• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 159
  • 151
  • 34
  • 26
  • 22
  • 10
  • 7
  • 6
  • 5
  • 4
  • 4
  • 3
  • 3
  • 3
  • 3
  • Tagged with
  • 536
  • 120
  • 105
  • 70
  • 59
  • 52
  • 49
  • 49
  • 48
  • 47
  • 47
  • 35
  • 34
  • 32
  • 28
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
341

Détection ampérométrique d'Escherichia coli (totaux et producteurs de BLSE) et d'Enterococcus spp. dans les systèmes de traitement des eaux usées et les eaux de baignade / Amperometric detection of Escherichia coli (totals and extended spectrum beta lactamase producing strains) and Enterococcus spp. in wastewater treatment plants and bathing waters

Chantemesse, Benoît 04 December 2017 (has links)
Les eaux traitées rejetées par les stations de traitement des eaux usées (STEU) et les effluents d’élevages sont à l’origine de contaminations des milieux aquatiques et des sols agricoles par des micro-organismes fécaux d’origines humaine et animale. Les eaux contaminées, et en particulier les eaux de baignade, peuvent présenter un risque sanitaire pour les humains si les concentrations en micro-organismes fécaux sont élevées, indiquant la présence potentielle de souches pathogènes et/ou résistantes aux antibiotiques. Les sols et les productions végétales peuvent également être contaminés par ces micro-organismes fécaux lors de l’épandage d’eaux traitées de STEU recyclées pour l’irrigation des cultures. Il est donc obligatoire de contrôler la qualité microbiologique des eaux de baignade et des eaux traitées de STEU pour limiter les risques sanitaires.D’un point de vue réglementaire, les contrôles de la qualité microbiologique des eaux traitées et des eaux de baignade sont basés sur la quantification de deux indicateurs bactériens de contamination fécale que sont les Escherichia coli (E. coli) et les entérocoques intestinaux (EI). Cependant, les méthodes disponibles actuellement présentent un voire plusieurs des inconvénients suivants : temps de réponse élevé, coût important, complexité de mise en œuvre, utilisation ex-situ, analyse d’un seul indicateur.Pour pallier ces inconvénients, le premier objectif de la thèse a été la mise au point d’une méthode de détection ampérométrique des E. coli et des EI, via la mesure d’activités enzymatiques spécifiques à l’aide de capteurs sérigraphiés à usage unique. Le travail réalisé a mis en évidence que la méthode ampérométrique permet d’obtenir des dénombrements en E. coli et en EI comparables à ceux obtenus avec les méthodes normalisées ISO 9308-3 et 7899-1 lors de l’analyse d’échantillons d’eaux traitées de STEU tout en offrant un temps d’analyse beaucoup plus court (en 4 à 6 h contre 36 à 72 h). De plus, l’application de la méthode à l’analyse d’échantillons d’eaux de baignade a permis de montrer que, contrairement aux 36 h minimum nécessaires avec les méthodes normalisées, la détection ampérométrique permet de déterminer en seulement 7 h si les échantillons respectent les normes de qualité sanitaires pour les eaux de baignade.Dans un second temps, une méthode de quantification ampérométrique des souches d’E. coli producteurs de β-lactamase à spectre étendu (BLSE) a été mise au point et appliquée à l’analyse d’échantillons d’eaux de STEU. Les résultats ont montré que les dénombrements ampérométriques obtenus en seulement 4 - 5 h étaient très proches de ceux fournis par une méthode de dénombrement sur milieux de culture sélectifs après un délai de 24 h. De plus, ce travail a permis de confirmer le rejet de souches productrices de BLSE par la majorité des STEU et ce, qu’elles reçoivent ou non des effluents hospitaliers.En conclusion, la méthode de détection ampérométrique des E. coli et des EI proposée autorise une détermination plus rapide de la qualité sanitaire des eaux traitées de STEU et des eaux de baignade que les méthodes normalisées qui servent actuellement de références. De plus, la détection et le dénombrement de souches d’E. coli producteurs de BLSE dans les eaux de STEU permet d’évaluer leur impact dans la dissémination environnementale de souches résistantes aux antibiotiques. L’avenir des outils électrochimiques étant prometteur, la poursuite de ce travail consistera à développer un dispositif d’analyse portable pour des applications sur le terrain. / Treated wastewaters discharged from wastewater treatment plants (WWTP) and livestock effluents are the main sources of contamination of aquatic environments and of agricultural soils by human and animal fecal micro-organisms. Contaminated waters, especially bathing waters, may present a sanitary risk for humans if the concentrations of fecal micro-organisms are high, thus indicating the potential presence of pathogenic and/or antibiotic resistant strains. Soils and crops also can be contaminated by these micro-organisms when treated wastewaters are used to irrigate cultivated soils. Consequently, microbiological quality controls are mandatory for bathing waters and treated wastewaters to manage and limit sanitary risks.According to the regulation, the microbiological controls of treated wastewaters and bathing waters rely on the quantification of two fecal indicator bacteria: Escherichia coli (E. coli) and intestinal enterococci (IE). However, the methods currently available have one or more of the following disadvantages, i. e. long response time, high cost, complexity of implementation, ex-situ use, analysis of a single indicator.To overcome these disadvantages, the first objective of the thesis was the development of an amperometric method for the detection of E. coli and IE, via the measurement of specific enzymatic activities using single-use screen-printed sensors. It was demonstrated that the amperometric method allowed to enumerate E. coli and IE in treated wastewaters samples and that the results were comparable to those obtained with the ISO 9308-3 and 7899-1 standardized methods, while offering a much shorter analysis time (in 4 to 6 h against 36 to 72 h). Moreover, the application of the amperometric method to the analysis of bathing water samples showed that contrary to the minimum 36 hours required with standardized methods, the amperometric detection provided answers regarding the sanitary quality standards for bathing waters within only 7 hours.Then in a second time, we developed an amperometric method to quantify extended-spectrum β-lactamase (ESBL)-producing E. coli in wastewaters samples. The results showed that amperometric counting obtained in only 4 - 5 h were very close to those provided by the enumeration on selective culture medium obtained after a delay of 24 h. In addition, this work confirmed the release of ESBL-producing strains by most of WWTP, whether or not they received hospital effluents.In conclusion, the proposed amperometric method to detect E. coli and IE provided more rapidly results regarding the sanitary quality of treated wastewaters of WWTP and bathing waters than the standardized methods currently used as references. Moreover, the amperometric detection and enumeration of ESBL-producing E. coli in the wastewaters of WWTP allowed to monitor their role in the environmental dissemination of antibiotic-resistant strains. Owing to the advantages of the developed electrochemical tools, further work will consist in developing a portable analysis device for field applications.
342

Trace element analysis of humus-rich natural water samples:method development for UV-LED assisted photocatalytic sample preparation and hydride generation ICP-MS analysis

Havia, J. (Johanna) 31 October 2017 (has links)
Abstract Humus-rich natural water samples, containing high concentrations of dissolved organic carbon (DOC), are challenging for certain analytical methods used in trace element analysis, including hydride generation methods and electrochemical methods. In order to obtain reliable results, the samples must to be pretreated to release analytes from humic acid complexes prior to the determination. In this study, methods for both pretreatment and analysis steps were developed. Arsenic is a toxic element and therefore its determination even at low concentration levels is important in environmental monitoring. Arsenic complexed with humic substances is not likely to form volatile hydrides quantitatively during borohydride reduction. In this study, natural water samples were digested with microwave-assisted digestion method prior to analysis by hydride generation inductively coupled plasma mass spectrometry (HG-ICP-MS). In addition, a dual mode sample introduction system was used to study internal standardization in order to correct signal variations during the measurement of arsenic with HG-ICP-MS. A novel nano-TiO2 catalyzed ultraviolet light emitting diode (UV-LED) digestion device was developed to apply green chemistry principles in sample preparation. The method consumes less harmful reagents and less energy than traditional techniques. The DOC removal efficiency was studied as a function of pH, irradiation time and hydrogen peroxide concentration. Recoveries of spiked heavy metals and hydride forming elements were studied. UV-LED technology is growing rapidly, and new catalytic semiconductor materials for photocatalysis are being developed. In this study, the effects of synthesis method variables on the properties of ZnO nanopowders were investigated. / Tiivistelmä Luonnonvesinäytteet voivat sisältää suuria määriä liuennutta hiiltä (DOC), jolloin pienten alkuainepitoisuuksien määrittäminen voi olla haasteellista esimerkiksi hydridinmuodostusmenetelmillä ja sähkökemiallisilla menetelmillä. Luotettavien tulosten saavuttamiseksi näytteet täytyy esikäsitellä analyyttien vapauttamiseksi humushappokomplekseista ennen määrityksiä. Tässä tutkimuksessa kehitettiin menetelmiä humuspitoisille luonnonvesinäytteille sekä esikäsittelyvaiheeseen että analyysivaiheeseen. Arseeni on myrkyllinen alkuaine, jonka määrittäminen pienissä pitoisuuksissa on ympäristön seurannan kannalta tärkeää. Humusyhdisteisiin kompleksoitunut arseeni ei muodosta kvantitatiivisesti hydridejä borohydridipelkistyksellä. Tässä tutkimuksessa luonnonvesinäytteet hajotettiin mikroaaltoavusteisella hajotusmenetelmällä ennen arseenin mittaamista hydridinmuodostus-induktiiviplasmamassaspektrometrialla (HG-ICP-MS). Tämän lisäksi tutkittiin mittaustarkkuuden parantamista sisäisellä standardoinnilla mitattaessa arseenia HG-ICP-MS-menetelmällä. Tutkimuksessa kehitettiin myös uudenlainen näytteenkäsittelylaitteisto, jossa käytettiin säteilylähteenä ultraviolettivaloa emittoivaa diodia (UV-LED) ja katalyyttinä nanotitaanidioksidia. Uusi ympäristöystävällinen menetelmä kuluttaa vähemmän haitallisia reagensseja ja vähemmän energiaa kuin perinteiset menetelmät. Kehitetyn menetelmän hajotustehokkuutta tutkittiin pH:n, säteilytysajan ja vetyperoksidikonsentraation funktiona. Lisäksi raskasmetallien ja hydridiä muodostavien alkuaineiden saantoja tutkittiin lisäyskokeilla. UV-LED-teknologia kehittyy nopeasti ja uusia valokatalyysimateriaaleja tutkitaan jatkuvasti. Tässä tutkimuksessa tarkasteltiin synteesimuuttujien vaikutusta sinkkioksidinanojauheiden ominaisuuksiin.
343

Datation des hydrocarbures par la méthode Re-Os : étude expérimentale du comportement géochimique du couple Re-Os dans les pétroles durant l’évolution d’un système pétrolier / Dating of hydrocarbons with Re-Os isotopes : Experimental investigation of the behavior of Re-Os in petroleum

Mahdaoui, Fatima 09 December 2013 (has links)
Le géochronomètre Re-Os a fait ses preuves dans son application aux huiles et bitumes pétroliers. Cependant, l’application de ce système sur les fluides pétroliers souffre d’un manque de compréhension de la géochimie pétrolière de Re et Os, des mécanismes de remise à zéro du géochronomètre et par conséquent des évènements réellement datés. Plus précisément, l’utilisation du géochronomètre Re-Os nécessite de comprendre la manière dont le comportement du système Re-Os permet de remplir les conditions nécessaire au développement d’une isochrone. Ces conditions sont : 1) l’homogénéisation isotopique des huiles à l’échelle d’un champ pétrolier ; 2) le fractionnement de Re par rapport à Os pour obtenir des échantillons ayant différents rapport Re/Os ; 3) la fermeture du système jusqu’au moment de la datation. Des protocoles expérimentaux ont ainsi été mis au point afin de comprendre le comportement géochimique de Re et Os dans les huiles afin d’évaluer l’utilisation du système Re-Os en tant que géochronomètre dans le cadre d’une application directe sur les pétroles. Le fractionnement de Re et Os a été vérifié dans le cas de la perte d’asphaltènes au cours de l’évolution de l’huile par précipitation séquentielle en laboratoire. Des expériences de contact entre solutions aqueuses de Re et Os et huiles ont été conduites afin d’étudier la possibilité d’un transfert des métaux entre ces deux phases sur une large gamme de concentrations et de températures. Enfin, l’étude de spéciation de Re et Os dans les huiles artificiellement enrichies en Re et Os par spectroscopie d’absorption X (rayonnement synchrotron) a permis de proposer un mécanisme d’incorporation de Re et Os dans les huiles / The Re-Os radiogenic system is well adapted to the dating of oils and bitumen. However the meaning of the obtained age is ambiguous. This is mainly due to gaps in our knowledge of the geochemical behavior and the speciation of Re and Os in oils. Specifically, use of the Re-Os system requires an understanding of how Re-Os behavior can lead to the fulfillment of the conditions necessary for the development of an isochron. These conditions are: 1) the isotopic homogenization of oils at the scale of a petroleum field 2) the fractionation of Re from Os so as to obtain samples with various Re/Os ratios 3) the closure of the system during the period of radiogenic ingrowth of the daughter isotope, that is, from the time of the event of interest to the present day. Experimental investigation of the organic geochemical behavior of Re and Os in oils under various conditions, designed as analogs of the different stages of petroleum generation and evolution, were performed in order to evaluate the use of the Re-Os system as a geochronometer in the context of a direct use on petroleum. The possibility of Re-Os fractionation resulting from asphaltene loss during oil evolution was investigated by sequential asphaltene precipitation in the laboratory. The possibility of metal transfer from formation waters to petroleum was studied by performing contact experiments between oils and aqueous solutions of Re and Os of various concentrations over a wide range of temperatures and for varying periods of time. Finally, the study by X-ray absorption spectroscopy of Re and Os in oils artificially enriched in these elements contributed to the proposal of a mechanism for Re and Os incorporation at the oil-water interface
344

WATER QUALITY IN THE LOWER COLORADO RIVER AND THE EFFECT OF RESERVOIRS

Slawson, G. C., Jr. 07 1900 (has links)
Comparison of the power spectra of TDS time series from different locations on the Lower Colorado River is useful in showing changes in salinity and for indicating physical factors influencing salinity. Similarities between the power spectra of the Lee Ferry and Grand Canyon tine series indicated that lateral inputs and evaporation are not greatly influencing the salinity cycle. The salinity change within this reach was approximated by a constant concentration change of 66.6 ppm. A similar model form was used for the Hoover Dam to Parker Dam reach. Dissimilarities between power spectra indicated that additional inputs are significant and must be accounted for in any model of such reaches. The model for Lake Mead required compensation for evaporation and for the inputs of the Virgin River and Las Vegas Wash. The modeled salinity increase between Parker Dam and Yuma contained a trend factor to allow for the effect of irrigation return flows and seepage. The crosscovariance function was used to approximate the time lag between data stations. Time series statistics, including coherence, response function spectra, and overall unit response, were used and are of utility in estimating salinity in a river system.
345

Conditions for Cooperative Water Resource Management in a conflict affected society : A case study of the Ibër River Basin

Berne, Astrid January 2020 (has links)
Kosovo is a disputed territory, in conflict with Serbia, the country it declared independence from in 1999. The two states share water resource, in the form of the Ibër river. Kosovo is facing issues of water scarcity and the water it has access to is heavily polluted with untreated wastewater metallurgy waste.Kosovo does not only have poor relations with Serbia, there are also conflict within Kosovo with communities of both Kosovo Albanian majority and Serb majority. These communities have shown different willingness to cooperate over the water management of the Ibër river basin. Cooperating over shared water resources have in other cases been used as a way to improve on relations in conflict affected societies, through environmental peacemaking. In this case study, the environmental and socio-political conditions for environmental peacemaking is investigated through interviews of municipal and regional stakeholders, involved in the management of the Ibër river basin. Interviews were conducted with two municipal employees and one representative from the regional river basin authority in Kosovo. These interviews were complemented with a comprehensive literature review. The findings were analysed, using a conceptual framework developed to analyse and compare different cases of environmental peacemaking. The conceptual framework consists of six elements: resource scarcity, interdependence, lack of environmental sustainability, mutual interests, shared values, and power (a)symmetries. External actions and interests was also included as an element to reveal in what way external actors can intervene and assist in improving relations through environmental peacemaking initiatives. The analysis concluded that the Ibër river basin is in a need of transboundary management to improve on the water quality in a more effective and efficient way. The resource scarcity that is currently facing the stakeholders could be used as a cooperative trigger between the different actors. And while there is a lot of complexity to within the socio-political conditions, the interviewees express the need and interest for increased cooperation. This indicates that increased collaboration could be possible, but most likely there would be a need for external interventions to create an ongoing dialogue, that in turn can build trust between the conflicting parties. / <p>Remote presentation on Teams</p>
346

Sous-produits de dégradation d'herbicides dans le milieu naturel et sur les filières de traitement des eaux : quelles origines, quels impacts et quelles solutions ? / Herbicides metabolites in the natural environment and water treatment processes : what sources, impacts and solutions?

Grandcoin, Alexis 21 June 2019 (has links)
Résumé : La Bretagne (France) est une région agricole où les polluants émergeants sont très susceptibles d’atteindre les eaux de surfaces. La surveillance institutionnelle montre que les sous-produits d’herbicides sont la principale pollution des eaux de surface, dans une région où 80 % des eaux potables sont produites à partir de ressources superficielles. Le comportement dans l’environnement des sous-produits d’herbicides est mal connu et, pour certains d’entre eux, les contributions de leurs différentes sources font toujours débat. Dans l’est de la Bretagne, le bassin versant de la Vilaine (10 500 km²) est d’un grand intérêt pour la recherche, car il abrite une importante usine de potabilisation (100 000 m3/j) à son extrême aval. Dans ce contexte, cette étude vise à (i) cartographier le bassin versant, (ii) évaluer la contamination et ses variations spatiales et saisonnières, (iii) comprendre les conditions favorables à l’export vers les eaux de surface, (iv) étudier les sources et le devenir de l’AMPA (acide aminométhyl phosphonique) dans les eaux usées, (v) explorer le procédé d’ozonation pour un sous-produit récalcitrant aux traitements de l’eau potable. Cette thèse consiste en trois chapitres : une revue de la littérature sur l’occurrence et le devenir des herbicides et leurs sous-produits dans les eaux de surface, eaux usées, et eau potable; le matériel et méthodes incluant, la sélection des composés d’intérêt, la stratégie d’échantillonnage, la description des méthodes d’analyses et d’assurance qualité, les outils statistiques; les résultats d’occurrence et de comportement des sous-produits d’herbicides dans les différentes eaux étudiées. Ces travaux se concluent sur un contexte plus large avec des perspectives pour acquérir une meilleure compréhension des sources et des facteurs influençant l’occurence des sous-produits d’herbicides dans les différentes eaux, dans le but d’améliorer la qualité des ressources. / Abstract : Brittany (France) is an agricultural region, where emerging pollutants are highly at risk to reach surface waters. Legal monitoring shows that herbicides metabolites are the main pollution of surface waters, in a region where 80 % of drinking water is produced with surface waters. The environmental behavior of herbicides metabolites is badly known and, for some of them, the contributions of their different sources are still debated. In east Britany, the Vilaine watershed (10 500 km²) is of great research interest, as a large drinking water treatment plant (100 000 m3/day) is located at the extreme downstream of it. In this context, this study aims to (i) map the watershed, (ii) evaluate the contamination and its spatial and seasonal variations, (iii) understand the favoring conditions resulting in metabolites export towards surface water, (iv) study sources and fate of AMPA (aminomethylphosphonic acid) in wastewaters, (v) explore ozonation treatment of a resistant metabolite in drinking water This thesis consists of three chapters: a review of the literature on herbicides and their metabolites occurrence and fate in surface waters, wastewaters, and drinking water; the materials and methods including, selection of compounds of interest, sampling strategy, description of the methods of analysis and quality assurance, statistical tools; the results of herbicides metabolites occurrences and behavior in the different waters studied. This work concludes on a broader context by providing perspectives to gain a better understanding of the sources and the factors influencing herbicides metabolites occurrences in the different waters, in order to improve the quality of water resources.
347

Stanovení tenzidů v hasebních prostředcích / Determination of surfactants in fire extinguishing devices

Janebová, Bibiana January 2011 (has links)
Nowadays are foam concentrates used as the primary extinguishing agent for flammable liquid fires (especially hydrocarbons), means of transports fires, the release of chemical substances in environmental accidents, and their importance is still growing with the industrial development. All units of fire protection have foam concentrates in their equipment, so it is important that firefighters to have some necessary knowledge about their characteristics and to be able to use them effectively and safely for the environment. The basic component of foaming concentrates are surfactants. This diploma thesis analyzes foam samples which are commonly used, by methods for analysis of drinking, surface and wastewater and determines cationic, anionic and nonionic surfactants.
348

Fotosyntetické charakteristiky fytoplanktonu eutrofních vod / Photosynthetic characteristics of phytoplankton in eutrophic waters

Tesařová, Blanka January 2011 (has links)
Photosynthesis and primary production were estimated in fishpond phytoplankton during period 2008-2010 in Třeboň fishpond region, Czech Republic. Photosynthesis was measured by the oxygen method in computer-assisted light pipetting system Illuminova. Altogether 64 samples of fishpond phytoplankton and 11 cyanobacterial cultures were analysed. Cyanobacteria and chlorococcal algae formed the most important part of phytoplankton biomass and their photosynthesis-irradiance (P-I) curves showed shade-adapted type of P-I curves with the high photosynthetic efficiency. No significant differences in the main parameters of P-I curves were obtained between different types of phytoplankton (chlorococcal-dominated, cyanobacteria- dominated). The results are consistent with the high turbid conditions in eutrophic or hypetrophic fishponds. On the contrary photosynthesis in cyanobacterial cultures differs from "wild" phytoplankton and therefore they can not be taken in primary production models. Primary production was estimated according Talling's model (1957), based on daily measurement of radiation, extinction coefficient of water and seasonal courses of chlorophyll concentration. Photosynthetic capacity and onset of light saturation determined in P-I curves were used as physiological parameters of Talling's model. The...
349

TRACKING WASTEWATER EMISSIONS IN RIVERS ENTERING GULF OF BOTHNIA COAST

Mkandawire, Helen January 2023 (has links)
The Gulf of Bothnia consists of two sub-basins in the northern Baltic Sea: the Bothnian Sea (salinity 4-5‰) and Bothnian Bay (salinity 2-3‰). Changing nutrient concentrations and signs of eutrophication has recently been observed in the Gulf of Bothnia. Many rivers enter this sea area, and potentially river inflows constitute a source of nutrient pollution via waste-water emissions. The aim of this study was to elucidate effects of waste-water emissions in four rivers in northern Sweden, Luleå, Skellefteå, Umeå and Söderhamn. My approach was to compare nutrient concentrations at upstream and downstream sampling stations related to the position of waste-water treatment plants. Temporal data from 2006 to 2021 were used and statistically analyzed using non-parametric tests to establish spatial and temporal patterns for nutrient discharged to the coast. The results showed that there are statistically differences in dissolved inorganic phosphorus (DIP) in the form of phosphate (PO4), ammonia (NH4) and total nitrogen (TotN) between the upstream and downstream of Luleå and Umeå wastewater treatment plants. No statistically significant differences were observed in the upstream and downstream data for Söderhamn and Skellefteå. This suggest that better management and mitigation of nutrient loading from wastewater treatment plants that serve higher populations is paramount to achieve the zero-eutrophication goal in the Gulf of Bothnia.
350

[pt] AVALIAÇÃO E CARACTERIZAÇÃO DE MICROPLÁSTICO EM ÁGUAS SUPERFICIAIS COSTEIRAS ENTRE A BAÍA DE GUANABARA E ILHAS CAGARRAS, RIO DE JANEIRO / [en] EVALUATION AND CHARACTERIZATION OF MICROPLASTIC IN COASTAL SURFACE WATERS BETWEEN GUANABARA BAY AND CAGARRAS ISLAND, RIO DE JANEIRO

PHELIPE PEREIRA MARINHO 11 February 2022 (has links)
[pt] Microplásticos (partículas poliméricas com tamanho inferior a 5 mm) são contaminantes ubíquos nos ambientes aquáticos, e há uma crescente preocupação sobre os seus efeitos sobre a saúde ambiental e humana. Apesar dos riscos dessa classe de contaminante, no Rio de Janeiro os trabalhos nessa área ainda são incipientes e se torna necessária uma correta avaliação da presença e distribuição de microplásticos. Com base nesse cenário, o presente trabalho tem como objetivos principais: (i) avaliar a ocorrência e a dispersão de microplásticos entre a Baía de Guanabara e Monumento Natural (MoNa) das Ilhas Cagarras; e (ii) determinar quantitativamente e qualitativamente o microplástico coletado. O material contado e separado em classes foi levado para posterior identificação com FTIR-ATR e caracterização da superfície via SEM-EDS. Os resultados mostram uma maior densidade de microplástico nos pontos mais próximos da Baía de Guanabara, sendo observado um gradiente de densidade ao longo dos pontos. Em duas campanhas houve uma maior abundância em itens menores que 1 mm (51,0 ± 5,9 porcento), enquanto em outras duas campanhas, a maior abundância correspondeu à classe de tamanho 1<x≤2 mm (30,0 ± 4,5 porcento). Os polímeros polietileno, polipropileno e poliuretano apresentaram maior representatividade em todas as classes sendo responsáveis por mais de 90 porcento da composição dos materiais. Os resultados podem representar a Baía de Guanabara e emissários submarinos como vetores de contaminação sobre o MoNa Cagarras, causando danos à fauna e flora local. Polímeros com menor densidade que a água do mar se mostram ubíquos devido à sua grande capacidade de dispersão influenciado por correntes, ventos e marés. / [en] Microplastics (polymer particles less than 5 mm in size) are ubiquitous contaminants in aquatic environments, and there is growing concern about their effects on environmental and human health. Despite the risks of this class of contaminant, works in this area in Rio de Janeiro are still incipient and a correct assessment of the presence and distribution of microplastics is necessary. Based on this scenario, the main aims of the present work are: (i) to evaluate the occurrence and dispersion of microplastics between Guanabara Bay and Natural Monument (MoNa) of the Cagarras Islands; and (ii) quantitatively and qualitatively determining the collected microplastic. The material counted and separated into classes was taken for further identification with FTIR-ATR and surface characterization via SEM-EDS. The results show a higher density of microplastic in the points closest to Guanabara Bay, with a density gradient being observed along the points. In two campaigns there was a greater abundance of items smaller than 1 mm (51.0 ± 5.9 percent), while in two other campaigns, the greatest abundance corresponded to the size class 1<x≤2 mm (30.0 ± 4 .5 percent). Polyethylene, polypropylene and polyurethane polymers were more representative in all classes, accounting for more than 90 percent of the composition of materials. The results may represent the Guanabara Bay and submarine outfalls as vectors of contamination on the MoNa Cagarras, causing damage to the local fauna and flora. Polymers with a lower density than seawater are ubiquitous due to their great dispersion capacity influenced by currents, winds and tides.

Page generated in 0.0449 seconds