【作者】 程宏；

【导师】 陈荣；

【作者基本信息】 厦门大学 ， 环境科学， 2022， 硕士

【摘要】 受人类活动影响,海洋环境中微塑料(Microplastics,MPs)与抗生素抗性基因(Antibioticresistance genes,ARGs)污染日趋严重。微塑料在环境中会经历长期老化,吸附各类污染物,并能富集ARGs甚至致病菌,威胁水生生物和人类健康。目前少有研究关注到不同种类微塑料在长时间老化后的表面特征以及ARGs富集的变化。本研究调查了福建省九龙江河口不同站位水体、沉积物中的微塑料与ARGs污染的分布情况。通过现场实验探究了不同材质微塑料在沿九龙江河口3个盐度梯度的沉积物环境中老化1个月后,其表面微生物的组成和ARGs丰度的变化特征;选取7种材质微塑料,在天然海水中老化8周、16周后,分析其表面特征变化以及ARGs的富集过程,并研究微塑料粒径、材质以及形态对ARGs富集的影响。本研究所取得的主要结果为:(1)九龙江河口 5个站点采集到的沉积物与水样测定结果显示,该河口主要的ARGs种类为四环素类抗性基因如tetG与磺胺类抗性基因sul2。水相中ARGs的丰度分布与盐度呈显著负相关关系,且表层水ARGs丰度高于亚表层水,沉积物中没有发现类似规律。九龙江水相与沉积物中的微塑料分布均呈现沿河向入海口丰度递减趋势,丰度范围分别为2～66 items/L、8～85 items/kg d.w.,聚丙烯(Polypropylene,PP)、聚苯乙烯(Polystyrene,PS)、聚乙烯(Polyethylene,PE)是检测到微塑料的主要材质,85%以上的粒径在1000 μm以下,颜色丰富但黑、蓝、透明微塑料占多数。(2)将4种微塑料在九龙江河口 3个盐度梯度沉积物中老化1个月后,各站点微塑料表面ARGs丰度没有显著差异,但优势ARGs种类差异显著。16S rDNA测序结果表明与沉积物和水相相比,微生物表面优势菌群更加丰富,一些在水和沉积物中占比不高的细菌在微塑料表面得以富集,如厚壁菌门、拟杆菌门、变形菌门等,从而形成自身更加独特的微生物群落,其中PE的生物膜组成最为丰富。此外,从代谢功能分布来看,微塑料表面生物菌群代谢通路表达程度也更高,进一步证明微塑料生物群落与环境介质微生物群落的差异性。(3)经过8周、16周的老化,7种微塑料中,有PE、PS、聚己二酸(Poly-butyleneadipate-co-terephthalate,PBAT)和聚乳酸(Polylactic acid,PLA)4 种微塑料表面出现了新的特征峰或特征峰增强的现象,集中在1475～1000 cm-1与3750～3000 cm-1波段,老化时间越长,特征峰强度越大。与原始微塑料相比,老化8周的微塑料表面ARGs丰度均显著升高。但16周后,绝大部分微塑料上ARGs相对丰度出现明显降低。测定的7种ARGs中,四环素类抗性基因tetG是检测到的丰度最高的ARGs。微塑料的粒径、材质对ARGs的富集产生影响,粒径越小所富集的ARGs浓度越高,PS和PP对ARGs的富集能力最强。值得注意的是,Nylon和可降解微塑料PLA、PBAT上ARGs的变化,老化16周后,7种微塑料中只有Nylon上ARGs相对丰度上升,而PBAT和PLA上ARGs达到最低,尤其是PLA。此外,微塑料表面富集的一类整合子基因(Class I integrons,intl1)与ARGs之间有显著正相关关系,说明其表面基因交换较为频繁。综上,九龙江河口微塑料与ARGs污染呈现一定的空间分布特征,上游水相与沉积物中污染更为严重。在不同盐度的沉积物环境中暴露后,微塑料与环境样本间、同种微塑料之间微生物群落以及ARGs组成差异明显。微塑料的性质、停留的时间都会影响其老化过程以及表面ARGs富集。本文探讨了微塑料在水相和沉积物环境中的行为,为近海海洋环境中微塑料的环境风险评估提供科学依据。更多还原

【Abstract】 Microplastics(MPs)and antibiotic resistance genes(ARGs)are increasingly contaminated in the marine environment due to human activities.Microplastics undergo long-term aging in the environment,adsorbing various pollutants and enriching ARGs and even pathogenic bacteria,threatening aquatic organisms and human health.Few studies have focused on the surface characteristics of different types of microplastics and the changes of ARGs enrichment after prolonged aging.In this study,we investigated the distribution of microplastics and ARGs contamination in water bodies and sediments at different stations in the Jiulong River Estuary,Fujian Province.The surface characteristics of microplastics and the abundance of ARGs were investigated by field experiments after aging for 1 month in sediments with 3 salinity gradients along the Jiulong River Estuary.7 types of microplastics were selected and aged in natural seawater for 8 and 16 weeks to analyze the changes of surface characteristics and the enrichment of ARGs,and to study the effects of particle size,material and morphology of microplastics on the enrichment of ARGs.The effects of particle size,material and morphology on the enrichment of ARGs were also investigated.The main results obtained in this study were:(1)The sediment and water samples collected from five stations in the Jiulong River Estuary showed that the main ARGs species in the estuary were tetracycline resistance genes such as tetG and sulfonamide resistance genes sul2.The abundance distribution of ARGs in the aqueous phase showed a significant negative correlation with salinity,and the abundance of ARGs in surface water was higher than that in subsurface water,while no similar pattern was found in the sediment.The distribution of microplastics in both the aqueous phase and sediment of Jiulong River showed a decreasing trend of abundance along the river to the estuary,with the abundance ranges of 2-66 items/L and 8～85 items/kg d.w.,respectively.Polypropylene(PP),polystyrene(PS),polyethylene(PE)were the main materials detected,more than 85%of the particle size was below 1000 μm,and the color was rich but black,blue and transparent microplastics were the majority.(2)After aging the four microplastics in three salinity gradient sediments of the Jiulong River Estuary for 1 month,there was no significant difference in the abundance of ARGs on the surface of microplastics at each site,but the difference in the dominant ARGs species was significant.16S rDNA sequencing results showed that the dominant microbial surface flora was more abundant compared with the sediment and water phase,and some bacteria that were not highly represented in water and sediment were enriched on the surface of microplastics.Some bacteria that were not high in water and sediment were enriched on the surface of microplastics,such as firmicutes,bacteroidetes,proteobacteria,thus forming their own more unique microbial communities,of which PE had the most abundant biofilm composition.In addition,from the distribution of metabolic functions,the metabolic pathways of microplastic surface biota were also expressed to a higher extent,further demonstrating the differences between microplastic biota and environmental media microbial communities.(3)After 8 and 16 weeks of aging,four of the seven microplastics,PE,PS,polybutylene-adipate-co-terephthalate(PBAT)and polylactic acid(PLA),showed new characteristic peaks or enhanced characteristic peaks on their surfaces,concentrated at the longer the aging time,the greater the intensity of the characteristic peaks.Compared with the original microplastics,the abundance of ARGs on the surface of microplastics aged for 8 weeks was significantly higher.However,after 16 weeks,the relative abundance of ARGs on the vast majority of microplastics showed a significant decrease.Among the seven ARGs measured,tetG was the most abundant ARGs detected.Particle size and material of microplastics influenced the enrichment of ARGs,with the smaller the particle size,the higher the concentration of enriched ARGs,PS and PP had the strongest enrichment ability for ARGs.It is worth noting that changes of ARGs on Nylon and degradable microplastics PLA and PBAT.After 16 weeks of aging,the relative abundance of ARGs increased only on Nylon among the seven microplastics,while ARGs reached the lowest on PBAT and PLA,especially on PLA.In addition,the enrichment of one class of integrons(class Ⅰ integrons,intl1)on the surface of microplastics and ARGs were not significant.Intl1 was significantly positive correlated with ARGs,indicating that the gene exchange on its surface was more frequent.In conclusion,microplastics and ARGs pollution in the Jiulong River Estuary showed certain spatial distribution characteristics,with more serious pollution in the upstream water phase and sediments.After exposure in sediment environments with different salinities,the microbial communities and the composition of ARGs differed significantly between microplastics and environmental samples and between microplastics of the same species.The nature of the microplastics,the residence time can affect the aging process and the enrichment of ARGs on the surface.This paper explores the behavior of microplastics in aqueous and sediment environments to provide a scientific basis for environmental risk assessment of microplastics in the offshore marine environment.更多还原