卡里马塔海峡贯穿流与印尼贯穿流的相互作用     

李淑江  徐腾飞  孙俊川  杨丽娜  滕飞  王冠琳  王永刚 《海洋科学进展》2021,39(2):197-209

卡里马塔海峡贯穿流将中国南海的低盐水输运到爪哇海,与印度尼西亚贯穿流(印尼贯穿流)携带的西太平洋高盐水在印度尼西亚海(印尼海)交汇,二者通过混合、浮力强迫等过程相互作用.这改变了印度尼西亚海的水体热盐性质,影响局地海气交换和热带太平洋-印度洋之间的热盐交换.依据卡里马塔海峡、龙目海峡和望加锡海峡的实测表层海流数据,采用...  相似文献   

Streambed restoration to remove fine sediment alters reach‐scale transient storage in a low‐gradient fifth‐order river,Indiana, USA          下载免费PDF全文

Adam S. Ward  Jeffrey R. White  Todd V. Royer 《水文研究》2018,32(12):1786-1800

Hyporheic restoration is of increasing interest given the role of hyporheic zones in supporting ecosystem services and functions. Given the prevalence of sediment pollution to waterways, an emerging restoration technique involves the removal of sediment from the interstices of gravel‐bed streams. Here, we document streambed sediment removal following a large, accidental release of fine sediment into a gravel‐bed river. We use this as a natural experiment to assess the impact of fine sediment removal on reach‐scale measures of transient storage and to document the responses of reaches with contrasting morphology (restored vs. unrestored) to changing discharge one‐field season. We conducted a series of conservative solute tracer experiments in each reach, interpreting both summary statistics for the recovered in‐stream solute tracer time series. Additionally, we applied the transient storage model to interpret the results via model parameters, including a Monte Carlo analysis to measure parameter identifiability and sensitivity in each experiment. Despite the restoration effort resulting in an open matrix gravel bed in the restored reach, we did not find the significant differences in most time series metrics describing reach‐scale transport and transient storage. We hypothesize that this is due to enhanced vertical exchange with the gravel bed in the restored reach replacing lateral exchange with macrophyte beds in the unrestored reach, developing a conceptual model to explain our findings. Consequently, we found that the impact of reach‐scale removal of fine sediment is not measureable using reach‐scale solute tracer studies. We offer recommendations for future studies seeking to measure the impacts of stream restoration at the reach scale.  相似文献   

Simulation of less‐mobile porosity dynamics in contrasting sediment water interface porous media          下载免费PDF全文

Farzaneh MahmoodPoor Dehkordy  Martin A. Briggs  Frederick D. Day‐Lewis  Amvrossios C. Bagtzoglou 《水文研究》2018,32(13):2030-2043

Considering heterogeneity in porous media pore size and connectivity is essential to predicting reactive solute transport across interfaces. However, exchange with less‐mobile porosity is rarely considered in surface water/groundwater recharge studies. Previous research indicates that a combination of pore‐fluid sampling and geoelectrical measurements can be used to quantify less‐mobile porosity exchange dynamics using the time‐varying relation between fluid and bulk electrical conductivity. For this study, we use macro‐scale (10 s of cm) advection–dispersion solute transport models linked with electrical conduction in COMSOL Multiphysics to explore less‐mobile porosity dynamics in two different types of observed sediment water interface porous media. Modeled sediment textures contrast from strongly layered streambed deposits to poorly sorted lakebed sands and cobbles. During simulated ionic tracer perturbations, a lag between fluid and bulk electrical conductivity, and the resultant hysteresis, is observed for all simulations indicating differential loading of pore spaces with tracer. Less‐mobile exchange parameters are determined graphically from these tracer time series data without the need for inverse numerical model simulation. In both sediment types, effective less‐mobile porosity exchange parameters are variable in response to changes in flow direction and fluid flux. These observed flow‐dependent effects directly impact local less‐mobile residence times and associated contact time for biogeochemical reaction. The simulations indicate that for the sediment textures explored here, less‐mobile porosity exchange is dominated by variable rates of advection through the domain, rather than diffusion of solute, for typical low‐to‐moderate rate (approximately 3–40 cm/day) hyporheic fluid fluxes. Overall, our model‐based results show that less‐mobile porosity may be expected in a range of natural hyporheic sediments and that changes in flowpath orientation and magnitude will impact less‐mobile exchange parameters. These temporal dynamics can be assessed with the geoelectrical experimental tracer method applied at laboratory and field scales.  相似文献   

Testing a spatially distributed tracer‐aided runoff model in a snow‐influenced catchment: Effects of multicriteria calibration on streamwater ages          下载免费PDF全文

Thea I. Piovano  Doerthe Tetzlaff  Pertti Ala‐aho  Jim Buttle  Carl P. J. Mitchell  Chris Soulsby 《水文研究》2018,32(20):3089-3107

Integrating stable isotope tracers into rainfall‐runoff models allows investigation of water partitioning and direct estimation of travel times and water ages. Tracer data have valuable information content that can be used to constrain models and, in integration with hydrometric observations, test the conceptualization of catchment processes in model structure and parameterization. There is great potential in using tracer‐aided modelling in snow‐influenced catchments to improve understanding of these catchments' dynamics and sensitivity to environmental change. We used the spatially distributed tracer‐aided rainfall‐runoff (STARR) model to simulate the interactions between water storage, flux, and isotope dynamics in a snow‐influenced, long‐term monitored catchment in Ontario, Canada. Multiple realizations of the model were achieved using a combination of single and multiple objectives as calibration targets. Although good simulations of hydrometric targets such as discharge and snow water equivalent could be achieved by local calibration alone, adequate capture of the stream isotope dynamics was predicated on the inclusion of isotope data in the calibration. Parameter sensitivity was highest, and most local, for single calibration targets. With multiple calibration targets, key sensitive parameters were still identifiable in snow and runoff generation routines. Water ages derived from flux tracking subroutines in the model indicated a catchment where runoff is dominated by younger waters, particularly during spring snowmelt. However, resulting water ages were most sensitive to the partitioning of runoff sources from soil and groundwater sources, which was most realistically achieved when isotopes were included in the calibration. Given the paucity of studies where hydrological models explicitly incorporate tracers in snow‐influenced regions, this study using STARR is an important contribution to satisfactorily simulating snowpack dynamics and runoff generation processes, while simultaneously capturing stable isotope variability in snow‐influenced catchments.  相似文献   

植被发育斜坡非饱和带土体优先域及其对水分入渗的贡献——以云南省呈贡和昭通玄武岩质斜坡为例     

徐宗恒  徐则民  李凌旭 《地理科学》2017,37(5):783-791

为了全面得到植被发育斜坡非饱和带土体中优先域结构类型,以2个试验区5个玄武岩斜坡为研究对象,采用染色示踪试验揭示优先域的存在形式及其影响因素,并采用双环入渗试验对不同深度非饱和带土体渗透特征进行测定,揭示优先域对水分入渗的贡献。研究表明：植被发育斜坡非饱和带土体中优先域结构类型除了传统的植物根系腐烂后残留的通道、动物通道、土体干缩裂隙以外,还存在有根系-土体以及砾石-土体接触带空隙以及气候冻融交替产生的裂隙,其中植被根系对大孔隙的影响占主导地位;试验区斜坡非饱和带土体的饱和渗透速度随深度增加有降低的趋势,土体饱和渗透速度最大值高达513.6 mm/h（表层）;最小值13.33 mm/h,受广泛分布的优先域影响下形成的斜坡饱和带高渗透盖层对降水入渗的贡献是巨大的。  相似文献   

The Source System of Mesozoic Magmatism in Middle and Lower Yangtze Valleys and Adjacent Areas—A Geochemical Tracer Study     

马振东  单光祥 《中国地球化学学报》1997,16(2):105-111

The mechanism that controls regional mineralization must be governed by a series of geochemical reactions in relation to the source system of magmatism.In this respect,the geological bodies must have been overprinted by various kinds of tracers in terms of either chemical elements or isotopes.For this reason,the problem may be better approached by treating the lithosphere as a whole with due considerations given to the various tracer elements and isotopes and the various media of the magmatism(magmatic as well as sedimentary rocks).Presented in this paper are the results of this attempt based on a great wealth of available data concerning the source system of Mesozoic magmatism in the Middle and Lower Yangtze Valleys and adjacent areas.  相似文献   

水中荧光计在高混浊水域中的混合扩散实验应用     

夏达英  苗禄田  胡福辰  朱儒弟  边洪村 《海岸工程》1997,(2)

为了研究长江水域污染物质的输运和扩散规律，作者利用研制成功的水中荧光计在该水域进行了混合扩散实验。该仪器在高混浊水作中对罗丹明B的浓度检测范围为1×10－9～5×10-5g／cm3，精确度≤±10％。本文着重论述使用水中荧光计和荧光示踪染料在流速大、混浊度高的长江九江江段和镇江江段进行水体混合扩散测量实验的情况，结果令人满意，为我国的高混浊水体混合扩散实验研究提供了新的手段和方法。  相似文献   

利用放射性示踪沙定量观测长江口北槽航道抛泥区底沙运动   总被引：3，自引：0，他引：3  

李樟苏  程和森  曹更新  吴永进  杜效云  王守家  魏明成 《海洋工程》1994,(2)

１９９１年６月在国际原子能机构的合作下，在长江口北槽航道上抛泥区进行了一次大规模的放射性示踪沙试验。示踪核素为钪－４６，总活度为１７．９５×１０~（１０）Ｂｑ（４．８５Ｃｉ），示踪沙投放总量为４９５ｇ。本试验目的是通过定量观测底沙运移的方向、路线、速度和输沙率，以期为北槽航道上抛泥区今后能否继续作为抛泥区使用提供直观可靠论据。本次试验观测资料表明，在北槽航道上抛泥区，在中小讯期间，无论是涨潮时投放的示踪沙还是落潮时投放的示踪沙都受落潮流控制，并向北槽航道中段输移。据测量资料分析，在上口抛泥区投放的示踪沙最终沿着１１０°的运动方向以７５８ｍ／ｄ的运动速度，在２６９~＃航标附近进入挖槽，单宽输沙率为４７．８ｍ~３／ｍｄ。  相似文献   

Physical behavior of the SEEDS iron-fertilized patch by sulphur hexafluoride tracer release     

Daisuke Tsumune  Jun Nishioka  Akifumi Shimamoto  Shigenobu Takeda  Atsushi Tsuda 《Progress in Oceanography》2005,64(2-4):111

The first iron (Fe) – fertilization experiment in the western North Pacific was carried out using SF₆ to trace the Fe-fertilized water mass. A solution in 10,800 liters of seawater of 350 kg of Fe and 0.48 M of SF₆ tracer was released into the mixed layer over a 8 × 10 km area. On the first underway transects through the patch after the Fe release, we observed a significant increase of dissolved Fe (ave. 2.89 nM). The fertilized patch was traced for 14 days by on-board SF₆ analysis. A Lagrangian frame of reference was maintained by the use of a drogued GPS buoy released at the center of the patch. The patch moved westward at a rate of 6.8 km d⁻¹. Mixed layer depth increased from 8.5 to 15 m during the experiment. Horizontal diffusivity was determined by the change of SF₆ concentration in the patch. The horizontal diffusivity increased during the experiment. We evaluate here the fate of Fe in a Fe-fertilized patch using the dilution rate determined from sulphur hexafluoride (SF₆) concentration. Dissolved Fe concentrations subsequently decreased rapidly to 0.15 nM on Day 13. However, the dissolved Fe half-life of 43 h was relatively longer than in previous Fe-enrichment studies, and we observed a larger increase of the centric diatom standing stock and corresponding drawdown of macro-nutrients and carbon dioxide than in the previous studies. The most important reason for the larger response was the phytoplankton species in the western North Pacific. In addition, the smaller diffusivity and shallower mixed layer were effective to sustain the higher dissolved Fe concentration compared to previous experiments. This might be one reason for the larger response of diatoms in SEEDS.  相似文献   

Discharge Control on Boundary of Tidal Models and Measuring Techniques of Low Current Velocity     

Li Guochen Xu Jinhuan Associate Prof.  Dept. of Navigation  Ocean Eng.  Hohai University  Nanjing Lecturer  Dept. of Navigation  Ocean Eng.  Hohai University  Nanjing 《中国海洋工程》1992,(3)

This paper describes the discharge control technique on boundary used in two models, one is the model of hot water drainning in Dayawan Nyclear Power Plant, Guangdong, and the other is the model for trainhing the sand bar at the Guanhe Estuary, Jiangsu. Many years of application shows that this technique has the advantages of good reliability, repeatability and validity. The speedometer of hydrogen bubble is also introduced in this paper. The device can display and store tracing lines in a computer, and help operators to obtain the value and direction of transient velocity of a nonsteady current, thus, the problem of measurment of low current velocity in tidal model tests is solved and the automation of the measurement of current velocity is realized.  相似文献