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题名:
海岸环境中微塑料对土霉素的吸附分配特征研究
其他题名: Adsorption and Partition Characteristics of Oxytetracycline by the Microplastics in Coastal Environments
作者: 周阳1,2
学位类别: 硕士
答辩日期: 2016-05-23
授予单位: 中国科学院大学
授予地点: 北京
导师: 章海波
关键词: 微塑料 ; 土霉素 ; 表面性质 ; 吸附解吸 ; 滨海潮滩
学科分类: 环境科学
学位专业: 环境科学
中文摘要:  微塑料和抗生素已成为海洋及海岸环境中一类新型污染物而受到全球关注。微塑料是指粒径在5 mm以下的毫米级或微米级塑料碎屑,是最容易被生物体摄食的粒径范围。近海地区养殖垃圾的随意堆置、生活和工业污水排放等是导致微塑料污染的主要原因。同时,随着养殖业的发展以及污水排放的加剧,近岸海域的抗生素污染及抗性基因的传播也成为新的海岸环境污染问题。因此,微塑料作为载体对抗生素类化学污染物在海岸环境中的富集与扩散成为微塑料污染研究中的关注焦点之一。本研究在对我国海岸环境中受养殖活动影响的河口及潮滩地区的微塑料与抗生素污染调查的基础上,选择潮滩风化聚苯乙烯发泡微塑料、树脂颗粒和微珠颗粒为典型微塑料类型,以土霉素为目标抗生素,通过批平衡吸附试验、吸附动力学和等温吸附模型等系统地研究了微塑料对土霉素的吸附行为及机理,并结合水沙侵蚀试验、光照老化试验、胡敏酸包覆试验以及野外风化样品的对比研究,探讨了不同海岸环境条件下微塑料表面性质的改变及其对土霉素吸附的影响,为揭示海岸环境中微塑料严重污染情况下抗生素的迁移转化机制提供理论依据,也为微塑料和抗生素复合污染的控制提供基础数据。论文的主要研究结论如下:
(1)通过对海岸环境中受养殖活动影响的河口及潮滩地区微塑料与抗生素污染的调查研究发现,聚苯乙烯发泡类微塑料是主要的微塑料类型之一,同时在一些地区树脂颗粒也有较高的丰度。抗生素污染在河口沉积物中普遍检出,其中喹诺酮类和四环素类抗生素检出率高,土霉素是主要的抗生素污染物,最高检出浓度达到4695 μg/kg。
(2)不同聚合物类型的树脂及微珠颗粒对土霉素的吸附动力学均存在快速吸附和慢吸附两个阶段,两者对土霉素的吸附行为均符合准一级动力学模型,但微珠颗粒达到吸附平衡的时间更快。树脂颗粒对土霉素的吸附受聚合物类型的影响更明显,其中橡胶体结构的聚乙烯(PE)树脂颗粒对土霉素的吸附能力最强,吸附机理为多层非线性吸附,聚氯乙烯(PVC)对土霉素的结合能力最弱,吸附机理为单层饱和吸附;微珠颗粒由于比表面积普遍大于树脂颗粒,其对土霉素的吸附能力普遍高于相同聚合物类型的树脂颗粒,受到聚合物类型的影响要小于树脂颗粒。
(3)潮滩风化聚苯乙烯发泡微塑料对土霉素的平衡吸附量是未风化聚苯乙烯发泡微塑料的4倍多,表明聚苯乙烯发泡微塑料经过潮滩长期风化后能显著增加对土霉素的吸附量;Freundlich模型均能很好的拟合潮滩风化与未风化聚苯乙烯发泡微塑料对土霉素的等温吸附曲线,表明聚苯乙烯发泡微塑料表面对土霉素的吸附以非线性的多层吸附为主。静电作用是控制聚苯乙烯发泡微塑料对土霉素吸附的主要机制,当pH=5时对土霉素的吸附量达到最大,此时土霉素分子与聚苯乙烯发泡微塑料表面的静电排斥作用最小。同时,离子间竞争作用亦会影响聚苯乙烯发泡微塑料对土霉素的吸附,但Ca2+与土霉素络合形成桥键作用会增加微塑料表面对土霉素的吸附,特别是未风化聚苯乙烯发泡微塑料表面对土霉素的吸附。
(4)聚乙烯(PE)和聚丙烯(PP)树脂颗粒经过海水沙侵蚀后表面粗糙度增加,对土霉素吸附结合能力要高于淡水沙侵蚀和光照老化处理;聚氯乙烯(PVC)树脂颗粒经过光照老化处理后,色度转变为暗黄色,表面氧化特征明显,对土霉素的吸附结合能力要高于海水沙侵蚀和淡水沙侵蚀;同时海水沙侵蚀、淡水沙侵蚀和光照老化处理后的PVC树脂颗粒对土霉素的吸附均要强于未做表面处理的PVC树脂颗粒。胡敏酸包覆聚苯乙烯发泡微塑料后对土霉素的饱和吸附量增加,表明在环境中微塑料表面生物膜的附着可能会增加对土霉素的吸附与结合。
(5)海水盐度对潮滩风化聚苯乙烯发泡微塑料吸附土霉素的影响要比对未风化聚苯乙烯发泡微塑料的更大。可溶性有机质对微塑料吸附土霉素总体表现为促进作用;相同腐殖酸浓度下,胡敏酸对促进微塑料吸附土霉素的作用要强于富里酸。
英文摘要:  Microplastics and antibiotics have been of concerned globally as emerging pollutants in the marine and coastal environments. Microplastics are defined as the plastic pieces with the size less than 5 mm, which is similar to the food size range of the zooplankton in ocean and is easily subjected to be ingested. The origins of microplastics in the coastal environment are mainly sourced from wastes of aquaculture, sweage sludge discharge from the industries and domestics. Meanwhile, pollutions of antibiotics and antibiotics resistance gene were also caused by the development of aquaculture and wastewater discharge. Therefore, microplastics has been of great concerned because they could be a vector to accumulating and diffusing chemical pollutants like antibitics in the coastal environments. Several types of microplastics including weathered expanded polystyrene styrofoam, resin pelltes and microbeads were selected as the typical microplastics and oxytetracycline was selected as the target antibiotics based on a field survey for microplastics and antibiotics pollutions in the coastal beaches and estuarine sediments. The batch equilibrium adsorption experiments, adsorption kinetic and isotherm models were employed to study the adsorption and desorption mechanisms of oxytetracycline in the different microplastics. Microplastics treated with erosion by sand and water, photoradiation aging and humic acid coating were used to explore the effects of different coastal circumstances on the suface modifications of the microplastics and their impacts on the adsorption of oxytetracycline. The purposes of this study are to provide a scientific basis for the migration and transformation of antibiotics under the severe pollution of microplastics as well as provide a basic dataset for the controling of the combined pollution of microplastics and antibiotics in the coastal environments. The major conclusions of the study are shown as following:
(1)A field survey for the microplastic and antibiotic pollution in the coastal environment showed that the expanded polystyrene styrofoam (EPS) was one of the most abundant microplastic types in the coastal beaches impacted by aquacultural activities, followed by the resin pellets which has a high abundance in some hotspots. Several types of antibiotics were detected in the estuarine sediment surrounding the Bohai Sea. Among the detected antibiotics, tetracyclines and quinolone were the two dominated antibiotics in the sediments and the concentration of oxytetracycline as one of the tetracyclines was the highest on average and the highest concentration was detected 4695 μg/kg.
(2)The adsorptions of oxytetracycline on the resin pellets and microbeads were all following the order of rapid adsorption and slow adsorption subsequently. And the adsorption was in accordance with the pseudo-first order kinetic model for both microplastics. However, the adsorption of microbeads for the oxytetracycline reached equilibrium faster than the resin pellets. The oxytetracycline adsorption on the resin pellets with different polymer types was significant different. The rubber-based Poly Ethylene (PE) resin pellets have the strongest adsorption for oxytetracycline among the 6 polymer types and multilayer nonlinear adsorption might be the main adsorption mechanism. While the polyvinyl chloride (PVC) resine pellets has the lowest adsorption due to the limitation of monolayer adsorption. The adsorption capacity of the microbeads is generally higher than that of the resin pellets with the same polymer type as a result of higher specific surface area of the microbeads than the pellets. The adsorption of microbeads is less affected by the polymer types than the resin pellets.
(3) The equilibrium adsorption capacity of the beached EPS microplastics for the oxytetracycline is over four times of the virgin EPS microplastics, which indicated the increased adsorption of EPS microplastics for the oxytetracycline after weathering in the beaches. The adsorption isotherms of the weathered and the virgin microplastics were both fitted well with the Freundlich model, which implied the nonlinear multilayer adsorption of oxytetracycline on the surface of the EPS microplastics. Electrostatic interactions mainly governed the adsorption of oxytetracycline on the EPS microplastics. The adsorption capacity of oxytetracycline reached the maximum at pH of 5 at which the electrostatic repulsion was the lowest. Meanwhile, ion competitions affected the adsorption of oxytetracycline on the both weathered and virgin microplastics. However, the bridging effect of Ca2+ with oxytetracycline increased the adsorption of oxytetracycline on the microplastic, and such an effect was more prominent in the virgin microplastics.
(4) The surface roughness of PE and PP resin pellets increased after the seawater-sand erosion and their adsorptions for oxytetracycline were higher than the water-sand erosion and photoradiation aging. The PVC resin pellets changed from transparent to dark yellow after photoradiation aging, which indicated the surface oxidation of the pellets. The adsorption capacity of the aged PVC for oxytetracycline was higher than that of the erosion treatments. Meanwhile, the adsorption was higher in the surface modified PVC pellets than in the untreated PVC pellets. A significant increase of oxytetracycline adsorption could be found in the EPS microplastics coated with humic acid which was one of the main components of biofilm frequently found in the surface of microplastics in environments. This implied that biofilm formed on the surface of the microplastics in the coastal environments might increase the adsorption and binding of oxytetracycline.
(5) The effect of seawater salinity on the oxytetracycline adsorption was more prominent in the weathered EPS microplastics than in the virgin ones. The dissolved organic matter promoted the oxytetracycline adsorption by EPS microplastics in gerneral. And the effect of humic acid on adsorption was stronger than that of fulvic acid under the same concentration.
 
Key Words:Microplastic, oxytetracycline, surface properties, adsorption and desorption, coastal beaches
 
内容类型: 学位论文
URI标识: http://ir.yic.ac.cn/handle/133337/22005
Appears in Collections:中科院烟台海岸带研究所知识产出_学位论文

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作者单位: 1.中国科学院烟台海岸带研究所
2.中国科学院大学

Recommended Citation:
周阳. 海岸环境中微塑料对土霉素的吸附分配特征研究[D]. 北京. 中国科学院大学. 2016.
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