L’objectif de cette étude est de reconstruire le régime de l’érosion des chaînes himalayennes, et de relier ces paramètres aux variations climatiques globales et à l’intensité de la mousson. Dans ce travail, Les sédiments de 3 carottes prélevées dans la baie du Bengale pendant la mission MONOPOL ont fait l’objet d’analyses minéralogiques (XRD et granulométrie) et géochimiques (majeurs, traces, la composition isotopique du Nd et du Sr). La mise en âge des carottes, est basée sur les enregistrements de δ¹⁸O de foraminifères planctoniques (G. ruber), et des datations au ¹⁴C (AMS). Ces 3 enregistrements sédimentaires couvrent les derniers 180 ka. L'approche multi-traceur menée sur ces carottes, nous donne des informations essentielles sur les sources, afin de reconstruire les changements au cours du temps des sédiments transportés vers la partie proximale du cône sous-marin du Bengale, et de mieux comprendre ses liens potentiels avec les changements climatiques (mousson indienne et/ou des changements au niveau de la mer). Les résultats de cette étude, donnent également des clefs sur les processus d'altération chimique et de la dynamique du transport des sédiments au cours du temps. En outre, une étude à haute résolution, sur un site localisé sur la levée du chenal actif du cône sous-marin fournit des informations sur les changements dans le degré d'altération et la dynamique de transport des sédiments du système himalayen au cours de l'Holocène. Ainsi, il est possible de quantifier l'impact de la mousson d’été sur la sédimentation au niveau de la levée durant cette période climatique. Les résultats de cette étude ont été utilisés pour estimer les changements dans les sources sédimentaires (plaine Indo-Gangétique vs haute-chaine) et retracer l'altération chimique du matériel détritique au sein du bassin versant du système fluviatile du Ganges-Brahmapoutre. / The aim of this study is to reconstruct the erosional history of the Himalayan ranges, in order to connect these parameters to global climatic events and variations in the intensity of the monsoon. In this work, sediments from 3 marine cores collected in the Bay of Bengal, during the MONOPOL cruise were analyzed using mineralogical (XRD and grain-size) and geochemical (major, trace, Nd and Sr isotopic composition) methods. Chronological framework of studied cores were based on δ¹⁸O from planktonic foraminifera (G. ruber), and ¹⁴C ages dating (AMS). These cores cover the last 180 kyr. The multi-proxy approach conducted on these cores, gives us critical information about the source, to reconstruct the temporal variability of sediment export to the proximal northeastern Bengal Fan and its potential links to climatic changes (Indian monsoon and/or sea-level changes). Results also give insights on the chemical weathering processes and the dynamic of transport of the sediments through time as well. Moreover, a high-resolution study, on a site located on the active middle fan channel levee of the fan provides information on changes in the weathering pattern and the dynamic of transport of sediments from the Himalayan system during the Holocene. Thus, it is possible to quantify the impact effect of summer monsoon rainfall during that time interval. These results have been used to assess changes in the sedimentary sources (Indo-Gangetic plain vs highlands) and document the chemical weathering states of the detrital material within the Ganges-Brahmaputra river basin catchment.

PhDENV / Department of Ecology and Resource Management / Kaolin dominated soils are common in the tropical and subtropical regions. People depend on kaolin-rich soils for agricultural production of food and fiber. The most popular of all South African soils is the Hutton form which accounts for the marvelous redness of the landscape across the Country. The apedal (structureless) soils in the group are characterised by a relatively low CEC (< 11 cmolc kg-1) reflecting oxidic mineralogy with predominantly kaolinitic assemblage. The geochemical and mineralogical composition of soil kaolin has significant implications on soil fertility, geochemical exploration and engineering properties. Despite the dominance of kaolin in these soils, little is known of their properties in the medium. The nature of kaolin minerals in soils varies with parent material, degree of weathering and pedogenic environment. Most studies conducted in South Africa on kaolins are limited to reference kaolins with little or no publication on soil kaolins, hence, this study. This research involved the evaluation of mineralogical and geochemical characteristics of oxidic soils and soil kaolins developed from four (4) selected parent rocks which were basalt, granite, arkosic sandstone, and gneiss. Soils developed from quartzite were selected as control. Representative soil samples collected from profiles developed from the different parent rocks were analysed for physico-chemical, mineralogical, and geochemical data. The mineralogical and geochemical data obtained by x-ray diffractometry (XRD), x-ray fluorescence (XRF), and laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) were used in unraveling the influence of the provenance and degree of weathering on the soil characteristics. The mineralogical and geochemical data for soil kaolins were determined through XRD, scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis and differential scanning calorimetry, XRF, and LA-ICPMS to establish their mineralogical and geochemical properties with respect to their parent rocks. Comparison between the soil kaolins and selected reference kaolins were also conducted. The phosphorus (P) sorption data acquired photometrically were employed to evaluate the relationship between the P sorption capacities of the soils and soil kaolins. The influence of soil properties on the fertility of the soils were assessed based on the physico-chemical (pH, particle size distribution, and electrical conductivity (EC)) and chemical (organic matter (OM) content, cation exchange capacity (CEC), available P, exchangeable cations (Ca, K, Mg, Na, and Al), and P sorption) data. The mineralogical and geochemical data for the parent rocks were obtained by XRD, optical microscopy, XRF, and LA-ICPMS. Multivariate statistical analyses were also conducted. Results showed that the dominant colour in the studied bulk soils was dusky red (31 %) followed by brown (23 %), reddish brown, yellowish red, and yellowish brown (23 %) as well as strong brown, dark brown, reddish grey, very dark greyish brown, and dark red. Soil textures were clayey to sandy loamy with OM contents between 0.41 and 4.76 %. The pH, EC, CEC, exchangeable cations, and available P values generally ranged from 5.22 to 8.38, 10.25 to 114.40 μS/cm, 2.93 to 18.30 cmol/kg, 0.03 to 13.92 cmol/kg, and <0.01 to 54.99 mg/kg, respectively. Kaolinite and quartz were the dominant phases for soils developed from basalt whereas, quartz and plagioclase were the dominant mineral phases in soils developed from granite, arkosic sandstone, and gneiss, respectively. Other minerals present in the soils were microcline, muscovite, hematite, goethite, montmorrillonite, anatase, gibbsite, chlorite, and actinolite. Geochemical compositions of the bulk soils show relative enrichment of Fe2O3, TiO2, CaO, K2O, MgO, MnO, and Na2O (except for CaO, K2O, MgO, MnO, and Na2O in soils developed from basalt). Chemical index of alteration (CIA), chemical index of weathering (CIW), and plagioclase index of alteration (PIA) values varied between 54.92 and 99.81 % which suggest low to high degree of chemical weathering. The ACN-K and A-CNK-FM diagrams for the different soils also support these observations. Trace elements were generally enriched in soils developed from basalt and gneiss (except for Rb, Sr, and Ba in soils developed from basalt), but were depleted in soils developed from granite and arkosic sandstone (except for Cr and Ta). The principal factors responsible for the mineralogical and geochemical characteristics of the soils were the parent rocks and degree of weathering. In the soil kaolins, the dominant clay mineral was kaolinite accounting for 23 to 85 wt % followed by montmorrillonite, chlorite, and gibbsite. The non-clay minerals like quartz, plagioclase, muscovite, microcline, anatase, goethite, hematite, and actinolite accounted for the remaining percentages. The soil kaolins were characterised by thin platy kaolinite particles with partially to poorly-ordered structural order. The platy kaolinite crystals have their longest dimension sizes between 0.06 and 0.25 μm. The dehydroxylation temperatures for the studied soil kaolins ranged from 425 to 475 ˚C. The SiO2/Al2O3 ratio was lowest in soil kaolins developed from basalt and higher in soils developed from granite, arkosic sandstone, and gneiss which is consistent with their mineralogy since the former have more kaolinite. Higher Fe2O3 and CEC values were obtained relative to reference kaolins which could be attributed to the presence of more structural iron in the soil kaolins as well as their smaller crystal sizes. The presence of weatherable and accessory minerals accounted for the enrichment of Co, Ni, Cu, Zn, and Pb in the soil kaolins. The kaolinite in the soils were formed by leaching and desilication of the primary minerals in the parent rocks under suboxic conditions. H-type P adsorption isotherms obtained for both the soils and soil kaolins indicated their high affinity for phosphorus by chemisorption. The average maximum P adsorption values were in decreasing order of soils developed from basalt > granite > arkosic sandstone > quartzite (control) > gneiss, respectively whereas, for soil kaolins is basalt > granite > quartzite (control) > arkosic sandstone > gneiss, respectively. Relative to other soils developed from different parent rocks, soils developed from basalt (with more clay content) had higher capacity and buffer power for P adsorption. The standard P requirements for the soils ranged from 7.78 to 92.91 mgP/kg and were classified as low based on the Langmuir model. Significant correlation between the P adsorption parameters for the soils and soil kaolins indicated that the later could be taken as a good predictor for P sorption dynamics in the soils. Electrical conductivity of the soils were taken to be negligible in interfering with plant growth. The available P values were generally below the critical level of 12 – 15 mg/kg for soils developed from basalt, gneiss, and quartzite (control) but higher in soils developed from granite and arkosic sandstone. All the soil evaluation factor (SEF) average values estimated were greater than five indicating that they are not of poor soil fertility. The correlation results between the soil properties and P sorption parameters suggest that several variables can influence the P sorption dynamics of the soil. Regression analyses further indicated that CEC, pH, OM, and clay content in the soils account for 99 % bounding P energy variation whereas, Fe2O3 accounts for 76 % P sorption maximum variation in the soils. In addition, variations in Fe2O3 and sand contents in the soils account for 96 % and 95 % maximum buffering capacity and external P requirement (EPR) variations, respectively. Models to advance the interplay between the various soil properties and P sorption parameters in the soils were developed. Mineralogical and geochemical characteristics of the soils were principally controlled by the parent rocks and degree of weathering. The soil kaolins displayed significant differences relative to reference kaolins. Langmuir model is most suited for describing P sorption in soils and soil kaolins developed from different parent rocks within the studied area. P sorption parameters for the soils can readily be obtained from the P sorption parameters of the kaolins present in them. EPR obtained and models for predicting P sorption parameters from selected soil properties developed for the various soils will improve the efficiency of routine P fertilizer applications. Iron oxide (Fe2O3) played the most crucial role in explaining the P sorption dynamics of the soils. The major contributions from this study have been: better understanding of the influence of parent rock characteristics and degree of weathering on the soil characteristics, the nature of soil kaolins and its influence on soil properties as well as P sorption dynamics in soils have been better established, and improvement of the understanding on the relationship between soil properties and P sorption dynamics in the soils. / NRF

Soil carbon is the largest sink and source of the global carbon cycle and is disturbed by several natural, anthropogenic, and environmental factors. The global increase of atmospheric CO2 affects soil carbon cycling through varied biogeochemical processes. The first chapter is a compilation of current information on potential factors triggering soil acidification and weathering mechanisms under elevated CO2 and their consequences on soil inorganic carbon (SIC) pool and quality. Soil water content and precipitation were critical factors influencing elevated CO2 effects on the SIC pool. The second chapter examines a detailed column experiment in which six soils from the state of Mississippi, USA, representing acidic, neutral, and alkaline pH, were exposed to different CO2 enrichments (100%, 10%, and 1%) for 30 days. The leachates’ pH tended to attain an equilibrium state (neutral) with time under CO2 saturation. SIC increased under CO2 saturation, whereas cation exchange capacity (CEC) showed a decreasing pattern in all soils. In the third chapter, an eXplainable artificial intelligence (XAI) was performed to visualize the different forms of soil carbon variability across the Mississippi River Basin area. This model explains key insights and local discrepancies, suggesting a solution to the “Black-Box” issue. The best performing model, stack ensemble, showed improved RMSE (3 to 8%) and spatial variability for soil carbons than other ML models, especially after adding the residuals from regression analyses. Land cover type > soil pH > total nitrogen, > NDVI were identified as the top four crucial factors for predicting SOC when bulk density > precipitation, soil pH > mean annual temperature described SIC. The proposed automatic machine learning (AutoML) model with model agnostic interpolations might be a hallmark to mitigate the C loss under adverse climate change conditions and allow diverse knowledge groups to adopt a new interpretable ML algorithm more confidently. Findings from this study help predict the impact of elevated atmospheric CO2 on soil pH, acidification, and nutrient availability and develop strategies for sustainable land management practices under a changing climate.

CO2 is a greenhouse gas which is significantly emitted by agricultural soils through the decomposition of plant residue and soil organic carbon. Carbon isotopes can be used in determining the source of the CO2, origin of the carbon, and the age of the CO2 emissions. This study investigates the transport of CO2 gas through agricultural soils using carbon isotopes 14C and 13C to complement concentration and production rate measurements in two comparative agricultural settings in Eastern Ontario, one of which has been modified by clearing and dredging of the adjacent riparian zone and one left undredged. Traditional radiocarbon dating measures time through loss by decay, while recent dating is based on matching measurements with the atmospheric 14CO2 signal (F14C) generated by nuclear bomb testing in the 1950s and 1960s. CO2 emissions were analyzed from soil core sections together with soil-probe gas samples and surface flux chamber samples collected from the study area. Soil cores were collected from 0- 90 cm at 7.5 cm increments and placed into IsoJar® microcosms for a period of one month. CO2 in-growth was monitored to provide production rates and samples for 14C and 13C analysis. The radiocarbon data for the microcosms showed that values increase with depth from the current fraction modern value of 1.00 F14C at the surface to an attenuated peak of 1.04 F14C at a depth of 30 to 40 cm and then decrease to values below 1.00 F14C. The data collected from the soil-probe gas showed a significant depletion in comparison to the microcosms and the surface chambers. The soil cores were subsequently analyzed by a selective leach oxidation protocol to sample decreasingly labile solid organic carbon. This involved placing the weighed soil samples into MilliQ water for 24 hours, before being passed through two sieves, 63 microns and 0.45 microns. The DOC leachate was collected and analyzed for 14C and 13C. The two solid soil fractions were then dried, treated with HCl to remove carbonate and then oxidized under vacuum with 5% H2O2 yielding CO2 and residual soil carbon for 14C and 13C. The radiocarbon analysis of these variously labile fractions, together with the microcosm and soil probe measurements, demonstrate that surface emissions at both sites are greatly dominated by CO2 from recently-sequestered labile organic carbon from the upper 30 cm with minor contribution from earlier, bomb-pulse carbon or from deeper pre-bomb carbon. No significant difference in age of emissions between the dredged and undredged sites was found.

Submitted by Biblioteca de Pós-Graduação em Geoquímica BGQ (bgq@ndc.uff.br) on 2016-05-02T17:58:54Z No. of bitstreams: 1 GALLOTTA_30_06_14.pdf: 62695484 bytes, checksum: 33335ee3affc2bcffb11fc10caf9ae3f (MD5) / Made available in DSpace on 2016-05-02T17:58:54Z (GMT). No. of bitstreams: 1 GALLOTTA_30_06_14.pdf: 62695484 bytes, checksum: 33335ee3affc2bcffb11fc10caf9ae3f (MD5) / Universidade Federal Fluminense. Instituto de Química. Programa de Pós-Graduação em Geociências-Geoquímica. Niterói, RJ / Os hidrocarbonetos presentes no ambiente consistem em misturas complexas de compostos derivados de múltiplas fontes. Os combustíveis fósseis representam a principal contribuição, devido à taxa e escala espacial, em que o petróleo tem sido usado como fonte de energia e matéria-prima para a indústria química. O objetivo deste estudo foi avaliar os níveis de concentração e identificar fontes de hidrocarbonetos na Bacia do Alto Iguaçu e, em especial, na área de influência da Refinaria Presidente Getúlio Vargas (REPAR). Além dos fatores de poluição crônica, a área de estudo foi alvo de um derrame acidental de petróleo em julho de 2000. Diversos indicadores em diferentes compartimentos ambientais (água superficial, sedimento, solo e água subterrânea) foram avaliados na fase pós-derrame e no monitoramento ambiental ao longo de várias campanhas por mais de uma década. Os esforços de avaliação foram concentrados nos seguintes indicadores: os nalcanos, os alcanos isoprenoides, os hidrocarbonetos policíclicos aromáticos (HPA), os biomarcadores de petróleo e ainda o total de hidrocarbonetos de petróleo (THP). Os resultados identificaram como principal aporte de matéria orgânica para as águas superficiais dos rios Barigüi e Iguaçu, os fluxos materiais originados em região a montante do acidente, refletindo a contribuição antropogênica crônica da cidade de Curitiba. Em 2007 e 2008, as concentrações de THP e HPA nas águas superficiais e sedimentos dos rios Barigüi e Iguaçu refletem uma expressiva melhoria nas condições desses rios em relação a 2000. Na área interna da refinaria (Ponto Zero), observou-se uma nítida diminuição (atenuação) natural das concentrações de THP no solo em todas as profundidades dos perfis amostrados ao longo do tempo nos Banhados 1 e 4 e, em particular, uma diminuição importante das concentrações entre 2004 e 2007. Para a identificação das fontes de hidrocarbonetos foram utilizadas razões diagnósticas e quimiometria. As razões diagnósticas calculadas a partir de concentrações de HPA sugeriram que, na maioria dos sedimentos dos Rios Barigüi e Iguaçu coletados nas campanhas de 2000 e 2001, a fonte petrogênica é a principal. Somente na estação a montante do acidente no Rio Barigüi, a fonte pirolítica predominou nestas duas campanhas. As razões diagnósticas que apresentaram maior eficiência na identificação de fontes de hidrocarbonetos nos sedimentos dos rios Barigüi e Iguaçu foram: ΣC1-Fenantrenos/Fenantreno; e (ΣHPA parentais de 3-6 anéis)/(Σ5 séries de HPA alquilados). A identificação de fontes através de razões diagnósticas calculadas a partir de áreas e alturas de picos cromatográficos demonstrou sua aplicabilidade verificando a relação entre os compostos encontrados em amostras de solo da área interna da refinaria com a amostra de petróleo derramado no acidente, após quase uma década da ocorrência do vazamento. A identificação de fontes através método de quimiométrico baseado na análise de componentes principais (ACP) de seções pré-processadas e combinadas dos Cromatogramas de Íons Selecionados (CIS) mostrou que as amostras mais contaminadas estão na área interna da refinaria. Essas amostras apresentam um padrão de distribuição petrogênica e diferentes graus de intemperismo. As amostras da área externa à refinaria (Guajuvira, General Lúcio e Balsa Nova) são menos ou não contaminadas e/ou contém uma mistura de contribuições diagenéticas, pirolíticas e petrogênicas onde predominam diferentes proporções. Os locais mais distantes da atividade industrial (Balsa Nova) contem, como esperado, os níveis mais baixos de contaminação por HPA. Os resultados de biomarcadores demonstraram que não há evidências para concluir que as amostras da área externa à refinaria e o óleo Cusiana vazado tenham a mesma origem. Os resultados ao longo dos rios Barigüi e Iguaçu e do Ponto Zero demonstraram que as ações de emergência para a contenção do óleo foram adequadas para os rios, e que a contaminação decorrente do derrame ficou predominantemente contida no Ponto Zero e diminuiu significativamente após uma década. / Hydrocarbons present in the environment consist of complex mixtures of compounds derived from multiple sources. The main contribution lies on fossil fuel inputs due to the rate and spatial scale by which petroleum has been used as an energy source and chemical feedstock. The aim of this study was to assess the concentration levels and identify sources of hydrocarbons in the Upper Iguaçu Watershed and, in particular, in the area of influence of the President Getulio Vargas Refinery (REPAR). In addition to the factors of chronic pollution, the study area was the scenario of an acute accidental oil spill in July 2000. Numerous indicators in different environmental compartments (surface water, sediment, soil and groundwater) were assessed in the post spill phase and during the environmental monitoring programs over the course of several campaigns for more than a decade. Assessment efforts were concentrated on the following indicators: n-alkanes, alkanes isoprenoids, polycyclic aromatic hydrocarbons (PAH), petroleum biomarkers and total petroleum hydrocarbons (TPH). The results identified as the main contribution of organic matter to surface waters of the Barigüi and Iguaçu Rivers the materials flows originated in the region upstream of the accident, reflecting chronic anthropogenic contribution of the city of Curitiba. In 2007 and 2008, the TPH and PAH concentrations in surface waters and sediments of the Barigüi and Iguaçu Rivers revealed a significant improvement in the conditions of these rivers when compared with 2000. Inside the refinery area (Point Zero), it was observed a clear natural decrease (attenuation) of the concentrations of TPH in the soil at all depths sampled over time in Marshes 1 and 4 and, in particular, an important decrease of concentrations between 2004 and 2007. Diagnostic ratios and chemometrics were used to identity hydrocarbon sources. The diagnostic ratios calculated from the concentrations of PAH suggested that, in the majority of sediments from the Barigüi and Iguaçu Rivers collected in 2000 and 2001 campaigns, the main source is petrogenic. Only in the station upstream the accident in the Barigüi River, the pyrolytic source predominated in these two campaigns. The diagnostic ratios that presented higher efficiency in identifying sources of hydrocarbons in sediments of the Barigüi and Iguaçu Rivers were: ΣC1- Phenantrenes/Phenanthrene; and (Σ3-6 rings parental PAH)/(Σ5 alkylated PAH series). The source identification through diagnostic ratios calculated from heights and areas of chromatographic peaks demonstrated its applicability establishing a relationship between the compounds found in soil samples of the internal area of the refinery and the sample of the oil spilled in the accident, after nearly a decade of occurrence of the spillage. The source identification through chemometric method based on principal components analysis (PCA) of preprocessed and combined sections of Selected Ion Chromatograms (SIC) showed that the most contaminated samples are inside the refinery area. These samples present a petrogenic pattern and different weathering degrees. Samples from outside the refinery area (Guajuvira, General Lúcio e Balsa Nova) are either less or not contaminated, and/or contain mixtures of diagenetic, pyrogenic and petrogenic inputs where different proportions predominate. The locations farthest away from industrial activity (Balsa Nova) contain, as expected, the lowest levels of PAH contamination. The biomarkers results do not show any evidences to conclude positive matches between the samples from outside the refinery area and the spilled Cusiana oil. The results along Barigüi and Iguaçu rivers and Point Zero demonstrated that emergency actions to contain the oil were appropriate for the rivers, and that the contamination resulting from the spill was mostly contained in the Point Zero and decreased significantly after one decade