典型抗生素在环境中的浓度分布及其降解机理研究

STUDY ON CONCENTRATION DISTRIBUTION AND DEGRADATION MECHANISM OF TYPICAL ANTIBIOTICS IN THE ENVIRONMENT

孙婧

11649180

硕士

环境工程

郑春苗

2018-05-28

2018-07-09

哈尔滨工业大学

深圳

抗生素是一种用于预防细菌感染的抗微生物药物，长期排放的以低浓度形式存在于环境中的抗生素会对非目标生物产生毒害作用，导致细菌产生耐药性，并会诱导抗性基因（ARGs）的生成，其在环境中的积累已经给生态系统和人类健康带来巨大的危害，且目前对抗生素的去除尚无有效的降解手段。中国是全世界抗生素生产量和使用量最大的国家，其中珠江流域是全国抗生素使用量，排放量，排放密度最高的地区，深圳地处珠江三角洲前沿，是中国经济中心城市，然而深圳市对抗生素的浓度分布研究还很匮乏。本研究对深圳市主要河流及相应底泥中普遍使用的20 种抗生素的浓度分布进行调查，同时对高污染的茅洲河沉积物样品中ARGs和细菌群落的分布模式进行研究，以探究抗生素，ARGs 和微生物群落之间的相关性。鉴于对目前抗生素的污染现状尚无较好的降解方法，因此在研究深圳市抗生素的污染分布基础上，选取恩诺沙星（ENR），培氟沙星（PEF）和磺胺喹恶啉（SQX）进行光降解研究并检测其残留的毒性。主要结果如下：对深圳市主要河流及相应底泥中抗生素的浓度分布调查表明：采集的河流和相应沉积物的62 个样品中，磺胺嘧啶（SDZ）和磺胺噻唑（STZ）的在河水中浓度范围分别为3.160 ng·L-1 - 219.767 ng·L-1 和0.124 ng·L-1 - 113.288 ng·L-1，在底泥中浓度均值分别为397.766 ng·g-1 和139.168 ng·g-1，分别是水和沉积物中的主要抗生素污染物，与其他抗生素相比，对藻类风险最高。此外，发现sul1 基因是沉积物样品中最丰富的ARGs，与高浓度的SDZ 和STZ 一致。统计分析表明，bla_d 基因，梭状芽孢杆菌和磺胺甲恶唑之间呈正相关。对ENR，PEF 和SQX 的光降解研究发现：ENR，PEF 和SQX 在纯水溶液在UV 照射3h 后，分别只降解了72.17 %，46.61%，89.44%。但是加入H2O2 和Fe2+可以有效地降解三种抗生素。在UV/H2O2 体系下，ENR，PEF 和SQX 的降解率随着H2O2 浓度的增加逐渐增大，但存在一个最优值，即当加入的H2O2 浓度分别达到20 mM，20 mM，5 mM 时，有最大的降解率，均可以达到90%，随着H2O2 浓度的继续增加会出现抑制作用。在UV/Fe2+体系下，ENR，PEF 和SQX 的降解率随着Fe2+浓度的增加逐渐增加，当加入的Fe2+的浓度分别为0.25 mM，10 mM，1mM 时，降解率达到最大，3h 可降解84.27%，33.82%，100%，然而，当Fe2+的浓度继续增大时，降解受到抑制。在UV/H2O2/Fe2+体系下，酸性条件有利于抗生素的降解，当pH=3 时，ENR，PEF 和SQX 可分别降解100%，79.11%和100%。毒理实验表明：在浓度分别为1g·L-1，1g·L-1 和4mg·L-1 的ENR，PEF 和SQX 的纯抗生素溶液中，斑马鱼胚胎全部死亡，可见三种抗生素对斑马鱼胚胎的毒性都很强，且对斑马鱼有致畸作用；在UV/H2O2/Fe2+体系下，ENR 降解4h 的降解产物对斑马鱼胚胎无致毒效应，在166h 时孵化率为100%；PEF 和SQX 各个降解时间下斑马鱼胚胎虽然均全部死亡，但在降解时间分别为0.5h 和15h 时，斑马鱼胚胎全部死亡所对应的时间最长，分别为118h 和32h。综上所述：深圳市水体及底泥中抗生素污染较为严重，ARGs 在环境中广泛分布，表明需要进一步地研究这些ARGs 在环境中的繁殖机制及其与微生物群落相关的风险。针对目前高浓度抗生素污染现状，鉴于还没有有效的降解手段，因此选取ENR，PEF 和SQX 三种抗生素进行光降解研究，在AOPs 的不同的反应体系下，ENR，PEF 和SQX 的降解率情况如下：UV/H2O2/Fe2+( pH=3) > UV/H2O2 > UV/H2O2 >UV，即在UV/H2O2/Fe2+且pH=3 时降解效果最好。在实际水体中抗生素的浓度一般为ng·L-1 - μg·L-1 级别，因此AOPs 降解抗生素是一种安全有效的，矿化难降解有机物程度较高的处理手段。该研究不仅为深圳市水污染问题和全国抗生素的污染情况提供基础数据，还可为污水处理厂用紫外降解抗生素提供可靠的技术支撑。

Antibiotics are a kind of antimicrobial drug used to prevent bacterial infection.Long-term discharge of low-level antibiotics can have a toxic effect on non-targetorganisms, which may result in bacterial resistance and induction of antibiotic resistancegenes (ARGs). Its accumulation in the environment have posed tremendous potential risks to the ecosystem and human health, while currently there is no effective techinique to degrade antibiotics. China has the largest amount of antibiotic production and usage among the whole world, the Pearl River Basin has the highest antibiotic manufacture, emissions and concentrations around China. As Shenzhen, one of the most populous city in China, locates in the forefront of the Pearl River Delta However, the study of the concentration distribution of antibiotics in Shenzhen is still rare. This study investigated the concentration distribution of 20 commonly used antibiotics in major rivers and corresponding sediments in Shenzhen, and also studied the distribution patterns of ARGs and bacterial communities in sediment samples from the highly polluted Maozhou River to explore the correlation among antibiotics, ARGs and microbial communities. In view of the current state of pollution of the current antibiotic pollution, there is no good degradation method. Then, based on previous study of the distribution of antibiotic pollution in Shenzhen, we selected enrofloxacin (ENR), pefloxacin (PEF) and sulfaquinoxaline (SQX) to photodegrade and examine the toxicity of their remnants. The main results are as follows:The investigation of the concentration distribution of antibiotics in major rivers and sediments in Shenzhen shows that: In the 62 samples, we found that sulfadiazine (SDZ) and sulfathiazole (STZ), in the water with concentrations ranging from 3.160 ng·L-1 to 219.767 ng·L-1 and 0.124 n ·L-1 to 113.288 ng·L-1, and in the sediments with mean values 397.766 ng·g-1 and 139.168 ng·g-1, respectively. They were dominant antibiotic pollutants in both water and sediment, and posed high risk to algae compared with other antibiotics. Furthermore, the sul1 gene was found to be the most abundant ARG in sediment samples, consistent with the high concentrations of SDZ and STZ. Statistical analysis indicated a positive correlation among the bla_d gene, Fusobacteria, and sulfamethoxazole, suggesting that antibiotics may be positively linked to the expression of ARGs in certain bacteria, and thus high reproduction would occur within the bacterial community.The photodegradation studies of ENR, PEF and SQX found that: the pure aqueous solutions of ENR, PEF and SQX were degraded by 72.17%, 46.61%, and 89.44% respectively after 3 h of UV irradiation. However, the addition of H2O2 and Fe2+ can effectively degraded three antibiotics. Under the UV/H2O2 system, the degradation rates of ENR, PEF and SQX increased with the increase of H2O2 concentration, but there was an optimal value, when the concentration of added H2O2 were 20 mM, 20 mM, 5 mM respectively, the mechanism has the maximum degradation rates, which can reach 90 percent. The inhibitory effect would appear as the H2O2 concentration continue to increase. Under the UV/Fe2+ system, the degradation rates of ENR, PEF and SQX increased gradually with the increase of Fe2+ concentration. When the concentration of added Fe2+ is 0.25 mM, 10 mM, 1 mM respectively, the degradation rate reached the maximum, which were 84.27%, 33.82%, 100% at 3 h. However, when the concentration of Fe2+ continued to increase, it suppress the degradation. In the UV/H2O2/Fe2+ system, acidic conditions favored the degradation of antibiotics. When pH is 3, ENR, PEF and SQX can degraded to 100%, 79.11% and 100%, respectively. Toxicological experiments showed that in pure antibiotic solutions of ENR, PEF and SQX at concentrations of 1 g·L-1, 1 g·L-1, and 4 mg·L-1, respectively, the zebrafish embryos all died. It suggested the three antibiotics are fatal to zebrafish embryos and have toxicity effects on zebrafish; in UV/H2O2/ Fe2+ system, the degradation product of ENR after 4 had no obvious effect on survival rate. The hatchability was 100% at 166 h. the zebrafish embryos died at all degradation time of PEF and SQX, but when the degradation time were 0.5h and 15h, the survival time of the zebrafish embryos was the longest, which were 118 hours and 32 hours, respectively.In summary, this study shows that the pollution of antibiotics in water bodies and sediments in Shenzhen is relatively serious, and ARGs are widely distributed in the environment. Therefore, it is necessary to furtherly study the reproductive mechanisms of these ARGs in the environment and the risks associated with microbial communities. In view of the wide usage of antibiotics and their low degradability, there are no effective methods for antibiotics degradation, ENR, PEF, and SQX antibiotics were selected for photodegradation studies. In the different reaction systems of AOPs, the ranking of degradation rates of ENR, PEF and SQX are as follows: UV/H2O2/Fe2+ (pH=3)> UV/H2O2 > UV/Fe2+ > UV, that is, UV/H2O2/Fe2+ and pH=3 mechanism is more efficient. Therefore, AOPs is a safe and effective method for degrading antibiotics, and the degradative products have a low toxicity and a high degree of treatment of mineralized refractory organics. This study not only lend several basic data to solve Shenzhen's water contamination problem, but also provides a reliable technical support for the use of UVdegrading method in sewage treatment plants.

抗生素 抗性基因 微生物群落 高级氧化法 降解产物 毒性

antibiotic resistance genes microbial community advanced oxidation process degradation products toxicity

中文

联合培养

哈尔滨工业大学

孙婧. 典型抗生素在环境中的浓度分布及其降解机理研究[D]. 深圳. 哈尔滨工业大学,2018.