The work presented in this dissertation focuses on + 4 NH in marine sediments and attempts to elucidate some of the specific pathways and processes affecting + 4 NH in coastal marine regions. The majority of work was conducted in the Laguna Madre estuary. A major feature of the estuary is the Gulf Intracoastal Waterway (GIWW) connecting the Lower Laguna Madre to Baffin Bay. Establishment of the GIWW has altered the hydrodynamics of the estuary, reduced seagrass coverage and increased sediment mobility resulting in frequent maintenance by the U.S. Army Corp of Engineers. GIWW sediment relocation associated with dredging is investigated to determine potential influence of + 4 NH release during resuspension. GIWW sediments are characterized by extremely high concentrations of porewater and exchangeable + 4 NH as well as reducing ions (millimolar HS-), and significant release hours to days after resuspension was observed during laboratory experiments. Using sediment + 4 NH porewater and exchangeable quantities, release potentials are calculated for a dredging event conducted in 1989 and results indicate that potential release from the dredging event are comparable to monthly inputs from intact GIWW and seagrass sediments. Reducing condition influence on + 4 NH adsorption dynamics was tested through resuspension experiments over a wide range of initial bulk concentrations in laboratory determined redox conditions. Significant increase in + 4 NH adsorption was observed in anoxic conditions. Calculations of the apparent partition coefficient (K*) were determined to be affected as well and implications to diagenetic models is explored. Observations in the laboratory were tested in field monitoring. Analysis of wind measurements established strong potential for interaction with sediments over the collection period. Measurements of water column + 4 NH , total suspended solids, and chlorophyll exhibited highest concentrations and correlation in areas close to the GIWW. Concentration measurements were combined with flux measurements in a model system designed to integrate field observations. Several model cases were considered including and excluding sediment resuspension. Model simulations including sediment resuspension maintained water column concentrations similar to field observations.

The work presented in this dissertation focuses on + 4 NH in marine sediments and attempts to elucidate some of the specific pathways and processes affecting + 4 NH in coastal marine regions. The majority of work was conducted in the Laguna Madre estuary. A major feature of the estuary is the Gulf Intracoastal Waterway (GIWW) connecting the Lower Laguna Madre to Baffin Bay. Establishment of the GIWW has altered the hydrodynamics of the estuary, reduced seagrass coverage and increased sediment mobility resulting in frequent maintenance by the U.S. Army Corp of Engineers. GIWW sediment relocation associated with dredging is investigated to determine potential influence of + 4 NH release during resuspension. GIWW sediments are characterized by extremely high concentrations of porewater and exchangeable + 4 NH as well as reducing ions (millimolar HS-), and significant release hours to days after resuspension was observed during laboratory experiments. Using sediment + 4 NH porewater and exchangeable quantities, release potentials are calculated for a dredging event conducted in 1989 and results indicate that potential release from the dredging event are comparable to monthly inputs from intact GIWW and seagrass sediments. Reducing condition influence on + 4 NH adsorption dynamics was tested through resuspension experiments over a wide range of initial bulk concentrations in laboratory determined redox conditions. Significant increase in + 4 NH adsorption was observed in anoxic conditions. Calculations of the apparent partition coefficient (K*) were determined to be affected as well and implications to diagenetic models is explored. Observations in the laboratory were tested in field monitoring. Analysis of wind measurements established strong potential for interaction with sediments over the collection period. Measurements of water column + 4 NH , total suspended solids, and chlorophyll exhibited highest concentrations and correlation in areas close to the GIWW. Concentration measurements were combined with flux measurements in a model system designed to integrate field observations. Several model cases were considered including and excluding sediment resuspension. Model simulations including sediment resuspension maintained water column concentrations similar to field observations.

No description available.

No description available.

In saline soils, which are characterized by an appreciable quantity of neutral soluble salts, plant growth is adversely affected due to the increase in osmotic pressure and the consequent decrease in the physiological availability of water. In addition, growth may also be restricted through the accumulation of toxic quantities of various ions within the plant.

Orientador: Silvio José Bicudo / Banca: Dirceu Maximino Fernandes / Banca: Helio Grassi Filho / Banca: Ciniro Costa / Banca: Ricardo Augusto Dias Kanthack / Resumo: A busca por uma agricultura ecologicamente sustentável e economicamente viável vem aumentando ao longo dos anos. Neste sentido, sistemas de cultivo que visam à maximização do uso do solo e dos insumos agrícolas têm ganhado, cada vez mais, espaço na agricultura brasileira. O objetivo deste trabalho foi avaliar a resposta do milho cultivado sob cobertura vegetal de Brachiaria brizantha a doses crescentes de potássio, em cultivo solteiro e em sistema de integração lavoura-pecuária (milho consorciado com Brachiaria brizantha). O experimento foi conduzido na Fazenda Experimental Lageado da FCA/UNESP, em Botucatu-SP, nos anos agrícolas de 2007/2008 e 2008/2009. O experimento consistiu de 16 tratamentos estabelecidos em esquema de blocos casualisados com parcelas subsubdivididas em quatro repetições, tendo a área de cada subsubparcela 35 m2 (5 x 7 m). Cada dose de K2O (0, 75, 150, 225 kg ha-1) correspondeu a uma parcela, sendo as subparcelas formadas pela presença ou ausência de Brachiaria brizantha cultivada no ano agrícola de 2007/2008 como planta de cobertura, as subsubparcelas foram compostas por dois sistemas de cultivo (milho solteiro e milho consorciado com Brachiaria brizantha). As doses de K2O e os sistemas de cultivo só foram implantados no ano agrícola de 2008/2009. Durante o período de florescimento da cultura do milho foram tomadas medidas da altura de plantas e inserção da espiga, comprimento médio dos internódios, diâmetro do colmo e área foliar. Foram coletadas folhas da base da espiga para análise nutricional. Foram avaliados após a colheita do milho os componentes da produção e produtividade de grãos. Os componentes da produção estudados foram: população final de plantas por hectare, número de espigas por hectare, comprimento de espigas, diâmetro de espigas... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract : The development of environmentally sustainable and economically viable agricultural systems has been increasing throughout the years, maximizing soil and input use. The objective of this work was to evaluate maize response to potassium doses when cropped on Brachiaria brizantha residues, both single and in a crop-livestock system (maize intercroppped with Brachiaria brizantha). The experiment was carried out in Botucatu-SPBrazil, Lageado Experimental Farm, in 2007/2008 and 2008/2009. The split-split-plot design consisted of 16 treatments arranged in completely randomized blocks with four replications. The area of each split-split-plot was 35 m2 (5 x 7 m). The main plots consisted of four K2O doses (0, 75, 150 and 225 kg ha-1). The split-plots were the absence or presence of Brachiaria brizantha cultivated in the growing season of 2007/2008 as cover crop. The split-split-plots consisted of two tillage systems (single maize and maize intercropped with Brachiaria brizantha). Both K2O doses and tillage systems were implemented in 2008/2009. At flowering, plant and ear height, internodes length, stem diameter and leaf area were evaluated. Leaves from the base of the ear were taken for nutritional analysis. After harvest, yield components and grain yield were determined. The yield components evaluated were final plant population per hectare, number of ears, ear length, ear diameter, number of grain rows per ear, weight of 1,000 grains, number of grains per ear and grain length. Soil samples were taken to evaluate exchangeable and non-exchangeable... (Complete abstract click electronic access below) / Doutor

Made available in DSpace on 2014-06-11T19:30:24Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-05-08Bitstream added on 2014-06-13T19:00:30Z : No. of bitstreams: 1 cruz_scs_dr_botfca.pdf: 754953 bytes, checksum: 6a8bc7052e1faca4049c3cfab25c5e36 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / A busca por uma agricultura ecologicamente sustentável e economicamente viável vem aumentando ao longo dos anos. Neste sentido, sistemas de cultivo que visam à maximização do uso do solo e dos insumos agrícolas têm ganhado, cada vez mais, espaço na agricultura brasileira. O objetivo deste trabalho foi avaliar a resposta do milho cultivado sob cobertura vegetal de Brachiaria brizantha a doses crescentes de potássio, em cultivo solteiro e em sistema de integração lavoura-pecuária (milho consorciado com Brachiaria brizantha). O experimento foi conduzido na Fazenda Experimental Lageado da FCA/UNESP, em Botucatu-SP, nos anos agrícolas de 2007/2008 e 2008/2009. O experimento consistiu de 16 tratamentos estabelecidos em esquema de blocos casualisados com parcelas subsubdivididas em quatro repetições, tendo a área de cada subsubparcela 35 m2 (5 x 7 m). Cada dose de K2O (0, 75, 150, 225 kg ha-1) correspondeu a uma parcela, sendo as subparcelas formadas pela presença ou ausência de Brachiaria brizantha cultivada no ano agrícola de 2007/2008 como planta de cobertura, as subsubparcelas foram compostas por dois sistemas de cultivo (milho solteiro e milho consorciado com Brachiaria brizantha). As doses de K2O e os sistemas de cultivo só foram implantados no ano agrícola de 2008/2009. Durante o período de florescimento da cultura do milho foram tomadas medidas da altura de plantas e inserção da espiga, comprimento médio dos internódios, diâmetro do colmo e área foliar. Foram coletadas folhas da base da espiga para análise nutricional. Foram avaliados após a colheita do milho os componentes da produção e produtividade de grãos. Os componentes da produção estudados foram: população final de plantas por hectare, número de espigas por hectare, comprimento de espigas, diâmetro de espigas... / The development of environmentally sustainable and economically viable agricultural systems has been increasing throughout the years, maximizing soil and input use. The objective of this work was to evaluate maize response to potassium doses when cropped on Brachiaria brizantha residues, both single and in a crop-livestock system (maize intercroppped with Brachiaria brizantha). The experiment was carried out in Botucatu-SPBrazil, Lageado Experimental Farm, in 2007/2008 and 2008/2009. The split-split-plot design consisted of 16 treatments arranged in completely randomized blocks with four replications. The area of each split-split-plot was 35 m2 (5 x 7 m). The main plots consisted of four K2O doses (0, 75, 150 and 225 kg ha-1). The split-plots were the absence or presence of Brachiaria brizantha cultivated in the growing season of 2007/2008 as cover crop. The split-split-plots consisted of two tillage systems (single maize and maize intercropped with Brachiaria brizantha). Both K2O doses and tillage systems were implemented in 2008/2009. At flowering, plant and ear height, internodes length, stem diameter and leaf area were evaluated. Leaves from the base of the ear were taken for nutritional analysis. After harvest, yield components and grain yield were determined. The yield components evaluated were final plant population per hectare, number of ears, ear length, ear diameter, number of grain rows per ear, weight of 1,000 grains, number of grains per ear and grain length. Soil samples were taken to evaluate exchangeable and non-exchangeable... (Complete abstract click electronic access below)

Clinoptilolite is a natural zeolite which can be used favorably in heavy metal removal. The main mechanisms for metal removal via clinoptilolite are adsorption and ion exchange. Several sources propose to keep the normality constant to obtain equilibrium isotherms for ion exchange systems, while many studies use constant sorbent mass with varying normalities of the sorbate. The objective of this study is to investigate the prevailing mechanisms of clinoptilolite during cadmium removal and the impact of the methodology for obtaining equilibrium isotherms. Batch Cd2+ removal experiments were conducted by using the two different methodologies (i.e. keeping the sorbent mass constant vs. keeping the normality constant) with clinoptilolite in as-received (AsC) and conditioned form (CnC), an ion exchange resin and granulated activated carbon. Exchangeable and framework cations, conductivity and pH were monitored during experiments. The equilibrium results were then fitted to isotherm models. The prevailing mechanisms for Cd2+ removal with clinoptilolite are discussed considering all monitored parameters and isotherm model fits. Use of the methodology was seen to have an effect on the overall Cd2+-clinoptilolite interaction. For example, differences between methodologies are observed regarding maximum sorbed Cd2+ and the distribution of exchangeable cations. Conductivity profiles provided a good indication of presence of ion exchange and demonstrated that it is more dominating for CnC than for AsC. The Cd2+ removal capacities observed in this study (0.65 meq/g for AsC and 1.46 meq/g for CnC) are the highest recorded for a clinoptilolite sample, as can be found in the literature.

Made available in DSpace on 2015-03-26T13:53:03Z (GMT). No. of bitstreams: 1 texto completo.pdf: 602726 bytes, checksum: e2d9ab25bd948e5bb48df8f314ae742c (MD5) Previous issue date: 2008-06-20 / The K accumulated in the plants cultivated in a successive way in the soils can be larger than the amount available in the soil initially, because in some cases, there is the participation of ways of the K that initially were not available to the nutrition of those plants. Thus, this work had the following objectives: evaluate the extractors Mehlich-1, Mehlich-3, NH4OAc 1 mol L-1 pH 7, H2SO4 0,5 mol L-1 boiling and e HNO3 2 mol L-1 boiling, as measures of availability of K in a short and long term; correlate the tenors of K obtained by those methods, with the contents of K in the aerial part of the corn plants from cultivation and in accumulative form. The experiment, factorial: 7 x 6, corresponded to seven soils (two Red- Yellow Latosols, one Red Latosol, two Cambisols, two Red- Yellow Argisols) of the State of Minas Gerais and six doses of added K (0; 50; 100; 200; 300 e 500 mg dm-3 of K) being the source KCl. The experiment was accomplished in randomized blocks with four repetitions. The liming, in the soils that needed it, and the doses of K were applied simultaneously, being the soils incubated by a period of 35 d. After that period, subsamples were collected for the determination of the K available by Mehlich-1, Mehlich-3, NH4OAc 1 mol L-1 pH 7, H2SO4 0,5 mol L-1 boiling and HNO3 2 mol L-1 boiling, before each cultivation. In the moment of the planting, the application of the doses of P and S was in agreement with the remaining P of each soil; a dose of 100 mg dm-3 of N was also applied. During the transport of each cultivation, a weekly dose of 50 mg dm-3 of N e B, Cu, Fe, Mn, Mo and Zn was applied in the following doses: 0,20; 0,33; 0,39; 0,92; 0,04 and 1 mg dm-3 respectively. Four corn plants were cultivated per pot. When 45 d of cultivation were passed, the plants were cut, then were dry, grinded in Wiley mill type and mineralized by the nitric - perchloric mixture (3:1); this proceeding happened with each cultivation. The total tenor of K was determined in the original samples of the seven soils. In the interval of each cultivation, samples of soil were subjected to extractors of K. The statistical analyses consisted of analyses of variance, regression and correlation. It was verified that along the cultivations the tenors of K extracted from all of the extractors were decreasing, ommitting the production of dry matter on the part of the corn plants that were cultivated. The H2SO4 0,5 mol L-1 boiling and HNO3 2 mol L-1 boiling, were the extractors that presented the largest capacity of recuperation of K in the seven soils in all of the cultivations, for they possess the largest force of extraction of K. The soils, PVAe1 and PVAe2 presented the largest tenors of extracted K for the five extractors along the cultivations. The critical levels of K went increasing when they were calculated in an accumulated way of the first to the seventh cultivation, to obtain larger productions of dry matter. The largest critical levels of K were obtained by the soils PVAe1 and PVAe2. There was contribution of available and non available fractions for all of the extraction methods in the nutrition of the corn plants cultivated in all the seven soils. It was observed that the accumulated contents of K in the aerial part of the corn plants in the six doses of K were highly correlated with the tenors of the nutrient in the soil obtained through the extractions with Mehlich-1, Mehlich-3 and NH4OAc 1 mol L-1 pH 7. That indicates that those extractors were appropriate to esteem the readiness of K during the growth of the plants for the first cultivation and in accumulative form of corn in the seven cultivations accomplished. The tenors of extracted K for Mehlich-1, Mehlich-3 e NH4OAc 1 mol L-1 pH 7 were highly correlated amongst themselves. / O K acumulado nas plantas cultivadas de modo sucessivo pode ser maior do que a quantidade disponível existente no solo inicialmente, por que, em alguns casos, ocorre a participação de formas do K que inicialmente não estavam disponíveis à nutrição dessas plantas. Assim, este trabalho teve os seguintes objetivos: avaliar os extratores Mehlich-1, Mehlich-3, NH4OAc 1 mol L-1 pH 7, H2SO4 0,5 mol L-1 fervente e HNO3 2 mol L-1 fervente, como medidas de disponibilidade de K a curto e a longo prazo; correlacionar os teores de K obtidos por esses métodos, com os conteúdos de K na parte aérea das plantas de milho por cultivo e em forma acumulativa. O experimento, fatorial: 7 x 6, correspondeu a sete solos (dois Latossolos Vermelho-Amarelo, um Latossolo Vermelho, dois Cambissolos, dois Argissolos Vermelho-amarelo) do Estado de Minas Gerais e seis doses de K adicionadas (0; 50; 100; 200; 300 e 500 mg dm-3 de K) sendo a fonte KCl. O experimento foi realizado em blocos casualizados com quatro repetições. A calagem, nos solos que dela necessitou, e as doses de K foram aplicadas simultaneamente, ficando os solos incubados por um período de 35 d. Após esse período, coletaram-se subamostras para a determinação do K disponível por Mehlich-1, Mehlich-3, NH4OAc 1 mol L-1 pH 7, H2SO4 0,5 mol L-1 fervente e HNO3 2 mol L-1 fervente, antes de cada cultivo. No momento do plantio, a aplicação das doses de P e S foi de acordo com o P remanescente de cada solo; aplicou-se, também uma dose de 100 mg dm-3 de N. Durante a condução de cada cultivo, aplicou-se, semanalmente uma dose de 50 mg dm-3 de N e B, Cu, Fe, Mn, Mo e Zn nas seguintes doses: 0,20; 0,33; 0,39; 0,92; 0,04 e 1 mg dm-3 respectivamente. Cultivaram-se quatro plantas de milho por vaso. Passados 45 d de cultivo, cortaram-se as plantas, que foram secas, moídas em moinho tipo Wiley e mineralizadas pela mistura nítricoperclórica (3:1); esse procedimento realizou-se para cada cultivo. O teor de K total foi determinado nas amostras originais dos sete solos. No intervalo de cada cultivo, amostras de solo foram submetidas aos extratores de K. As análises estatísticas consistiram de análises de variância, regressão e correlação. Verificou-se que ao longo dos cultivos os teores de K extraídos por todos os extratores foram diminuindo, comprometendo a produção de matéria seca por parte das plantas de milho que foram cultivadas. O H2SO4 0,5 mol L-1 fervente e o HNO3 2 mol L-1 fervente, foram os extratores que apresentaram a maior capacidade de recuperação do K nos sete solos em todos os cultivos, por possuírem a maior força de extração de K. Os solos, PVAe1 e PVAe2 apresentaram os maiores teores de K extraídos pelos cinco extratores ao longo dos cultivos. Os níveis críticos de K foram aumentando quando foram calculados de modo acumulado do primeiro até o sétimo cultivo, para se obter maiores produções de matéria seca. Os maiores níveis críticos de K foram obtidos pelos solos PVAe1 e PVAe2. Existiu contribuição de frações disponíveis e não disponíveis por todos os métodos de extração na nutrição das plantas de milho cultivadas em todos os sete solos. Observou-se que os conteúdos acumulados de K na parte aérea das plantas de milho nas seis doses de K, foram altamente correlacionados com os teores do nutriente no solo obtidos por meio das extrações com Mehlich-1, Mehlich-3 e NH4OAc 1 mol L-1 pH 7. Isso indica que esses extratores foram adequados para estimar a disponibilidade de K durante o crescimento das plantas para o primeiro cultivo e em forma acumulativa de milho nos sete cultivos realizados. Os teores de K extraídos pelo Mehlich-1, Mehlich-3 e NH4OAc 1 mol L-1 pH 7 foram altamente correlacionados entre si.

The stable isotope ratio of non-exchangeable hydrogen (δ2Hn) emerged as a promising new tool for source attribution in aquatic ecology, which can better discriminate between the organic matter sources. However, determining the absolute isotopic values is problematic due to the functional groups with hydrogen (H) that can easily exchange with the ambient water. This can lead to significant uncertainties in the absolute isotopic values, which eventually translates into errors in source attribution. However, controlled H exchange experiments with dual water equilibrations can alleviate this problem. However, current methods report significant variation in the absolute values, likely originating in partial H exchange, uncertainty in fractionation factors between exchangeable H and ambient water, and residual moisture. Here I used two methods for H exchange based on steam and liquid water using novel equipment for sample preparation called the Isobox. I evaluated the exchangeable H fraction in materials commonly analysed in ecology. Furthermore, I have investigated how these methods and associated analytical uncertainties can influence the mathematical mixing models used to resolve the source attribution using known sample mixtures made with soils and algae. The results show that 1) H exchange experiments using liquid water equilibration provide a higher exchangeable H fraction than the steam-based method, which was approximately three times higher. 2) The two-source mixing model proved to effectively determine the source attribution with known soil and algae mixtures, as evidenced by both water and steam equilibration. However, prior exposure to isotopically divergent waters can lead to source attribution errors, particularly with steam-based methods that provide low exchangeable H fractions. 3) When labile H is fully exchanged, source attribution does not depend on absolute δ2Hn determination, and simple one-water equilibration is sufficient. 4) Additional uncertainties in source attribution could originate from fractionation factors and δ2H measurement variability. The findings of this study conclude that the variations in fractionation factors did not significantly alter the mixing model as the error was below 5%. 5) Based on these experiments, I recommend keeping the analytical uncertainty of δ2H below ±5‰, which amounts to about a 6% error factor in source attribution. Finally, these experiments and analyses show how the methods can generate reliable data, depending on the research questions and whether absolute or relative isotopic values are required. This study provides different analytical pathways.