Investigating the metal contamination status from recycling e-waste sites from Dakar,Senegal

Environmental Science and Pollution Research - In Senegal, processes employed for recycling e-wastes result in release of so-called heavy metals in the environment. In this study, the metal...     

A cascaded fuzzy-LOPA risk assessment model applied in natural gas industry

Natural gas plants demand high amount of energy provided through immense fuel gas units that may suffer risk hazards. Implementing a safety management system is the most efficient way of allocating resources for safety. This paper adopts The Layer of Protection Analysis (LOPA) risk Management associated with Fuzzy Logic methodology to prevent or limit industrial accidents. We provide an innovative cascaded fuzzy-LOPA model for certain hazardous scenarios and at different frequencies of occurrence. The introduced model is tested at moderate and high risk levels controlled in its practical limits through the use of Safety Integrity Functions (SIF). Obtained results show how this fuzzy-LOPA achieves better results to maintain the Safety Integrity Level (SIL) rating to acceptable limits.     

Connectivity for conservation: a framework to classify network measures

Graph theory, network theory, and circuit theory are increasingly being used to quantify multiple aspects of habitat connectivity and protected areas. There has been an explosive proliferation of network (connectivity) measures, resulting in over 60 measures for ecologists to now choose from. Conceptual clarification on the ecological meaning of these network measures and their interrelationships is overdue. We present a framework that categorizes network measures based on the connectivity property that they quantify (i.e., route-specific flux, route redundancy, route vulnerability, and connected habitat area) and the structural level of the habitat network to which they apply. The framework reveals a lack of network measures in the categories of "route-specific flux among neighboring habitat patches" and "route redundancy at the level of network components." We propose that network motif and path redundancy measures can be developed to fill the gaps in these categories. The value of this framework lies in its ability to inform the selection and application of network measures. Ultimately, it will allow a better comparison among graph, network, and circuit analyses, which will improve the design and management of connected landscapes.     

Design of a tracer test experience and dynamic calibration of the hydraulic model for a full-scale wastewater treatment plant by use of AQUASIM.

The setup of the hydraulic model structure of wastewater treatment plants (WWTPs) is an important step in the calibration of activated sludge models. The hydrodynamics of a full-scale municipal WWTP (Monterrey, Mexico) has been studied by means of the use of tracer tests and of a commercial simulator. A presimulation approach allowed the authors to quantify the appropriate rhodamine mass, set up a sampling plan, and evaluate the anticipated visual effect of the tracer test in the receiving river. The hydraulic behavior of the aeration tank for the first treatment line, a 7-cell plug-flow reactor, was shown to be best represented by 5 virtual mixed-tanks-in-series. The second treatment line, which included a vertical loop reactor (VLR), was best modeled as 3 tanks-in-series. The VLR, alone, was shown to be similar to a continuously stirred tank reactor, and not a circuit of tanks, as generally used to represent oxidation ditch reactors.     

Concentrating anthropogenic disturbance to balance ecological and economic values: applications to forest management

To maintain healthy ecosystems, natural-disturbance-based management aims to minimize differences between unmanaged and managed landscapes. Two related approaches may help accomplish this goal, either applied together or in isolation: (1) concentrating anthropogenic disturbance through zoning (with protected areas and intensive management); and (2) emulating natural disturbances. The purpose of this paper is to examine the effects of these two approaches, applied both in isolation and in combination, on the structure of the forest landscape. To do so, we use a spatially explicit landscape simulation model on a large fire-dominated landscape in eastern Canada. Specifically, we examine the effects of (1) increasing the maximum size of logged stands (cutblocks) to better emulate the full range of fire sizes in a fire-dominated landscape, (2) increasing protected areas, and (3) adding aggregated or dispersed intensive wood production areas to the landscape in addition to protected areas (triad management). We focus on maximizing the amount and minimizing the fragmentation of old-growth forest and on reducing road construction. Increasing maximum cutblock size and adding protected areas led to reduced road construction, while the latter also resulted in less fragmentation and more old growth. Although protected areas led to reduced harvest volume, the addition of an intensive production zone (triad management) counterbalanced this loss and resulted in more old growth than equivalent scenarios with protected areas but no intensive production zone. However, we found no differences between aggregated and dispersed intensive wood production. Our results imply that differences between unmanaged and managed landscapes can be reduced by concentrating logging efforts through a combination of protected areas and intensive wood production, and by creating some larger cutblocks. We conclude that the forest industry and regulators should therefore seek to increase protected areas through triad management and consider increasing maximum cutblock size. These results add to a growing body of literature indicating that intensive management on a small part of the landscape may be better than less intensive management spread out over a much larger part of the landscape, whether this is in the context of forestry, agriculture, or urban development.     

Climate Variability and Environmental Stress in the Sudan-Sahel Zone of West Africa

Environmental change in the Sudan-Sahel region of West Africa (SSWA) has been much debated since the droughts of the 1970s. In this article we assess climate variability and environmental stress in the region. Households in Senegal, Mali, Burkina Faso, Niger, and Nigeria were asked about climatic changes and their perceptions were compared across north–south and west–east rainfall gradients. More than 80% of all households found that rainfall had decreased, especially in the wettest areas. Increases in wind speeds and temperature were perceived by an overall 60–80% of households. Contrary to household perceptions, observed rainfall patterns showed an increasing trend over the past 20 years. However, August rainfall declined, and could therefore potentially explain the contrasting negative household perceptions of rainfall trends. Most households reported degradation of soils, water resources, vegetation, and fauna, but more so in the 500–900 mm zones. Adaptation measures to counter environmental degradation included use of manure, reforestation, soil and water conservation, and protection of fauna and vegetation. The results raise concerns for future environmental management in the region, especially in the 500–900 mm zones and the western part of SSWA.     

Deleterious effects of cypermethrin on rat liver and kidney: protective role of sesame oil

The involvement of reactive oxygen species (ROS) has been implicated in the toxicity of various pesticides. Our study was designed to investigate the induction of oxidative stress by cypermethrin; a Type II pyrethroid in rat liver and kidney. In addition, the protective role of sesame oil against the toxicity of cypermethrin was investigated. Animals were divided into four equal groups; the first group used as control while groups 2, 3 and 4 were treated with sesame oil (5 mL/kg b.w), cypermethrin (12 mg/kg b.w) and the combination of both sesame oil (5 mL/kg b.w) plus cypermethrin (12 mg/kg b.w), respectively. Rats were daily administered with their respective doses for 30 days by gavage. Repeated oral administration of cypermethrin was found to reduce the level of glutathione (GSH) and the activities of the antioxidant enzymes. While, the level of TBARS was elevated indicating the presence of oxidative stress. The activities of LDH, AST and ALT were decreased in the liver extract while increased in the plasma of the cypermethrin-treated group. Also, the levels of urea and creatinine were significantly increased after treatment with cypermethrin. Liver and kidney injury was confirmed by the histological changes. In conclusion, the administration of sesame oil provided significant protection against cypermethrin-induced oxidative stress, biochemical changes, histopathological damage and genomic DNA fragmentation.     

Participatory research and sustainable development in the Sahelo-Sudanian region

SUMMARY

A participatory research programme was conducted in the groundnut basin of Senegal, where there was a need to intensify the local farming systems. The research yielded a set of technical references and profitable innovations, which were introduced through specific development actions. The technology transfer aims at the establishment of sustainable farming systems and takes into account the climatic risks and innovation costs. Identification of research themes and implementation of results was based on various analyses: climatic analysis at regional level (establishment of climatic zones) and identification of constraints at farm level. Farmers' interests and the research results were combined to define suitable interventions for each surveyed farm, with the aim of increasing farm income and restoring soil fertility. The research also yielded elements for formulating an appropriate and realistic agricultural policy for the region. Clearly, the development of livestock farming activities is essential in bringing new economic life into the region and increasing the sustainability of farming systems in erratic climatic conditions.     

Respirometry-based evaluation of the fate and possible effects of antifreeze on activated sludge

This paper focuses on environmental concerns regarding used antifreeze. It shows the results of laboratory respirometric tests conducted to evaluate the potential impact of antifreeze on activated sludge. In this first step of the study, only the components of virgin antifreeze were addressed, i.e. ethylene glycol, and antifoaming and corrosion inhibitory substances. The plateau resulting from oxygen uptake rate measurements of mixed liquor taken at the end of an aeration tank is used as a reference to evaluate the response of biomass to pulse injection of increasing dosages of new antifreeze, compared to that of formaldehyde, a known toxic compound. While 200 mg/L of formaldehyde steadily decreased the biomass activity (7 mg O2/Lh), there were no toxicity effects for doses up to 5000 mg/L of ethylene glycol from new antifreeze coolant (23 mg O2/Lh, compared to the initial 15 mg O2/Lh for the mixed liquor). It is estimated that ethylene glycol concentration in municipal wastewaters should be several order of magnitude lower then the 1000 mg/L shown to be tolerated by the biomass in this work, but at the present stage, the research does not provide enough information to recommend a definitive management scheme for antifreeze discharge. Many other management issues for used antifreeze must be addressed in future studies before any decision on tolerating sewer discharge in Mexico, as a transitory management option that will conciliate the actual practices with legality, can be made.