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851.
Phytoplankton Biomass and Production in Subtropical Hong Kong Waters: Influence of the Pearl River Outflow 总被引:1,自引:0,他引:1
Alvin Y. T. Ho Jie Xu Kedong Yin Yuelu Jiang Xiangcheng Yuan Lei He Donald M. Anderson Joseph H. W. Lee Paul J. Harrison 《Estuaries and Coasts》2010,33(1):170-181
The size-fractionated phytoplankton biomass and primary production were investigated in four contrasting areas of Hong Kong
waters in 2006. Phytoplankton biomass and production varied seasonally in response to the influence of the Pearl River discharge.
In the dry season, the phytoplankton biomass and production were low (<42 mg chl m−2 and <1.8 g C m−2 day−1) in all four areas, due to low temperatures and dilution and reduced light availability due to strong vertical mixing. In
contrast, in the wet season, in the river-impacted western areas, the phytoplankton biomass and production increased greater
than five-fold compared to the dry season, especially in summer. In summer, algal biomass was 15-fold higher than in winter,
and the mean integrated primary productivity (IPP) was 9 g C m−2 day−1 in southern waters due to strong stratification, high temperatures, light availability, and nutrient input from the Pearl
River estuary. However, in the highly flushed western waters, chl a and IPP were lower (<30 mg m−2 and 4 g C m−2 day−1, respectively) due to dilution. The maximal algal biomass and primary production occurred in southern waters with strong
stratification and less flushing. Spring blooms (>10 μg chl a L−1) rarely occurred despite the high chl-specific photosynthetic rate (mostly >10 μg C μg chl a
−1 day−1) as the accumulation of algal biomass was restricted by active physical processes (e.g., strong vertical mixing and freshwater
dilution). Phytoplankton biomass and production were mostly dominated by the >5-μm size fraction all year except in eastern
waters during spring and mostly composed of fast-growing chain-forming diatoms. In the stratified southern waters in summer,
the largest algal blooms occurred in part due to high nutrient inputs from the Pearl River estuary. 相似文献
852.
Regional landslide susceptibility analysis using back-propagation neural network model at Cameron Highland,Malaysia 总被引:20,自引:6,他引:14
This paper presents landslide susceptibility analysis around the Cameron Highlands area, Malaysia using a geographic information
system (GIS) and remote sensing techniques. Landslide locations were identified in the study area from interpretation of aerial
photographs and field surveys. Topographical, geological data and satellite images were collected, processed, and constructed
into a spatial database using GIS and image processing. Ten landslide occurrence factors were selected as: topographic slope,
topographic aspect, topographic curvature and distance from drainage, lithology and distance from lineament, soil type, rainfall,
land cover from SPOT 5 satellite images, and the vegetation index value from SPOT 5 satellite image. These factors were analyzed
using an advanced artificial neural network model to generate the landslide susceptibility map. Each factor’s weight was determined
by the back-propagation training method. Then, the landslide susceptibility indices were calculated using the trained back-propagation
weights, and finally, the landslide susceptibility map was generated using GIS tools. The results of the neural network model
suggest that the effect of topographic slope has the highest weight value (0.205) which has more than two times among the
other factors, followed by the distance from drainage (0.141) and then lithology (0.117). Landslide locations were used to
validate the results of the landslide susceptibility map, and the verification results showed 83% accuracy. The validation
results showed sufficient agreement between the computed susceptibility map and the existing data on landslide areas. 相似文献
853.
Alternative water resources in granitic rock: a case study from Kinmen Island,Taiwan 总被引:1,自引:1,他引:0
Tai-Sheng Liou Yuan-Hsi Lee Li-Wei Chiang Wayne Lin Tai-Rong Guo Wen-Shan Chen Jeng-Ming Chien 《Environmental Earth Sciences》2010,59(5):1033-1046
Kinmen Island is a small, tectonically stable, granitic island that has been suffering from a scarcity of fresh water resources
due to excessive annual evapotranspiration over annual precipitation. Recent studies further indicate that shallow (0–70 m)
sedimentary aquifers, the major sources of groundwater supply, have already been over-exploited. Therefore, this preliminary
study is to investigate the existence of exploitable water resources that can balance the shortage of fresh water on this
island. Site characterization data are obtained from island-wide geophysical surveys as well as small-scale tests performed
in a study area formed by three deep (maximum depth to 560 m) vertical boreholes installed in mid-east Kinmen northeast to
Taiwu Mountain. Vertical fracture frequency data indicate that the rock body is fractured with a spatially correlated pattern,
from which three major fracture zones (depths 0–70, 330–360, and below 450 m) can be identified. Geologic investigations indicate
that the deepest fracture zone is caused by the large-scale, steeply dipping Taiwushan fault. This fault may have caused a
laterally extensive low-resistivity zone, a potential fractured aquifer, near Taiwu Mountain. The middle fracture zone is
induced by the Taiwushan fault and intersects the fault approximately 21 m southeast of the study area below a depth of 350 m.
Slug testing results yield fracture transmissivity varying from 4.8 × 10−7 to 2.2 × 10−4 m2/s. Cross-hole tests have confirmed that hydraulic connectivity of the deeper rock body is controlled by the Taiwushan fault
and the middle fracture zone. This connectivity may extend vertically to the sedimentary aquifers through high-angle joint
sets. Despite the presence of a flow barrier formed by doleritic dike at about 300 m depth, the existence of fresh as well
as meteoric water in the deeper rock body manifests that certain flow paths must exist through which the deeper fractured
aquifers can be connected to the upper rock body. Therefore, groundwater stored within the Taiwushan fault and the associated
low-resistivity zone can be considered as additional fresh water resources for future exploitation. 相似文献
854.
Curtis M. Oldenburg Jennifer L. Lewicki Lehua Pan Laura Dobeck Lee Spangler 《Environmental Earth Sciences》2010,60(2):241-250
A numerical experiment was carried out to test whether the patchy CO2 emission patterns observed at the Zero Emissions Research and Technology release facility are caused by the presence of packers
that divide the horizontal injection well into six CO2-injection zones. A three-dimensional model of the horizontal well and cobble–soil system was developed and simulations using
TOUGH2/EOS7CA were carried out. Simulation results show patchy emissions for the seven-packer (six-injection-zone) configuration
of the field test. Numerical experiments were then conducted for the cases of 24 packers (23 injection zones) and an effectively
infinite number of packers. The time to surface breakthrough and the number of patches increased as the number of packers
increased suggesting that packers and associated along-pipe flow are the origin of the patchy emissions. In addition, it was
observed that early breakthrough occurs at locations where the horizontal well pipe is shallow and installed mostly in soil
rather than the deeper cobble. In the cases where the pipe is installed at shallow depths and directly in the soil, higher
pipe gas saturations occur than where the pipe is installed slightly deeper in the cobble. It is believed this is an effect
mostly relevant to the model rather than the field system and arises through the influence of capillarity, permeability, and
pipe elevation of the soil compared to the cobble adjacent to the pipe. 相似文献
855.
The effect of the variation of river water levels on the estimation of groundwater recharge in the Hsinhuwei River,Taiwan 总被引:1,自引:1,他引:0
Jung-Wei Chen Hsun-Huang Hsieh Hsin-Fu Yeh Cheng-Haw Lee 《Environmental Earth Sciences》2010,59(6):1297-1307
Land subsidence is a serious problem in Taiwan’s Yunlin area due to groundwater overpumping. There are safety risks in the
high-speed railway structures in the areas of Siluo, Huwei, Tuku, and Yuanchang towns that run from north to south in the
Yunlin area. Therefore, it is important to increase the groundwater recharge and to remedy the land subsidence in this area.
The purpose of this study is to use the stream-flow estimation model (SF) and the groundwater flow numerical software MODFLOW
(MF) to estimate the stream infiltration with consideration to the variation of the river water level in the Hsinhuwei River.
The Ferris analytical model (FA) and MF are used to estimate the increased stream infiltration after the water level of the
river rises. The hydraulic parameters required for each model are obtained from field observations and laboratory experiments.
The results indicate that the assessment of the stream infiltration obtained through the SF and MF models are 264.2 × 104 and 170.9 × 104 m3/year, respectively. When the river water level increases by about 2.5 m, the annual stream infiltration obtained through
the FA and MF models significantly increases by 31.6 × 104 and 26.4 × 104 m3/year, respectively. Taken together, the stream storages estimated using these two models indicate that an increasing efficiency
of groundwater recharge is within the range of 10.0–18.5%. 相似文献
856.
Alan F. Hamlet Se-Yeun Lee Kristian E. B. Mickelson Marketa M. Elsner 《Climatic change》2010,102(1-2):103-128
Climate strongly affects energy supply and demand in the Pacific Northwest (PNW) and Washington State (WA). We evaluate potential effects of climate change on the seasonality and annual amount of PNW hydropower production, and on heating and cooling energy demand. Changes in hydropower production are estimated by linking simulated streamflow scenarios produced by a hydrology model to a simulation model of the Columbia River hydro system. Changes in energy demand are assessed using gridded estimates of heating degree days (HDD) and cooling degree days (CDD) which are then combined with population projections to create energy demand indices that respond both to climate, future population, and changes in residential air conditioning market penetration. We find that substantial changes in the amount and seasonality of energy supply and demand in the PNW are likely to occur over the next century in response to warming, precipitation changes, and population growth. By the 2040s hydropower production is projected to increase by 4.7–5.0% in winter, decrease by about 12.1–15.4% in summer, with annual reductions of 2.0–3.4%. Larger decreases of 17.1–20.8% in summer hydropower production are projected for the 2080s. Although the combined effects of population growth and warming are projected to increase heating energy demand overall (22–23% for the 2020s, 35–42% for the 2040s, and 56–74% for the 2080s), warming results in reduced per capita heating demand. Residential cooling energy demand (currently less than one percent of residential demand) increases rapidly (both overall and per capita) to 4.8–9.1% of the total demand by the 2080s due to increasing population, cooling degree days, and air conditioning penetration. 相似文献
857.
It is common to think of hot deserts, i.e. hot arid or dry lands, as areas of little rain situated in the middle parts of the world, that are simply 'just there'. However, most of the world's deserts have a long geological history, sometimes of 50 million years or more and ways have been developing for some time now, particularly from geomorphological studies, of not only erecting the law of superposition of strata for the desert but also 'absolute' dating. The authors have often worked commercially in deserts world-wide but their recent experiences in the Oman have brought home to them the excellent work that has been going on in the last two or three decades in evaluating the geological history of deserts. The Oman experience is described in a feature in the next issue. 相似文献
858.
If the binding energy of the pulsar's surface is not so high (the case of a neutron star), both negative and positive charges will flow out freely from the surface of the star. An annular free flow model for γ-ray emission of pulsars is suggested. It is emphasized that: (1) Two kinds of acceleration regions (annular and core) need to be taken into account. The annular acceleration region is defined by the magnetic field lines that cross the null charge surface within the light cylinder. (2) If the potential drop in the annular region of a pulsar is high enough (normally the case for young pulsars), charges in both the annular and the core regions could be accelerated and produce primary gamma-rays. Secondary pairs are generated in both regions and stream outwards to power the broadband radiations. (3) The potential drop grows more rapidly in the annular region than in the core region. The annular acceleration process is a key process for producing the observed wide emission beams. (4) The advantages of both the polar cap and outer gap models are retained in this model. The geometric properties of the γ-ray emission from the annular flow are analogous to that pre-sented in a previous work by Qiao et al., which match the observations well. (5) Since charges with different signs leave the pulsar through the annular and the core regions respectively, the current closure problem can be partially solved. 相似文献
859.
This article derives the closed‐form solutions for estimating the vertical surface displacements of cross‐anisotropic media due to various loading types of batter piles. The loading types include an embedded point load for an end‐bearing pile, uniform skin friction, and linear variation of skin friction for a friction pile. The planes of cross‐anisotropy are assumed to be parallel to the horizontal ground surface. The proposed solutions are never mentioned in literature and can be developed from Wang and Liao's solutions for a horizontal and vertical point load embedded in the cross‐anisotropic half‐space. The present solutions are identical with Wang's solutions when batter angle equals to 0°. In addition, the solutions indicate that the surface displacements in cross‐anisotropic media are influenced by the type and degree of material anisotropy, angle of inclination, and loading types. An illustrative example is given at the end of this article to investigate the effect of the type and degree of soil anisotropy (E/E′, G′/E′, and ν/ν′), pile inclination (α), and different loading types (a point load, a uniform skin friction, and a linear variation of skin friction) on vertical surface displacements. Results show that the displacements accounted for pile batter are quite different from those estimated from plumb piles, both driven in cross‐anisotropic media. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
860.
Dong‐Chan Koh Ho‐Wan Chang Kwang‐Sik Lee Kyung‐Seok Ko Yongje Kim Won‐Bae Park 《水文研究》2005,19(11):2225-2245
Ground water from springs and public supply wells was investigated for hydrochemistry and environmental isotopes of 3H, 18O and D in Jeju volcanic island, Korea. The wells are completed in a basaltic aquifer and the upper part of hydrovolcanic sedimentary formation. Nitrate contamination is conspicuous in the coastal area where most of the samples have nitrate concentrations well above 1 mg NO3 N/l. Agricultural land use seems to have a strong influence on the distribution of nitrate in ground water. Comparison of stable isotopic compositions of precipitation and ground water show that ground water mostly originates from rainy season precipitation without significant secondary modification and that local recharge is dominant. 3H concentration of ground water ranged from nearly zero to 5 TU and is poorly correlated with vertical location of well screens. The occurrence of the 3H‐free, old ground water is due to the presence of low permeability layers near the boundary of the basaltic aquifer and the hydrovolcanic sedimentary formation, which significantly limits ground water flow from the upper basaltic aquifer. The old ground water exhibited background‐level nitrate concentrations despite high nitrate loadings, whereas young ground water had considerably higher nitrate concentrations. This correlation of 3H and nitrate concentration may be ascribed to the history of fertilizer use that has increased dramatically since the early 1960s in the island. This suggests that 3H can be used as a qualitative indicator for aquifer vulnerability to nitrate contamination. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献