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1.
叶绿素浓度垂向变化影响遥感反演精度和富营养化评价。湖泊水体叶绿素浓度影响因子众多,其垂向变化规律仍是当前的研究难点。以广东省3个典型湖泊的叶绿素浓度、营养盐浓度、藻种及粒径结构等数据,分析了叶绿素浓度垂向变化规律与影响机制,并用不同函数来拟合建模。结果表明：各水体不同时期拟合函数各异,需要分时间、分区域讨论;浅水区域（或浅水湖泊）叶绿素浓度自上而下先减后增,用傅立叶变换拟合效果佳;深水区域的规律是自上而下递减明显,用高斯函数拟合效果较好。浅水区域,光照和水温对垂向浓度的影响在本研究中体现不明显,但营养盐及底泥对其影响较明显;深水区域的垂向浓度变化是藻种、水温、营养盐等因子共同作用的结果。 相似文献
2.
《Polar Science》2009,3(4):262-271
We investigated the vertical structure of physicochemical properties in 27 lakes at Skarvsnes and Langhovde, Syowa Oasis, East Antarctica, from December 2003 to February 2004. The lakes were classified into three types based on their origin and geographical characteristics: non-marine relic lakes, marine relic and lotic lakes, and marine relic and lentic lakes. We describe the physicochemical characteristics of each lake type. When the non-marine relic lakes were partly covered with ice, the water column was stratified beneath the ice. In the non-marine relic lakes, during the season with no ice cover, physicochemical parameters were uniform throughout the water column, probably due to frequent vertical mixing induced by wind force and thermal convection within the shallow basins. Similarly, in marine relic and lotic lakes, lake waters appeared to be completely mixed because of a large inflow of meltwater from glaciers and outflow to other lakes and the coastal sea. In the marine relic and lentic lakes, except for Lake Himebati-ike, the lake water was vertically stratified with a strong halocline. In Lakes Suribati-ike and Hunazoko-ike, salinity was very high (up to 20%) due to evapoconcentration. Lake Suribati-ike is a meromictic lake, with a monimolimnion developed below 10 m water depth. 相似文献
3.
The extensive debris that covers glaciers in the ablation zone of the Himalayan region plays an important part in regulating ablation rates and water availability for the downstream region. The melt rate of ice is determined by the amount of heat conducted through debris material lying over the ice. This study presents the vertical temperature gradients, thermal properties in terms of thermal diffusivity and thermal conductivity, and positive degree-day factors for the debris-covered portion of Lirung Glacier in Langtang Valley, Nepal Himalaya using field-based measurements from three different seasons.Field measurements include debris temperatures at different debris thicknesses, air temperature, and ice melt during the monsoon(2013), winter(2013), and pre-monsoon(2014) seasons. We used a thermal equation to estimate thermal diffusivity and thermal conductivity, and degree-day factors(DDF) were calculated from cumulative positive temperature and ice melt of the measurement period. Our analysis of debris temperature profiles at different depths of debris show the daily linear gradients of-20.81 °C/m, 4.05 °C/m, and-7.79 °C/m in the monsoon, winter, and pre-monsoon seasons, respectively. The values of thermal diffusivity and thermal conductivity in the monsoon season were 10 times greater than in the winter season. The large difference in these values is attributed to surface temperature and moisture content within the debris. Similarly, we found higher values of DDFs at thinner debris for the pre-monsoon season than in the monsoon season although we observed less melting during the pre-monsoon season. This is attributed to higher cumulative temperature during the monsoon season than in the pre-monsoon season. Our study advances our understanding of heat conductivity through debris material in different seasons, which supports estimating ice melt and discharge from glacierized river basins with debris-covered glaciers in the Himalayan region. 相似文献
4.
Long-term temperature data on a soil layer 3.2 m in thickness have been used in the differentiation of a topographically highly complicated permafrost on the territory of Transbaikalia. It was found that the geographical ranges are most clearly identified from mean annual temperature values. The schematic map displays the areas with the temperatures –4 to–1°C,–1 to 1°C and 1 to 4°C which are in good agreement with the permafrost distribution pattern (continuous and discontinuous permafrost, and permafrost islands). A classification of the thermal conditions of soils is carried out according to the highest mean monthly temperature at all depths. We identified four types which are characterized by the qualitative assessment as warm, moderately warm, cold and very cold. A relevant cartographic model shows the distribution of the thermal regime of soils for a warm season. The dot method was used to provide a clear display of available information on soil temperature, and it was possible to show the existence of small areas of the types of thermal regime and their fragmentation. Current changes in soil temperature were determined for August, which are in good agreement with regional changes in ground air temperature. In either case, we observed positive linear trends. Assessments of thermal resources of the soil layer and their geographical patterns belonging to the widespread depression-valley and valley natural systems as well as to the relatively planate surfaces of Transbaikalia can be used for scientific and practical purposes. 相似文献
5.
Below-ground relationships of soil texture, roots and hydraulic conductivity in two-phase mosaic vegetation in South-east Spain 总被引：2，自引：0，他引：2
Results led to the development of a conceptual model, which describes that the presence of deep larger diameter roots in shrub areas form large open channels at deeper soil depths, facilitating deep-water percolation, while presence of thin shallow roots in grass areas form small open channels at shallow depths, causing water to remain within shallow depths. Over time these roots systems will alter their environment and facilitate storage and uptake of water and nutrient availability. The difference in rooting depth will decrease the competition for water between the shrub areas and grass areas and cause differences in water distribution and availability. 相似文献
6.
Stuart D. Ludlam 《Journal of Paleolimnology》1996,16(2):111-131
Five important features appear in rough order from the surface downwards in physical and chemical profiles from high arctic coastal meromictic lakes. These features are: (1) a supersaturated oxygen maximum, (2) the center of the oxycline, (3) a thermal maximum, (4) a major absorption maximum, and (5) an anoxic stratum. The depth of the absorption maxima and the top of the anoxic strata are both statistically correlated to light penetration and to each other. The depth of the thermal maximum also shows a statistical correlation to light penetration among lakes with a relatively shallow chemocline. The temperature of the thermal maximum appears to be maintained by inputs of light energy while the oxygen maximum is maintained to a large extent by photosynthesis. Thus, these major features are all influenced by light penetration. With the exception of the supersaturated oxygen maximum, all of the above features are dependent for their existence upon the primary chemocline stabilizing the water column. Apparently, in at least some lakes, a near surface secondary chemocline or cool (ca. 4°C) secondary inverse thermocline will enhance the stability of the water column above the primary chemocline sufficiently to allow a supersaturated oxygen maximum to develop in this region. However, the supersaturated oxygen maximum can extend into the primary chemocline, and in highly transparent Sophia Lake (Cornwallis Island, N.W.T.) this feature extends below the primary chemocline.Where the chemocline is found below depths with adequate illumination, features other than the supersaturated oxygen maximum should be found in deeper water as well, or they should be eliminated from the profiles. Thus, where the chemocline is relatively shallow, the depth of features like the thermal maximum or anoxic strata are related most closely to light penetration, but where chemoclines are deep, as in Lake Tuborg (Ellesmere Island, N.W.T.), the depth of the chemocline determines the depth of the oxycline, thermal maximum, absorption maximum and anoxic stratum.This is the second in a series of papers published in this issue on the Taconite Inlet Lakes Project. These papers were collected by Dr R. S. Bradley. 相似文献
7.
A late Pleistocene and Holocene mineral magnetic record from sediments of Lake Aibi,Dzungarian Basin,NW China 总被引：1，自引：0，他引：1
Alina Tudryn Piotr Tucholka Elisabeth Gibert Francoise Gasse Keiquin Wei 《Journal of Paleolimnology》2010,44(1):109-121
We studied mineral magnetic properties of a 6-m-long, late Pleistocene through Holocene sediment sequence from Lake Aibi in
Dzungaria (Zunggary, Junggar), northern Xinjiang, China. Results were used to infer environmental changes and are compared
with previously studied cores from Lake Manas. Both water bodies occupy the deepest parts of the Dzungarian Basin and are
remnants of large Holocene lakes. During the Late Pleistocene, the magnetic mineralogy in both lakes was dominated by detrital,
iron oxide minerals. Oxic conditions, which dominated during sedimentation and early diagenesis, persisted over the Pleistocene–Holocene
transition. Later, during the middle Holocene, lake bottom conditions enabled authigenic formation of iron sulphide minerals
such as pyrite (FeS2) in Lake Aibi, and pyrite and greigite (Fe3S4) in Lake Manas. This iron sulphide mineralogy suggests increased biological activity in stagnant, anoxic bottom waters. Anoxic
bottom conditions started about 9.8 cal kyr BP in Lake Manas and at about 7.2 cal kyr BP in Lake Aibi. A short dry event recorded
in Lake Manas between 6.8 and 5.2 cal kyr BP is not clearly observed in Lake Aibi. In the late Holocene, i.e. the last 2.8 cal
kyr, sediments of both lakes are again characterised by iron oxides, suggesting well-mixed, shallow water bodies. For this
recent period, it seems that the detrital material in the two lakes had a common origin. Magnetic properties of sediments
in Lakes Aibi and Manas show broadly similar environmental evolution during the late Pleistocene and Holocene. Nevertheless,
despite the close proximity of the two lakes (~200 km) in the same basin, they display some different magnetic properties
and record environmental changes at different times. 相似文献
8.
为探讨全球气候变化背景下多元线性混合模型（IsoSource）和贝叶斯混合模型（MixSIAR）解析宁夏河东沙地柠条锦鸡儿（Caragana korshinskii）水分利用策略差异及适用性,利用氢氧稳定同位素技术,结合直接对比法、IsoSource模型和MixSIAR模型对比分析不同坡度（6°、10°、16°和24°）样地柠条锦鸡儿在生长季不同时期对各潜在水源的利用率,并评估两种模型的植物水分溯源效果。结果表明：柠条锦鸡儿对不同土层深度土壤水的利用存在明显的季节性差异,生长季初期,随着坡度的增大,柠条锦鸡儿对中层土壤水的利用率呈现出先增大后减小的趋势;生长季中期,随坡度增大,柠条锦鸡儿主要水分来源由深层土壤转移至浅层土壤;生长季后期,柠条锦鸡儿主要水分来源随着坡度的增大由浅层土壤转移至深层土壤。基于直接对比法的定性判断结果,IsoSource模型和MixSIAR模型计算坡度6°、10°和16°样地柠条锦鸡儿主要水分来源利用率的适用性均较高;而Mix-SIAR模型计算坡度24°样地柠条锦鸡儿主要的水分来源以及其贡献率具有更高的可靠性。Iso-Source模型更适合解析较小坡度（6°和1... 相似文献
9.
《Polar Science》2014,8(3):232-241
This study analyzes long-term (40–60 years) discharge and water temperature records collected near the basin outlets of the Yukon and Mackenzie Rivers. It defines seasonal cycles of discharge, water temperature (WT), and heat flux (HF) for the basins, and compares their main features to understand their similarity and difference. Both rivers have similar hydrographs, i.e. low flows in winter and high discharge in summer, with the peak flood in June due to snowmelt runoff. Mackenzie River has many large lakes and they sustain the higher base flows over the fall/winter season. Mackenzie basin is large with high precipitation, thus producing 50% more discharge than the Yukon River to the Arctic Ocean. The WT regimes are also similar between the two rivers. Yukon River WT is about 2–3 °C warmer than the Mackenzie over the open water months. Both rivers have the highest WT in the mid summer and they transport large amount of heat to the polar ocean system. Yukon River monthly HF is lower by 10–60% than the Mackenzie mainly due to smaller discharge. Mackenzie River heat transport peaks in July, while the Yukon HF reaches the maximum in June and July. These results provide critical knowledge of river thermal condition and energy transport to the northern seas. They are useful for large-scale climate and ocean model development and validation, and climate/hydrology change research in the northern regions. 相似文献
10.
11.
鲁西北平原冬小麦耗水过程与节水灌溉管理模式讨论 总被引：6，自引：1，他引：6
本文利用禹城综合试验站土壤-植物-大气综合观测场冬小麦田间的小气候梯度仪和大型蒸渗仪的观测资料,结合作者建立的模拟SPAC系统中水、热、CO2通量和光合作用的综合模型,研究了冬小麦全生育期的耗水过程;根据模拟计算的土壤水分动态,对山东省鲁西北平原现行的灌水管理模式进行了讨论。(1)冬小麦全生育期耗水438mm;返青以前耗水占20%,拔节-灌浆期是耗水的旺盛时期,占67%;(2)灌水后地表以下1m处的渗漏量与土层前期储水量和灌水量有关,前期含水量越大,灌水量越大,损失越大,灌水利用率越低;(3)鲁西北平原现行的越冬水-返青水-灌浆水-黄熟水的灌水模式在各次的灌水量控制上应谨慎处理,否则会造成大量的水资源浪费,从而影响灌水利用率。 相似文献
12.
A survey of the modern physical setting of Lake El’gygytgyn, northeastern Siberia, is presented here to facilitate interpretation
of a 250,000-year climate record derived from sediment cores from the lake bottom. The lake lies inside a meteorite impact
crater that is approximately 18 km in diameter, with a total watershed area of 293 km2, 110 km2 of which is lake surface. The only surface water entering the lake comes from the approximately 50 streams draining from
within the crater rim; a numbering system for these inlet streams is adopted to facilitate scientific discussion. We created
a digital elevation model for the watershed and used it to create hypsometries, channel networks, and drainage area statistics
for each of the inlet streams. Many of the streams enter shallow lagoons dammed by gravel berms at the lakeshore; these lagoons
may play a significant role in the thermal and biological dynamics of the lake due to their higher water temperatures (>6°C).
The lake itself is approximately 12 km wide and 175 m deep, with a volume of 14.1 km3. Water temperature within a column of water near the center of this oligotrophic, monomictic lake never exceeded 4°C over
a 2.5 year record, though the shallow shelves (<10 m) surrounding the lake can reach 5°C in summer. Though thermally stratified
in winter, the water appears completely mixed shortly after lake ice breakup in July. Mean annual air temperature measured
about 200 m from the lake was −10.3°C in 2002, and an unshielded rain gage there recorded 70 mm of rain in summer of 2002.
End of winter snow water equivalent on the lake was approximately 110 mm in May 2002. Analysis of NCEP reanalysis air temperatures
(1948–2002) reveals that the 8 warmest years and 10 warmest winters have occurred since 1989, with the number of days below
−30°C dropping from a pre-1989 mean of 35 to near 0 in recent years. The crater region is windy as well as cold, with hourly
wind speeds exceeding 13.4 m s−1 (30 mph) typically at least once each month and 17.8 m s−1 (40 mph) in winter months, with only a few calm days per month; wind may also play an important role in controlling the modern
shape of the lake. Numerous lines of evidence suggest that the physical hydrology and limnology of the lake has changed substantially
over the past 3.6 million years, and some of the implications of these changes on paleoclimate reconstructions are discussed.
This is the second in a series of eleven papers published in this special issue dedicated to initial studies of El'gygytgyn Crater Lake and
its catchment in NE Russia. Julie Brigham-Grette, Martin Melles, Pavel Minyuk were guest editors of this special issue. 相似文献
13.
Miriam Dühnforth Andreas G. N. Bergner Martin H. Trauth 《Journal of Paleolimnology》2006,36(3):281-294
The Nakuru-Elmenteita basin in the Central Kenya Rift, contains two shallow, alkaline lakes, Lake Nakuru (1770 m above sea level) and Lake Elmenteita (1786 m). Ancient shorelines and lake sediments at 1940 m suggest that these two lakes formed a single large and deep lake as a result of a wetter climate during the early Holocene. Here, we used a hydrological model to compare the precipitation–evaporation balance during the early Holocene to today. Assuming that the Nakuru-Elmenteita basin was hydrologically closed, as it is today, the most likely climate scenario includes a 45% increase in mean-annual precipitation, a 0.5°C decrease in air temperature, and an increase of 9% in cloud coverage from the modern values. Compared to the modeling results from other East African lake basins, this dramatic increase in precipitation seems to be unrealistic. Therefore, we propose a significant flow of water from the early Holocene Lake Naivasha in the south towards the Nakuru-Elmenteita basin to compensate the extremely negative hydrological budget of this basin. Since we did not find any field evidence for a surface connection, as often proposed during the last 70 years, the hydrological deficit of the Nakuru-Elmenteita basin could have also been compensated by a subsurface water exchange. 相似文献
14.
本文使用南极长城湾 1 987年 3月至 1 988年 2月连续观测资料 (每小时观测一次 ) ,对该海湾底层海水温度的季节变化特征进行了分析研究 相似文献
15.
Following the Acadian Orogeny, Atlantic Canada accommodated several, large, relatively deep lakes within a wrench-fault basin complex called the Maritime Basin. Late Devonian and Tournaisian lakes were hydrologically open, shallow to deep, mainly fresh water bodies. Middle Visean lakes, here collectively called Loch Macumber, were closed, deep, and meromictic. Their deposits comprise the first and thickest of five sequences in the Maritime Basin. Salinity in the loch increased with time from restricted marine or penesaline, to saline. Basin-centre facies consist of a thin, but extensive, sheet of black, peloidal laminated lime mudstones and an overlying thick evaporite complex. The carbonate sheet grades laterally into both laminated to thinly bedded marlstones, siliciclastic sandstones, and microbial, biocementstone mounds. Laminae consist of alternating carbonate and either silty carbonaceous shale or siliciclastic clay and silt. The mudstone and marlstone are locally interbedded with siliciclastic and carbonate turbidites, resedimented (?deep water) breccias, and olistostromes. Seasonal changes in anoxia and/or carbonate production produced rhythmic laminae of carbonate and carbonaceous shale. Carbonate grains consist of silt-sized microbial clots and rare arthropod carapaces and brachiopod shells. The mounds originated as tufa precipitated around subaqueous hydrothermal springs that supported chemosynthetic communities. Resedimentation processes including incipient brecciation, sliding, slumping, debris flows, and turbidity currents were common. The mounds trapped hydrocarbons from the surrounding laminite and sulphides from underlying hydrothermal vents. Increasing salinity with time resulted in sulphate and chloride precipitation that filled the basins and ended the life of Loch Macumber. After the deposition of thick evaporites the topography became less accentuated, the seas less saline, and the faunas more normal marine. 相似文献
16.
针对不同深度含水层,揭示其富水性,探讨地下水资源可恢复性、可利用性和浅层劣质水改造利用可能性。以国土资源部衡水地下水试验场为依托,在详细调查试验场影响区地下水开发利用状况、监测地下水年动态基础上,开展分层抽水试验和水化学同位素采样。通过对大量抽水水位动态数据过程、局部流场特征和水化学同位素的分析,得出结论:该区农业为影响地下水水位的主控因素;含水层系统承压性、补给强度从下到上分别呈减弱、增强趋势,除浅层外各含水层渗透性较强;各含水层渗流强度及方向不同等。提出实现地下水可持续开发利用建议:对浅层地下咸水适时进行抽咸换淡、混灌轮灌改造利用;170m、300m强含水层作为工农业用水主要开采层,深层地下水主要用于生活用水;按照水量平衡、分质用水原则开发地下水。 相似文献
17.
Elco Luijendijk Marlies ter Voorde Ronald van Balen Hanneke Verweij Erik Simmelink 《Basin Research》2011,23(1):65-82
We performed a detailed analysis of the thermal state of the Cenozoic Roer Valley Graben, the north–western branch of the European Cenozoic Rift System, based on a new set of temperature data. We developed a numerical technique for correcting bottom hole temperatures, including an evaluation of the uncertainty of thermal parameters. Comparison with drill stem test temperatures indicated that the uncertainty in corrected bottom hole temperatures using a two‐component numerical model is approximately ± 4 °C, which is much more accurate than the up to 15 °C errors encountered in often‐used line‐source or Horner correction methods. The subsurface temperatures and the derived regional heat flow estimates of 53 ± 6 to 63 ± 6 mW m?2 show no significant difference between the central rift and the adjacent structural highs. The absence of an elevated heat flow is attributed to the low amount of lithospheric thinning during the Cenozoic rifting phase (β=1.06–1.15). A local thermal anomaly exceeding +10 °C was found in five wells in the north–western part of the rift basin at depths of 1000–1500 m, and is most likely caused by the upward flow of fluids along faults, whereas lower temperatures in the upper 1500 m in the southern part of the rift basin could indicate cooling by topography‐driven groundwater flow. Conflicting ideas exist on the active or passive rifting mechanisms responsible for the formation of the different rift basins of European Cenozoic Rift System. The low spatial variation in heat flow found in this study suggests that the mechanism responsible for forming the Roer Valley Graben is passive rifting. 相似文献
18.
松嫩平原盐沼湿地冻融期水盐动态研究--吉林省长岭县十三泡地区湖滩地为例 总被引：12，自引：0，他引：12
以吉林省长岭县十三泡地区湖滩地为例 ,选取有代表性的月份进行定位观测、实验和对比分析 ,研究了冻融期盐沼湿地水盐运移的特殊规律性。研究表明 ,盐沼湿地冻结期 ,由于冻层的存在 ,土体内产生的温度梯度、水势梯度 ,是冬季水盐积累的驱动力。在冻结期 ,冻层水盐自底层向上迁移 ;融冻期 ,冻层自地表向下及自暖土层向上双向融化 ,在冻层形成上层滞水 ,在冻层之下水盐从下向冻层迁移冻结。冻融期间盐沼湿地水盐迁移的热力学机制是松嫩平原土壤盐化发生机制的重要组成部分。 相似文献
19.
Mid-Palaeocene palaeogeography of the eastern North Sea basin: integrating geological evidence and 3D geodynamic modelling 总被引：1，自引：0，他引：1
The Mid‐Palaeocene palaeogeography of Denmark and the surrounding areas have been reconstructed on the basis of published geological data integrated with 3D geodynamic modelling. The use of numerical modelling enables quantitative testing of scenarios based on geological input alone and thus helps constrain likely palaeo‐water depths in areas where the geological data are inconclusive or incomplete. The interpretation of large‐scale erosional valleys and small‐scale circular depressions at the Mid‐Palaeocene Top Chalk surface in the Norwegian–Danish basin as either submarine or subaerial features is enigmatic and has strong implications for palaeogeographical reconstructions of the eastern North Sea basin. A 3D thermo‐mechanical model is employed in order to constrain the likely palaeo‐water depths of the eastern North Sea basin during the Palaeocene. The model treats the lithosphere as an elasto‐visco‐plastic continuum and models the lithospheric response to the regional stress field and thermal structure. The model includes the effects of sea‐level change, sedimentation and erosion, from the Mid Cretaceous to the present. Modelling results reproduce to first order geological data such as present sediment isopachs and palaeo‐water depths. It is concluded that the Mid Palaeocene water depths in the Norwegian–Danish basin were about 250 m. The erosional valleys and circular depressions at the top of the Upper Cretaceous‐Danian Chalk Group are thus interpreted to have formed in relatively deep water rather than due to subaerial exposure. Likely interpretations of the structures are therefore submarine valleys and pockmarks. 相似文献