三峡水库温室气体效应近年来备受关注.为揭示三峡水库典型支流澎溪河水-气界面CO2和CH4通量的昼夜动态规律,明晰短时间尺度下该水域温室气体释放的影响因素,在2010年6月至2011年5月的一个完整水文周年内,选择4个具有代表性的时段(2010年8、11月和2011年2、5月)对澎溪河高阳平湖水域开展昼夜跟踪观测.结果表明:2010年8、11月和2011年2、5月4次采样的CO2日总通量值分别为-8.34、73.94、28.13和-20.12 mmol/(m2·d),相应的CH4日总通量值分别为2.22、0.11、0.32和7.16 mmol/(m2·d),不同时期昼夜变化明显.研究水域CO2和CH4通量过程不具同步性:CO2昼夜通量变化可能更显著地受到水柱光合/呼吸过程的影响,但瞬时气象过程(水汽温差、瞬时风速等)在高水位时期亦可对CO2通量产生显著影响;CH4昼夜通量变化与水温条件改变更为密切.;There is a wide concern on the greenhouse gases emission due to dam construction in recent years. However, diel variation of reservoir greenhouse gases fluxes was seldom reported. To track the diel dynamics of greenhouse gases fluxes in the backwater area of the Pengxi River, Three Gorges Reservoir and elucidate the controlling factors of the fluxes, four 24-h monitoring-campaigns in Aug., Nov. of 2010 and Feb., May of 2011 were carried out in a whole reservoir operation year in Lake Gaoyang. We found that the daily total emission of CO2 were -8.34, 73.94, 28.13 and -20.12 mmol/(m2·d) in the above periods, respectively. While the fluxes of CH4 during these 4 monitoring campaigns were 2.22, 0.11, 0.32 and 7.16 mmol/(m2·d), respectively. The diel varied among the campaigns. The emission of CO2 and CH4 were showed to have different pathways for their asynchronous fluxes during the study. A correlation analysis revealed that photosynthesis and respiration in water column was a key controlling process for CO2 fluxes in this area. Furthermore, instantaneous meteorological parameters, i. e. wind speed, water-air temperature differences, were also significant factors that impact the fluxes of CO2 in high water level operation period of the reservoir. However, the variations of CH4 might be regulated by water temperature changes.
三峡工程举世瞩目，是长江流域大保护与流域水安全保障的关键性枢纽工程。自2003年三峡工程蓄水以来，在防洪、发电、航运、供水等方面产生了巨大的经济、社会及生态环境等综合效益。同时，水库建成后，重庆至宜昌600多km的自然河道变成了人为控制的大型河流型深水水库，不仅在库区形成了诸如消落带、干-支流往复交融的独特生境，而且由于下泄水流、泥沙、营养盐等水文及生物地球化学要素的时空变化，长江中、下游河床冲淤及演变均出现了一些新特征，江-湖关系也变得比2003年之前更加错综复杂，长江流域迎来了“后三峡工程”时代。为了阶段性系统总结、交流这20年来三峡水库生态环境效应研究的成果，《湖泊科学》编辑委员会特邀我们组织了本专辑。自2022年4月发布征稿启示以来，先后收到各类来稿60余篇，经过多轮审稿，最终25篇得以录用发表。 专辑不少研究成果都数据翔实、针对性强，体现了当下我国三峡工程生态环境效应研究的水平。(1)在水文水资源方面，不仅总结了长江中下游干流及两湖的径流泥沙变化，而且研究改进了三峡入库洪水概率预报方法，尤其是针对工程运用后三峡水库泥沙淤积及长江中下游河床调整、河道冲刷、航道水深资源等方面更是有多篇论文刊发。(2)在水环境水生态方面，对水动力、水沙变化引起的生态环境效应进行了系统的归纳和分析，并对水库消落带土壤-植物-微生物作用下的氮循环关键过程研究进行了系统回顾；研究认为，目前的水库富营养化及潜在的水华风险主要在支流，但是对干、支流浮游植物生长增殖的因果响应也要积极关注。(3)在流域生物多样性保育方面，专辑重点关注了消落区植物群落演变及优势植物适应策略、后三峡工程时代的鄱阳湖湿地植被生产力演变以及水库库尾江段产漂流性卵鱼类早期资源等。(4)在流域水安全方面，有论文针对库湾水-气界面热交换过程及水体稳定性进行了分析；我们高兴的发现，模拟分析揭示了三峡水库成库以来的气候效应主要集中在局地和近地层，而不是区域性的，这一研究成果无疑具有积极和深远的意义。(5)作为我国最大的水库，其温室气体排放及对“碳中和”“碳达峰”的贡献研究，无疑也引起了国内外学者的积极和长期关注，专辑中对水库CO2、CH4通量监测分析研究进行了系统回顾与展望，这也将是未来三峡水库的研究热点之一。 这是《湖泊科学》近10年来策划出版的第4个专辑。专辑不在多而在于精，未来我们还将持续关注三峡水库，长期跟踪、重点报道后三峡工程时代长江流域水资源、水生态、水环境、水安全方面的研究成果，更好的为长江大保护和我国水生态文明建设服务。;The Three Gorges Project is a key pivotal hydro-project in the Yangtze River Basin for the protection and security of water resources, which has been attracting worldwide attention over the past decades. Since the impoundment of the Three Gorges Reservoir in 2003, the project has created great economic, social, and ecological benefits in terms of flood control, hydropower generation, navigation, and water supply. Meanwhile, the reservoir formation has drastically transformed the 600km natural river reach of Yangtze, from Chongqing to Yichang, to a large river-valley dammed reservoir with deep water regulated by the dam. Such has created unique landscapes and habitats within the reservoir, e.g., drawdown area along the shorelines, reciprocal fluctuating backwater water area between tributaries and the main stem, etc. In addition, the regulation of the reservoir discharge also leads to new patterns of spatiotemporal variations of hydrological and biogeochemical parameters, e.g., sediment transport, fluvial equilibrium of downstream channels, nutrient exports, etc. The river-lake relationships in the mid and lower reach of the Yangtze have been becoming more complex than before 2003. The Yangtze River basin is now in a post-Three-Gorges-Project era. To summarize the state of research on the ecological and environmental effects caused by the Three Gorges Reservoir in the past 20 years, the editorial board of the Journal of Lake Sciences invited us to organize this special issue. The call for papers was announced in April 2022. Since then, more than 60 manuscripts have been received, and after extensive reviews, 25 of them were finally accepted for publication. The manuscripts collected in the special issue are informative and relevant, representing the knowledge-of-the-art of the ecological and environmental effects of the giant hydro-project in history. (1) In the area of hydrology and water resources, sediment transport in the mid and lower reaches of the Yangtze, as well as their exchange with the Dongting Lake and Poyang Lake, were elaborated. The special issue also collected novel methodologies for the flood prediction of the reservoir inflow, in particular, the fluctuation of a downstream riverbed after the operation of the Three Gorges Reservoir, as well as the situation of river scouring and channel depth variation, were extensively discussed. (2) In the area of water environment and aquatic ecology, the special issue systematically addressed the ecological and environmental effects caused by hydrological and hydrodynamic conditions. The important biogeochemical cycles of nitrogen within the soil-plant-microbial interactions in the reservoir drawdown area were also reviewed and discussed profoundly. It highlighted the tributaries of the Yangtze in the reservoir, exhibiting the trends of eutrophication, had potential risks of algal blooms. However, the causal chain of phytoplankton growth in the main stem and tributaries should also be taken into further attention. (3) In the area of watershed biodiversity conservation, the special issue collected manuscripts on the evolution of vegetation communities and adaptive strategies of dominant populations in the drawdown area. The evolution of vegetation productivity in the wetland of Poyang Lake was discussed. The research on drifting egg-producing fish populations was also included in the special issue. (4). In the watershed water security, manuscripts in the special issue discussed the air-water heat transfer process and thermal stability of the water column in the reservoir. Rather than regionally, we were delighted to find that modeling analysis revealed that the potential climatic effect caused by the project were mainly limited to the local scale or near-surface layer. Undoubtedly, this result seemed to be positive with considerable significance. (5) As China’s largest reservoir, greenhouse emissions from the reservoir have been the concern of academic communities, stakeholders, and policymakers, particularly about its potential contribution to China’s road to carbon neutrality. The special issue collected recent advances and outlooks on field monitoring and analysis of CO2 and CH4 fluxes in the reservoir. We believed that this would be a research hot spot shortly. This is the fourth special issue in the Journal of Lake Sciences over the past decade. It is not the number of manuscripts that counts but the quality of the research. In the future, we will continue to focus on the Three Gorges Reservoir, and report on the state of the research on hydrology, ecology, and environment and watershed water security in the Yangtze River Basin in the Post-Three-Gorges-Project era. These efforts will better serve the Great Protection Strategy of the Yangtze River and ecological civilization in China.
This paper constructs a model of the internal cross-sectional temperature field of power cables based on the multiphysics coupling simulation software, Comsol, to conduct an in-depth analysis of internal defects in power cables. First, a temperature field coupling model for power cables was built, and the accuracy of the simulation model was verified through mesh and boundary condition analysis. Subsequently, the distribution patterns of the internal temperature field of power cables were investigated under normal operating conditions and typical fault conditions (eccentric defects, internal water tree defects). The simulation results reveal that the presence of faults affects the insulation capability of the cables insulation layer, causing an imbalance in internal heat conduction and thus impacting the temperature distribution within the power cable. Additionally, this paper compares the internal temperature field distribution of power cables under different conditions (changing coil current and heat transfer coefficient) during normal operation. The results indicate that the temperature rise of power cables is closely related to the current carrying capacity and the heat transfer coefficient. Through an in-depth study of the temperature field distribution in power cables, this research provides a more precise, efficient, and economical reference solution for fault detection and repair in power systems, thereby enhancing the stability and safety of power cables and promoting the sustainable development of power cable technology.
On the basis of analyzing the present situation of medical China,a new monitor was introduced.The monitor can not only offer real-time display dripping speed,but also give an alarm in time in case of abnormality during the process of transfusion.The principle of the monitor and the software design are the focal points of our discussion.
Through a self-designed experimental device according to hydrodynamic conditions of backwater area of branch of Three Gorges Reservoir,the experiment was carried out to study the effects of reynolds number and turbulent flow on the vertical distributions of algae and its suspension and gathered behavior in different water depths.In the condition that water temperature is 20℃,illumination is 5000lx and there are enough nutrient concentrations in water,the experiment results showed that Cyanophyta cells are mainly in the depth ranging from 0.2m to 0.8m when average flow velocity is within 0-0.005m/s and reynolds number is within 0-1750 while Bacillariophyta cells are mainly in the depth ranging from 0.2m to 0.8m when average flow velocity is within 0.1-0.5m/s and reynolds number is within 35000-175000.Compared to Cyanophyta and Bacillariophyta,a considerable part of Chlorophyta cells could suspend in the depth ranging from 0.2m to 0.8m when flow velocity is within 0-0.05m/s and reynolds number is within 0-17500.
本文提出了两种原位培养装置(培养笼、培养桶)并采用这两种装置在澎溪河高阳平湖断面进行原位培养实验,旨在研究澎溪河典型优势藻的原位生长速率.研究期间主要生境特征为营养物丰足、光热条件优越、生境条件相对稳定,适宜于藻类生长,为水华形成的敏感期;在此期间代表CR型生长策略的湖北小环藻和兼具C、R、S生长策略的卵形隐藻的原位生长速率总体呈逐渐下降趋势,代表CS型生长策略的水华鱼腥藻和空球藻的原位生长速率则先增加后又有所下降,代表S型生长策略的铜绿微囊藻的原位生长速率虽然前期都为负,但总体呈现逐渐增加的趋势;并测得培养笼和培养桶中各藻种的最大比生长速率分别为湖北小环藻0.31、0.21 d-1;铜绿微囊藻0.09、0.03 d-1;空球藻0.16、0.42 d-1;水华鱼腥藻0.30、0.26 d-1;卵形隐藻0.49、0.95 d-1.本研究中,不同生长策略藻种生长速率的变化在一定程度上体现了不同生长策略藻种的生长趋势.另外,就装置性能实验及原位培养实验结果综合分析,认为两种原位培养装置均能够满足对天然水域藻类原位生长速率的测试要求,但装置的构造对藻类实际生长过程仍存在一定影响.;In situ growth rates of the typical dominant algae species in Pengxi River were investigated using two kinds of in situ incubation devices (incubation cage and incubation bucket) for field incubation experiment in Lake Gaoyang of Pengxi River. Adequate nutrients, superior solar-thermal and relatively stable hydrodynamic conditions are the main characteristic of the habitat during the study. The selected environment was suitable for the algal growth and the period chosen was sensitive for the occurrence of algal blooms. During this period, in situ growth rates of Cyllotella and Cryptomonas representing phytoplankton with CR and CRS growth strategies, respectively, were both gradually declined, and those of Anabaena and Eudorina which both represent the CS growth strategies increased firstly and then declined. The in situ growth rate of Microcystis which represents the S growth strategy was negative in early days, however, the general trend of growth rate was increased. The maximum specific growth rate of each species in the incubation cage and incubation bucket were Cyllotella hubeiana 0.31, 0.21 d-1, Microcystis aeruginosa 0.09, 0.03 d-1, Eudorina elegans 0.16, 0.42 d-1, Anabaena flos-aquae 0.30, 0.26 d-1, Cryptomonas ovata 0.49, 0.95 d-1, respectively. In this study, changes in the algae growth rates of the different growth strategies to a certain extent reflected the different growth trend. In addition, comprehensive analysis of the results of the performance test and in situ incubation experiment suggested that both of the two devices were able to meet the testing requirements of in situ growth rate of algae in natural water. There were potential impacts of the incubation devices on the in situ growth of phytoplankton.
We observed behavior response of overwintering Aythya baeri to different weather conditions by using fixed point-based observation and scanning sampling methods, at Henan Minquan National Wetland Park during November to December 2018. The results showed that, on sunny days, the dominant behaviors of A. baeri were resting, flying, and locomotion (65.5%), the second were foraging and maintaining (31.9%). The daily behavioral rhythm was foraging in the morning, resting at noon, and foraging and maintain in the afternoon. The flying usually occurred before the peak of foraging. The locomotion behavior was mostly accompanied by other behaviors, which positively associated with foraging and negatively correlated with resting. A. baeri increased resting and foraging in rainy days compared with that in sunny days. The dominant behaviors were resting, foraging and locomotion (76.5%), and maintaining and flying were the secondary (20.3%). The peaks of foraging and resting postponed to the evening, while the flying and maintaining were significantly decreased. Compared with the sunny days, the resting, foraging, locomotion and maintaining behaviors were increased in mist days, and flying was decreased. The peak of foraging delayed to the noon and afternoon, and that of resting postponed to the afternoon. The dominant behaviors were resting, locomotion and foraging (70.6%), while maintaining and flying behavior were the secondary (27.5%). In summary, there are variations in time allocation of A. baeri behaviors, activity rhythm and dominant behaviors due to the change of weather conditions during wintering. To overcome the bad weather conditions in rainy and mist days, A. baeri would allocate more time on foraging for increasing energy intake, and more resting time for reducing energy consumption.2018年11—12月在河南民权国家湿地公园,采用定点观察法、扫描取样法对越冬青头潜鸭在不同天气条件下的行为响应模式进行研究。结果表明: 在晴天,静息、飞行、运动是青头潜鸭越冬期的优势行为(65.5%),觅食、修整是次要行为(31.9%);行为节律表现为上午觅食、中午静息、下午觅食修整;飞行通常发生在觅食高峰前,运动行为多与其他行为相伴,其时间分配与觅食呈正响应,与静息呈负响应。相较于晴天,阴雨天青头潜鸭增加了对静息和觅食的时间分配,静息、觅食和运动为阴雨天的主要行为(76.5%),修整、飞行为次要行为(20.3%);觅食和静息的高峰时段后移,傍晚时达到高峰,飞行和修整时间显著减少。与晴天相比,雾霭天青头潜鸭静息、觅食、运动和修整的时间分配增加,飞行行为减少;觅食高峰后移至中午和下午,静息高峰后移至下午;静息、运动和觅食为雾霭天的优势行为(70.6%),修整和飞行为次要行为(27.5%)。研究表明,不同天气条件下,民权湿地公园青头潜鸭的越冬期行为在时间分配、行为节律、优势行为方面存在一定的响应;阴雨天和雾霭天青头潜鸭会分配更多的静息和觅食时间,并通过增加能量摄入和减少耗能行为应对恶劣天气。.
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