Information Sharing in Professional Associations: the case of the Ethiopian Journal of Health Development in Strengthening the Ethiopian Public Health Association

No Abstrac

Influence de l'origine et de la nature des substances humiques sur l'adsorption de l'atrazine sur charbon actif en poudre

Les essais d'adsorption sur charbon actif en poudre, de sept acides humiques (H) ou fulviques (F) et pour trois pH (5,6 ; 7,0 ; 8,8) marquent que ces acides ont un comportement différent suivant leur origine.Lorsque le pH de la suspension de charbon est basique, l'adsorption des différentes fractions humiques diminue, ce qui est en relation avec l'augmentation de leur solubilité. Pour un même pH de la suspension, les acides humiques et fulviques d'origine aqueuse s'adsorbent mieux que ceux d'origine commerciale ou que ceux extraits de sol.La capacité maximale d'adsorption de l'atrazine sur charbon actif en poudre : 260 mg.g-1 (Langmuir), est plus fortement diminuée en présence d'acides fulviques que d'acides humiques d'une part, et plus inhibée (jusqu'à 40 %) par les acides fulviques extraits d'eau (F1, F2) que par ceux extraits de sol (F3) d'autre part.Par contre, les acides humiques provenant de substances commerciales (H4, H5) influencent moins l'adsorption de l'atrazine.L'ensemble des essais montre que l'origine et la nature des substances humiques joue un rôle prépondérant sur l'adsorption de l'atrazine sur charbon actif, le pH ayant une influence limitée.Enfin l'étude de l'influence de l'atrazine sur l'adsorption des substances humiques sur charbon actif en poudre indique également une différence de comportement entre les acides fulviques, pour lesquels on note peu de variation, et les acides humiques, pour lesquels on note à la fois une promotion de l'adsorption et une meilleure affinité d'adsorption sur le charbon actif en poudre en présence d'atrazine.Ce travail met en évidence l'importance du choix des substances humiques pour des essais d'évaluation des interactions substances humiques - pesticides lors de l'adsorption sur charbon actif en poudre.Though the subject was copiously and oldly studied, this work is bringing a new contribution to the study of the influence of the origin and the nature upon their properties and in particular with atrazine, the more used herbicide these fast years.In order to study this influence of the origin and nature of various humic substances upon the removal of atrazine by adsorption onto powdered activated carbon (PAC), humic substances were obtained from different sources :- Natural aquatic fulvic (F1) and humic (H1) acids isolated from Beaune Lake (Limoges, France).- Natural aquatic fulvic (F2) and humic (H2) acids extracted from hydroxyde sludges of the water treatment plant of La Bastide (Limoges, France).- Soil fulvic acids (F3) extracted from a canadian top soil horizon.- Commercial humic acids (Aldrich. H4 and Jansen H5) obtained from commercial sodium humates.The results of adsorption test of humic acids, fulvic acids and atrazine (alone or together) onto powdered activated carbon (PAC) at three different pH (5,6 ; 7,0 ; 8,8) were expressed by Freundlich's and Langmuir’s models and permitted us to note that :- According to the increasing of water solubility of humic substances with basic pH, their adsorption was better in acidic medium.- Natural aquatic humic substances (H1, H2, F1, F2) were more adsorbed onto PAC than humic substances tram soil (H3) or commercial origines (H4, H5).- Atrazine adsorption capacity was 260 mg.g-1 according to Langmuir's model.- Atrazine adsorption decreased with F1 for all pH ; the same result was also observed with the other natural aquatic humic substances.- Commercial humic acids didn’t importantly affect atrazine adsorption. These differences appeared to be derived from the nature and the origin of fulvic and humic acids. The rose of atrazine on the humic substances adsorption showed a difference between humic and fulvic acids whose adsorption was not influenced by atrazine even humic acids only presented an increasing of adsorption.All these results showed the importance of the selection of humic substances to evaluate the interaction SH-Pesticides during adsorption onto PAC and let us think to a competitive adsorption between fulvic acids and atrazine onto PAC

Influence du dodécylsulfate de sodium sur l'adsorption des acides humiques sur charbon actif en poudre

L'objectif de ce travail est d'étudier l'influence d'un tensioactif anionique, le dodécylsulfate de sodium (DSS) sur l'adsorption d'acides humiques (AH), sur le charbon actif en poudre (CAP).L'adsorption sur CAP, en fonction du temps, des AH seuls, puis du DSS seul, a été effectuée en réacteur discontinu, à différents pH (7,0 et 10,5). Les mêmes expériences ont été réalisées avec le mélange des deux composés et l'on a pu constater une inhibition réciproque de leur adsorption, moins importante à pH basique (10,5).L'influence de l'ordre d'introduction des coadsorbats, sur l'adsorption de chacun d'eux, a permis de montrer que l'inhibition de l'adsorption des AH sur CAP par le DSS est encore plus importante lorsque les AH sont ajoutés sur une suspension DSS-CAP déjà en équilibre. Aucune désorption du DSS n'a pu être mise en évidence après 24 heures. Ces résultats pourraient permettre de conclure à une adsorption « compétitive » des AH et du DSS sur les mêmes sites superficiels du charbon actif.Ce travail permet de préciser les phénomènes d'adsorption pouvant intervenir entre divers micropolluants susceptibles de s'adsorber simultanément soit sur des sédiments naturels, soit sur charbon actif lors du traitement des eaux naturelles.The removal of humic acids (HA) from natural waters is a very old yet modern problem : humic substances are at the origin of the coloration of water but also, they give off nocive trihalomethanes during chlorination.Humic acids are also known to be a metal micropollutant vector and their behavior is not well defined when there is coadsorption.The purpose of this work was to study the effect of an anionic surfactant, sodium dodecyl sulphate (SDS), on the adsorption on powdered activated carbon (PAC) of humic substances from a commercial source, as a function of the pH (7.0 or 10.5), as well as the effect of the order of introduction of the coadsorbate.Results (fig. 1 to 3 and fig. 6) showed an inhibition of the adsorption for both HA and SDS in the presence of the coadsorbate. The inhibition was more significant for a pH = 7.0.Results of the influence of the order of introduction of the coadsorbate on the adsorption (fig. 4 and 5) showed a more significant inhibition of HA adsorption when HA were introduced into the equilibrium suspension SDS-PAC (the contact lime was 24 hours).Table 1 gives parameter values of the Langmuir equation for the adsorption on PAC of HA atone or with SDS.All these results suggest that a competition on the same sites occurs during the adsorption on PAC of HA and SDS

Étude de l'adsorption de l'atrazine sur le charbon actif en poudre en présence de tensioactifs

Les tensioactifs, adjuvants participant à la formulation des pesticides peuvent se trouver en compétition avec ces derniers lors de l'adsorption sur charbon actif en poudre (CAP) utilisé au cours du traitement de potabilisation des eaux. L'adsorption de l'atrazine, qui reste l'un des produits phytosanitaires le plus souvent détecté dans les eaux de surface malgré les réglementations sur son utilisation, a été étudiée en présence de trois tensioactifs afin de déterminer l'influence de ces derniers; il a été choisi un tensioactif anionique (DSS), cationique (BHTA), et un non ionique (DE6). Les résultats ont montré que quelle que soit la nature du tensioactif, celui-ci diminue toujours l'adsorption de l'atrazine pour des pH variant de 3,5 à 10 ce qui a pour conséquence une diminution à la fois de la constante de vitesse (Adams et Bohart) et de la capacité d'adsorption (Langmuir). L'étude de l'influence de l'ordre d'introduction des différents éléments participant à l'adsorption (CAP, atrazine, tensioactif) a montré que la fixation préalable de DSS anionique, favorisée en milieu acide, inhibe davantage l'élimination de l'atrazine. L'application des modèles d'adsorption compétitive et non compétitive de Langmuir n'a pas permis de définir avec certitude la nature des interactions entre l'herbicide et les différents tensioactifs.Atrazine, in spite of the restrictions concerning its use, remains one of the most prevalent pesticides in natural surface waters. If a sudden pollution incident occurs, powdered activated carbon (PAC) is used during the flocculation step of water treatment; under such circumstances, atrazine might be in adsorption competition with surfactants included in commercial formulations. The aim of this study was thus to determine the influence of three surfactants [anionic (sodium dodecylsulphate, SDS), cationic (hexadecyl-trimethylammonium bromide, HTAB) and nonionic (2-dodecyloxy-pentaethanoxy)-ethanol, DE6)] on atrazine adsorption onto PAC. At pH 5.5, adsorption onto PAC of atrazine alone was estimated to be 230 mg. g-¹; it was inhibited whatever the nature of the surfactant (cationic anionic or nonionic: figs. 2, 3 and 4). The adsorption capacities (Langmuir) and the kinetic constants (Adams & Bohart) decreased in the presence of the surfactants (table 4) and this diminution was most important for HTAB (fig. 5), perhaps the consequence of a steric effect.The adsorption onto PAC of the molecular form of atrazine (pK=1.68) was not affected by the pH variations. However, when the pH was increased (3.5 to 10) in the presence of SDS, adsorption onto PAC of the anionic surfactant decreased and atrazine adsorption increased (fig. 9). In contrast, for the same experimental conditions but with the cationic surfactant HTAB, adsorption of the surfactant increased over the pH range 3.5 to 10 and the relative adsorption of atrazine diminished (fig. 9). The nonionic surfactant DE6 had no influence.A study of the introduction order of the different components (atrazine, SDS surfactant and PAC) showed the same final equilibrium distribution of atrazine was obtained (fig. 10), regardless of the order of introduction. A similar result was obtained for the adsorption of SDS (fig. 11).For all these cases, the Langmuir equation yielded the adsorption capacity for atrazine and the equilibrium constant. However, competitive and noncompetitive adsorption models (table 1) were unsuccessful in predicting the nature of the interactions between atrazine and the surfactants (table 5)

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)

Indications, Challenges, and Characteristics of Successful Implementation of Perioperative Registries in Low Resource Settings: : A Systematic Review

Acknowledgements The authors would like to thank Ms. Dilshaad Brey for her assistance during the database searches and in organising the search results. UCT Division of Global Surgery and Prof Maswime’s SA MRC Mid-career Scientist Award for partially funding this study. Funding Open access funding provided by University of Cape Town. This study was partially funded by the University of Cape Town Department of Global Surgery, and the Network for Perioperative and Critical Care (N4PCc).Peer reviewedPublisher PD

Capacity Gaps in Post Disaster Waste Management: Case Study in Sri Lanka

Disaster waste is one of the major consequences aftermath of any disaster, impacts on public and environment, rescue and emergency services, provision of lifeline support and socio-economic recovery of affected areas. Thus, management of wastes created by disasters has become an increasingly important issue to be addressed in responding to a disaster. This chapter intends to present the prevailing gaps in disaster waste management and approaches to minimize the impacts on disaster management at developing countries with special emphasis to Sri Lankan context. Findings revealed that, unavailability of single point responsibility and provisions for disaster waste in existing policies and capacity constraints of the prevailing peace time solid waste management practices as major capacity gaps. Establishment of a regulatory body and enforceable rules and regulations with necessary levels of capacities were identified with seven areas for capacity building for post disaster waste management. The research enabled to attain sustainable post disaster waste management for future resilience

Внутригодовые (сезонные) изменения общего содержания биогенных элементов и кислорода в различных районах Севастопольской бухты

Для каждого месяца в период май 1998 г. – май 1999 г. рассчитано абсолютное содержание биогенных элементов и кислорода в пяти различных районах Севастопольской бухты и для всей бухты в целом. Показано, что наиболее чистый (возле входа в бухту) и наиболее грязный (Южная бухта) районы отличаются по динамике накопления и расходования биогенных элементов. Максимальный запас неорганических форм азота, фосфора, и кремнекислоты во всех районах Севастопольской бухты, за исключением района Инкерманской бухты, приходится на январь.Total content of biogenic elements and oxygen in five different areas of the Sevastopol Bay and for the whole bay in general is estimated for each month starting from May, 1998 up to May, 1999. It is shown that the purest (near the bay entrance) and the dirtiest (the Southern Bay) areas are distinguished for dynamics of biogenic elements accumulation and expense. Maximum storage of inorganic forms of nitrogen, phosphorus and silicic acid in all the areas of the Sevastopol Bay, excepting the Inkerman Bay area, falls on January

Evaluation and application of multi-source satellite rainfall product CHIRPS to assess spatio-temporal rainfall variability on data-sparse Western margins of Ethiopian Highlands

The spatio-temporal characteristic of rainfall in the Beles Basin of Ethiopia is poorly understood, mainly due to lack of data. With recent advances in remote sensing, satellite derived rainfall products have become alternative sources of rainfall data for such poorly gauged areas. The objectives of this study were: (i) to evaluate a multi-source rainfall product (Climate Hazards Group Infrared Precipitation with Stations: CHIRPS) for the Beles Basin using gauge measurements and (ii) to assess the spatial and temporal variability of rainfall across the basin using validated CHIRPS data for the period 1981-2017. Categorical and continuous validation statistics were used to evaluate the performance, and time-space variability of rainfall was analyzed using GIS operations and statistical methods. Results showed a slight overestimation of rainfall occurrence by CHIRPS for the lowland region and underestimation for the highland region. CHIRPS underestimated the proportion of light daily rainfall events and overestimated the proportion of high intensity daily rainfall events. CHIRPS rainfall amount estimates were better in highland regions than in lowland regions, and became more accurate as the duration of the integration time increases from days to months. The annual spatio-temporal analysis result using CHIRPS revealed: a mean annual rainfall of the basin is 1490 mm (1050-2090 mm), a 50 mm increase of mean annual rainfall per 100 m elevation rise, periodical and persistent drought occurrence every 8 to 10 years, a significant increasing trend of rainfall (similar to 5 mm year(-1)), high rainfall variability observed at the lowland and drier parts of the basin and high coefficient of variation of monthly rainfall in March and April (revealing occurrence of bimodal rainfall characteristics). This study shows that the performance of CHIRPS product can vary spatially within a small basin level, and CHIRPS can help for better decision making in poorly gauged areas by giving an option to understand the space-time variability of rainfall characteristics