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Wasiu Olanrewaju Raji Ifedolapo Gbadesere Obadare Marry Abiodun Odukoya Lukman Mobolaji Johnson 《Arabian Journal of Geosciences》2018,11(7):144
Three years after the oil spillage and pipeline explosion that claimed about 100 human lives at Ijegun Community of Lagos–Nigeria, a combination of carefully designed 2D Electrical Resistivity Profilling and Vertical Electrical Sounding methods was deployed to map and characterise the subsurface around the contaminated site. Data acquired were processed, forward modelled and tomographically inverted to obtain the multi-dimensional resistivity distribution of subsurface. The results of the study revealed high resistivity structures that indocate the presence of contaminant (oil plumes) of different sizes and shapes around the oil leakage site. These high resistivity structures are absent in the tomograms and resistivity-depth slices computed for Iyana—a linear settlement not affected by oil spillage. The five geo-electric layers and the resistivities delineated in the area are the top soil layer, 220–670 Ωm; clayey sand layer, 300–1072 Ωm; top sand layer, 120–328 Ωm; mudstone/shale layer, 25–116 Ωm and the bottom sand layer, 15–69 Ωm. The base of the first four geo-electric layers corresponds to 3.9, 8.4, 27.2 and 34.6 m respectively. The two groundwater aquifers delineated correspond to the third and fifth geo-electric layers. The top aquifer has been infiltrated by oil plumes. The depth penetrated by the oil plume decreases from 32 m to about 24 m across the survey profiles from the two ends. It was concluded that the contaminant plumes from the oil spillage are yet to be completely degraded as at the time of the study. It is recommended that the contaminated site be remediated to remove or reduce the contaminant oil in the subsurface. 相似文献
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Christophe Béné Louisa Evans David Mills Solomon Ovie Aminu Raji Ahmadu Tafida Amaga Kodio Famory Sinaba Pierre Morand Jacques Lemoalle Neil Andrew 《Global Environmental Change》2011,21(4):1173-1184
Resilience thinking is an important addition to the range of frameworks and approaches that can be used to understand and manage complex social–ecological systems like small-scale fisheries. However, it is yet to lead to better environmental or development outcomes for fisheries stakeholders in terms of food security, improved livelihoods and ecological sustainability. This paper takes an empirical approach by focusing on the fundamentals of resilience thinking to evaluate its usefulness in developing relevant management interventions in small-scale fisheries in the Niger River Basin in West Africa. The paper presents the outputs of a participatory assessment exercise where both fishery communities and local experts were involved at two different scales. The resilience frame used was designed to facilitate the identification of socially defined thresholds that help delineate the desirability of the current system configuration and provides a diagnosis framework that tailors management solutions to problems in local context. The analysis highlights some key contributions from resilience thinking to the challenge of diagnosis in small-scale fisheries management in developing countries, as well as important contributions that emerge from taking a pragmatic and critical approach to its application. 相似文献
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Despite the numerous advantages of crosswell seismic data over surface seismic data, crosswell seismic geophysics is still underutilized and underdeveloped. The factors limiting the full utilization of crosswell data include the lack of standardized methods for processing and imaging the data. This is because crosswell data is not completely understood. To improve the understanding of crosswell data, we performed acoustic and elastic modeling of a west Texas carbonate oilfield data using finite difference methods and crosswell geometry. To account for the different wave modes in the field data, we decomposed the full data into its constituent wave modes. Results of the forward modeling show that elastic synthetic data is a better representation of crosswell field data than the popular acoustic synthetic data. Wavefield decomposition gave insight into the time-space kinematics behavior of the different wave modes that constitute the full data. Overall, the study improved our understanding of crosswell field data. The learning from this study has been utilized to perform data-driven reflection enhancement processing where the discerned characteristic of different seismic arrival is utilize to suppress unwanted and enhanced the desired wave modes. The processing reduced the complex data to only up-going P-P reflections that can be imaged to reveal the subtle geological structures of the oilfield. 相似文献
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The profile distribution of total, diethylene triamine penta-acetic acid (DTPA)- and 0·1
HCl-extractable Fe and Mn were determined in 12 pedons formed on three contiguous sand dunes in the semi-arid savanna of Nigeria. The total Fe and Mn contents varied from 100 to 3750 and 40 to 11,375 μg g−1, respectively. Values of 0·1
HCl-extractable Fe and Mn varied from 8·0 to 123 and 1·5 to 43·5 μg g−1, respectively. The corresponding values of DTPA-extractable Fe and Mn were 4·5 to 16·0 and 1·0 to 38·8 μg g−1. Total Fe and Mn correlated significantly with clay in nearly all the dunes (p≤ 0·01) but were not significantly correlated with organic matter. The 0·1
HCl-extractable Mn had a positive significant correlation with soil pH (r= 0·58*) in Illela dunes but a negative significant correlation with pH in the Sangiwa dunes (r= −0·75***). The values of extractable Fe and Mn in the sand dune soils are above the critical limits reported in other literature, thus deficiencies of these micronutrients do not pose a problem to crop production in the study area. 相似文献
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Sadasivan Nair Raji Geetha Nair Aparna Changatharayil N. Mohanan Narayanan Subhash 《Journal of the Indian Society of Remote Sensing》2017,45(3):463-475
Chlorophyll fluorescence is an indicator of plant photosynthetic activity and has been used to monitor the health status of vegetation. Several studies have exploited the application of red/far-red chlorophyll fluorescence ratio in detecting the impact of various types of stresses in plants. Recently, sunlight-induced chlorophyll fluorescence imaging has been used to detect and discriminate different stages of mosaic virus infection in potted cassava plants with a multi-spectral imaging system (MSIS). In this study, the MSIS is used to investigate the impact of drought and herbicide stress in field grown crop plants. Towards this control and treatment groups of colocasia and sweet potato plants were grown in laterite soil beds and the reflectance images of these crop plants were recorded up to 14-days of treatment at the Fraunhofer lines of O2 B at 687 nm and O2 A at 759.5 nm and the off-lines at 684 and 757.5 nm. The recorded images were analyzed using the Fraunhofer Line Discrimination technique to extract the sunlight-induced chlorophyll fluorescence component from the reflectance images of the plant leaves. As compared to the control group, the chlorophyll fluorescence image ratio (F 687/F 760) in the treatment groups of both the plant varieties shows an increasing trend with increase in the extent of stress. Further, the F 687/F 760 ratio was found to correlate with the net photosynthetic rate (Pn) and stomatal conductance (gs) of leaves. The correlation coefficient (R 2) for the relationship of F 687/F 760 ratio with Pn were found to be 0.78, 0.79 and 0.78, respectively for the control, herbicide treated and drought treated colocasia plants, while these were 0.77, 0.86 and 0.88, respectively for sweet potato plants. The results presented show the potential of proximal remote sensing and the application F 687/F 760 fluorescence image ratio for effective monitoring of stress-induced changes in field grown plants. 相似文献
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Mansir Aminu Ahmad Nazri Bin Muhamad Ludin Abdul-Nassir Matori Khamaruzaman Wan Yusof Lawal Umar Dano Imtiaz Ahmed Chandio 《Environmental Earth Sciences》2013,70(3):1113-1124
The need for a sustainable approach in tourism development is very often addressed among the academia, the authorities and the stakeholders, as well as the apparent need for tools, which will guide the decision environment in evaluation and planning. This research aims to identify conservation and compatible areas for tourism development in Johor Ramsar sites, using spatial modeling in geographic information system (GIS). The study describes a methodological approach based on the integrated use of GIS and multi criteria decision evaluation (MCE) to identify nature conservation and development priorities among the wetland areas. A set of criteria was defined to evaluate wetland biodiversity conservation and development. Having defined the criteria, the next step was selecting suitable indicators and variables to measure the selected criteria. Subsequently the criteria were evaluated from conservation and tourism development point of view. These criteria were then weighted using the pair wise comparison technique of MCE and the results were integrated into GIS. Several conservation scenarios were generated so as to simulate different evaluation perspectives. The scenarios were then compared to highlight the most feasible and to propose a conservation and development strategy for the wetland areas. The generation and comparison of conservation and development scenarios highlighted the critical issues of the decision problem. This study represents an important contribution to effective decision-making because it allows one to gradually narrow down a problem. 相似文献
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A strong geochemical gradient was observed in the thick overburden aquifer of the Asa drainage basin. Different types of
groundwater occur at different (downslope) locations and groundwater table depths. The following sequence was noticed with
increasing distance downslope or with increasing groundwater table depth:
1. Ca–Mg–HCO3 water at about 390-m groundwater table elevations or upslope locations.
2. Ca–Mg–HCO3–Cl water at middle-slope locations or groundwater table elevations of about 350 m above sea level;
3. Ca–Mg–SO4–Cl water at downslope locations or groundwater table elevations of about 300 m above sea level.
In this basin, changes in the type of water are expected at about every 40–50 m depth from the surface. Statistical analysis
via the determination of the correlation coefficient (r) and regression analysis shows that about 80–99% of the variation in groundwater chemistry is accounted for by the topography,
using the model presented in this paper. The rate of change in the sequence will depend on the permeability of the aquifer,
which determines the rate of groundwater flow and the residence time, and the nature of recharge.
Received: 4 February 1997 · Accepted: 22 July 1997 相似文献