秋季连续打捞蓝藻对水-气界面温室气体通量的影响     

荀凡  杜先  陈新芳  刘高飞  齐天赐  冯慕华 《湖泊科学》2020,32(6):1707-1722

在巢湖西北半湖近岸带设置大型围隔研究秋季连续打捞蓝藻对湖泊温室气体通量的影响，应用YL-1000型大型仿生式水面蓝藻清除设备进行原位打捞蓝藻，通过便携式温室气体分析仪-静态箱法对大型围隔内水-气界面CH₄、CO₂通量特征及其影响因素进行观测.结果表明：对比未打捞区，蓝藻连续打捞下打捞区水体中叶绿素a（Chl.a）、悬浮物（SS）浓度不断下降，两者削减率分别为72%、85%，Chl.a、SS浓度分别下降到29.6±2.5 μg/L、12.5±1.2 mg/L，打捞对围隔内颗粒态物质去除效果十分明显；打捞过程中水体溶解性有机物（DOM）中微生物代谢类腐殖质（C1）、类蛋白（C3）显著下降趋势，打捞区C1、C3组分（0.18±0.02、0.06±0.01 RU）强度明显低于未打捞区（0.26±0.05、0.12±0.03 RU），打捞能有效控制藻源性溶解性有机质释放.同时，打捞区水-气界面CH₄通量呈显著下降趋势，未打捞区CH₄通量平均值（17.473±1.514 nmol/（m²·s））为打捞区（7.004±4.163 nmol/（m²·s））近2倍，CH₄通量与Chl.a、C1、C3组分均呈显著正相关，水体中藻源性溶解态有机质对CH₄通量具有促进作用；打捞区CO₂释放通量呈显著上升趋势，打捞区CO₂吸收通量（-0.200±0.069 μmol/（m²·s））明显低于未打捞区（-0.344±0.017 μmol/（m²·s）），CO₂通量与Chl.a、温度均呈显著负相关.秋季打捞对CH₄、CO₂综合日平均通量减排量值为0.275±0.076 mol/（m²·d）（以CO₂当量计）.研究结果揭示了巢湖秋季连续打捞蓝藻过程对水-气界面温室气体具有显著减排作用，且能在一定程度上减缓蓝藻水华与湖泊富营养化、气候变暖之间的恶性循环，为湖泊碳循环和蓝藻水华灾害防控提供科学数据支撑和理论参考.  相似文献   

深时源-汇系统古地理重建方法评述   总被引：1，自引：1，他引：0       下载免费PDF全文

邵龙义  王学天  李雅楠  刘炳强 《古地理学报》2019,21(1):67-81

源-汇系统根据侵蚀、搬运及沉积作用的显著程度可划分为物源区、过渡区和沉积区,根据研究的时间尺度可划分为现代系统、第四纪系统和深时系统。洋陆边缘源-汇系统根据地貌单元的空间配置可划分为“陡—短—深”、“宽—深”及“宽—浅”3种空间分布类型,这3种类型在沉积体积分布及沉积记录保存潜力上存在差异。完整的源-汇系统古地理重建包括沉积区古地理重建和物源区古地理重建。深时尺度下沉积区古地理重建方法随着岩相古地理、构造古地理、生物古地理及层序地层学的发展已趋完善,而物源区古地理重建则更具挑战性,尤其是在物源区遭受侵蚀而不复存在的情况下更具难度。在源-汇分析方法体系中,物源区古流域水系形态、面积范围、地貌地势等古地理要素可通过构造要素分析、碎屑矿物分析、沉积体积回填、地貌学参数比例关系、古水力学参数比例关系和河流沉积通量模型等方法获得。总之,深时源-汇系统古地理重建能够通过盆地沉积记录揭示出物源区古地理演化特征,为沉积盆地充填过程提供沉积供给的信息,对能源矿产勘探和深时古环境研究具有重要意义。  相似文献   

南海盐致环流对台风降水的响应特征分析     

刘娜  王桂华  巩远发  刘磊 《热带海洋学报》2019,38(3):13-21

本文采用多源卫星遥感数据通过统计分析的方法研究了17年间(2000—2016年)南海夏季(6—9月)台风对该海域降水、淡水通量的贡献及其可能导致的环流异常。主要结论如下: 1) 台风是南海中北部降水的重要影响因子, 可导致日平均降水量增加12mm, 约占南海夏季日平均降水(25mm·d ^-1)的一半, 且西北太平洋台风和南海“土台风”产生的降水分布存在显著的区域和强度差异; 2) 夏季, 南海由淡水通量引起的盐致环流表现为以海南岛东南部海域为中心的弱气旋式, 其流量量级约为-0.15Sv, 约占同期风生环流流量(约为-1.5Sv)的10%; 3) 夏季, 台风带来的降水使得南海中北部的气旋式盐致环流增强, 且西北太平洋台风降水导致的淡水通量变化引起的盐致环流强度要强于南海“土台风”。  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   

Subsurface flow measurements using passive flux meters in variably-saturated cold-regions landscapes     

Élise G. Devoie  Ryan F. Connon  James R. Craig  William L. Quinton 《水文研究》2020,34(23):4541-4546

To date, passive flux meters have predominantly been applied in temperate environments for tracking the movement of contaminants in groundwater. This study applies these instruments to reduce uncertainty in (typically instantaneous) flux measurements made in a low-gradient, wetland dominated, discontinuous permafrost environment. This method supports improved estimation of unsaturated and over-winter subsurface flows which are very difficult to quantify using hydraulic gradient-based approaches. Improved subsurface flow estimates can play a key role in understanding the water budget of this landscape.  相似文献   

Ephemeral rollover points and clinothem evolution in the modern Po Delta based on repeated bathymetric surveys     

Fabio Trincardi  Alessandro Amorosi  Alessandro Bosman  Annamaria Correggiari  Fantina Madricardo  Claudio Pellegrini 《Basin Research》2020,32(2):402-418

Reconstructions of ancient delta systems rely typically on a two-dimensional (2D) view of prograding clinothems but may miss their three-dimensional (3D) stratigraphic complexity which can, instead, be best documented on modern delta systems by integrating high-resolution geophysical data, historical cartography, core data and geomorphological reconstructions offshore. We quantitatively compare three precisely positioned, high-resolution multi-beam bathymetry maps in the delta front and pro delta sectors (0.3 to 10 m water depth) of Po di Pila, the most active of the modern Po Delta five branches. By investigating the detailed morphology of the prograding modern Po Delta, we shed new light on the mechanisms that control the topset to foreset transition in clinothems and show the temporal and spatial complexity of a delta and its pro delta slope, under the impact of oceanographic processes. This study documents the ephemeral nature of the rollover point at the transition between sandy topset (fluvial, delta plain to mouth-bar) and muddy seaward-dipping foreset deposits advancing, in this case, in >20 m of water depth. Three multibeam surveys, acquired between 2013 and 2016, document the complexity in space and time of the topset and foreset regions and their related morphology, a diagnostic feature that could not be appreciated using solely 2D, even very high-resolution, seismic profiles. In addition, the comparison of bathymetric surveys gathered with one-year lapses shows the migration of subaqueous sand dunes on the clinothem topset, the formation of ephemeral cut-and-fill features at the rollover point (few m below mean sea level), the presence of collapse depressions derived by sagging of sediments and fluid expulsion (possibly induced by storm waves) on the foreset, and splays of sand likely reflecting gravity flows on the lower foreset. Though the modern Po Delta is anthropogenic in many respects, its subaqueous clinothem can be studied as a scale model for ancient clinothems that are less resolved geometrically and far less constrained chronologically.  相似文献   

A method for evaluating the longitudinal functional connectivity of a river–lake–marsh system and its application in China     

Yeling Liu  Baoshan Cui  Jizeng Du  Qing Wang  Shuling Yu  Wei Yang 《水文研究》2020,34(26):5278-5297

The longitudinal functional connectivity of a river–lake–marsh system (RLMS) refers to the actual water-mediated transport of material from upstream to downstream areas along a spatial gradient and is fundamental to understand hydrological and biogeochemical cycles. However, due to a lack of consensus on appropriate data and methods, the quantification of connectivity is still a challenge, especially at the catchment scale. We developed a new method to evaluate longitudinal functional connectivity based on fluxes of materials (water, sediment, and chemicals) along a RLMS. The calculation of fluxes is based on the longitudinal pattern of terrain gradient, which influences transport efficiency, and on contributions from hillslopes, which set the initial spatial template of material loading to the RLMS. We evaluate the contributions from hillslopes to RLMS based on a new modified version of the index of sediment connectivity (IC) proposed by Borselli et al. (2008) and revised by Chartin et al. (2017).We applied this method to the Baiyangdian Basin covering an area of 3.4 × 10⁴ km² in China and quantified longitudinal functional connectivity during normal, wet, and dry periods(April, July and December) in year 2016. We found that areas with good structural connectivity exhibited poor functional connectivity during the normal and dry periods. Modelling testing with discharge data from hydrological stations and measured chemicals from Baiyangdian Lake was satisfactory in test periods. We conclude that public data and Digital Elevation Model-derived information can be used to reliably map the longitudinal functional connectivity of RLMSs. The proposed method provides a useful tool for monitoring and restoring the longitudinal functional connectivity of RLMSs and our results indicate that efforts aimed at restoring functional connectivity in RLMSs should take into account landscape patterns that can greatly influence fluxes in the watershed.  相似文献   

Clinoform growth and sediment flux into late Cenozoic Qiongdongnan shelf margin,South China Sea     

Si Chen  Ronald Steel  Hua Wang  Rui Zhao  Cornel Olariu 《Basin Research》2020,32(2):302-319

The South China Sea continental margin in the Qiongdongnan Basin (QDNB) area has incrementally prograded since 10.5 Ma generating a margin sediment prism more than 4km-thick and 150–200 km wide above the well-dated T40 stratigraphic surface. Core and well log data, as well as clinoform morphology and growth patterns along 28 2D seismic reflection lines, illustrate the evolving architecture and margin morphology; through five main seismic-stratigraphic surfaces (T40, T30, T27, T20 and T0) frame 15 clinothems in the southwest that reduce over some 200 km to 8 clinoforms in the northeast. The overall margin geometry shows a remarkable change from sigmoidal, strongly progradational and aggradational in the west to weakly progradational in the east. Vertical sediment accumulation rate increased significantly across the entire margin after 2.4 Ma, with a marked increase in mud content in the succession. Furthermore, an estimate of sediment flux across successive clinoforms on each of the three selected seismic cross sections indicate an overall decrease in sediment discharge west to east, away from the Red River depocenter, as well as a decrease in the percentage of total discharge crossing the shelf break in this same direction. The QDNB Late Cenozoic continental margin growth, with its overall increased sediment flux, responded to the climate-induced, gradual cooling and falling global sea level during this icehouse period.  相似文献   

基于经验模态分解和小波分解估算海气通量涡相关计算中的截断时间尺度     

姜浩  赵中阔  樊伟  宋金宝 《海洋与湖沼》2018,49(6):1138-1150

基于时长38天的海表风场实测数据,应用经验模态分解(EmpiricalModeDecomposition,EMD)和小波分解(Wavelet Decomposition, WD)这两种数据处理方法首先对涡相关法中的截断时间尺度(CutoffTimescale,CTS)进行估算,结果显示:基于EMD与WD方法估算出的CTS一般都在40秒左右(EMD的结果略小),远远小于传统涡相关法中CTS的取值(固定为10分钟),且EMD和WD的使用使得每一段数据都能够根据自身的湍流特点而获得合适的CTS; EMD方法和WD方法有效的去除了计算结果中的非湍部分,且对通量传输方向的刻画也更加合理,极大提高了通量的计算精度,所得通量与传统方法计算的通量偏差平均值高达45%;研究还对EMD和WD的优缺点进行了对比分析,结果表明EMD相比于WD有更高的自主性,而WD对信号的分离程度则更高。  相似文献   

A kinematic model of vertical geomagnetic field variation resulting from a steady convective flow     

Alexandra Marsenić 《地球物理与天体物理流体动力学》2014,108(2):191-212

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