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1.
Wetland is the conjunction of lake and terrene where human activities are concentrated. From the viewpoints of material transport and cycling in the terrene-lake system, wetland is the buffer where sand and mud, heavy metals, pollutants and nutrients are tarried. In this paper, we provide a case study based on the temporal and spatial distribution of elements in the Wangling River catchment, a small sub-catchment of Longgan Lake in the middle reaches of the Yangtze River. We have found that wetland can buffer major heavy metals such as Cr, Cu, etc.significantly, but has a little buffer function to some active elements such as Fe and Mn, which are always transported as solutions. Human activities not only influence the distribution of elements, but also weaken the buffer function of wetland. Intensive human activities in the Longgan Lake area in the past 70 years have been recorded in stream, wetland and lake sediments, especially the human activity events such as deforesting and reclaiming on a large scale in 1958 and the 1980‘s. Human activities caused the increase of sedimentation rates since the 1950‘ s, as well as the increase of elements‘ concentrations. The extensive use of fertilizers and pesticides since the 1960‘ s have led to the increase of total P concentrations. Increasing SO2 emission accelerate the process of cation exchange in soil, and enhance the leaching of Mn out of soils. Permanent storing of water causes the soil gleyification that also intensifies the leaching of Mn.These are two major reasons for the obvious increase of manganese concentrations in recent 20 years in Longgan Lake. Intensive human activities since the 1950s‘ have intensified the population in this region and thus destroyed the buffer function of wetland.  相似文献   

2.
《Geoforum》2002,33(2):195-219
This paper attempts a two-tiered analysis of what has come to be referred to as the `security-park', i.e., that South African variation of the `gated community' which combines Blakely and Snyder's [Fortress America: Gated communities in the United States, Brookings Institution Press, Washington, 1999] typically separable `lifestyle', `prestige' and `security zone' gated community types. The first part of this analysis reviews the existing literature on gated communities and relates it back to the South African situation. The second part, both theoretical and empirical, draws on Foucault's [Utopias and heterotopias, in: N. Leach (Ed.), Rethinking Architecture: A Reader in Cultural Theory, Routledge, London, 1997] notion of the heterotopia, and on a variety of textual representations of Dainfern. The heterotopia, as an `analytics of difference' becomes a particularly important means of critique here, drawing attention to security-parks as: (1) possessing a precise and well-defined function within society (a function which typically coalesces around points of social crisis), (2) operating distinctive systems of admission and exclusion, (3) containing certain `juxtaposed incompatibilities' (of which a paradoxical `heterochroneity' is one of the most pronounced elements), (4) embodying – via the espousal of a certain `utopics' – an `alternate mode of social ordering' (in Hetherington's [The Badlands of Modernity: Heterotopia and Social Ordering, Routledge, New York, 1997] term). Each of these analytical strands constitutes a discursive relay through which one might deduce wider networks of social power or in the case of Dainfern or security-parks more generally, historical structures of the race- and class-structuring of privilege and poverty. Representations and practices of the security-park are in this way indicative of a far larger political rationality – a self-justificatory set of entitlements, warrants and exclusionary prerogatives which we have labelled a “rights” of privilege.  相似文献   

3.
Quantitative rock physics analyses were used to determine the lithology and pore fluid of a reservoir in the Niger Delta. Inaccurate prediction of lithology and pore fluid results in the inaccurate determination of other petrophysical properties and parameters such as porosity, permeability, and net pay. This research is to predict lithology and pore fluid using rock physics analysis. However, reservoir zones were also predicted. Density, compressional wave velocity, and shear wave velocity logs were used as input to calculate elastic parameters such as velocity ratio, Poisson’s ratio, and bulk modulus. The calculated velocity ratio log was used to differentiate between sand and shale. Poisson’s ratio and velocity ratio using Goodway interpretation template were carried out and used to delineate pore fluid content, gas sand, oil sand, and sandstone formation from crossplot analysis.  相似文献   

4.
1IntroductionUp to now,eutrophication is still a problem af-fecting water quality in many developing countries.Themost important nutrients causing eutrophication arephosphates,nitrates and ammonia(Lijklema,1995;Horne and Goldman,1994).Eutrophic waters are…  相似文献   

5.
Landslips are often triggered due to non-engineered excavation of potential unstable slopes. Such slips can be stabilized by implementing suitable remedial measures.A landslip occurred at a drilling site of Oil India Limited in Mizoram State due to slope excavation. There was an immediate concern to protect the slope as the drilling platform and the highway at the top of the slope are at risk if further landslide occurs in future. Slope stability analysis of the failed slope was carried out to design suitable control measures for the protection of the slope from further sliding. Slope stability using various methods indicated that the slope is marginally stable. To improve the stability of the slope, suitable retaining structure at the toe of the slope was suggested and designed. Stability analysis performed with inclusion of retaining wall showed a significant increase in factor of safety of the slope. The suggested remedial measure has been implemented at the site and there is no landslip reported since then. The paper presents the results of the slope stability analysis and the design details of the retaining structure prescribed as the protection measure.  相似文献   

6.
The inversion of the Middle Proterozoic Belt sedimentary basin during Late Cretaceous thrusting in Montana produced a large eastwardly-convex salient, the southern boundary of which is a 200 km-long oblique to lateral ramp subtended by a detachment between the Belt rocks and Archean basement. A 10 km-long lateral ramp segment exposes the upper levels of the detachment where hanging wall Belt rocks have moved out over the Paleozoic and Mesozoic section. The hanging wall structure consists of a train of high amplitude, faulted, asymmetrical detachment folds. Initial west-east shortening produced layer parallel shortening fabrics and dominantly strike slip faulting followed by symmetrical detachment folding. “Lock-up” of movement on the detachment surface produced regional simple shear and caused the detachment folds to become asymmetrical and faulted. Folding of the detachment surface after lock-up modified the easternmost detachment folds further into a southeast-verging, overturned fold pair with a ramp-related fault along the base of the stretched mutual limb.  相似文献   

7.
Chloramphenicol （CAP） is an antibiotic commonly used in aquaculture as a prophylactic or disinfectant to prevent diseases, or as a chemotherapeutic agent to control diseases. This antibiotic is either spread directly in the aquatic environment or administered through medicated feeds. It may be directly exposed to or enter the environment by leaching from uneaten feeds or from the aquatic animals＇ excrements. The antibiotic also directly enters the environment through pharmaceutical wastewater. Toxicity of CAP to human bone marrow has been linked to fatal aplastic anemia. Antimicrobial residues enter the environment, which may also establish a selective pressure in favour of antimicrobial-resistant bacteria. The residues of antibiotics may pose potential risk to public health or increase the occurrence of antibiotic-resistant bacteria in the aquatic environment. Due to these perceived risk, treatment of CAP in farm animals intended for human consumption has been restricted. However, residue of CAP in the environment is still a concern. There have been some reports on the residual effects of CAP on aquaculture and on microbial resistance to CAP in certain environments. The biotransformation of CAP in aquaculture pond sediments has been reported, which indicated that salinity is one of the many environmental factors that affect the degradation of CAP. However, acclimatization and screening of dominant bacteria for biodegrading CAP have been rarely studied. This paper studied the microbial degradation of CAP. In order to screen the dominant bacteria for degrading, the source of bacteria was sampled from the aquaculture pond sediments of Baiyun Borough, Guangzhou, China. 60 mg/L CAP was used as a sole carbon source to screen CAP-degrading bacteria and the dominant bacteria were acclimated after 2 months.  相似文献   

8.
This paper gives an account of the research that the authors conducted on the cyclic sequences, events and evolutionary history from Proterozoic to Meso-Cenozoic in the Sino-Korean plate based on the principle of the Cosmos-Earth System. The authors divided this plate into 20 super-cyclic or super-mega-cyclic periods and more than 100 Oort periods. The research focused on important sea flooding events, uplift interruption events, tilting movement events, molar-tooth carbonate events, thermal events, polarity reversal events, karst events, volcanic explosion events and storm events, as well as types of resource areas and paleotectonic evolution. By means of the isochronous theory of the Cosmos-Earth System periodicity and based on long-excentricity and periodicity, the authors elaborately studied the paleogeographic evolution of the aulacogen of the Sino-Korean plate, the oolitic beach platform formation, the development of foreland basin and continental rift valley basin, and reconstructed the evolution  相似文献   

9.
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10.
The objective of this work was to study sorption–desorption and/or precipitation–dissolution processes of Hg(II) compounds considering an eventual contact of soils with Hg-bearing wastes. In addition, this study contributes new data about Hg(II) chemistry in alkaline systems. Saline and alkaline soils with low organic matter (<1 %) and high clay content (60–70 %) were obtained near a chlor-alkali plant. Batch techniques were used to perform the experiments using 0.1 M NaNO3 solutions. Total Hg(II) concentrations ranged from 6.2 × 10?8 to 6.3 × 10?3 M. Sorption of Hg(II) was evaluated at two concentration ranges: (a) 6.2 × 10?8 to 1.1 × 10?4 M, and (b) 6.4 × 10?4 to 6.3 × 10?3 M. At low Hg(II) concentrations, adsorption occurred with a maximum sorption capacity ranging from 4 to 5 mmol/kg. At high Hg(II) concentrations, sorption–precipitation reactions occurred and maximum sorption capacity ranged from 17 to 31 mmol/kg. The distribution of Hg(II) hydrolysis products showed that Hg(OH)2 was the predominant species under soil conditions. According to sorption experiments, X-ray diffraction and chemical speciation modelling, the presence of Hg(OH)2 in the interlayer of the interstratified clay minerals can be proposed. Hg(OH)2 was partially desorbed by repeated equilibrations in 0.1 M NaNO3 solution. Desorption ranged from 0.1 to 0.9 mmol/kg for soils treated with 5.8 × 10?5 M Hg(II), whereas 2.1–3.8 mmol/kg was desorbed from soils treated with 6.3 × 10?3 M Hg(II). Formation of soluble Hg(II) complexes was limited by low organic matter content, whereas neutral Hg(OH)2 was retained by adsorption on clay mineral surfaces.  相似文献   

11.
International Journal of Earth Sciences - The Southern Brasília Orogen is a Neoproterozoic belt that occurs along the southernmost border of the São Francisco Craton where the...  相似文献   

12.
 In order to characterize the hydraulic properties of an aquifer in Finland comprising two subvertical fracture zones, observation-well responses were matched with generalized radial flow (GRF) type curves. The responses in six wells out of seven are consistent with the GRF model. The fractional flow dimensions (1–1.2 and 1.5) were determined by regression analysis of straight-line slopes and type-curve matching. In each test, the flow dimensions in the neighboring fracture zone range from 2–2.25. Comparisons of the late-time responses with the asymptotic GRF solution and the flow dimensions obtained by reversing the pumping and observation points suggest homogeneous hydraulic properties. Deviations in responses can be explained by flow-path tortuosity. After assessments of the extent of the flow and radial distances along the fracture system, hydraulic conductivities and storativities were determined from the results of the type-curve matching procedure. The obtained hydraulic conductivities are 1.3×10–5 to 7.9×10–5 m/s and 5.0×10–6 to 2.5×10–5 m/s for the western and the eastern fracture zones, respectively. The results were verified by applying them to analytical solutions for pumping wells. The calculated pumping-well responses are consistent with the observations. The analysis of flow dimension also enhances qualitative interpretations on the hydrogeology of fracture zones. Received, April 1997 · Revised, September 1997 · Accepted, May 1998  相似文献   

13.
Disaster associated with natural hazards can lead to important changes—positive or negative—in socio-ecological systems. When disasters occur, much attention is given to the direct disaster impacts as well as relief and recovery operations. Although this focus is important, it is noteworthy that there has been little research on the characteristics and progress of change induced by disasters. Change, as distinct from impacts, encompasses formal and informal responses to disaster events and their direct and indirect impacts. While smaller disasters do not often lead to significant changes in societies and organizational structures, major disasters have the potential to change dominant ways of thinking and acting. Against this background, the article presents an analytical framework for distinguishing change from disaster impacts. Drawing from research in Sri Lanka and Indonesia, formal and informal changes after the Indian Ocean Tsunami of 2004 are examined and discussed against the background of the conceptual framework. The changes examined range from the commencement of the peace process in Aceh, Indonesia, to organizational and legal reforms in Sri Lanka. The article concludes that change-making processes after disasters need to be understood more in depth in order to derive important strategic policy and methodological lessons learned for the future, particularly in view of the increasing complexity and uncertainty in decision making due to climate change.  相似文献   

14.
The 100-km diameter Popigai impact crater (astrobleme), which formed 35.7?Ma ago as a result of the collision of an ordinary chondrite asteroid, was discovered in the 1970s. The impact site was studied in detail for nearly two decades, and various geological investigations were performed there. They included drilling of numerous wells (about 850), geophysical surveys, and investigations of impact breccias and impactites. This research was generally performed in connection with the identification of the unique resource of industrial impact diamonds, which were found in impact rocks for the first time in the world. The extensive research data acquired over 20–30 years include geological maps, collections of rock samples and thin sections, core samples, etc. All these materials are stored in the Russian Research Geological Institute in St Petersburg. Although a lot of data on the Popigai crater have already been published, the available materials and new analytical methods offer the opportunity to obtain some new data on mechanisms of rock-forming processes during an impact event, to improve existing geological models, and to compare in detail all these features to those established in other large craters on the Earth. Modelling of the physical processes of impact cratering has been extended and new data contribute significantly to the study of impact cratering and other problems of comparative planetology. In particular, many different hypotheses of rock-forming mechanisms are tested, especially those of impact melting of various target lithologies, homogenisation of huge volumes of melt products, and their mode of ejection, deposition, cooling, etc.  相似文献   

15.
An extremely large rock avalanche occurred on April 9, 2000 at Yigong, Tibet, China. It started with an initial volume of material of 90?×?106 m3 comprising mainly of loose material lying on the channel bed. The rock avalanche travelled around 10 km in horizontal distance and formed a 2.5-km-long by 2.5-km-wide depositional fan with a final volume of approximately 300?×?106 m3. An energy-based debris flow runout model is used to simulate the movement process with a new entrainment model. The entrainment model considers both rolling and sliding motions in calculating the volume of eroded material. Entrainment calculation is governed by a second order partial differential equation which is solved using the finite difference method. During entrainment, it is considered that the total mass is changed due to basal erosion. Also the profile of the channel bed is adjusted accordingly due to erosion at the end of each calculation time step. For Yigong, the profile used in the simulation was extracted from a digital elevation model (DEM) with a resolution of 30 m?×?30 m. Measurements obtained from site investigation, including deposition depth and flow height at specific location, are used to verify the model. Ground elevation-based DEM before and after the event is also used to verify the simulation results where access was difficult. It is found that the calculated runout distance and the modified deposition height agree with the field observations. Moreover, the back-calculated flow characteristics based on field observations, such as flow velocity, are also used for model verifications. The results indicate that the new entrainment model is able to capture the entrainment volume and depth, runout distance, and deposition height for this case.  相似文献   

16.
Over the past decade, Indigenous peoples in Taiwan have shown a strong desire for the ??return of the Native??; this includes the Truku people in eastern Taiwan. Seizing a favorable climate of political opportunity structure in 2004, the Truku people first succeeded in obtaining the Taiwanese government??s recognition as an independent Indigenous nation??formerly considered a subgroup of the Atayal Nation. Then, riding on accumulated political resources, a few Truku elites started to engage in a government-initiated tribal mapping project. However, while tribal mapping originated in some North American Indigenous communities with a bottom-up process and spirit, the Taiwanese government sent both money (through the municipal government) and an academic expert team into the community to initiate and to assist (the elite group) with the tribal mapping project. These top-down government initiatives resulted in at least two major ill effects. First of all, two other subgroups of the Atayal Nation living in the same region were systematically excluded from the tribal mapping project, to the extent that their own traditional territories became part of the traditional territory of the newly formed Truku Nation. Secondly, possibly expecting a high political payoff on the part of elites, elite competition arose during the process of tribal mapping, with the interests of other community members largely ignored. As such, instead of establishing a decolonizing force, the ??return of the Truku?? appears to have achieved ??colonialism from within.?? This paper analyzes this process and considers ways to develop a more democratic strategy for the ??return of the Truku.??  相似文献   

17.
Our understanding of monsoon circulation timing’s at the orbital scale is currently a matter of debate. Here, we compare previous and recently published results of Indian, East Asian, West African and East African monsoon variability. We note different timings between the East African, West African, Indian and East-Asian monsoon systems for the most recent 45 ka, where the age models are constrained by AMS dating. On this basis, we construct different orbital forcing “reference curves” and apply them to the 200 ka time period for the different monsoon systems. Our results indicate that the ‘global monsoon’ concept at the orbital scale is a misnomer. We find real regional differences in the timing of the monsoon response to orbital forcing and differences in the weight of precession and obliquity in the monsoon records. This work highlights the necessity of studies aimed at understanding the underlying physics of these regional response patterns. This is crucial to a better understanding of monsoon dynamics and improved climate model simulations and comparisons with proxy data.  相似文献   

18.
A hydrogeochemical study was conducted in Thoothukudi district situated in the southeast coast of Tamil Nadu, India to identify the influence of saltwater intrusion and suitability of groundwater for domestic and agricultural purposes. Scattered studies of this coastal region have reported signs of seawater intrusion, salt pan and industrial activity together with natural weathering process. To have a holistic picture of geochemical processes in the entire district, a total of 135 groundwater samples were collected and analyzed for major cations and anions. The geochemical parameters were compared with world and Indian standards and it was found that most samples are unsuitable for drinking purpose. The geochemical facies of the groundwater showed Na–Cl as the dominant water type indicating the saline nature of the groundwater. Chadda’s plots show that most of the samples fall in the Na–Cl type of water due to seawater intrusion. The samples were classified with parameters like sodium absorption ratio, residual sodium carbonate, total hardness, chloride, index to base exchange, electrical conductivity and facies to determine their suitability for irrigation purpose. It was inferred that the samples falling along the coast are not suitable for the irrigation purpose. The seawater-mixing percentage indicates that strong mixing was observed in the near shore and at the proximity of the salt pan. The permanent hardness was predominant in all the samples compared to the carbonate hardness reducing its domestic usability.  相似文献   

19.
The River Ganges being the most sacred river and lifeline to millions of Indians in serving their water requirements is facing excessive threat of pollution. Under various river management and conservation strategies for its protection, the assessment of water quality of its main tributary Ramganga River is lacking. This study focuses on assessment of physicochemical and heavy metal pollution of the Ramganga River by application of multivariate statistical techniques. Sampling of Ramganga River at sixteen sampling sites was carried out in three seasons (summer, monsoon and winter) of 2014. The collected water samples were analyzed for physicochemical parameters and heavy metals. Results from cluster analysis (CA) of the data divided the whole stretch of the river into three clusters as elevation from 1304 to 259 m as less polluted, from 207 to 154 m as moderately polluted and from elevation 154 to 139 m as high-polluted stretches with anthropogenic as main sources of pollution in high-polluted stretch. Principal component analysis of the seasonal dataset resulted in three significant principal components (PC) in each season explaining 72–8% of total variance with strong loadings (>0.75) of PC1 on fluoride (F?), chloride (Cl?), sodium (Na+), calcium (Ca2+), magnesium (Mg2+), bicarbonate (HCO3 ?), total dissolved solids and electrical conductivity. Temporal variation by one-way ANOVA (Analysis of Variance) showed significant seasonal variation was in the pH, chemical oxygen demand, biochemical oxygen demand, turbidity, HCO3 ?, F?, Zn, cadmium (Cd) and Mn (p < 0.05). Turbidity showed approximately a twofold increase in monsoon season due to rainfall in the catchment area and subsequent flow of runoff into the river. Concentration of HCO3 ?, F? and pH also showed similar increase in monsoon. The concentration of Zn, Cd and Mn showed an increasing trend in summers compared to monsoon and winter season due to dilution effect in the monsoon season and its lasting effect in winters.  相似文献   

20.
Holocene sedimentation patterns and environmental development in Aarhus Bay, Denmark, were reconstructed based on proxy analyses of two sediment cores (M1 and M5). Together, the two cores offer an opportunity to examine the history of the area during the past c. 10 000 years. The investigation consisted of acoustic mapping and multi-proxy analyses of the sediment cores including macrofossils, sediment physical properties, sediment accumulation rates, grain size, and X-ray fluorescence elemental counts. Radiocarbon dating of the two sediment successions revealed that they cover the periods c. 10 000–3700 cal. a BP (M1) and c. 4400 cal. a BP to the present (M5). The data from the M1 site indicate the presence of a near-shore lake environment between c. 10 000 and 9000 cal. a BP. The first intrusion of marine water into the area is dated to c. 9000 cal. a BP. In the following c. 1300 years, brackish-water conditions prevailed in the area characterized by a mixture of taxa from marine, limnic and terrestrial habitats, reflecting a shallow estuarine environment. Around 7700 cal. a BP full marine conditions were established, accompanied by a marked increase in sedimentation rates. The changes to full marine conditions and higher sedimentation rates are probably due to a significant sea-level rise leading to flooding of former land areas and intensified erosion. A subsequent distinct decrease in sedimentation rates around 6350 cal. a BP is presumably linked to a previously documented sea-level drop about this time. Continuous sedimentation ceased around 3700 cal. a BP in the central part of the bay, most probably due to a major sea-level lowering involving widespread erosion. In the eastern and deeper part of the bay, sedimentation continued until today. Fully marine conditions prevailed there for at least the last 4400 years.  相似文献   

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