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71.
This paper explores the impact that a new type of pineapple, and subsequent changing consumer preferences in the Global North, has had on the livelihoods of pineapple growers in Ghana. The paper starts by tracing how research and development in Costa Rica by the world’s largest producers of pineapple, Del Monte and Dole, have resulted in a new variety MD2. This new pineapple type has been marketed in the EU through campaigns carried out by plantation companies via supermarkets. Consumer preferences have subsequently switched to MD2 away from the varieties which previously dominated the market, including the Ghanaian grown Smooth Cayenne. Ghanaian smallholders have experienced a dramatic drop in the demand for Smooth Cayenne and are unable to switch to growing MD2. The Ghanaian pineapple sector is consequently being restructured with large-scale pineapple farms, principally run by transnational companies, growing large quantities of MD2 for export. Through a detailed empirical study of the changing livelihoods of pineapple growers in two settlements in Ghana, we show how smallholders have been affected in differing ways as transnational companies have increasingly entered the market. Recent attempts to incorporate smallholders as producers of niche pineapple products are discussed. The paper illustrates the mutual benefits of linking global value chain analysis with livelihood analysis. 相似文献
72.
Towards an integrated arid zone water management using simulation-based optimisation 总被引:5,自引:3,他引:2
Jens Grundmann Niels Schütze Gerd H. Schmitz Saif Al-Shaqsi 《Environmental Earth Sciences》2012,65(5):1381-1394
For ensuring both optimal sustainable water resources management and long-term planning in a changing arid environment, we
propose an integrated Assessment-, Prognoses-, Planning- and Management tool (APPM). The new APPM integrates the complex interactions
of the strongly nonlinear meteorological, hydrological and agricultural phenomena, considering the socio-economic aspects.
It aims at achieving best possible solutions for water allocation, groundwater storage and withdrawals including saline water
management together with a substantial increase of the water use efficiency employing novel optimisation strategies for irrigation
control and scheduling. To obtain a robust and fast operation of the water management system, it unites process modeling with
artificial intelligence tools and evolutionary optimisation techniques for managing both water quality and quantity. We demonstrate
some key components of our methodology by an exemplary application to the south Al-Batinah region in the Sultanate of Oman
which is affected by saltwater intrusion into a coastal aquifer due to excessive groundwater withdrawal for irrigated agriculture.
We show the effectiveness and functionality of a new simulation-based water management system for the optimisation and evaluation
of different irrigation practices, crop pattern and resulting abstraction scenarios. The results of several optimisation runs
indicate that due to contradicting objectives, such as profit-oriented agriculture versus aquifer sustainability only a multi-objective
optimisation can provide sustainable solutions for the management of the water resources in respect of the environment as
well as the socio-economic development. 相似文献
73.
Carlos Descourvières Niels Hartog Bradley M. Patterson Carolyn Oldham Henning Prommer 《Applied Geochemistry》2010
The injection and recovery of oxic water into deep anoxic aquifers may help to alleviate short- and long-term imbalance between freshwater supply and demand. The extent and structure of physical and geochemical heterogeneity of the aquifer will impact the water quality evolution during injection, storage and recovery. Water–sediment interactions within the most permeable parts of the aquifer, where the bulk of the injectant will penetrate, may dominate, however, water quality may also be impacted by interactions within the finer-grained, less permeable but potentially highly reactive media. In this study, the heterogeneity of the reductive capacity of an aquifer selected for water reuse projects was characterised, the amount, type and reactivity of the sedimentary reductants present determined, and the relationship between reductive capacity and sedimentary lithologies quantified. The average potential reductive capacities (PRCTOT), based on total organic C and pyrite concentrations of the sediment, were quantified for sands (382 μmol O2 g−1), clays (1522 μmol O2 g−1), and silts (1957 μmol O2 g−1). Twenty-seven samples, spanning the three different lithologies, were then incubated for 50 days and the measured reductive capacities (MRC) determined for the sands (29.2 μmol O2 g−1), silts (136 μmol O2 g−1), and clays (143 μmol O2 g−1). On average, the MRC were 10% of the PRCTOT. The main consumers of O2 were pyrite (20–100%), sedimentary organic matter (SOM; 3–56%), siderite (3–28%) and Fe(II)-aluminosilicates (8–55%). The incubation data plus hydrogeochemical modelling, indicated that pH-buffering was controlled firstly by dissolution of trace level carbonates, followed by dissolution of feldspars. Zinc, Co, Ni, Cd and Pb were readily mobilized during incubation. 相似文献
74.
Søren Erbs Poulsen Keld Rømer Rasmussen Niels Bøie Christensen Steen Christensen 《Hydrogeology Journal》2010,18(1):161-171
A monitoring system, including five groups of piezometers and five vertical multielectrode profiling probes (VMEP), has been installed in an aquifer beneath a coastal dune in Denmark. In order to assess the salinity distribution within the aquifer, geoelectrical data were gathered in March, June and September 2008, by measuring a dipole-dipole and gradient array using multielectrode profiling. Interpretation of the processed resistivity data was performed by regularized inversion using a one-dimensional, horizontally layered model of formation resistivity. The standard deviation on estimated layer log-resistivity was 0.01–0.03. By estimating two parameters of a power function, observed fluid conductivities derived from samples of porewater were related to corresponding estimated formation resistivities. The conductivity profiles correlate with a winter situation in March with high sea level, active recharge and significant wave activity, causing increased hydraulic heads, a thicker freshwater lens and salt water overlying freshwater close to the sea. In June, the thickness of the freshwater lens is reduced due to less recharge and prevailing offshore winds, imposing density-stable conditions and a sharper transition between fresh and brackish water. During the autumn, aquifer recharge is enhanced and hydraulic heads increase, resulting in a thicker freshwater lens. 相似文献
75.
Long-term trends in ten non-target North Sea fish species 总被引:1,自引:1,他引:1
76.
Sediment supply from landslide-dominated catchments: implications for basin-margin fans 总被引:1,自引:0,他引:1
The sediment flux from a mountainous catchment can be expressed as a function of a landslide rate constant κ which accounts for the vigour of hillslope erosion. Since the incising drainage network flushes all or a portion of the products of hillslope erosion to a range front where fan deposition takes place, a conservation of solid sediment volume allows the fan area and progradation distance to be calculated. These parameters are related primarily to the discharge of sediment from the catchment and to local tectonic subsidence.
A survey of modern alluvial fans in a wide range of climatic and tectonic settings shows that the effects of climate and bedrock lithology cannot be discriminated in the scatter of data of catchment area vs. fan area. However, by focusing on over 100 fans in the arid and semiarid zone of SW USA, the impact of tectonic subsidence rate is unambiguous. Although further quantitative data on local tectonic subsidence rates are urgently required, our preliminary analysis suggests considerable potential for reconstructing palaeocatchments where basin tectonic subsidence rates can be estimated. The progradation distances of fans from the northern and southern margins of the Middle Devonian Hornelen Basin of Norway, and the western and north-eastern margins of the Mio-Pliocene Ridge Basin, California, allow catchment sizes and denudation rates to be approximated. Although unique solution sets are not possible, an iteration of parameter values allows plausible parameter combinations to be calculated which shed light on the tectonic and sedimentary history of the proximal basin and upland source regions. Model results suggest significant asymmetry in basin subsidence rates, catchment slopes and transport mechanics between the two margins. 相似文献
A survey of modern alluvial fans in a wide range of climatic and tectonic settings shows that the effects of climate and bedrock lithology cannot be discriminated in the scatter of data of catchment area vs. fan area. However, by focusing on over 100 fans in the arid and semiarid zone of SW USA, the impact of tectonic subsidence rate is unambiguous. Although further quantitative data on local tectonic subsidence rates are urgently required, our preliminary analysis suggests considerable potential for reconstructing palaeocatchments where basin tectonic subsidence rates can be estimated. The progradation distances of fans from the northern and southern margins of the Middle Devonian Hornelen Basin of Norway, and the western and north-eastern margins of the Mio-Pliocene Ridge Basin, California, allow catchment sizes and denudation rates to be approximated. Although unique solution sets are not possible, an iteration of parameter values allows plausible parameter combinations to be calculated which shed light on the tectonic and sedimentary history of the proximal basin and upland source regions. Model results suggest significant asymmetry in basin subsidence rates, catchment slopes and transport mechanics between the two margins. 相似文献
77.
Michael R. Talbot Niels Bo Jensen Tine Lærdal Maria Letizia Filippi 《Journal of Paleolimnology》2006,35(3):467-489
Bulk organic matter (OM) in sediments that accumulated in Lakes Victoria, Albert and Tanganyika during the major transgression
that transformed these basins from a desiccated or lowstand condition at the time of the Last Glacial Maximum to highstand
with overflow in the terminal Pleistocene and early Holocene, show some striking compositional trends. Sediment OM content
(TOC) and Rock-Eval Hydrogen Index (HI) both rise markedly, reflecting increasing primary productivity during the transgression
and enhanced conditions for the preservation of labile OM, In Lake Victoria rising sedimentary sulphur content tracks the
change in HI. Over the same time interval in all three lakes, δ13COM shows a falling trend of 5–8‰ . Nitrogen isotopic and C/N trends are, in contrast, more variable. Relatively high δ15N values at an early stage in the transgression may reflect isotopic effects associated with ammonia loss from an alkaline
waterbody, while high δ15N later in the transgression was probably due to periods when stratification-related denitrification had a particularly strong
impact upon the lakes' N cycle. The observed changes are attributed to the influence of the landscape drowned during the transgression
upon the nutrient budget of the lake, a rise in river-supplied nutrients as the climate became wetter, and an increasing tendency
to stable chemical stratification as the water column deepened. In the case of δ13C, additional contributory factors were changes in the amount and isotopic composition of river-supplied dissolved inorganic
carbon (DIC) as runoff and soil–moisture turnover rates increased, and the replacement of a C4-grassland dominated flora by
mixed woodland-grassland and forest with a significant presence of C3 plants. Distinct geochemical changes are also apparent
in Lakes Victoria and Albert sediments at the end of the transgression which are consistent with a reduction in nutrient loading.
In the case of N this resulted in biological N fixation becoming a major part of the lakes' N cycle, Some of the observed
geochemical variations may be generally applicable as proxy indicators of major transgressions in large lakes.
IDEAL Contribution No. 152. 相似文献
78.
Niels Grobbe Joost van der Neut Evert Slob Kees Wapenaar Carlos Almagro Vidal Guy Drijkoningen 《Geophysical Prospecting》2016,64(2):361-391
Wavefield decomposition forms an important ingredient of various geophysical methods. An example of wavefield decomposition is the decomposition into upgoing and downgoing wavefields and simultaneous decomposition into different wave/field types. The multi‐component field decomposition scheme makes use of the recordings of different field quantities (such as particle velocity and pressure). In practice, different recordings can be obscured by different sensor characteristics, requiring calibration with an unknown calibration factor. Not all field quantities required for multi‐component field decomposition might be available, or they can suffer from different noise levels. The multi‐depth‐level decomposition approach makes use of field quantities recorded at multiple depth levels, e.g., two horizontal boreholes closely separated from each other, a combination of a single receiver array combined with free‐surface boundary conditions, or acquisition geometries with a high‐density of vertical boreholes. We theoretically describe the multi‐depth‐level decomposition approach in a unified form, showing that it can be applied to different kinds of fields in dissipative, inhomogeneous, anisotropic media, e.g., acoustic, electromagnetic, elastodynamic, poroelastic, and seismoelectric fields. We express the one‐way fields at one depth level in terms of the observed fields at multiple depth levels, using extrapolation operators that are dependent on the medium parameters between the two depth levels. Lateral invariance at the depth level of decomposition allows us to carry out the multi‐depth‐level decomposition in the horizontal wavenumber–frequency domain. We illustrate the multi‐depth‐level decomposition scheme using two synthetic elastodynamic examples. The first example uses particle velocity recordings at two depth levels, whereas the second example combines recordings at one depth level with the Dirichlet free‐surface boundary condition of zero traction. Comparison with multi‐component decomposed fields shows a perfect match in both amplitude and phase for both cases. The multi‐depth‐level decomposition scheme is fully customizable to the desired acquisition geometry. The decomposition problem is in principle an inverse problem. Notches may occur at certain frequencies, causing the multi‐depth‐level composition matrix to become uninvertible, requiring additional notch filters. We can add multi‐depth‐level free‐surface boundary conditions as extra equations to the multi‐component composition matrix, thereby overdetermining this inverse problem. The combined multi‐component–multi‐depth‐level decomposition on a land data set clearly shows improvements in the decomposition results, compared with the performance of the multi‐component decomposition scheme. 相似文献
79.
80.
We present a new, fast and versatile method, the lateral parameter correlation method, of invoking lateral smoothness in model sections of one-dimensional (1D) models. Modern, continuous electrical and electromagnetic methods are capable of recording very large data sets and except for a few cases, standard inversion methodology still relies on 1D models. In environments where the lateral rate of change of resistivity is small, 1D inversion can be justified but model sections of concatenated 1D models do not necessarily display the expected lateral smoothness.
The lateral parameter correlation method has three steps. First, all sounding data are inverted individually. Next, a laterally smooth version of each model parameter, one at a time, is found by solving a simple constrained inversion problem. Identity is postulated between the uncorrelated and correlated parameters and the equations are solved including a model covariance matrix. As a last step, all sounding data are inverted again to produce models that better fit the data, now subject to constraints by including the correlated parameter values as a priori values. Because the method separates the inversion from the correlation it is much faster than methods where the inversion and correlation are solved simultaneously, typically with a factor of 200–500.
Theoretical examples show that the method produces laterally smooth model sections where the main influence comes from the well-determined parameters in such a way that problems with equivalence and poor resolution are alleviated. A field example is presented, demonstrating the improved resolution obtained with the lateral parameter correlation method. The method is very flexible and is capable of coupling models from inversion of different data types and information from boreholes. 相似文献
The lateral parameter correlation method has three steps. First, all sounding data are inverted individually. Next, a laterally smooth version of each model parameter, one at a time, is found by solving a simple constrained inversion problem. Identity is postulated between the uncorrelated and correlated parameters and the equations are solved including a model covariance matrix. As a last step, all sounding data are inverted again to produce models that better fit the data, now subject to constraints by including the correlated parameter values as a priori values. Because the method separates the inversion from the correlation it is much faster than methods where the inversion and correlation are solved simultaneously, typically with a factor of 200–500.
Theoretical examples show that the method produces laterally smooth model sections where the main influence comes from the well-determined parameters in such a way that problems with equivalence and poor resolution are alleviated. A field example is presented, demonstrating the improved resolution obtained with the lateral parameter correlation method. The method is very flexible and is capable of coupling models from inversion of different data types and information from boreholes. 相似文献