Добірка наукової літератури з теми "Organo-Minerals"

Pearl millet [Pennisetum glaucum (L.) R. Br.] constitutes the third most important cultivated cereal and source of nutrients in Burkina Faso. The study carried out in 2018 and 2019 at the Saria Environment and Agricultural Researches Station aimed to assess the effects of tillage and organo-mineral fertilization on the quantities of minerals accumulated in pearl millet stover that could be used in animal diets as nutritional supplements. The experimental design was a completely randomized block with a split-plot arrangement of treatments, three replications with four tillage methods assigned to main plots and eight organo-mineral fertilizations to subplots. Results showed that the quantities of minerals accumulated in pearl millet stover were affected by tillage methods and organo-mineral fertilizations as well as by their interactive effects. Compost associated with mineral fertilizers resulted in higher accumulations of minerals in pearl millet stover. In terms of tillage methods, the results indicated that ploughing and scarifying were more favorable for greater but not varying mineral accumulations compared to manual zaï and tie-ridging.

Organo-mineral complexes were obtained by treatment of aluminosilicate minerals (zeolite, bentonite and diatomaceous earth) with a primary amine (oleylamine) and an alkyl ammonium salt (stearyldimethylbenzyl ammonium chloride). The modification of the zeolite surface was carried out in two steps. The first step was treatment of the zeolite with 2M HCl. This acid treatment of the zeolite increased its affinity for neutral molecules such as surface-active amines. The second step of the modification was the adsorption of oleylamine on the acid treated zeolite. Four types of organo-mineral complexes were prepared and their anion adsorption properties were compared to those of organo-zeolite. The adsorption of sulphate bichromate and dihydrogenphosphate anions on the organo-mineral complexes was investigated. The anion adsorption measurements showed that the most efficient adsorbent for anion water pollutants was the primary amine modified H+-form zeolite.

Among the various technologies tested for removing the anionic species resulting from arsenic contamination, sorption methods have received unflagging interest. Being potential sorbent materials, clay minerals modified by cationic surfactants are often examined for this purpose. Among the clay minerals tested, information regarding sorption properties of expanded vermiculite modified with surfactants is scarce. Therefore, the present study aims to prepare organo-vermiculites modified with hexadecyltrimethylammonium (HDTMA) and benzyldimethylhexadecylammonium (HDBA) at surfactant concentrations of 0.5, 1.0, and 2.0 cation exchange capacity. Modified sorbents were identified and characterized using the analytical methods that can determine phase composition and textural properties of the samples. The sorption of As(III) and As(V) as a function of initial pH value, initial concentration of As(III, V), and initial dosage of sorbent was investigated. The results show that HDTMA and HDBA affect the properties of raw vermiculite. For instance, increase in the concentration of surfactants is often accompanied by a change in interlayer space or textural properties of vermiculite. It was observed that tested organo-minerals adsorbed As(V) to a greater extent compared to As(III). Various analytical studies were carried out and the results revealed the successful synthesis of organo-vermiculite. Moreover, the study also showed that the structure of organo-vermiculite has a significant impact on the uptake of As(III) and As(V) anions.

Abstract. An approach for nanoscale 3-D tomography of organic carbon (OC) and associated mineral nanoparticles was developed to illustrate their spatial distribution and boundary interplay, using synchrotron-based transmission X-ray microscopy (TXM). The proposed 3-D tomography technique was first applied to in situ observation of a laboratory-made consortium of black carbon (BC) and nanomineral (TiO2, 15 nm), and its performance was evaluated using dual-scan (absorption contrast and phase contrast) modes. This novel tool was then successfully applied to a natural OC–mineral consortium from mountain soil at a spatial resolution of 60 nm, showing the fine structure and boundary of OC, the distribution of abundant nano-sized minerals, and the 3-D organo-mineral association in situ. The stabilization of 3500-year-old natural OC was mainly attributed to the physical protection of nano-sized iron (Fe)-containing minerals (Fe oxyhydroxides including ferrihydrite, goethite, and lepidocrocite), and the strong organo-mineral complexation. In situ evidence revealed an abundance of mineral nanoparticles, in dense thin layers or nano-aggregates/clusters, instead of crystalline clay-sized minerals on or near OC surfaces. The key working minerals for C stabilization were reactive short-range-order (SRO) mineral nanoparticles and poorly crystalline submicron-sized clay minerals. Spectroscopic analyses demonstrated that the studied OC was not merely in crisscross co-localization with reactive SRO minerals; there could be a significant degree of binding between OC and the minerals. The ubiquity and abundance of mineral nanoparticles on the OC surface, and their heterogeneity in the natural environment may have been severely underestimated by traditional research approaches. Our in situ description of organo-mineral interplay at the nanoscale provides direct evidence to substantiate the importance of mineral physical protection for the long-term stabilization of OC. This high-resolution 3-D tomography approach is a promising tool for generating new insight into the interior 3-D structure of micro-aggregates, the in situ interplay between OC and minerals, and the fate of mineral nanoparticles (including heavy metals) in natural environments.

Les matières en suspension (MES) participent au transfert de matière des continents vers les océans. Les MES sont quantitativement issues de plusieurs sources : de l'érosion des surfaces continentales, de la remobilisation des sédiments, de l'activité biologique aquatique, et de l’activité anthropique introduisant directement des particules dans le milieu aquatique. Leur composition, leur distribution en taille et leur nature va dépendre de l’ensemble des processus qui contrôlent l’érosion, l’activité biologique ainsi que l’ensemble des activités humaines au sein d’un bassin versant. L’objectif de ces travaux de thèse est d’élaborer des systèmes modèles mimant les matières en suspension pour mieux comprendre la réactivité de ces particules naturelles. Une question se pose donc sur le choix des constituants pour modéliser ces systèmes modèles. Les travaux sur les matières en suspension de la Moselle permettent de sélectionner des constituants typiques des matières en suspension naturelles transportées par les eaux de surface sur le bassin de la Moselle et par l’Orne. Afin de reproduire la précipitation d’oxyhydroxydes de fer sur les particules d’illites, une solution de Fe(NO3)3 faiblement concentré (10-4M) pour éviter l’altération des particules d’illites sera ajouté dans une suspension d’illite et hydrolysé par une solution de KOH. La concentration et la vitesse d’addition en KOH, la méthode de titration ainsi que le rapport Fe/illite ajouté lors de cette synthèse seront étudiés. L’association entre l’illite et des polymères étant pauvre dans la littérature, il a été nécessaire dans un premier temps de préparer une série supplémentaire d'échantillons binaires illite-polysaccharides pour ensuite mieux mettre en évidence l'influence des particules de fer sur les interactions entre le polymère (Dextran ou Alginate de sodium) et les particules d’illite. Dans le cas de la formation des agrégats ternaires, il n'y avait pas de protocole établi au début de la thèse. Le travail a d’abord consisté à tester plusieurs conditions de préparation ou de synthèse, vérifier la reproductibilité et à comprendre l'influence de chaque paramètre de synthèse. Le mémoire s’articule autour de 4 parties. Une première partie est un rappel des différentes connaissances établies sur les matières en suspension, notamment leur composition et leurs origines. Une synthèse sur les matériaux présents dans les MES en tant que sujet de recherches y est également développée. Une seconde partie présente les stratégies de formation des agrégats binaires et ternaires retenues ainsi que le choix des techniques analytiques pour répondre aux objectifs. Ces stratégies reposent sur le choix fait à partir de plusieurs tests effectués lors de ces travaux. Une troisième partie traite les résultats obtenus sur la formation des agrégats binaires à base d’illite et polysaccharides. Ce chapitre détaille la formation des agrégats illite-polysaccharide en fonction de plusieurs paramètres tels que le temps d’agitation du mélange, la concentration en sel bivalent CaCl2, la concentration et le poids moléculaire du polysaccharide et le polysaccharide ajouté. Le chapitre 4 est présenté sous forme d’article scientifique en révision pour Applied Clay Science. Ce chapitre sous forme d’article scientifique en préparation, présente dans un premier temps la formation des agrégats binaire Fe-illite en fonction de plusieurs paramètres tels que la vitesse d’addition ou la concentration de KOH ajouté et la quantité de fer ajouté dans la suspension d’illite. Un rappel de certains résultats du chapitre III est également fait. Dans un second temps, la formation des agrégats ternaires est comparée à celle des agrégats binaires illite-polysaccharide. Une conclusion générale est également apportée au terme de ce mémoire, permettant de proposer quelques perspectives à ce travail
Suspended matter (SM) is involved in the transfer of matter from the continents to the oceans. TSS is quantitatively derived from several sources: erosion of continental surfaces, remobilisation of sediments, aquatic biological activity, and anthropogenic activity introducing particles directly into the aquatic environment. Their composition, size distribution and nature will depend on all the processes that control erosion, biological activity and human activities within a catchment. The objective of this thesis is to develop model systems that mimic suspended matter to better understand the reactivity of these natural particles. The question arises as to the choice of constituents to model these model systems. The work on the suspended matter of the Moselle allows the selection of constituents typical of the natural suspended matter transported by the surface waters of the Moselle basin and by the Orne. In order to reproduce the precipitation of iron oxyhydroxides on illite particles, a weakly concentrated Fe(NO3)3 solution (10-4M) to avoid alteration of the illite particles will be added to an illite suspension and hydrolysed by a KOH solution. The concentration and rate of KOH addition, the titration method and the Fe/illite ratio added during this synthesis will be studied. As the association between illite and polymers is poor in the literature, it was necessary first to prepare an additional series of binary illite-polysaccharide samples to better highlight the influence of iron particles on the interactions between the polymer (Dextran or sodium alginate) and illite particles. In the case of the formation of ternary aggregates, there was no established protocol at the beginning of the thesis. The work first consisted in testing several preparation or synthesis conditions, checking the reproducibility and understanding the influence of each synthesis parameter. The thesis is divided into 4 parts. The first part is a reminder of the different knowledge established on suspended matter, particularly its composition and origins. A summary of the materials present in suspended solids as a subject of research is also developed. A second part presents the strategies for the formation of binary and ternary aggregates as well as the choice of analytical techniques to meet the objectives. These strategies are based on the choice made from several tests carried out during this work. A third part deals with the results obtained on the formation of binary aggregates based on illite and polysaccharides. This chapter details the formation of illite-polysaccharide aggregates as a function of several parameters such as the stirring time of the mixture, the concentration of the bivalent salt CaCl2, the concentration and molecular weight of the polysaccharide and the added polysaccharide. Chapter 4 is presented as a scientific paper under review for Applied Clay Science. This chapter, in the form of a scientific article in preparation, first presents the formation of binary Fe-illite aggregates as a function of several parameters such as the rate of addition or the concentration of added KOH and the amount of added iron in the illite suspension. A reminder of some of the results of chapter III is also given. In a second step, the formation of ternary aggregates is compared to that of binary illite-polysaccharide aggregates. A general conclusion is also given at the end of this thesis, allowing us to propose some perspectives to this work

Plant roots are critical weathering agents in deep soils, yet the impact of resulting mineral transformations on the vast deep soil carbon (C) reservoir are largely unknown. Root-driven weathering of primary minerals may cause the formation of reactive secondary minerals, which protect mineral-organic associations (MOAs) for centuries or millennia. Conversely, root-driven weathering may also transform secondary minerals, potentially enhancing the bioavailability of C previously protected in MOAs. Here we examined the impact of root-driven weathering on MOAs and their capacity to store C over pedogenic time scales. I compared soil that experienced root-driven weathering, resulting in the formation of discrete rhizosphere zones in deep soil horizons (100-160 cm) of the Santa Cruz Marine Terrace chronosequence (65 ka-226 ka), with adjacent soil that experienced no root growth. Using a combination of radiocarbon, mass spectrometry, Mössbauer spectroscopy, and X-ray spectromicroscopy approaches, we characterized MOA transformations in relation to changes in C content, turnover and chemistry across four soils ranging in age (65 ka-226 ka). We found that the onset of root-driven weathering (65-90 ka) increased the amount of C associated with poorly crystalline iron (Fe) and aluminum (Al) phases, particularly highly-disordered nano-goethite. The increase in C coincided with greater overall C concentrations, longer C residence times, and a greater abundance of microbially-derived C. Continued root-driven weathering (137-226 ka) did not significantly change the amount of C associated with crystalline Fe and Al phases, but resulted in a decline in the amount of C associated with poorly crystalline metal phases. This decline in C associated to poorly crystalline phases coincided with a decrease in C concentrations and potential turnover rates, and a shift toward plant-derived C. In contrast, soil not affected by root-driven weathering showed low amounts of C bound to poorly crystalline Fe and Al phases regardless of soil age and, correspondingly, lower C concentrations and estimated residence times. My results demonstrate that root-driven formation and disruption of poorly crystalline Fe and Al phases directly controls both C accrual and loss in deep soil. Hence root impacts on soil C storage are dependent on soil weathering stage, a consideration critical for predictions of the vulnerability of deep soil C to global change.

The surface of soil colloids carries electric charges, and these surface charges are the basic cause for soil to possess a series of surface properties. Soil surface charges affect the chemical properties of the soil through varying the quantity of electric charge and the surface charge density. For example, adsorptions of cations and anions are caused by negative and positive surface charges of the soil, respectively. The amount of ions adsorbed is determined by the quantity of surface charge, whereas the tightness of adsorption is related to charge density. In addition, the migration of ions in soil, the formation of organo-mineral complexes,and the dispersion, flocculation, swelling, and shrinkage are all affected by surface charge properties of the soil. Therefore, surface charge properties have an important bearing on soil structure and plant nutrition. Variable charge soils are characterized by the high content of iron and aluminum oxides. The clay mineralogical composition is dominated by 1:1-type minerals, such as kaolinite. These two factors make the surface charge properties of variable charge soils distinctly different from those of constant charge soils of temperate regions which chiefly containin 2:1-type clay minerals. However, unlike the case for pure variable charge minerals, in variable charge soils there is generally the presence of a certain amount of 2:1-type clay minerals. Therefore, as a mixture of variable charge minerals and constant charge minerals, the surface charge properties of variable charge soils is more complicated. In this chapter, the origin and factors affecting surface charges of the soil as well as the relationship between these charges and soil type will be discussed. Despite the complexity in composition, a soil may be regarded as a mixed system consisting of constant charge surface materials and constant potential surface materials in different ratios (Anderson and Sposito, 1992; Gillman and Uehara, 1980). Examples of the former type such as montmorillonite and vermiculite carry permanent negative charges, while those of the latter type such as iron oxide and aluminum oxide carry variable charges. Commonly found constant charge clay minerals in soils include those layer silicates such as hydrous mica, vermiculite, montmorillonite, and chlorite.

The Lower Triassic Montney Formation is a major siltstone dominated unconventional tight gas play in the Western Canadian Sedimentary Basin (WCSB). In the Peace River region, the Montney Formation contains a regionally variable amount of hydrogen sulfide (H2S) in gas-producing wells with western Alberta's wells having the highest concentrations. Previous studies on the source and distribution of H2S in the Montney Formation mainly focused on variations of H2S concentration and its relationship with other hydrocarbon and non-hydrocarbon gases, sulfur isotope composition of H2S, as well as organo-sulfur compounds in the Montney Formation natural gas. None of those studies, however, focused on the role of diagenetic and geochemical processes in the formation of dissolved sulfate, one of the two major ingredients of H2S formation mechanisms, and pyrite within the Montney Formation. According to the results of this study, the Montney Formation consists of two different early and late generations of sulfate minerals (anhydrite and barite), mainly formed by the Montney Formation pore water and incursion of structurally-controlled Devonian-sourced hydrothermal sulfate-rich fluids. In addition, pyrite the dominate sulfide mineral, occurred in two distinct forms as framboidal and crystalline that formed during early to late stages of diagenesis in western Alberta (WAB) and northeast British Columbia (NEBC). The concurrence of the late-stage anhydrite and barite and various types of diagenetic pyrite with high H2S concentrations, particularly in WAB, their abundance, and spatial distribution, imply a correlation between the presence of these sulfate and sulfide species and the diagenetic evolution of sulfur in the Montney Formation. The sulfur isotope composition of anhydrite/barite, H2S, and pyrite demonstrates both microbial and thermochemical sulfate reduction (MSR and TSR) controlled the diagenetic sulfur cycle of the Montney Formation. The relationship between the delta-34S values of the present-day produced gas H2S and other sulfur-bearing species from the Montney and other neighboring formations verifies a dual native and migrated TSR-derived origin for the H2S gas with substantial contributions of in situ H2S in the Montney reservoir.