Évaluation des impacts environnementaux de l'apport des boues urbaines liquides sur les plants de Mélèzes cultivés sur un sol acide : Bénéfices et risques

Organic waste valorization can be a good tool to remedy soil impoverishment problems through intensive cultivation and also to reduce fertilizer costs. Facing a growing sewage sludge production and a sludge reutilization in agriculture increasingly marginalized, the spreading in forest plantations could be a complementary alternative way. This spreading allows nitrogen and phosphorus supplies which are very beneficial for soils generally poor. Nevertheless, some contaminants in sludge, particularly trace metals (TMs), present a risk due to soil accumulation on these contaminants, aquatic contamination and transfer to the entire ecosystem trough the food chain. The objective of this study was to evaluate the benefits and risks following liquid sludge application at: (i) growth and nutritional status of larch (ii) contaminants (TMs) transfer to soil solution, plants (iii) and along the food chain.This work was conducted both under controlled conditions on young larch one year aged, grown in pots on an acidic soil amended with 30 t DW ha-1 and 60 t DW ha-1 as in the field, in sub-plots within a larch plantation and receiving 6 t DW ha-1. The effects of short and medium term showed that liquid sludge application had a beneficial effect on soil quality because improved levels of nitrogen and phosphorus, but not for other mineral elements. This last result may be due to low levels of these nutrients in the used sludge. Concentrations of copper and zinc in the upper soil were increased significantly in proportion to the sludge rate, while no effect was observed on deep soil horizons.Despite the low nitrate leaching detected at 20 cm depth, it is worth noting the potential danger of groundwater contamination. The migration of P and TMs in the soil profile was not observed in this work. It is probable that these elements are sequestered on the upper layer either by the solid matrix of the soil (for P) or by the organic matter (for TMs). However, the culture of Lemna minor conducted on the raw leachates showed a stimulation of growth after 60 t ha-1 supply. This response could be a risky situation (europhication) in case of intense leaching.Sludge application did not induce any toxicity to larch plants which showed a recovery rate higher than 98%. The results obtained in this study under controlled conditions showed a better growth in height beginning from the seventh month after sludge supply. This delayed response could be explained by the time required for mineralization of provided organic matter that improved the nutritional status of young seedlings. This improvement in nitrogen and phosphorus nutrition could account for the observed stimulation of photosynthetic activity at 6 months stage, which provides the energy needed for biomass accumulation at 12 months stage. In situ, the works did not shown any effect on either growth (height, circumference) or biodiversity of the herbaceous stratum. The differences observed between trees were further related to pedological characteristics of the station (soil depth, waterlogging) rather than the supply of sewage sludge performed at very low rate (6 t ha-1). The plant needles grown in controlled conditions accumulated Cu, Zn and Cd, while Pb was mostly sequestered in lateral roots. Nevertheless, the recorded values were below the minimum threshold of toxicity, thus no adverse effects were observed. The risk assessment of SS application on the trophic chain has been studied in situ and under controlled conditions via the transfer model soil-plant-snail. The study carried out in situ showed that mortality and weight decrease observed in snails placed in mesocosms might account for the environmental conditions such as temperature, photoperiod and/or the nature of the vegetation. By contrast, under controlled conditions, snail exposure both to contaminated lettuce and amended soil had a beneficial effect on their growth parameters. This result could be due to a high nutritional quality of lettuce plants grown on amended soil compared to control. This growth stimulation induced an increase in the levels ETM snail soft body without any detectable toxic effect.La valorisation des déchets organiques peut constituer un bon outil pour remédier aux problèmes d’appauvrissement des sols par des cultures intensives d’une part et pour limiter les coûts de fertilisation d’autre part. Face à une production de boues de STEP croissante et à une réutilisation agricole de ces boues de plus en plus marginalisée, l'épandage dans les plantations forestières pourrait constituer une voie alternative complémentaire. Cet épandage permet un apport d’azote et de phosphore très bénéfique pour les sols généralement pauvres. Cependant, les contaminants présents dans certaines boues et en particulier les éléments traces métalliques (ETM), présentent un risque d’accumulation dans les sols ainsi que de contamination des milieux aquatiques et de transfert à l'ensemble de l'écosystème via la chaîne trophique. L’objectif de cette étude est d’évaluer les bénéfices et les risques suite à l’application des boues liquides sur (i) la croissance et le statut nutritionnel chez le mélèze (ii) sur les transferts de contaminants (ETM) à la solution du sol, aux plantes (iii) ainsi que le long de la chaîne trophique.Ce travail a été réalisé à la fois en conditions contrôlées sur de jeunes mélèzes d’un an cultivés en pots sur un sol acide avec un apport de 30 t de MS ha-1 et de 60 t de MS ha-1 et sur le terrain, où des mini-placettes au sein d’une plantation de mélèze ont reçu 6 t MS ha-1. Les effets à court et à moyen terme étudiés dans ces expérimentations ont montré que l’apport de boues liquides a eu un effet bénéfique sur la qualité du sol grâce à leur effet fertilisant marqué pour l’azote et pour le phosphore, mais pas pour les autres éléments minéraux. Ce dernier résultat serait dû aux faibles teneurs en ces éléments nutritifs présents dans les boues épandues. Les teneurs en cuivre et en zinc mesurées dans l’horizon supérieur du sol ont augmenté significativement de manière proportionnelle à la dose de boues alors qu’aucun effet n’est observé sur les horizons profonds.En dépit de la faible lixiviation des nitrates détectée à 20 cm de profondeur, il convient de souligner le danger potentiel de contamination de la nappe. La migration du P et des ETM dans le profil du sol n’a pas été observée. Il est probable que ces éléments sont retenus en surface soit par la matrice solide du sol (pour le P), soit par la matière organique (pour les ETM). Cependant, la culture de Lemna minor effectuée sur les lixiviats bruts montre une stimulation de la croissance dans le cas de l’apport de 60 t ha-1 et constituerait donc un risque d’eutrophisation en cas de lixiviation intense.L’application des boues n’engendre aucune toxicité pour les plants de mélèze qui ont manifesté un taux de reprise supérieur à 98 %. Les résultats obtenus au cours de notre étude en conditions contrôlées ont montré une meilleure croissance en hauteur à partir du 7ème mois après l’apport des boues. Cette réponse différée s’expliquerait par le temps nécessaire à la minéralisation de la matière organique apportée qui améliore le statut nutritionnel des jeunes semis. Cette amélioration de nutrition azotée et phosphatée serait à l’origine de la stimulation de l’activité photosynthétique observée au stade 6 mois et qui fournirait donc l’énergie nécessaire à l’accumulation de biomasse enregistrée à la récolte de 12 mois. In situ, les travaux n’ont montré aucun effet ni sur la croissance (hauteur, circonférence) ni sur la biodiversité de la strate herbacée. Les différences observées entre les arbres sont d’avantage liées aux caractéristiques pédologiques de la station (profondeur du sol, hydromorphie) plutôt qu’à l’épandage des boues d’épuration effectué à très faible taux (6 t ha-1). Les aiguilles des plants cultivées en conditions contrôlées accumulent du Cu, du Zn et du Cd alors que le Pb reste majoritairement séquestré dans les racines latérales. Néanmoins, les valeurs enregistrées étaient inférieures au seuil minimum de toxicité, ainsi aucun effet néfaste n’a été observé.L’évaluation des risques de l’épandage des boues sur les réseaux trophique a été étudiée in situ et en conditions contrôlées à travers le modèle de transfert sol-plante-escargot. L’étude réalisée in situ a montré que la mortalité et la décroissance pondérale observées chez les escargots placés dans les mésocosmes seraient dues aux conditions environnementales, telles que la température, la photopériode et ou à la nature de la végétation. Par contre en conditions contrôlées, la double exposition des escargots (sols et laitue contaminés) a eu un effet bénéfique sur leur croissance. Ce résultat pourrait être dû à une meilleure qualité nutritive des plants de laitues cultivées sur sol amendé par rapport au contrôle. Cette augmentation de biomasse influence positivement les quantités d’ETM accumulés dans le corps mou des escargots sans aucun effet toxique décelable

Performance assessment of Etueffont (France) lagooning treatment system: Report from a 16-year survey

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Overview of pesticide use in Moroccan apple orchards and its effects on the environment

International audienceThe cultivation of apple trees needs to use phytosanitary products, which are used in an irrational way by certain farmers. The harmful effects of pesticides result mainly from their persistence in the environment. Several studies have been carried out to estimate the pesticide residues and assess their effects on soil microorganisms and aquatic organisms. The results of these studies have revealed a harmful effect on these bioindicators. Therefore, a disruption in their growth and reproduction, an increase in their mortality, and a decrease in their fertility have been proven. In addition, a considerable reduction in the number and diversity of soil microorganisms and aquatic organisms has been claimed. Other indicators, such as fish, have shown an accumulation of pesticide residues in their tissues, which can create a danger to human health. Wherefore, it is important to take into account both toxicological and ecotoxicological effects in the environment

Wastewater use in agriculture in Djibouti : Effectiveness of sand filtration treatments and impact of wastewater irrigation on growth and yield ofPanicum maximum

International audienceIn the arid climate of Djibouti, salt concentrations of up to 1200 mg L −1 have been recorded in well water, attributed to the overexploitation of aquifers. Farmers are therefore turning to untreated wastewater as a source of water for crop irrigation. The authors undertook a study in two phases. In the first phase they tested the field transposition of an experimental water treatment method previously laboratory-tested on a small scale. The pilot device was composed of an adaptor basin for the wastewater, a filter basin filled with sand and a storage basin to collect and hold the treated water. Transfer of waters from basin to basin was gravitational. The physicochemical and microbiological sleek raw water parameters were determined weekly for 7 weeks. Monitoring of chemical oxygen demand concentrations decreased from 445 ± 5.76 mg L −1 O 2 on the first day of the experiment to 101 ± 1.34 mg L −1 O 2 on the 21st day. The removal of total coliforms attained more than 99.6% as of day 21. The performance of the microbiological treatment of waters obtained through sand filtration is therefore of definite interest in agriculture. In the second phase the effect of different irrigation waters (untreated wastewater (WW), treated wastewater (TW), saline well water (SW), mixed water (MW) and potable water (PW)) on growth and yield of the grass Panicum maximum were also compared. The use of WW and TW in irrigation effectively increased stem height and aerial part dry matter compared to other treatments, while irrigation with SW and PW showed the lowest measured values. Depending on their performance, the effectiveness of the treated waters can be ranked in the following increasing order: TW; WW > MW > PW; SW. The performance of the TW treatment can be explained by its higher nutritive content, especially in N

Integrated pest management (IPM) for Ectomyelois ceratoniae on date palm

International audienceEctomyelois ceratoniae integrated pest management defines three main keys: Sterile Insect Technique (SIT), post-harvest chemical control and biological control. Each component is described with information on its implementation, adoption and importance in palm groves. The SIT, a control tool using gamma radiation to sterilize male and/or female moths before release, has been shown to significantly reduce density in subsequent generations. Alternatively, date fumigation with CO2, ethyl formate or eucalyptus essential oils has proven to be a promising control alternative to fumigation with methyl bromide. However, biological control can be considered as the most environmentally friendly and better option against this pest. A lipopeptide biosurfactant produced by Bacillus subtilis SPB1 has been shown to be very effective against E. ceratoniae infesting stored dates. In addition, the combined application of Bacillus thuringiensis with the release of parasitoids of the genus Trichogramma, Phanerotoma or Bracon would be a promising control approach

Assessment of sustainable deficit irrigation in a Moroccan apple orchard as a climate change adaptation strategy

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Proposed changes for post-closure monitoring of Etueffont landfill (France) from a 9-year survey

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Treated waste water reuse in agriculture: An Overview

The reuse of treated wastewater in agriculture is a promising solution to the water scarcity challenge faced by many regions worldwide. This review paper provides an overview of the current state of knowledge on treated wastewater reuse in agriculture, highlighting its potential benefits and challenges. The paper begins by discussing the importance of treating wastewater before reuse and the potential it offers. The benefits of using treated wastewater in agriculture are discussed, including increased water availability, improved soil fertility and reduced fertilizer use. The risks associated with the use of treated wastewater, such as the accumulation of pollutants and the potential for pathogen transmission, are also discussed. The review paper then presents some examples of reuse projects for irrigation and their success criteria. The current regulations governing the use of treated wastewater in agriculture are examined, and their evolution presented. The paper concludes with a discussion of future research needed to address the remaining challenges surrounding the use of treated wastewater in agriculture. Overall, the review paper emphasizes the importance of careful management and regulation of treated wastewater reuse in agriculture to ensure safety and sustainability to meet the growing demand for water in agriculture

Growth performance and biochemical composition of nineteen microalgae collected from different Moroccan reservoirs

International audienceMacro- and microalgae have recently received much attention due to their valuable chemical constituents. In order to increase existing data, the authors studied nineteen microalgae species isolated from different reservoirs in the Fez region (northern Morocco), undertaking experiments to determine for each species the specific growth rate, their total amounts of proteins, carbohydrates and lipids and the influence of the growth phase on these chemical constituents. The growth rates of the nineteen studied species of microalgae showed a wide interspecies variation, ranging from 0.27 d-1 for Chlamydomonas nivalis to 3.64 d-1 for Chlorococcum wemmeri. Protein, carbohydrate and lipid contents also varied greatly between taxa and within genera. Ankistrodesmus falcatus, Chlamydomonas nivalis, Chlorococcum sp., Fragilaria ulna, Scenedesmus protuberans, and Synechocystis aquatilis tended to synthesize proteins, the concentrations exceeding 20% of dry weight (DW). Ankistrodesmus falcatus, Ankistrodesmus sp., Chlorococcum wemmeri, Coenocystis sp., Isocystis sp., Lyngbya bergei, Oscillatoria amphibia, Polytoma papillatum, Scenedesmus protuberans, Scenedesmus sp. and Synechocystis aquatilis showed a high capacity for lipid storage, higher than 20% DW. For carbohydrate contents, only Scenedesmus protuberans and Scenedesmus quadricauda showed an excessive level, compared to other scanned species with 29.21% and 24.76% DW, respectively. Green algae, Scenedesmus protuberans for example, generally tend to synthesize proteins, with a content reaching 45% DW, while blue-green algae, for example Lyngbya bergei, tend to synthesize lipids, with a content reaching 50% DW

Sewage sludge used as organic manure in Moroccan sunflower culture: Effects on certain soil properties, growth and yield components

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