塑料污染在自然环境中的广泛分布已经引起了各国学者和公众的关注，并与气候变化、海洋酸化和栖息地破坏并列为重大全球环境问题。环境中的塑料残体在物理、化学和生物过程的作用下，破碎成更小的颗粒，根据其粒径可划分为大型塑料（>25 mm）、中型塑料（5-25 mm）和微塑料（<5 mm）。海洋塑料可以通过缠绕或被摄食对海洋生物造成伤害，尤其是微塑料，因其与浮游生物等饵料生物的粒径相似，容易被海洋生物摄入，从而对海洋生物造成物理伤害或化学危害。因此，开展近海环境中塑料污染负荷、特征、溯源、微塑料在生物体内的累积及生态效应研究，对科学认识海洋生态系统中塑料污染赋存、迁移、归趋及其生态风险评估等具有重要科学意义。

本研究以渤海环境介质和常见鱼类为研究对象，通过研究辽东湾、渤海湾、莱州湾和渤海中部的表层水体、沉积物和鱼类体内塑料（大型塑料、中型塑料和微塑料），尤其是微塑料的污染水平，揭示塑料在渤海不同环境介质中的污染水平、空间分布、迁移及其在各介质之间的赋存关系，解析微塑料在常见鱼类体内的污染特征以及影响鱼类摄入微塑料的生态因素。主要结论如下：

1. 渤海表层水体中塑料污染分布广泛，但存在空间差异。整个海区中塑料的平均丰度为0.93 items m^-3（总计7953个），其中微塑料的平均丰度为0.79 items m^-3（总计6866个），塑料污染处于中等水平。辽东湾的塑料（2.29 items m^-3）或微塑料（1.95 items m^-3）的污染水平显著高于其他三个海区（0.34 ~ 0.67 items m^-3或0.26 ~ 0.59 items m^-3）。辽东湾海域较高的塑料污染水平，主要来源于辽东半岛高度集中和发达的农业、工业、渔业和海洋工程活动产生的塑料废弃物。同时，较弱的水交换能力和距离渤海海峡较长的距离不利于塑料的扩散，增加了其在海区的滞留时间，从而增加了该海域的塑料丰度。大型塑料（0.10 items m^-3）和中型塑料（0.04 items m^-3）的丰度远远低于微塑料的丰度（0.79 items m^-3），但在四个海域之间无显著差异。微塑料的主要形状为碎片（75.1%）、泡沫（12.0%）和线型（7.4%）；主要颜色为透明（36.9%）、白色（29.1%）和蓝色（20.0%）；平均粒径为1.56 mm，粒径分布范围为0.31 ~ 4.99 mm之间，小粒径（<1 mm）颗粒在微塑料中占比为34.8%；聚合物类型以醇酸树脂（AR，29.3%）、聚乙烯（PE，26.4%）、聚苯乙烯（PS，25.6%）和聚丙烯（PP，17.8%）为主。

2. 渤海表层沉积物中塑料的平均丰度为52.05 items kg^-1 d.w.（总计141个），微塑料的平均丰度为48.88 items kg^-1 d.w.（总计137个），在四个海区间无显著差异（41.10 ~ 67.73 items kg^-1 d.w.），河口区是塑料累积的热点区域。与国内外的研究相比，渤海沉积物的塑料污染丰度处于中等偏下的水平。沉积物中微塑料的主要形状为纤维（53.3%）和碎片（41.6%）；颜色以蓝色（26.3%）、透明（22.6%）、黑色（17.5%）和白色（11.7%）较为常见；粒径分布在0.03 ~ 4.89 mm之间，平均粒径为0.84 mm，小粒径颗粒（<0.5 mm）占绝大多数；聚合物类型以人造丝（RY，37.2%）和纤维素（CE，21.8%）为主。沉积物中塑料的污染水平与人类活动、河流输入、海流和潮汐等因素相关。

3. 渤海表层水体和沉积物中微塑料特征相似性较低，说明其空间分布的相关性较低。两种环境介质中微塑料的丰度和粒径均无显著相关性；其微塑料的聚合物、形状和颜色的相似度系数较低，分别为0.16、0.29和0.38；就四个海区而言，微塑料的特征相似性系数相差较大，各海区中微塑料的聚合物、形状和颜色相似性系数的范围分别为：0.11 ~ 0.22、0.26 ~ 0.33和0.27 ~ 0.77。微塑料在两种介质中的时空分布的不匹配、水动力等环境动力作用以及它们在环境中的归趋行为差异等会导致两种介质中微塑料的相关性偏低。

4. 全部鱼种均检测出塑料（总计704个），塑料的检出频率为54.7%；以微塑料为主（总计679个），微塑料的检出率为53.4%。鱼类体内塑料和微塑料的丰度分别为（1.0 ± 1.2 items ind.^-1和0.9 ± 1.2 items ind.^-1）、（0.1 ± 0.1 items g^-1和0.1 ± 0.1 items g^-1）和（0.1 ± 0.1 items cm^-1和0.1 ± 0.1 items cm^-1）。鱼体内微塑料的检出率（25.0% ~88.9%）或单位个体丰度（0.3 ~ 1.8 items ind.^-1）因种类而异。鱼体内检出的微塑料形状以纤维（82.2%）为主；颜色以蓝色（50.8%）、黑色（19.4%）和灰色（15.6%）为主；聚合物类型以RY（42.3%）和CE（35.2%）为主；粒径分布在0.03 ~ 4.99 mm之间，平均粒径为1.08 mm，以<0.5 mm的颗粒占优势。除粒径外，鱼类体内微塑料的其他特征与环境介质中的微塑料特征组成并不一致。

在四个海域内采集的鱼类体内的微塑料检出率在51.2% ~ 60.0%之间；中上层鱼类体内微塑料的检出率（56.1%）高于底层鱼类（51.9%）；空胃鱼类和摄食鱼类体内微塑料的检出率分别为51.7%和55.2%；定居性鱼类体内微塑料的检出率（56.5%）高于洄游性鱼类（49.5%）；但以上因素，即海域、栖息水层、摄食状态和迁移习性对鱼类体内微塑料的检出率和单位个体丰度无统计学上的显著影响。而不同食性鱼类体内的微塑料检出率或丰度均差异显著，依次为小型中上层滤食性鱼类（62.1%，1.2 items ind.^-1）>大型底栖捕食性鱼类（54.4%，1.0 items ind.^-1）>中小型底栖生物食性鱼类（50.5%，0.8 items ind.^-1）>大型中上层捕食性鱼类（40.3%，0.7 items ind.^-1）。这与鱼类的捕食策略相关，中小型上层滤食性鱼类通过滤食大量海水获取浮游生物饵料，加之它们栖息的表层水域微塑料的丰度较高，在滤食过程中能够直接从自然环境中摄入较多微塑料，导致鱼类体内较高的微塑料污染水平。

鱼类体内塑料/微塑料的粒径与其体长之间均无显著相关性。鱼类单位个体微塑料丰度与其体长、体重和营养水平之间均无显著相关性；单位体重微塑料的丰度与营养级之间无显著的相关关系，表明微塑料在渤海食物网的营养级水平上无显著累积传递或生物放大效应。

综上所述，塑料污染广泛分布于渤海环境介质和常见鱼类体内。渤海表层水体中塑料污染存在空间异质性，辽东湾塑料/微塑料污染水平显著高于渤海湾、莱州湾和渤海中部；辽东湾较高的塑料污染水平与农业、工业、渔业和海洋工程等活动密切相关，同时水交换能力差和距离渤海海峡较长也增加了塑料的累积水平。渤海表层沉积物中塑料/微塑料丰度相对均一，河口区是微塑料累积的热点区域。渤海表层水体和沉积物中微塑料的空间分布相关性较低，这与微塑料在两种介质中时空分布的不匹配、水动力等环境动力作用以及它们在环境中的归趋行为差异有关。超过半数的鱼类个体检测出塑料/微塑料，鱼类体内微塑料的丰度水平与捕食策略相关；微塑料在渤海食物网水平上无显著的生物累积效应。研究结果可为揭示塑料污染在渤海生态系统中的来源、行为和归趋，以及评估微塑料在食物网传递累积和生态效应提供科学依据。

The widespread of plastic pollution in the natural environments has attracted much attention from both scholars and general public. And plastic debris has been recognized as a global threat to the environments, together with other environmental problems such as climate change, ocean acidification and habitat destruction. Large plastic items are brittle and tend to break down into small pieces as a result of various physical, chemical and biological processes. According to their size, plastics in the aquatic environments are generally divided into three groups: macroplastics (>25 mm), mesoplastics (5-25 mm) and microplastics (<5 mm). Large plastics can entangle and injure marine organisms. Particularly, microplastics are readily available for ingestion by biota because they pose high similarity in morphology and size to zooplankton, the prey of many organisms. This would cause physical threats or chemical toxicity to the consumers or predators. Therefore, knowledge about the pollution load, distribution and characteristics of plastics in the environment media and organisms is of great significance to better understanding their occurrence, behavior, and source tracing. Furthermore, the knowledge is essential for assessing the ecological risk of plastic pollution in marine environments.

The present study focuses on the investigation of the pollution status of plastics (macro-, meso- and microplastics) in the surface water, sediments and fish in the Bohai Sea (Liaodong Bay, Bohai Bay, Laizhou Bay and Central Bohai Sea). Based on the data of the abundance, spatial distribution and morphology (shape, color, size and polymer) of the plastics, their transfer behavior and relationship between the two environmental media is investigated. Spatial variation of the plastics is assessed from the perspectives of sources (e.g., influx) and transfer behavior of the plastics, ocean hydraulic forces and oceanography in the four regions of the Bohai Sea. Plastic pollution in fish is studied from the aspects of pollution load in fish and the ecological factors that may affect their intake of plastics, such as the feeding and living habits of fish. Trophic transfer and bioaccumulation of plastics in the food web is also assessed. The following main conclusions are reached.

1. Plastics are widely distributed in the surface water and their abundance of plastics considerably vary in terms of spatial distribution across the sea. The average abundance of plastics in the entire water is 0.93 items m^-3 (7953 in total), and the abundance of microplastics is 0.79 items m^-3 (6866 in total), which is at a moderate level compared with the plastics in other oceans. Both plastics (2.29 items m^-3) and microplastics (1.95 items m^-3) are more abundant and show more diverse characteristics in Liaodong Bay than in the other three regions (0.26-0.59 items m^-3 and 0.26-0.59 items m^-3, respectively). Plastic wastes from highly concentrated and developed agricultural, industrial, fishery and ocean engineering activities around Liaodong Bay make large contributions to the microplastics in this region. Additionally, low hydrodynamics and long distances to the Bohai Strait are unfavorable for the diffusion of particles, facilitating the retention of particles and increasing their abundance in this bay. Macroplastics (0.10 items m^-3) and mesoplastics (0.04 items m^-3) are far less abundant and show less diverse characteristics than microplastics but do not significantly differ among the four regions of the sea. Fragments (75.1%), foams (12.0%) and lines (7.4%) are the dominant shapes among the microplastics. Transparent (36.9%), white (29.1%) and blue (20.0%) particles dominate among the microplastics. The average size of the microplastics is 1.56 mm (0.31-4.99 mm) with small particles (<1 mm) predominating among the microplastics. Alkyd resin (AR, 29.3%), polyethylene (PE, 26.4%), polystyrene (PS, 25.6%) and polypropylene (PP, 17.8%) are the predominant polymers in the microplastics.

2. The average abundances of plastics and microplastics in the surface sediments of the Bohai Sea are 52.05 items kg^-1 d.w. (141 in total) and 48.88 items kg^-1 d.w. (137 in total), respectively, which are not significantly different among the four regions (41.10-67.73 items kg^-1 d.w.). The abundance of the microplastics near the estuary areas is relatively abundant compared to other regions of the Bohai Sea. The plastic abundance in the surface sediments of the entire area is at a medium-low level in comparison with other oceans. In terms of shape composition of the microplastics, fibers (53.3%) are the most dominant particles, followed by fragments (41.6%). Blue (26.3%), transparent (22.6%), black (17.5%) and white (11.7%) particles are the most common types by color. The average size of microplastics is 0.84 mm (0.03-4.89 mm), with the particles less than 0.5 mm being the most dominant microplastics. Rayon (RY, 37.2%) and cellulose (CE, 21.8%) dominate the microplastics particles in the sediments by polymers. The abundance and distribution of microplastics in the sediments are considerably affected by anthropogenic activities, river input and ocean hydraulic forces such as currents and tides in the regions.

3. Neither the abundance nor the size of the microplastics is proportionally correlated with low similarity indexes of the characteristics of microplastics in the surface water and sediments. The similarity indexes of the polymer, shape and color of the microplastics in the two environmental media are 0.16, 0.29 and 0.38, respectively. The similarity indexes of microplastics characteristics in the four sea areas are different, which are 0.11-0.22, 0.26-0.33 and 0.27-0.77 by polymer, shape and color, respectively. This could be caused by the mismatch in the spatiotemporal distribution and variation in the characteristics, fate and behavior of microplastics in the two media.

4. Plastic particles (704 in total) are detected in all the 22 fish species with an average detection rate of 54.7% in the Bohai Sea. Most of the plastics are microplastics (679 in total) with a detection rate of 53.4%. The abundances of plastics and microplastics by individual fish, mass and length of fish are 1.0 ± 1.2 items ind.^-1 or 0.9 ± 1.2 items ind.^-1, 0.1 ± 0.1 items g^-1 or 0.1 ± 0.1 items g^-1, and 0.1 ± 0.1 items cm^-1 or 0.1 ± 0.1 items cm^-1, respectively. The detection rate (25.0-88.9%) or abundance (0.3-1.8 items ind.^-1) in the fish varies with species. Fibers (82.2%) are the most prevalent microplastics in shape and blue (50.8%), black (19.4%) and grey (15.6%) particles are the dominant microplastics in color. RY (42.3%) and CE (35.2%) dominate the microplastics by polymer. The average size of the microplastics is 1.08 mm (0.03-4.99 mm) with particles <0.5 mm dominating the microplastics. The composition of morphological characteristics or chemical components (polymer) of the microplastics detected in the fish is not consistent with those of the microplastics in the two environmental media.

The detection rate of microplastics in the fish range from 51.2% to 60.0% across the four regions. The detection rates of microplastics in the fish in terms of ecological or functional groups are following: pelagic fishes (56.1%) > demersal fishes (51.9%); feeding fish (55.2%) > fish with empty stomachs (51.7%); local coastal fish (56.5%) > migratory fishes (49.5%). However, the above factors (region, living habitat, feeding status and moving habit) do not show statistically significant influences on the detection rate or abundance of the microplastics in the fish. Contrastingly, significant differences in detection rate or abundance of microplastics occur among the fish of different feeding habits, in an order of small and medium pelagic fishes (62.1% or 1.2 items ind.^-1) > large benthic predatory fishes (54.4% or 1.0 items ind.^-1) > small and medium-sized benthic predatory fishes (50.5% or 0.8 items ind.^-1) > large pelagic predatory fishes (40.3% or 0.7 items ind.^-1). Foraging strategy of fish may partly account for the differences in the intake of microplastics by fish of different feeding habits. For instance, pelagic filtering fish usually take the plankton prey by filtering large amount of surface seawater, in which microplastics are commonly more abundant than in other water columns. This could make it possible for the pelagic filtering fish to ingest more microplastics directly from the environments during feeding and breathing than others, leading to higher levels of plastic pollution level in these feeders.

The size of the plastics/microplastics in the fish is not significantly correlated with fish length. The abundance of microplastics by individual fish is not significantly correlated with fish length, mass or trophic level, either. And the relative abundance of microplastics by fish mass is not significantly correlated to trophic level. These results indicate that microplastics may not show trophic transfer or bioaccumulation in food chains or webs in the Bohai Sea.

In conclusion, plastics are ubiquitous in environmental media and common fish of the Bohai Sea. In the surface water, the abundance of plastics considerably vary in terms of spatial distribution across the sea, and both plastics and microplastics are more abundant and show more diverse characteristics in Liaodong Bay than that in Bohai Bay, Laizhou Bay and Central Bohai Sea. Plastic wastes from agricultural, industrial, fishery and ocean engineering activities around Liaodong Bay make large contributions to the microplastics in this region. In addition, low hydrodynamics and long distances to the Bohai Strait increase the abundance in this bay. In the surface sediments, the average abundances of plastics and microplastics are not significantly different among the four regions, and the abundance of the microplastics near the estuary areas is relatively abundant compared to other regions. The spatial distribution of microplastics in surface water and sediments is relatively low, which is related to the mismatch in the spatiotemporal distribution and variation in the characteristics, fate and behavior of microplastics in the two media. Plastics/microplastics are detected in more than half of fish individuals, and the abundance of microplastics in fish is correlated with their foraging strategies. Microplastics may not show bioaccumulation in food chains or webs in the Bohai Sea. The results are expected to provide knowledge for assessing plastic pollution, tracing sources and understanding the behavior and destiny of plastics in the Bohai Sea, particularly the transfer behavior of microplastics between the two environmental media and organisms.

目  录

第1章  绪论... 1

1.1  海洋微塑料概况... 1

1.2  海洋环境中微塑料的分布特征... 6

1.2.1  微塑料在水体中的分布... 6

1.2.2  微塑料在沉积物中的分布... 8

1.2.3  微塑料在生物体中的分布... 9

1.3  中国近海微塑料研究现状... 11

1.4  研究意义与内容... 14

1.4.1  研究意义... 14

1.4.2  研究内容... 15

1.4.3  技术路线... 16

第2章  渤海表层海水中塑料污染特征... 17

2.1  材料与方法... 17

2.1.1  样品采集... 17

2.1.2  样品预处理... 18

2.1.3  微塑料的形态表征和鉴定... 18

2.1.4  质量控制... 19

2.1.5  数据分析... 19

2.2  结果... 19

2.2.1  塑料丰度和特征... 19

2.2.2  微塑料的丰度和空间分布... 25

2.2.3  微塑料特征... 25

2.3  讨论... 30

2.3.1  微塑料丰度和空间分布... 30

2.3.2  微塑料的特征和来源... 37

第3章  渤海表层沉积物中塑料污染特征... 41

3.1  材料与方法... 41

3.1.1  样品采集... 41

3.1.2  样品预处理... 42

3.1.3  微塑料的形态表征和鉴定... 42

3.1.4  质量控制... 42

3.1.5  数据分析... 42

3.2  结果... 42

3.2.1  塑料丰度和特征... 42

3.2.2  微塑料的丰度和空间分布... 47

3.2.3  微塑料特征... 48

3.2.4  环境微塑料的相似性... 50

3.3  讨论... 53

3.3.1  微塑料丰度和空间分布... 53

3.3.2  微塑料的特征和来源... 53

3.3.2  环境中微塑料的相似性... 58

第4章  渤海海域常见鱼类体内塑料污染特征... 63

4.1  材料与方法... 63

4.1.1  样品采集... 63

4.1.2  样品预处理... 64

4.1.3  微塑料的形态表征和鉴定... 66

4.1.4  微塑料在食物链上的营养转移... 66

4.1.5  塑料/微塑料的粒径与鱼类体长的关系... 66

4.1.6  质量控制... 66

4.1.7  数据分析... 66

4.2  结果... 67

4.2.1  渤海常见鱼类食性... 67

4.2.2  鱼类体内微塑料的丰度... 70

4.2.3  鱼类体内微塑料的特征... 78

4.2.4  小结... 91

4.3  讨论... 91

4.3.1  鱼类体内微塑料的丰度及影响因素... 91

4.3.2  微塑料特征... 95

4.3.3  微塑料在食物网上的累积效应评估... 103

第5章  结论与展望... 105

5.1  主要结论... 105

5.2  创新点... 107

5.3  展望... 107

参考文献... 111

致  谢... 133

作者简历及攻读学位期间发表的学术论文与研究成果... 135