An Inverse Almost Ideal Demand System for Oysters in the United States: An Empirical Investigation of the Impacts of Mandatory Labels

In 1991, mandatory warning labels were imposed on the sale of oysters harvested from the Gulf of Mexico. Using an IAIDS model, this paper investigates the impact of these labels on the demand for Gulf product as well related oyster products (the Chesapeake, the Pacific, and imports).Demand and Price Analysis,

Properties of pervious concrete for hydrologic applications

Abstract: This paper presents an experimental investigation that was conducted to examine those properties of interest with regard to the passage of water through pervious concrete. A total of 30 mixtures of pervious concrete were prepared at water-cementitious ratios (w/cm) varied from 0.25 to 0.40. Three aggregate types and sizes were used consisting of 13.2, 9.5 and 6.7 mm granite stone; 6.7 mm shale and 9.5 mm dolomite. Pozzolans were incorporated into mixtures in proportions of 20, 30 and 50% fly ash (FA) or 30% and 50% ground granulated blast furnace slag (GGBS). Compressive strength development in the mixtures was monitored at 7, 14, and 60 days. It was found that strength gain after 14 days generally occurred only in mixtures containing pozzolans. A unique behavior in property relations of pervious concrete was found with compressive strength increasing and porosity decreasing with increase in w/cm, contrary to established knowledge of conventional concrete properties. It was found that mixtures made with 6.7 or 9.5 mm granite stone gave porosity and permeability characteristics that were most suitable for hydrologic applications. Similarly, incorporation of 20% FA, 30% or 50% GGBS in the mixtures gave the most appropriate mechanical and transport properties

Bottom ash and fly ash wastes as alkalinising reagents for neutralising acid mine drainage

Preliminary investigation was conducted to evaluate the utilization of bottom ash and fly ash by-products on a study limited to their role as alkalizing reagents, with the ultimate objective of examining their potential use for insitu treatment of acid mine drainage (AMD) in South African mines. Bottom ash (BA) and fly ash (FA) obtained from a coal-powered electricity generation station were used in varied combined proportions of 100/0, 90/10, 70/30 BA:FA reagent mixtures and used to conduct neutralization tests done at mix proportions varied from 20:1 to 1:1 AMD to reagent mixtures. Three types of acid mine drainage water from an underground gold mine (AMD-Wz), gold tailings dam (AMD-Lc) and a coal mine (AMD-MpK) were used in the investigation. Water quality tests were carried out before and after the neutralisation treatment. It was found that both bottom ash and fly ash are effective alkalinising reagents for neutralising AMD. The materials were found to be most effective when mixed at a ratio no greater than 5:1 of mine water to reagent. Use of the coal ash wastes effectively removed up to 99% of iron from the AMD. The sulphate concentration was also reduced by the treatment but it remained fairly elevated. Manganese concentration reduced as the pH of the treated water increased, reaching a negliglible concentration of < 1.0 mg/l at pH ≥ 11. Further investigations are underway to examine leaching and weathering characteristics of the reagents

Potentiodynamic polarization study of the corrosion characteristics of acid mine drainage

Potentiodynamic tests were carried out to evaluate the attacking characteristics of acid mine drainage (AMD) from South African mines. Tests were done using seven solutions of:- AMD water taken from the field and consisting of two AMD sources from the gold mines and two sources from the coal mines; sulphuric acid, distilled water, synthetic AMD prepared in the laboratory. Tests were done at normal room temperature of 23oC using mild steel and stainless steel samples. Tafel plots were generated and corrosion current (Icorr), corrosion potential (Ecorr), corrosion rates determined in each case. The corrosion rate of AMD from the coal mines was found to be similar to the corrosion of AMD from the gold tailings dam mine, both of which were significantly higher than the corrosion of AMD from the underground gold mine. It is, however, anticipated that the corrosion bevaviour could be different under static conditions and further investigations in this regard are being conducted

Effect of Deep-Fat Frying on Chemical Properties of Edible Vegetable Oils Used By Senegalese Households

Deep-fat frying performed at high temperatures under atmospheric pressure is a common method of preparing dishes in Senegalese culinary practices. This operation can lead to deterioration of physical, chemical, nutritional and sensory properties of oil, which affects its frying performance. It also results in the production of volatile products such as aldehydes and non volatile fraction which remains in the frying medium. Some of these remaining products have been implicated in producing adverse health effects. Highly oxidized oils may also produce polyaromatic hydrocarbons, which have carcinogenic effect. This work was intended to evaluate the effect of frying on chemical properties of edible vegetable oils. Frying process was applied to meat, fish and potatoes in Senegalese culinary conditions. Ten (10) oil samples, each of three different brands, were purchased from wholesalers and retailers in different neighborhoods of Dakar. The samples were subjected to frying at 220°C for 40 min and then oils were withdrawn in amber bottles samples of which were taken for analysis. Acid value, peroxide value and total polar components were used to evaluate the quality of these oils after initial determination of the iodine value and the moisture and volatile matter content. Acid value increased after 40 min of frying and values ranged from 0.62 to 1.08 mg/kg after frying fish, while those for meat and potatoes ranged from 0.39 to 0.73 and 0.37 to 0.51 mg/kg, respectively. Peroxide value increased slightly for peanut oil (A) and sharply for peanut oil (B) and sunflower oil (C). Frying fish led to high values of total polar components whereas those obtained after frying meat and potatoes during 40 min did not exceed 15.27% except for peanut oil (A). Therefore, frying affects chemical parameter values of edible vegetable oils, which increase at a level depending on the product to be fried. A sharp Total Polar components increase was obtained after frying fish using the three types of oil with values exceeding, sometimes, the maximum level set by the Codex Alimentarius Commission. This latter chemical parameter is considered a good indicator of overall quality of frying oil. Thus in Senegalese culinary practices where frying oil is often reused in families with low-income, such a situation may lead to significant sanitary risks. In view of these results, investigations need to be extended to other types of oil marketed in Senegal.Keywords: edible-oils, quality, frying, fish, mea

Dynamique de la teneur en carbone et en azote des sols dans les systèmes d’exploitation du Ferlo : cas du CRZ de Dahra

Objectif : Cette étude, réalisée au Centre de Recherches Zootechniques (CRZ) de Dahra situé en Région sylvopastorale du Sénégal, a pour objectif d’apprécier l’évolution de la teneur en carbone, en azote et le stock de carbone du sol dans ses différents systèmes d’exploitation.Méthodologie et résultats : En 2011, des échantillons de sols (à 0-20 cm et 20 – 40 cm) ont été prélevés au niveau des mêmes sites que ceux qui ont fait l’objet d’analyse de sols en 1962, afin de déterminer la teneur en carbone et azote du sol. Le nombre d’échantillons est fonction de la superficie des différents types de sols rencontrés. L’utilisation de la cartographie nous a permis de déterminer le nombre d’échantillon prélevé sur chaque système d’exploitation. Au niveau du CRZ de Dahra, l’analyse des paramètres pédologiques (teneur en carbone, en azote et rapport C/N) de l’horizon 0-20 cm, n’a pas révélé de différence significative entre 1962 et 2011. Par contre, dans l’horizon 20-40 cm, seule la teneur en azote présente une hausse significative entre ces deux périodes. S’agissant des systèmes d’exploitation du CRZ de Dahra, l’analyse de la teneur en carbone, en azote et du rapport C/N de l’horizon 0-20 cm, n’a pas révélé de différence significative aussi bien pour l’année 1962 que celle de 2011. Au niveau de l’horizon 20-40 cm, parmi les paramètres étudiés, seul la teneur en carbone de 1962 présentait une différence significative (au seuil de 5%) entre les systèmes de cultures et les pâturages. Le stock de carbone du centre est en moyenne de 0,08±0,03 et 0,06±0,02 t/ha respectivement pour les horizons 0-20 et 20-40 cm. Celui-ci est plus important au niveau des gommiers et plus faibles dans les systèmes de culture et les pâturages.Conclusion et application des résultats : Cette étude a permis de montrer qu’au niveau du CRZ de Dahra à vocation essentiellement pastorale, le carbone et l’azote du sol, présente une certaine stabilité dans les différents systèmes d’exploitation. Toutefois, les gommiers présentent les teneurs en carbone et en azote du sol les plus importantes. Ces résultats peuvent servir de données d’entrée aux modèles de prévision de la séquestration du carbone et de l’azote du sol des écosystèmes sahéliens pastoraux, être valorisés en aménagement pastoral et agro-sylvopastoral en vue d’une meilleure préservation de l’environnement et de la gestion de la fertilité du sol.Mots clés : carbone, l'azote, le contenu, les sol

Permeable reactive barriers for acid mine drainage treatment : a review

Contaminated water flowing from abandoned mines is one of the most significant contributors to water pollution. Acid mine drainage (AMD) can have severe impacts on aquatic resources, can stunt terrestrial plant growth and harm wetlands, contaminate groundwater, raise water treatment costs, and damage concrete and metal structures. Permeable reactive barriers (PRBs) are one of the passive treatment technologies widely accepted for sustainable in situ remediation of contaminated groundwater and may be used in the management of localised seepage plumes from mine residues that contaminate shallow groundwater. These barriers provide chemical interactions with AMD as the polluted water flows through it. The ability of PRBs to remediate contaminants is dependent on the type of reactive material used. Some of the reactive media remove contaminants through physical contact while others work by altering the biogeochemical processes in the treatment zone, thus providing conditions conducive for contaminant immobilization or (bio) degradation. A variety of materials has been employed to remove contaminants including heavy metals, chlorinated solvents, aromatic hydrocarbons, and pesticides. This paper gives an overview of the PRB technology, which includes the advantages and limitations of the PRB, the types of reactive materials used, laboratory treatability tests used to evaluate suitable reactive materials and to aid in the designing and the implementation of the PRB and the installations schemes used in PRB field application

Effets de l’inoculation mycorhizienne sur le sesame (Sesamum indicum L.) en conditions naturelles

La présence des microorganismes symbiotiques dans le sol constitue un atout pour la majorité des cultures. L’inoculation avec des champignons mycorhiziens à arbuscules (CMA) est considérée comme un des moyens biologiques permettant à la culture de résister aux stress biotiques et abiotiques, et d’augmenter la productivité. Mais en conditions naturelles, la combinaison de plusieurs facteurs a une influence majeure dans l’établissement de la mycorhization. L’inoculation du sésame (Sesamum indicum L.) avec deux souches de Glomus est expérimentée en milieu naturel, dans un dispositif en split-plot avec quatre répétitions. Cetteinoculation mycorhizienne en milieu naturel a produit les effets suivants : le taux de mycorhization des plants inoculés reste bas ; l’inoculation n’a pas eu un effet significatif sur le rendement en graines, le nombre decapsules et la biomasse totale comparativement aux plants témoins naturellement infectés. Cela montre que, la mycorhization naturelle a eu une efficacité comparable à celle des souches inoculées sur le sesame. On peut déduire que les sols de cette zone de Bambey contiendraient des souches de champignons mycorhiziens à arbuscules (CMA) indigènes aussi efficaces que des souches sélectionnées.© 2013 International Formulae Group. All rights reserved.Mots clés : Mycorhization naturelle, Glomus mosseae, Glomus fasciculatum, sésame, productivité