近60年鄱阳湖东部湖湾水文连通变化及其对湿地植物与候鸟的影响

鄱阳湖碟形湖生物群落分布特征很大程度上受区域与主湖区水文连通性影响。由于水位波动,东部湖湾水文连通性受鄱阳湖主湖体水位影响较为敏感。本文以东部湖湾为例,分析主湖区水位变异程度及其影响,并从连通天数和发生时间等方面定量表征东部湖湾与主湖区的水文连通性,进而讨论水文连通性变化及其对湿地植物生境和候鸟栖息地的潜在影响。结果表明,当水位在13～16 m时,东部湖湾与主湖区存在着良好的水文连通关系,湿地植物适宜生境面积最大。2003年以后,鄱阳湖主湖区水位普遍降低,低枯水位持续时间延长,IHA/RVA法分析表明主湖区水位发生了中等程度改变,整体改变度为40.2%,东部湖湾与主湖区的连通关系发生明显改变,年连通天数减少了46.2 d,变化幅度为15.9%,而非连通期发生时间提前约1个月且年内时间跨度更长。水文连通性减弱造成3 10月东部湖湾平均水位下降了0.6 m,其中9 10月减少了约1 m,使薹草（Carexsp．）和苦草（Vallisneria natans）适宜水深对应的水面面积在多数月份呈增加趋势,特别是9 10月（幅度超过40%）,但枯水提前导致沉水植物面积减少,湿生植物生物量增加。水...     

Preconditioning of an underflow during ice-breakup in a subarctic lake

The fate of inflows into lakes has been extensively studied during summer stratification but has seen relatively little focus during the weak winter stratification, with or without ice-cover. Field observations are presented of groundwater inflow into a shallow bay of a subarctic lake. Atmospheric forcing of the bay during the study period was extremely variable and coincided with spring ice-cover break-up. Two dominant wind regimes were identified; (1) weak wind-forcing (wind speed <5 m s⁻¹ or land-fast ice-cover), and (2) strong wind-forcing (wind speed >5 m s⁻¹ and open water). At a relatively constant temperature of ~3.3°C, the groundwater inflow was closer to the temperature of maximum density than the water in the main body of the lake, which during the observed winter stratification is ~1.2°C. During weak wind-forcing, the stratification within Silfra Bay approximated two-layers as this denser groundwater formed a negatively buoyant underflow. A calculated underflow entrainment rate of 2.8 × 10⁻³ agrees well with other underflow studies. During strong wind-forcing, the water column out to the mouth of the bay became weakly stratified as the underflow was entrained vertically by wind-stirring. Observed periods of mixing can be predicted to occur when turbulent kinetic energy (TKE) production by wind stirring integrated over the underflow hydraulic residence time in the bay exceeds the potential energy associated with the stratification. A decrease of ice cover, as observed in the studied subarctic lake over the last decade, will result in the underflow being more frequently exposed to the strong wind-forcing regime during winter, thereby altering the winter distribution of groundwater inflow within the lake.     

How water exchange and seasonality affect the eutrophication of Murchison Bay,Lake Victoria

Murchison Bay in the Northern part of Lake Victoria has for decades received a daily wastewater load of 0.2% of its volume from Kampala City, through the Nakivubo channel. In spite of this, the Water Treatment Works abstracts raw water from this bay and has been able to produce drinking water of sufficient quality for the capital. This study monitored various physical−chemical components within the bay during 2000−2003 to understand the processes responsible for the acceptable quality of raw water. Four sampling stations were located along a transect from the channel mouth towards the open lake.Resultsshowed that the wastewater did not accumulate in the bay, instead was already strongly diluted 2.5 km from the channel mouth. This caused an abrupt reduction in conductivity and the concentrations of the nutrients total phosphorus (Tot-P), orthophosphate (PO₄-P) and total nitrogen (Tot-N).Inshore−offshore exchange of water was mediated by flows from daily and sub-daily water level fluctuations and wind-driven currents. As a daily average, 2% of the Murchison Bay flowed in and out and the incoming wastewater was diluted 9.7 times.During the dry season from June to August (D2), when the weather was influenced by the south-east monsoon, the thermal stratification in the main lake disappeared and cooler and deoxygenated water from deeper depths entered the bay influencing its water quality.The daily flushing of water in and out of the bay due to water level variation was identified as the main factor diluting the bay water.     

西洞庭湖沉水植物分布格局对环境因子及水文情势差异的响应

沉水植物是湖泊生态系统的重要组成部分,其生产力和分布格局受环境因子特别是水文情势决定.洞庭湖是长江流域重要的大型通江湖泊,近年来受人为干扰和气候变化影响,水文节律与水质等环境因子发生改变,导致沉水植物出现衰退现象,急需开展科学恢复,因此有必要对洞庭湖沉水植物深入研究.本研究选取西洞庭湖为研究区域,于2018年和2019年夏季调查了12处典型生境、98个样点的沉水植物与水深、透明度等11个环境因子,采用独立样本T检验和冗余分析方法对沉水植物与环境因子的关系进行分析,对比年际水文情势变化的影响.结果表明：1）西洞庭湖沉水植物主要在水深较浅、水质更优、水体更为稳定的半阻隔子湖和自由连通的湖湾区分布,在河道及水位波动较大的区域分布较少,有、无沉水植物分布样点间存在显著差异的环境因子为水深、透明度、底泥总磷和pH;2）在有沉水植物分布的样点,沉水植物生物量与pH、水深和水体总磷呈显著相关关系;3）自然连通的季节性淹没湖泊沉水植物生物量在2018年高于2019年,可能与2019年5—8月沉水植物关键生长期出现的涨水过程有关,持续的高水位对沉水植物的生长产生了不利影响.维持自然水文节律、湖泊生境异质性与自由连通性、健康的水质等是恢复西洞庭沉水植物的关键,建议在水深低于3 m、营养盐浓度适中、流速及风浪较小的湖湾区或半阻隔湖泊开展沉水植物恢复.     

太湖近代沉积物中重金属元素的累积

利用210Pb、137Cs定年技术,对来自太湖不同生态和沉积特征的三个湖区的沉积物柱状样品进行了定年,用ICP—AES分析了沉积物中重金属等元素的含量,分析了太湖沉积物中重金属的累积特征及其成因.污染较重、蓝藻水华暴发频繁的梅梁湾沉积物中的重金属含量在近25年来逐年增加;太湖上游风浪较大的夹浦湖区表层10cm沉积速率大、粒度粗,除表层1cm外,1—10cm沉积物中各种重金属含量都较低,且层间变化剧烈;下游湖区正逐渐草型化的胥口湾除表层3cm外,沉积物中重金属的含量自底层向表层大致呈不断下降的趋势.研究表明,不同年代的太湖沉积物中重金属含量差异很大,明显大于不同湖区间沉积物重金属平均含量间的差异.水动力作用引起的沉积物粒度分异很可能是影响沉积物中重金属积累的一个重要因素.总体上太湖沉积物中重金属的污染比较轻微,但已经有一定程度的Cd污染,梅梁湾沉积物中自上世纪70年代开始明显积累Cd,其他重金属元素的积累也逐渐增加,值得关注.     

射阳湖历史变迁研究

射阳湖是苏北历史上著名的大湖。早全新世因受海侵影响,本区是里下河浅水海湾的一部分;中全新世时,由于西冈等岸外砂堤的形成,本区成为古泻湖,后因海岸东迁,淡水冲灌,古泻湖逐渐演变为淡水湖。1128年黄河夺淮后,大量泥沙进入湖区,湖区淤积迅速,成为沼泽型湖泊,加之人类活动因素的显著影响,射阳湖逐渐演变为里下河平原的一部分。     

大型浅水湖泊太湖波浪特征及其对风场的敏感性分析

以空间均匀的实际风场为驱动,利用SWAN模式模拟了太湖波浪场,结果表明:SWAN模式能够较好的模拟太湖波浪的生成与传播,适用于大型浅水湖泊(太湖);同时分析了该风场驱动下下太湖风浪谱,波浪的绝对频率主要集中在0.45～1.0 Hz的中高频率段;风向与波向具有高度一致性.在同一风速下,太湖不同区域波浪成长稳定时间不同,湖心区稳定的谱峰频率在0.342～0.585 Hz之间,湾区及西山岛附近狭长水域稳定的谱峰频率在0.447～0.765 Hz之间;在同一区域,风速增大,波浪稳定时间减少,谱峰频率沿低频推移,在湖心区谱峰频率最小不低于0.340 Hz,湾区、西山岛附近狭长水域最小不低于0.447 Hz;风向的改变对湾区及西山岛附近狭长水域的波浪频谱形状影响较大.     

Distribution and origin of biologically available phosphorus in the water of the Meiliang Bay in summer

The investigation and continuous monitoring with an innovative iron oxide embedded cellulose acetate membrane (FeO/CAM) on the concentrations of biologically available phosphorus (BAP) were conducted in the Meiliang Bay of the Taihu Lake during summer in 2004. The results showed that the concentrations of dissolved (FeO-DP), particulate (FeO-PP) and total bioavailable phosphorus (FeO-P) had similar horizontal distribution. The BAP concentrations were the highest in those estuaries in the northern bay. With the decrease of the distance to the estuary or long shore, there was little difference between BAP concentrations in an open lake area. During the observation period, algal blooms occurred in most waters of the northern bay, which was reflected from the high concentrations of chlorophyll a (Chl-a). While they were not highest in the estuarine waters of those major rivers, this is the case for the BAP concentrations. The concentrations of Chl-a had a significantly positive correlation with those of bioavailable phosphorus in the open area of the Meiliang Bay. With the sediment resuspension induced by wind and wave, BAP concentrations increased in a short-term, indicating that the riverine P inputs mainly contribute to the concentrations of BAP in the estuarine water while internal P release was the major source of BAP in the open lake area. In the eutrophic shallow lake, the blooms of alga may cause pH increase and further result in internal P release. The above results showed that the new membrane of FeO/CAM can be used to monitor the concentrations of BAP and provide the scientific justifications for the control strategy of the lake eu-trophication.     

Active fault and water loading are important factors in triggering earthquake activity around Aswan Lake

Aswan Lake started impounding in 1964 and reached the highest water level so far in 1978 with a capacity of 133.8 km³, thus forming the second largest man-made lake in the world. An earthquake of magnitude 5.3 (Ms) took place on 14 November 1981 along the most active part of the E-W Kalabsha fault beneath the Kalabsha bay (the largest bay of the lake). This earthquake was followed by a tremendous number of smaller events that continue till now. A radio-telemetry network of 13 seismic short period stations and a piezometer network of six wells were established around the northern part of the lake.Epicenters were found to cluster around active faults near the lake. The space-time distribution and the relation of the seismicity with the lake water level fluctuations were studied. Six years after flooding the eastern segment of the Kalabsha fault, strong seismicity began following the main shock of 14 November 1981. It occurred four days after the reservoir had reached its seasonal max level. The effect of the North African drought (1982 to present) is clearly seen in the reservoir water level. As it decreased and left the most active fault segments uncovered, the activity (Gebel Marawa area) decreased sharply. Also, the shallow activity was found to be more sensitive to rapid discharging than to the filling. This study indicates that geology, topography, lineations in seismicity, offsets in the faults, changes in fault trends and focal mechanisms are closely related. No relation was found between earthquake activity and both-ground water table fluctuations and water temperatures measured in wells located around the Kalabsha area.     

全新世内蒙南缘黄旗海湖面的波动

黄旗海是一封闭湖泊,气候是控制其湖面变化的主要因素。地貌、沉积物、地球化学分析及历史考古资料均证实,一万年以来湖面在总体收缩下降过程巾不断地波动着。全新世初期,湖面扩张抬升,9000a B.P.前后湖面达最高(1340m),湖面面积也最大(约560km~2),其后,湖面持续地收缩下降。     

Distribution and origin of biologically available phosphorus in the water of the Meiliang Bay in summer

The investigation and continuous monitoring with an innovative iron oxide embedded cellulose acetate membrane (FeO/CAM) on the concentrations of biologically available phosphorus (BAP) were conducted in the Meiliang Bay of the Taihu Lake during summer in 2004. The results showed that the concentrations of dissolved (FeO-DP), particulate (FeO-PP) and total bioavailable phosphorus (FeO-P) had similar horizontal distribution. The BAP concentrations were the highest in those estuaries in the northern bay. With the decrease of the distance to the estuary or long shore, there was little difference between BAP concentrations in an open lake area. During the observation period, algal blooms occurred in most waters of the northern bay, which was reflected from the high concentrations of chlorophyll a (Chl-a). While they were not highest in the estuarine waters of those major rivers, this is the case for the BAP concentrations. The concentrations of Chl-a had a significantly positive correlation with those of bioavailable phosphorus in the open area of the Meiliang Bay. With the sediment resuspension induced by wind and wave, BAP concentrations increased in a short-term, indicating that the riverine P inputs mainly contribute to the concentrations of BAP in the estuarine water while internal P release was the major source of BAP in the open lake area. In the eutrophic shallow lake, the blooms of alga may cause pH increase and further result in internal P release. The above results showed that the new membrane of FeO/CAM can be used to monitor the concentrations of BAP and provide the scientific justifications for the control strategy of the lake eutrophication.     

Periodic drainage of ice-dammed lakes as a result of variations in glacier velocity

Previous discussions of the catastrophic drainage of ice-dammed lakes have centred on mechanisms where characteristics of the lake are crucial to drainage initiation, for example dam flotation or tunnel formation at a critical lake depth. This paper describes a mechanism for lake drainage where drainage initiation depends on the characteristics of the glacier and is independent of the characteristics of the lake. Prediction of this mechanism must be based on glacier dynamics, whereas the mechanisms most commonly discussed previously are best predicted primarily on the basis of lake evolution. An ice-dammed lake at the margin of the glacier Solheimajokull, in southern Iceland, was observed to drain rapidly into the sub- or englacial drainage system, supplying water and debris to the bed or interior of the glacier. Geomorphological evidence suggests that the lake drains and refills periodically, discharging up to 13300 m³ of water into the glacier-hydrological system. The depth of the maximum lake is insufficient to cause either flotation of the ice margin or tunnel opening by plastic deformation of the ice, and we suggest that sudden drainage is related to ice-bed separations associated with specific glacier flow states rather than to a critical lake depth threshold. This mechanism of lake drainage has implications for conditions at the glacier bed, for the development of basal ice and for the entrainment of debris into the glacier, as well as for the prediction of potentially hazardous catastrophic drainage events and jokulhlaups from ice-dammed lakes.     

太湖梅梁湾水土界面反硝化和厌氧氨氧化

运用无扰动芯样实验室内流动培养、稳定同位素示踪、同位紊气态产物测定及同位素配对技术,对太湖梅梁湾北部到南部的4个梯度样点的水土界面反硝化和厌氧氨氧化速率进行研究.结果表明,梅梁湾内及湾外开敞湖区4个样点的水土界面反硝化脱氮速率为(46.36±13.26)-(16.34±22,74)μmol/(m~2·h),厌氧氨氧化脱氮速率为(7.50±2.21)-(2.05±2.90)～mol/(m~2.b).梅梁湾北部河口区水土界面总脱氮能力明显高于梅梁湾南部及开敞湖区.通过对脱氮过程的进一步研究发现.北部脱氮过程主要以上覆水硝酸盐为底物的非耦合反硝化过程(D_w)为优势过程,而梅梁湾外开敞湖区则以沉积物硝化过程耦合控制的反硝化(D_n)为主.影响D_n、D_w在反硝化中比重的主要因素是沉积物溶氧侵蚀深度和上覆水NO_3~-.浓度的差异;梅梁湾厌氧氨氧化脱氮比例占总脱氮比例为12%-14%,湾外开敞湖区则占11%,影响其比例差异的主要因子是反硝化强度的大小及其反硝化中间产物--亚硝酸盐含量的差异.     

太湖梅梁湾水动力及相关过程的研究

太湖是位于长江下游的一个大型水湖泊,水动力过程和要素对浅水湖泊的环境演化有着复杂和深远的影响,本文基于１９９８年开展的有关太湖梅梁湾的水动力过程的野外调查结果,总结了梅梁湾在夏季盛行风向条件下湖流特征,发现了梅梁湾在夏季偏南风条件下,表层湖流以顺时针环流为主要特征,但在湾内靠近梁溪河口地区,流场受地形影响而有所不同,反映在叶绿素浓度和总磷、总氮浓度分布上,因受湖流影响较大而富集在梁溪河口周转,即偏     

五里湖富营养化过程中水生生物及生态环境的演变

五里湖是太湖西北部一个小型浅水湖湾,是无锡市的饮用水源和主要风景游览区。50年代时,该湖基本保持着原始状态,全湖以大型水生植物占优势。湖水清澈见底,水质为中营养水平,溶氧接近饱和,对外来的N、P污染冲击具有很强的缓冲能力。底泥的氧化程度较高,磷和有机物含量仅为0.023％和0.75％。浮游藻类受到了大型水生植物的强烈抑制,年均数量为26.7×10~4个/L,以硅藻和隐藻为主;从春季至秋季,随着大型水生植物的增长,浮游藻类数量大幅度减少。浮游动物多达190种,年均数量为5660ind./L。大型底栖动物较多,以日本沼虾和螺、蚌类为主。鱼类资源十分丰富,63种鱼中以凶猛性鱼类占优势,并有较多的底栖性鱼类。 自50年代以来,大约有1/2的湖面被围垦,沿岸带生态条件被破坏,失去了最适合于大型水生植物生长的浅水区。加之60年代后期在全湖放养草鱼,水生植被遭到彻底毁灭。外源污染加剧,引起了水质的严重富营养化。围垦和修建水闸隔断了五里湖与太湖间的通道,限制了两个水体间的水流交换,妨碍了污染物的稀释扩散,使得来自无锡市区的污水成了五里湖的主要补给水源,加速了富营养化的进程。五里湖水质已达重富营养水平,透明度小于0.5m,缺氧较为严重。营养物在底泥中大量积累,TP和TOC含量分别增高了4.17倍和1.87倍。在春末     

历史时期希门错湖泊沉积色素记录的古环境变化

湖泊沉积物中色素的含量,种类以及相应的参数是研究湖泊初始生产力和湖泊环境的有效手段之一。本文根据青藏高原东部希门错短柱岩芯ＸＭ９２０１沉积物的色素指标的综合判别,讨论了该地区过去２０００多年来的古环境变化过程和特点,对比分析我国东西部气候记载及冰芯研究,探讨了各气候事故表现形式的异同点。     

Zooplankton Community Structure of Çavuşcu and Eber Lakes in Central Anatolia Struktur von Zooplankton-Gemeinschaften im Çavuşcu Lake und im Eber Lake in Zentralanatolien

This research has been undertaken to determine the zooplanktonic fauna (Rotatoria, Crustacea) and their seasonal distribution in two lakes with different characters. Çavu?cu lake has a surface area of 1000 ha with a maximum depth of 4 m and is classified as an oligo-mesotrophic lake. Eber lake has a surface area of 5200…17000 ha with a maximum depth of 2.5 m and is classified as an eutrophic lake. Zooplankton samples have been collected seasonally between the period of 1990 to 1993 from three stations with a zooplankton net of 44 μm mesh size. From Çavu?cu lake totally 50 Rotifera, 2 Copepoda, and 7 Cladocera species; 49 phytoplankton genera and 5 macrophytes have been identified while, 37 Rotifera, 3 Copepoda, 5 Cladocera; 45 phytoplankton genera and 6 macrophytes have been identified from Eber lake. 13 new rotifer records for the Turkey were found, which were Brachionus diversicornis, Macrochaetus collinsi, Lecane stichaeta, Cephalodella sterea, Cephalodella auriculata, Trichocerca iernis, Encentrum saundersiae. Pompholyx complanata, Floscularia ringens, Conochilus natans, Filinia pejleri, Rotaria rotatoria, and Philodina megalotrocha.     

Survey of dioxins in Tokyo Bay bottom sediment

This paper examines dioxin profiles in bottom sediments from Tokyo Bay, Japan using sedimentation dating based on 210Pb measurements and dioxin measurements based on particle size distributions. Dioxin concentrations in surface sediment ranged from 3.2 to 52 pg-TEQ g(-1), with the concentrations in the bay back and central region being higher than those at the front of the bay. The vertical dioxin concentration in sediment core samples showed peak levels from years 1962 to 1980, with the maximum being 110 pg-TEQ g(-1). Principal component analysis indicates that the main source of dioxins in bottom sediment from the back of bay are herbicides such as CNP, while in the front of bay atmospheric deposition due to incineration activities are responsible. Dioxins in bottom sediment were mainly found in the particles <75 microm in size.     

洞庭湖水面面积与城陵矶水位之间的绳套关系

洞庭湖是我国第二大淡水湖,与长江连通,在防洪抗旱和湿地生态保护等方面具有重要的现实意义.采用Terra/MODIS L1B遥感数据,提取了2000-2012年洞庭湖水面面积,结合同期城陵矶水位观测数据,建立了城陵矶水位与洞庭湖水面面积的绳套关系曲线.分析结果表明:2000-2012年间,洞庭湖水面面积呈现总体减少的趋势;在季节上表现为规律性的涨落,具有明显的涨(4-6月)-丰(7-9月)-退(10-12月)-枯(1-3月)的水文特征;在空间格局上表现为由湖体中心向外扩张,随后由外向湖体中心逐渐收缩的变化过程;洞庭湖水面面积与城陵矶水位之间具有较高的相关性,但不同时期的相关系数存在一定的差异:枯水期二者相关性较低,丰水期相关性最高,涨水期和退水期相关性较高;这种差异与各个时期的主导因素不同有关,长江来水对枯水期、丰水期的绳套关系影响较大,其中东洞庭湖最为明显;不论丰水年(2002年)或干旱年(2011年),洞庭湖水面面积变化与城陵矶水位之间的相关性均较高.研究结果对于深入认识江湖关系的宏观复杂性、长江中下游地区以及洞庭湖水域洪涝灾害的预防和治理都具有积极的意义.     

Magnetic studies on Kilauea Iki lava lake,Hawaii

Ground surveys made during August, 1961, show large vertical magnetic intensity anomalies associated with the partly lava filled crater of Kilauea Iki. A vertical magnetic variation of 11,600 gammas occurs along a north-south profile across the crater, the maximum being on the north rim of the crater and the minimum on the south edge of the encrusted lava lake below the south rim. An east-west profile shows less vertical magnetic variation, with lake-surface measurements 1500 to 2500 gammas lower than measurements on the east rim of the crater. Computed anomalies using two-dimensional potential field graticules are in good agreement with the observed anomalies and support the following conclusions: 1) Average measured values of remanent magnetization of 10^?2 cgs units and susceptibilities of 10^?3 cgs units give reasonable magnitudes to the computed anomalies. 2) The remanent magnetization is parallel to the earth’s present magnetic field. 3) The maximum vertical magnetic field value in the north-south profile is the result of reinforcement of the positive terrain effect of the north rim of the crater and the positive edge effect of the north side of the lava lake. 4) The minimum value in the same profile is the result of reinforcement of the negative terrain effect at the base of the south rim of the crater and the negative edge effect of the south side of the lava lake. 5) Variation in the east-west magnetic profile is less because the terrain and edge effects of the horizontal components of the earth’s magnetic field and remanent magnetization approach zero. Changes in vertical magnetic field values as the lake solidifies will be maximum at the north edge of the lava lake, but more consistent changes of the opposite sign will occur on the south side of the lava lake. Total change will be approximately + 2300 gammas between the August 1961 measurement at station S6 and the value at that point when the entire lava lake has cooled below 400° C. The maximum rate of change at station S6 will occur when the 500° C isotherm is 35 to 65 meters below the surface and will be about 28 gammas per meter of lowering of the 500°C surface. Because of the steep magnetic anomalies associated with the lava lake and crater rims, the permanent magnetization presently forming in the cooling lake crust will have inclinations as much as 12° less than the average 37.5° inclination in the Kilauea area.