• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 91
  • 54
  • 15
  • 13
  • 9
  • 7
  • 7
  • 5
  • 2
  • 1
  • 1
  • 1
  • Tagged with
  • 234
  • 45
  • 45
  • 43
  • 42
  • 41
  • 36
  • 34
  • 33
  • 33
  • 28
  • 25
  • 24
  • 21
  • 20
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
81

Aquatic Priming Effects in the York River Estuary and Implications for Dissolved Organic Carbon Mineralization

Dunlap, Thomas M 01 January 2014 (has links)
The priming effect (PE), characterized as the enhanced microbial processing of bio-recalcitrant organic matter with the addition of labile substrates, has been hypothesized to moderate carbon (C) cycling in aquatic systems. In this study, aquatic PEs were evaluated through bacterial respiration and dissolved organic C consumption in incubations of water collected from three locations along the York River estuary. Incubations from White’s Landing on the Pamunkey River, a tidal freshwater tributary of the York, and from Croaker Landing in the middle of the estuary, displayed positive PEs when amended with labile C. In contrast, amended incubations from Gloucester Point, near the mouth of the estuary, displayed negative PEs, or reduced relative C metabolism, based on our calculations, This study provides empirical evidence for the occurrence of aquatic PEs and serves to elucidate how they may enhance or retard the processing and mineralization of organic C during transport to the ocean.
82

Techno-economic environmental risk analysis of advanced biofuels for civil aviation

Lokesh, Kadambari January 2015 (has links)
Commercial aviation has demonstrated its ability to be a key driver of global socio-economic growth to this date. This growth, resulting from an ever increasing need for air-travel, has been observed to be environmentally unsustainable. Any technological enhancements to the upcoming fleet of aircraft or operational improvements have been overshadowed by this very demand for air-travel. Any further investigation into innovative concepts and optimisation approaches bring in trade-off difficulties due to limitations in current technology. This creates a constraint on design space exploration. The need to mitigate civil aviation’s environmental impact has necessitated this sector to expand its frontier and seek radical technologies. Among a range of other technologies, advanced biofuels for civil jet engines have been claimed to be one of the most promising solutions. “Techno-economic Environmental Risk Analysis (TERA) of Advanced Biofuels for Civil Aviation” is a study that contributes to knowledge through conception plus application of quantitative/ qualitative approaches to assess the technical viability, financial feasibility and environmental competence of 2nd and 3rd generation biojet fuels, through their application into the existing scenario of civil aviation, against that of the fossil-derived conventional jet fuel (Conv.Jet fuel). TERA of advanced biofuels aims to accomplish the aforementioned through a holistic, multi-disciplinary study entailing life cycle studies, carbon-foot printing, sustainability analysis, fuel chemistry, virtual studies comprising combustion thermodynamic, engine/aircraft performance and emission prediction, economic studies entailing biofuel price prediction and business case analysis as opposed to earlier studies. TERA of Advanced biofuels study entails development of elaborate life cycle models, ALCEmB (Assessment of Life Cycle Emissions of Biofuels) and ALCCoB (Assessment of Life Cycle Cost of Biofuels) to predict life cycle emissions and costs, respectively, of the advanced biofuels from the point of raw material generation to the point of finished product consumption (a “cradle-grave” approach). A virtual experiment, to assess the impact of the “performance” properties of the advanced biofuels on a representative twin-shaft turbofan/airframe combination, relative to that of Conv.Jet fuel, was also undertaken through numerical modelling and simulation.Evaluation through ALCEmB revealed that Camelina-SPK, Microalgae-SPK and Jatropha-SPK delivered 70%, 58% and 64% savings in life cycle emission, relative to Conv.Jet fuel. The Net Energy Ratio (NER) analysis indicates that current technology for the biofuel processing is energy efficient and technically feasible. An elaborate post-combustion gas property evaluation infers that the Bio-SPKs exhibit improved thermodynamic behaviour. This thermodynamic effect has a positive impact on mission-level fuel consumption which reflected as fuel savings in the range of 3 - 3.8% and, therefore, emission savings of 5.8-6.3% in CO2 and 7.1-8.3% in LTO NOx, relative to that of Jet-A1. An economic feasibility analysis which entails prediction of hypothetical biofuel price prediction and its impact on direct operating cost (DOC) of an aircraft which infers that Bio-SPKs, over a user-defined medium-range mission profile, costs an additional 95-100% in terms of aircraft DOC, relative to that operated with conventional Jet-fuel, within short (2020) and medium (2020). However, the advanced biofuels are able to exhibit financial competence from 2020 onwards, relative to that of Conv.Jet fuel. However, the Bio-SPKs exhibit this economic feasibility only against a backdrop of persistent Conv.Jet fuel price volatility and severe environmental taxation between the analysis periods (2020-2075).
83

Finding the Man, Husband, Physician & Father: Creating the Role of Doc Gibbs in Thornton Wilder's Our Town

Payne, Patrick 17 December 2010 (has links)
This thesis serves as documentation of my efforts to define accurately my creative process as an actor in creating the role of Doc Gibbs in Our Town by Thornton Wilder. This includes research, rehearsal journal, character analysis and evaluation of my performance. Our Town was produced by the University of New Orleans Department of Film, Theatre and Communication Arts in New Orleans, Louisiana. The play was performed in the Robert E. Nims Theatre of the Performing Arts Center at 7:30 pm on the evenings of April 22 through April 24, 2010 and April 29 through May 1, 2010 as well as one matinee at 2:30 pm on Sunday, May 2, 2010.
84

Strontium Isotopes-A Tracer for Dust and Flow Processes in an Alpine Catchment

Hale, Colin Andrus 01 July 2018 (has links)
Stream chemistry changes in response to snowmelt, but does not typically reflect thechemistry of the snowpack. This suggests that flow processes between snowmelt and streamsystem, such as interactions with the soil and bedrock, have an important control on waterchemistry and highlight the complex flow pathways from the snowpack to stream. To investigateflow processes in the upper Provo River watershed, northern Utah, we sampled three sites on theriver ~20 times per year during 2016 and 2017. The sites, from highest elevations to lowest wereSoapstone, Woodland, and Hailstone, corresponding to locations of active stream gauges. Toidentify possible water sources to the stream during snowmelt, water samples were taken forsnow, ephemeral streams, soil water, lake, and spring water. To investigate potential impacts ofmineralogy, samples were taken for dust, soil and bedrock. The upper Provo River showeddistinct temporal variation in filtered (<0.45 microns) stream water for 87Sr/86Sr, dissolvedorganic carbon (DOC), silica (Si), and Lead (Pb) during the snowmelt season. The watershed hasdistinct 87Sr/86Sr ratios for bedrock (0.7449)
85

Forma??o docente continuada no projeto ?Trajet?rias Criativas? de uma escola no munic?pio de Alvorada, RS

Silva, K?tia Oliveira 09 January 2018 (has links)
Submitted by PPG Educa??o (educacao-pg@pucrs.br) on 2018-03-15T14:10:18Z No. of bitstreams: 1 K?tia Oliveira Silva.pdf: 1055941 bytes, checksum: d9fd8e2d88ade648ca728d489246fbe4 (MD5) / Approved for entry into archive by Tatiana Lopes (tatiana.lopes@pucrs.br) on 2018-03-23T14:01:36Z (GMT) No. of bitstreams: 1 K?tia Oliveira Silva.pdf: 1055941 bytes, checksum: d9fd8e2d88ade648ca728d489246fbe4 (MD5) / Made available in DSpace on 2018-03-23T14:07:23Z (GMT). No. of bitstreams: 1 K?tia Oliveira Silva.pdf: 1055941 bytes, checksum: d9fd8e2d88ade648ca728d489246fbe4 (MD5) Previous issue date: 2018-01-09 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior - CAPES / This dissertation investigates the continuing formation of five teachers who are part of an educational action called "Creative Trajectories (TC)" at a public school in the city of Alvorada, Metropolitan Region of Porto Alegre / RS. Educational action that is based on the development of authorship, of creation, autonomy and protagonism of young people aged 15 to 17 who did not complete Primary School. The investigative question consisted in know is, how happens the continuous formation of the teachers of the Creative Trajectory Project. It was a qualitative study based on the Participant Research, which used participant observation with information in the field diary, conversation wheels (in the B.S. School and in the UFRGS) in the collection of information, questionnaires, interviews and reading and document analysis. According to the production of the information and, in a special way, the transcription of the subjects' speeches, I made the intersection of these with the theories and the discussion proposal. The conclusive analysis of the dissertation was that the continuous training of the professionals of the Creative Trajectory Project is basically based on the daily classroom and pedagogic activities, which are directly linked to the context of the students. Teachers also use the space of pedagogical meetings to exchange experiences and promote shared learning among peers. They expand their knowledge through online courses and presential classes of fewer hours and participate in the courses offered by the College of Application (UFRGS) in the socalled immersions. Faced with this situation, it is possible to affirm that continuing teacher education lacks more specific and characteristic themes about the realities of youth, and that these teachers struggle against the precariousness of the world in in teaching struggling to keep up to date. Each of these professionals presented an untiring search for the knowledge necessary to teach, especially with the youth of the TC, becoming, themselves, autonomous authors of their knowledge, protagonists in the pedagogical action of each new day, creators of situations and proposals involving both for them as well as for the students Exactly what the Creative Trajectory Project intends to accomplish with the youth that participate in it. / Essa disserta??o investiga a forma??o docente continuada de cinco docentes que fazem parte de uma a??o educativa chamada ?Trajet?rias Criativas (TC)?, numa escola da Rede P?blica no munic?pio de Alvorada, Regi?o Metropolitana de Porto Alegre/RS. Esta a??o educativa est? baseada no desenvolvimento da autoria, da cria??o, da autonomia e do protagonismo de jovens de 15 a 17 anos que n?o conclu?ram o Ensino Fundamental. A pergunta investigativa consistiu em saber como acontece a forma??o continuada dos docentes do Projeto Trajet?rias Criativas. Foi um estudo qualitativo a partir da Pesquisa Participante, que utilizou na coleta de informa??es a observa??o participante com registros no di?rio de campo, rodas de conversas (na Escola B.S. e na UFRGS), question?rios, entrevistas e leitura e an?lise de documentos. De acordo com a produ??o das informa??es e, de modo especial, a transcri??o das falas dos sujeitos, entrecruzei essas com as teorias e com a proposta de discuss?o. A an?lise conclusiva da disserta??o foi de que a forma??o continuada dos profissionais do Projeto Trajet?rias Criativas acontece, basicamente, a partir do cotidiano da sala de aula e do fazer pedag?gico, os quais est?o diretamente vinculados ao contexto dos estudantes. Os docentes tamb?m utilizam o espa?o das reuni?es pedag?gicas para a troca de experi?ncias e a promo??o de aprendizagens compartilhadas entre os pares. Ampliam seus conhecimentos atrav?s de cursos online e presenciais de menor carga hor?ria e participam das forma??es oferecidas pelo Col?gio de Aplica??o (UFRGS), nas chamadas imers?es. Diante desse quadro, ? poss?vel afirmar que forma??o docente continuada carece de temas mais espec?ficos e caracter?sticos sobre as realidades das juventudes e que esses docentes lutam contra as precariedades do mundo na doc?ncia teimando em manter-se atualizados. Cada um desses profissionais apresentou uma incans?vel busca pelo conhecimento necess?rio ? doc?ncia, sobretudo com as juventudes do TC, tornando-se, eles pr?prios, autores aut?nomos do seu conhecimento, protagonistas na a??o pedag?gica de cada novo dia, criadores de situa??es e propostas envolventes tanto para eles quanto para os alunos e alunas. Exatamente o que o Projeto Trajet?rias Criativas se prop?e a realizar com as juventudes que dele participam.
86

O papel da disciplina de Filosofia nos cursos superiores de administra??o / The role of the suject philosophy in the administration college courses

Vieira, S?rgio Eduardo Fazanaro 06 December 2007 (has links)
Made available in DSpace on 2016-04-04T18:32:41Z (GMT). No. of bitstreams: 1 Sergio Eduardo Fazanaro Vieira.pdf: 22108800 bytes, checksum: b920f3ff83f5858b657345c4c449e378 (MD5) Previous issue date: 2007-12-06 / This research aims to verify the contribution of Philosophy as a school subject to Administration college courses. The focus given to the study has as an object of analysis a College institution from the interior of the state of S?o Paulo, which propagates differed teaching quality, putting top professionals in the job market, according to the means of publishing of the institution itself. The project analyses the function that the subject Philosophy is given when inserted in the school curriculum of a course out of the plain universe of the epistemologic reflection, facing the challenges of practical and dynamic activity of the administrative quotidian. The methodology used consists of a qualitative investigation that gathers a bibliographical study on the theme, application of semistructured questionnaires pertinent to the teacher s performance and to the student s view before the pedagogic proposal of the institution. The present study is concentrated on the analysis of the collected data from the proposal of an excellence teaching, contextualizing the philosophical thinking in the conflicting and disparate realities of the market and policies ruling the administrative relationships. / Esta pesquisa tem por finalidade verificar a contribui??o da Disciplina de Filosofia nos cursos superiores de Administra??o. O recorte dado ao estudo tem como objeto de an?lise uma Institui??o de Ensino Superior no interior do Estado de S?o Paulo, que propaga qualidade de ensino diferenciada, formando, segundo os ve?culos de divulga??o da pr?pria Institui??o, a elite profissional para o mercado de trabalho. O projeto analisa a fun??o que a disciplina de Filosofia recebe ao ser inserida na grade curricular de um curso fora do universo puro da reflex?o epistemol?gica, enfrentando os desafios da atividade pr?tica e din?mica da administra??o. A metodologia utilizada constitui-se de uma pesquisa qualitativa reunindo um estudo bibliogr?fico sobre o tema, aplica??o de question?rios semi-estruturados pertinentes ? atua??o docente e ? vis?o discente frente ? proposta pedag?gica da institui??o. Tamb?m se estuda que contribui??o a disciplina em pauta d? ? forma??o do profissional esperado. O estudo est? focado na an?lise dos dados levantados a partir da proposta de um ensino de excel?ncia, contextualizando o pensar filos?fico, nas realidades contradit?rias e desiguais do mercado e das pol?ticas que regem as rela??es administrativas.
87

Poesia na sala de aula: um exerc?cio ?tico e est?tico / Poetry in the classroom: an ethical and esthetic exercise

Neves, Cynthia Agra de Brito 04 August 2008 (has links)
Made available in DSpace on 2016-04-04T18:32:46Z (GMT). No. of bitstreams: 1 Cynthia Agra de Brito Neves.pdf: 1079788 bytes, checksum: fd6d004c284c30a3c2d4488d3bb183fe (MD5) Previous issue date: 2008-08-04 / This study is part of the line of research of Pedagogical Practices and the Formation of the Educator. It shows how poetry has been worked into high school literature classes in public and private schools in the State of S?o Paulo and how contemporary student readers have accepted poetry texts. Interest in this research came from the teacher-researcher who, as a lover of poetry, shares poetic readings with her students and observes the surprise and enchantment that the poetic text can offer to dynamics in the classroom. Initially, theoretical references were sought that could justify the importance of ethics and esthetics for teaching art, poetry and erudite literature in the schools; this was followed by an historical reflection about the roots of poetry in the Greco-Latin tradition, as well as studying the nascent relation between poetry and education in ancient times until the arrival of this pedagogical tradition in national soil. Also, according to an historical perspective, certain moments were pointed out concerning significant changes in the history of reading, books, literature and the concept of poetry in education from ancient times to the modern era. Afterwards, empirical research was done using the methodology of taped oral interviews with teachers of Portuguese in both types of schools in the State. The purpose was to investigate what they understand as poetic and how to create teaching-learning of literature through poetry in the schools where they teach, which led to running into criticism and suggestions from the educators. The voice of the teachers was analyzed in dialogues with authors of educational theory and education. The conclusion was that poetry, reflection on language, non-submission and pleasure deserve privileged space in school discourse. / Esta disserta??o, inserida na linha de pesquisa Pr?ticas Pedag?gicas e Forma??o do Educador, mostra como a poesia tem sido trabalhada nas aulas de literatura do Ensino M?dio de escolas da rede p?blica e privada de ensino do estado de S?o Paulo e como os alunos-leitores contempor?neos t?m recepcionado o texto po?tico. O interesse por esta pesquisa nasceu da experi?ncia da professora-pesquisadora, que ? amante da poesia e, portanto, compartilha leituras po?ticas com os alunos, atentando para o estranhamento e para o encantamento que o texto po?tico ? capaz de proporcionar nas din?micas em sala de aula. Buscaram-se, inicialmente, referenciais te?ricos que justificassem a import?ncia ?tica e est?tica de se ensinar arte, poesia e literatura erudita na escola; em seguida, uma reflex?o hist?rica acerca das ra?zes da poesia na cultura ocidental greco-latina, bem como pesquisou-se o ber?o da rela??o poesia-educa??o na Antig?idade at? o ingresso dessa tradi??o pedag?gica em solo nacional. Ainda dentro de uma perspectiva hist?rica, foram assinalados momentos de ruptura que mudaram significativamente a hist?ria da leitura, do livro, da literatura e da concep??o de poesia na educa??o, da Antig?idade ? Idade Moderna. A partir de ent?o, chegou-se ? pesquisa emp?rica, cuja metodologia consistiu em entrevistas orais gravadas com docentes de l?ngua portuguesa de ambas as redes de ensino do estado, a fim de investigar o que entendem como po?tico e como se constr?i o ensino-aprendizagem da literatura atrav?s da poesia nas escolas onde lecionam, deparando-se, neste processo, com cr?ticas e sugest?es dos educadores. Analisou-se a voz dos professores em di?logo com autores da teoria liter?ria e da educa??o para se concluir que a poesia, linguagem de reflex?o, insubmiss?o e prazer, merece espa?o privilegiado dentre os discursos escolares.
88

O uso do e-mail como ferramenta did?tico-pedag?gica: uma an?lise sobre o discurso de professores de uma institui??o de ensino superior / Using e-mail as a didactic-pedagogical tool: an analysis of the discourse of professors in an Institution of higher learning

Miranda J?nior, Levi Pinto de 28 February 2005 (has links)
Made available in DSpace on 2016-04-04T18:32:58Z (GMT). No. of bitstreams: 1 Levi Pinto de Miranda Junior.pdf: 319498 bytes, checksum: 8633f7378b85061fdf577aa01b59f57a (MD5) Previous issue date: 2005-02-28 / This work follows the line of research University, Teaching and Formation of Teachers. Its principal objective is to analyze the discourse of professors in an Institution of Higher Learning in the State of S?o Paulo about the use of e-mail as a didactic-pedagogical resource. Afier signing a free consent agreement, 50 professors at the Institution answered a questionnaire containing questions about their professional profile and their knowledge about computers, Internet and e-mail. Results indicated that 48 (96.0%) professors have access to computers; 88.0% use them to send and receive e-mail; and 72.0% send didactic material to their students through this system. The participants agree that the computer is a good support for learning and that by means of it classes can be more interesting. Regarding the interactivity provided by using e-mail, 96.0% agree that it facilitates professor/student interaction as well as student/student interaction; furthermore, 90.0% agree that with the use of e-mail educational objectives are easier to reach. In the light of the results obtained, we recommend that professors of Higher Education be aware of the technological resources available in order to reflect on the use of these diverse tools, among which can be found e-mail, in the teaching-learning process. / Este trabalho se insere na linha de pesquisa Universidade, Doc?ncia e Forma??o de Professores e teve como objetivo principal analisar o discurso de professores de uma Institui??o de Ensino Superior do interior do Estado de S?o Paulo sobre o uso do e-mail como recurso did?tico-pedag?gico. Participaram da pesquisa 50 professores da referida Institui??o e a eles foi aplicado, ap?s a assinatura do Termo de Consentimento Livre e Esclarecido, um question?rio com perguntas referentes ao perfil dos participantes e a seus conhecimentos acerca de computadores, da Internet e do e-mail. Os resultados indicaram que 48 (96,0%) professores t?m acesso a computadores e que 88,0% o utilizam para o envio e recebimento de e-mail, enquanto 72,0% disseram enviar material did?tico para seus alunos atrav?s deste sistema. Os participantes concordam que o computador ? um bom suporte para a aprendizagem e que atrav?s dele as aulas podem se tornar mais interessantes. Quanto ? interatividade proporcionada pelo uso do e-mail, 96,0% concordam que ela facilita tanto a intera??o professor/aluno, quanto a intera??o aluno/aluno; al?m disso, 90,0% concordam que com o uso do e-mail os objetivos educacionais s?o alcan?ados mais facilmente. Em vista dos resultados obtidos, recomendamos que os professores de Ensino Superior estejam atentos aos recursos tecnol?gicos dispon?veis, de forma a refletirem sobre o uso de diversas ferramentas, entre elas o e-mail no processo de ensino-aprendizagem.
89

Deposição atmosférica de espécies químicas em Ribeirão Preto, uma importante cidade canavieira do estado de São Paulo / Deposição atmosférica de espécies químicas em Ribeirão Preto, uma importante cidade canavieira do estado de São Paulo

Coelho, Cidelmara Helena 30 March 2007 (has links)
Amostras de água de chuva foram coletadas no campus da USP Ribeirão Preto (RP) de agosto de 2002 a dezembro de 2005. Cerca de 84% (n=127) das amostras apresentaram excesso de acidez, com pH médio de 5,12. Não se observou sazonalidade no pH de acordo com o período de safra da cana. As concentrações médias ponderadas pelo volume (MPV, em mol L-1): K+ 3,9 (n=175), Na+ 2,1 (n=172), Ca2+ 5,0 (n=175) e Mg2+ 1,8 (n=168), observadas em RP, bem como seus fluxos de deposição por via úmida, foram ligeiramente mais elevadas que aquelas encontradas em chuvas de regiões com características semelhantes. As concentrações destes cátions foram sazonais, com um aumento no período de safra, sendo que a maior diferença foi observada para o íon K+, indicando a sua importante fonte na queima de biomassa. A sazonalidade do íon Ca2+ aponta para a importância das atividades agrícolas, intensificadas no período de safra, na emissão deste cátion para a atmosfera. Observaram-se boas correlações lineares entre as concentrações de Na+ e K+ (0,67626) e de Na+ e Ca2+ (0,77822), indicando a possibilidade de emissões pirogênicas e a ressuspensão do solo serem fontes de emissão de Na+. A MPV de carbono orgânico dissolvido (COD) encontrada em RP foi mais elevada que na Amazônia, onde também há intensa queima de biomassa, porém seus fluxos por via úmida em ambas as regiões foram similares (0,42 molCm-2ano-1). As concentrações de COD em RP apresentaram correlações lineares significativas com K+ (0,70341) e com Ca2+ (0,61638), apontando para a queima de biomassa e ressuspensão do solo como fontes importantes de emissão de carbono orgânico para a atmosfera. As concentrações de COD nas chuvas de Araraquara foram ainda maiores que em RP, indicando pronunciadas fontes locais naquela cidade. As MPV (nmol L-1) de Cd 0,54 (n=56), Pb 3,02 (n=94) e Cu, 19,9 (n=98), encontradas nas chuvas de RP foram semelhantes a regiões urbanas e industriais do hemisfério norte, enquanto a concentração de Al (448 nmol L-1, n=126) foi menor, e a de Zn (405 nmol L-1, n=120) apresentou-se dentro das faixas de concentrações relatadas nestes locais. Com exceção de Cd, os demais metais analisados (Pb, Cu, Zn e Al) também apresentaram concentrações significativamente maiores (P=0,05) nas chuvas durante o período de safra, indicando que a queima de biomassa e as atividades agrícolas podem aumentar a emissão destes metais para a atmosfera de RP. A correlação linear significativa entre Pb e Ca2+ (0,53845), indica a participação da ressuspensão do solo no aporte atmosférico de Pb em RP, enquanto a ausência de correlação linear entre Zn e K+ (0,20182) parece indicar a presença de outras fontes significativas de Zn para a atmosfera de RP, além da queima de biomassa. O cálculo do fator de enriquecimento demonstra que Cd, Zn, Pb e Cu estão enriquecidos com relação ao solo na chuva de RP, sugerindo que estes podem ter fontes antrópicas locais e / ou distantes. A análise preliminar de componentes principais não esclareceu o peso das diferentes fontes de emissão atribuídas neste trabalho. / Rain water samples were collected based on events at the University of São Paulo - campus Ribeirão Preto - from August 2002 to December 2005. About 84% (n=127) of the samples had excess of acidity, with an average pH of 5.12. There was no correlation between the pH values and the sugar cane harvest period. The Volume Weighed Means (VWM, in mol L-1) for K+ 3.9 (n=175), Na+ 2.1 (n=172), Ca2+ 5.0 (n=175) and Mg2+ 1.8 (n=168), and their wet fluxes in RP were slightly higher than those reported to regions with similar characteristics. The concentrations for these cations were seasonal, with higher values during the harvest period. The largest difference was observed for K+, indicating its important source in the biomass burning activity. The seasonality showed for Ca2+ is probably related to the higher soil resuspension during the more intense agricultural activities. A good linear correlation observed between Na+ and K+ (0.67626) and between Na+ and Ca2+ (0.77822), suggest that Na+ may have important pirogenic as well as soil dust sources. The VWM for Dissolved Organic Carbon (DOC) in RP was higher than that reported for rainwater in the Amazon region (where the biomass burning is also intense); however, the wet fluxes from both sites were very similar (0.42 mol C m-2 ano-1). DOC concentrations were well correlated with K+ (0.70341) and Ca2+ (0.61638), suggesting that the biomass burning as well as soil dust can be important sources of organic carbon to the atmosphere. DOC concentrations in rainwater from Araraquara were even higher than those for RP, showing a high local source of organic carbon. The VWM (nmol L-1) for Cd 0.54 (n=56), Pb 3.02 (n=94) and Cu 19.9 (n=98) found in the rainwater from RP were similar to urban and industrialized regions of the Northern Hemisphere, while for Al (448 nmol L-1, n=126) it was lower, and for Zn (405 nmol L-1, n=120) the VWM was within the range reported for such areas. Except for Cd, all the other metals measured (Pb, Cu, Zn and Al) also showed higher concentrations (P=0.05) in rainwater samples during the harvest period, suggesting that biomass burning and intensive agricultural activities can increase these species concentrations in the atmosphere. The significant linear correlation between Pb and Ca2+ (0.53845) indicates that soil inputs can be of relevance for Pb atmospheric inputs in RP. On the other hand, the absence of linear correlation between Zn and K+ (0.20182) seems to indicate the presence of other important sources for Zn to the atmosphere besides biomass burning. The calculated Enrichment Factor showed that Cd, Zn, Pb and Cu are anomalously enriched in RP rainwater in relation to soil, suggesting these metals may have antroprogenic local sources as well as distant ones. The preliminary statistical analysis of principal components did not clarify the weight of the different sources of emission attributed in this work.
90

Mobilisation and transport of peatland carbon : the role of the riparian zone

Leith, Fraser Iain January 2014 (has links)
Northern peatlands are an important carbon store, with carbon dynamics and hydrology intrinsically linked. The riparian zone is the interface between the terrestrial and aquatic systems, situated adjacent to the stream and characterised by periodic flooding, near surface water tables and unique soil and plant species composition. Due to its unique biogeochemical environment, the riparian zone has the potential to modify significantly the production, mobilisation and transport of carbon via the land-atmosphere and aquatic pathways. Two contrasting headwater catchments, an ombrotrophic peatland (Auchencorth Moss, SE Scotland) and a forested, till dominated catchment (Västrabäcken, N Sweden), were investigated. In each carbon concentrations in soil and stream water and hydrological parameters were measured in transects connecting the wider catchment, riparian zone and stream. The overarching aim was to investigate the role of the riparian zone on the hydrological and bio-geochemical functioning of peatland and forested catchments, focusing on carbon export via the aquatic pathway. Specific objectives were to: a) examine the importance of soils, water table and vegetation composition on riparian biogeochemical cycling, b) investigate riparian-stream hydrological connectivity and the transport of carbon across the soil-water interface and c) assess riparian processes in relation to the net ecosystem carbon balance (NECB) across northern latitude ecosystems. Porewater total carbon (TC) concentrations (sum of dissolved organic and inorganic carbon (DOC, DIC), CO2 and CH4) were on average higher in Auchencorth Moss (78.8-140 mg C L-1) than the Västrabäcken (27.7-63.2 mg C L-1) catchment. In both catchments, higher TC concentrations were observed in the riparian zone compared to the wider catchment. The dominant control for differentiating between catchment and riparian biogeochemical processes was the higher average riparian water table with each carbon species displaying a positive relationship with water table height. A range of other factors, including soil temperature and the carbon content of catchment and riparian soils, also contributed to the complexity of riparian carbon biogeochemical cycles. Catchment specific phenomena, including the presence of aerenchymous vegetation and stream sediment deposition onto the riparian zone, modified riparian carbon dynamics in the Auchencorth Moss catchment. Isotopically, porewater DOC, CO2 and CH4 had a 14C content >100 %modern, indicating that the modern plant derived DOC is being transported down the soil profile, providing the source for CO2 and CH4 production at depth. In both catchments the riparian zone represented an important and dynamic source of carbon to stream waters. Total annual CO2 export from the riparian zone of the Västrabäcken catchment to the stream channel over the hydrological year was 2.7 g CO2-C m2 yr-1 with export predominantly from between 40 and 55 cm depth within the soil. Two monthly peaks in CO2 export occurred over the hydrological year related to either storm events or the spring snow melt period which accounted for 19 % of annual export, highlighting the temporal variability in soil-stream linkages, especially during high flow periods. In the generally wetter peatland catchment, riparian-stream linkages were driven by antecedent conditions and variation in riparian water table, with changes in water input, rather than changes in CO2 source concentrations, controlling stream water composition. The negative CO2 concentration-discharge relationship in the stream suggested that event water dominated, with small but important inputs from high concentration soil water during individual events. The importance of event water in transporting carbon was confirmed through the isotope result. CO2, CH4 and DOC exported via the aquatic pathway predominantly contained modern, plant derived carbon from the near surface soil horizons but with a small contribution (5-28 %) from deeper geological sources leading to aged evasion CH4 (310-537 years BP) and CO2 (36 years BP to modern). In both catchments the riparian zone was more important, relative to the wider catchment, in controlling the export of carbon via the aquatic pathway. At Auchencorth Moss, the riparian zone, plus an area of the catchment extending ~20 m from the stream, were hotspots for land-atmosphere fluxes of CH4, with mean flux of 1.08-7.70 mg m2 hr-1 in comparison to the catchment overall (0.05 mg m2 hr-1). In both catchments, combining detailed catchment hydrological models with high temporal resolution carbon concentration measurements, especially in riparian zone soils, has the potential to improve estimates of downstream and evaded carbon export in headwater catchments. Riparian zones should therefore be included more in studies investigating hydrological and biogeochemical processes in northern latitude headwater catchments. The processes within riparian zones suggest that despite the relatively small area that riparian zones represent, in relation to the wider catchment, they may play an important role in the NECB of peatland and forested catchments under future management and climate change scenarios.

Page generated in 0.4042 seconds