Ecological health effects of rural livelihood and poverty reduction strategies in the Lake Bosomtwe basin of Ghana     

Prince Osei-Wusu Adjei  Daniel Buor  Pascal Addrah 《GeoJournal》2017,82(3):609-625

Despite the growing recognition that poverty and environmental degradation remain a threat to achieving sustainable development goals, poverty–environment relationship is rarely explored. Crucial is the changing geography of the Lake Bosomtwe basin of Ghana. In this paper we examine how intensive and extensive fishing and farming in the name of livelihood sustainability, poverty reduction and human well-being undermine ecological health within the lake basin by subjecting data collected from 250 respondents to factor analysis. From a geo-referenced and processed classification of remotely sensed and GIS images over three periods using the maximum likelihood classifier algorithm, the results showed that, built up areas within the lake basin increased from 543.64 ha in 1986 to 7682.97 ha in 2008. Dense forest and rangeland decreased from 8698.95 and 22,660.88 ha over the same period to 1416.33 and 8577.99 ha in 2008 respectively. Other indicators such as water levels and fish stock also saw drastic reduction. The results further showed that major changes in the ecological landscape of the basin over the years are the outcomes of both direct and indirect drivers such as slash and burn agriculture, unregulated development of tourism facilities, overfishing, use of illegal fishing gear, poverty, annual overturn, climate change, market and institutional failures. Hence, a paradigm shift from the traditional site level forest restoration efforts to a landscape level, and a “conservation first principle” as a top priority in planning for the future, as well as focus on non-farm activities to reduce pressure on the natural capital are required.  相似文献   

Study of high and low amplitude wave trains of cosmic ray diurnal variation during solar cycle 23     

Ambika Singh  Anil Kumar Tiwari  S. P. Agrawal 《Journal of Astrophysics and Astronomy》2010,31(2):89-96

A detailed study has been conducted on the long-term changes in the diurnal variation of cosmic rays in terms of high and low amplitude wave trains event (HAEs/LAEs) during the period 1996–2008 (solar cycle 23), using the neutron monitor data from Kiel neutron monitoring station. As such, 17 HAE and 48 LAE cases have been detected and analyzed. These HAEs appear quite dominantly during the declining phase as well as near the maximum of the solar activity cycle 23. In contrast, the low amplitude events (LAEs) are inversely correlated with solar activity cycle. In fact, LAEs appear quite dominantly during the minimum phase of the solar activity. When we compare our results for diurnal phase with that observed on an annual average basis, we notice no significant diurnal phase shift for HAEs as well as for LAEs. Moreover, we find that the high-speed solar wind streams (HSSWS) do not play any significant role in causing these variations. These results are discussed on the basis of that observed in earlier cycles.  相似文献   

Mean sea level determination from satellite altimetry     

W. D. Kahn  B. B. Agrawal  R. D. Brown 《Marine Geodesy》2013,36(2):127-144

The primary experiment on the Geodynamics Experimental Ocean Satellite‐3 (GEOS‐3) is the radar altimeter. This experiment's major objective is to demonstrate the utility of measuring the geometry of the ocean surface, i.e., the geoid. Results obtained from this experiment so far indicate that the planned objectives of measuring the topography of the ocean surface with an absolute accuracy of ±5 m can be met and perhaps exceeded. The GEOS‐3 satellite altimeter measurements have an instrument precision in the range of ±25 cm to ±50 cm when the altimeter is operating in the “short pulse”; mode. After one year's operations of the altimeter, data from over 5,000 altimeter passes have been collected. With the mathematical models developed and the altimeter data presently available, mapping of local areas of ocean topography has been realized to the planned accuracy levels and better. This paper presents the basic data processing methods employed and some interesting results achieved with the early data. Plots of mean sea surface heights as inferred by the altimeter measurements are compared with a detailed 1^o × 1° gravimetric geoid.  相似文献   

Assessment of the geochemical reactivity of Fe-DOM complexes in wetland sediment pore waters using a nitroaromatic probe compound   总被引：1，自引：0，他引：1  

J. Alexandra Hakala  Yu-Ping Chin  Sheela G. Agrawal 《Geochimica et cosmochimica acta》2009,73(5):1382-6822

The reductive capacity of Fe(II) present in anoxic sediment pore waters affects biogeochemically significant processes that occur in these environments, such as metal speciation, mineral solubility, nutrient bioavailability, and the transformation of anthropogenic organic compounds. We studied the reduction of pentachloronitrobenzene (PCNB) in natural pore waters to elucidate the reductive capacity of Fe(II) complexes, and monitored the redox-active species responsible for the observed kinetics. Differential pulse polarography (DPP) scans of sediment pore waters from a coastal Lake Erie wetland (Old Woman Creek National Estuarine Research Reserve, Huron, OH) revealed an increase in both Fe(III)-organic and Fe(II) species to a depth of ∼30 cm below the sediment-water interface. Concentrations of dissolved organic matter (DOM) in pore waters increased while pH decreased with depth. We found that Fe(II) was necessary for rapid PCNB reduction (<24 h), and observed faster reduction with increased pH. PCNB reduction in preserved pore waters (acidified to pH 2.5 after pore water extraction and raised to the native pH (6.7-7.6) prior to reaction) was similar to that observed in a model system containing Fe(II) and fulvic acid isolated from this site. Conversely, PCNB reduction in unaltered pore water was significantly slower than that observed in preserved pore water, indicating that the Fe(II) speciation and its reductive capacity differed. DPP scans of pore waters used for kinetic studies confirmed that pH-adjustment affected Fe_T speciation in the pore waters, as the Fe(III)-DOM peak current was lowered or disappeared completely in the preserved pore water samples. These data show that pH-adjustment of pore waters presumably alters both their complexation chemistry and reactivity towards PCNB, and shows how small changes in Fe complexation can potentially affect redox chemistry in anoxic environments. Our results also show that reactive organic Fe(II) complexes are naturally present in wetland sediment pore waters, and that these species are potentially important mediators of Fe(II)/Fe(III) redox biogeochemistry in anoxic sedimentary environments.  相似文献   

Evolution of Ganges–Brahmaputra western delta plain: Clues from sedimentology and carbon isotopes     

A. Sarkar  S. Sengupta  J.M. McArthur  P. Ravenscroft  M.K. Bera  Ravi Bhushan  A. Samanta  S. Agrawal 《Quaternary Science Reviews》2009,28(25-26):2564-2581

Sedimentology, carbon isotope and sequence stratigraphic analysis of subsurface sediments from western part of Ganges–Brahmaputra (GB) delta plain shows that a Late Quaternary marine clay and fluvial channel-overbank sediments of MIS 5 and 3 highstands are traceable below the Holocene strata. During the Last Glacial Maximum (LGM) sea-level lowering of >100 m produced a regional unconformity (type 1), represented by palaeosols and incised valley. C4 vegetation expanded on exposed lowstand surface in an ambient dry glacial climate. At 9 ka transgression inundated the lowstand surface pushing the coastline and mangrove front 100 km inland. Simultaneous intensification of monsoon and very high sediment discharge (4–8 times than modern) caused a rapid aggradation of both floodplain and estuarine valley fill deposits between 8 and 7 ka. The Hoogli River remaining along its present drainage possibly acted as the main conduit for transgression and sediment discharge that was subsequently abandoned. C3 vegetation dominated the delta plain during this time. From 7 ka onward progradation of delta plain started and continued till recent. This period experienced a mixed C3–C4 vegetation with localized mangroves in the mid-Holocene to dominant return of C4 vegetation in the late Holocene period. The study indicates that while the initiation of western part of GB delta occurred at least 1 ka earlier than the global mean delta formation age, the progradation started at 7 ka, at least 2 ka earlier than thought before. The terrestrial vegetation change was modulated by changes in depositional environment, specific ecological niches and climate rather than pCO₂.  相似文献   

Effect of the presence of a conducting channel between India and Sri Lanka Island on the features of the equatorial electrojet     

Mita Rajaram  B. P. Singh  N. Nityananda  A. K. Agrawal 《Geophysical Journal International》1979,56(1):127-138

Summary. Transient geomagnetic variations like SSCs, Bays, Sq and storm-time variations show anomalously large Z amplitudes at the three permanent magnetic observatories in India under the equatorial electrojet. Our earlier studies have shown that these anomalies cannot be explained in terms of the usual coastal effect. Another unique feature of this area is the small equatorial enhancement of all magnetic fluctuations, which still remains to be completely understood. It is also noticed that Z/H ratio at Annamalainagar is very large for night-time variations but becomes insignificant for day-time fluctuations, whereas no such large difference is seen at Trivandrum, the other coastal station. All the above features have been explained here by introducing the presence of a conducting channel in the lower crust or upper mantle between India and Sri Lanka Island. The anomalies of the equatorial electrojet in the Indian region thus do not necessitate the conducting surface of the mantle to be deeper in this area as has been suggested by earlier workers. A less conducting mantle in the Indian region otherwise could be difficult to incorporate in the present theories of mantle convection when this area is known to be tectonically active. The presence of the conducting channel is further confirmed by analogue model experiments of Papamastorakis. We further observe that the equatorial electrojet does have an associated internal part in the Indian region.  相似文献   

Heat and mass transfer of an oscillatory flow with Hall current,II     

H. L. Agrawal  P. C. Ram  V. Singh 《Astrophysics and Space Science》1983,94(2):383-393

An analysis of Hall current on the combined effects of thermal and mass diffusion of an electrically conducting liquid past an infinite vertical porous plate is performed. Analytical expressions for the transient velocity, the transient temperature in the boundary layer and the skin-friction on the plate are derived. The effects of various parameters on the velocity, temperature, shearing stresses and rate of heat transfer are shown by graphs and tables.  相似文献   

Evidence of low density sub-crustal underplating beneath western continental region of India and adjacent Arabian Sea: Geodynamical considerations     

O.P. Pandey  P.K. Agrawal  J.G. Negi 《Journal of Geodynamics》1996,21(4):365-377

The known high mobility of the Indian subcontinent during the period from 80 to 53 Ma has evoked considerable interest in recent times. It appears to have played an important role in shaping the subcontinental structures of western India and the adjoining Arabian Sea. During this period, a major catastrophic event took place in the form of Deccan volcanism, which coincides with the biological mass extinction at the K-T boundary, including the death of dinosaurs. The origin of Deccan volcanism is still being debated.Geophysically, western India and its offshore regions exhibit numerous prominent anomalies which testify to the abnormal nature of the underlying crust-lithosphere. In this work, we develop a two-dimensional structural model of these areas along two long profiles extending from the eastern basin of the Arabian Sea to about 1000 km inland. The model, derived from the available gravity data in the oceanic and continental regions, is constrained by seismic and other relevant information in the area, and suggests, for the first time, the presence of an extensive low-density (2.95–3.05 g/cm³) sub-crustal underplating. Such a layer is found to occur between depths of 11 and 20 km in the eastern basin of the Arabian Sea, and betweeen 45 and 60 km in the continental region where it is sandwiched in the lower lithosphere. The low density may have been caused as a result of serpentinization or fractionation of magma by a process related in some way to the Deccan volcanic event. Substantial depletion of both oceanic and continental lithosphere is indicated. We hypothesize that the present anatomy of the deformed lithosphere of the region at the K-T boundary is the result of substantial melt generated owing to frictional heat possibly giving rise to a hot cell like condition at the base of the lithosphere, resulting from the rapid movement of the Indian subcontinent between 80 and 53 Ma.  相似文献   

Palaeoclimate,stratigraphy and prehistory in north and west Rajasthan     

D. P. Agrawal  P. S. Datta  Zahid Hussain  R. V. Krishnamurthy  V. N. Misra  S. N. Rajaguru  P. K. Thomas 《Journal of Earth System Science》1980,89(1):51-66

Quaternary formations in western Rajasthan are of fluvial, locustrinal and aeolian origins. Fossil gravel ridge of Jayal in Nagaur District is one of the earliest quaternary formations so far recorded in the region. A rich lower palaeolithic habitation-cum-workshop site has been discovered in association with the gravel ridge. Multiple evidence for climatic change in the area during the quaternary period is discussed.  相似文献   

X-Ray emission from the pleiades cluster     

P. C. Agrawal  G. R. Riegler  K. P. Singh 《Astrophysics and Space Science》1983,92(1):177-180

Detection of a new X-ray source and its identification with the Pleiades cluster is reported here. The new X-ray source has an X-ray luminosity of ～10³² ergs s^?1 in the 0.15–3.0 keV energy band. The observed X-ray emission could be explained as integrated emission from a large number of stars in the cluster.  相似文献