Physiological effects of tetracycline antibiotic pollutants on non-target aquatic Microcystis aeruginosa

This study aimed to evaluate the aquatic toxicity of three typical tetracycline antibiotics, including tetracycline, oxytetracycline, and chlortetracycline, on the cyanobacterium Microcystis aeruginosa. The cell density, chlorophyll a content, protein content, and enzymatic antioxidant activities were determined. The results showed that the cell growth was significantly inhibited by the three compounds at a low concentration. The chlorophyll a and protein content decreased significantly after exposure to 0.05 mg L^?1 of each compound for 9 d. When exposed to 0.2–1 mg L^?1 of tetracycline, the superoxide dismutase (SOD) activity increased, but peroxidase (POD) and catalase (CAT) activities decreased. In contrast, when exposed to oxytetracycline and chlortetracycline at different concentrations ranging from 0.2 to 1 mg L^?1 and from 0.01 to 0.05 mg L^?1, the SOD activity decreased, but the POD and CAT activities increased. These findings indicate that tetracycline antibiotics influence cell growth and protein synthesis, and they also induce oxidative stress in M. aeruginosa at environmentally similar concentrations. Thus, this study may provide further insights into the toxic effects of tetracycline antibiotics and the controlled use of antibiotics.     

Adsorptive removal of antibiotics from water using magnetic ion exchange resin

The occurrence of antibiotics in the environment has recently raised serious concern regarding their potential threat to aquatic ecosystem and human health. In this study, the magnetic ion exchange(MIEX) resin was applied for removing three commonly-used antibiotics, sulfamethoxazole(SMX), tetracycline(TCN) and amoxicillin(AMX) from water.The results of batch experiments show that the maximum adsorption capacities on the MIEX resin for SMX, TCN and AMX were 789.32, 443.18 and 155.15 μg/m L at 25°C,respectively, which were 2–7 times that for the powdered activated carbon. The adsorption kinetics of antibiotics on the MIEX resin could be simulated by the pseudo-second-order model(R~2= 0.99), and the adsorption isotherm data were well described by the Langmuir model(R~2= 0.97). Solution p H exhibited a remarkable impact on the adsorption process and the absorbed concentrations of the tested antibiotics were obtained around the neutral p H.The MIEX resin could be easily regenerated by 2 mol/L Na Cl solution and maintained high adsorption removal for the tested antibiotics after regeneration. Anion exchange mechanism mainly controlled the adsorption of antibiotic and the formation of hydrogen binding between the antibiotic and resin can also result in the increase of adsorption capacity. The high adsorption capacity, fast adsorption rate and prominent reusability make the MIEX resin a potential adsorbent in the application for removing antibiotics from water.     

UiO-66/BiVO4复合光催化剂的制备及其对四环素的光解

通过两步溶剂热法成功制备了UiO-66/BiVO₄复合光催化材料,考察其对四环素（TC）的光催化降解性能.在模拟可见光下,当锆（Zr）：铋（Bi）物质的量投料比为2：1时,对TC的光解效果最好（85.8%）.对TC的总去除率分别比纯UiO-66和纯BiVO₄提高27.1%和23.5%,降解速率是纯BiVO₄的47.9倍.通过X射线衍射仪（XRD）、扫描电子显微镜（SEM）、X射线光电子能谱（XPS）、紫外可见漫反射（UV-vis DRS）等对所制备的纳米光催化剂进行结构、形貌、组成及光电性能表征分析.结果表明：UiO-66与BiVO₄紧密结合形成Ⅱ型异质结,复合材料性能的提升归因于比表面积的和光生载流子分离率的提升及孔隙结构的改善.     

New insights into FeS/persulfate system for tetracycline elimination: Iron valence, homogeneous-heterogeneous reactions and degradation pathways

In this study, complete tetracycline（TTC） and above 50% of total organic carbon（TOC） were removed by Fe S/PS after 30 min under optimized conditions. Although free radicals and high-valent iron ions were identified to generate in the process, the apparent similarity between intermediate products of Fe S/PS, Fe/PS, and UV/PS systems demonstrated that the degradation of TTC was due to sulfate radicals(SO₄^·-) and hydroxyl radicals（ ·OH）. Based on the reaction between free radi...     

水体中四环素类抗生素的去除技术研究进展

四环素类抗生素因其可以防治人类和动物由病菌引起的疾病,同时又能用作生长促进剂以加快动物生长,目前在国内外被大量使用。抗生素的使用甚至滥用对自然环境造成不容忽视的污染,并进一步对人类身体健康产生潜在危害。从常规处理、膜处理、化学氧化和吸附等角度讨论了国内外对四环素类抗生素去除技术的研究进展,为环境水体中四环素类抗生素污染的有效去除提供了方向。     

Novel synthesis of aluminum hydroxide gel-coated nano zero-valent iron and studies of its activity in flocculation-enhanced removal of tetracycline

A newly designed aluminum hydroxide gel-coated nanoscale zero-valent iron(AHG@NZVI)with enhanced activity and dispersibility of NZVI was successfully synthesized.The AHG@NZVI composite was synthesized via control of the surface AHG content.AHG@NZVI-1,AHG@NZVI-2 and AHG@NZVI-3 were prepared under centrifugal mixing speeds of 1000,2000 and 4000 r/min,respectively.The activity of AHG@NZVI was evaluated by its tetracycline(TC) removal efficiency.The effects of AHG content,pH value,reaction temperature,and presence of competitive anions on TC removal were investigated.TC could be removed by both adsorption and chemical reduction on AHG@NZVI-2(centrifugal speed 2000 r/min) in a short time with high removal efficiency(≥98.1%) at the optimal conditions.Such excellent performance can be attributed to a synergistic interaction between aluminum hydroxide gel and NZVI:(1) AHG could enhance the stability and dispersity of NZVI;(2) aluminum hydroxide gel could absorb a certain amount of TC and Fe~(2+)/Fe~(3+),which facilitated the mass transfer of TC onto the NZVI surface,resulting in acceleration of the reduction rate of TC by the AHG@NZVI composite;and(3) AHG-Fe~(2+)/Fe~(3+)could absorb a certain amount of TC by flocculation.The kinetics of TC removal by AHG@NZVI composite was found to follow a two-parameter pseudo-first-order model.The presence of competitive anions slightly inhibited the activity of AHG@NZVI systems for TC removal.Overall,this study provides a promising alternative material and environmental pollution management option for antibiotic wastewater treatment.     

Preparation and photocatalytic performance study of dual Z-scheme Bi2Zr2O7/g-C3N4/Ag3PO4 for removal of antibiotics by visible-light

At present, the high re-combination rate of photogenerated carriers and the low redox capability of the photocatalyst are two factors that severely limit the improvement of photocatalytic performance. Herein, a dual Z-scheme photocatalyst bismuthzirconate/graphitic carbon nitride/silver phosphate (Bi₂Zr₂O₇/g-C₃N₄/Ag₃PO₄ (BCA)) was synthesized using a co-precipitation method, and a dual Z-scheme heterojunction photocatalytic system was established to decrease the high re-combination rate of photogenerated carriers and consequently improve the photocatalytic performance. The re-combination of electron-hole pairs (e⁻ and h⁺) in the valence band (VB) of g-C₃N₄ increases the redox potential of e⁻ and h⁺, leading to significant improvements in the redox capability of the photocatalyst and the efficiency of e⁻-h⁺ separation. As a photosensitizer, Ag₃PO₄ can enhance the visible light absorption capacity of the photocatalyst. The prepared photocatalyst showed strong stability, which was attributed to the efficient suppression of photo-corrosion of Ag₃PO₄ by transferring the e⁻ to the VB of g-C₃N₄. Tetracycline was degraded efficiently by BCA-10% (the BCA with 10 wt.% of AgPO₄) under visible light, and the degradation efficiency was up to 86.2%. This study experimentally suggested that the BCA photocatalyst has broad application prospects in removing antibiotic pollution.     

固定化厌氧微生物处理四环素废水的研究

采用PVA－硼酸法固定化微生物作为两相厌氧工艺中的产甲烷相,进行了四环素废水的处理试验,并与一般UASB产甲烷相进行了比较。结果表明固定化微生物产甲烷相具有较高的污泥活性和抗冲击负荷能力,其COD去除率达65％～75％,高于一般UASB反应器,且具有较高的污泥活性和抗冲击负荷能力。      

DNA damage and biochemical toxicity of antibiotics in soil on the earthworm Eisenia fetida

DNA damage and changes in enzyme activities were used as biomarkers to evaluate the genotoxicity and oxidative stress of tetracycline and chlortetracycline on the earthworm Eisenia fetida. The results showed that both antibiotics induced significant genotoxicity on earthworms in a dose-dependent manner (p < 0.01) with chlortetracycline having a stronger effect than tetracycline in the short term. The tests on the activities of superoxide dismutase (SOD) and catalase (CAT) enzymes further indicated biochemical stresses induced by the antibiotics. An N-shaped activity pattern was noted with the enzyme activities being stimulated first, then inhibited, and stimulated again with increasing concentration. The induced activity of SOD or CAT could scavenge oxygen free radicals and protect the organisms against oxidative stress by alleviating the corresponding DNA damage. Compared to enzyme activities, DNA damage as a biomarker was more sensitive and is thus more suitable for detecting low concentration exposure and diagnosing the genotoxicity of contaminants in terrestrial environment.     

Detection of antibiotic resistance and tetracycline resistance genes in Enterobacteriaceae isolated from the Pearl rivers in South China

This study investigated antibiotic resistance profiles and tetracycline resistance genes in Enterobacteriaceae family isolates from the Pearl rivers. The Enterobacteriaceae isolates were tested for susceptibility to seven antibiotics ampicillin, chloramphenicol, ciprofloxacin, levofloxacin, sulphamethoxazole/trimethoprim, tetracycline and trimethoprim. In Liuxi reservoir, with an exception to ampicillin resistant strains (11%) no other antibiotic resistance bacterial strains were detected. However, multiple drug resistance in bacterial isolates from the other sites of Pearl rivers was observed which is possibly due to sewage discharge and input from other anthropogenic sources along the rivers. Four tetracycline resistance genes tet A, tet B, tet C and tet D were detected in the isolates from the rivers. The genes tet A and tet B were widely detected with the detection frequencies of 43% and 40% respectively. Ciprofloxacin and levofloxacin resistant enteric bacteria were also isolated from the pig and duck manures which suggest a wider distribution of human specific drugs in the environment. This investigation provided a baseline data on antibiotic resistance profiles and tetracycline resistance genes in the Pearl rivers delta.