L'installation de décharges sanitaires représente la seule méthode de stockage des déchets ménagers solides dans plusieurs pays. Les lixiviats générés à partir de ces décharges présentent une grande toxicité aigüe et chronique. Lorsqu'ils ne sont pas traités, ces lixiviats peuvent pénétrer dans la nappe phréatique ou contaminer les eaux de surface et donc contribuer à la pollution des eaux. Divers procédés biologiques ont été appliqués au traitement des lixiviats de décharge. Cependant, ces procédés sont relativement inefficaces pour le traitement des lixiviats à cause de la présence de composés bioréfractaires. Les procédés d'oxydation avancée représentent une excellente alternative pour le traitement des eaux polluées par les polluants toxiques et/ou persistants (biorfractaires). Dans ce travail, quelques procédés d'oxydation avancée (procédé Glidarc, électro-Fenton, oxydation anodique et photo-Fenton) ont été appliqués au traitement de deux molécules modèles appartenant chacune à une famille de polluants présents dans la matrice du lixiviat tunisien de la décharge contrôlée de Jebel Chakir (identifiée dans ce travail), à savoir, l'anhydride phtalique et le 8-hydroxyquinoléine sulfate. Pour ces deux molécules, une étude de la dégradation et la minéralisation a été réalisée en optimisant les paramètres expérimentaux. L'étude cinétique montre que la dégradation oxydative des deux polluants étudiés suit une cinétique de réaction du pseudo-premier ordre, avec des temps de dégradation assez courts. Par exemple, avec une anode de Pt, l'oxydation complète de l'anhydride phtalique a été achevée en moins de 15 min sous un courant appliqué de 2,88 mA cm-2. L'identification des intermédiaires aromatiques et carboxyliques à courte chaine carbonée a permis de proposer un mécanisme de dégradation de l'anhydride phtalique par les radicaux hydroxyles. Les valeurs des constantes de vitesse des réactions entre les *OH, et les deux polluants et leurs intermédiaires ont été déterminés par la technique de cinétique de compétition à l'aide d'un composé de référence ; l'acide 4-hydroxybenzoϊque. Le suivi de la toxicité lors du traitement de la solution de 8-HQS par la méthode Microtox®, (une méthode basée sur la mesure de la luminescence des bactéries marines Vibriofischeri) a montré la formation des intermédiaires plus toxiques que les molécules mères. Une comparaison des procédés d'oxydation avancée appliqués a été réalisée pour chacun des polluants. Enfin, différents procédés d'oxydation avancée (procédé Glidarc, électro-Fenton, oxydation anodique et photo-Fenton) ont été appliqués à la dépollution du lixiviat tunisien de Jebel Chakir. Une étude comparative a été réalisée afin d'évaluer le coût des procédés. L'ensemble des résultats obtenus confirme l'efficacité du procédé électro-Fenton pour la dépollution des lixiviats

Thesis.

Techn. Hochsch., Diss., 2004--Aachen.

Nedbrytning av organiskt material är en nyckelfaktor som påverkar omvandlingar av de många grundämnen som utgör eller är associerade till just organiskt material. En stor del av nedbrytningen av akvatiskt organiskt material (OM) sker i gränsskiktet mellan sediment och vatten. Eftersom så många biogeokemiska cykler styrs av nedbrytningen av OM är det viktigt att ha kunskap om processer och påverkansfaktorer både på mikro- och makronivå. Mineraliseringshastigheten av OM är en vanligt förekommande mätparameter, men vanligtvis inkluderar mätningarna inte de naturliga processer som kan påverka nedbrytnings-hastigheterna, t.ex. fysiska krafter. Syftet med den här studien är att studera mineraliseringshastigheten av det OM som finns naturligt i ytsediment i söt- och brackvatten när det utsätts för fysiska krafter som orsakar förändringar i redox-förhållanden, resuspension eller advektivt porvattenflöde. Fem laborativa experiment har utförts för att belysa syftet: Åldrat ytsediment från en sötvattens å utsattes för olika redox förhållanden där oxisk respiration, sulfatreduktion respektive metanogenes gynnades. Resultaten visade ingen skillnad i mineraliseringshastighet beroende på behandling. Detta motsäger studier utförda i marina miljöer, där anoxiska förhållanden ger en lägre mineraliseringshastighet än oxiska. Vidare gjordes två studier på brackvattensediment där effekten av resuspension var i centrum. Den ena studien fokuserade på frekvens och varaktighet av resuspensionstiderna, den andra på olika typer av sediment. Studierna visade att väldigt korta resuspensionstider med upp till 48 timmars stillhet mellan varje resuspension ökade mineraliseringstakten med fem gånger jämfört med diffusivt utbyte, och mer än dubblerades i jämförelse med kontinuerlig resuspension eller resuspension i långa perioder. Resuspensionen under kort tid var troligen gynnande då resuspension fysiskt stör bildningen av stabila bakteriesamhällen. Mineraliseringshastigheterna i sediment som domineras av väldigt fin, fin eller medium sand visade lika hastigheter, medan grov sand visade en signifikant lägre mineraliseringshastighet. Likheterna mellan de tre första sedimenttyperna kan dock ha påverkats av tillgång på lättnedbrytbart OM då sediment och vatten hämtades in under en algblomning. Till sist studerades effekten på mineraliseringshastigheten av advektivt porvattenflöde. Detta gjordes på åldrat sediment dels från en sötvattensbäck dels från en brackvattenstrand. Inget av de två sedimenttyperna visade någon skillnad i mineraliseringshastighet i jämförelse med diffusivt styrda system. Det är i motsats till tidigare marina studier, men är i linje med den första studien, där mineraliseringshastigheten var oberoende av redox-förhållande. Den generella slutsatsen från den här studien är nödvändigheten att studera samma aspekter i olika typer av akvatiska system, eftersom responsen verkar vara annorlunda beroende på system, t.ex. söt- brack- och saltvatten. Faktorer som kan förklara de här skillnaderna finns ännu inte, vilket gör att småskaliga studier och modeller blir viktiga verktyg för att utreda detta. / Organic matter mineralisation is a key parameter that affects most other element transformations associated with organic matter. A substantial part of aquatic organic matter (OM) mineralisation takes place at the interface between sediment and water. Understanding OM mineralisation is important at both the micro and macro scales, since it drives many biogeochemical cycles. OM mineralisation rates are widely measured, but generally not all the natural factors possibly affecting the rates, such as physical forcing, are considered. This thesis examines the mineralisation rates of indigenous OM in fresh and brackish surface sediments, subjected to different physical forces inducing changed redox conditions, resuspension, and advective pore water flow. Five experiments were performed to this end. Aged surface sediment from a freshwater river was subjected to different redox conditions favouring oxic respiration, sulphate reduction, and methanogenesis, respectively. Results indicated no difference in mineralisation rate irrespective of treatment. This contradicts what has been found in marine environments, where anoxic mineralisation rates are lower than oxic ones. Further, two studies of resuspension of brackish sediments were performed, one addressing the impact of the frequency and duration of the resuspension events, and the other addressing the impact of resuspension on different types of sediments. The studies found that very brief resuspension events followed by calm periods of up to 48 h increased mineralisation rates by five times compared to diffusion, and more than doubled the rate compared to continuous or long-term resuspension. The short-term events were possibly favoured because resuspension physically disturbs the arrangement of a stable bacteria community. Mineralisation rates on sediments dominated by very fine, fine, or medium-grained sand were the same, while coarse sand displayed a significantly lower rate. The similar rates of the three first sediment types could stem from access to labile OM, due to an ongoing algae bloom when the sediment and water samples were collected. Finally, the effect of advective pore water flow on aged sediment from one fresh and one brackish sediment was studied. Neither of the sediments displayed a mineralisation rate different from those occurring in incubations in which only diffusive exchange occurred. This contradicts the findings of previous marine studies, but is in line with the first study, which did not detect different mineralisation rates irrespective of redox conditions. The general conclusion is that it is necessary to study the same physical forces in different aquatic environments, since responses appear to differ, for example, between freshwater, brackish, and marine environments. Factors explaining these differences have not yet been expressed, making small-scale studies and modelling a challenge for future research.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Crop residues (CR) composed by shoots and roots of plants are the main source of C for the agricultural soils. During the decomposition of these CR in the soil, part of C is evolved as CO2 and nutrients are mineralized, with emphasis on the N. Among the factors that affect decomposition of CR, the biochemical composition has great importance. The objectives of this study were: a) evaluate the dry matter production (DM) and biochemical composition of CR of shoot and roots from commercial and summer cover crops; and b) evaluate the influence of biochemical composition of the transformations of C and N, when CR are kept on the surface (shoot), or incorporated to soil (roots). It was realized two studies, in the first one, it was quantified the DM and biochemical composition of CR from shoot (leaves and stalks) and roots. In the second study, it was evaluated under laboratory conditions for 120 days, the mineralization of C and N and the results were correlated with the biochemical composition of the CR studied. The DM yield of roots varied from 0.54 to 2.86 Mg ha-1 in commercial crops and from 0.56 to 1.66 Mg ha-1 in cover crops. Rice and millet were the species that had the highest DM production of shoots and roots between the commercial and cover crops, respectively. Most of the DM of roots was found in the topsoil (0-10cm) and near the sowing row. The relation root/shoot average of cover crops was less than commercial crops (0.10 vs. 0.17). The CR show wide variation in their biochemical composition. The N content in the DM of CR ranged from 2.8 g kg- 1 (sunflower stalks) to 46.3 g kg- 1 (velvet leaves). The soluble fraction of Van Soest ranged from 108 g kg-1 (soybean stalks) to 774 g kg-1 DM (bean leaves). While the values of cellulose in DM ranged from 138 g kg-1 (bean leaves) to 612 g kg-1 (sunflower stalks), those of lignin ranged only from 38 g kg-1 in the leaves of Crotalaria juncea to 197 g kg- 1 in roots of soybean. The highest levels of polyphenols were found in the CR from shoot (14.1 g kg-1 DM) and roots (22.2 g kg-1 DM) of velvet beans. The CR with N content less than 15 g kg-1 (C/N > 29) cause net immobilization of N in the soil. All the roots of valued commercial crops caused immobilization of N in the soil, and the predominance of net mineralization of N was observed only with the roots of cover crops legume. In general, the mineralization of C from CR decreased in the following order: leaf > stalk+leaf > stalk. Among the CR from commercial crops, those of maize (leaf+stalk) were which presented least amount of C mineralized (39%). The mineralization of C from roots presents values similar to those observed for CR from shoot. The mineralization of N in the soil was significantly correlated with the total content of N in the DM and in the Van Soest soluble fraction of shoot and roots (P < 0.01 and r2 ranging from 0.90 to 0.98). The values of correlation between biochemical composition of CR and C mineralization were lower than those observed for N mineralization, but there was a greater number of significant correlations, especially for ratio C/N, polyphenols and NDF from Van Soest. / Os resíduos vegetais (RV) compostos pela parte aérea e raízes das plantas constituem a principal fonte de C para os solos agrícolas. Durante a decomposição desses RV no solo, parte do C é evoluído como CO2 e nutrientes são mineralizados, com destaque para o N. Dentre os fatores que afetam a decomposição dos RV, a composição bioquímica exerce grande importância. Os objetivos do presente trabalho foram os seguintes: a) avaliar a produção de matéria seca (MS) e a composição bioquímica dos RV da parte aérea e de raízes de culturas comerciais e de plantas de cobertura de solo de verão; e b) avaliar a influência da composição bioquímica sobre as biotransformações do C e do N, quando os RV são mantidos na superfície (parte aérea) ou incorporados ao solo (raízes). Foram realizados dois estudos, sendo que no primeiro quantificou-se a MS e a composição bioquímica dos RV da parte aérea (folhas e talos) e de raízes e no segundo estudo, avaliou-se em condições de laboratório por 120 dias, a mineralização do C e do N e os resultados obtidos foram correlacionados com a composição bioquímica dos RV estudados. A produção de MS de raízes variou de 0,54 a 2,86 Mg ha-1 nas culturas comerciais e de 0,56 a 1,66 Mg ha-1 nas plantas de cobertura de solo. O arroz e o milheto foram as espécies que apresentaram as maiores produções de MS da parte aérea e de raízes entre as culturas comerciais e as plantas de cobertura, respectivamente. A maior parte da MS de raízes foi encontrada na camada superficial do solo (0-10 cm) e próximo à linha de semeadura. A relação raiz/parte aérea média das plantas de cobertura foi inferior aquela das culturas comerciais (0,10 vs 0,17). Os RV apresentam ampla variação na sua composição bioquímica. O teor de N na MS dos RV variou de 2,8 g kg-1 (talos girassol) a 46,3 g kg-1 (folhas mucuna). A fração solúvel de Van Soest variou de 108 g kg-1 (talos de soja) a 774 g kg-1 MS (folhas de feijão). Enquanto que os valores de celulose na MS variaram de 138 g kg-1 (folhas feijão) a 612 g kg-1 (talos girassol) os de lignina variaram de apenas 38 g kg-1 nas folhas de crotalária juncea a 197 g kg-1 nas raízes de soja. Os maiores teores de polifenóis foram encontradas nos RV da parte aérea (14,1 g kg-1 MS) e raízes (22,2 g kg-1 MS) da mucuna cinza. Os RV com teores de N inferior a 15 g kg-1 (C/N > 29) provocam imobilização líquida de N no solo. Todas as raízes das culturas comerciais avaliadas causaram imobilização de N no solo, sendo que a predominância de mineralização líquida de N somente foi observada com as raízes das plantas de cobertura leguminosas. De maneira geral, a mineralização do C dos RV decresceu na seguinte ordem: folha > talo+folha > talo. Entre os RV das culturas comerciais, aqueles do milho (folha + talo) foram os que apresentaram menor quantidade de C mineralizado (39%). A mineralização do C das raízes apresenta valores semelhantes àqueles observados para os RV da parte aérea. A mineralização do N no solo foi significativamente correlacionada com os teores de N total na MS e na fração solúvel de Van Soest dos RV da parte aérea e raízes (P < 0.01 e r2 variando de 0,90 a 0,98). Os valores de correlação entre a composição bioquímica dos RV e a mineralização do C foram menores do que aqueles observados para a mineralização do N, porém observou-se maior número de correlações significativas, com destaque para a relação C/N, polifenóis e FDN de Van Soest.

The Kinsevere mine is a copper deposit located in the Democratic Republic of Congo (DRC), within the Central African Copperbelt. This area is situated in the Katangan basin within the SE portion of the Lufilian Arc, which is a large, arcuate structure that extends from SE Angola, across the DRC, and into NW Zambia. The purpose of this study is to characterise the brittle deformation observed around the Kinsevere copper deposit to lead to an understanding of the deformation history of the area. This is accomplished by analysing fault-slip and fold data to help understand the relationship between regional palaeostress, faulting and folding present in the mine vicinity. This study also attempts to characterise fracture-controlled copper mineralisation within the interpreted geodynamic context of the area. The broader objective of this study is to relate the structural observations from Kinsevere to the deformation history of the Lufilian Arc. This study uses the right dihedral method to analyse four categories of brittle structures. The structural types analysed include slickensided faults, mineralised joints, and unmineralised joints and shear fractures. The data suggests that the palaeostress associated with the formation of brittle structures in the Kinsevere area occurred during three deformation events. The first event is characterised by a compressional stress regime which occurred during the early stage of the Kolwezian phase (D1). The second event is characterised by a strike-slip stress regime that formed as the result of clockwise rotation of the earlier (D1) compressional regime. Two fault-slip vectors were observed on the strike-slip fault planes, indicating that a reactivation occurred during the Monwezian phase (D2). The final structural event was characterised by the development of an extensional stress regime. This was associated with North-South oriented extension and is related to the East African Rift System (D3). These interpreted events correlate well with the geodynamic context related to the Lufilian orogeny. Another line of evidence that supports this structural interpretation is the presence of evaporitic minerals observed in the stratigraphic units surrounding the brecciated zones such as the RAT and the CMN. The structural association of these evaporitic minerals may be related to pre-existing, salt-bearing units, which were dissolved during an early compressive (D1) phase of the Lufilian orogeny. However, the contact between the Grey RAT and the Red RAT (distal from the breccia zones) does not show any evidence of faulting, and in the Kinsevere area the Grey RAT is always observed above the Red RAT. This suggests that the Grey RAT may be the uppermost stratigraphic unit of the RAT subgroup, which contradicts some previously published interpretations. Thus, the current structural architecture was probably formed from a combination of two separate mechanisms, including compression-related salt extrusion and the development of thrust faults and folding resulting from the shortening of the Katangan basin. Based on an analysis of the fracture-controlled mineralisation in the study area, it is shown here that most of the stress tensors indicate that these fractures were induced within the compressional stress regime generated by the Lufilian orogeny. This conclusion supports studies which suggest a multiphase origin for the mineralizing fluids active in the Katangan basin. Thus, the age of the copper mineralisation associated with fractures is interpreted to correlate with the timing of the folding event that occurred during the Lufilian orogeny between 540-550Ma. / Dissertation (MSc)--University of Pretoria, 2012. / Geology / unrestricted

Department of Mining and Environmental Geology / MESMEG

Biological hydrogels are highly promising materials for bone tissue engineering (BTE) due to their high biocompatibility and biomimetic characteristics. However, for advanced and customized BTE, precise tools for material stabilization and tuning material properties are desired while optimal mineralisation must be ensured. Therefore, reagent-free crosslinking techniques such as high energy electron beam treatment promise effective material modifications without formation of cytotoxic by-products. In the case of the hydrogel gelatin, electron beam crosslinking further induces thermal stability enabling biomedical application at physiological temperatures. In the case of enzymatic mineralisation, induced by Alkaline Phosphatase (ALP) and mediated by Calcium Glycerophosphate (CaGP), it is necessary to investigate if electron beam treatment before mineralisation has an influence on the enzymatic activity and thus affects the mineralisation process. The presented study investigates electron beam-treated gelatin hydrogels with previously incorporated ALP and successive mineralisation via incubation in a medium containing CaGP. It could be shown that electron beam treatment optimally maintains enzymatic activity of ALP which allows mineralisation. Furthermore, the precise tuning of material properties such as increasing compressive modulus is possible. This study characterizes the mineralised hydrogels in terms of mineral formation and demonstrates the formation of CaP in dependence of ALP concentration and electron dose. Furthermore, investigations of uniaxial compression stability indicate increased compression moduli for mineralised electron beam-treated gelatin hydrogels. In summary, electron beam-treated mineralized gelatin hydrogels reveal good cytocompatibility for MG-63 osteoblast like cells indicating a high potential for BTE applications.

Dans le contexte de la transition agroécologique en faveur de systèmes de culture plus économes en intrants azotés, la réintroduction des légumineuses a un rôle majeur à jouer pour atteindre la durabilité de ces systèmes. Peu de références sont actuellement disponibles sur les intérêts agronomiques et écologiques des différentes espèces, notamment à l’échelle de la rotation. Dans ce cadre, notre objectif principal consiste à mieux quantifier les flux d’azote impliqués au cours et après culture de légumineuses, et ce pour une gamme élargie d’espèces. Notre travail expérimental porte donc sur la caractérisation des flux d’azote induits dans le sol et dans les cultures de légumineuses aux caractéristiques morphologiques contrastées en parallèle de la mesure des déterminants de ces flux. Les objectifs spécifiques consistent à : i) quantifier la fixation symbiotique en fonction du niveau du stock d’azote minéral du sol, la minéralisation de l’azote des résidus de légumineuses après enfouissement et les pertes d’azote en dehors du système sol-plante (lixiviation, émission de protoxyde d’azote), ii) identifier les « traits de plantes » explicatifs des fonctions liées à ces flux d’azote. Pour atteindre ces objectifs, les différents flux d’azote ont été quantifiés au cours d’une expérimentation au champ avec implantation d’une culture de légumineuses en première année suivie par une culture de blé en année 2 qui a été menée en 2014-2015 et reconduite sur la campagne 2016-2017. En parallèle, les traits des plantes, notamment racinaires, ont été caractérisés plus finement au cours d’expérimentations conduites en conditions contrôlées / In the context of agroecological transition, the reintroduction of legume crops should play a key role in cropping system sustainability by allowing a reduction of nitrogen (N) inputs. But few references are available concerning the agronomical and ecological services provided by a wide range of legume crops, particularly within crops succession scale. Thus, the main objective of our study is to quantify the N fluxes during and after the legume crops taking into account 10 legume crops (peas, lupin, faba bean, soybean...). Our experiment consists in i) quantifying symbiotic N fixation depending on the amount of soil inorganic N, the mineralisation of N present in legume crop residues after soil incorporation and N losses outside of the soil-plant system (leaching, emission of nitrous oxide), ii) identifying plant biological traits associated to N fluxes. Thus, different N fluxes were quantified during a two-year field experiment, i.e. the first year (2014) legume crops were implanted and followed by wheat the second year (14-15) after incorportation of legume residues. This experiment was repeated in 2016-2017.In parallel, plant root traits were characterised during greenhouse hydroponic experiments

Les sols constituent le principal réservoir de carbone, avec près de deux fois plus de carbone que le pool atmosphérique. Afin de pouvoir prédire et anticiper le devenir du carbone dans le contexte actuel de changement climatique et de changement d'usage des terres, il apparaît nécessaire de mieux comprendre les processus qui régulent la décomposition des matières organiques dans les sols. Cette thèse se propose donc d'étudier deux types de régulateurs de la dynamique du carbone du sol : les propriétés de l'habitat microbien et celles des communautés microbiennes. En effet, puisque directement affectées par les changements climatiques d'une part, et les changements d'usage des terres et de pratiques culturales d'autre part, l'habitat microbien et les communautés microbiennes apparaissent comme des régulateurs clés de la dynamique du carbone du sol. Des dispositifs expérimentaux permettant de faire varier les propriétés de l'habitat microbien et celles des communautés microbiennes de façon indépendante ou simultanée ont été mis en place. Dans un premier temps, des microcosmes dont la structure du sol a été manipulée afin d'obtenir des gradients de déstructuration, ont été incubés. Dans un second temps ce sont des microcosmes mettant en jeu des gradients de diversité microbienne qui ont été incubés. Enfin, une incubation utilisant les différences naturelles de propriétés de l'habitat microbien et de communautés microbiennes a été mise en place pour tenter de hiérarchiser ces régulateurs de la décomposition des matières organiques du sol. Les résultats obtenus ont mis en évidence que l'activité microbienne de décomposition du carbone organique du sol semble plus contrôlée par les conditions environnementales (comme le pH, la texture et l'approvisionnement en substrat) que par la structure des communautés microbiennes ou leurs capacités métaboliques. En plus de cela, la fonction de minéralisation ne semble être affectée que dans le cas d'une très grande érosion de la biodiversité suggérant la présence d'un effet seuil, et que l'importance de la redondance fonctionnelle n'est pas toujours aussi grande que ce que le suggère de nombreuses études. D'autre part, dans des conditions d'aération suffisante, les mécanismes qui réguleraient la dynamique du carbone organique des sols se passeraient à des échelles très fines. / Soils represent the principal reservoir of carbon with two times as much carbon as is found in the atmospheric pool. In an effort to better predict and anticipate how soil carbon dynamics will be affected by environmental changes and by the evolution of cropping systems, it is necessary to better understand the processes that regulate soil organic matter decomposition. This study aims to investigate two regulatory mechanisms of the soil carbon dynamic: the properties of the microbial habitat and the ones of the microbial communities. Because they are directly affected by the climatic changes and by the rapid evolution of cropping systems these two mechanisms appear to have a key role in the regulation of soil carbon decomposition. Experimental designs were setup allowing the variations, independent or simultaneous, of the properties of microbial habitat and the ones of the microbial communities. First, to assess the relative importance of soil structure, microcosms with different gradient of disaggregation were incubated. Then, to assess the relative importance of diversity erosion, microcosms with microbial diversity gradient were incubated. Finally, using contrasted soils varying in their habitats and their microbial communities properties, we aimed to hierarchize these two carbon decomposition regulatory mechanisms.The obtained results indicate that microbial activity of soil organic carbon decomposition seems to be more controlled by environmental conditions (such as pH, texture and also substrate supply) than by the microbial community structure or metabolic profiles. Then we observed that organic carbon mineralisation was impacted only when the levels of diversity were very low suggesting the existence of a threshold, and that the functional redundancy is maybe not as great as numerous studies suggest. Moreover, our work showed that when conditions of aeration in the pore system are sufficient, mechanisms regulating the dynamic of soil organic carbon take place at fine spatial scales.