Academic literature on the topic 'Gafsa phosphate'

The raw phosphates in the Gafsa-Metlaoui phosphate basin are valorized by wet processes that are performed in the laundries of the Gafsa Phosphates Company (CPG, Gafsa, Tunisia) to reach market grades (>28% P2O5). This enrichment process allows the increase of P2O5 content by the elimination of the coarse (>2 mm) and fine (<71 µm) fractions. Mineralogical analysis has shown that all the investigated materials (raw phosphate, marketable phosphate, coarse waste, and fine waste) from the laundries of M’Dhilla-Zone L and Redeyef are both composed of carbonate fluorapatite, carbonates, quartz, gypsum, clays, and clinoptilolite. Chemical analysis shows that Cr, Cd, Zn, Pb, and U are concentrated in the fine wastes and associated with the clay–phosphate fraction. The rare earth elements are more concentrated in both raw and marketable phosphates. Drilling and sludge-water analysis, along with leaching tests conducted on the fine wastes, showed that, due to phosphate industry, cadmium, fluorine, and sulfate contributing to the pollution of water resources in the region, pollution is more conspicuous at M’Dhilla.

This article seeks to evidence the social, environmental and political repercussions of phosphate extraction and transformation on two peripheral Tunisian cities (Gabes and Gafsa). After positing the difference between class environmentalism and political ecology, it addresses the harmful effects of phosphate transformation on the world's last coastal oasis and on various cities of the Gulf of Gabes. It then sheds light on the gross social, environmental and health inequalities brought about by phosphate extraction in the mining region of Gafsa. The confiscatory practices of the phosphate industry are subsequently linked with global production and distribution chains at the international level as well as with centralized and authoritarian forms of government at the national and local level. Dispossessed local communities have few alternatives other than violent protest movements and emigration towards urban centers of wealth. Using the recent experience in self-government in the Jemna palm grove, the article ends with a reflection on the possible forms of subaltern resistance to transnational extractivism and highlights the ambiguous role of the new "democratic state" as a power structure reproducing patterns of domination and repression inherited from the colonial period and cemented under the dictatorship of Ben Ali.Keywords: political ecology, transnational extractivism, phosphate, Tunisia.

The enrichment of the low-grade-phosphate ore of the Tozeur-Nefta deposit was investigated using scrubbing-attrition, ball grinding and anionic/cationic reverse flotation in order to separate phosphate-rich particles from their gangue. The choice of the beneficiation process was based on the petrographic, mineralogical and chemical analyses. The petrographic and mineralogical studies have revealed the abundance of phosphatic (carbonate-fluorapatite-CFA) particles) coupled with carbonates (calcite, dolomite,) and silicates (quartz, illite, kaolonite) that constitute the (endo/exo) gangue of these ores. Chemical analysis has demonstrated that the raw phosphate sample contains low amounts of P2O5 (12.0%) and MgO (4.9%) and high amounts of CaO (40.7%) and SiO2 (20.5%). Microscopic observation/counting has shown that the release mesh occurs in the 71–315 μm size. Scrubbing-attrition, grinding and reverse flotation methods were applied to the +71μm fraction. Scrubbing-attrition tests of the 71–315 μm fraction have helped to improve the P2O5 grade to 15.5%. Ball-grinding tests were used to reduce the coarse fraction +315 μm. Grounded materials were sieved to 71–315 μm and combined with the scrubbed fraction in the flotation feed. Reverse-flotation tests of the phosphate-rich fraction (71–315 μm) have helped to improve the P2O5 grade to 27.1%, with a recovery rate of 92.4%.

Crops in general make poor use of phosphorous fertilizer and, as a result, recommended rates and production costs are very high. Phosphorus can be made more readily available to plants by proper management of phosphate fertilization, selecting both, type of fertilizer and application method. This study was carried out to evaluate the efficiency of the natural Gafsa rock phosphate and the triple superphosphate on dry matter production and P uptake by corn plants cultivated in a greenhouse. Fertilizers were applied localized and broadcast/incorporated on to two soils with contrasting phosphorus capacity factors (PCF). Rock phosphate broadcast application was as efficient as triple superphosphate in increasing corn plant dry matter in the Tropudult, with lower PCF. This effect was not observed on the Haplustox, owing to the lower P solubility due to the higher Ca concentration in this soil. Triple superphosphate rates increased plant P uptake in both soils and for both application forms. Rock phosphate resulted in higher P-content in plants, but only for broadcast application on the Ultisol.

The agronomic effectiveness of partially acidulated phosphate rock (PAPR) fertilizers depends on the proportion of water soluble P present and the long-term release of P from the unacidulated residual phosphate rock (water-insoluble residue) in the soil environment. The relative reactivity of water-insoluble residues in a range of partially acidulated phosphate rock (PAPR) fertilizers was assessed according to chemical solubility, and was found to be lower than the corresponding original PRs. Two causes were identified for the reduced formic acid solubility of water-insoluble residues: (i) some preferential dissolution of more reactive apatite components (i.e. higher carbonate substituted apatite) during partial acidulation as indicated by reductions in the molar apatite C:P ratio of the residual PRs compared with the corresponding original PRs, and (ii) acid-insoluble metal (Fe-Al-Mg)phosphate and/or fluoride complexes formed on the surface of residual PRs during partial acidulation with commercial-grade phosphoric acid, which were partially soluble in alkaline ammonium citrate. These two mechanisms accounted for most of the solubility differences observed for 'medium' reactive PRs (Khouribga, Arad), compared with only half for more reactive PRs (North Carolina, Gafsa). The conclusion from this study is that partial acidulation may not be an ideal method for the manufacture of fertilizers containing fast and slow release (i.e. PR) components, particularly when highly reactive PRs such as North Carolina are used.

Les techniques orientées vers le traitement des phosphates et en particulier celles relatives à la détermination de la fraction exploitable reposent actuellement sur deux procédés : l'examen au microscope et la détermination par des méthodes analytiques : chimique, physique et physico-chimique (spectrographie, rayon x, etc. ). On identifie ainsi les phases présentes (analyse qualitative) et on effectue un ensemble de mesures (analyse quantitative), tels que taille nombre de grains, pourcentage en phase, etc. Bien qu'ils fournissent des résultats satisfaisants, les deux procédés d'analyse cités ci-dessus sont très longs. Pour améliorer le temps d'exécution des analyses et éliminer la subjectivité de l'opérateur, nous proposons, dans ce mémoire, une méthode basée sur les techniques de l'imagerie numérique. Il s'agit généralement de méthodes connues du traitement de l'image qu'il conviendrait d'adapter à la spécificité de l'instrument. Cette méthode, non destructive, permet une analyse qualitative de l'échantillon de phosphate brut en lame mince, aboutissant à la différenciation des différentes phases minérales présentes et notamment la fraction phosphatée. Cette dernière sera ensuite quantifiée en utilisant les techniques de la reconstitution dans r#3 afin d'obtenir la répartition granulométrique de l'échantillon. Les étapes nécessaires pour cette analyse des données sont de conception originale puisqu'il n'existe pas à ce jour de travaux dans le domaine des techniques des phosphates pouvant être utilisés comme référence.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
In tropical conditions, the availability of phosphorus (P) in the soil for plants is one of the main limiting factors. One of the alternatives to reduce the cost of fertilization is the use of natural phosphate rock. The activity of phosphate solubilizing microorganisms is critical to use of phosphate fertilizers of low solubility. This work aimed to evaluate the changes introduced in the chemical and biological attributes of a Entisol cultivated with corn, by the application of water-soluble phosphate fertilizer, Gafsa rock phosphate and phosphatic biofertilizers. The experiment was conducted in two stages. The first step was performed to produce biofertilizers and biofertilizers in the second stage that showed better solubilization of phosphorus were used in growing corn in pots in the greenhouse The biofertilizers: poultry manure + Gafsa Phosphate (CA + FG) and bovine manure + Gafsa Phosphate (EB + FG), were produced in plastic pots with a capacity of 1000 mL over a period of 60 days. The experimental design was completely randomized in a 6 x 2 factorial with four replications, six sources of phosphorus: Gafsa Phosphate (FG), simple superphosphate (SS), poultry manure + Gafsa Phosphate (CA + FG), bovine manure + Gafsa Phosphate (EB + FG), poultry manure + single superphosphate (CA + SS), bovine manure + simple superphosphate (EB + SS) and two application forms: Incorporated (I) and surface (S). The parameters evaluated were: dry mass of roots and shoots, chemical characterization of soil and plant, biological indicators of soil phosphatase enzyme activity and identification and quantification of organic acids in the soil and rhizosphere. The results were submitted to analysis of variance and the averages of the data separated by the Scott-Knott test, at 5% probability. The lower content of P in the soil was determined by the addition of FG (8.42 mg kg-1). Fertilization with EB + FG and CA + FG so embedded produced the highest dry matter (MSPA), 10.55 and 9.20 g plant-1. The EB + FG showed the highest values of microbial biomass carbon (C-MBC), total organic carbon (COT) and microbial quotient (qMIC) and lower values of basal respiration (C-O2), metabolic quotient (qCO2), water-soluble carbon (CSA), indicating high stability of the microbial activity. The highest activity of alkaline phosphatase was verified by treating EB + SS, while the highest acid phosphatase activity was verified by treatment with EB + FG. The samples analyzed in the gas chromatograph detected the presence of acetic acid, propionic acid and butyric, with acetic more significant. In samples from the rhizosphere of corn plants were identified three low molecular weight acids, acetic, propionic and butyric acids, but in much higher concentrations than in the soil.
Em condições tropicais, a disponibilidade de fósforo (P) no solo para as plantas é um dos principais fatores limitantes da produção. Uma das alternativas para reduzir o custo com as adubações é o uso de fosfatos de rocha natural. A atividade dos microrganismos solubilizadores de fósforo é fundamental para uma utilização dos fertilizantes fosfatados de baixa solubilidade. Este trabalho teve como objetivo avaliar as alterações promovidas nos atributos químicos e biológicos de um Neossolo Regolítico, cultivado com milho, pela aplicação de fertilizante fosfatado hidrossolúvel, fosfato natural de Gafsa e biofertilizantes fosfatados. O experimento foi conduzido em duas etapas. Na primeira etapa foi realizada a produção de biofertilizantes e na segunda etapa os biofertilizantes que apresentaram melhor solubilização de fósforo foram utilizados no cultivo de milho em vasos, em casa de vegetação Os biofertilizantes: Cama de aviário + Fosfato de Gafsa (CA+FG) e Esterco bovino + Fosfato de Gafsa (EB+FG), foram produzidos em potes plásticos com capacidade de 1000 mL durante um período de 60 dias. O delineamento experimental utilizado foi inteiramente casualizado em esquema fatorial 6 x 2 com quatro repetições, sendo seis fontes de fósforo: Fosfato de Gafsa (FG), Superfosfato simples (SS), Cama de aviário + Fosfato de Gafsa (CA+FG), Esterco bovino + Fosfato de Gafsa (EB+FG), Cama de aviário + Superfosfato simples (CA+SS), Esterco bovino + Superfosfato simples (EB+SS) e duas formas de aplicação: Incorporada (I) e em Superfície (S). Os parâmetros avaliados foram: massa seca de raiz e parte aérea, caracterização química de solo e planta, indicadores biológicos do solo, atividade enzimática de fosfatase e identificação e quantificação dos ácidos orgânicos presentes no solo e na rizosfera. Os resultados obtidos foram submetidos à análise de variância, sendo as médias dos dados separadas pelo teste Scott-Knott, ao nível de 5% de probabilidade. O menor teor de P no solo foi determinado pela adição de FG (8,42 mg kg-1). A adubação com EB+FG e CA+FG de forma incorporada proporcionaram as maiores produções de matéria seca de parte aérea (MSPA), 10,55 e 9,20 g planta-1. O EB+FG apresentou os maiores valores de carbono da biomassa microbiana (C-CBM), carbono orgânico total (COT) e quociente microbiano (qMIC) e menores valores de respiração basal (C-O2), quociente metabólico (qCO2), carbono solúvel e água (CSA), indicando alta estabilidade da atividade microbiana. A maior atividade da fosfatase alcalina foi verificada pelo tratamento EB+SS, enquanto que a maior atividade da fosfatase ácida foi verificada pelo tratamento com EB+FG. As amostras de solos analisadas no cromatógrafo gasoso detectaram a presença do ácido acético, butírico e propiônico, sendo o acético mais expressivo. Nas amostras da rizosfera de plantas de milho foram identificados três ácidos de baixo peso molecular, acético, butírico e propiônico, porém em concentrações muito mais elevadas do que no solo.

Mangabeira (Hancornia speciosa) fruit is native to Brazil, and its fruit - mangaba - is widely used in agribusiness juices and ice creams. Given the growing demand for its fruit becomes imperative to cultivation of this species. Thus, it is necessary to develop farming technologies, which includes studies on fertilization. The work aimed to study the response to fertilization mangabeira planting with different sources and levels of phosphorus in soil type PSAMENT. The experiment was carried out in green- EMBRAPA, Aracaju, Sergipe. We studied two phosphorus sources (triple super phosphate and Gafsa rock phosphate) and five doses (0, 0.56, 1.12, 2.24 and 4.48 g P2O5 dm3). Observed photosynthesis, stomatal conductance, transpiration and internal CO 2, besides the production of dry matter and phosphorus content and accumulation in roots and shoots. It was concluded that the provision of high doses of phosphorus and high in acidity and concentration of aluminum substrate provided by the source superphosphate brought damage to plant development. The Gafsa rock phosphate was more efficient doque triple superphosphate as source of phosphorus for speciosa.
A mangabeira (Hancornia speciosa Gomes) é frutífera nativa do Brasil, e seu fruto - mangaba - é muito utilizado na agroindústria de sucos e sorvetes. Tendo em vista a crescente demanda por seus frutos torna-se imperativa a necessidade de cultivo desta espécie. Para tanto, faz-se necessário o desenvolvimento de tecnologias de cultivo, o que inclui estudos relativos à adubação. O trabalho teve como objetivo estudar a resposta da mangabeira à adubação de plantio com diferentes fontes e doses de fósforo em solos do tipo Neossolo Quartzarênico. O experimento foi desenvolvido em casa-devegetação da EMBRAPA, em Aracaju, Sergipe. Estudou-se duas fontes de fósforo (super fosfato triplo e fosfato natural de Gafsa) e cinco doses (0; 0,56; 1,12; 2,24 e 4,48g de P2O5 dm3). Observou-se fotossíntese, condutância estomática, transpiração e CO2 interno, além da produção de massa seca e teor e acúmulo de fósforo no sistema radicular e na parte aérea. Concluiu-se que a disponibilização de doses excessivas de fósforo e a elevação da acidez e dos teores de alumínio do substrato, proporcionados pela fonte superfosfato triplo trouxeram prejuízos ao desenvolvimento das plantas. O fosfato natural de Gafsa foi mais eficiente doque o superfosfato triplo, como fonte de fósforo para a mangabeira.

A eficiência do fosfato natural (FN) pode ser melhorada se aplicado junto com uma fonte de elevada solubilidade em água. O presente trabalho constou de quatro experimentos realizados em casa-de-vegetação do Laboratório de Fertilidade do Solo do CENA/USP, nos quais cultivaram-se plantas de milho (Zea mays L.) e de soja [Glycine max (L.) Merr.] em amostras de um Latossolo Vermelho Amarelo distrófico utilizando-se o método da diluição isotópica de 32P para: a) verificar se o efeito de uma fonte de P de elevada solubilidade em água no aumento da disponibilidade do P do FN é fisiológico (disponibilidade inicial de P) ou químico (acidificação), b) avaliar o efeito das doses e das proporções das misturas de superfosfato triplo com fosfatos naturais, e c) comparar a eficiência do fosfato natural de Patos de Minas com o de Gafsa aplicados com o SFT. As fontes de P usadas foram o superfosfato triplo (SFT) como fonte padrão e fosfatos naturais (FNs) de Patos de Minas e de Gafsa. A aplicação de uma fonte de P solúvel em água juntamente com fosfato natural melhorou o aproveitamento do fósforo do FN tanto pelo milho como pela soja, embora esse efeito seja pequeno para o fosfato natural de Patos. Para o milho, a simples presença de P na forma solúvel em água na fase inicial de desenvolvimento não melhorou o aproveitamento do P da fonte natural, provavelmente por causa do menor período de tempo de desenvolvimento das plantas em relação à soja, no qual efeito foi significativo. A compactação do FN de Gafsa com SFT aumentou o aproveitamento do P do FN para o milho comparado à aplicação deste localizado no solo e na soja esse efeito foi maior obtendo aproveitamento superior ao do FN de Gafsa misturado ao solo. Assim, a maior utilização do P do FN pela soja ocorreu tanto pelo efeito químico quanto fisiológico. A aplicação localizada do SFT proporcionou resultado melhor do que quando este fertilizante foi misturado ao solo, ocorrendo o contrário para o fosfato natural. As doses de fósforo aplicadas com as misturas de superfosfato triplo com os FNs não afetaram o aproveitamento do P do fosfato natural pelo milho e pela soja, enquanto que o aumento do SFT nas proporções das misturas aumentaram significativamente o aproveitamento do P dos fosfatos naturais. Ao contrário do FN de Patos, o aproveitamento de P do FN de Gafsa quando misturado na proporção 80 SFT: 20 FN, na soja, foi tão eficiente quanto o SFT aplicado sozinho.
The efficiency of phosphate rock (PR) can be improved applying it together with watersoluble P fertilizer. Four experiments were carried out in the greenhouse of the Soil Fertility Laboratory, CENA/USP (Centro de Energia Nuclear na Agricultura - Universidade de São Paulo), with maize (Zea mays L.) and soybean [Glycine max (L.) Merr.] grown in a dystrophic Typic Haplustox using 32P dilution technique to: a) verify if the increasing effect of water-soluble P source on PR phosphorus availability is physiological (initial higher P availability) or chemical (acidification), b) evaluate the effect of rate and proportion of triple superphosphate (TSP) mixed with PR, and c) compare the efficiency of Patos de Minas with of Gafsa PR applied with TSP. The P sources utilized were the TSP as standard P source and Patos de Minas and Gafsa PR. The application of a water-soluble P source improved the PR phosphorus utilization efficiency by maize and soybean, although this effect was small for the Patos PR. For maize, the simple presence of P in water-soluble form at initial stage of plant growth did not increase the PR phosphorus utilization, probably due to the short growing period in relation to soybean, in which the effect was significant. The compaction of Gafsa PR with TSP increased the absorption of PR P by maize plants. Compared to its localized application in the soil this effect was bigger in soybean plants, obtaining better efficiency than the Gafsa PR mixed in the soil. Therefore, the increased PR P utilization by soybean plants occurred by both chemical and physiological effect. The localized application of TSP promoted better results than when this fertilizer was mixed in the soil, unlike with PR. The increasing rate of P applied in mixed form (TSP and PR) did not affect the PR P utilization by the crops, while the increasing proportion of TSP in the mixture increased the absorption of PR P. The Gafsa PR, when mixed with TSP in proportion 80 TSP: 20 PR, was as efficient as the TSP applied sole.

L'etude porte sur deux types de matiere organique: l'une provient des sediments argileux et phosphates du bassin de gafsa-metlaoui en tunisie, l'autre est une serie de charbon presentant tous les stades de houillification et provenant du bassin houiller lorrain. On utilise la spectrometrie de resonance paramagnetique electronique et la spectrometrie infra-rouge a transformee de fourier (irtf) afin de determiner les groupements presents et la structure du materiau

Les travaux antérieurs ayant porté sur la géochimie des séries phosphatées tunisiennes ont montré que celles-ci étaient constituées d alternances de strates richement phosphatées et de strates intercalaires stériles. Les strates phosphatées sont, elles-mêmes, constituées d un sédiment argilo-carbonaté de faciès épicontinental, servant de matrice à des grains phosphatés (pellets). La reprise des études géochimiques de ces séries a montré que la matière organique (MO) des matrices argilo-carbonatées des pellets et des intercalaires est un "kérogène" dont l état d évolution est normal pour des strates d environ 50 Ma (Yprésien) n ayant jamais été enfouies. La MO des pellets est, par contre, tout à fait singulière pour cet âge car de type "humique" (humus marin et non pas continental). Cette MO, d origine phytoplanctonique, est profondément altérée par des populations microbiennes, notamment sulfato-réductrices et son évolution a été bloquée au stade humique. Les pellets phosphatés apparaissent ainsi comme des corpuscules "étrangers" à leur matrice, tant sur le plan pétrographique que chimique. Ces corpuscules n ont aucun caractère authigène au sein de leur matrice. La seule explication susceptible de rendre compte de leur présence, et de leur composition, est qu il s agisse de pelotes fécales de poissons carnivores/piscivores. La séquence des événements allant de la formation de fèces richement phosphatées dans l intestin de tels poissons jusqu à leur enfouissement et à leur fermeture géochimique au sein du sédiment. Les obligations imposées aux fèces au cours de leur formation dans l intestin de tels poissons, de leur transport et de leur sédimentation, pour que la chaîne de fossilisation aboutisse à la préservation de pellets phosphatés intacts, depuis 50 Ma, et contenant une MO fragile et réactive, sont de natures physiques, chimiques et microbiennes.