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991.
The unique characteristics of Small Island Developing States and structural vulnerabilities they face in terms of development
have earned them particular consideration in the development agenda. This article sheds light on some of the vulnerabilities
that these countries face, making particular reference to their environmental and economic vulnerabilities. It then highlights
the ambiguous role that international migration plays in the recreation of those vulnerabilities. 相似文献
992.
In this study, the electrical resistivity of soil having different chemical weathering index (CWI) was measured, and the correlation
between CWI and the electrical resistivity was estimated. The electrical resistivity of soil varies with CWI of soil. The
difference in the electrical resistivities of soils having different weathering degrees is clear at lower water contents.
At the volumetric water contents estimated in this study, CWI could be described by a linear equation of electrical resistivity
with the constants related to the volumetric water content. The findings in this study suggest that the electrical resistivity
could be used as an effective alternative for estimating the weathering degree of soil. 相似文献
993.
Natural precipitation and water samples from passive devices were collected at Mt. Vesuvius and Vulcano Island, Italy, during
the period 2004–2006, in order to investigate its possible interactions with fumarolic gases. Evidence of chemical reactions
between fumarolic fluids and rain samples before and after its deposition into the sampling devices was found at Vulcano Island.
Very low pH values (down to 2.5) and significant amounts of chlorine and sulfate (up to 22 mEq/l) were measured at sampling
points located close to the fumarolic field. In contrast, anthropogenic contributions and/or dissolution of aerosols (both
maritime and continental) influence the chemistry of rainwaters at Mt. Vesuvius, which show inter-annual variations that are
highly consistent with those recorded at the coastal site at Vulcano Island. Chemistry of waters directly exposed to fumarolic
fluids may then give useful information about its temporal evolution, holding the signal of the “maximum” chemical event occurred
in the meanwhile. In addition, the observation of the health status of vegetation colonizing the immediate surroundings of
the fumarolic fields, due to its strong dependence on the interactions with these fluids, may work as a possible biomarker
of volcanic activity. 相似文献
994.
Fly ash is a waste by-product obtained from the burning of coal by thermal power plants for generating electricity. When bulk
quantities are involved, in order to arrest the fugitive dust, it is stored wet rather than dry. Fly ash contains trace concentrations
of heavy metals and other substances in sufficient quantities to be able to leach out over a period of time. In this study
an attempt was made to study the leachabilities of a few selected trace metals: Cd, Cu, Cr, Mn, Pb and Zn from two different
types of class F fly ashes. Emphasis is also laid on developing an alternative in order to arrest the relative leachabilities
of heavy metals after amending them with suitable additives. A standard laboratory leaching test for combustion residues has
been employed to study the leachabilities of these trace elements as a function of liquid to solid ratio and pH. The leachability
tests were conducted on powdered fly ash samples before and after amending them suitably with the matrices lime and gypsum;
they were compacted to their respective proctor densities and cured for periods of 28 and 180 days. A marked reduction in
the relative leachabilities of the trace elements was observed to be present at the end of 28 days. These relative leachability
values further reduced marginally when tests were performed at the end of 180 days. 相似文献
995.
The Nature and Distribution of Particulate Matter in the Mandovi Estuary,Central West Coast of India
Pratima Mohan Kessarkar Venigalla Purnachandra Rao Ranjan Shynu Prakash Mehra Blossom E. Viegas 《Estuaries and Coasts》2010,33(1):30-44
Systematic seasonal variations of suspended particulate matter (SPM) along a 44-km transect of the Mandovi estuary reveal
that the concentrations of SPM are low at river-end stations, increase generally seaward, and are highest at sea-end stations
of the estuary. An estuarine turbidity maximum (ETM) occurs at sea-end stations during June–September when river discharge
is high and also in February–May when river discharge is low. These are the two windiest times of year, the former associated
with the southwest monsoon and the latter characterized by a persistent sea breeze. The salinity vs. SPM plot shows that high
SPM is a seaward deposit and skewed landward. Suspended matter comprised of floccules, fecal pellets, and aggregates that
consist of clay and biogenic particles occur everywhere in the estuary. Diatoms are the most common and are of marine type
at the sea-end and freshwater-dominated at river-end stations of the estuary. SPM is characterized by kaolinite- and smectite-rich
clay mineral suites at the river- and sea-end stations, respectively. Smectite concentrations increase seawards with the increase
in SPM content and are not influenced by salinity. Wind-driven waves and currents and biogeochemical processes at the mouth
of estuary likely play an important role in the formation of ETM in resuspension and transformation of SPM into floccules
and aggregates and in their upkeep or removal. 相似文献
996.
Ecological restoration of the Wangaloa coal mine in southern New Zealand is hindered by a range of geoecological factors.
The site has some substrate acidification (down to pH 1) and acid rock drainage with discharge waters initially down to pH
4, although this has since risen to ca. pH 6. Surface and ground waters develop elevated sulfate (up to 700 mg/kg) during
oxidation of pyrite in coal and quartz in waste rock. Coal has elevated boron content (up to 450 mg/kg) and surface waters
on coal-rich waste rock have up to 6 mg/L dissolved boron. Evaporation causes formation of salt encrustations dominated by
gypsum with minor boron salts. Boron is bioavailable and may be at toxic levels (>200 mg/kg) in some plants. Quartz-rich waste
rock is readily eroded, and develops a cm-scale low-nutrient quartz pebble armouring layer with low water retention properties.
All waste rocks including loess siltstone have low nutrient contents, and low moisture retention properties, that are barely
sufficient for plant establishment. Native plants introduced to the site during rehabilitation have grown on loess substrate
(up to fivefold increase in height over 3 years), with poor or no growth on coal-rich and quartz-rich substrates. In contrast,
natural colonisation of manuka (Leptospermum scoparium) has been most effective at revegetation on even the most hostile substrates. This natural revegetation has been facilitated
by islands of manuka established accidentally during 60 years of mining history. Manuka from local genetic stock is most viable
for this revegetation, and introduced manuka seedlings have had a 70% mortality rate. Natural plant colonisation is the key
step in overall ecosystem recovery, and invertebrates rapidly colonise beneath new shrubs irrespective of the nature of the
substrate from vegetation islands that have high invertebrate numbers and species richness. 相似文献
997.
This paper presents the computation of time series of the 22 July 2007 M 4.9 Kharsali earthquake. It occurred close to the Main Central Thrust (MCT) where seismic gap exists. The main shock and
17 aftershocks were located by closely spaced eleven seismograph stations in a network that involved VSAT based real-time
seismic monitoring. The largest aftershock of M 3.5 and other aftershocks occurred within a small volume of 4 × 4 km horizontal extent and between depths of 10 and 14 km.
The values of seismic moment (M
∘) determined using P-wave spectra and Brune’s model based on f
2 spectral shape ranges from 1018 to 1023 dyne-cm. The initial aftershocks occurred at greater depth compared to the later aftershocks. The time series of ground motion
have been computed for recording sites using geometric ray theory and Green’s function approach. The method for computing
time series consists in integrating the far-field contributions of Green’s function for a number of distributed point source.
The generated waveforms have been compared with the observed ones. It has been inferred that the Kharsali earthquake occurred
due to a northerly dipping low angle thrust fault at a depth of 14 km taking strike N279°E, dip 14° and rake 117°. There are
two regions on the fault surface which have larger slip amplitudes (asperities) and the rupture which has been considered
as circular in nature initiated from the asperity at a greater depth shifting gradually upwards. The two asperities cover
only 10% of the total area of the causative fault plane. However, detailed seismic imaging of these two asperities can be
corroborated with structural heterogeneities associated with causative fault to understand how seismogenesis is influenced
by strong or weak structural barriers in the region. 相似文献
998.
Marcin Słowik Tadeusz Sobczyński Zygmunt Młynarczyk 《Environmental Earth Sciences》2010,59(5):957-966
Research concerning chemical constitution of alluvial sediments was done in the lower course of the Obra river (Western Poland).
The fragment of vertical profile, which consisted of various alluvial sediments (fine sands, peats, and sandy silts) was chosen
for detailed analysis. The main research problem was to determine if lithology and chemical constitution of alluvial deposits
are interconnected in a distinct way within studied section of the Obra river valley, and, if changes of chemical elements’
concentration could be used to illustrate depositional processes, which take place in riverbed and floodplain. Concentrations
of Fe, Mn, Cu, Zn, Ca, Mg, and K were determined in collected sediment samples. Next, geochemical groups of alluvial sediments
were distinguished using cluster analysis. Investigated changes of chemical elements’ concentration show that there is a distinct
border between the environment of organic sediments, which marks the place of former functioning of the Obra riverbed, and
sandy silts, which were deposited within floodplain during floods. Besides, floodplain sediments, riverbed sediments, and
reductive environment within peat deposits were singled out on the basis of the analysis. 相似文献
999.
Zuzana Kratinová Matej Machek Vladimír Kusbach 《Journal of the Geological Society of India》2010,75(1):267-277
Investigations on a set of experimental models of highly viscous intrusions were carried out in order to study the internal
strain pattern during vertical ascent and emplacement of granite intrusions. The strain pattern was determined by means of
anisotropy of magnetic susceptibility (AMS) resulting from the orientation of magnetite particles in a liquid plaster medium.
The modelled intrusions show distinct fabrics reflecting the flow of a rheologically complex, non-Newtonian material. During
the vertical growth of the intrusion, constrictional vertical fabrics are transposed into flattening fabrics, and along with
the development of low-intensity fabric domains are passively transported upwards. Vertical growth takes place along subvertical
thrust shear zones that satisfactorily explain the discordant magmatic fabrics in granites along intrusion sides. The resulting
complex fabric patterns suggest that the vertical movement of material in ascending intrusions is accommodated by various
flow mechanisms operating simultaneously. 相似文献
1000.
Sushant S Naik Meloth Thamban A Rajakumar Witty D’Souza C M Laluraj Arun Chaturvedi 《Journal of Earth System Science》2010,119(1):41-49
Ice and firn core studies provide one of the most valuable tools for understanding the past climate change. In order to evaluate the temporal isotopic variability recorded in ice and its relevance to environmental changes, stable isotopes of oxygen and hydrogen were studied in a firn core from coastal Dronning Maud Land, East Antarctica. The annual δ 18O profile of the core shows a close relation to the El Niño Southern Oscillation (ENSO) variability. The ENSO indices show significant correlation with the surface air temperatures and δ 18O values of this region during the austral summer season and support an additional influence related to the Southern Annular Mode (SAM). The correlation between the combined ENSO-SAM index and the summer δ 18O record seems to have been caused through an atmospheric mechanism. Snow accumulation in this region illustrates a decreasing trend with opposite relationships with δ 18O data and surface air temperature prior and subsequent to the year 1997. A reorganization of the local water cycle is further indicated by the deuterium excess data showing a shift around 1997, consistent with a change in evaporation conditions. The present study thus illustrates the utility of ice-core studies in the reconstruction of past climate change and suggests possible influence of climatic teleconnections on the snow accumulation rates and isotopic profiles of snow in the coastal regions of east Antarctica. 相似文献