首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 62 毫秒
1.
Ambae (also known as Aoba), is a 38 × 16 km2 lozenge-shaped island volcano with a coastal population of around 10 000. At the summit of the volcano is lake Voui — one of the largest active crater lakes worldwide, with 40 × 106 m3 of acidic water perched 1400 m a.s.l. After more than 300 years of dormancy, Ambae volcano reawakened with phreatic eruptions through Voui in 1995, and culminating in a series of surtseyan eruptions in 2005, followed by a rapid and spectacular colour change of the lake from light blue to red in 2006. Integrating lake water chemistry with new measurements of SO2 emissions from the volcano during the 2005–2006 eruptive period helps to explain the unusual and spectacular volcanic activity of Ambae — initially, a degassed magma approached the lake bed and triggered the surtseyan eruption. Depressurization of the conduit facilitated ascent of volatile-rich magma from the deeper plumbing system. The construction of a cone during eruption and the high degassing destabilised the equilibrium of lake stratification leading to a limnic event and subsequently the spectacular colour change.  相似文献   

2.
Our investigation on macrophytes in Lake Qattieneh, a large, shallow reservoir in western Syria, is a first assessment of ecological status of this lake. We studied spatial distribution patterns of aquatic macrophyte vegetation and heavy metal concentrations to determine if they can be used as indicators of point sources of pollution. Industrial and municipal point sources at the lake shore increase nutrient load and contamination by heavy metals. Water analyses revealed high concentrations of some heavy metals at some littoral sites: Ni 88.7 μg L−1, Cr 49.99 μg L−1, Co 14.38 μg L−1, and Cu 11.65 μg L−1. Despite hypertrophic conditions and high heavy metal contamination, we recorded several submerged macrophyte species with heterogeneous spatial distribution patterns. Whereas Potamogeton pectinatus L. dominates in the eastern part of the lake, near industrial point sources, both Myriophyllum spicatum L. and Potamogeton lucens L. form extended patches in the western part of the lake. The shallow, littoral areas near villages are dominated by Ranunculus trichophyllus Chaix in Villars and Ceratophyllum demersum L. The west-east gradient in nutrient and heavy metal concentrations in waters and sediments are reflected by the spatial distribution of submersed species. While the heavy metal concentrations of the water body vary considerably in different seasons, the contents in submersed macrophytes integrate seasonal variations of longer time periods. Spatial distribution and tissue accumulation of littoral macrophyte species reflect the environmental conditions at respective sites such as heavy metal contents in water and sediment.  相似文献   

3.
Water resources development and exploitation are critical for a viable and sustainable modern human society. Unfortunately, however, there is a considerable water storage depletion and environmental degradation in especially (semi)‐arid river basins due to the forces of population growth, urbanization, industrialization and intensive agricultural irrigation. Addressing water storage depletion is not only a question of research, but is very much a question of developing appropriate countermeasures to preserve valuable/fragile ecological systems. As one such effort, this study analyzes the hydrology and storage in Baiyangdian Lake as affected by water resources development and exploitation in the Baiyangdian Lake Catchment of Northern China. Three models, WetSpass (Water and Energy Transfer between Soil, Plants and the Atmosphere under quasi‐Steady State), WATBUD (Water Budget) and MODFLOW (USGS three‐dimensional finite‐difference groundwater flow model) were used in combination to simulate the hydrogeologic conditions in the lake catchment for 1956–2008. The model‐calibrated values are in good agreement with the measured values, with R2 > 0·8 and RMSE < 10% of measured values. Runoff, the primary source of water for the lake storage, has steadily declined due mainly to multiple dam construction and reservoir impoundments in the headwater valleys and rivers in the catchment. In addition to dwindling runoff, groundwater levels have declined considerably due to over‐abstraction, mainly for agricultural irrigation. Additionally, evaporation or evapotranspiration is increasing in the lake catchment due to rising temperatures. The worsening hydrological conditions, amid the harsh semi‐arid climate, have resulted in considerable depletion of the storage and hydrology of Baiyangdian Lake. Sustainable countermeasures like agricultural water‐saving and infusion of external water (e.g., via by the South–North Water Transfer Project) could be a viable option for preserving not only the hydrology of the lake catchment, but also storage in Baiyangdian Lake. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

4.
In China, the increase in exogenous-source pollutants from rivers is one of the most important causes of lake eutrophication. The application of remote sensing technology to water quality monitoring of rivers connected to these lakes has special significance for lake management at regional scales. Many research studies have estimated water clarity using Landsat imagery. However, most of this work focused on lakes or reservoirs, for which abundant water-only pixels (i.e., pure pixels of water, PPW) were available. Few of these studies have addressed rivers, especially rivers with an average width less than 100 m. In our study, we sought to determine whether water clarity in the rivers connected to Taihu Lake could be estimated using Landsat imagery. We obtained 18 Enhanced Thematic Mapper Plus (ETM+) images from 2009 for 13 rivers ranging from an average of 37.3 to 173.6 m wide. Three field campaigns conducted in May 2009, September 2009, and January 2010 were used to obtain field measurements of Secchi disk depth (SDD). Our results suggested that the widely used model, a(TM1/TM3) + b(TM1) + c, was suitable for the estimation of SDD for Taihu Lake. The brightness of the panchromatic band of ETM+ showed significant correlations with TM1, TM3 and TM1/TM3 (p < 0.001). As a result, SDD in the lake could also be estimated using the Landsat panchromatic band. The multispectral image of ETM+ did not provide adequate PPW for estimation of water clarity in rivers. However, PPW derived from the panchromatic image captured about 93% of the variation in SDD, on average, for the every worst-case scenario in the 13 rivers. Using the PPW in rivers, a significant correlation was found between the brightness of the panchromatic image and SDD (R2 = 0.64, p < 0.001). Our results demonstrate that the panchromatic image of Landsat, but not the multispectral image, can be used to estimate water clarity in rivers with an average width greater than 40 m in the Taihu basin.  相似文献   

5.
Monitoring the water balance of Lake Victoria, East Africa, from space   总被引：3，自引：0，他引：3  
Sean Swenson  John Wahr   《Journal of Hydrology》2009,370(1-4):163-176
Using satellite gravimetric and altimetric data, we examine trends in water storage and lake levels of multiple lakes in the Great Rift Valley region of East Africa for the years 2003–2008. GRACE total water storage estimates reveal that water storage declined in much of East Africa, by as much as , while altimetric data show that lake levels in some large lakes dropped by as much as 1–2 m. The largest declines occurred in Lake Victoria, the Earth’s second largest freshwater body. Because the discharge from the outlet of Lake Victoria is used to generate hydroelectric power, the role of human management in the lake’s decline has been questioned. By comparing catchment water storage trends to lake level trends, we confirm that climatic forcing explains only about 50decline. This analysis provides an independent means of assessing the relative impacts of climate and human management on the water balance of Lake Victoria that does not depend on observations of dam discharge, which may not be publically available. In the second part of the study, the individual components of the lake water balance are estimated. Satellite estimates of changes in lake level, precipitation, and evaporation are used with observed lake discharge to develop a parameterization for estimating subsurface inflows due to changes in groundwater storage estimated from satellite gravimetry. At seasonal timescales, this approach provides closure to Lake Victoria’s water balance to within . The third part of this study uses the water balance of a downstream water body, Lake Kyoga, to estimate the outflow from Lake Victoria remotely. Because Lake Kyoga is roughly 20 times smaller in area than Lake Victoria, its water balance is strongly influenced by inflow from Lake Victoria. Lake Kyoga has been shown to act as a linear reservoir, where its outflow is proportional to the height of the lake. This model can be used with satellite altimetric lake levels to estimate a time series of Lake Victoria discharge with an rms error of about .  相似文献   

6.
Hydrologic regime plays an important role in maintaining aquatic ecosystem structures and biogeochemical processes of endorheic salt lakes. Due to joint influences of regional climate change, runoff regulation and water withdrawal, ecological water deficiency has been increasingly prominent in endorheic salt lakes in Northwest China, especially in the Inner Mongolian Plateau. Previous studies mainly focused on establishing and applying methods to determine ecological water levels of lakes, while much less attention was paid to a more important problem – how such water levels could be reached under changed watershed hydrological processes. Solutions of this gap were explored in this study using the Dalinuoer Lake as an example. This lake is a typical endorheic salt lake located in the Inner Mongolian Plateau. It is a critical source to provide important ecological services and economic values for locals. Its ecological water level to maintain the optimum salinity threshold was first calculated by applying a statistical analysis of relationships between the phytoplankton biomass, salinity and water level of the lake. Potential measures to preserve the ecological water level of the lake were subsequently evaluated based on a hydrological process analysis of the watershed. The results indicated that the optimum salinity threshold was 5.7 g/L. This value should be also valid for other endorheic salt lakes in this region. According to a function between the water storage and the mean water depth of this lake, the ecological water level was determined to be 10.28 m with an ecological water deficit of 2.5 × 108 m3. A basin water balance analysis using the results proposed measures to maintain a sustainable ecological water level, including controlling local water consumption and infusing ecological water. The results of this study could be extrapolated to other similar conditions to provide guidance for policy-makers, so that better decisions could be hopefully forged to protect eco-hydrological processes of endorheic salt lakes in the Mongolian Plateau, as well as other comparable scenarios.  相似文献   

7.
This paper presents 19 months of stable isotope (δ2H and δ18O) data to enhance understanding of water and solute transport at two spatial scales (2.3 km2 and 122 km2) in the agricultural Lunan catchment, Scotland. Daily precipitation and stream isotope data, weekly lake and spring isotope data and monthly groundwater isotope data revealed important insights into flow pathways and mixing of water at both scales. In particular, a deeper groundwater flow path significantly contributes to total streamflow (25-50%). Upstream lake isotope dynamics, susceptible to evaporative fractionation, also appeared to have an important influence on the downstream isotope composition. This unique tracer data set facilitated the conceptualization of a lumped catchment-scale flow-tracer model. The incorporation of hydrological, mixing and fractionation processes based on these data improved simulations of the stream δ2H isotope response at the catchment outlet from 0.37 to 0.56 for the Nash-Sutcliffe statistic. The stable isotope data successfully aided model conceptualization and calibration in the quest for a simple water and solute transport model with improved representation of process dynamics.  相似文献   

8.
After the phreatic eruption in 1982–83, volcanic activities at Kusatsu–Shirane volcano had been decreasing and reached a minimum in 1990, had turned to a temporal rise in activity up to 1994 and then decreased again at least up to 1997. During this low-activity period we observed a relatively short (≤ 1 y) cyclic variation in polythionates (PT) in the Yugama lake water. Spectral power density analysis of the PT time-series by an autoregressive (maximum entropy spectral estimation, MESE) method indicates that the major frequency in the PT variations is 1.0 y− 1 and the minor is 2–3 y− 1 (1.0 and 0.3–0.5 y in periodicity, respectively). Annual variations in the lake temperature are ruled out for explaining these periodicities. We attribute these cyclic variations to a cyclic magnification-reduction in meteoric-water injection into a hydrothermal regime where volcanic gases from cooling magma bodies at depth and cooler oxidized groundwater come into contact with each other. This interaction may result in a periodical change in the composition and flux of SO2 and H2S gases being discharged into the lake and forming PT. From a phase deviation (2–3 months) in the cycles between the annual precipitation, including snowmelt, and the PT time-series, we estimated the maximal depth of a hydrothermal reservoir beneath the lake assuming a vertical hydraulic conductivity (5 × 10− 3 cm/s) of the volcanic detritus around the summit hydrothermal system. Chloride in the lake water reached a maximum 1.5 years faster than PT. This is most likely due to a gradual elevation of the potentiometric front of a concentrated sublimnic solution in the hydrothermal reservoir. Variations of dissolved SO2 and H2S in the lake water were not consistent with those of the fumarolic gases on the north flank of the volcano. This fact together with additional observations strongly suggests that these fumaroles may have the same origin but are chemically modified by a subsurface aquifer. The PT monitoring at active crater lakes during a quiescent period can provide insight into the annual expansions and reductions of a volcano-hosted hydrothermal reservoir.  相似文献   

9.
The ‘Chicken Creek’ artificial catchment area, Welzow-South, E Germany, created to study processes and structures of initial ecosystem development, discharges into a small experimental lake (A=3805 m2, V=3992 m3, zmax=2.4 m). This lake was man-made in 2005 and filled by natural surface runoff until January 2006. In summer 2006 and 2008, the actual development of sediments and the evolution of the phosphorus (P) cycle were studied. 19.7% of the original lake volume was filled by sediment within the first 3 years. A fine-grained sediment representing silt (6.3-63 μm) accumulated at high accretion rates at the deepest point (200 mm a−1, 0-24 mm week−1) due to massive erosion in the catchment. The sediment is low in organic matter (2.5-5.2%) and total P (TP, 0.31-0.97 mg g−1). Low amounts of P associated with degradable organic matter and surplus of metal hydroxides (Fe:P∼40, Al:P∼20) favor an efficient P binding and low dissolved P concentrations in pore water (1-107 μg l−1). Hence, the mineral sediment quality and the low rates of P release (0.06 mg m−2 d−1) revealed that a lake at an initial stage of development has essentially no sedimentary P cycle compared to eutrophic shallow lakes. However, the increasing emersed and submersed macrophyte growth will control further lake succession by intensifying the internal nutrient cycling. The macrophytes drive the evolution of a sedimentary P cycle by mobilizing and translocating P, by accumulating carbon and thus by stimulating microbial and redox processes.  相似文献   

10.
卞宇峥  薛滨  张风菊 《湖泊科学》2021,33(6):1844-1856
洪泽湖是淮河水系中最重要的湖泊之一,是我国的第四大淡水湖,它在防洪、灌溉、航运、跨流域调水以及水资源与水环境保护等方面发挥着重要作用.过去300年来,由于黄淮关系的演变和人类活动的影响,洪泽湖水域面积发生剧烈变化.研究湖泊水域空间变化有助于认识流域环境变化与人类活动影响.本文利用18世纪初以来的古地图、历史文献资料及1981-2016年期间的7期遥感影像数据,采用遥感和地理信息系统技术相结合的方法,分析了近300年来洪泽湖水域时空演变过程及其原因.研究结果表明：过去300年来,洪泽湖面积总体呈减少趋势,年际缩减速率为0.17%,且湖域范围总体表现为由四周向中心缩小的趋势,其中西南湖域的形态变化最为显著.具体而言,清中期以前,黄河多次夺泗入淮,洪泽湖面积变化受黄淮关系、高家堰等水利枢纽的修建以及降水等因素影响.至清末,洪泽湖面积由3078.78 km2下降至2335.73 km2,共减少743.05 km2,其空间形态也发生了剧烈变化,该时期黄河改道、降水以及人口增长导致的湖滨围垦是影响洪泽湖演变的主要原因.建国以来（1949-2016年）,洪泽湖面积进一步缩小,由1757.60 km2下降至1488.43 km2,共减少了269.17 km2,其中1995-2000年间湖泊面积下降最为显著,共减少了281.43 km2,湖泊动态变化度达到2.78%,该时期自然因素对湖泊水域面积的影响减弱,而人口增长、围垦及水利工程的修建等人类活动逐渐成为影响洪泽湖演化的主导因素.  相似文献   

11.
The effects of climate change have a substantial influence on the extremely vulnerable hydrologic environment of the Tibetan Plateau. The estimation of alpine inland lake water storage variations is essential to modeling the alpine hydrologic process and evaluating water resources. Due to a lack of historical hydrologic observations in this remote and inaccessible region, such estimations also fill a gap in studies on the continuous inter‐annual and seasonal changes in the inland lake water budget. Using Lake Siling Co as a case study, we derived a time‐series of lake surface extents from MODIS imagery, and scarce lake water level data from the satellite altimetry of two sensors (ICESat/GLAS and ENVISAT RA‐2) between 2001 and 2011. Then, based on the fact that the rise in lake water levels is tightly dependent on the expansion of the lake extent, we established an empirical model to simulate a continuous lake water level dataset corresponding to the lake area data during the lake's unfreezing period. Consequently, from three dimensions, the lake surface area, water level and water storage variations consistently revealed that Lake Siling Co exhibited a dramatic trend to expand, particularly from 2001 to 2006. Based on the statistical model and lake area measurements from Landsat images since 1972, the extrapolated lake water level and water storage indicate that the lake has maintained a continual expansion process and that the cumulative water storage variations during 1999–2011 account for 66.84% of the total lake water budget (26.87 km3) from 1972 to 2011. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

12.
The level of Lake Tana, Ethiopia, fluctuates annually and seasonally following the patterns of changes in precipitation. In this study, a mass balance approach is used to estimate the hydrological balance of the lake. Water influx from four major rivers, subsurface inflow from the floodplains, precipitation, outflow from the lake constituting river discharge and evapotranspiration from the lake are analysed on monthly and annual bases. Spatial interpolation of precipitation using rain gauge data was conducted using kriging. Outflow from the lake was identified as the evaporation from the lake's surface as well as discharge at the outlet where the Blue Nile commences. Groundwater inflow is estimated using MODular three‐dimensional finite‐difference ground‐water FLOW model software that showed an aligned flow pattern to the river channels. The groundwater outflow is considered negligible based on the secondary sources that confirmed the absence of lake water geochemical mixing outside of the basin. Evaporation is estimated using Penman's, Meyer's and Thornwaite's methods to compare the mass balance and energy balance approaches. Meteorological data, satellite images and temperature perturbation simulations from Global Historical Climate Network of National Oceanographic and Atmospheric Administration are employed for estimation of evaporation input parameters. The difference of the inflow and outflow was taken as storage in depth and compared with the measured water level fluctuations. The study has shown that the monthly and annually calculated lake level replicates the observed values with root mean square error value of 0·17 and 0·15 m, respectively. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

13.
We have numerically modeled evolving fluid pressures and concentrations from a nine-year in situ osmosis experiment in the Pierre Shale, South Dakota. These data were obtained and recently interpreted by one of us (C.E.N.) as indicating a potentially significant role for chemical osmosis in media like the Pierre Shale. That analysis considered only the final pressure differentials among boreholes that were assumed to represent osmotic equilibrium. For this study, the system evolution was modeled using a recently developed transient model for membrane transport. The model simulates hydraulically and chemically driven fluid and solute transport. The results yield an estimate of the thickness of the water film between the clay platelets b of 40 Å, which corresponds to an osmotic efficiency σ of 0.21 for the ambient pore water salinity of 3.5 g/l TDS. These values largely confirm the results of the earlier equilibrium analysis. However, the new model analysis provides additional constraints suggesting that intrinsic permeability k = 1.4 × 10−19 m2, specific storage Ss = 1.7 × 10−5 m−1, and diffusion coefficient D* = 6 × 10−11 m2/s. The k value is larger than certain independent estimates which range from 10−21 to 10−20; it may indicate opening of microcracks during the experiments. The fact that the complex transient pressure and concentration behavior for the individual wells could be reproduced quite accurately, and the inferred parameter values appear to be realistic for the Pierre Shale, suggests that the new model is a useful tool for modeling transient coupled flows in groundwater systems.  相似文献   

14.
Perturbations of the lake water balance, inputs of heavy metals to lakes, and intensifying fertilization of lakes through input and accumulation of phosphorus—these three classes of phenomena are among the more important background processes in lake restoration. Lake restoration consists of a series of measures animed at producing a homeostatic response of a lake system to external perturbations. The success of its implementation is affected by the morphometric and edaphic parameters of different types of lakes. The relationship between the volume (V) and mean-depth of fresh-water lakes indicates a trend of . Glacial lakes occuring on or near crystalline shields have relatively shallow depths, whereas volcanic lakes, rift valley and deep valley lakes have relatively greater depths for the same volume. For saline lakes (21 lakes, V>1 km3) that undergo cycles of expansion and shrinkage, the V to relationship is closer to power 1. Water residence times (τ) of small and big fresh-water lakes show a trend of τ approximately linear in or τ∝V0.3. Volcanic lakes and Maare have longer residence times in comparison to other lakes of similar volumes. For the major inorganic chemical species and heavy metals, the regulatory upper-limit concentrations in drinking water in the USA and EEC are from several times to more than 100 times higher than their concentrations in a global mean river water. Only three elements (Fe, P, and Al) occur in river water at concentrations approaching such upper-limit recommendations. Rates of accumulation of phosphorus in lake water and sediments, computed as the difference between input and ouflow removal rates for 23 fresh-water lakes, are generally lower for lakes of longer water residence time. The rate of accumulation is a measure of homeostatic response of the lake system to input load: it is equivalent to the rate of all the removal processes needed to maintain phosphorus concentration in lake water at a steady state.  相似文献   

15.
El Chichón crater lake appeared immediately after the 1982 catastrophic eruption in a newly formed, 1-km wide, explosive crater. During the first 2 years after the eruption the lake transformed from hot and ultra-acidic caused by dissolution of magmatic gases, to a warm and less acidic lake due to a rapid “magmatic-to-hydrothermal transition” — input of hydrothermal fluids and oxidation of H2S to sulfate. Chemical composition of the lake water and other thermal fluids discharging in the crater, stable isotope composition (δD and δ18O) of lake water, gas condensates and thermal waters collected in 1995–2006 were used for the mass-balance calculations (Cl, SO4 and isotopic composition) of the thermal flux from the crater floor. The calculated fluxes of thermal fluid by different mass-balance approaches become of the same order of magnitude as those derived from the energy-budget model if values of 1.9 and 2 mmol/mol are taken for the catchment coefficient and the average H2S concentration in the hydrothermal vapors, respectively. The total heat power from the crater is estimated to be between 35 and 60 MW and the CO2 flux is not higher than 150 t/day or ~ 200 gm− 2 day− 1.  相似文献   

16.
Strontium (Sr) concentrations and isotopic ratios have been measured in a series of water and rock samples from most of the major tributaries of the Lake Qinghai basin on the north‐eastern Tibetan Plateau. Dissolved Sr and 87Sr/86Sr show ranges of 488–12 240 nmol/l and 0·710497–0·716977, respectively. These data, together with measurements of major cations and anions in rivers and their tributaries and various lithologies of the catchment, were used to determine the contributions of Sr and its isotopic expense to rivers and lakes. Our results demonstrate that the chemical components and 87Sr/86Sr ratios of the alkaline waters are derived from mixing of carbonate and silicate sources, with the former contributing 72 ± 18% dissolved Sr to rivers. The difference in tributary compositions stems from the lithology of different river systems and low weathering intensity under a semi‐arid condition. Variation in 87Sr/86Sr ratios places constraint on the Sr‐isotopic compositions of the main tributaries surrounding Lake Qinghai. The water chemistry of the Buha River, the largest river within the catchment underlain by the late Paleozoic marine limestone and sandstones, dominates Sr isotopic composition of the lake water, being buffered by the waters from the other rivers and probably by groundwater. However, the characteristic chemical composition of the lake itself differs remarkably from the rivers, which can be attributed to precipitation of authigenic carbonates (low‐magnesium calcite, aragonite, and dolomite), though this does not impact the Sr isotope signature, which may remain a faithful indicator in paleo‐records. Regarding the potential role of groundwater input within the Lake Qinghai systems in the water budget and water chemistry, we have also determined the Sr concentration and 87Sr/S6Sr ratio of groundwater from diverse environments. This has allowed us to further constrain the Sr isotope systematic of this source. A steady‐state calculation gives an estimate for the groundwater flux of 0·19 ± 0·03 × 108 m3/yr, accounting for about 8% of contemporary lake Sr budget. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

17.
It has been shown that due to the small surface of crater lakes, temperature surveillance is a problem using meteorological satellites. This is particularly true for El Chichón surface lake because it's about one tenth of an AVHRR pixel at nadir. In order to guarantee at least one unmixed pixel in AVHRR data, it is necessary to use only AVHRR data from NOAA satellite passes as close as possible to the nadir for the period 1996–2006, therefore AVHRR data of El Chichón's crater lake were only used it they were cloudless and had scan angles close to nadir. The analysis of the time series data shows that lake surface temperature had annual maximum values (> 35 °C) during 1996 and 1997 then surface temperature decay with a negative exponential trend reaching a steady state of about 30 °C in the last years (2004–2006). A seasonal temperature variation between the dry (December to May) and the wet (June to November) seasons is also observed. Differences between nocturnal and midday temperatures indicate the influence of lake energy emission (including reflectance) at midday under a strong short-wave solar radiation. Water surface radiative flux under these conditions reaches an average of 77.8 W m− 2 and a maximum of 187.1 W m− 2. Whereas nocturnal heat output from El Chichón crater lake has an average surface radiative flux of 20.4 W m− 2 and a maximum of 74.3 W m− 2.  相似文献   

18.
苏州金鸡湖水环境治理工程的环境经济分析   总被引：1，自引：0，他引：1  
逄勇  丁玲  陈燕羽 《湖泊科学》2002,14(3):253-258
对苏州金鸡湖水环境综合治理的环境效益和经济费用进行了综合分析，得出：工程建成运行后的金鸡湖及周边河道的水质基本可达国家地面水Ⅲ类水标准。金湖鸡水环境治理工程建成运行后费用约为0.92元/m^3-1.62元/m^3之间，若考虑金鸡湖水环境改善后地价的价值、旅游收入的增加，金鸡湖水环境治理的经济费用还会降低。总体来看，该项工程环境及社会效益比较明显，经济费用也在比较合理的范围内。  相似文献   

19.
Mount Erebus, a large intraplate stratovolcano dominating Ross Island, Antarctica, hosts the world's only active phonolite lava lakes. The main manifestation of activity at Erebus volcano in December 2004 was as the presence of two convecting lava lakes within an inner crater. The long-lived Ray Lake, ~ 1400 m2 in area, was the site of up to 10 small Strombolian eruptions per day. A new but short-lived, ~ 1000–1200 m2 lake formed at Werner vent in December 2004 sourced by lava flowing from a crater formed in 1993 by a phreatic eruption. We measured the radiative heat flux from the two lakes in December 2004 using a compact infrared (IR) imaging camera. Daily thermal IR surveys from the Main Crater rim provide images of the lava lake surface temperatures and identify sites of upwelling and downwelling. The radiative heat outputs calculated for the Ray and Werner Lakes are 30–35 MW and 20 MW, respectively. We estimate that the magma flux needed to sustain the combined heat loss is ~ 250–710 kg s− 1, that the minimum volume of the magma reservoir is 2 km3, and that the radius of the conduit feeding the Ray lake is ~ 2 m.  相似文献   

20.
We present the results of a 3‐year monitoring programme of the stable isotope composition of lake water and precipitation at Taozi Lake, in the East Asian monsoon region of China. Our aims were to reveal the spatiotemporal pattern of variation of stable isotopes in a small closed‐basin lake and to quantitatively determine the impacts of precipitation and evaporation on the stable isotope composition of lake water under a humid monsoon climate. In the time domain, the stable oxygen isotopic ratio of the lake water (δ18OL) exhibited substantial seasonal and interannual variations, but the isotope variations between different precipitation events substantially exceeded seasonal and interannual variations. Compared with the stable isotopes in precipitation, δ18OL was substantially positive and dL was negative. In the space domains, the lake water was homogeneously mixed. Indicated by statistic analyses, precipitation plays a dominant role in dynamic of the lake stable isotope during precipitation events of relatively large magnitude, whereas the effect of evaporation is dominant during smaller precipitation events. Results advance our understanding of the stable isotope change rule in the process of lake water evaporation, and it is helpful to identify the climatic significance recorded in stable isotopic compositions of lake bottom sediments.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号