| 其他摘要 | Antibiotics are commonly used for diseases treatment of human and animals, and especially used as feed additives for animals in recent years. Antibiotics which could lead to bacteria resistance, disturbance of micro-ecology balance or even impact on the ecology and human unexpectedly, can enter the environment through many pathway, such as excrement used as fertilizer, medicine discarding, municipal sewage discharge and so on,. Antibiotic contamination is a new environment problem addressed recently all over the world, and a few researches are reported. To learn the characteristics of environment effect of antibiotics, it is necessary to make a special study in the transfer, fate and behavior of the medicine. In this article, geochemical behavior of chloramphenicol (CAP), oxytetracycline (OTC), teracycline (TC) and chorltetracycline (CTC) in municipal sewage, Nanming River and Wujiangdu reservoir are studied, including the distribution, fate and influence factor of the analytes in environment. Antibiotics in animal food are also determined. Under test conditions in aquatic systems, stability and sorption of the target compounds are studied to learn the degradation and fate of the medicine in environment. Based on these studies, the impact of the antibiotics on environment can be evaluated and scientific basis for the control and treatment of the antibiotic contamination is provided. The content of this research describes as follow.
1. A rapid and effective method for determination of CAP, OTC, TC and CTC in river water, soil and sediment using solid-phase extraction with high-performance liquid chromatography-UV detection is described. The four antibiotics in water, soil and sediment were extracted using EDTA and McIlvaine buffer (citric acid and sodium orthophosphate). Strong anion exchanger (SAX) cartridge was used to remove natural organic matter, and hydrophilic-liphophilic balance (HLB) cartridge was used to retain and pre-concentrate the antibiotics. The separation and determination of four target compounds is carried out by HPLC-UV.
2. It is proved that antibiotics exist widely in the municipal sewage. Of the four analytes in the sewage of Guiyang city, the contamination of CAP is the most predominant. The concentration of CAP in sewage of Guiyang city is higher than that in Gangzhou city, and the concentration of tetracyclines (TCs) is familiar to that in America and western countries. This result shows that antibiotic pollution is severe and could have a serious impact on the environment of surface water. The sources of antibiotics in municipal sewage include human medicine and animal food with antibiotics residue which is eaten or discarded by people. The concentration of antibiotics in sewage shows a seasonal variety. The contamination of antibiotics in municipal sewage reveals the misuse of antibiotics especially illegal use of CAP, and more attention must be paid to the menace of antibiotics to the environment.
3. It is confirmed that Nanming River is influenced by many antibiotic sources, of which the municipal sewage is the most important one, and the antibiotics is persistent in the river to some extent. The antibiotics sources upstream include suburban town sewage, aquaculture, medical factory and earth waste. The antibiotic sources downstream include municipal sewage, suburban town sewage and agriculture, of which the municipal sewage is the most important source. The sewage makes the antibiotics pollution downstream more severe than upstream. The four analytes shows different distribution in river water and sediment: CAP contamination is predominant in river water and TCs are predominant in river sediment. It is indicated that sorption/desorption is a significant factor that influences the partitioning of antibiotics between water and sediment. The occurrence of antibiotics implies an affinity of CAP to aqueous phase, and an affinity of TCs to sediment. Although been prohibited using in animal feed, CAP largely exists in river and sewage, which implies the illegal using of CAP. The concentration of antibiotics in river water shows evidently seasonal change: the concentration in winter and spring is higher than that in summer and autumn, because of the dilution of the high flow in summer and winter. However, the seasonal change of antibiotics concentration in sediment is not distinct. The concentration of the compounds in water is obviously different between upstream and downstream of the sewage outlet, because of the influence of the municipal sewage. Whereas, except obviously influenced by sewage in winter, sediment is not evidently influenced by sewage, causing by the great impact of other sources of antibiotics in spring, summer and autumn. Especially in summer, the content of CAP in most sediment upstream is higher than downstream, because the impact of the sewage with lowest antibiotics content is weak and the earth waste upstream which is usually a source of antibiotics rushes into the river upstream by the downfall in summer.
Antibiotics contamination in Nanming River is persistent in 20 km and may have a great impact on the water ecosystem. Moreover, the Nanming river water is always used for irrigating in agriculture along the river, and it would threaten the food chain and would potentially endanger the health of human.
4. Environment behavior of antibiotics is studied, and residue characteristic of antibiotics in food (such as fish and pork) is also researched, as food is always an antibiotics source of municipal sewage. The study in aquaculture farm shows that the fish feed contains high concentration of antibiotics and leads to the antibiotics contamination to the water environment of the farm. The antibiotics in fish feed do not cause serious impact on water, but it cause serious residue in sediment under the fish cabin and also in the river-route. Considering the seasonal change of the compounds concentration in sediment, the dosage of TCs used in autumn is more than other seasons, and the dosage of CAP is equivalent in each season. Despite of high content of CAP in feed, the content of TCs in sediment is higher than CAP, because of the affinity of TCs to sediment and CAP to water. The antibiotics pollution in Wujiangdu reservoir is getting worse, the antibiotics in sediment have a potential menace to the ecosystem because the antibiotics would be released under some condition.
Animal foods (fish, pork and milk) which have been analyzed have high concentrations of antibiotics residues. One part of the compounds will enter the municipal sewage with excrement, and the other part will accumulate in human body which may hurt the human health. The contents of CAP, OTC, TC, CTC in the five familiar kind of fish range from 57.1～365.5 µg/kg, 37.0～60.7µg/kg, 34.3～72.4 µg/kg and 22.3～68.0 µg/kg respectively. The average content of CAP, OTC, TC and CTC in other animal flesh is 88.1 µg/kg, 76.8 µg/kg, 343.7 µg/kg and 34.2 µg/kg. The concentration of CAP, OTC, TC and CTC in milk is 4.2 µg/L, 1.6 µg/L, 2.5 µg/L and 22.0 µg/L.
5. Experiments are carried out to learn the impact of environment factors on stability and sorption/desorption of the analytes. Accordingly, scientific basis for analyzing the behavior characteristics and controlling contamination of antibiotics in environment could be provided. In short time heating, TCs degrade partially and CAP does not decompose at all. It is showed that the cooking process can not remove the antibiotics in food which will enter into the human body and sewage. TCs are stable as the pH ranges from 2 to 8, and CAP is stable as the pH ranges from 1 to 10. It is indicated that TCs may be influenced by pH only a little and CAP may not be influenced by pH in aquatic environment, since the pH of surface water and groundwater is usually around 7. TCs in all three liquid medium degraded partially in six month and CAP nearly did not reduce at all. The result shows that TCs and CAP contamination may be persistent in environment to some extent. The sorption/desorption of TCs is greatly influenced by the particle diameter and CAP is not influence at all. It is proved that CAP tends to exist in water and TCs tends to exist in sediment. The sorption of TC and CTC gets stronger with the increasing concentration of CaCO3 in particle. It is proved that CaCO3 can increase the adsorbing of TC and CTC, which may provide a way to treat the antibiotic pollution in environment. |
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