Characteristics, Spatiotemporal Changes and Surface Effects of Biofilm on Microplastics in Coastal Environment of the Yellow River Estuary

微塑料污染已成为仅次于气候变化的全球第二大环境问题，受到广泛关注。海岸带是受人类活动和气候变化双重影响的陆海交互作用地带，也是环境中微塑料的重要汇集区。国内外已有针对海岸带区域的微塑料污染研究，但大多研究是在海水环境介质中开展，缺乏海岸带环境中由陆到海的空间梯度上微塑料及其表面生物膜的长期原位暴露及动态变化研究。因此，本研究针对长期暴露于黄河口海岸带潮上带、潮间带和潮下带环境后，微塑料表面生物膜特征的时空动态变化及其对微塑料表面理化性质的影响，开展了（ 1）海岸带环境中微塑料表面生物膜形貌、总量和物理结构的时空动态变化；（ 2）海岸带环境中微塑料表面生物膜的微生物群落结构时空动态变化；（ 3）海岸带环境中微塑料表面生物膜形成与表面理化性质变化等方面的研究，取得的主要结果如下：（ 1）掩埋在海岸带不同区域的微塑料样品表面有多种微生物附着， 球菌和杆菌出现在大多数微塑料表面， 聚乙烯（ Polyethylene， PE） 薄膜表面以球菌为主， 聚丙烯（ Polypropylene， PP） 扁丝表面以杆菌为主。微塑料表面生物膜总量在空间上呈现出潮上带空气暴露处理最高的规律，在时间尺度上表现为夏季（ 12个月）高于冬季（ 18 个月）；对同一类型聚合物而言，尺寸对生物膜总量变化无显著效应；在不同类型聚合物间， PP 扁丝单位面积上生物膜总量更高。在结构分布上，潮上带微塑料的生物膜以菌体为主，潮间带和潮下带的生物膜以胞外多聚物（ Extracellular polymeric substances, EPS）为主；生物膜平均厚度在时间尺度上的变化与生物膜总量变化基本一致。（ 2）高通量测序结果表明，微塑料表面物种丰度从潮上带、潮间带至潮下带呈梯度递减，有少数潮上带、潮间带和潮下带环境中普遍存在且可以在微塑料表面定殖的物种。变形菌门（ Proteobacteria）、拟杆菌门（ Bacteroidete）和放线菌门（ Actinobacteria）是微塑料表面最主要的菌群，三类菌群在时间尺度上的变化规律并不显著，放线菌门则在空间尺度上有明显变化规律，呈潮上带、潮间带、潮下带梯度递减。潮上带地下部微塑料表面微生物与土壤微生物物种组成高度重叠，在聚合物类型间存在一定差异；潮间带和潮下带微塑料表面的微生物丰度介于沉积物与海水之间，其表面微生物主要来源于沉积物。微塑料与环境介质样本中微生物的物种丰度存在显著差异，潮下带微塑料表面的硫卵菌属（ Sulfurovum）和假单胞菌属（ Pseudomonas）丰度远高于海水和沉积物。（ 3）微塑料在黄河口潮上带、潮间带和潮下带等不同海岸环境中暴露 12 个月和 18 个月后，表面出现胞外多聚物的红外特征峰，理化性质也发生改变，出现风化痕迹。暴露于潮上带地上部的微塑料表面裂化现象和密度下降最为显著，除潮上带地上部外，微塑料密度随着暴露时间出现先增长后下降的趋势。潮上带和潮间带暴露微塑料疏水性仅在暴露初期出现下降，之后在时间上没有显著变化。所有野外暴露处理的微塑料表面均有羰基产生，且羰基指数呈潮上带 > 潮间带 >潮下带的趋势。综合微塑料的表面微形貌特征、密度、疏水性以及化学官能团（羰基指数）的动态变化等指标表明，黄河口潮上带地上部暴露的微塑料风化特征随时间变化最为显著。微塑料风化程度总体呈潮上带至潮间带、潮下带下降趋势，这一结果与微塑料表面生物膜总量的变化规律相一致。本学位论文的研究结果将为揭示海岸带环境中微塑料的生物风化过程提供科学依据，同时可应用于海洋微塑料污染监测需求方面

Weathering Characteristics of Microplastics of Low Density Polyethylene Film in the Coastal Environment of the Yellow River Estuary

【Objective】Microplastic pollution has become a global environmental issue that has caused widespread concern. Coastal zone is a region of land-ocean interaction under the dual impacts of global climate change and human activities. It is also an important sink for microplastics in the environment. However, by far little attention has been paid to long-term weathering characteristics of microplastics in coastal environments. In this study, microplastics of low density polyethylene(LDPE)film, which were commonly found in the coastal environments of the Yellow Sea and the Bohai Sea, were selected as the object for test in exploring long-term weathering characteristics of the microplastics in different coastal environments, including supratidal, intertidal and subtidal zones at the Yellow River Estuary. The aim of this study is to lay down a scientific basis for clarifying fates and effects of microplastics in the coastal environments. 【Method】Microplastics of LDPE film were left in the tidal zones for exposure to the coastal environment for 12 and 18 months. At the end of the each exposure period, they were retrieved for analysis of surface morphology, chemical functional groups(carbonyl index)and density with scanning electron microscopy, Fourier transform infrared spectrometry, and pycnometry. Weathering degree of the microplastics was characterized. 【Result】 Results show that after 18 months of exposure in the field, colonies of microorganisms were observed on the surface of the microplastics in all the zones and so were significant weathering characteristics. The microplastics in the supratidal zone exhibited the highest degree of cracking. Carbonyl groups were also observed on the surface of the microplastics regardless of where they were in, and in terms of carbonyl index of the microplastics, the three zones displayed an order of supratidal zone (0.28-0.81) > intertidal zone (0.18-0.22) > subtidal zone (0.16-0.20). The microplastics did not show much spatio-temporal variation in density. However, having been subjected to ultrasonic cleaning for removal of surface attachments, the microplastics exposed aboveground at the supratidal zone for 18 months were by (0.850.02 g·cm~(-3)) significantly lower than the untreated ones (0.930.03 g·cm~(-3)) in density.【Conclusion】The dynamic changes in morphological characteristics, chemical functional groups (carbonyl index) and density of the microplastics of LDPE film indicate that weathering degree of the microplastics varying with the tidal zone shows a declining order of supratidal zone > intertidal zone > subtidal zone, and the microplastics in the supratidal zone varied sharply with time in weathering characteristics. The microplastics in the coastal environment are subjected to physical, chemical and biological weathering, such as light, friction, chemical oxidation, and biodegradation. Among them, light-triggered photochemical oxidation may contribute the most to the weathering of microplastics. In the future, more attention should be paid to the research on potential environmental effects and fate of microplastics as affected by the complex environmental factors in the coastal environment

MG 400/951型采煤机截割部行星架时变可靠性分析

截割部行星架作为采煤机的关键零件，其时变可靠性对采煤机的综合性能有着重要的影响。基于Pro/E建立以截割部行星架为模态中性文件的采煤机刚柔耦合模型，研究截割部行星架的动力学性能，获得了截割部行星架薄弱区域和动态应力。基于Matlab获得了截割部行星架薄弱区域三参数威布尔分布的概率密度函数，利用Kstest函数验证其拟合的合理性。依据疲劳寿命可靠性理论，建立了截割部行星架疲劳寿命可靠性模型，计算得到基于Copula函数的截割部行星架多薄弱区域时变可靠度由0.936 2呈指数退化趋势，直至截割部行星架失效，结合可靠性灵敏度设计理论分析了截割部行星架多薄弱区域设计变量对其时变可靠性的影响程度，为截割部行星架的研究提供了理论基础和准确的数据支撑

The temporal and spatial distribution and surface morphology of atmospheric microplastics around the Bohai Sea

Microplastic pollution has become a key environmental issue. At present, research on microplastic pollution in the atmospheric environment has been carried out only in limited regions. Here, the long-term variation in atmospheric microplastic pollution in different coastal cities around the Bohai Sea was compared by selecting three coastal cities(Yantai, Tianjin and Dalian) as case studies. Atmospheric deposition samples were collected from June 2018 to May 2019. The particle size, color, micro-morphology and components of atmospheric microplastics were characterized by stereomicroscopy, scanning electron microscopy and μ-Fourier transform infrared spectrometry, and the atmospheric deposition flux of microplastics was also calculated. Four types of microplastics comprising fibers, films, fragments and granules were found in the atmospheric deposition samples at the three sampling sites and were dominated by fibers(>90%). The colors of microplastics were mainly transparent, blue, red, and black. Most microplastics were 50%) and polyester terephthalate(>30%). All the atmospheric microplastics showed definite surface weathering characteristics. The annual atmospheric deposition flux of microplastics at Yantai, Tianjin and Dalian were 2.7×10~4, 8.9×10~4 and 7.2×10~4 particles per square meter, respectively. The results may provide a scientific basis for investigation of atmospheric microplastic pollution and control in the coastal cities around the Bohai Sea

Surface properties and changes in morphology of microplastics exposed in-situ to Chinese coastal wetlands

Coastal wetlands are key areas of accumulation of microplastics. However, until now only a few studies have focused on the surface properties and morphological changes in microplastics in the real coastal wetland environment. Here, two typical biogeographic coastal soils, the Yellow River Estuary salt marsh wetland in the temperate zone and the Beibu Bay mangrove wetland in the subtropical zone, were selected for study. Polystyrene foams and polyethylene films were used and exposed within two coastal wetlands sites through in situ soil burial (underground exposure) and surface placement (above-ground exposure). The samples were sampled after 6, 12, 18 and 24 months of exposure to reveal the characteristics of the surface properties and morphological changes in microplastics in typical wetlands from the southern and northern biogeographic coastal zones. The surface morphology, microstructures and attached materials were observed using scanning electron microscopy using an energy dispersive spectrometer. Surface properties of the microplastics, i.e. the surface roughness, specific surface area, pore size distribution, functional groups and hydrophobicity, were analyzed by using atomic force microscopy, a surface area analyzer, a mercury porosimeter, Fourier transform infrared spectrometry and a contact angle meter. The surface morphology of the polystyrene foams in the Beibu Bay mangrove wetland exhibited more pits and holes than those in the Yellow River Estuary salt marsh wetland. The polystyrene foams exposed aboveground in the Beibu Bay mangrove wetland showed embrittlement and exfoliation after 18 months, while those exposed underground did not show such features. The specific surface areas of the polystyrene foams and the polyethylene films in the Yellow River Estuary salt marsh wetland were higher than those in the Beibu Bay mangrove wetland. The pore distributions on the surfaces of the two microplastic types mainly comprised macropores and mesopores. However, the porosity of the polyethylene film in the Yellow River Estuary salt marsh wetland was slightly higher than in the Beibu Bay mangrove wetland. The porosities in both regions were higher than in the original control samples. In terms of carbonyl index, rates of change in the Yellow River Estuary salt marsh wetland were higher than those in the Beibu Bay mangrove wetland. The surface hydrophobicity of the polyethylene film in the two regions declined with increasing exposure time. The changes in surface morphology of the polystyrene foams were more rapid than those in the polyethylene films, but the degree of change in specific surface area of the polyethylene films was greater than in the case of the polystyrene foams. It can be concluded that the surface properties and changes in morphology of microplastics in the coastal soil environment are related to multiple factors including the types and conditions of the wetlands, types of microplastics, exposure mode and exposure time. However, the specific mechanisms of these surface changes require further study. In summary, this study provides a scientific basis for research on the chemical processes of the micro-interfaces on the microplastic surfaces and environmental behavior and risk assessment of microplastics in the Chinese coastal zone

Prediction of Energy Resolution in the JUNO Experiment

International audienceThis paper presents the energy resolution study in the JUNO experiment, incorporating the latest knowledge acquired during the detector construction phase. The determination of neutrino mass ordering in JUNO requires an exceptional energy resolution better than 3% at 1 MeV. To achieve this ambitious goal, significant efforts have been undertaken in the design and production of the key components of the JUNO detector. Various factors affecting the detection of inverse beta decay signals have an impact on the energy resolution, extending beyond the statistical fluctuations of the detected number of photons, such as the properties of liquid scintillator, performance of photomultiplier tubes, and the energy reconstruction algorithm. To account for these effects, a full JUNO simulation and reconstruction approach is employed. This enables the modeling of all relevant effects and the evaluation of associated inputs to accurately estimate the energy resolution. The study reveals an energy resolution of 2.95% at 1 MeV. Furthermore, the study assesses the contribution of major effects to the overall energy resolution budget. This analysis serves as a reference for interpreting future measurements of energy resolution during JUNO data taking. Moreover, it provides a guideline in comprehending the energy resolution characteristics of liquid scintillator-based detectors

Determination of the number of ψ(3686) events taken at BESIII

The number of ψ(3686) events collected by the BESIII detector during the 2021 run period is determined to be (2259.3±11.1)×106 by counting inclusive ψ(3686) hadronic events. The uncertainty is systematic and the statistical uncertainty is negligible. Meanwhile, the numbers of ψ(3686) events collected during the 2009 and 2012 run periods are updated to be (107.7±0.6)×106 and (345.4±2.6)×106, respectively. Both numbers are consistent with the previous measurements within one standard deviation. The total number of ψ(3686) events in the three data samples is (2712.4±14.3)×10^