Obligatory service is not service

Service is not just helping another person in an hour of need, but rather it is helping another in any hour, ignoreing our own selfish gains from taking up the act. In this sense, therefore, service cannot by meaning, by compulsory

The Clash of Civilizations: Classical & Modern Definitions of Heroism in Vergil’s Aeneid

To conceive of Aeneas as anything but a hero is to perceive of the clash of two civilizations; the mind of the modern reader and that of a Roman epic poet ultimately require some form of reconciliation. The vehicle for this understanding is the consideration of historical and social contexts. These are useful not only in decoding ancient literature, but also in a world that is swiftly becoming increasingly more global. In the face of this trend, it is necessary to equip ourselves with the tools needed to interact with one another with mutual understanding—the same tools used everyday for something as simple as reading

Simulation par le modèle AgriFlux du devenir de l'atrazine et du dééthylatrazine dans un sol du Québec sous mais sucré

Les outils mathématiques sont de plus en plus utilisés pour simuler la contamination d'origine agricole des eaux souterraines. Le modèle AgriFlux permet, à l'aide du module PestiFlux, de simuler les processus responsables du devenir des pesticides dans le sol: ruissellement, volatilisation, adsorption/désorption rapide, adsorption/désorption lente, complexation par la matière organique dissoute, biodégradation en sous-produits, hydrolyse, drainage et lessivage. AgriFlux est utilisé pour simuler le devenir de l'atrazine et du dééthylatrazine sur une parcelle expérimentale de la région de Québec (Québec, Canada) cultivée en maïs sucré (Zea mays, L.) traité à l'atrazine. Des prélèvements d'eau interstitielle ont été réalisés (1986-1990) à l'aide de lysimètres avec succion (0,5 et 1,0 m de profondeur) et analysés pour leur contenu en atrazine et dééthylatrazine. De manière générale, AgriFlux reproduit bien l'évolution des concentrations mesurées, dans le temps et dans le profil de sol (r=0,76). Certains pics de concentrations observés sur le terrain ne sont toutefois pas représentés ou sont décalés dans le temps, ce qui pourrait être attribué à une sous-estimation de la variabilité spatiale des paramètres. Le rapport dééthylatrazine/atrazine est relativement bien simulé en 1988 à 0,5 m, mais est moins représentatif pour les autres données, ce qui pourrait être dû à une certaine imprécision dans la simulation de la biodégradation. Une analyse de sensibilité du modèle aux variations de différents paramètres a montré que le paramètre le plus influent dans les conditions testées est la constante de biodégradation. Les résultats obtenus montrent la pertinence d'AgriFlux (PestiFlux) dans la simulation du devenir des pesticides dans le sol et donc des risques de contamination des eaux souterraines en région agricole.Groundwater and surface water contamination by agricultural practices has become an increasingly preoccupying problem. Mathematical models are valuable tools to help prevent this type of pollution from non-point sources. AgriFlux is a mechanistic, stochastic model simulating the fate of agricultural contaminants in the unsaturated zone at the scale of the agricultural field. AgriFlux, through the PestiFlux module, now simulates pesticide transformations in the soil from their application to the field until their leaching with percolating water. The processes represented include volatilization, complexation by the soluble organic matter, instantaneous adsorption and desorption, slow adsorption and desorption to less available sites, biodegradation to by-products and hydrolysis to non-toxic compounds. The pesticide freely dissolved in solution or complexed with soluble organic matter can be mobilized with runoff, drainage and leaching waterAn application of PestiFlux to an experimental field near Quebec City (Quebec, Canada) is presented. The soil is a well-drained loamy sand cropped from 1986 to 1990 with sweet corn (Zea Mays, L.) receiving atrazine treatments (1.6 to 1.8 kg.ha-1 of active ingredient). Interstitial water was sampled using 12 suction lysimeters located at both the 0.5 and 1.0 m depths in the soil. All stations were sampled monthly in 1986 and 1987 and the collected water was analyzed for atrazine alone. In 1988, the sampling (every two weeks) was limited to the lysimeters which had previously shown the highest pesticide concentrations (two lysimeters at 0.5 m and one lysimeter at 1.0 m). The interstitial water was analyzed for atrazine and deethylatrazine. There was no sampling in 1989. In 1990, all stations were sampled on a weekly basis and a composite water sample obtained for each depth was analyzed for both compounds. Most of the pesticide-related parameters required to run PestiFlux were deduced from the literature, with the exception of the biodegradation rate coefficient which was estimated from field monitoring of atrazine. The parameters required to simulate water fluxes and plant uptake were the same as those used in a previous application of AgriFlux to the same experimental field for the simulation of nitrate fluxes (LAROCQUE and BANTON, 1995).Results show that PestiFlux generally represents well the measured atrazine and deethylatrazine concentrations in the interstitial water at 0.5 and 1.0 m. A linear regression using all measured and simulated concentrations indiscriminately gives a correlation coefficient of 0.76 when using the logarithm of concentrations. The temporal evolution of the pesticide concentrations is relatively well simulated, especially on the long term with an adequate representation of the increase in pesticide concentrations in the soil profile at 1.0 m. This increase is probably due to the fallow existing in 1985 which would have favored leaching of adsorbed pesticide below the soil profile, leaving only low residual pesticide concentrations. Over one growing season, the transport of atrazine and deethylatrazine is well represented by the model, although some peak concentrations are delayed or attenuated. This result could be due to an underestimation of the spatial variability of the different parameters. It is possible that the coefficient of variation of 10% adopted may not represent adequately the spatial variation of some parameters. Nevertheless, most measured concentrations of both compounds are within the mean simulated concentrations and included between two standard deviations. For 1988, most of the measured concentrations are located near the upper limit of the envelope curve which is consistent with the fact that the sampled lysimeters were those yielding the highest concentrations. The simulated concentrations show a generally good representation of the relative atrazine and deethylatrazine concentrations. The ratio of the mean deethylatrazine to atrazine concentrations provides a closer look at the adequacy between the simulated concentrations of both compounds. A comparison between the measured and the simulated ratios shows a good adequacy at 0.5 m in 1988 and both over- and under-estimation of the ratio for the other available data. This is probably due to an imprecision in the simulation of biodegradation rates during some periods. All the parameters used in the simulation have an important uncertainty, due to the significant spatial variation of the parameters in the field and to the imprecise knowledge of some pesticide characteristics. In order to identify the parameters which have the most important influence on the results, an analysis of the sensitivity of the cumulated leaching mass of both compounds at 1.0 m to variations of the different input parameters was performed. The results show that the biodegradation rate has the greatest influence on the results. This is probably due to the importance of this process in the simulated situation. This result confirms the importance of an adequate quantification of this parameter and of its spatial variation. PestiFlux offers a comprehensive representation of pesticide transformations in the soil and is easy to use. As a module of AgriFlux, it has the advantage of being integrated into a well-tested and reliable modeling environment. The presented simulation results show that, apart from some limits due to the quantification of some of the parameters, PestiFlux is a useful and comprehensive tool for estimating potential groundwater pollution by pesticides

Milk Marketing Order Winners and Losers

Determining the impacts on consumers of government policies affecting the demand for food products requires a theoretically consistent micro-level demand model. We estimate a system of demands for weekly city-level dairy product purchases by nonlinear three stage least squares to account for joint determination between quantities and prices. We analyze the distributional effects of federal milk marketing orders, and find results that vary substantially across demographic groups. Families with young children suffer, while wealthier childless couples benefit. We also find that households with lower incomes bear a greater regulatory burden due to marketing orders than those with higher income levels.Milk, marketing orders, dairy industry regulation

Milk Marketing Order Winners and Losers

Do milk marketing orders affect various demographic groups differently? To answer this question, we use supermarket scanner data to estimate an incomplete demand system for dairy products. Based on these estimates, we simulate substitution effects among dairy products and the welfare impacts of price changes resulting from changes in milk marketing orders for various consumer groups. While we find little difference in own- and cross-price substitution elasticities of demand, the welfare effects of price changes vary substantially across demographic groups, with some losing and others winning from this government program. Families with young children suffer from marketing orders, while wealthier childless couples benefit. Additionally, we find that households with lower incomes pay a larger percentage of their income due to marketing orders than those with higher income levels.Consumer/Household Economics,

Milk Marketing Orders: Who Wins and Who Loses?

Livestock Production/Industries, Marketing, Q13, Q18,

Adsorption du pentachlorophenol sur divers matériaux : Influence de co-adsorbats organiques (Substances humiques et lindane)

Nous avons réalisé, pour de faibles concentrations, l'étude de l'adsoprtion d'un pesticide le pentachlorophénol, sur plusieurs matériaux adsorbants : le charbon actif, la kaolinite et la bentone. Les résultats montrent que l'adsorption du pentachlorophénol sur la kaolinite reste négligeable tandis que la bentone SD-3 (argile traitée) permet d'obtenir des résultats intéressants avec toutefois une capacité maximale d'adsorption 10 à 100 fois plus faible que celle du charbon actif. Le charbon actif reste le meilleur matériau adsorbant pour le pentachlorophénol. La solubilité de ce composé étant très variable en fonction du pH du milieu on constate que l'adsorption du pentachlorophénol-pentachlorophénate (5 mg.l-1) diminue pour des valeurs de pH supérieures au pKa du couple acide-base que nous avons déterminé expérimentalement, égal à 5,9 ± 0,1. L'adsorption du pentachlorophénol n'est pas affectée par la présence d'acides humiques (obtenus à partir de substances commerciales) utilisés comme coadsorbats (10 mg.l-1) alors que les acides fulviques (20 mg.l-1) extraits de sols semblent provoquer une promotion de l'adsorption. On observe d'autre part que le pentachlorophénol n'affecte pas l'adsorption des acides humiques mais augmente légèrement celle des acides fulviques. Ces remarques suggèrent la possible formation d'un complexe acides fulviques-pentachlorophénol. Lorsqu'on utilise le lindane, pesticide hydrophobe comme coadsorbat (165 mg.l-1), on observe encore d'une façon systématique pour tous les nombreux essais une légère promotion de l'adsorption.Adsorption studies for the removal of the pesticide pentachlorophenol found in a number of water supplies (BELAMIE and GIROUD, 1986) were carried out using various materials including kaolinite, bentone SD-3 and powdered activated carbon (WEBER and GOULD, 1966; WEBER and JODELHAH, 1985). It was found that adsorption on kaolinite was negligible, whereas bentone SD-3 presented and adsorption efficiency from 10 to 100-fold less than equivalent quantities of powdered activated carbon (LOTSE et al., 1968; SHAROM et al., 1980). The effect of the pH on the removal of pentachlorophenol by activated carbon was studied. The removal efficiency of pentachlorophenol by activated carbon is better in acidic media. A clear dependence of adsorption on the pH appeared to be the result of a marked variation of the pesticide solubility as a function of the pH (fig. 3). Adsorption of pentachlorophenol/phenate (5mg.l-1) diminishes markedly at pH values above the pKa of this weak acid (that we found equal to 5,9 ± 0,1) when the pentachlorophenol exists almost entirely in ionic form in aqueous solution, and is enhanced at low pH when the percentage of molecular species (whose concentration can be determined from pKa value) becomes significant (WARD and GETZEN, 1970). These remarks and the adsorptive capacities (163 mg.g-1= 0,6 mmol.g-1 at pH = 5,2 and 79 mg.g-1 0,3 mmol.g-1 at pH =12,7), suggest a П-П interaction between pentachlorophenol and activated carbon which seems to be confirmed by the results with bentone SD-3 (tables 1 to 4), and the values of the electrokinetic potential of these materials. This study emphasizes the effect of organic coadsorbates (e.g., dissolved humic substances and the pesticide lindane) on the adsorption capacity of activated carbon for pentachlorophenol. Two different natural organic matters were studied as coadsorbates : purified humic acids from a commercial source (at 10 mg.l-1) and fulvic acids extracted from a top soil horizon (et 20 mg.l-1) (SCHNITZER and SKINNER, 1963; THURMAN and MALCOLM, 1981). Pentachlorophenol adsorption was not affected by humic acids, whereas an increase of adsorption seemed to be observed in the presence of fulvic acids (fig. 6). Pentachlorophenol does not affect the adsorption of humic acids, but improves slightly the removal of fulvic acids. This suggests an association between the two kinds of organic compounds (WERSNAW et al., 1969; KHAN, 1972; OGNER and SCHNITZER, 1970), the resulting « complex », fulvic acids/pentachlorophenol, being more adsorbed than the compounds themselves. The coadsorbate lindane (0,65 mg.l-1) which is easily adsorbed by activated carton (GOMELLA and BELLE, 1975...) seemed also to Improve slightly the removal efficiency of pentachlorophenol by activated carton (fig. 7)

Fractionnement et caractérisation de la matière organique des lixiviats de décharges d'ordures ménagères

Les lixiviats de décharge constituent une source de nuisance qui vient s'ajouter aux nombreux problèmes de contamination du milieu environnant s'ils ne sont pas traités avant leur rejet. La matière organique, principale composante de ces effluents, doit retenir une grande attention dans la mesure où il est difficile d'éviter la propagation et la diffusion de cette pollution dans les sols et vers les nappes phréatiques. Cette étude vise à fractionner et à caractériser la matière organique présente dans des lixiviats de décharges d'ordures ménagères afin de prévoir et d'orienter le choix des traitements les plus adaptés compte tenu de leur biodégradabilité.La méthode de fractionnement utilisée comprend une adsorption spécifique sur résines macroporeuses Amberlite XAD (combinaison de XAD-7 et XAD-4) pour séparer les composés hydrophobes et hydrophiles qui sont ensuite extraits à la soude (composés acides) et au dichlorométhane (composés neutres). Le fractionnement de la matière organique par filtration sur résines XAD-7 et XAD-4, après une première étape de précipitation en milieu acide (pH=1), a permis de répartir l'ensemble des composés organiques du lixiviat dans six fractions de spécificités différentes fonction de la taille et/ou du caractère hydrophile ou hydrophobe des molécules. Les résultats montrent que ce protocole expérimental permet d'extraire au moins 98 % de la matière organique totale (pourcentage relatif aux teneurs de la demande chimique en oxygène ou DCO), dont la plus grande proportion est constituée des substances humiques (76 % à 90 % en DCO). Diverses méthodes analytiques ont été proposées en vue de caractériser les fractions isolées telles que l'analyse élémentaire, la spectrophotométrie infrarouge, la résonanoe magnétique nucléaire C13 (RMN Cl3) et la chromatographie CG/FID et CG/SM.Landfill leachates represent an obvious source of pollution for the environment and many studies have attempted to analyze organic pollutants found in leachates. A number of methods have been described in the literature for the isolation and concentration of dissolved organic matter from landfill leachate samples. Membrane ultrafiltration, gel permeation and high performance liquid chromatography are commonly used because these techniques can be easily adapted to separate soluble organic substances from large volumes of leachate. The objective of this study was to fractionate and characterize dissolved organic matter found in leachates collected from sanitary landfills.The discharges are defined with regard to the geological context from which they are situated and the nature of the waste. The discharges are classified in three categories, based upon the value of the permeability coefficient K, the substratum and its continuity.- class 1; impermeable site (K 10-[sup]6 ms-¹). The studied leachates come from landfill of class 2:- Crézin (Haute-Vienne) of compacted type: it was used for household rubbish and assimilated ordinary wastes. - Foussais-Payre (Vendée): leachate coming from the fermentation area of a composting plant and from the compost refuse. Fractionation of dissolved organic matter was applied on three leachates samples. The first sample was the raw leachate collected from the Crézin landfill and the two others came from Foussais-Payre (a raw sample and a sample treated in an aerated lagoon for 52 days). Because of the wide variety of organic compounds that can be found in such leachates, we classified and isolated the different groups of organic constituents using an XAD resin adsorption procedure. The experimental method consisted of acidifying samples to pH 1 to isolate the first fraction (fig. 1) and then treating the remaining supernatant with XAD-7 and XAD-4 resins. The adsorption on XAD resins allowed the isolation of the other organic fractions (figs. 2 to 6). Various analytical techniques were applied to characterize the isolated fractions such as elementary analysis infrared spectroscopy, ¹3C nuclear magnetic resonance (¹3C CP/MAS NMR), gas chromatography (GC/FID), and gas chromatography coupled to mass spectrometry (GC/MS). Results showed that more then 90% of the total organic carbon (TOC) in leachates can he recovered by the isolation procedure. Most of the isolated compounds corresponded to humic substances (76% to 90% of the chemical oxygen demand). Hydrophobic and hydrophilic neutral compounds were found only in small concentrations