The most acidified Austrian lake in comparison to a neutralized mining lake

This study investigated two mining lakes located in the north of Lower Austria. These lakes arose 45 years ago when open cast lignite mining ceased. The lakes are separated by a 7-m wide dam. Due to the oxidation of pyrite, both lakes have been acidified and exhibit iron, sulphate, and heavy metal concentrations several orders of magnitude higher than in circumneutral lakes. The water column of both lakes is divided into two layers by a pronounced chemocline. The smaller mining lake (AML), with pH close to of 2.6, is the most acidic lake in Austria, whereas flooding with stream water and by drainage from the surrounding fields neutralized the adjacent larger pit lake. The goal of our study was to investigate the effect of flooding on its physical, chemical and biological properties, in comparison to the pristine AML. Even relative to other extremely acidic lakes, the flora and fauna in the AML was reduced and composed of only two flagellate, one ciliate, and one rotifer species. The simplified pelagic food web in the mixolimnion consisted of heterotrophic bacteria, the mixotrophic flagellates Chlamydomonas acidophila and Ochromonas sp., the ciliate Oxytricha sp., and the rotifer Cephalodella sp. The latter two are as yet undescribed new species. The heliozoan Actinophrys sp. that may act as top predator occurred only in low abundance. The euglenid Lepocinclis buetschlii formed a stable deep chlorophyll maximum (DCM) at 7 m depth. Highest cell numbers of L. buetschlii in the DCM exceeded 10⁸ L^?1. The neutralized mining lake harboured higher plankton diversity similar to that of natural circumneutral lakes. A peak of at least 16 different phytoplankton taxa was observed during summer. The zooplankton consisted of several copepod species, daphnids and other cladocerans, and at least six different rotifer species. Several fish species occurred in the neutralized lake. Although the effect of non-permanent flooding was largely sustainable, interannual fluctuations of the pH affected the plankton community and reduced its species diversity.     

蚌湖与鄱阳湖水量交换关系的分析

根据蚌湖和鄱阳湖修水站的水位同步观测资料,结合湖区地形,分析蚌湖与鄱阳湖的水量交换关系,并利用三峡工程对鄱阳湖修水,星子,都昌站水位影响的预测结果,讨论三峡工程对蚌湖水情的影响。     

青海湖水位变化与湖区气候要素的相关分析

对湖区现有气象和水文资料作相关分析后得出,影响青海湖水位或水量的主要气象因子是前期降水量、当年蒸发量、水汽压饱和差及融冰期开始后的气温。影响湖周水系流量的气象因子则视发源地远近而异：源于近处的短程河溪的流量受制于当时降水量;源于冰山雪岭的较长河流的流量,由发源地及其流域的固态水储量和当时热状况而定。     

Strategies of lake sanitation

Lake sanitation measures must be planned in such a way that under consideration of the ecological requirements the trophic state which is needed in order for the lake to fulfill its designated purpose can be achieved with a sufficient degree of certainty. This is obtainable solely by limiting the influx of phosphorus compounds. The influencing factors as well as a knowledge of the local conditions which must be taken into consideration so that planning can be undertaken are described and discussed. The limits and effectiveness of technical and administrative single and joint control measures are presented with regard to the source of the phosphorus compounds. Presented at the International Conference on Lake Restoration at Zürich, 3–4 November 1986     

OSL dating of past lake levels for a large dammed lake in southern Tibet and determination of possible controls on lake evolution

Fluvio‐lacustrine terraces along Phung Chu (river) on the central southern Tibetan Plateau indicate that a large palaeo‐dammed‐lake formerly existed in this area. Based on landscape survey, optically stimulated luminescence (OSL) dating and sedimentary analyses, this research shows that the Phung Chu was blocked and a dammed‐lake over 2500 km² in size formed before 30 ka ago. OSL dating analysis suggests the fluvio‐lacustrine sediments were well bleached and yield accurate age estimates for two lake drainage events. The first drainage event took place after 30 ka, resulted in river incision and formed a high terrace at 50 m height from the present river level. The second drainage happened after 3.7 ka, resulted in further river incision and formed the second terrace at 25 m height from the present river level. According to the distribution of the fluvio‐lacustrine sediments, active normal faults (particularly the Kharta Fault) in this region and the high gradient slopes after Phung Chu enters the Yö Ri gorge, seismically‐induced landsliding is regarded as highly likely to have been the cause of river blockage and associated formation of a dammed‐lake, although glacial damming is also a possible cause. The volume of drainages from this dammed‐lake may have led to catastrophic flooding and analogous modern lakes represent significant geo‐hazard risks to down‐river human settlements. As dammed‐lakes are special phases in fluvial evolution, often involving river blockage, breakthrough and drastic catchment change, these processes can reveal how tectonic or climatic events modify landforms. However, such tectonic‐derived landform changes can also impact palaeo‐climate of the region. Thus this study has added new evidence regarding the evolutionary history of a dammed lake including its formation, duration, extent and final drainage, which is crucial for understanding its general landscape process mechanisms and for better assessing geo‐hazard risks. Copyright © 2016 John Wiley & Sons, Ltd.     

Zonal features of lake acidification

Zonal features of water acidification in small lakes of European Russia are analyzed. The conditions under which the process can develop are evaluated. Studies of water chemistry variations and formulation of various criteria used to assess water acidification made it possible to prove the development of the process in the humid part of the area under study, i.e., in tundra, taiga, and forest regions. The leading natural and anthropogenic factors, whose combination governs the acidification mechanism and secondary effects are discussed. The concentrations of some metals (Al, Zn, Pb, and others) are proved to increase in waters with low pH, as well as at an increase in water color index. Critical loads of acid precipitation are evaluated and the values of their exceedance in lakes in different natural-climatic zones.     

Hydrocarbons in a wilderness lake

The hydrocarbons found in Green Lake, Ontario, Canada, are believed to be of natural origin coming from plant and animal organisms.     

龙感湖水生植被

于１９９３年９月对龙感湖水生植被及环境进行了调查研究。龙感湖有水生植物２６科３８属５０种,依据优势种群划分９个群丛,其分布面积２８３．５ｋｍ＾２,占全湖总面积的８９．７％,植被现有年生产力达２１４７７３０ｔ,对渔业生产和生态环境具有十分重要的意义。建议对该湖植被应合理开发利用,如果围网养鱼得到广泛地发展,渔业生产潜力每年可达４１８１．８ｔ。     

Oxygen patchiness in a lake

The presence and extent of small scale vertical structure in dissolved oxygen were investigated in a tropical Australian lake. At a 9 m deep site an extremely high oxygen patch appeared near the bottom boundary. Light levels reaching the bottom boundary during the life of the patch exceeded 10 µEinst m^–2 s^–1. The patch remained for 1.5 h before gradually reaching ambient oxygen levels. The patch's disappearance coincided with decreasing light levels during the late afternoon. Differences in the extent of oxygen vertical patchiness between deep (16 m) and shallow (9 m) sites were also observed. At the deep site, the distribution of oxygen steps over the water column coincided largely with the distribution of temperature steps. This indicates the dominance of physical processes at that site. At the shallow site, marked vertical patchiness in oxygen was observed with no similar patchiness in temperature. This indicates the prevalence of biological and chemical processes.     

湖泊水环境模糊数学评价模型及其在富营养化排序中的应用

本文根据模糊水文学关于水体“清洁”与“污染”之间无明确界面,在识别过程中具有模糊性的论点,提出湖泊水环境评价的模糊数学模型。应用此模型对我国12个湖泊富营养化污染状况进行排序,结果与实际相符,文中提出的评价模型,原则上也适用于其他环境领域的评价工作。     

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。     

底泥释磷及其对杭州西湖富营养化的影响

杭州西湖是一个小型浅水湖泊,底泥由上部藻骸腐泥和下部泥炭层构成,其显著特点是有机碳含量特别高,氮含量也相当高,而磷的富集程度相对较低。通过实验室和现场模拟研究,考察了pH值、温度、溶解氧、氧化还原电位及上覆水种类等环境因素对底泥释磷量和释磷速率的影响。上覆水pH值在6.5—7.0范围内底泥释磷量最低;在较高或较低pH值时,释磷量倍增。升高水温或降低上覆水溶解氧浓度均能加速释磷。实验室模拟西湖底泥最大释磷量为0.368μgP/g。夏季现场模拟平均释磷速率为1.02mg P/m~2·d;由此估算底泥释磷量达1.346tP/a,相当于年平均外部入湖磷负荷的36.4％。底泥释磷对西湖富营养化起着不容忽视的影响。     

滇池化学需氧量及营养盐负荷量的预测

本文采用多元线性回归及合田健模型分别对滇池有机污染及富营养化的主要因子COD、TN、TP进行预测,并将污染负荷量分至各点源。定量说明污水处理厂对治理城市污水的积极作用,为流域进行污染治理提供了科学依据。     

Numerical model of crater lake eruptions

We present results from a numerical investigation of subaqueous eruptions involving superheated steam released through a lake mimicking the volcanic setting at Mt. Ruapehu. The simulations were conducted using an adaptive mesh, multi-material, hydrodynamics code with thermal conduction SAGE, (Simple Adaptive Grid Eulerian). Parameters investigated include eruption pressure, lake level and mass of superheated vapor. The simulations produced a spectrum of eruption styles from vapor cavities to radial jets that resulted in hazards that ranged from small-scale waves to high amplitude surges that reached and cascaded over the edge of the crater rim. There was an overall tendency for lake surface activity to increase (including wave amplitude) with increasing mass of superheated vapor and eruption pressure. Surface waves were induced by the formation and collapse of a gas cavity. The collapse of the cavity is considered to play a major role in the characteristic features observed during a subaqueous eruption. The additional mass of superheated vapor produced a larger cavity that displaced a larger area of the lake surface resulting in fast moving surges upon the collapse of the cavity. High lake levels (>90 m) appear to suppress the development of explosive jetting activity when eruption pressures are <10 MPa. At very large eruption pressures (>10 MPa), vertical jets and radial ejections of steam and water can occur in water depths >90 m. Less explosive eruption styles can produce hazardous events such as lahars by the outward movement of surface waves over the crater rim.     

太湖与流域治理

太湖流域是中国最重要的经济区.流域面积36500km~2,六分之五为平原,有上海、无锡、苏州、杭州等重要城市.以太湖为中心和其周围的河网构成了流域水系的特点.治理和开发的目标是防洪、供水、水资源保护和航运.治理的方案充分发挥太湖的调蓄作用,规划了十项骨干工程,可使流域内收到十分显著的综合效益.其中以望虞河和太浦河最为重要,可以解决80％上游洪水的出路和从长江引水2.8km~3,缓解防洪和水污染的压力,建议及早兴建.     

Evaluation of lake restoration in Sweden

A large portion of the water resources in Sweden have been afflicted by acidification and eutrophication. Governmental grants have been allocated for external and internal restoration measures for nutrient reductions, and are at the moment given for liming operations in acidified lakes. Objective and results of the Swedish lake restoration programme during the last 20 years are discussed and evaluated. Presented at the International Conference on Lake Restoration in Zürich, 3–4 November 1986     

Revisiting lake sediment budgets: How the calculation of lake lifetime is strongly data and method dependent

Lake sedimentation has a fundamental impact on lake lifetime. In this paper, we show how sensitive calculation of the latter is to the quality of data available and assumptions made during analysis. Based on the collection of a large new dataset, we quantify the sediment masses (1) mobilized on the hillslopes draining towards Lake Tana (Ethiopia), (2) stored in the floodplains, (3) transported into the lake, (4) deposited in the lake and (5) delivered out from the lake so as to establish a sediment budget. In 2012–2013, suspended sediment concentration (SSC) and discharge measurements were made at 13 monitoring stations, including two lake outlets. Altogether, 4635 SSC samples were collected and sediment rating curves that account for land cover conditions and rainfall seasonality were established for the 11 river stations, and mean monthly SSC was calculated for the outlets. Effects of the floodplain on rivers' sediment yield (SY) were investigated using measurements at both sides of the floodplains. SY from ungauged rivers was assessed using a model that includes catchment area and rainfall, whereas bedload and direct sediment input from lake shores were estimated. As a result, the gross annual SY was c. 39.55 (± 0.15) Mt, dominantly from Gilgel Abay and Gumara Rivers. The 2.57 (± 0.17) Mt sediment deposited in floodplains indicate that the floodplains serve as an important sediment sink. Moreover, annually c. 1.09 Mt of sediment leaves the lake through the two outlets. Annual sediment deposition in the lake was c. 36.97 (± 0.22) Mt and organic matter accumulation was 2.15 Mt, with a mean sediment trapping efficiency of 97%. Furthermore, SSC and SY are generally higher at the beginning of the rainy season because soils in cultivated fields are bare and loose due to frequent ploughing and seedbed preparation. Later in the season, increased crop and vegetation cover lead to a decrease in sediment production. Based on the established sediment budget with average rainfall, the lifetime of Lake Tana was estimated as 764 to 1032 years, which is shorter than what was anticipated in earlier studies. The sedimentation rate of Lake Tana (11.7 ± 0.1 kg m^?2 yr^?1) is in line with the sedimentation rates of larger lakes in the world, like Lake Dongting and Lake Kivu. Copyright © 2017 John Wiley & Sons, Ltd.