珠江口黄茅海底质沉积中介形类的生态类型及其分布特征          下载免费PDF全文

黄毅  吴洁  殷征欣  关瑶  倪锦锋 《海洋开发与管理》2020,37(6):89-94

文章通过对黄茅海底质沉积样品中的介形类生态类型进行研究，探讨其空间分布特征。研究结果显示：研究区内出现的介形类可划分为4种生态类型，总体表现为以近岸广盐型分子占主导地位，优势度极高；浅海多盐 真盐型分子次之；而广海真盐型和淡水 微盐型分子丰度很低。根据黄茅海河口湾的水体条件，可大致将研究区划分为5种亚环境区，各区内的介形类生态类型组成也存在较大差别，表现出不同的空间分布特征。介形类分布受海水盐度控制最大，其次为水动力条件。在水体盐度小、水动力条件强的河流入海口及其影响区域，介形类丰度小，且生态类型单一；而在黄茅海河口湾南部海域，由于海水底层盐度全年在15‰以上，水动力条件适宜，介形类丰度总体较高，生态类型增多。  相似文献   

珠江口典型海岛周边水域浮游植物分布特征及其影响因素*     

苏芯莹  钟瑜  李尧  谭美婷  黄亚东  刘珊  徐向荣  宋星宇 《热带海洋学报》2020,39(5):30-42

旅游业为海岛带来可观经济效益的同时, 人类活动也导致水体生态环境恶化, 如水体富营养化加剧、赤潮频发等。文章通过对珠江口东南部典型海岛——庙湾岛和外伶仃岛周边水域丰水期和枯水期现场环境数据与浮游植物分布特征的对比研究, 分析珠江径流等自然因素以及人类活动对河口天然海岛周边水体生态的潜在影响。枯水期外伶仃岛和庙湾岛周边水域海水分别镜检鉴定出76种和74种浮游植物, 两个海岛浮游植物平均细胞密度分别为2.62×10⁴个·L^-1和2.08×10⁴个·L^-1; 丰水期则分别鉴定出38种和47种浮游植物, 平均细胞密度分别为52.91×10⁴个·L^-1和170.57× 10⁴个·L^-1。在外伶仃岛和庙湾岛, 丰水期中肋骨条藻(Skeletonema coatatum)均为绝对优势种, 而枯水期两个岛的最主要优势种分别为窄隙角毛藻(Chaetoceros affinis)和新月筒柱藻(Cylindrotheca closterium), 物种多样性指数均明显高于丰水期。两个海岛微型浮游植物相对于其他两个粒级常占据优势地位, 但在丰水期, 小型浮游植物贡献明显上升, 其中外伶仃岛相对于枯水期由16.32%升至26.75%, 庙湾岛则由12.12%升高至24.78%。两个海岛在丰水期和枯水期均仅检出聚球藻(Synechococcus, Syn)和真核微微型藻类(eukaryotic, Euk)两大微微型浮游植物类群, 两者细胞密度分别为~10⁷个·L^-1及~10⁸个·L^-1量级。与环境因子的对比分析表明, 两个海岛浮游植物的区域分布与季节变化受多种因素影响, 其季节性差异主要受径流影响强度、影响范围以及相应的盐度、营养盐等环境因素的季节变化所调控。丰水期岛屿屏蔽效应对浮游植物丰度的区域分布特征有显著影响, 无论小型浮游植物还是微微型浮游植物均发现存在迎流面出现丰度高值分布的现象, 但对群落结构的分布影响不明显; 在枯水期, 水体环境很可能主要受人类活动与水体垂直混合扰动的综合影响, 总体上浮游植物分布的区域差异较小。  相似文献   

珠江三角洲地区活动断裂探查方法浅析          下载免费PDF全文

黄孝波  孙社良  屈尚侠 《山东国土资源》2019,35(9)

活动断裂是指晚第四纪以来活动过的断裂,它威胁到人类生命财产安全。该文通过文献调研,结合珠江三角洲基底断裂探查研究项目的实际工作,介绍了地面地质调查、浅层地震、断层气测量、钻探及连孔剖面、断裂物质测年、历史地震分析等活动断裂探查方法,以及这些方法的优缺点,并指出了目前活动断裂探查存在的一些问题,提出了建议。  相似文献   

Changes in run‐off and sediment load in the three parts of the Yellow River basin,in response to climate change and human activities     

Chaojun Gu  Xingmin Mu  Peng Gao  Guangju Zhao  Wenyi Sun 《水文研究》2019,33(4):585-601

Hydrological regimes in the Yellow River have changed significantly because of climate change and intensive human interventions. These changes present severe challenges to water resource utilization and ecological development. Variation of run‐off, suspended sediment load (SSL), and eight precipitation indices (P1: 0–12 mm·day^?1, P12: 12–25 mm·day^?1, P25: 25–50 mm·day^?1, P50: P ≥ 50 mm·day^?1 and corresponding rainfall day: Pd1, Pd12, Pd25, Pd50 day year^?1) in three critical parts of the Yellow River basin (source region: SRYRB, upper reaches: URYRB, middle reaches: MRYRB) were investigated for the period from 1960 to 2015. The results show that run‐off and SSL significantly decreased (P < 0.01) in the URYRB and the MRYRB, whereas their decline in the SRYRB was insignificant (P > 0.05). Moreover, run‐off in the URYRB had one change point in 1987, and SSL in the URYRB as well as run‐off and SSL in the MRYRB had two change points (in the 1970s and the 1990s). Over the same period, only Pd1 and Pd12 in the SRYRB showed significant increasing trends, and an abrupt change appeared in 1981. The optimal precipitation indices for assessing the effects of precipitation on run‐off and SSL in the URYRB and MRYRB were Pd50 and P12, respectively. A double‐mass curve analysis showed that precipitation and human activities contributed to approximately 20% and 80% of the reduction in run‐off, respectively, for both the SRYRB and the MRYRB. However, the contribution rate of precipitation and human activities on SSL reduction was approximately 40% and 60% in the URYRB and 5% and 95% in the MRYRB, respectively. Human activities, primarily soil and water conservation measures and water extraction (diversion), were the main factors (>50%) that reduced the run‐off. However, the dominant driving factors for SSL reduction were soil and water conservation measures and reservoir interception, for which the contribution rate was higher than 70% in the MRYRB. This work strengthens the understanding of hydrological responses to precipitation change and provides a useful reference for regional water resource utilization.  相似文献   

Identification of groundwater mean transit times of precipitation and riverbank infiltration by two‐component lumped parameter models     

Nguyen Le Duy  Nguyen Viet Dung  Ingo Heidbüchel  Hanno Meyer  Markus Weiler  Bruno Merz  Heiko Apel 《水文研究》2019,33(24):3098-3118

Groundwater transit time is an essential hydrologic metric for groundwater resources management. However, especially in tropical environments, studies on the transit time distribution (TTD) of groundwater infiltration and its corresponding mean transit time (mTT) have been extremely limited due to data sparsity. In this study, we primarily use stable isotopes to examine the TTDs and their mTTs of both vertical and horizontal infiltration at a riverbank infiltration area in the Vietnamese Mekong Delta (VMD), representative of the tropical climate in Asian monsoon regions. Precipitation, river water, groundwater, and local ponding surface water were sampled for 3 to 9 years and analysed for stable isotopes (δ¹⁸O and δ²H), providing a unique data set of stable isotope records for a tropical region. We quantified the contribution that the two sources contributed to the local shallow groundwater by a novel concept of two‐component lumped parameter models (LPMs) that are solved using δ¹⁸O records. The study illustrates that two‐component LPMs, in conjunction with hydrological and isotopic measurements, are able to identify subsurface flow conditions and water mixing at riverbank infiltration systems. However, the predictive skill and the reliability of the models decrease for locations farther from the river, where recharge by precipitation dominates, and a low‐permeable aquitard layer above the highly permeable aquifer is present. This specific setting impairs the identifiability of model parameters. For river infiltration, short mTTs (<40 weeks) were determined for sites closer to the river (<200 m), whereas for the precipitation infiltration, the mTTs were longer (>80 weeks) and independent of the distance to the river. The results not only enhance the understanding of the groundwater recharge dynamics in the VMD but also suggest that the highly complex mechanisms of surface–groundwater interaction can be conceptualized by exploiting two‐component LPMs in general. The model concept could thus be a powerful tool for better understanding both the hydrological functioning of mixing processes and the movement of different water components in riverbank infiltration systems.  相似文献   

Artificial neural network simulation for prediction of suspended sediment concentration in the River Ramganga,Ganges Basin,India     

Mohd Yawar Ali Khan  Fuqiang Tian  Faisal Hasan  Govind Joseph Chakrapani 《国际泥沙研究》2019,34(2):95-107

The relation between the water discharge (Q) and suspended sediment concentration (SSC) of the River Ramganga at Bareilly, Uttar Pradesh, in the Himalayas, has been modeled using Artificial Neural Networks (ANNs). The current study validates the practical capability and usefulness of this tool for simulating complex nonlinear, real world, river system processes in the Himalayan scenario. The modeling approach is based on the time series data collected from January to December (2008–2010) for Q and SSC. Three ANNs (T1-T3) with different network configurations have been developed and trained using the Levenberg Marquardt Back Propagation Algorithm in the Matlab routines. Networks were optimized using the enumeration technique, and, finally, the best network is used to predict the SSC values for the year 2011. The values thus obtained through the ANN model are compared with the observed values of SSC. The coefficient of determination (R²), for the optimal network was found to be 0.99. The study not only provides insight into ANN modeling in the Himalayan river scenario, but it also focuses on the importance of understanding a river basin and the factors that affect the SSC, before attempting to model it. Despite the temporal variations in the study area, it is possible to model and successfully predict the SSC values with very simplistic ANN models.  相似文献   

Satellite-based monitoring of contrasting characteristics of suspended sediment discharged from the Red and the Ma river systems along the northern coast of Vietnam     

Yoshimitsu Tajima  Kavinda Gunasekara  Hung Thanh Nguyen 《国际泥沙研究》2019,34(3):191-204

The northern coast of Vietnam has accumulated a significant amount of sediment discharged from the multiple distributaries of rivers such as the Red River and Ma River. While recent decreases of the sediment supply appears to have a significant impact on coastal erosion, the complex network of these distributaries makes it difficult to determine the overall spatiotemporal characteristics of sediment discharges and related topographic changes. The goal of the current study is to develop a satellite-based monitoring system for observation of turbidity discharged from the multiple rivers and to investigate the applicability of the developed monitoring system through a case study on the northern coast of Vietnam. Based on the in-situ observed data, a formula was determined for estimation of the surface water turbidity as a function of the red band reflectance of Moderate Resolution Imaging Spectro-radiometer (MODIS) images. The formula was then combined with a newly determined threshold for cloud-masking to obtain maps of the nearshore turbidity patterns. These maps capture the spatiotemporal water surface turbidity along the entire coast of the Red River Delta and the coast around the Ma River mouth over the past sixteen years with frequency of twice a day. Finally, long-term trends of the turbidity patterns from multiple rivers were compared with the in-situ observation data and it was found that the Red River and the Ma River showed clearly contrasting characteristics, which reasonably explain the recent coastal shoreline changes and characteristics of sediment sampled along the coast.  相似文献   

云南小江流域典型泥石流沟中底栖动物群落特征及其对河流地貌的响应   总被引：2，自引：2，他引：0  

朱朋辉  潘保柱  李志威  蒋小明  赵娜  赵耿楠  何浩然 《湖泊科学》2019,31(3):869-880

云南小江流域为典型干热河谷区，该区域干热少雨，流域内泥石流沟众多，生态环境十分脆弱.2017年4月和9月对小江流域的吊嘎河、蒋家沟、蓝泥坪沟、清水沟、陶家小河5条泥石流沟及小江干流开展了系统调查，旨在摸清5条泥石流沟及小江干流河流地貌、水环境及底栖动物群落现状，分析不同河床结构发育程度的泥石流沟间的底栖动物群落差异，揭示底栖动物对反映河床结构发育程度的河流地貌特征参数凹凸度的响应关系.调查期间于5条泥石流沟及小江干流中共采集到底栖动物70种，隶属于4门6纲38科69属，其中环节动物6种，软体动物2种，节肢动物61种，扁形动物1种.从种类类群来看，5条泥石流沟及小江干流的底栖动物物种数、密度、生物量上均以节肢动物占绝对优势，分别占总量的78.0%~92.5%、98.7%~100%、65.0%~100%.从功能摄食类群上来看，5条泥石流沟及小江干流底栖动物密度上均以直接收集者为主，占总量的74.3%~96.3%.回归分析表明，5条泥石流沟中底栖动物物种数、密度及生物量均与河流地貌特征参数凹凸度呈正相关关系，由此可见，发育良好的河床结构在维持河流地貌稳定和改善河流生态方面起着举足轻重的作用.本研究结果可为小江流域山区河流泥石流沟河床结构重建及生态修复提供科学依据.  相似文献   

帕隆藏布流域冰湖变化及危险性评估     

刘娟  姚晓军  高永鹏  祁苗苗  段红玉  张大弘 《湖泊科学》2019,31(4):1132-1143

冰湖作为区域气候变化的灵敏指示器和主要冰川灾害的启动器，认识其空间分布及变化特征对探讨冰湖对气候变化的响应规律及冰湖溃决危险性评估具有重要意义.基于1968-1980年地形图数据和1994-2016年Landsat TM/OLI遥感影像资料，综合利用RS、GIS技术和数理统计方法分析帕隆藏布流域面积≥ 0.01 km²冰湖时空分布及其动态变化，并对潜在危险性冰湖进行判别和评估.结果表明：2016年帕隆藏布流域共有冰湖351个，面积50.48 km²，且面积和数量分别以面积>1 km²和面积<0.1 km²的冰湖为主，这些冰湖主要分布于海拔2800~5400 m之间.近50年来帕隆藏布流域冰湖总体呈数量增多、面积增加态势；海拔<3000 m的冰湖相对稳定，而海拔>4500 m的冰湖数量和面积增加则相对迅速.近50年间帕隆藏布流域冰川面积减少591.34 km²，气候变暖导致的冰川末端退缩和冰川融水增加为冰湖形成和扩张提供了发育空间和物质来源.切毛措、光谢错等9个冰湖为潜在危险性冰湖，预计未来一段时间内帕隆藏布流域冰湖溃决可能处于活跃阶段，其形成和暴发也将更加频繁.  相似文献   

筑坝拦截对黑河河道沉积物粒度空间分布的影响   总被引：2，自引：1，他引：1  

王昱  连运涛  冯起  王之君  赵维俊  刘娟娟  卢世国  张昕雨 《湖泊科学》2019,31(5):1459-1467

河流沉积物对流域环境变化具有敏感响应，其粒度参数能反映沉积环境中物质来源和水动力环境.本文以黑河流域上中游为研究区域，探究河流沉积物粒度对流域环境变化的响应.从黑河上中游干流22个主要控制断面采集河床沉积物样品，采用筛分法和吸管法对沉积物样品粒度参数进行测定，并分析其空间分布规律对筑坝拦截为主的环境改变响应.研究结果表明：受梯级水库建设影响，黑河上中游泥沙粒径大小差异显著.干流库区泥沙粒径较自然河段明显减小，分选很好，呈正偏或极正偏尖锐分布，而且在库区不同沉积高度上表现出分层沉积特征；坝下游河段因遭受强烈冲刷，较自然河段泥沙粒径粗化显著，分选变差，偏态趋向极正偏，峰态尖锐化；水库回水区受水库壅水及下泄清水的双重制约，泥沙粒度参数介于自然河段和坝下游河段之间，整体分选中等，呈极正偏尖锐分布；沉积环境分析表明，上游支流河段沉积物粒度特征受泥沙供给和物源特征的影响较水动力条件显著，干流河段沉积物粒度特征主要受水动力条件控制.研究结果既符合河流上中游沉积物粒度分布规律，也反映了河流环境变化对沉积物粒度组成的影响.  相似文献