The effect of drainage and restoration on the ecology of different types of peatlands in the Šumava Mountains was investigated. The study was focused primarily on peat properties, vegetation dynamics, carbon gas fluxes and their linkages under the affected hydrological regimes.

Made available in DSpace on 2015-04-01T12:17:41Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 2182019 bytes, checksum: f16ae6c6befcaa27f593134ca7fa0f5d (MD5) Previous issue date: 2013-08-23 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Brazil is one of the references in the world market of ceramic tiles, ranking second in production and consumption. Only in 2012 were produced 865.9 million square feet, for a total installed capacity of 1.004 million square meters. An important aspect of the ceramic industry in the global context, is the continuous technological development, the widespread use of ceramics in various applications and environments and the increasing incorporation of waste from other sectors, giving sustainability concepts in the industry. Brazil produces on average 980 000 tonnes of glass packaging a year and has about a recycling rate of 47%. This study aimed to present one more option to the use of waste glass, which is still poorly recycled in Brazil, analyzing the influence of the replacement of feldspar in a ceramic, for residue from glass bottles are not returnable to the market. We tested three different percentages of glass waste, but also the influence on the behavior of the residue the technological properties with variation of firing temperature. Previously, all materials used in this work were characterized by the techniques of X-ray fluorescence, X-ray diffraction, thermal analysis and particle size. After established formulations, manufacturing and burning the bodies of the test piece, checked the technological properties and microstructure of established formulations. The results indicate that the glass waste has the potential to be used as a flux alternative to replace feldspar in the production of ceramic tiles for different purposes, according to NBR 13817/1997. / O Brasil é uma das referências no mercado mundial de revestimentos cerâmicos, ocupando a segunda posição em produção e consumo. Só no ano de 2012 foram produzidos 865,9 milhões de metros quadrados, para uma capacidade instalada de 1.004 milhões de metros quadrados. Um aspecto importante da indústria cerâmica, no contexto mundial, é o contínuo desenvolvimento tecnológico, a disseminação do uso de cerâmica em diferentes aplicações e ambientes e a crescente incorporação de resíduos provenientes de outros setores, dando conceitos de sustentabilidade no setor. O Brasil produz em média 980 mil toneladas de embalagens de vidro por ano e possui, aproximadamente, um índice de reciclagem de 47%. Este trabalho teve como objetivo apresentar mais uma opção para o aproveitamento do resíduo de vidro, que ainda é pouco reciclado no Brasil,analisando a influência da substituição do feldspato, em uma massa cerâmica, por resíduo de vidro proveniente de garrafas não retornáveis ao mercado. Foram testadas três diferentes percentuais de resíduo de vidro, como também a influência no comportamento do resíduo nas propriedades tecnológicas com a variação de temperatura de queima. Previamente, todos os materiais utilizados no trabalho foram caracterizados pelas técnicas de fluorescência de raios X, difração de raios X, análise térmica e granulométrica. Após estabelecidas as formulações, confecção e queima dos corpos-de-prova, foram verificadas as propriedades tecnológicas e microestruturais das formulações estabelecidas. Os resultados obtidos apontam que o resíduo de vidro apresentou potencial de ser utilizado como fundente alternativo em substituição ao feldspato, na produção de revestimentos cerâmicos para diferentes finalidades, de acordo com a norma NBR 13817/1997.

Para a garantia do bom desempenho dos fluxantes para lingotamento contínuo de aços no molde, a determinação da sua composição química é importante para garantir as propriedades necessárias para o seu perfeito funcionamento. O carbono é adicionado ao fluxante para controlar a velocidade de fusão do fluxante sobre o aço líquido, já que, se adequada, colabora para a disponibilidade de escória líquida suficiente para alimentar o intervalo existente entre a placa de aço em solidificação e o molde, garantindo a perfeita lubrificação. Neste trabalho é demonstrada a influência do efeito de duas fontes de carbono na velocidade de fusão dos fluxantes, através da utilização de uma nova concepção de forno elétrico no qual são colocados dois cadinhos vazados contendo fluxante in natura. Um dos cadinhos é utilizado para avaliação da amostra de referência. O desenvolvimento das reações de fusão do fluxante com o aumento da temperatura resulta em uma escória que, em função de sua fluidez, gera o escorrimento da massa fundida a uma taxa característica, a qual é registrada em um gráfico de massa x temperatura. Desta forma, é demonstrada a eficiência do uso deste equipamento para avaliação da velocidade de fusão, e da influência da fonte e teor de carbono, possibilitando a avaliação de diferentes alternativas de composições. Os ensaios de microscopia com aquecimento e análises térmicas também foram utilizados. / In order to assure good performance of mould flux for continuous casting of steel, the chemical composition definition is important to guarantee the properties needs to its perfect behavior in the mould. Carbon is added to the mould flux to control the melting rate, since this property is related to the availability of liquid slag to fill in the gap between the solidified steel and the cupper wall that assure a perfect lubrication. This work presents the influence of two carbon sources evaluated by an apparatus designed for testing the melting rate of mould fluxes. It is an electric resistance furnace in which two perforated at the bottom crucibles contain flux sample in natura. One of the crucibles is used for the reference sample. As the temperature increases and the melting of the flux takes place, liquid slag starts dropping from the crucible, which is attached to a load cell. Weight losses and temperature are simultaneously recorded and a plot of mass (grams) versus temperature (degree Celsius) is produced. The effect of carbon content of the flux mixtures on the melting rate has been investigated. The heating microscope and thermal analysis were also evaluated.

This thesis investigates the effects of alanine on rainbow trout’s glucose metabolism at the organismal and molecular levels. Rainbow trout is an important aquaculture species that belongs to the salmonid family. As a carnivorous fish, the requirement of protein/amino acids in trout’s diet is high. In contrast, rainbow trout are poor utilizers of carbohydrates. One prevalent hypothesis suggests that high levels of dietary amino acids could indeed contribute to the poor utilization of carbohydrates in this species. In mammals, there is evidence supporting the importance of alanine as a gluconeogenic precursor. However, a recent study found that alanine stimulates hepatic AMP-activated protein kinase (AMPK) to lower circulating glucose levels in mice. Alanine levels are high in all tissues in rainbow trout. The role of alanine in gluconeogenesis is less clear in trout and there is no evidence, to our knowledge, regarding its effects on glucose kinetics. Therefore, the main goal of the study was to investigate the impact of the continuous infusion of exogenous alanine for 4h on glucose fluxes and to identify potential mechanisms in tissues that could interpret the observed changes in glucose fluxes in vivo. Glucose turnover, appearance and disposal, Rt, Ra and Rd, respectively, were measured to determine the impact of alanine on glucose fluxes. The expression and/or activity of key genes in glucose transport, utilization and gluconeogenesis were assessed in liver and muscle. An additional goal was to assess whether alanine activates AMPK in trout. The levels of phosphorylated AMPK and other signaling proteins known to interact with the latter were quantified. Results show that alanine reduced plasma glucose levels and inhibited Ra and Rd glucose, consistent with previously observed effects of insulin in rainbow trout. The reduction in the expression of a paralogue of glut4, a key gene in glucose transport, and the activity of hexokinase (HK), a key enzyme in glucose utilization, in muscle can partially explain the observed reduction in Rd glucose. Together, these results suggest that glucose was not a preferred substrate under conditions of increased alanine availability and that alanine was probably oxidized to provide energy. Alanine failed to activate AMPK in trout, contrary to mammalian findings. However, it increased AKT (also known as protein kinase B) phosphorylation in muscle, similar to the effect of insulin in trout. In conclusion, my results suggest that alanine mediated at least some of the observed effects by stimulating insulin secretion given the similarities between the effects of exogenous alanine and insulin in rainbow trout as discussed above. Future studies are warranted to investigate the hypothesis that alanine is an insulin secretagogue in rainbow trout.

Global forests cover approximately 30% of land’s surface storing around 45% of above-ground terrestrial carbon. This carbon storage is constantly endangered by anthropogenic activities. Especially, tropical regions like the Amazon rainforest suffer from deforestation taking a great share in global CO2 emissions. In addition, forest dynamics are affected by climatic change like more frequent drought events. Quantifying the impact and feedback mechanisms of such climatic and anthropogenic changes on the global carbon cycle is still a great challenge. In this thesis, we developed a regionalization scheme to apply a forest gap model on the entire Amazon rainforest. Such a forest model has the advantage that it calculates forest growth at the individual tree level. It considers different successional states, that evolve form natural forest dynamics and disturbances, including information on tree height and species. The regionalized forest model thereby allows for integrating forest structure and species compositions into large-scale carbon analyses. The approach is independent of spatial scale and the simulation results can be linked to measurements from field inventory, eddy covariance, and remote sensing at local to continental scales. In a first study (chapter 2), we tested the capability of the forest model FORMIND to simulate gross primary production (GPP), respiration, and net ecosystem exchange (NEE) at daily and yearly time scales. The forest model was applied to spruce forests in Germany in order to analyze how the variability in environmental factors affects simulated carbon fluxes. Simulation results were compared to 6 years of eddy covariance (EC) data at a daily scale. The analysis shows that the forest model described the seasonal cycle of the carbon fluxes correctly, but estimated GPP differed from the observed data on days with extreme climatic conditions. Based on these findings, we developed two new parameterizations. One resulted from a numerical calibration against EC data. The other parameterization resulted from a method where EC data is filtered to extract the limiting factors for productivity. Thereby, new parameter values and even a new function for the temperature limitation of photosynthesis were found. The adopted forest model was then tested successfully at another spruce forest for cross validation. In general, the forest model reproduced the observed carbon fluxes of a forest ecosystem quite well. Although the overall performance of the calibrated model version was best, the filtering approach showed that calibrated parameter values did not necessarily correctly display the individual functional relations. The study has shown that the concept of simulating forest dynamics at the individual tree level is a valuable approach for simulating the NEE, GPP, and respiration of forest ecosystems. The focus of the second study (chapter 3) lied on the simulation of forest structure and above-ground biomass in the Amazon region with the forest model FORMIND. Estimating the spatial variation of biomass in the Amazon rainforest is challenging and, hence, a source of substantial uncertainty in the assessment of the global carbon cycle. On the one hand, estimates need to consider small-scale variations of forest structures due to natural tree mortality. On the other hand, it requires large-scale information on the state of the forest that can be detected by remote sensing. We, here, introduced a novel method that considered both aspects by linking the forest model and a wall-to-wall canopy height map derived from LIDAR remote sensing. The forest model was applied to estimate above-ground biomass stocks across the Amazon rainforest. This allowed for the direct comparison of simulated and observed canopy heights from remote sensing. The comparison enabled the detection of disturbed forest states from which we derived a biomass map of the Amazon rainforest at 0.16 ha resolution. Simulated biomass varied between 20 and 490 t(dry mass) ha-1 across 7.8 Mio km² of the Amazon rainforest (elevation < 1000 m). That equals a total above-ground biomass stock of 76 GtC with a strong spatial variation (coefficient of variation = 63%). The estimated biomass values fit estimates, that had been observed in 114 field inventories, well (deviation of only 15%). Beside biomass, the forest model allowed for estimating additional forest attributes such as basal area and stem density. The linkage of a forest model with a canopy height map allows for capturing forest structures at the individual to large scale. The approach is flexible and can also be combined with measurements of future satellite missions like ESA Biomass or GEDI. Hence, the study sets a basis for large-scale analyses of the heterogeneous structure of tropical forests and their carbon cycle. In a third study (chapter 4), we analyzed the interactions of productivity, biomass, and forest structure that are essential for understanding ecosystem’s response to climatic and anthropogenic changes. We here applied the forest model on the Amazon rainforest, combined simulation results with remotely-sensed data as in chapter 3, and additionally simulated ecosystem carbon fluxes. We found that the successional state of a forest has a strong influence on mean annual net ecosystem productivity (NEP), woody above-ground net primary production (wANPP), and net ecosystem productivity (NEP). These relations were used to derive maps of carbon fluxes at 0.16 ha resolutions (current state of the Amazon rainforest under spatial heterogenic environmental conditions). The Amazon was estimated to be a sink of atmospheric carbon with a mean NEP of 0.73 tC ha-1 a-1. Mean wANPP equals 4.16 tC ha-1 a-1 and GPP 25.2 tC ha-1 a-1. We found that forests in intermediate successional states are the most productive. Under current conditions, the Amazon rainforest takes up 0.59 PgC per year. This third study shows that forest structure and species compositions substantially influence productivity and biomass, and should not be neglected when estimating current carbon budgets or climate change scenarios for the Amazon rainforest. The findings of this thesis set a fundament for future analyses on carbon storage and fluxes of forests. Simulating at the tree level has the potential to investigate carbon dynamics from individual to continental scales. The regionalized forest model allows for the integration of different types of remotely sensed data in order to improve the spatial accuracy of estimates. The insights, we have gained from the eddy covariance study (chapter 2), help to investigate carbon dynamics of forests at continental scale also under changing climate. In combination with the regionalization approach (chapter 3 and 4), the findings of this thesis may be used to complement studies on drought events in forests and to understand feedback mechanisms caused by anthropogenic disturbances.

We propose the use of a small unmanned aerial vehicle (UAV) equipped with temperature, pressure, and relative humidity sensors to estimate sensible and latent heat fluxes over an active agricultural area in east-central Mississippi. The Bowen ratio method is applied to vertical soundings from the surface to 120 meters at 10-meter intervals. A number of flights were conducted at Mississippi State University during the late stages of the growing season with the purpose of obtaining heat flux estimates over different land surface/cover types. Results show that the UAV platform is able to provide reasonable heat and moisture flux estimates, and that the fluxes show substantial variability among different land cover types over a small spatial scale. Future work must be done to quantify the diurnal and seasonal changes in heat flux estimates over various crop types and investigate flight plans and sensor mounting options to maximize sensor precision.

Coastal ecosystems are faced with increasing pressures from human activities. Perhaps one of the most profound impacts is that of excess nitrogen loading which drives a series of negative consequences. Excess nitrogen fuels primary productivity and the subsequent enhanced microbial decomposition of organic matter, consumes oxygen and releases carbon dioxide, which causes large fluctuations in pH. Changes in organic matter availability, oxygen concentrations, and pH can have significant yet unconstrained implications for sediment recycling and removal of biologically important nutrients such as nitrogen and phosphorus. Such changes can also impact the production and consumption of two powerful greenhouse gases – nitrous oxide and methane. Here I use two temperate estuaries, Long Island Sound (New York, USA) and Waquoit Bay (Massachusetts, USA) to assess the role of human impacts on coastal sediment biogeochemical fluxes. In Chapter 1, I investigate the influence of organic matter loading on sediment nutrient cycling, excess nitrogen filtering, and greenhouse gas emissions in Long Island Sound, a heavily nutrient polluted estuary. To provide a comprehensive analysis of these benthic fluxes and their environmental drivers, I incubated sediment cores from five stations along a west to east transect representing a gradient of high to low nutrient inputs and organic matter deposition. I found sediments across the estuary removed only 9% of land-based nitrogen entering the system and had a nitrogen removal efficiency of 30%. Additionally, sediments were often a source of inorganic nitrogen and phosphorus as well as nitrous oxide and methane. This study provides the first directly measured rates of sediment nitrogen removal and production in Long Island Sound. In Chapters 2 and 3, I investigate the effect of coastal acidification on benthic fluxes of greenhouse gases and nutrients across the sediment-water interface in Waquoit Bay. I collected sediment cores from two sites experiencing different rates of nutrient loading and experimentally altered the overlying water pH through a series of incubations representing moderate (pH 7.3) and extreme (pH 6.3) pH conditions. My results show low pH conditions have a strong effect on greenhouse gas and nutrient fluxes and responses vary by site. Specifically, in the high nutrient impacted site, nitrous oxide flux increased and methane flux decreased under acidification. In the low nutrient impacted site acidification drove reduced nitrous oxide flux, while methane flux decreased in the moderate treatment and increased in the extreme treatment. Acidification also affected benthic nutrient fluxes and drove the high nutrient impacted site to become phosphorus limited. Furthermore, the relationships and drivers between nutrient availability and nutrient fluxes shifted under acidification. This dissertation provides additional insight into how coastal ecosystems respond to human impacts. In Chapter 1, I present a critical missing piece of the nitrogen budget of a heavily impacted estuary. In Chapters 2 and 3, I begin to elucidate how low pH conditions can impact sediment biogeochemistry in estuarine ecosystems. Efforts to improve our understanding of human impacts on sediment biogeochemical fluxes will create better informed coastal management practices for these dynamic systems under a changing climate. / 2025-10-23T00:00:00Z

Doctor of Philosophy / Department of Agronomy / Clenton E. Owensby / Most rangelands are harvested at some point during the year and removal of plant leaf area and biomass alters a host of ecosystem processes including gas exchange. An experiment was conducted in 2005 and 2006 to study the effects of clipping tallgrass prairie at different dates on water vapor and CO2 fluxes. A portable, non-steady-state chamber was designed to measure CO2 and water vapor fluxes from small plots in less than 40 s. A combination of sunlit and shaded readings allowed measurements of net carbon exchange (NCE) and ecosystem respiration (RE); by summing NCE and RE, gross canopy photosynthesis (GCP) was calculated. Throughout the two-year study, the chamber had a minimal effect on microclimate, i.e., average chamber temperature increased 2.9° C, while chamber pressure increased only 0.3 Pa during measurements, and photosynthetically active radiation attenuation was 10%. The immediate effect of all clipping treatments was a loss of leaf area that led to reductions in GCP, NCE, and RE and in most cases decreased water vapor flux. Further patterns of carbon flux were governed by the amount of water stress during canopy development, while water vapor flux rates varied with water availability. Canopies that developed during periods of low water stress quickly increased carbon flux rates following precipitation after a mid-season drought. However, flux rates of canopies, which developed during the mid-season drought, responded considerably slower to subsequent water availability. A separate experiment was conducted from June-October of 2006 to estimate GCP, leaf area index (LAI), and total aboveground biomass with a hyperspectral radiometer. Indices such as the Normalized Difference Vegetation Index and the Simple Ratio were used to estimate LAI and biomass had poor correlations with measured values. However, GCP was significantly correlated to all six indices derived in this study. While GCP measured from June-October was significantly correlated with all indices, removal of the senesced canopy scans recorded during October greatly increased the relationship.

Diversas metodologias foram desenvolvidas nas últimas décadas para cálculo de propriedades que representassem quantitativamente a distribuição de carga eletrônica de forma mais simplista. A mais básica destas propriedades é chamada de carga atômica. Contudo, não havendo unanimidade quanto à utilização de um formalismo de cálculo de carga para situações abrangentes de estudo, há a necessidade de trabalhos voltados para uma análise comparativa entre as respostas destes formalismos em termos de carga atômica e parâmetros derivados. Assim, fez-se nesta dissertação uma investigação sobre valores de carga atômica e propriedades dinâmicas relacionadas, com importância em estudos sobre movimentos vibracionais em moléculas, como fluxo de carga e fluxo de dipolo, obtidos com os formalismos de cálculo de carga de Mulliken, NPA, CHELPG e QTAIM. Neste trabalho também se avaliou o efeito da escolha do método de cálculo, como Hartree-Fock e métodos que incluem correlação eletrônica (MP2, MP4(SDQ) e CCSD), e do conjunto de funções de base, através de funções como cc-pVDZ, cc-pVTZ e cc-pVQZ, sobre estas propriedades dinâmicas. Os sistemas analisados incluíram moléculas diatômicas e triatômicas lineares (HF, HCl, LiH, NaH, NaCl, LiF, NaF, LiCl, BF, AlF, BeO, MgO, CO, ClF, CO2, CS2, OCS, HCN e HNC) formadas por ligações de caráter variado, desde altamente iônicas até covalentes e incluindo ligações múltiplas. Também foram estudadas moléculas de clorofluorometanos (CH4, CH3Cl, CH3F, CH2Cl2, CH2F2, CH2ClF, CHCl3, CHF3, CHCl2F, CHClF2, CCl2F2, CClF3, CFCl3, CCl4, e CF4) para observação do efeito da troca de substituintes nas propriedades citadas. Pelos resultados obtidos, pode-se afirmar que apenas os formalismos NPA e QTAIM apresentam bom comportamento quanto à convergência em relação ao método de cálculo e/ou tamanho do conjunto de funções de base utilizados no estudo do fluxo de carga. Entretanto, apenas os valores QTAIM são consistentes com certas considerações químicas fundamentais, como fluxos de carga tendendo a zero durante o estiramento de ligações de predominante caráter iônico, em moléculas com estruturas próximas à geometria de equilíbrio. As cargas e seus fluxos obtidos com Mulliken apresentaram alta dependência e problemas de convergência com a escolha da função de base, além de valores incoerentes em alguns sistemas. Por sua vez, CHELPG não se mostrou adequado à aplicação da aproximação finita de dois pontos na obtenção dos valores numéricos de fluxos de carga. A análise da resposta destas propriedades à troca de substituintes em moléculas de clorofluorometanos seguiu destacando positivamente QTAIM em relação aos outros formalismos. Enquanto CHELPG demonstrou oscilações inconsistentes em gráficos destes valores em função do número de átomos de cloro e/ou flúor, NPA e Mulliken se mostraram sensíveis à troca de substituintes, entretanto, os valores de fluxo de carga observados em alguns casos estão em desacordo com a tendência esperada na troca de átomos de hidrogênio por átomos de cloro ou flúor. / Several methodologies were developed in the last few decades in order to obtain a property which could represent quantitatively electronic charge distributions in a simple way. The fundamental quantity in this treatment is called atomic charge. However, as long as there is not an agreement about the most indicated method to determine atomic charges for general systems or responses under study, it is necessary to analyze, comparatively, how these methods behave in given situations and how the values derived from them respond in each case. Hence, an investigation including charges and related quantities as charge flux and atomic dipole flux, which are of interest to vibrational analysis, was done by means of values resulting from four formalisms, that are, Mulliken, NPA, CHELPG and QTAIM. In this study were also evaluated the changes in such dynamic properties when the calculations are done by means of different methods, as Hartree-Fock and methods that include electron correlation (MP2, MP4(SDQ) and CCSD) and, with different basis sets as cc-pVDZ, cc-pVTZ and cc-pVQZ. The systems analyzed were diatomic and linear triatomic molecules (HF, HCl, LiH, NaH, NaCl, LiF, NaF, LiCl, BF, AlF, BeO, MgO, CO, FCl, CO2, CS2, OCS, HCN and HNC) including diverse bonding character, such as highly ionic or covalent bonds along with multiple bonds. Also, charge and charge flux parameters in chlorofluoromethane molecules (CH4, CH3Cl, CH3F, CH2Cl2, CH2F2, CH2ClF, CHCl3, CHF3, CHCl2F, CHClF2, CCl2F2, CClF3, CFCl3, CCl4 and CF4) were studied to analyze the effects in these properties during the exchange of substituent atoms. Considering the data obtained, one can infer that only NPA and QTAIM formalisms result in satisfactory convergence patterns with chosen methods and/or basis set sizes during the determination of charge and charge flux values. However, only QTAIM charge fluxes seem to follow certain chemical considerations, as low values for charge flux in a bond enlargement in systems with a predominant ionic character close to their equilibrium geometry. The Mulliken formalism shows high dependence and convergence issues in basis set size increments, as well as some inconsistent values. On other hand, CHELPG formalism is not suited to the finite approach for numerical derivatives in its two-point version. The study of substituent effects in chlorofluoromethanes reinforces the performance of QTAIM when compared to other formalisms. While CHELPG returned inconsistent oscillations in plots against the number of chlorine/fluorine atoms, NPA and Mulliken exhibited some sensibility with the change of substituent, though the flux values observed in a few cases are in disagreement with the tendencies expected when the hydrogen atoms are switched by chlorine or fluorine atoms.

River, lakes and   streams account for more carbon dioxide emissions than all other freshwater   reservoirs together. However, there is still lack of knowledge of the   physical processes that control the efficiency of the air-water exchange of   CO2 in these aquatic systems. In the more turbulent water sections   of a river, the gas transfer is thought to be governed by the river’s   morphology such as bottom topography, slope and stream flow. Whiles for wider   sections of the river, the gas transfer could potentially be influenced by   atmospheric forcing (e.g. Wind speed). The main purpose of this project is to   study the fluxes of carbon dioxide and how (wind speed and stream discharge)   influence the CO2 fluxes in the river. In this study, direct and   continuous measurements of CO2 emission was conducted for the   first time in a controlled boreal river in Kattstrupeforsen (Sweden) from   18th April to 10th May 2018. A unique measurement setup which combines eddy   covariance techniques, general meteorology and in situ water variables (for   high accuracy emission measurements) was used. The results show that   in the late winter, an   upward directed CO2 fluxes measured in the river was approximately   2.2 μmol m−2 s−1. This value agrees with many other small and   large rivers where CO2 fluxes has been studied. The river can be   said to serve as source of CO2 to the atmosphere in the day due to   the dominant upward fluxes recorded during the daytime. The results also show   that carbon dioxide fluxes increase with increasing wind speed notably at   wind speed above 2 m s-1. There   was no relation between CO2 fluxes and stream discharge. This   indicates that wind speed could be one principal factor for air- river gas   exchange. The findings in this work on river gas exchange will provide   a basis for a regional estimate and be applicable for many river systems on a   global scale. / <p>2018-07-09</p>