抗生素降解

Accepted Manuscript

The behavior of tetracyclines and their degradation products during swine man‐

ure composting

Xiaofeng Wu, Yuansong Wei, Jiaxi Zheng, Xin Zhao, Weike Zhong

PII:

DOI:

Reference:

To appear in:

Received Date:

Revised Date:

Accepted Date:S0960-8524(11)00349-X10.1016/j.biortech.2011.03.007BITE 8240Bioresource Technology29 October 20103 March 20113 March 2011

Please cite this article as: Wu, X., Wei, Y., Zheng, J., Zhao, X., Zhong, W., The behavior of tetracyclines and theirdegradation products during swine manure composting, Bioresource Technology (2011), doi: 10.1016/j.biortech.2011.03.007

This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customerswe are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, andreview of the resulting proof before it is published in its final form. Please note that during the production processerrors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

The behavior of tetracyclines and their degradation products during swine manure composting

Xiaofeng Wu, Yuansong Wei∗, Jiaxi Zheng, Xin Zhao, Weike Zhong a a a, a b b Beijing 100085, P. R. China.

b Abstract

including chlortetracycline (CTC), (OTC) and tetracycline (TC) and and also to study the degradation kinetics and TC. During the pilot scale composting, CTC, OTC and TC by 74%, 92% and 70%, respectively. Several degradation found like 4-epitetracycline (ETC), 4-epioxytetracycline (EOTC), (ECTC), demeclocycline (DMCTC) and (ATC). Both the simple and the adjusted first-order kinetic fit the degradation process of CTC, OTC and TC during the but the adjusted first-order kinetic model fit much better with the calculated half-lives of 8.2, 1.1 and 10.0 days, respectively.

Keywords : Swine Manure; Composting; Degradation product; Degradation kinetic; ∗ Corresponding author. Tel.: +86 010 62849109; fax: +86 010 62849109.

E-mail address

Tetracyclines

1. Introduction

Animal Feeding Operations (CAFOs) to treat and prevent diseases Phillips et al., 2004; Sarmah et al., 2006). For example, of the for non-therapeutic purposes in 2000 (Sarmah et al., the administered et al., 2004; Winckler and Grafe, in the form of their parent Tetracyclines such (TC), oxytetracycline (OTC) and chlortetracycline the most common antibiotics used in animal husbandry (De al., 2003; Kumar et al., 2005; Sarmah et al., 2006). It is farm animals in the United States (Arikan et al., 2007; Bao et al., tetracyclines residues in animal manure due to the wide usage and absorption can be detected in the level of mg/kg or even up to several hundreds of mg/kg (Bao et al., 2009; De Liguoro et al., 2003; Shen et al., 2009a; Zhao et al., 2010) and thus pose an increasing potential risk to human health and ecosystem safety with the application of manure as fertilizers in agricultural lands (Boxall et al., 2003; Kummerer, 2003). Therefore, it is necessary and important to treat and dispose animal manure before its land application to reduce the amount of veterinary

antibiotics released into the environment and minimize the risk of the widespread development of resistant bacteria derived from residual antibiotics (Kemper, 2008; Sarmah et al., 2006).

As an established and well-developed technology for stabilization of organic

proved to be a feasible and effective approach to promote in and Funamizu, 2007; Kakimoto et al., 2007; 2010; Shen et al., days of beef manure composting, in the compost mixture et al., 2008), the chlortetracycline during manure composting achieved during the 38-day composting period. All the mentioned clearly showed that composting is effective to remove the residual in animal manure. Factors of possibly affecting removal behavior of tetracyclines such as temperature, moisture and other abiotic conditions are of great attention (Bao et al., 2009; Dolliver et al., 2008; Wang and Yates, 2008). However, there is litter information on their fate concerning about the degradation products and degradation process during animal manure composting. It is known that generation of tetracyclines’ degradation products depends on different pH conditions because their

molecular structure contains four connected benzene rings (lettered A through D from right to left) with multiple ionizable functional groups (Chen and Huang, 2009) as shown in Fig. 1. For instance, the 4-epimers such as 4-epitetracycline (ETC), 4-epioxytetracycline (EOTC) and 4-epichlortetracycline (ECTC) can be reversibly formed under mildly acidic conditions (pH 2-6). Strong acidic conditions (pH facilitate the formation of anhydro-tetracyclines that could their

are stable, anhydro-oxytetracycline is quite unstable and -OTC and are even more toxic than their parents et al., 2002). Moreover, some metabolites can also be to the parent compounds (Kemper, 2008; Sarmah et al., there is lack of knowledge involving degradation products as most researchers usually just focus on the OTC their degradation products in soil interstitial water have been et al., 2003; Søeborg et al., 2004), but during animal and concerned about the degradation products in a laboratory scale. Degradation processes of the other two common tetracyclines during animal manure composting have not been the subject of research recently.

In this study, the behavior of three tetracyclines such as tetracycline (TC), oxytetracycline (OTC) and chlortetracycline (CTC) as well as their potential

degradation products were investigated during a pilot scale swine manure composting in the spring. Moreover, the degradation kinetics of the three parent tetracyclines were also studied and compared on the basis of both the simple and adjusted first-order kinetic model.

2. Materials and Methods

2.1 Chemicals and Standards

hydrochloride (TC, 97.5% purity, CAS no. 64-75-5), hydrochloride 99.0% purity Degradation products of these three with high purity (>97%) including (ETC), anhydrotetracycline

4-epioxytetracycline

-apo-oxytetracycline (ATC), (EOTC), ( -apo-OTC), 4-epianhydrotetracycline (

in the darkness.

Acetonitrile, methanol and ethyl acetate from J.T. Baker Co. (USA) were all of HPLC-grade. The HPLC-grade formic acid (88% purity, CAS no.64-16-6) was purchased from Mallinckrodt Baker Inc. (USA). All of the following chemicals, including disodium hydrogen phosphate dodecahydrate, citric acid monohydrate and ethylenediamineteraacetic acid disodiumsalt (Na2EDTA), were of analytical pure grade. The ultra pure water was supplied by a Millipore Milli-Q system.

2.2 The pilot scale swine manure composting

A pilot scale of swine manure composting was carried out in the spring to further investigate the fate behavior of tetracyclines and their degradation products. It was pile was about 5 m3days 1, 4, 7, 14, 21, 28, 35, 52, respectively, collected by mixing the upper, Parameters all materials including pH, electrical conductivity (EC), organic matter, TKN, TP were analyzed according to the 2000). The evolution of temperature that concerns about ambient of the pile including upper, central and lower part was

To determine tetracyclines and their degradation products, samples stored at -20 were firstly thawed, freeze-dried (ALPHA 1-2LD PLUS, Christ, Germany) and then sieved by nylon screen with mesh size of 100, and finally analyzed by using an improved method described by Shen (Shen et al., 2009a). Each sample at 1 g was extracted with 10 mL McIlvaine–Na2EDTA buffer prepared by mixing 0.1 mol/L

citric acid monohydrate solution with 0.2 mol/L disodium hydrogen phosphate dodecahydrate solution, adding 0.1 mol/L ethylenediamineteraacetic acid disodiumsalt (Na2EDTA). After vortexed for 1 min, 5 mL acetonitrile was added to increase the extraction efficiency and then followed by intensively shaking for 30 min and centrifugation at 15,000 r/min of 4 °C for 5 minutes. The same procedure was repeated twice, and then all the supernatant was and

water. For sample purification and pre-concentration, a (SUPELCO VISIPREP TM DL, USA) was applied. Firstly, extraction (SPE) cartridges (Oasis HLB, 150 mg, 6 mL) with 5 mL methanol followed by 5 mL McIlvaine–Na25 mL 5% methanol Finally, the cartridges were eluted with 9 mL dryness of nitrogen and then reconstituted with 1.0 mL acetonitrile formic acid (1:9, v/v) followed by filtration with 0.22 m nylon

Concentrations of the three parent tetracyclines and their degradation products were determined by an ultra performance liquid chromatography with tandem mass spectrometry (Waters Corp., USA). Separation of tetracyclines and their degradation products was achieved with an Acquity UPLCTM C18 column (i.d. 2.1 mm×50 mm,

1.7 µm. Waters, USA).The column was maintained at 35 while the sample room was kept at 10 and the injection volume was 10 µL. The gradient of mobile phase consisted of acetonitrile (A) and 0.1% formic acid (B) with a constant flow rate at 0.30 mL/min was shown as follows: the initial 5% A was increased linearly to 17% in maintain equilibration. The total run time was 11 min.

Quattro Premier XE triple quadrupole mass with an electrospray ionization source that operated in the mode (ESI+). The operation conditions were optimized source temperature 120 °C, desolvation temperature 350 , desolvation gas flow 600 L/h, tetracyclines and products were summarized in Table 2. Peak 2.5 of recovery, limit of detection (LOD) and limit of quantification To determine the extraction efficiency of all target compounds, samples were spiked with their standard solutions at three levels: 0.2 mg/kg dry weight (DW), 1.0 mg/kg DW and 4.0 mg/kg DW, respectively. Triplicate samples were extracted and analyzed as described above.

The limit of detection (LOD) and limit of quantification (LOQ) of this method were evaluated by spiking samples with a mixture of all standards at a low

concentration and calculated as the signal-to-noise (S/N) ratio was 3 and 10, respectively, based on the obtained peaks. The reproducibility was assessed by run-to-run recoveries (eleven successive injections). Calibration curves were constructed from 0 to 300 µg/Lg/L with correlation coefficient R 2 representing their linearity. The precision of method was expressed as the relative standard (RSD) of triplicate measurements.

2.6 Kinetic model

It is well known that in most cases degradation of in the environment follows the simple first-order kinetic is described as follow:

d t

Where C t and k is the

t 1/2=ln2/k

fixation (Thiele-Bruhn, 2003). Hence, the simple first-order kinetic to be improved and the adjusted first-order kinetic model was more accurate and clearer information on the degradation process of organic compounds, which is shown as follow (Wang and Yates, 2008):

d C /dt =-k C

Where is defined as the concentration ratio of the available portion to the total target compound and is assumed as a function of t expressed as = 0e -at where 0 is the

value obtained when t=0 and a is called availability coefficient. The called degradation rate constant k ’’=k 0 is defined, and then we acquire the equation

d C /dt =-k ’’C e-at

Consequently, the half-life is derived as

t 1/2=-ln(1-a ln2/ k’’) /a

3. Results and discussion

3.1 Method validation

Table 3 presented that there was difference between recovery of parent tetracyclines could be the range of 71-89%, 66-94% and 66-84% for TC, OTC and The recovery of DMCTC was in the other two epimers’ ETC and ECTC were in the range of 32-51%. of characteristics could be another possible reason, especially for because they are formed under strong acidic situations the whole pretreatment process was maintained in weak acidic conditions to achieve simultaneous determination the parent tetracyclines and their degradation products.

Although the determination of tetracyclines in animal manure was a hot topic (KarcI and BalcIoglu, 2009; Martinez-Carballo et al., 2007; Zhao et al., 2010), there was limited reports concerning about the recoveries of their degradation products. It

was reported by Arikan (Arikan et al., 2006) that the recoveries of Æ- apo-OTC and - apo-OTC in beef manure were 40% and 25% respectively. The same low recovery had been previously reported by Fedeniuk (Fedeniuk et al., 1996). Loke (Loke et al., 2003) found that the recovery of Æ- apo-OTC in the manure-containing matrix was 18.3% slightly higher than our findings.

The results indicated good reproducibility and great linearity of the curve with all R 2

range of 1.668-17.270 µg/kgg/kg and 5.561-45.918 µg/kgg/kg (Table a high sensitivity of the method.

3.2 Composting process

As shown in Fig. 2(a), the increased continuously during central portion of the pile much higher than that of the other two within 5 days for the whole period except for some occasional down, the requirement of sanitary standard for the non-hazardous soil in China (GB 7959-87). High level of microbial activity for the rapid increase of pile temperature and the high pile temperature

In Fig. 2(b) and 2(c), the pH value was kept about 8.5 with a little decline in the maturity stage while EC had a general ascending trend. Moisture content was observed in the range of 50%-65% suitable for composting due to irregularly water addition. Besides, decomposition of organic matter could be inferred from its descending content during the whole composting process.

3.3 Behavior of tetracyclines and their degradation products in the pilot scale swine manure composting

Fig. 3 illustrated the behavior of tetracyclines during the pilot scale swine manure composting process. The initial concentrations of three parent (Arikan et al., 2009; Bao et al., 2009; Ramaswamy et This may be attributed to different application amounts of feed livestock production. Degradation of these three tetracyclines can observed because not only their unique chemical structure, and undergo abiotic degradation conditions such as pH, temperature, redox and then generate degradation products via epimerization, or other pathways (Halling-Sørensen et al., 2003; Kühne et al., DMCTC was detected in this study, its initial epimers as ECTC, EOTC together with ETC, and another degradation of the 4-epianhydrotetracyclines of the three parent tetracyclines had been discovered during the composting. The slight alkaline condition (Fig. 2(b)) in the pile may be helpful to account for this because anhydrotetracyclines could only be formed when they are under strongly acidic conditions. Both of ECTC and ICTC were found in beef manure composting (Arikan et al., 2009), however, the standard of ICTC was not

commercially available so it can not be determined in our study. In addition, -apo-OTC and -apo-OTC had been observed in anaerobic tests (Loke et al., 2003), but they could not be detected in this study either.

As shown in Fig. 3, not only did the parent tetracyclines decrease, but also the degradation products went down during the swine manure composting. It

phenomenon was possibly related with the inadequate veterinary (Elmund et al., 1971). Both the and its degradation product ECTC declined fast during the process and their removal rates were 74% and 82% separately. By composting, DMCTC went down to close to its after to about 0.25 mg/kg DW in the first week. As far as TC was its initial concentration was less than 0.5 mg/kg DW and decreased to 74% of its degradation product ETC was removed within the first week and another degradation product ATC was maintained all the same at levels only above its detection limit.

The above results elucidated that all the three tetracyclines could undergo degradation process and be removed during the course of composting, and thus

demonstrated that composting is an effective alternative to remove residual antibiotics in animal manure as reported before (Arikan et al., 2007; Bao et al., 2009; Dolliver et al., 2008; Kakimoto and Funamizu, 2007; Kakimoto et al., 2007; Ramaswamy et al., 2010).

3.4 Degradation kinetics of tetracyclines

TC The degradation data of three parent tetracyclines such as and

during the pilot scale swine manure composting was fitted commonly process of the three tetracyclines during the as all of their correlation coefficients R 2 parent tetracyclines than first-order kinetic model. For example, at the of the adjusted first-order kinetic model confirmed the existed behavior of sorption in the manure and also proved that the availability of tetracyclines declined during the composting. Interestingly, OTC appeared to obey the two models most successfully among the three target tetracyclines with correlation coefficients of 0.9286 and 0.9969, respectively.

The half-lives of CTC, OTC and TC calculated by the simple first-order kinetic model were 16.95, 2.66 and 22.36 days, respectively, while the obtained half-lives using the adjusted first-order kinetic model were 8.25, 1.14 and 10.02 days, respectively, nearly half of the former results. Thermal degradation might contribute the degradation rates of residual tetracyclines in swine as temperature increasing and achieved the maximum at 55 2009b). Generally, pile temperature should maintain at 50-55 according to the sanitary standard (GB7959-87) to the pathogens during composting, as shown in our study (Fig. 2). such high pile temperature composting. Microbial activity also important role in the composting, not to promote the As the decomposition temperatures of tetracyclines are above 170 , we proposed that it was synergy effect of the composting. Compared with longer half-lives of CTC and TC, constant k ’’ and availability coefficient a of OTC in the adjusted first-order kinetic model were higher than those of CTC and TC. The higher the value of a was, the more the OTC was available. The higher rate constant k ’’ of OTC was, the faster degradation process and shorter half-life of OTC were. The fate of tetracyclines during the composting had been the subject of numerous studies (Arikan et al., 2007;

Bao et al., 2009; De Liguoro et al., 2003; Dolliver et al., 2008) and the results of half-life differed to some degree. Arikan (Arikan et al., 2007) reported a calculated half-life of OTC at approximately 3.2 days during beef manure composting which was comparable with our result, but De Liguoro (De Liguoro et al., 2003) found that the half-life of OTC in the stockpiled manure-bedding mixture was 30 days compound was still detectable after 5 months. Assuming the first-order the half-life of CTC in the managed manure composting was only 1 by were 11.0 days in broiler manure and 12.2 days in manure, which were consistent with our finding.

Furthermore, it could be inferred 4 that the degradation behavior of three parent tetracyclines CTC, during the swine manure composting predominately took place stage as their concentration almost reached the plateau except that the concentration of OTC achieved on both the and adjusted first-order kinetic models were less than 25 days, (Fig. 2), which was advantageous to their degradation.

4. Conclusions

During the pilot scale swine manure composting, the degradation of CTC, OTC and TC occurred, with a removal rate of 74%, 92% and 70% for CTC, OTC and TC, respectively, and their degradation behavior predominately took place in the

thermophilic stage of composting. Several degradation products were detected including ECTC, EOTC, ETC, DMCTC and ATC. Both the simple and the adjusted first-order kinetic models fit their degradation process, but the adjusted first-order kinetic model was much better.

Acknowledgements

This work is financially supported by the National (No. 21077122).

References

Arikan, O. A., Mulbry, W., Management of antibiotic residues in beef treated animals. J. Hazard. Mater. 164(2-3), 483-489.

Arikan, J., Mulbry, W., Khan, S. U., Foster, G. D., 2007. . D., The fate and effect of oxytetracycline during the anaerobic digestion of manure from therapeutically treated calves. Process Biochem. 41(7), 1637-1643.

Bao, S. D., 2000. Soil Agricultural Chemical Analysis, third ed. Agriculture Press, Beijing (in Chinese).

Bao, Y., Zhou, Q., Guan, L., Wang, Y., 2009. Depletion of chlortetracycline during composting of aged and spiked manures. Waste Management 29(4),

1416-1423.

Boxall, A. B. A., Kolpin, D. W., Halling-Sorensen, B., Tolls, J., 2003. Are veterinary medicines causing environmental risks? Environ. Sci. Technol. 37(15), 286-294.

by Mn(II) and Cu(II) Ions in the Presence of Oxygen. Environ. 43(2), 401-407.

De Liguoro, M., Cibin, VElmund, Gexcreted the decomposition process in feedlot W., Ramamurthi, S., McCurdy, A. R., 1996. Application of liquid chromatography and prepacked C-18 cartridges for the oxytetracycline and related compounds. J. Chromatogr. B-Biomed. Halling-Sørensen, B., Lykkeberg, A., Ingerslev, F., Blackwell, P., Tjørnelund, J., 2003. Characterisation of the abiotic degradation pathways of oxytetracyclines in soil interstitial water using LC-MS-MS. Chemosphere 50(10), 1331-1342.

Halling-Sørensen, B., Nors Nielsen, S., Lanzky, P. F., Ingerslev, F., Holten Lützhøft, H. C., Jørgensen, S. E., 1998. Occurrence, fate and effects of pharmaceutical substances in the environment- A review. Chemosphere 36(2),

357-393.

Halling-Sorensen, B., Sengelov, G ., Tjornelund, J., 2002. Toxicity of tetracyclines and tetracycline degradation products to environmentally relevant bacteria, including selected tetracycline-resistant bacteria. Arch. Environ. Contam. Toxicol. 42(3), 263-271.

Kühne, M., Hamscher, G ., Körner, U., Schedl, D., Wenzel, Formation of anhydrotetracycline during a of Kakimoto, T., Funamizu, N., 2007. Factors degradation of Kakimoto, T., Osawa, T., N., 2007. Antibiotic effect of amoxicillin on the feces and reactivation of bacteria by KarcI, A., A., 2009. Investigation of the tetracycline, sulfonamide, and antimicrobial compounds in animal manure 2008. Veterinary antibiotics in the aquatic and terrestrial K., Gupta, S. C., Baidoo, S. K., Chander, Y ., Rosen, C. J., 2005. Antibiotic uptake by plants from soil fertilized with animal manure. J. Environ. Qual. 34(6), 2082-2085.

Kumar, K., Gupta, S. C., Chander, Y., Singh, A. K. (2005). Antibiotic use in agriculture and its impact on the terrestrial environment. Adv. in Agron. 87: 1-54.

Kummerer, K., 2003. Significance of antibiotics in the environment. J. Antimicrob. Chemother. 52(1), 5-7.

Loke, M.L., Jespersen, S., Vreeken, R., Halling-Sørensen, B., Tjørnelund, J., 2003. Determination of oxytetracycline and its degradation products by high-performance liquid chromatography-tandem mass spectrometry in manure-containing anaerobic test systems. J. Chromatogr. B 783(1), 11-23.

Martinez-Carballo, E., Gonzalez-Barreiro, C., Scharf, S., Gans, O., Environmental monitoring study of selected veterinary antibiotics manure and soils in Austria. Environ. Pollu. 148(2), 570-579.

Phillips, I., Casewell, M., Cox, T., De Groot, B., Jones, R., animals pose a risk to human health? A of published data. J. Antimicrob. Chemother. 53(1), 28-52.

and chlortetracycline degradation products and epimers in soil sales, exposure pathways, occurrence, fate and effects of veterinary antibiotics (VAs) in the environment. Chemosphere 65(5), 725-759.

Shen, Y ., Wei, Y ., Guo, R., Xu, C., Zhang, Z., Zhou, G ., Zhao, X., Liu, J., 2009a. Tetracyclines residues in swine manure: determination by UPLC-Q-TOF MS/MS. Environment Chemistry 28(5), 747-752 (in Chinese).

Shen, Y ., Wei, Y ., Zheng, J., Fang, Y ., Chen, L., 2009b. Biodegradation of Tetracycline Antibiotics Residues in Swine Manure. The Chinese Journal of

Process Engineering 9(5), 962-968.

Thiele-Bruhn, S., 2003. Pharmaceutical antibiotic compounds in soils - A review. J. Plant Nutr. Soil Sci. 166(4), 546-546.

Tolls, J., 2001. Sorption of veterinary pharmaceuticals in soils: A review. Environ. Sci. Technol. 35(17), 3397-3406.

Tylova, T., Olsovska, J., Novak, P., Flieger, M., 2010. Ultra Performance Liquid Chromatography with UV 78(4), 353-359.

Wang, Q. Q., Yates, S. R., 2008. of oxytetracycline degradation kinetics in animal manure soil. J. Agric. Food Chem. 56(5), 1683-1688.

Winckler, C., Grafe, A., of veterinary drugs in intensive animal in eight provinces of China. Sci. Total Environ.

Tables and figures Table 1

Characteristics of raw materials in the pilot scale swine manure composting.

Characteristics Moisture (%) EC ( S/cm) OM (%) TKN a (g/kg) TP a (g/kg) C:N

66.3 1236 64.3 30.36 12.01 9.01

25.1 1580 87.0 24.82 4.69 16.77

11.02

a

Measured based on dry matter.

Table 2

The optimized MS/MS parameters used for identification and quantitation of three tetracyclines and their degradation products in MRM condition.

time [M+H] + ions ions voltage Compounds

(min) (V) m/z m/z m/z 6.69 427 410 31

(EATC) 154 Anhydrotetracycline 410 16

6.87 427 410 (ATC) 154 34

-apo-oxytetracycline 426 16

5.55 443 426 ( - apo-OTC) 408 25 -apo-oxytetracycline 426 16

6.82 443 31

( - apo-OTC) 408 25

19 4-epitetracycline (ETC) 410

28 4.32 445

15 Tetracycline (TC) 19

5.08 445 28

15

4-epioxytetracycline (EOTC) 444 16

4.47 461 426 22

19

Oxytetracycline (OTC) 16

4.72 426 22

426 19

Demeclocycline (DMCTC) 448 19

5.78 448 34

430 25

4-epichlortetracycline 444 22

479 444 34

(ECTC) 462 15

Chlortetracycline (CTC) 444 22

6.34 479 444 34

462 15

Table 3

Recovery, LOD and LOQ, reproducibility and linearity of three tetracyclines and their degradation products.

Compounds ETC A TC EA TC OTC EOTC - apo-OTC - apo-OTC CTC ECTC DMCTC

DW: dry weight.

0.2 51±11.4 21±13.8 3±8.9 66±25.7 32±28.8 4±21.9 50±6.7 84±1.9 124±0.1 53±6.9

1.0 37±15.7 26±6.6 6±1.2 94±17.1 35±1.3 8±13.5 43±10.0 83±7.4 102±4.8 64±6.1

4.0 36±7.9 21±12.7 6±11.1 73±7.2 46±2.2 3±11.0 24±14.5 66±4.1 48±2.1 52±3.7

LOD LOQ Reproducibility ( g/kg) ( g/kg) (%,n=11) R 23.189 2.947 1.668 1.893 13.775 4.444 3.791 12.346 6.707 17.270 10.630 9.824 5.561 6.309 45.918 14.814 57.567 5.843 13.326 6.789 10.742 7.055

0.9997 0.9984 0.9994 0.9979 0.9987 0.9991 0.9989 0.9996

N(CH3) 2

(TC)

Fig. 1. Chemical structure and property of tetracyclines (TCs)

Time (d)

(c) TC

Fig. 4. Degradation kinetics of three tetracyclines (a) CTC, (b) OTC and (c) TC during the pilot scale swine

manure composting.