从正交曲线坐标推求悬移质运动扩散方程

从正交曲线坐标推求悬移质运动扩散方程熊治平（武汉水利电力大学）一、引言河流泥沙工程学中￣［１］，扩散理论是用来研究悬移质运动的基本理论之一。建立在扩散理论基础之上的悬移质运动扩散方程即悬移质含沙量随时空变化的微分方程，目前一般只应用于直角坐标系中。而...     

长江口泥沙运动形式分类及对深水航道淤积影响

潮汐河口泥沙运动复杂多变,科学划分泥沙运动形式并评估其对航道淤积的影响,是厘清航道淤积泥沙来源、制定有效减淤措施的关键。基于长江口深水航道所处南港—北槽河段2015年和2018年洪季、枯季表层沉积物和近底悬沙的现场采样数据,分析提出潮汐条件下推移质、悬移质和时推时悬泥沙3类泥沙运动形式的粒径划分方法,量化3类泥沙对深水航道淤积的贡献比例。结果表明：近底悬沙级配曲线上拐点粒径对泥沙由推移质向悬移质转化具有较好的指示意义;长江口南港—北槽悬沙、底沙交换显著,深水航道淤积物中除仅做推移质或悬移质运动的泥沙外,还包括大量的时推时悬泥沙,其在航道淤积泥沙中的占比最高,约达50%～60%;南港段航道洪季、枯季推移质淤积占比分别为36%和26%,高于悬移质的6%和13%;北槽段航道悬移质落淤泥沙占比为44%～48%,明显较推移质3%～6%的占比高。3类泥沙运动形式粒径划分方法为深化潮汐河口泥沙运动规律认识、判别航道淤积泥沙来源提供了新途径。     

具有合理性检验功能的悬移质级配曲线图形处理软件的设计

具有合理性检验功能的悬移质级配曲线图形处理软件的设计吴金塔，潘秀丽（福建省水文总站）１问题的提出在悬移质泥沙颗粒分析（以下简称颗分）中，需要计算泥沙的平均粒径和中数粒径。而在泥沙颗分实验中，一般需测定大于某些粒径级的密度，因此只能靠绘制颗粒密度Ｐ同粒...     

床面附近泥沙交换率在悬移质输沙计算中的应用

总结并分析了关于悬移质运动方程的源/汇项或底部边界条件的已有的处理方法.认为在悬移质输沙计算中,这些方法因引入了平衡输沙概念、忽略了推移质颗粒对悬移质运动的影响或因缺乏床面附近泥沙质量交换率的理论表达式,均存在着某些不足.运用床面附近泥沙质量交换率理沦,对一般的悬移质输沙方程的底部边界条件进行了新的探讨,并提供了关于一维和垂向二维悬移质输沙的计算实例.     

漏斗式全沙排沙技术及其应用

主要介绍了一种新型泥沙处理技术,即“漏斗式全沙排沙术”.该项技术既可以排除粗颗粒的推移质泥沙,也可以排除细颗粒的悬移质泥沙.对0.5mm以上的粗颗粒泥沙的截沙率为100%,对0.5mm以下细颗粒泥沙的截沙率为90%,排沙耗水量仅占渠道引水量的2%～5%.     

黄河下游河道悬移质泥沙与床沙交换计算研究

在前人研究成果的基础上,根据挟沙水流任一粒径组泥沙在输移过程中质量守恒原理,建立了一维非恒定挟沙水流悬移质泥沙和床沙交换基本方程;通过引入平衡冲淤物粒径的概念,建立了河床处于淤积与冲刷时冲淤物粒径的计算公式,并提出了一套完整的一维非恒定挟沙水流悬移质泥沙和床沙交换计算方法。将该成果引入黄河下游一维扩展泥沙数学模型中,采用黄河下游1977年高含沙洪水与1999年汛后至2002年汛前冲刷系列进行了验证。结果表明,该方法能较好地模拟悬沙与床沙的交换过程,克服分组挟沙力方法的缺陷,使得非均匀沙计算理论上更加完善,应用上更加方便。     

鲁北平原区河道悬移质泥沙规律浅析

分析了鲁北平原主要排洪河道悬移质泥沙的来源、组成、年内、年际变化及沿程变化规律，水沙关系，输沙量与年径流量、年降水量之间的关系。指出鲁北平原河道泥沙主要有两大来源：一是流域产沙；二是引黄客沙，其中引黄客沙是鲁北平原河道泥沙的主要来源，引黄客沙的大量进入，不但改变了河流泥沙形势，而且加剧了河道淤积，使各河行洪能力较70年代降低了40％～70％。鲁北平原区河流泥沙的输沙量年际变化较大，与年径流量的丰枯变化有较明显的相应性；输沙量年内分配极不均匀，主要集中在汛期（6～9月）。     

河流泥沙输移过程中矿物风化的碳汇效应初探——以长江干流为例

本文首先提出了河流泥沙输移过程中泥沙中的钙镁矿物溶蚀消耗水体中的CO2并具有碳汇功能的观点。基于前人长江干流从源头到入海口和支流2003~2007年期间4次河流悬移质泥沙的化学元素组成和矿物组成资料,分析悬移质中CaO、MgO含量和方解石、白云石含量变化特征,定量计算了这些取样点悬移质泥沙的CO2总碳汇能力和非永久性、永久性碳汇能力,分析了不同碳汇能力沿程变化规律及其原因。碳汇计算结果表明：寸滩—大通河段1956~2000年期间泥沙输移过程中钙镁矿物溶蚀产生的总碳汇量、非永久性和永久性碳汇量分别为2572万t/a、1700万t/a和872万t/a。由于输沙量减少,寸滩站—大通站河段的总碳汇量、非永久性和永久性碳汇量2006~2019年期间较1956~2000年期间相应分别减少了1852万t、1224万t和872万t。三峡水库年均淤积量1. 145亿t,损失总碳汇量675. 6万t,相当于三峡电站减排二氧化碳8580万t的7. 9%。全球河流入海年输沙量126. 1亿t,以寸滩- 吴淞口河段碳汇功能0. 060 t/t计,总碳汇量7. 57亿t相当于全球岩石风化碳汇总量10. 56亿t CO2的71. 6%。河流泥沙输移过程中钙镁矿物溶蚀的碳汇量具有重要的作用,其溶蚀速率大于原地风化。     

河流泥沙测验仪器的研究

为了解决河流的泥沙测验问题，人们试图用各种物理原理和方法来研制测沙仪，但是，均未达到满意的结果。分析了几种测沙仪的原理及其存在多参数的不足，介绍了振动式悬移质测沙仪的工作原理、主要技术指标、比测实验及试用情况。     

1956—2008年鄱阳湖流域水沙输移趋势及成因分析

利用鄱阳湖流域代表性水文站1956—2008年实测年径流量及年输沙量资料序列,采用Mann-Kendall秩相关检验法,研究鄱阳湖流域水沙量年际变化趋势和可能发生突变的时间,并从流域降雨、用水、水库拦沙、水土流失及其治理等方面分析了鄱阳湖流域水沙变化的主要影响因素。研究结果表明:鄱阳湖地区来水量和出湖水量有小幅增大趋势;鄱阳湖流域来沙量呈异常显著减小趋势,发生突变的年份为1998—1999年;实测出湖沙量从2002年开始呈明显的减少趋势。通过对有关影响因素的研究,发现鄱阳湖流域气候变化降雨量减少对近10年鄱阳湖出入湖径流量的减少影响显著;水库滞沙是鄱阳湖入湖沙量减少的主要原因;出湖沙量变化主要受上游水库群的影响,还有近年湖区采砂的影响。     

Images of concentrations of dissolved sulphide in the sediment of a lake and implications for internal sulphur cycling

The high-resolution mapping of dissolved sulphide in modern sediment of a permanently stratified (meromictic) lake is possible using a novel sulphide imaging technique (called a 'sulphur print'). The technique is simple, easy to use and can map a relatively large area (up to several dm²). In situ sulphur prints from anoxic fine-grained sediments are able to reveal internal structures in apparently homogeneous materials. Sulphur prints have been used to examine the formation and distribution of dissolved sulphide in the sediment and water column of the meromictic Lake Cadagno (southern Switzerland). The prints show clearly that a previously unknown laminar convective flow of sulphide-free porewater occurs across the sediment–water interface. Such convective flow out of the sediment must be accompanied by convective flow of sulphide- and sulphate-rich lake water into the sediment, and may be an important mechanism for the accumulation of sulphur in the sediment.     

Sediment waves in a modern high-energy glacilacustrine environment

A 4·7 km² field of sediment waves occurs in front of the Slims River delta in Kluane Lake, the largest lake in the Yukon Territory. Slims River heads in the Kaskawulsh Glacier, part of the St Elias Ice Field and discharges up to 400 m³ s^?1 of water with suspended sediment concentrations of up to 7 g l^?1. The 19 km long sandur of Slims River was created in the past 400 years since Kaskawulsh Glacier advanced and dammed the lake and the sandur has advanced into Kluane Lake at an average rate of 48 m a^?1. However, this rate is decreasing as flow is diverted from Slims River because of the retreat of the Kaskawulsh Glacier. The sandur and a road constructed on the delta remove coarse‐grained sediment, so the river delivers dominantly mud to the lake. Inflow during summer generates quasi‐continuous turbidity currents with velocities up to 0·6 m s^?1. The front of the delta consists of a plane surface sloping lakeward at 0·0188 (1·08°). A field of sediment waves averaging 130 m in length and 2·3 m in amplitude has developed on this surface. Slopes on the waves vary from ?0·067 (?3·83°, i.e. sloping in the opposite direction to the regional slope) to 0·135 (7·69°). The internal structure of the sediment waves, as documented by seismic profiling, shows that sedimentation on the stoss portion of the wave averages 2·7 times that on the lee portion. Rates of sediment accumulation in the wave field are about 0·3 m a^?1, so these lacustrine waves have formed in a much shorter period of time (less than 200 years) and are advancing upslope towards the delta much more quickly (1 to 2 m a^?1) than typical marine sediment waves. These waves formed on the flat surface of the lake floor, apparently in the absence of pre‐existing forms, and they are altered and destroyed as the wave field advances and the characteristics of the turbidity currents change.     

武汉东湖现代沉积物磁组构特征及意义

采自武汉东湖现代沉积物的0．86m长的样品被用于研究湖泊现代沉积物的磁性各向异性，研究发现，东湖的现代沉积可划分为3个阶段，不同阶段的沉积特征与磁学性质反映了不同的沉积环境物源差异，通过分析样品沉积特征，磁化率K值特征并结合磁性矿物在各层面间的差别，从而分析得出磁化率K值可作为地层划分的有效辅助手段，磁铁矿广泛存在于所有砂质及泥质沉积物中，是引起东湖现代沉积物磁化率变化的主导性物质。     

石臼湖近代环境演化历史

以2007年在石臼湖采集的浅岩芯钻孔(SJH07-C1)研究近代石臼湖湖泊环境演化历史以及人类活动的影响。运用核素²¹⁰Pb和 ¹³⁷Cs进行定年,²¹⁰Pb 的CRS模式定年结果与¹³⁷Cs方法获得的年代具有较好的可比性。同时分析了岩芯沉积物的理化指标,包括烧失量、总磷、金属元素和磁化率。分析表明：  1955年以前地球化学指标表明石臼湖湖泊沉积物中人类活动信息较弱,但总磷和有机质（烧失量）开始出现增加,湖泊营养水平开始升高。1955～1969年,湖泊沉积物磁化率较高,重金属（包括铜、铅、锌和汞）含量快速增加,可能与该期开始大量使用化肥、农药有关,导致入湖污染物增加。1969～1997年期间,1969～1979年时段湖泊沉积物磁化率最高,重金属含量比较稳定,在石臼湖进行了大规模的围垦;   1979～1997年,湖泊沉积物磁化率较高但呈减少趋势,重金属含量再次快速增加,总磷增加较快,说明该阶段入湖污染物增加,湖泊营养水平也在增加。1997～2007年,磁化率较低,重金属含量保持在高水平,总磷快速增加,显示该阶段湖泊营养水平较高,但入湖物质通量在减少。     

新疆柴窝堡湖沉积物中环境敏感粒度组分揭示的环境信息

通过对柴窝堡湖沉积物剖面和流域表层沉积物进行粒度分析,结合沉积剖面年代序列,研究了柴窝堡地区的环境演变与沙尘暴事件。首先通过主成分因子分析,对柴窝堡湖沉积物剖面粒度不同粒级组分含量进行了研究,探讨了湖泊沉积物的物质来源,获得了两个主控因子F1和F2,它们控制了湖泊沉积物近97.7%的粒度变化特征。研究表明,F2代表了以57 μm为众数粒径的次总体,主要来源于地表风沙侵蚀;而F1为以7 μm为众数粒径的次总体,主要受流水作用控制。进而通过粒径-标准偏差法,提取了湖泊沉积物中环境敏感粒度组分,风成组分C2（20~209 μm）反映了区域风沙活动的历史,并揭示了1910-1930年和1980-2000年为百年来的两个沙尘暴相对活动强烈的时期。沉积物中记录的1980年和2000年左右的沙尘事件与器测记录及历史文献记载具有很好的一致性。最后利用均值突变诊断分析,发现柴窝堡湖地区1910年前后存在近百年来最强的沙尘事件,揭示了近百年来该地区一次最强的环境突变事件。      

Multi‐basin depositional framework for moisture‐balance reconstruction during the last 1300 years at Lake Bogoria,central Kenya Rift Valley

Multi‐proxy analysis of sediment cores from five key locations in hypersaline, alkaline Lake Bogoria (central Kenya Rift Valley) has allowed reconstruction of its history of depositional and hydrological change during the past 1300 years. Analyses including organic matter and carbonate content, granulometry, mineralogical composition, charcoal counting and high‐resolution scanning of magnetic susceptibility and elemental geochemistry resulted in a detailed sedimentological and compositional characterization of lacustrine deposits in the three lake basins and on the two sills separating them. These palaeolimnological data were supplemented with information on present‐day sedimentation conditions based on seasonal sampling of settling particles and on measurement of physicochemical profiles through the water column. A new age model based on ²¹⁰Pb, ¹³⁷Cs and ¹⁴C dating captures the sediment chronology of this hydrochemically complex and geothermally fed lake. An extensive set of chronological tie points between the equivalent high‐resolution proxy time series of the five sediment sequences allowed transfer of radiometric dates between the basins, enabling interbasin comparison of sedimentation dynamics through time. The resulting reconstruction demonstrates considerable moisture‐balance variability through time, reflecting regional hydroclimate dynamics over the past 1300 years. Between ca 690 and 950 AD , the central and southern basins of Lake Bogoria were reduced to shallow and separated brine pools. In the former, occasional near‐complete desiccation triggered massive trona precipitation. Between ca 950 and 1100 AD , slightly higher water levels allowed the build‐up of high pCO ₂ leading to precipitation of nahcolite still under strongly evaporative conditions. Lake Bogoria experienced a pronounced highstand between ca 1100 and 1350 AD , only to recede again afterwards. For a substantial part of the time between ca 1350 and 1800 AD , the northern basin was probably disconnected from the united central and southern basins. Throughout the last two centuries, lake level has been relatively high compared to the rest of the past millennium. Evidence for increased terrestrial sediment supply in recent decades, due to anthropogenic soil erosion in the wider Bogoria catchment, is a reason for concern about possible adverse impacts on the unique ecosystem of Lake Bogoria.     

6600 years of earthquake record in the Julian Alps (Lake Bohinj,Slovenia)

Sequences of lake sediments often form long and continuous records that may be sensitive recorders of seismic shaking. A multi‐proxy analysis of Lake Bohinj sediments associated with a well‐constrained chronology was conducted to reconstruct Holocene seismic activity in the Julian Alps (Slovenia). A seismic reflection survey and sedimentological analyses identified 29 homogenite‐type deposits related to mass‐wasting deposits. The most recent homogenites can be linked to historical regional earthquakes (i.e. 1348 ad , 1511 ad and 1690 ad ) with strong epicentral intensity [greater than ‘damaging’ (VIII ) on the Medvedev–Sponheuer–Karnik scale]. The correlation between the historical earthquake data set and the homogenites identified in a core isolated from local stream inputs, allows interpretation of all similar deposits as earthquake related. This work extends the earthquake chronicle of the last 6600 years in this area with a total of 29 events recorded. The early Holocene sedimentary record is disturbed by a seismic event (6617 ± 94 cal yr bp ) that reworked previously deposited sediment and led to a thick sediment deposit identified in the seismic survey. The period between 3500 cal yr bp and 2000 cal yr bp is characterized by a major destabilization in the watershed by human activities that led to increases in erosion and sedimentation rates. This change increased the lake's sensitivity to recording an earthquake (earthquake‐sensitivity threshold index) with the occurrence of 72 turbidite‐type deposits over this period. The high turbidite frequency identified could be the consequence of this change in lake earthquake sensitivity and thus these turbidites could be triggered by earthquake shaking, as other origins are discarded. This study illustrates why it is not acceptable to propose a return period for seismic activity recorded in lake sediment if the sedimentation rate varies significantly.     

湖泊沉积物中蛋白质和氨基酸的动态变化

测定了阿哈湖和百花湖沉积物孔隙水中蛋白质和氨基酸的含量。蛋白质含量分别在0．32－1．71mg/ml和0．22－1．38mg/ml之间，氨基酸含量分别在1．15－5．01μg/ml（以含N量计）和1．41－4．16μg/ml之间。两湖沉积物氨基酸含量逐渐增高，表明扩散作用的存在。随着时间的推移，蛋白质在沉积物各层中得到了很好的保存，说明它的分解比较有限。沉积物孔隙水中氨基酸含量和微生物活动有关，氨基酸在27cm以后的阿哈湖沉积物中明显积累，可能指示微生物活动的减弱。     

Holocene climate inferred from glacier extent,lake sediment and tree rings at Goat Lake,Kenai Mountains,Alaska, USA

Lake sediment, glacier extent and tree rings were used to reconstruct Holocene climate changes from Goat Lake at 550 m asl in the Kenai Mountains, south‐central Alaska. Radiocarbon‐dated sediment cores taken at 55 m water depth show glacial‐lacustrine conditions until about 9500 cal. yr BP, followed by organic‐rich sedimentation with an overall increasing trend in organic matter and biogenic silica content leading up to the Little Ice Age (LIA). Through most of the Holocene, the northern outlet of the Harding Icefield remained below the drainage divide that currently separates it from Goat Lake. A sharp transition from gyttja to inorganic mud about AD 1660 signifies the reappearance of glacier meltwater into Goat Lake during the LIA, marking the maximum Holocene (postglacial) extent. Meltwater continued to discharge into the lake until about AD 1900. A 207 yr tree‐ring series from 25 mountain hemlocks growing in the Goat Lake watershed correlates with other regional tree‐ring series that indicate an average summer temperature reduction of about 1°C during the 19th century compared with the early–mid 20th century. Cirque glaciers around Goat Lake reached their maximum LIA extent in the late 19th century. Assuming that glacier equilibrium‐line altitudes (ELA) are controlled solely by summer temperature, then the cooling of 1°C combined with the local environmental lapse rate would indicate an ELA lowering of 170 m. In contrast, reconstructed ELAs of 12 cirque glaciers near Goat Lake average only 34 ± 18 m lower during the LIA. The restricted ELA lowering can be explained by a reduction in accumulation‐season precipitation caused by a weakening of the Aleutian low‐pressure system during the late LIA. Copyright © 2008 John Wiley & Sons, Ltd.     

全新世中期相对稳定的长江水位造成约3000年的湖泊沉积缺失

长江中下游地区浅水湖泊密布,全新世该区湖泊沉积的模式还不清晰。本研究在长江中下游的南漪湖、升金湖和菜子湖这3个湖泊开展了多钻孔AMS^14C测年工作,测年结果显示这些湖泊沉积地层中广泛出现长时间尺度的沉积物缺失。南漪湖湖泊钻孔的沉积物14C年龄介于5668~7828cal.aB.P.,菜子湖湖泊钻孔的沉积物^14C年龄介于6221~7929cal.aB.P.,升金湖围垦区钻孔14C年龄介于6302~7049cal.aB.P.。结合该地区以往湖泊钻孔研究资料,发现全新世长江中下游两岸洼地湖泊存在较广泛的6~3ka的沉积间断。结合长江水位重建资料,笔者提出关于全新世湖泊沉积存有长期间断的新认识:即6~3ka,长江水位相对平稳,湖泊沉积物虽有堆积,但易于被侵蚀搬运造成沉积间断;与此对应的是,在约8~7ka,海面上升造成长江水位较快上升,由于顶托作用,湖泊沉积物持续堆积;在约3ka以来,由于人类活动的影响,以及长江水位的进一步上升,湖泊沉积物也易于堆积,但在一些湖区沉积物也会被侵蚀。在6~3ka之间湖泊沉积物易于被侵蚀的一个可能原因是该时段长江上游来沙来水减少,自然堤易被破坏,对两岸湖泊洼地的封堵作用减少,使得湖泊泥沙易被侵蚀入江。