Influence de la matière organique et inorganiquede l'eau sur l'élimination des pesticides par nanofiltration

Ce travail explore les performances de deux types de membranes de nanofiltration (Desal DK et NF200) dans l'élimination dans les eaux de certains pesticides (l'atrazine et son métabolite la déséthylatrazine (DEA), la simazine, la cyanazine, l'isoproturon et le diuron) et évalue l'influence de la présence de matière organique ou inorganique dans la matrice d'eau sur l'efficacité de ce traitement.Des eaux synthétiques, composées à partir d'eau distillée à laquelle a été ajoutée de la matière organique (acides humiques) ou inorganique (CaCl2 ou CaSO4), ont été traitées sur un pilote de nanofiltration durant 96 heures. Les taux rétention en pesticides et ceux de leur adsorption sur les membranes ont été calculés et comparés aux résultats obtenus sur une matrice d'eau distillée pure. Une influence du type de membrane et de la présence de la matière humique sur le taux d'abattement de certains pesticides a été constatée. L'influence de la matière inorganique est pratiquement insignifiante.The intensive use of pesticides in agriculture has resulted in the contamination of groundwater and surface waters. The removal of these organic pollutants by the usual methods such as adsorption by activated carbon (in powdered or granular form) or oxidation by ozone have some disadvantages. Recently, the removal of organic pollutants by membrane retention (reverse osmosis, ultrafiltration and nanofiltration) has become increasingly popular and due to its low cost, nanofiltration has become an interesting option.This study examined the efficiency of two different nanofiltration membranes (Desal DK and NF200) in the removal of some pesticides (atrazine and its metabolite desethylatrazine (DEA), simazine, cyanazine, isoproturon and diuron) from water and, in addition, investigated the influence that organic and inorganic matter may have on the efficiency of this removal. Synthetic waters were made from distilled water and organic matter (humic acids) or inorganic matter (CaCl2 or CaSO4) was added, as well as 1 µg/l of each pesticide. The samples were then filtered by a nanofiltration pilot for 96 hours. Samples of the feed, permeate and the retentate were taken after 4, 24, 48, 72 and 96 h. The samples were replaced with equivalent volumes of the original solution in the feed tank. The different samples were analysed by an on-line SPE / HPLC system. The different concentrations obtained allowed the determination of the proportion of the pesticides that adsorbed to the membrane.The removal efficiency of pesticides from pure distilled water differed according to the membrane. For example, the Desal DK membrane eliminated more than 90% of all the pesticides (with the exception of diuron). In contrast, the NF200 membrane, eliminated more than 75% of all the pesticides (with the exception of diuron). The removal efficiency of Diuron was the lowest by both the membranes: 70 % by Desal DK and 45 % by NF200. The adsorption efficiency of the pesticides was similar for both membranes (between 30 and 40%). In pure water, pesticide removal is a function of both the specific properties of each pesticide (solubility, molecular mass, Stokes diameter, equivalent molar diameter, calculated equivalent diameter and polarity) and the physical characteristics of the membrane (molecular weight cut-off and current load).The influence of inorganic matter on pesticide removal efficiency changed according to the type of membrane. For example, we noted an improvement in removal efficiency with the NF200 membrane from low removal with CaCl2 to high removal with CaSO4 for all pesticides examined including diuron. In contrast, for the Desal DK membrane, very little change was noted (a slight decrease in the removal efficiency of DEA and simazine with CaCl2). Adsorption by the membranes remained stable for all the pesticides tested on the two types of membrane. The improvement in the removal of pesticides by the NF200 membrane was probably linked to pores being blocked by ions at high concentrations. It could be concluded from these results that elimination of pesticides is quantitatively linked to the physical characteristics of the membranes and that inorganic matter only has an effect with wide-pore membranes (NF200 membrane) and, furthermore, it has no influence on the adsorption of the pesticides on the membranes.For water containing organic matter, we have noted an improvement in the removal of certain pesticides with the NF200 membrane when compared to distilled water (except diuron). With the Desal DK membrane, we observed a slight decrease in the removal of DEA, simazine and isoproturon, and a substantial drop for diuron (20 %) with no change for cyanazine and atrazine. Adsorption of the pesticides on the membranes remained unchanged with the NF200 membrane but increased by about 10% on the Desal DK membrane for all molecules. Pesticides, notably triazines, adsorb easily on organic matter by physiosorption (weak links) and by chemisorption (ionic links) to form macromolecules. The steric congestion and the density of these pseudo-complexes is high, which facilitated the elimination of certain pesticides with the (wide-pore) NF200 membrane by accentuating the effects of steric exclusion and electrostsatic repulsion and decreasing adsorption. For the Desal DK membrane, the increased adsorption of the pesticides on the membrane generated a more significant transition of these molecules in the direction of the permeate. This had a negative influence on the removal of some pesticides, depending on their size; the largest molecules underwent the least change. Diuron behaved differently from the other pesticides examined. This molecule did not bind to humic acids and its removal rate did not change with a wide-pore (NF200) membrane. However a greater adsorption of organic matter by the narrower-pore (Desal DK) membrane favored diuron adsorption and, consequently, its diffusion into the permeate. The effect of organic matter and, more specifically, of humic acids on the elimination of pesticides depends not only on the structure of the molecules, but also on the cut-off threshold of the membrane.The two main mechanisms that govern the process of pesticide elimination by NF are repulsion (steric and electrostatic) by the membrane and adsorption on the membrane. This latter phenomenon must be minimized, to reduce the elimination of pesticides by fostering their transition in the direction of the permeate. In addition, removal of the pesticides by NF was favoured by the high-molecular weight organic matter fraction (i.e., humic acids). The influence of the inorganic matter (CaCl2 and CaSO4), for its part, is greater with the wide-pore membrane

Impact of opioid-free analgesia on pain severity and patient satisfaction after discharge from surgery: multispecialty, prospective cohort study in 25 countries

Background: Balancing opioid stewardship and the need for adequate analgesia following discharge after surgery is challenging. This study aimed to compare the outcomes for patients discharged with opioid versus opioid-free analgesia after common surgical procedures.Methods: This international, multicentre, prospective cohort study collected data from patients undergoing common acute and elective general surgical, urological, gynaecological, and orthopaedic procedures. The primary outcomes were patient-reported time in severe pain measured on a numerical analogue scale from 0 to 100% and patient-reported satisfaction with pain relief during the first week following discharge. Data were collected by in-hospital chart review and patient telephone interview 1 week after discharge.Results: The study recruited 4273 patients from 144 centres in 25 countries; 1311 patients (30.7%) were prescribed opioid analgesia at discharge. Patients reported being in severe pain for 10 (i.q.r. 1-30)% of the first week after discharge and rated satisfaction with analgesia as 90 (i.q.r. 80-100) of 100. After adjustment for confounders, opioid analgesia on discharge was independently associated with increased pain severity (risk ratio 1.52, 95% c.i. 1.31 to 1.76; P < 0.001) and re-presentation to healthcare providers owing to side-effects of medication (OR 2.38, 95% c.i. 1.36 to 4.17; P = 0.004), but not with satisfaction with analgesia (beta coefficient 0.92, 95% c.i. -1.52 to 3.36; P = 0.468) compared with opioid-free analgesia. Although opioid prescribing varied greatly between high-income and low- and middle-income countries, patient-reported outcomes did not.Conclusion: Opioid analgesia prescription on surgical discharge is associated with a higher risk of re-presentation owing to side-effects of medication and increased patient-reported pain, but not with changes in patient-reported satisfaction. Opioid-free discharge analgesia should be adopted routinely

Extraction en phase solide de certains herbicides présents dans l'eau

L'extraction en phase solide (SPE) est devenue une alternative très intéressante à l'extraction liquide - liquide dans l'analyse des pesticides dans l'eau. Le travail réalisé consiste à mettre au point une méthode SPE sur un nouveau type de cartouche (Oasis - HLB) pour certains herbicides de la famille des triazines et phénylurées substituées. Les cartouches sont conditionnées par le passage de petits volumes de méthanol et d'eau de qualité HPLC. L'analyse des extraits a été réalisée par chromatographie en phase gazeuse avec un détecteur à azote et phosphore (CPG / NPD). L'automatisation du procédé d'extraction en phase solide a permis l'obtention de résultats très reproductibles et un important gain de temps et de solvants. Les taux d'extraction obtenus ont été supérieurs à 80 % pour la majorité des molécules étudiées

Application de l'outil hydrochimique pour la détermination du biseau salé du système aquifère de Guerbès (Nord-Est Algérien)

La nappe côtière de Guerbès est contenue dans les sables dunaires. Ces formations très perméables facilitent les échanges entre la nappe et son environnement. Les nombreux marécages présents peuvent influencer le chimisme des eaux. L'examen des cartes hydrochimiques ainsi que les profils du rapport Br/CI, mettent en évidence une salinité des eaux. Cette dernière peut avoir plusieurs origines : apports latéraux par le massif de Filfila, apport par la partie amont par l'oued Kébir, recyclage des eaux d'irrigation. Les profils Br/CI montrent un accroissement du rapport du Sud vers le Nord pouvant atteindre voire dépasser 1,7%o. Cette valeur observée dans le secteur côtier indique une intrusion marine. Au Sud, la salinité des eaux aurait une origine anthropique

A 3D In-vitro model of the human dentine interface shows long-range osteoinduction from the dentine surface

Emerging regenerative cell therapies for alveolar bone loss have begun to explore the use of cell laden hydrogels for minimally invasive surgery to treat small and spatially complex maxilla-oral defects. However, the oral cavity presents a unique and challenging environment for in vivo bone tissue engineering, exhibiting both hard and soft periodontal tissue as well as acting as key biocenosis for many distinct microbial communities that interact with both the external environment and internal body systems, which will impact on cell fate and subsequent treatment efficacy. Herein, we design and bioprint a facile 3D in vitro model of a human dentine interface to probe the effect of the dentine surface on human mesenchymal stem cells (hMSCs) encapsulated in a microporous hydrogel bioink. We demonstrate that the dentine substrate induces osteogenic differentiation of encapsulated hMSCs, and that both dentine and β-tricalcium phosphate substrates stimulate extracellular matrix production and maturation at the gel-media interface, which is distal to the gel-substrate interface. Our findings demonstrate the potential for long-range effects on stem cells by mineralized surfaces during bone tissue engineering and provide a framework for the rapid development of 3D dentine-bone interface models