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  • 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.
31

Rtuť v odpadních vodách / Mercury in waste water

Paříková, Lucie January 2008 (has links)
In the time period from November to April of the academic year 2007/2008 presence of mercury and its forms was monitored in the waste waters of Faculty of Chemistry, VUT in Brno. The level of mercury was determined as total mercury with help of the atomic absorption spectrometry method and in available forms by diffusive gradient in thin film technique.
32

Vývoj techniky difúzního gradientu v tenkém filmu (DGT) pro stanoveni rtuti ve vodných systémech. / Development of Diffusive Gradients in Thin Films Technique for Determination of Mercury in Aquatic Systems

Szkandera, Roman January 2011 (has links)
The theoretical part of this doctoral thesis deals with determination of mercury and its species in aquatic systems. Special attention is paid to the use in situ sampling technique diffusive gradients in thin films technique (DGT) and its development. Current resin gels used for determination of mercury by DGT technique Duolite GT-73, Chelex-100 and Spheron-Thiol are described. Moreover, new types of resin gels including Iontosorb AV modified by imidazole or 6-mercaptopurine and commercially available titanium dioxide. Preparations of resin gels and their basic tests in model solution according to DGT Research are described. Mercury accumulation in relation to time and basic recovery test were tested and capacity of resins was determined. All tested resins meet the requirements of basic DGT Research tests and relative standard deviations of mercury in recovery tests were lower than 10 %. The sorption capacity of resins varied from 1,5 to 6 µmol.l-1 and decreased in following order: Duolite GT-73 > ISAV-IM > Chelex-100 > Spheron-Thiol > TiO2 > ISAV-MP. Mercury sorption on resins was investigated under conditions similar to those in natural waters. It was found that the ionic strength commonly occurring in natural waters does not affect the determination of mercury. The presence of chlorides significantly affects the determination of mercury using DGT with titanium dioxide and therefore this sorbent can not be recommended for the determination of mercury in sea waters. The accumulated amount of mercury, depending on the pH shows that all the sorbents can be used in natural waters with pH in the range form 4 to 8. Mercury sorption is most affected by the presence of humic acids, especially at ion-exchange resins containing other than thiol functional groups. The exception is titanium dioxide for which physical sorption of humic acid metal complexes is typical. Cadmium and copper in model solutions in the molar balance of the excess mostly influenced the sorption of mercury on Chelex-100 and Spheron-Thiol resins. After laboratory tests, the DGT units with studied sorbents were used for the determination of mercury in natural waters of South Moravia (Svratka, Jihlava and Svitava river). Mercury concentration determined using DGT units containing Duolite GT-73 resin was comparable to the total dissolved concentration of mercury in river water provided by direct determination using AAS technique. Order of magnitude smaller concentrations than the total dissolved mercury concentration were found using DGT containing Spheron-Thiol and ISAV-MP resins. These sorbents are probably able to capture only mercury present in the form of labile complexes. This can be used for speciation analysis if more DGT units with different resins are deployed together. Subtracting the measured DGT Spheron-Thiol or ISAV-MP concentrations from the DGT Duolite GT-73 concentration, information about the amount of mercury present in the form of stabile complexes can be obtained. The amount of mercury determined after application of DGT units containing ISAV-IM, Chelex 100 or TiO2 can probably represent the mercury fraction bound in even weaker complexes than fraction determined by Spheron-Thiol and ISAV-MP DGT.
33

Transport kovů v systému půda/rostlina. Porovnání metody aktivního a pasivního vzorkování (Technika difúzního gradientu v tenkém filmu) / Metals Transport in the System Soil/Plant. Comparison of the Active and Passive Sampling Method (The Diffusive Gradients in Thin Films Technique)

Trávníčková, Jana January 2011 (has links)
The doctoral thesis deals with comparison between copper uptake by radish (Raphanus sativus L.) and concentration of copper measured by a DGT-device and concentration of copper obtained by extraction with generally used extraction agents (HNO3, NaNO3 and water). Plants were cultivated in pot experiments on a tested non-treated and gradually spiked soil. The amount of copper was determined in various part of radish (whole plant, above- and below-ground part) after mineralization in the APION mineralizer by ET – AAS. The highest concentration was in belowground part, especially in root tissues and sheel of root bulb. It confirms copper is associated with cell walls. The amount of copper taken by radish up does not pass beyond sanitary standards not even in spiked soils and consummation of radish is not unhealthy. Good correlations were found between copper concentration in radish and the amount of copper extracted with HNO3, NaNO3 and water and the amount found in soil solution. Results of extraction with HNO3 confirmed the amount of copper was stable in spiked soils during the pot experiments. The DGT experiments have shown that the rate of resupply from the solid phase to soil solution is constant during the deployment time. Whereas the release of copper decreases after 24 hours in natural soil. Copper added to soil in form of cupric ions is present in the different form after one month-equilibration than copper present in unspiked soils. The results obtained by DGT measurements were approximately up to two orders of magnitude lower than copper concentration obtained by leaching with sodium nitrate. The extraction with sodium nitrate does not provide true reflection of metal availability to plant root system and soil microorganism. High values of correlation coefficients (R2 > 0,9) were found between concentration of copper in radish plant and the concentration of copper in soil solution measured by DGT technique. Concentration of copper in soil solution was three times higher than concentration measured by DGT technique. Soil solution contains species of copper that are not measured by DGT technique and available to plants. Concentration of metals obtained by DGT measurements is more closely to real concentration of bioavailable forms of metal in soil. Therefore it is possible to recommend the DGT technique as a technique for determination of bioavailable forms of copper in soils.
34

AN INTEGRATED GPS TRACKING AND TELEMETRY SYSTEM FOR RANGE APPLICATIONS

Wells, Lawrence L., Montgomery, Robert S. 10 1900 (has links)
International Telemetering Conference Proceedings / October 26-29, 1998 / Town & Country Resort Hotel and Convention Center, San Diego, California / This paper describes a highly integrated and low cost GPS Translator/Telemetry system for use on missile platforms – the Digital GPS Translator (DGT), a component part of the Translated GPS Range System (TGRS). The DGT provides translated GPS tracking capability combined with transmission of telemetry at rates of up to 10 Mbps with optional encoding and/or encryption. This integrated approach to GPS tracking and telemetry results in a significant reduction in hardware size and cost compared to a segregated approach. The TGRS includes a ground-processing unit that provides real time processing of both the GPS and telemetry portions of the DGT transmission.
35

Avaliação in situ da biogeodisponibilidade de metais em área de mineração usando as técnicas de peixes transplantados e DGT / In situ evaluation of the biogeoavailability of metals in a mining area using transplanted fishes and DGT techniques

Eismann, Carlos Eduardo [UNESP] 14 November 2017 (has links)
Submitted by CARLOS EDUARDO EISMANN null (kadueismann@gmail.com) on 2018-01-05T14:55:15Z No. of bitstreams: 1 Dissertação Carlos Eduardo Eismann.pdf: 1179566 bytes, checksum: 31c2f0993986aed5992b2088ac3153cb (MD5) / Rejected by Adriana Aparecida Puerta null (dripuerta@rc.unesp.br), reason: Prezado Carlos Eduardo Eismann, Solicitamos que realize uma nova submissão seguindo as orientações abaixo: - Capa - Faltou a capa no documento enviado. - Folha de Aprovação (faltou) Estes itens são elementos obrigatórios de acordo com as normas de trabalhos do seu Programa de Pós Graduação. Agradecemos a compreensão e aguardamos o envio do novo arquivo. Atenciosamente, Biblioteca Campus Rio Claro Repositório Institucional UNESP on 2018-01-08T18:12:45Z (GMT) / Submitted by CARLOS EDUARDO EISMANN null (kadueismann@gmail.com) on 2018-01-09T12:39:53Z No. of bitstreams: 1 Dissertação Carlos Eduardo Eismann.pdf: 1285572 bytes, checksum: b10940da816026c45e4e6fa92a5d4807 (MD5) / Approved for entry into archive by Adriana Aparecida Puerta null (dripuerta@rc.unesp.br) on 2018-01-09T18:37:35Z (GMT) No. of bitstreams: 1 eismann_ce_me_rcla.pdf: 1252029 bytes, checksum: 63e1b3228ec61f7168a0ff587899bcec (MD5) / Made available in DSpace on 2018-01-09T18:37:35Z (GMT). No. of bitstreams: 1 eismann_ce_me_rcla.pdf: 1252029 bytes, checksum: 63e1b3228ec61f7168a0ff587899bcec (MD5) Previous issue date: 2017-11-14 / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / A toxicidade e biodisponibilidade dos metais presentes no ambiente estão diretamente relacionadas com as suas condições de especiação. A avaliação in situ da biogeodisponibilidade de metais é uma ferramenta importante na manutenção da qualidade ambiental dos sistemas aquáticos. A técnica DGT (do inglês Diffusive Gradient in Thin Films) e o uso de animais transplantados são capazes de fornecer informações desta natureza. As biodisponibilidades de Al, Fe, Mn e Zn em águas de três pontos no interior de uma área de mineração desativada no município de Caldas-MG, Brasil, foram avaliadas utilizando-se a técnica DGT e exemplares transplantados do peixe Oreochromis niloticus. As amostragens foram realizadas em períodos de 14, 28 e 42 dias. Foram utilizados dispositivos DGT com géis difusivos e restritivos e foram determinadas as concentrações de Al, Fe, Mn e Zn nos fígados, brânquias e músculos dos peixes após digestão ácida em microondas. As determinações das concentrações dos analitos nas amostras foram realizadas por Espectrometria de Emissão Óptica com Plasma acoplado Indutivamente (ICP-OES). A massa acumulada nos dispositivos com géis restritivos foi maior que com os géis difusivos, indicando uma possível contribuição da fração moderadamente lábil na massa acumulada nos dispositivos. Os resultados da DGT indicaram uma presença de concentrações muitos baixas de espécies orgânicas destes elementos em todos os pontos estudados. As maiores frações de Al, Fe, Mn e Zn foram identificadas nos pontos 014, 023, 023 e 041 respectivamente. O método proposto se mostrou satisfatório para determinar as concentrações de Al, Fe, Mn e Zn em todas as amostras dos tecidos de O. niloticus. Foram observados incrementos significativos nas concentrações de Mn e Zn nas brânquias dos exemplares transplantados quando comparados com aqueles não transplantados. As concentrações lábeis foram mais satisfatórias do que as concentrações dissolvidas em predizer a variabilidade espacial das concentrações biodisponíveis de Al, Fe, Mn e Zn. / The toxicity and bioavailability of metals in the environment is directly associated to its speciation conditions. The in situ evaluation of the biogeoavailability of metals is an important tool to support the environmental quality of aquatic systems. The DGT technique (Diffusive Gradients in Thin Films) and the use of transplanted animals are able to give this kind of information. The bioavailability of Al, Fe, Mn and Zn was evaluated at three points inside a disabled uranium mining site at Caldas city, Brazil, using DGT technique and transplanted specimens of the fish Oreochromis niloticus. The samplings were performed in periods of 14, 28 and 42 days. The DGT devices were deployed using diffusive and restrictive gels and the Al, Fe, Mn and Zn concentrations were determined at the kidney, gill and muscle of the fishes after an acid digestion using a microwave. The determinations of the analytes were performed by Inductively Coupled Plasma Optic Emission Spectrometry (ICP-OES). The accumulated mass in the devices using restrictive gels was higher than using diffusive gel, indicating that there’s probably a contribution of the moderately labile fractions to the accumulated mass of these devices. Results from DGT indicated the presence of very low concentrations of organic species of Al, Fe, Mn and Zn in all the sampling points. The highest labile fraction of Al, Fe, Mn and Zn were observed at points 014, 023, 023 e 041 respectively. The proposed method was satisfactory in determining the concentration of Al, Fe, Mn e Zn in all the tissue samples of O. niloticus. A significant increase of the Mn and Zn concentrations was observed in the gills of the transplanted specimens when comparing to the not transplanted ones. The labile concentrations were more satisfactory predicting the spatial variability of the bioavailable Al, Fe, Mn and Zn concentrations than the dissolved concentrations.
36

Stanovení mobilních forem rtuti v půdách pomocí techniky difúzního gradientu v tenkém filmu

Zouharová, Iveta January 2015 (has links)
The diploma thesis deals with the determination of mobile forms of mercury using the technology of diffusion gradient in thin-film. The theoretical part deals with the occurrence of chemical forms of mercury in the environment, mercury effects on plants and methods of determination of mercury's mobile forms. In the practical part, the accumulation of mercury from soils into various organs of garden pea (Pisum sativum L.) was observed. Soil samples were taken in Brno, in streets Opuštěná and Zvonařka. The contents of mercury in soils ranged from 0,32618 +- 0,02493 mg.kg-1 to 0,08382 +- 0,00255 mg.kg-1. Only 0,15 - 0,20 % of the mercury passed from the soil into the soil solution. Only 2,21 to 3,45 % of mercury was available for the soil solution for DGT units and therefore also for the plants. The mercury content in the soil influenced the amount of mercury in the garden pea. The highest concentrations of mercury were detected in the leaves and roots, the lowest concentrations were in the consumed parts of garden pea. The significant correlations were found out between the content of mercury's mobile forms provided by DGT method and the mercury content in roots, leaves and stem of garden pea (correlation coefficients from 0,913 to 0,984). Simulation of acid rains did not demonstrate the raise of mercury's mobility relating to the increase of the acidification of the soil.
37

Biodostupnost rtuti ve vysoce kontaminovaných půdách a její přestup do hub

Bártová, Veronika January 2016 (has links)
This diploma thesis deals with bioavailability of mercury in high contaminated soils collected in the Jedová hora in the Brdská vrchovina and their change to mushrooms. Theoretical part deals with parameters of mercury, its toxicity and appearance in Environment with focus on mercury content in the soil and change of mercury to the biota (to mushrooms and mosses). In practical part was summarized own analysis of mercury assessment with assistance of dedicated atomic absorption spectrometer AMA 254 and mobile form of mercury by technology of diffuse gradient in thin film - DGT. Average amount of mercury in collected samples of the soil moved between 1,25 +/- 0,01 mg.kg-1 - 276,18 +/- 0,09 mg.kg-1. From the soil to the soil solution passed only 0,01 - 0,09 % of mercury. From the soil solution was for DGT units, therefore for biota, available only 0,10 - 4,47 % of mercury. The mercury content in the soil solution (r = 0,861) and mobile forms of mercury (r = 0,980) in the soils significantly correlated with the total mercury content in soils and also with the total sulphur content in the soils (r = 0,931). The highest concentration of mercury in mushrooms was detected in dry matter of Holubinka sesterská (Russula sororia Fr.) 12,490 +/- 2,439 mg.kg-1 and highest concentration of mercury in mosses was measured in dry matter of Ploník ztenčený (Polytrichum formosum) 0,420 +/- 0,111 mg.kg-1.
38

Studium bioakumulace vybraných kovů vodním mechorostem Fontinalis antipyretica / Study of metals bioaccumulation by the aquatic moss Fontinalis antipyretica

Jaskowiecová, Lenka January 2008 (has links)
This diploma thesis is focused on determination of bioavailable cadmium in natural waters. Thesis is devided to two parts-laboratory study in model solution and experiments in real surface water system. During the laboratory experiments the accumulation and release constants of cadmium by aquatic moss Fontinalis antipyretica were determined. In Morava river experiment this aquatic moss was used to determine bioavailable fraction of cadmium and the moss bag technique were compared with another methods for phytotoxic metals determination.
39

Influence de l'herbier de Zostera noltei sur la méiofaune benthique et la géochimie de sédiments intertidaux du Bassin d'Arcachon / Influence of Zostera noltei meadows on benthic meiofauna and geochemistry of the intertidal sediment of Arcachon Bay

Cesbron, Florian 13 March 2015 (has links)
Cette thèse visait l’étude des micro-environnements géochimiques créés par la présence de l’herbier de Zostera noltei et de son réseau racinaire dans le Bassin d’Arcachon ainsi que ses effets 1) sur l’écologie des foraminifères benthiques, un groupe d’organismes présent en grand nombre dans les sédiments et dont l’influence sur les cycles biogéochimiques reste mal connue et 2) sur les espèces chimiques et les flux benthiques associés. Pour y répondre, une stratégie multidisciplinaire a été mise en place. L’étude écologique des foraminifères benthiques à l’échelle centimétrique, conduite dans des sédiments avec et sans végétation en février et juillet 2011, a montré la présence de trois espèces majeures aux métabolismes spécifiques. L’herbier de Zostera noltei semble influencer la densité et la profondeur de vie des espèces calcaires hétérotrophe (Ammonia tepida) et mixotrophe (Haynesina germanica), présentes près de la surface des sédiments. La troisième espèce (Eggerella scabra), au métabolisme anaérobie encore inconnu, est retrouvée sur au moins 7 cm de sédiment et semble préférer le carbone organique issu de la dégradation de l’herbier. En surface, la contribution des foraminifères à la reminéralisation aérobie a été évaluée à 7 % soit 5 fois plus que lors des études précédentes dans d’autres environnements marins. La présence de l’herbier influence également la géochimie du sédiment où des structures enrichies en fer dissous et appauvries en sulfure sont observables en 2D grâce aux gels DET-DGT développés ici. Le phosphate dissous semble dépendre de la demande des zostères et est observé à forte concentration uniquement sous forme de spots. Une tranche de sédiment, prélevée en vis-à-vis du gel DET-DGT visait la réalisation de cartes de la phase solide et de la densité des foraminifères. Bien que ce travail reste inachevé, des méthodes comme la micro-fluorescence et la micro-tomographie aux rayons X donnent des perspectives prometteuses. De nouvelles voies de recherches ont ainsi été ouvertes grâce à des méthodologies innovantes combinant physiologie, écologie et géochimie. / This thesis aimed to study the geochemical microenvironments created by Zostera noltei meadows and its root system in Arcachon Basin and to evaluate the effect of these microenvironments 1) on living benthic foraminifera ecology, a group of organisms present in large densities in sediment which impact on marine biogeochemical cycles remain poorly known and 2) on the chemical species and associated benthic fluxes. To fulfill these objectives, a multidisciplinary strategy was developed. The study of benthic foraminiferal ecology at centimeter scale, conducted in sediments with or without vegetation in February and July 2011, has shown the presence of three major species with specific metabolisms. Zostera noltei meadows seem to influence the densities and the living depth of heterotrophic (Ammonia tepida) and mixotrophic (Haynesina germanica) calcareous species, present in the sediment surface. The third species (Eggerella Scabra), which anaerobic metabolism is still to discover, is found throughout the sedimentary column and seems to prefer the organic matter coming from the degradation of the seagrass. In surface sediment, the contribution of these three species to aerobic remineralization was estimated at 7%, i.e. 5 times more than the maximum rates previously recorded in marine environments. The presence of the seagrass also influences geochemistry where enriched iron and depleted sulfide structures are observable in 2D thanks to DET-DGT gels developed here. Dissolved phosphorus depended on seagrass uptake and was highly concentrated only as scattered spots. A slice of sediment, taken face to face with the DET-DGT gel, was also conducted during this study aiming to map the solid phase and foraminiferal density. Despite this work is still in progress, methods such as X-ray microfluorescence and microtomography showed promising perspectives. New research pathways have been opened through technological developments and innovative approaches combining physiology, ecology, and geochemistry.
40

APPLICAZIONE DI DIFFERENTI TECNICHE PER LA DETERMINAZIONE DELL’ARSENICO NELLA CATENA ALIMENTARE UMANA: DALL’ACQUA DI FALDA ALLA TAVOLA. / Application of different techiniques for Arsenic determination in human food chain: from groundwater to dining table

FONTANELLA, MARIA CHIARA 16 May 2013 (has links)
Lo scopo della tesi è di caratterizzare i rischi per la salute umana, che derivano dall’inquinamento delle acque (acque sotterranee) e dal cibo (riso) tramite l’applicazione e lo sviluppo di nuove tecniche analitiche. La tecnica “diffusive gradients in thin films (DGT)” con resina a base di ferrihydrite, è stata studiata per l'accumulo delle forme inorganiche (As(III) e As(V)) e organiche (DMA(V) e MMA(V)) di Arsenico in matrici acquose. I DGT sono stati applicati su campioni di acque sotterranee, raccolti in sei diverse città del Nord Italia, dove la concentrazione di As è molto alta. Antimonio (Sb) è associato all’As in diversi studi perché le proprietà fisiche e chimiche di questi due elementi sono simili, ed esso è stato recentemente riconosciuto come contaminante dell'acqua. In questa tesi per la prima volta sono state riportate le prestazioni dettagliate dei DGT con ferrihydrite, impiegati in soluzioni acquose di Sb(III) e Sb(V). L’analisi delle forme chimiche di Sb(III) e Sb(V) in campioni acquosi è stata realizzata con l’applicazione della diluizione isotopica. In generale il riso, a differenza di altri prodotti alimentari di origine terrestre, contiene quantità significative di Arsenico inorganico. L’analisi della speciazione di As è stata realizzata in 70 campioni di riso italiano, rappresentativo di diversi tipi di coltivazione. Le forme più abbondanti nel riso erano As(III) e DMA(V). Inoltre è stato interessante studiare la localizzazione dell’As nel chicco di riso, sottoposto a diversi processi di lavorazione (risone, riso integrale e lavorato con o senza parboiling), perché sia la distribuzione che la presenza delle diverse forme chimiche nel chicco sono fattori chiave che controllano la biodisponibilità del contaminante. La distribuzione dell’ As nei chicchi di riso di due varietà (Gladio e Ronaldo) sottoposti a diversi processi, è stato determinato con Laser Ablation ICP-MS. In realtà il contenuto di As era più alto nei chicchi di riso non-parboiled rispetto a quello parboiled. La relazione tra intensità dell’As e le varie parti del chicco di riso ha rivelato che i livelli di As diminuisco dalla parte esterna verso la posizione centrale, mentre i valori di As sembrano essere simili tra la parte media e interna dei non parboiled. / The aim of this thesis was to explore new analytical techniques as well as to carry out further characterisations of human health risks, which derive from water pollution, in particular groundwater, and food, in particular rice. The prevention of water pollution is an environmental aspect, that includes monitoring of both natural enrichment and outside pollution with routine analysis but also with new techniques, e.g. the application of passive sampling techniques and advanced technologies. The diffusive gradients in thin films (DGT) technique with ferrihydrite adsorbent, has been investigated for the accumulation of different species of Arsenic (As), like Inorganic Species (arsenite and arsenate) and Organic Arsenic (dimethylarsinic and monomethylarsenate) in aqueous matrix. To evaluate the performance of DGT method for accumulation of arsenic species, after deployment in synthetic solutions, DGT devices were carried out on groundwaters collected in six different towns in the North of Italy, where the As concentration is very high. Recently, health effects at arsenic exposures have been observed in areas where levels of inorganic As in drinking water are not excessive. Antimony (Sb) is associated to As in several studies because the physical and chemical properties of these two elements are similar, and it has been recently recognized as water contaminant. In this thesis I reported for the first time detailed performance characteristics of the Fe-oxide gel associated to DGT devices deployed in known aqueous solutions of trivalent and pentavalent Sb. Speciation analysis of Sb(III) and Sb(V) in aqueous samples was performed through extraction and on-line determination of isotope dilution concentration after a chromatographic separation. Generally rice, unlike food products of terrestrial origin, contains significant amounts of inorganic arsenic. Recently some Government Organizations (e.g. EFSA) debated the possibility to set an upper limit for total and inorganic arsenic in rice. Arsenic speciation was realized in 70 Italian rice samples from different representative cultivation conditions. The most abundant forms in rice were As(III) and DMA(V). After that, it was fundamental to investigate the localization of As in rice grains in different processes (raw, brown and milled rice with or without parboiling technique), because both speciation and distribution throughout the grain are key factors controlling bioavailability of the contaminant. The As distribution in rice grains of two varieties (Gladio and Ronaldo) from different processes, was determined by LA-ICP-MS. The distribution of As varied between the various parts of the grains (exterior, medium and interior part). During parboiling, the partial boiling of food as the first step in the cooking process, arsenic might have released from the grain to the boiling water. Thus, parboiling of rice grain may reduce the magnitude of arsenic intake in human body. Actually the As content was higher in non-parboiled rice grain than in parboiled rice. The relationship between As intensities and the different parts of rice grain revealed that As levels decreased from the external part towards the middle position, and then the intensity values seem to be similar between medium and internal part in non parboiled products.

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