of tylosin in forest and agricultural corn field soils amended with hardwood and softwood biochars. Tylosin adsorption was rapid at initial stages, followed by slow and continued adsorption. Amounts of adsorption increased as the biochar amendment rate increased from 1 to 10%. For soils with the hardwood biochar, tylosin adsorption was 10 to 18% higher than that when using the softwood biochar. Adsorption kinetics was well described by Elovich equation ( ≥ 0.921). As the percent of biochar was increased, the rates of initial reactions were generally increased, as indicated by increasing α value at low initial tylosin concentration, whereas the rates during extended reaction times were generally increased, as indicated by decreasing β value at high initial tylosin concentration. A considerably higher amount of tylosin remained after desorption in the corn field soil than in the forest soil regardless of the rate of biochar amendment, which was attributed to the high pH and silt content of the former. The breakthrough curves of tylosin showed that the two soils with biochar amendment had much greater retardation than those of soils without biochar. The CXTFIT model for the miscible displacement column study described well the peak arrival time as well as the maximum concentration of tylosin breakthrough curves but showed some underestimation at advanced stages of tylosin leaching, especially in the corn field soil. Overall, the results indicate that biochar amendments enhance the retention and reduce the transport of tylosin in soils.

An approach for mapping the vulnerability of European Union soils to antibiotic contamination

Release of antibiotics into the environment through the agricultural reuse of animal manure is considered a cause of chronic environmental exposure that often leads to adverse ecotoxicological effects, as well as to the introduction of antibiotic-resistant bacteria into the environment. The vulnerability of soil to antibiotic contamination plays a major role in determining the extent of the contamination and the likelihood of the emergence of antibiotic resistance and the appearance of ecotoxicological effects. It depends on soil characteristics, which vary across Europe, and antibiotic characteristics, which vary across drug classes. Understanding how soil vulnerability varies geographically for different veterinary medicinal products would be very useful for resource allocation among surveillance programmes. This paper performs risk analysis of the EU region for 12 antimicrobials using a spatial assessment performed in four steps. First, antibiotic release was estimated based on livestock density. Then exposure was estimated based on antimicrobial soil contamination. Third, consequences were modelled based on soil uses. Finally, risk was estimated by combining release, exposure and consequences using spatial multicriteria decision analysis. A final risk value for soil vulnerability was calculated for each antibiotic studied and displayed in chloropletic maps (ArcGIS 9.3). Furthermore, the Getis-Ord Gi statistic was used to identify clusters of areas at high risk for antibiotic soil contamination. Enrofloxacin was the highest-risk antibiotic in the European Union, followed by tetracyclines, tylosin and sulfodiazine. The highest risk values were found in Belgium, Ireland, Netherlands, Switzerland, Denmark, Germany and the UK. The results suggest that this methodology can be used successfully for evaluating the contamination potential of antibiotics over large areas with limited input data. This work is a preliminary step towards prioritising the use of veterinary medicinal products (VMPs), orientating monitoring studies and antimicrobial surveillance programmes, and informing sustainable decision-making for interventions designed to mitigate the risk of VMPs.

Aquaculture effects on environmental and public welfare - the case of Mediterranean mariculture

Aquatic farming has been considered, during the last decades, as the fastest growing food production industry powered by governmental and technological impulsion. Compensation for fisheries decline, creation of new jobs and source of financial windfall are the most important benefits. However, similar to most of the human food-production activities, aquaculture raised several issues related to the environmental welfare and consumer safety. An effort to record the aquaculture-environment and -human safety interactions with regard to the Mediterranean mariculture, is attempted herein. We focused on this geographical area due to its individualities in both the hydrological and physicochemical characteristics and the forms of aquaculture activities. The cage farming of euryhaline marine fish species and more recently of bluefin tuna and mollusk farming are the dominating aquaculture activities. The impacts of these activities to the environment, through wastes offloads, introduction of alien species, genetic interactions, disease transfer, release of chemicals, use of wild recourses, alterations of coastal habitats and disturbance of wildlife, are analytically considered. Also the consumer safety issues related to the farming are assessed, including generation of antibiotic-resistant microorganisms, contaminants transferred to humans though food chain and other hazards from consumption of aquacultured items. Within these, the major literature findings are critically examined and suggestions for scientific areas that need further development are made. The major tasks for future aquaculture development in this region are: (i) to ensure sustainability and (ii) to balance the risks to public or environmental health with the substantial economical benefits. In regard with monitoring, tools must be created or adapted to predict the environmental costs and estimate consumer impact. At a canonistic and legal basis, the establishment of appropriate legal guidelines and common policies from all countries involved should be mandatory.

Occurrence and distribution of antibiotics in coastal water of the Bohai Bay, China: impacts of river discharge and aquaculture activities

The presence of 21 antibiotics in six different groups was investigated in coastal water of the Bohai Bay. Meantime, to illuminate the potential effects caused by the river discharge and aquaculture activities, wastewater from three breeding plants and surface water from six rivers flowing into the Bohai Bay were also analyzed for the selected antibiotics. The result revealed that measured antibiotics in the North Bobai Bay were generally higher than those in the South, highlighting the remarkable effects of high density of human activities on the exposure of antibiotics in environment. The antibiotics found in the six rivers were generally higher than those in the Bohai Bay reflecting the important antibiotics source of river discharge. This study reveals that the high consumption of some antibiotics in aquaculture activities may pose high ecological risk to the bay.

Sorption and biodegradation of sulfonamide antibiotics by activated sludge: experimental assessment using batch data obtained under aerobic conditions

This study investigated the adsorption, desorption, and biodegradation characteristics of sulfonamide antibiotics in the presence of activated sludge with and without being subjected to NaN(3) biocide. Batch experiments were conducted and the relative contributions of adsorption and biodegradation to the observed removal of sulfonamide antibiotics were determined. Three sulfonamide antibiotics including sulfamethoxazole (SMX), sulfadimethoxine (SDM), and sulfamonomethoxine (SMM), which had been detected in the influent and the activated sludge of wastewater treatment plants (WWTP) in Taiwan, were selected for this study. Experimental results showed that the antibiotic compounds were removed via sorption and biodegradation by the activated sludge, though biodegradation was inhibited in the first 12 h possibly due to competitive inhibition of xenobiotic oxidation by readily biodegradable substances. The affinity of sulfonamides to sterilized sludge was in the order of SDM > SMM > SMX. The sulfonamides existed predominantly as anions at the study pH of 6.8, which resulted in a low level of adsorption to the activated sludge. The adsorption/desorption isotherms were of a linear form, as well described by the Freundlich isotherm with the n value approximating unity. The linear distribution coefficients (K(d)) were determined from batch equilibrium experiments with values of 28.6 ± 1.9, 55.7 ± 2.2, and 110.0 ± 4.6 mL/g for SMX, SMM, and SDM, respectively. SMX, SMM, and SDM desorb reversibly from the activated sludge leaving behind on the solids 0.9%, 1.6%, and 5.2% of the original sorption dose of 100 μg/L. The sorbed antibiotics can be introduced into the environment if no further treatments were employed to remove them from the biomass.

Occurrence, distribution and seasonal variation of antibiotics in the Huangpu River, Shanghai, China

Water samples were collected from 19 sampling sites along the Huangpu River in June and December 2009. The occurrence, distribution and seasonal variation of 22 antibiotics, including four tetracyclines, three chloramphenicols, two macrolides, six fluoroquinolones, six sulfonamides and trimethoprim were investigated. It was found that all 19 sampling sites were contaminated by antibiotics. Four antibiotics (sulfamerazine, norfloxacin, fleroxacin and sarafloxacin) were not detected. The detection frequencies of the other 18 antibiotics were in the range of 5.3-100%. The median concentrations of the detected antibiotics ranged from quantification limits to 36.71 ng L(-1) (tetracycline) in June and to 313.44 ng L(-1) (sulfamethazine) in December. The number of detected antibiotics and the overall antibiotic concentrations were higher in December than in June due to the different river flow conditions. Different dominant antibiotics were observed for each group of antibiotics between June and December. Higher total concentrations of veterinary antibiotics such as tetracyclines were observed in suburban sampling sites than in urban sites, indicating the role of livestock and agricultural activities as an important source of antibiotic contamination.

Simultaneous determination of three classes of antibiotics in the suspended solids of swine wastewater by ultrasonic extraction, solid-phase extraction and liquid chromatography-mass spectrometry

This work describes a systematic approach to the development of a method for simultaneous determination of three classes of veterinary antibiotics in the suspended solids (SS) of swine wastewater, including five sulfonamides, three tetracyclines and one macrolide (tiamulin). The entire procedures for sample pretreatment, ultrasonic extraction (USE), solid-phase extraction (SPE), and liquid chromatography-mass spectrometry (LC-MS) quantification were examined and optimized. The recovery efficiencies were found to be 76%-104% for sulfonamides, 81%-112% for tetracyclines, and 51%-64% for tiamulin at three spiking levels. The intra-day and inter-day precisions, as expressed by the relative standard deviation (RSD), were below 17%. The method detection limits (MDLs) were between 0.14 and 7.14 microg/kg, depending on a specific antibiotic studied. The developed method was applied to field samples collected from three concentrated swine feeding plants located in Beijing, Shanghai and Shandong province of China. All the investigated antibiotics were detected in both SS and liquid phase of swine wastewater, with partition coefficients (logK(d)) ranging from 0.49 to 2.30. This study demonstrates that the SS can not be ignored when determining the concentrations of antibiotics in swine wastewater.

Fate of antibiotics during municipal water recycling treatment processes

Municipal water recycling processes are potential human and environmental exposure routes for low concentrations of persistent antibiotics. While the implications of such exposure scenarios are unknown, concerns have been raised regarding the possibility that continuous discharge of antibiotics to the environment may facilitate the development or proliferation of resistant strains of bacteria. As potable and non-potable water recycling schemes are continuously developed, it is imperative to improve our understanding of the fate of antibiotics during conventional and advanced wastewater treatment processes leading to high-quality water reclamation. This review collates existing knowledge with the aim of providing new insight to the influence of a wide range of treatment processes to the ultimate fate of antibiotics during conventional and advanced wastewater treatment. Although conventional biological wastewater treatment processes are effective for the removal of some antibiotics, many have been reported to occur at 10-1000 ng L(-1) concentrations in secondary treated effluents. These include beta-lactams, sulfonamides, trimethoprim, macrolides, fluoroquinolones, and tetracyclines. Tertiary and advanced treatment processes may be required to fully manage environmental and human exposure to these contaminants in water recycling schemes. The effectiveness of a range of processes including tertiary media filtration, ozonation, chlorination, UV irradiation, activated carbon adsorption, and NF/RO filtration has been reviewed and, where possible, semi-quantitative estimations of antibiotics removals have been provided.

Sorption of benzimidazole anthelmintics to dissolved organic matter surrogates and sewage sludge

The sorption coefficients of four rarely studied zwitterionic pharmaceuticals (benzimidazoles: fenbendazole, albendazole, thiabendazole and flubendazole) and four metabolites of fenbendazole to various dissolved organic matter surrogates (humic acid, sodium dodecyl sulfate micelle, hydroxypropyl-beta-cyclodextrin and liposomes made of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), and sewage sludge) were measured to extend the available sorption coefficients and eventually to evaluate their environmental fate in soil and water environment. For the entire range of dissolved organic matters, the more hydrophobic fenbendazole and albendazole had higher sorption coefficients than thiabendazole and flubendazole, indicating that the traditional hypothesis of hydrophobic interaction holds for zwitterionic benzimidazole anthelmintics. However, the sorption coefficients of a given benzimidazole to selected dissolved organic matters (DOMs) varied within an order of magnitude. The measured K(oc) values decreased in the order of fenbendazole, albendazole, thiabendazole and flubendazole for sewage sludge and hydroxypropyl-beta-cyclodextrin whereas the orders were different for the other DOM surrogates, implying the hydrophilic nature of sewage sludge. This was also supported by the (N+O)/C elemental ratio of the sewage sludge sample used in this study. The correlations between log K(oc) and log K(ow) were weak (r(2)=0.28-0.64) and the magnitude of the sorption coefficients to the hydrophilic organic matters (hydroxypropyl-beta-cyclodextrin and sewage sludge) were similar to or slightly smaller than those for the hydrophobic organic matters (humic acids and liposome). This suggests that specific hydrophilic interactions also play a significant role in the sorption of moderately hydrophobic benzimidazoles to organic matters.

Simulated rainfall study for transport of veterinary antibiotics--mass balance analysis

Occurrence of human and veterinary antibiotics has been reported in various environmental compartments. Yet, there is a lack of information verifying the transport mechanisms from source to environment, particularly the transport of veterinary antibiotics as a non-point source pollutant. A rainfall simulation study was conducted to address surface runoff as a possible transport mechanism of veterinary antibiotics introduced in the field and mass balance was calculated with supplementary surface and depth soil measurement. Seven veterinary antibiotics that are the most abundantly used in agriculture for therapeutic and non-therapeutic (growth-promotion) purposes were examined in this study, including tetracycline (TC), chlortetracycline (CTC), sulfathiazole (STZ), sulfamethazine (SMZ), erythromycin (ETM), tylosin (TYL), and monensin (MNS). Runoff in aqueous and sediment phases was collected every 5 min for 1h with varied rainfall intensity and additional surface (0-2 cm) and depth (2-30 cm) soil samples were collected after rainfall simulation for mass balance analysis. Quantification of antibiotic concentration in all collected samples was based on solid phase extraction (SPE) followed by measurement with high-performance liquid chromatography/tandem mass spectrometry (HPLC/MS/MS). MNS showed the highest concentration in runoff aqueous samples (0.22 mg plot(-1)), while ETM showed the highest concentration in runoff sediment samples (0.08 mg plot(-1)). The highest concentration of each applied antibiotic in surface soil samples occurred at different locations. This result might indicate the mobility of these compounds in surface soil varies due to different physicochemical properties among the antibiotics. Further, the analysis results showed that all of the subject antibiotics had penetrated into the subsurface; yet, no residuals were found for STZ, suggesting this compound might have penetrated even deeper into the soil. These results indicate that aqueous or sediment erosion control might reduce the transport of veterinary antibiotics in the environment.

Effects of Swine manure on macrolide, lincosamide, and streptogramin B antimicrobial resistance in soils

Current agricultural practices involve inclusion of antimicrobials in animal feed and result in manure containing antimicrobials and antimicrobial-resistant microorganisms. This work evaluated the effects of land application of swine manure on the levels of tetracycline, macrolide, and lincosamide antimicrobials and on macrolide, lincosamide, and streptogramin B (MLS(B)) resistance in field soil samples and laboratory soil batch tests. MLS(B) and tetracycline antimicrobials were quantified after solid-phase extraction using liquid chromatography-tandem mass spectrometry. The prevalence of the ribosomal modification responsible for MLS(B) resistance in the same samples was quantified using fluorescence in situ hybridization. Macrolide antimicrobials were not detected in soil samples, while tetracyclines were detected, suggesting that the latter compounds persist in soil. No significant differences in ribosomal methylation or presumed MLS(B) resistance were observed when amended and unamended field soils were compared, although a transient (<20-day) increase was observed in most batch tests. Clostridium cluster XIVa accounted for the largest fraction of resistant bacteria identified in amended soils. Overall, this study did not detect a persistent increase in the prevalence of MLS(B) resistance due to land application of treated swine manure.

Hydrolysis and photolysis of oxytetracycline in aqueous solution

Oxytetracycline ((2Z,4S,4aR,5S,5aR,6S,12aS)-2-(amino-hydroxy-methylidene)-4-dimethylamino-5,6,10,11,12a-pentahydroxy-6-methyl-4,4a,5,5a-tetrahydrotetracene-1,3,12-trione) is a member of tetracycline antibiotics family and is widely administered to farm animals for the purpose of therapeutical treatment and health protection. Increasing attention has been paid to the environmental fate of oxytetracycline and other veterinary antibiotics with the occurrence of these antibiotics in the environment. The hydrolysis and photolysis degradation of oxytetracycline was investigated in this study. Oxytetracycline hydrolysis was found to obey the first-order model and similar rate constant values ranging from 0.094 +/- 0.001 to 0.106 +/- 0.003 day(-1) were obtained at different initial concentration ranging from 10 to 230 microM. Solution pH and temperature were shown to have remarked effects on oxytetracycline hydrolysis. The hydrolysis in pH neutral solution appeared to be much faster than in both acidic and alkaline solutions. Oxytetracycline half-life decreased from 1.2 x 10(2) to 0.15 day with the increasing temperature from 4 +/- 0.8 to 60 +/- 1 degrees C. The presence of Ca(2+) made oxytetracycline hydrolytic degradation kinetics deviate from the simple first-order model to the availability-adjusted first-order model and greatly slowed down the hydrolysis. Oxytetracycline photolysis was found to be very fast with a degradation rate constant at 3.61 +/- 0.06 day(-1), which is comparable to that of hydrolysis at 60 degrees C. The presence of Ca(2+) accelerated oxytetracycline photolysis, implying that oxytetracycline become more vulnerable to sunlight irradiation after chelating with Ca(2+). The photolysis may be the dominant degradation pathway of oxytetracycline in shallow transparent water environment.

Sorption and desorption of antibiotic tetracycline on marine sediments

Tetracycline is commonly used for human therapy and veterinary purposes as well as agricultural feed additives. In this study, batch experiments were carried out to investigate the sorption behaviour of tetracycline on marine sediments. The sediment samples were collected from Victoria Harbour, Hong Kong. Sorption isotherms of tetracycline on marine sediments can be well described by a Freudlich model. The calculated K(f) varied from 1.12 to 2.34Lg(-1). After H(2)O(2) oxidation for removing the organic carbon from marine sediments, the K(f) values were reduced by more than 80%, but the organic carbon normalized sorption constant averaged 213.1Lg(-1) for the H(2)O(2)-treated sediments, which was higher than 98.3Lg(-1) for the raw marine sediments. The calculated hysteresis coefficient H ranged from 0.79 to 0.90 indicating that there is a hysteresis in desorption. The sorption of tetracycline on marine sediments was found to decrease with an increase of pH and salinity. These research findings are of importance to an assessment of the fate and transport of tetracycline and other similar antibiotics in seawater-sediment systems.

Treatment of chloramphenicol-contaminated soil by microwave radiation

This paper describes the microwave (MW) treatment of soil contaminated by chloramphenicol (CAP), using granular activated carbon (GAC) as MW absorbent. It was found that the addition of GAC effectively increased the temperature of soil. Large MW power and GAC dosage were beneficial for a completed decomposition of CAP. The effect of initial CAP concentration on decomposition was minute and a small scale of soil/GAC was disadvantageous. The degradation mechanism by MW radiation was also explored. The decomposition product of 4-nitrobenzoic acid after MW radiation was confirmed by LC-MS. The analysis by GC-MS and FTIR proved that parts of the decomposed fragment of CAP reacted with soil organic matters and formed compounds with larger molecular weight than CAP, but the concentration of each product was extremely low. It was suggested that MW radiation was an alternative technology for the treatment of antibiotics-contaminated soils.