How soil texture,channel shape and cross-sectional area affect moisture dynamics and water loss in irrigation channels     

Zhifan Mu  Tianxiao Li  Dong Liu  Qiang Fu  Renjie Hou  Qinglin Li  Yi Ji  Song Cui  Mo Li 《水文研究》2021,35(4):e14155

To enhance the utilization efficiency of farmland irrigation water and reduce the leakage of water conveyance channels, the leakage process of channels was simulated dynamically. The simulated results were compared with data measured in laboratory experiments, and the performance of the model was evaluated. The results indicated that the simulated values of the model were consistent with the observation values, and the R² values varied between 0.91 and 0.99. In addition, based on the laboratory experiments, a water supply system (Mariotte bottles) and soil box were built using plexiglass. Three influencing factors, namely, the channel form, soil texture and channel cross-sectional area, were varied to observe and calculate the resulting cumulative infiltration amount, infiltration rate and wetting front migration distance. HYDRUS-3D software was used to solve the three-dimensional soil water movement equation under different initial conditions. The results demonstrated that the U-shaped channel was more effective than the trapezoidal channel in increasing the utilization efficiency of the water resources. A U-shaped channel with a small channel cross-sectional area should be adopted and the soil particle size should be prioritized in the construction of water conveyance channels for farmlands. The simulation results were in agreement with the observed results, which indicates that HYDRUS-3D is a reliable tool that can accurately simulate the soil moisture movement in water conveyance channels. The research results can provide a reference for the design and operation of farmland irrigation systems.  相似文献   

Impact of the sampling duration on the uncertainty of averaged velocity measurements with acoustic instruments     

Muste Marian  Jongmin Kim  Dongsu Kim 《水文研究》2021,35(4):e14125

Average velocity in streams is a key variable for the analysis and modelling of hydrological and hydraulic processes underpinning water resources science and practice. The present study evaluates the impact of the sampling duration on the quality of average velocity measurements acquired with contemporary instruments such as Acoustic Doppler Velocimeters (ADV) an Acoustic Doppler Current Profilers (ADCP). The evaluation combines considerations on turbulent flows and principles and configurations of acoustic instruments with practical experience in conducting customized analysis for uncertainty analysis purposes. The study sheds new insights on the spatial and temporal variability of the uncertainty in the measurement of average velocities due to variable sampling durations acting in isolation from other sources of uncertainties. Sampling durations of 90 and 150 s are found sufficient for ADV and ADCP, respectively, to obtain reliable average velocities in a flow affected only by natural turbulence and instrument noise. Larger sampling durations are needed for measurements in most of the natural streams exposed to additional sources of data variability.  相似文献   

Concurrent Determination of U‐Pb Age and REE Mass Fractions of Zircon by High Mass Resolution SIMS     

Yu Liu  Qiu‐Li Li  Guo‐Qiang Tang  Xian‐Hua Li 《Geostandards and Geoanalytical Research》2020,44(3):421-437

A combined geochronological and geochemical investigation for the same domain of zircon provides valuable information on timing and genesis, particularly in the case of multi‐growth metamorphic zircon. A high spatial resolution concurrent analytical method for zircon U‐Pb age and rare earth element content was successfully achieved in this study, using a multi‐collector secondary ion mass spectrometer (SIMS) at a ~ 8 μm diameter scale. Special instrument parameters were employed, including a high mass resolution of approximately 15000 applied to replace the previous energy filter method, and a dynamic multi‐collector mode used to reduce the measurement time to 18 min per analysis. Six zircon reference materials yielded precise and accurate ²⁰⁶Pb/²³⁸U ages, which are comparable to those obtained by the ordinary mono‐collector method, but with 2–3 times higher spatial resolution. All zircon grains measured in this study showed enriched heavy‐REE (HREE) contents consistent with previously reported values determined by LA and solution ICP‐MS methods. The light‐REE (LREE) mass fractions measured using both SIMS and LA‐ICP‐MS methods in this study, although with quite different volume, show consistent results within uncertainties.  相似文献   

Variation in the vertical zonality of erodibility and critical shear stress of rill erosion in China's Hengduan Mountains     

Zhengan Su  Donghong Xiong  Jianhui Zhang  Tao Zhou  Hongkun Yang  Yifan Dong  Haidong Fang  Liangtao Shi 《地球表面变化过程与地形》2019,44(1):88-97

Soil erodibility is an essential parameter used in soil erosion prediction. This study selected the Liangshan town watershed to quantify variation in the vertical zonality of rill erodibility (k_r) in China's ecologically fragile Hengduan Mountains. Soil types comprised of yellow–brown (soil A), purple (soil B), and dry-red (soil C) in a descending order of occurrence from the summit to the valley, which roughly corresponds to the vertical climate zone (i.e. cool-high mountain, warm-low mountain, and dry-hot valley sections) of the study area. With elevation, vertical soil zonality varied in both soil organic matter (SOM) content and soil particle-size fractions. A series of rill erosion-based scour experiments were conducted, using water discharge rates of 100, 200, 300, 400, 500, and 600 mL min^-1. Additionally, detachment rates (Dr) were measured under three hydrological conditions (the drainage, saturation, and seepage treatments). Results show that both Dr and flow shear stress (Ʈ) values increased as discharge increased. As elevation increased, the k_r values decreased, while the vertical zonality of critical shear stress (Ʈ_c) values showed no obvious variation. The highest k_r values were observed during the seepage treatment, followed by the saturation treatment then drainage treatment, indicating that variation in vertical hydraulic gradients could significantly alter k_r values. This study also found that land-use types could also alter k_r and Ʈ_c values. Further research, however, is necessary to better quantify the effects of subsurface hydrological conditions and land-use types on k_r under different soil zonalities in China's Hengduan Mountains. © 2018 John Wiley & Sons, Ltd.  相似文献   

Temporal-Spatial Variation of Surface Suspended Matter and Controlling Factors in the Inner Shelf of the East China Sea in Winter     

MIN Jianxiong  LI Guangxue  DING Dong  QIAO Lulu  MA Yanyan  YANG Gang  ZHANG Yaqi  ZHANG Lei  LI Shuhao 《中国海洋大学学报(英文版)》2019,(1)

Based on the observed surface suspended matter in the East China Sea in February 2007 and June 2015, an empirical model was established using L1 b's band 4 data to retrieve surface suspended matter from the Moderate Resolution Imagine Spectroradiometer Terra imagery. The squared correlation coefficient is 0.8358, and the root mean square error is 0.4285 mg L-1. The model reflects the distribution characteristics of surface suspended matter in the inner shelf of the East China Sea. In this paper, the satellite images of the study area were retrieved in January from 2001 to 2015, and the monthly distribution of surface suspended matter were obtained. The inter-annual distribution of the study area is similar, and the concentration of surface suspended matter is higher near the shore than offshore. A large amount of surface suspended matter is transported southeast under the influence of Zhejiang and Fujian coastal current and Taiwan warm current. Only a small amount of surface suspension can reach the Kuroshio area. The surface suspended matter concentration changes obviously near the estuary because of the effect of differences in the flux of the Yangtze River. Meanwhile, winter monsoon, temperature front, El Ni?o events, and other factors affect the distribution of surface suspended matter in 100 m isobath to coastal water but minimally influence the distribution in 100 m isobath to deep sea.  相似文献   

南海边缘海多金属结核与大洋多金属结核对比     

殷征欣  王海峰  韩金生  吕修亚  沈泽中  陈静  贺惠忠  谢安远  关瑶  董超 《吉林大学学报(地球科学版)》2019,49(1):261-277

本文通过系统对比分析前人研究成果，研究了南海边缘海多金属结核的成矿特征，结果表明：南海边缘海结核的矿物组成与大洋结核相似，均主要由锰相矿物和铁相矿物组成，其中锰相矿物主要为水羟锰矿和钡镁锰矿，铁相矿物主要以无定型铁氧化/氢氧化物形式存在，另外南海边缘海结核中含有大量硅酸盐矿物，表明在南海结核成矿过程中受到大量的陆源碎屑矿物混杂；相对于大洋主要经济成矿区的多金属结核，南海边缘海多金属结核中主要的经济元素如Mn、Cu、Co、Ni和Zn质量分数较低，而亲陆源性元素如Fe、Ti、P、Nb、Pb、Rb、Sc、Ta、Sr、Th和REY（REE和Y）等质量分数较高；南海边缘海多金属结核的元素地球化学特征和REE配分模式显示其为水成成因，并呈现更低的Mn/Fe值；同时南海边缘海结核也具有较快的平均生长速率及较高的δCe正异常，表明其生长在更为氧化的海水环境。虽然较快的沉积物沉积速率和动荡的海水环境影响了南海边缘海结核的成矿，但大量陆源物质进入海洋也为南海边缘海结核提供了丰富的成矿物质来源，便于南海边缘海结核的快速生长成矿。南海边缘海结核富集有Fe、Ti、Pb、Rb、Th和REY等金属元素，同样可以作为极具潜力的海洋矿产资源。南海边缘海多金属结核具有其独特的地球化学特征，与大洋多金属结核存在着明显差异。  相似文献   

套管锻铣开窗技术在土耳其贝帕扎里碱矿中的应用          下载免费PDF全文

林修阔  刘汪威  陈晓林  刘志强  隆东 《探矿工程》2020,47(8):50-56

土耳其贝帕扎里碱矿在矿区边缘的碱层出现埋深起伏大、厚度变化大、易尖灭、易涌水等情况，这些特殊的地质情况导致水溶开采钻井过程中同一组井的套管最终下入到了不同的层位，或是原先下入的矿层不稳定，易坍塌。为了解决以上问题而引入了套管锻铣开窗技术。该技术可以将老井眼中已被套管封闭的上部碱层暴露出来形成新的采矿通道，从而提高矿区采收率。先后在14口老井眼中完成了套管锻铣作业，均达到了预期效果。本文介绍了套管锻铣器的工作原理，并以H066井组为例，详细阐述了套管锻铣开窗工艺技术。工程实践表明，套管锻铣开窗技术对于换层开采、钻井处理事故、事故井恢复性生产等方面具有一定的效果，具有减少钻井工期、降低施工成本、延长老井使用寿命、提高矿藏产量等优点，有广阔的应用前景。  相似文献   

Application of Avaatech X-ray fluorescence core-scanning in Sr/Ca analysis of speleothems     

Dong LI  Liangcheng TAN  Fei GUO  Yanjun CAI  Youbin SUN  Gang XUE  Xing CHENG  Hong YAN  Hai CHENG  R.Lawrence EDWARDS  Yongli GAO  Jessica KELLEY 《中国科学:地球科学(英文版)》2019,(6)

Application of X-ray fluorescence core-scanning(XRF-CS) on both marine and lake sediments has achieved remarkable results. However, its application has not been widely extended to the research on speleothems. In this study, we measure the Sr abundance and the Sr/Ca ratios of three stalagmites(two aragonite stalagmites, one calcite stalagmite) using the state-of-the-art fourth-generation Avaatech high-resolution XRF core scanner. Through comparisons among different scan paths and among different scan resolutions, as well as comparisons with inductively coupled plasma optical emission spectrometer(ICP-OES), Itrax XRF, and Artax XRF results, we confirm that the Avaatech XRF core scanner could precisely, quickly, and nondestructively analyze the high-resolution Sr abundance of speleothems. Furthermore, we combine the stalagmite δ~(18)O records to explore the paleoclimatic significance of the measured stalagmite Sr/Ca.  相似文献   

地表暖化影响下温度示踪地下水流速方法     

董林垚  任洪玉  雷俊山  刘纪根 《吉林大学学报(地球科学版)》2019,49(3):773-783

为构建温度示踪方法测算地下水流速技术体系，并应用于区域地下水资源评价，基于最小二乘法和垂向一维非稳定流水-热运移方程数值解法，提出地表暖化情形下地下水流速计算方法，并对雷州半岛东北部地下水流速进行测算。结果表明：研究区域地下水补给速度为0.796 m/a，入渗以西北部降水和运河渗漏为主；地下水排泄速度为0.269 m/a，排泄入海主要发生在东海岛、南三岛和硵州岛附近。温度示踪解析区域地下水流动情况与地下水位分布情况基本一致，观测和计算地温数据具有较强相关性（R²>0.50）和较低均方根误差（均值0.748），表明提出方法率定得到的地下水流速具有较强的可靠性。参数敏感性分析结果表明，地质体热扩散率和地表温度均对地温计算结果产生较明显的影响，参数的准确率定对利用地温计算地下水流速十分重要。  相似文献   

Long‐term temporal and spatial patterns in bioeroding sponge distribution at the Abrolhos Bank,Brazil, Southwestern Atlantic     

Fernando Coreixas de Moraes  Fernanda Cervi  Cludia S. Karez  Leonardo T. Salgado  Rodrigo L. Moura  Gabriella A. Leal  Alex C. Bastos  Gilberto M. Amado‐Filho 《Marine Ecology》2019,40(3)

Bioeroding sponges belong to the most dominant bioeroders, significantly contributing to the erosion of coral reefs. Some species are tolerant or even benefit from environmental conditions such as ocean warming, acidification, and eutrophication. In consequence, increases in sponge bioerosion have been observed on some coral reefs over the last decades. The Abrolhos Bank is the largest coral reef system in the South Atlantic. It has been affected by sedimentation, eutrophication, overfishing, and climate change, mainly affecting coastal reefs, and at lesser intensity outer ones as well. This study aimed to describe spatial and temporal patterns in bioeroding sponge distribution in carbonate substrates in the Abrolhos Bank. Photo‐quadrats were used to compare bioeroding sponge abundance between two shallow reefs: a coastal, Pedra de Leste (PL), and an outer reef, Parcel dos Abrolhos (PAB). Each individual was delimitated over the substrate by determining the sponge surface through a line connecting the outermost papillae. The study was conducted over 6 years in 2008–2009 and 2013–2016. Four species of bioeroding sponges were identified: Cliona carteri Ridley, 1881, C. delitrix Pang, 1973, C. cf. schmidtii Ridley, 1881, and Siphonodictyon coralliphagum Rützler, 1971. The distribution and abundance of species varied between the inner and outer reefs and across the years, and displayed certain selectivity for the calcareous substrates recorded. Crustose coralline algae (CCA) were the main substrate excavated by the most abundant bioeroding species, C. carteri, and represented 70% of the substrate types occupied by this sponge (CCA, coral overgrown by CCA and plain coral). The highest abundance of bioeroding sponges observed in photo‐quadrats was 21.3 individuals/m² at the outer reefs (PAB) in 2014. The abundances or areal extents of bioeroding sponges were up to 10 times greater on the outer reefs than on the coastal ones, where sedimentation is higher and more strongly influenced by siliciclastic material. Moreover, a higher herbivorous fish biomass has been reported on outer reefs which could also influence the higher abundance of bioeroding sponges in outer reefs. During the study period of 6 years, an increase in bioeroding sponge abundance was observed at the outer reefs (PAB), with the sea surface temperature increase. As CCA have an important role in reefal cementation and carbonate production in the Abrolhos reefs, a bioerosion impact might be expected, in particular, on the outer reefs.  相似文献