Studies have shown that including perennial forages in cropping rotations can increase soil carbon (C) and lower nitrous oxide (N2O) emissions when compared to continuous annual cropping. Research is needed to evaluate the inclusion of a perennial forage in an annual crop rotation on net carbon dioxide (CO2) and N2O fluxes, natural and agronomic drivers of seasonal greenhouse gases (GHGs), and the possibility of using forages as a C sequestration-CO2 mitigation tool. A long-term field experiment site to determine GHG budgets for Red River Valley cropping systems in Manitoba, Canada was used. The site consisted of four plots with the same annual rotation management history. A perennial legume, alfalfa, was grown in 2008 and 2009 on two plots and spring wheat and industrial oilseed-rapeseed grown on the other two plots in 2008 and 2009, respectively. Nitrous oxide and CO2 fluxes were measured continuously using the flux gradient micrometeorological method. For the net study period, the perennial phase sequestered twice the atmospheric CO2 (2070 kg C ha-1) compared to the annual crops. The annual rotation emitted 3.5 times more N2O than the perennial legume phase. When accounting for harvest C removals and considering GHGs in CO2-equivalent (eq.), the perennial legume phase was a net sink of 5440 kg CO2-eq. ha-1 and the annual rotation was a net source of 4500 kg CO2-eq. ha-1 for the two year study period. Information gathered will help bridge missing data gaps in national emission trends and enhance development of Canadian GHG mitigation models.

Studies have shown that including perennial forages in cropping rotations can increase soil carbon (C) and lower nitrous oxide (N2O) emissions when compared to continuous annual cropping. Research is needed to evaluate the inclusion of a perennial forage in an annual crop rotation on net carbon dioxide (CO2) and N2O fluxes, natural and agronomic drivers of seasonal greenhouse gases (GHGs), and the possibility of using forages as a C sequestration-CO2 mitigation tool. A long-term field experiment site to determine GHG budgets for Red River Valley cropping systems in Manitoba, Canada was used. The site consisted of four plots with the same annual rotation management history. A perennial legume, alfalfa, was grown in 2008 and 2009 on two plots and spring wheat and industrial oilseed-rapeseed grown on the other two plots in 2008 and 2009, respectively. Nitrous oxide and CO2 fluxes were measured continuously using the flux gradient micrometeorological method. For the net study period, the perennial phase sequestered twice the atmospheric CO2 (2070 kg C ha-1) compared to the annual crops. The annual rotation emitted 3.5 times more N2O than the perennial legume phase. When accounting for harvest C removals and considering GHGs in CO2-equivalent (eq.), the perennial legume phase was a net sink of 5440 kg CO2-eq. ha-1 and the annual rotation was a net source of 4500 kg CO2-eq. ha-1 for the two year study period. Information gathered will help bridge missing data gaps in national emission trends and enhance development of Canadian GHG mitigation models.

Doctor of Philosophy / Department of Biological and Agricultural Engineering / Ronaldo G. Maghirang / Emission of particulate matter (PM) and various gases from open-lot beef cattle feedlots is becoming a concern because of the adverse effects on human health and the environment; however, scientific information on feedlot emissions is limited. This research was conducted to estimate emission rates of PM[subscript]10 from large cattle feedlots. Specific objectives were to: (1) determine feedlot PM[subscript]10 emission rates by reverse dispersion modeling using AERMOD; (2) compare AERMOD and WindTrax in terms of their predicted concentrations and back-calculated PM[subscript]10 emission rates; (3) examine the sensitivity of both AERMOD and WindTrax to changes in meteorological parameters, source location, and receptor location; (4) determine feedlot PM[subscript]10 emission rates using the flux-gradient technique; and (5) compare AERMOD and computational fluid dynamics (CFD) in simulating particulate dispersion from an area source. PM[subscript]10 emission rates from two cattle feedlots in Kansas were determined by reverse dispersion modeling with AERMOD using PM[subscript]10 concentration and meteorological measurements over a 2-yr period. PM[subscript]10 emission rates for these feedlots varied seasonally, with overall medians of 1.60 and 1.10 g /m[superscript]2 -day. Warm and prolonged dry periods had significantly higher PM emissions compared to cold periods. Results also showed that the PM[subscript]10 emissions had a diurnal trend; highest PM[subscript]10 emission rates were observed during the afternoon and early evening periods. Using particulate concentration and meteorological measurements from a third cattle feedlot, PM[subscript]10 emission rates were back-calculated with AERMOD and WindTrax. Higher PM[subscript]10 emission rates were calculated by AERMOD, but their resulting PM[subscript]10 emission rates were highly linear (R[superscript]2 > 0.88). As such, development of conversion factors between these two models is feasible. AERMOD and WindTrax were also compared based on their sensitivity to changes in meteorological parameters and source locations. In general, AERMOD calculated lower concentrations than WindTrax; however, the two models responded similarly to changes in wind speed, surface roughness, atmospheric stability, and source and receptor locations. The flux-gradient technique also estimated PM[subscript]10 emission rates at the third cattle feedlot. Analyses of PM[subscript]10 emission rates and meteorological parameters indicated that PM[subscript]10 emissions at the feedlot were influenced by friction velocity, sensible heat flux, temperature, and surface roughness. Based on pen surface water content measurements, a water content of at least 20% (wet basis) significantly lowered PM[subscript]10 emissions at the feedlot. The dispersion of particulate from a simulated feedlot pen was predicted using CFD turbulence model ([kappa]-[epsilon] model) and AERMOD. Compared to CFD, AERMOD responded differently to wind speed setting, and was not able to provide detailed vertical concentration profiles such that the vertical concentration gradients at the first few meters from the ground were negligible. This demonstrates some limitations of AERMOD in simulating dispersion for area sources such as cattle feedlots and suggests the need to further evaluate its performance for area source modeling.

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No. of bitstreams: 2 Dissertação - Rubia Santos Corrêa - 2014.pdf: 2181864 bytes, checksum: f7194eae8a762b1a93fbddf736eda76d (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Previous issue date: 2014-02-24 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Climate changes is of global importance influencing local and international policy decisions. It is important that sectors and human activities that contribute to worsen the global warming scenario are identified. Nitrous oxide (N2O) is an important greenhouse gas, despite its low concentration in the atmosphere this gas stands out due to its long residence time and to potential for absorption of infrared radiation of its molecule and to its hence high of global warming potential. N2O in the atmosphere has the ability to absorb infrared radiation of the earth and increase the average temperature of the planet. As consequences we observe the effects of warming on many environmental disasters, changes in rainfall patterns, melting glaciers and other phenomena caused by climate disorders. The magnitudes of the gas fluxes coming from the farm system are relevant, highlighting the need to identify sources sinks of greenhouse gas emissions (GGE) in agriculture. In Brazil the most commonly used method for measuring the greenhouse gas is the static chamber. It is supposed that with this method the fluxes GGE are underestimated. In this work this hypothesis was tested by comparing the N2O fluxes obtained with manuals static chambers with those obtained by a micrometeorological method, the flux-gradient, and characterizing the dynamics of the flux of N2O in the Integrated Crop-Livestock system (ICL). The study was conducted at Embrapa Rice and Beans, in Santo Antônio de Goiás, in clay Rhodic Ferralsol typical, under ICL system the pasture phase. Initial studies have been made to define sampling times and best time to perform the sampling by the manual static chamber method. The sampling times used were 0, 15 and 30 minutes and the best period for routine sampling was around 10 am. In calculating fluxes, whenever possible the Hutchinson & Mosier function was used. When this function not was applied a simple linear function was used. The flux calculated by the linear function was considered when R2 was greater than or equal to 0.80. The measured fluxes by the two quantification methods manuals static chambers and flux-gradient were comparable, however in 69.77% of the assessed days the values positive obtained by the flux-gradient method were higher than those obtained by the manual static chamber method. As to the physical and chemical attributes of the soil, considering the entire period under study, in pasture soil, it was observed that N2O fluxes were positively correlated with the nitrate concentration, WFPS and the soil temperature. In the rainy season there was a positive correlation between N2O fluxes and WFPS of soil. In the dry season there was a positive correlation between N2O fluxes and the ammonium and nitrate concentrations of soil. During the study not was observed emission of N2O in of reference area, area this formed by a native forest fragment. / As mudanças do clima são de importância global influenciando decisões políticas locais e internacionais. É importante que sejam identificados os setores e as atividades antrópicas que contribuem para agravar o cenário do aquecimento global. O óxido nitroso (N2O) é um importante gás de efeito estufa, apesar de sua baixa concentração na atmosfera esse gás se destaca devido ao seu longo tempo de permanência e ao potencial de absorção de radiação infravermelha de sua molécula e, consequentemente, ao seu alto potencial de aquecimento global. O N2O presente na atmosfera tem capacidade de absorver radiação infravermelha da Terra e aumentar a temperatura média do planeta. Como consequências observam-se os efeitos do aquecimento em diversos desastres ambientais, mudanças nos padrões de chuvas, derretimento das geleiras e outros fenômenos provocados pelas desordens climáticas. As magnitudes dos fluxos de gases oriundos do sistema agrícola são relevantes, destacando-se a necessidade de identificar fontes e sumidouros de gases de efeito estufa (GEE) na agricultura. No Brasil o método mais comumente utilizado para a medição de fluxos de GEE é a câmara estática. Supõe-se que, com este método, os fluxos de GEE são subestimados. Neste trabalho esta hipótese foi testada comparando os fluxos de N2O obtidos com câmaras estáticas manuais com os obtidos por um método micrometeorológico, o fluxo-gradiente, além da caracterização da dinâmica do fluxo de N2O no sistema de integração lavoura-pecuária (ILP). O estudo foi realizado na Embrapa Arroz e Feijão, no município de Santo Antônio de Goiás, em Latossolo Vermelho Acriférrico típico, sob sistema ILP na fase pastagem. Estudos iniciais foram feitos para definir o tempo de amostragem dos fluxos e o melhor horário para a realização das amostragens pelo método da câmara estática manual. Os tempos de amostragem utilizados foram de 0, 15 e 30 minutos e o melhor período para a rotina de amostragem se concentrou em torno das 10 h. No cálculo dos fluxos, sempre que possível foi utilizada a função de Hutchinson & Mosier. Quando esta função não era aplicável foi utilizada uma função linear simples. O fluxo calculado através da função linear era considerado quando o R2 era maior ou igual a 0,80. Os fluxos medidos pelos dois métodos de quantificação, câmaras estáticas manuais e fluxo-gradiente foram comparáveis, entretanto em 69,77% dos dias avaliados os valores positivos obtidos através do método do fluxo-gradiente foram superiores aos obtidos pelo método da câmara estática manual. Quanto aos atributos físicos e químicos do solo sob pastagem, considerando o período em estudo, observou-se que os fluxos de N2O apresentaram correlação positiva com o teor de nitrato, EPPA e a temperatura do solo. Na estação chuvosa houve correlação positiva entre os fluxos de N2O e o EPPA do solo. Na estação seca foi observada correlação positiva entre os fluxos de N2O e os teores de amônio e nitrato do solo. Durante o estudo não foi observada emissão de N2O na área de referência, área esta formada por um fragmento de floresta nativa.

In this study, the local similarity theory functions were calculated with two different approaches and on the other hand the mean hub height wind speed was compared with the rotor equivalent wind speed. Both calculations are based on two independent data-sets from measurement campaigns Hornamossen and Ryningsnäs which were conducted in the south of Sweden between May 2015 and June 2017, and November 2010 and February 2012. The first campaign includes measurements between 100 and 173 m and the second 98 and 138 m. In general, the aims were to validate if the results with reference functions and to compare the results from both approaches. The local similarity theory was used, because well above the ground, the assumption of a constant flux layer typically does not hold especially in the stable boundary layer. The used approaches are the flux-gradient and Richardson number formulation. Based on those, the non-dimensional universal functions for momentum and heat could be calculated and those could be presented as functions of the stability parameter. As shown in this study, the scatter the Richardson number formulation results are significant smaller compared to the flux-gradient formulation. One reason can be that the stability parameter and the universal functions for momentum and heat depend solely on the Richardson number. Despite the higher scatter, the medians of the universal function for momentum based on the flux-gradient formulations for both data-sets agree also with the references. Furthermore, for the results of the universal function for heat based on the flux-gradient formulation agree with the references if the minimum limit for the kinetic heat flux is significantly higher than for the universal function for momentum. Furthermore, in the publication from England & McNider 1995, who derived the Richardson number formulation, includes two erroneous equations for stable stratification. One of them has a tipping error and the other was incorrectly derived. Thus, the corrected equations are presented in this work. This work also presents new equations which are not based on the assumption that the constants of the empirical formulation for the universal function for momentum and heat with the same value. A comparison of the old and new equations show for a generated Richardson number vales a agreement of the results over the defined Richardson number range. Finally, in the wind industry it is a common practice to use the mean wind speed at the hub height as the representative mean wind speed over the entire rotor swept area. However, this assumption differs increasingly from the reality, because turbine sizes increase constantly. Thus, in this study, this common method is compared with another averaging concept. Hence, the work focuses on a area-weighted mean wind speed which is called the rotor equivalent wind speed. This average gives a better estimation of the existing wind field because it is based on multiple measurements at various heights. Since the wind gradient changes with height, those two velocities are plotted as functions of the same stability parameter as above. The main results in unstable stratification are that the hub height wind speed underestimates the rotor equivalent wind speed by about 1 to 1.5 %. In stable stratification the results vary: Two calculations show a overestimates by about 1 % and another shows no difference between those averages. Hence, the conclusion based on those findings are that the hub height wind speed is a source for a higher modelling uncertainty. On the contrary, the rotor equivalent wind speed gives more accurate modelling results. / I denna studie beräknades de lokala likhetsteorifunktionerna med två olika tillvägagångssätt och å andra sidan jämförs genomsnittliga vindhastigheten vid navhöjden med rotorekvivalent vindhastigheten. Beräkningarna är baserad på två oberoende datamängder från mätningskampanjer Hornamossen och Ryningsnäs som genomfördes i södra Sverige mellan maj 2015 och juni 2017 och november 2010 och februari 2012. Första kampanj innehåller mätningar mellan 100 och 173 m och den andra 98 och 138 m. Generellt var målet att validera resultaten med referensfunktioner och jämföra både tillvägagångssätt med varandra. Lokala likhetsteorinen används eftersom för mätningar långt över marken håller antagandet om ett konstant flödesskikt vanligtvis inte. Det gäller särskilt i det stabila gränsskiktet. De två tillvägagångssätten är flödesgradientförhållandet och Richardson-talformuleringen. Baserade på de formuleringarna kan de icke-dimensionella universella funktionerna för momentum och värme beräknas och de visas som en funktion av stabilitetsparametern. I denna studie visas att spridningen av Richardsons talformuleringsresultat är signifikant mindre jämfört med andra metoden. En anledning är att stabilitetsparameter och både universella funktioner beror endast på Richardson tal. Trots den högre spridningen överensstämmer medianerna för den universella funktionen för momentum baserat på flödesgradientformuleringarna med referenserna. Detsamma gäller för resultaten av den universella funktionen för värme baserat på flödesgradientformuleringen om minimigränsen om kinetiska värmeflödet är betydligt högre än för den universella funktionen för momentum. Dessutom innehåller publikationen från England & McNider 1995, som innehåller härledning av Richardson talformulering, två felaktiga ekvationer för stabila gränsskiktet. En av dem har ett tippfel och den andra var felaktigt härledd. Detta arbete presenteras de korrigerade ekvationerna. Dessutom presenteras en uppsättning nya ekvationer där de konstanterna av den empiriska formuleringen för den universella funktionen för momentum och värme inte antas att har samma värde. Slutligen är det i vindindustrin en vanlig praxis att använda den genomsnittliga vindhastigheten vid navhöjden som den representativa medelvindhastigheten för hela "rotor swept area". Turbinstorlekarna ökar dock ständigt och därför får skillnaden mellan realitet och beräkningen alltid större. Således fokusera denna studien en areaviktad medelvindhastighet som heter rotorekvivalent vindhastighet. Den beräknar medelvindhastigheten med ett mindre osäkerhet eftersom den är baserad på flera vindmätningar på olika höjder. På grund av ett ojämt vindgradient i gränsskiktet visas resulten som funktion av densamma stailitetsparameter från likhetsteorien. Huvudresultaten för instabil gränskiktet är att navhöjdens vindhastigheten underskattar rotorekvivalent vindhastigheten med cirka 1 till 1,5 %. För det stabila gränskiktet finns olika resultaten: Två beräkningar visar att navhöjdens vindhastigheten överskattningar rotorekvivalent vindhastigheten med ungefär 1 % och en beräkning visa inget skillnad mellan medelvärdarna. Slutsatsen är att navhöjdens vindhastigheten är ett källa till ett högre modelleringsosäkerhet. Däremot visades att användningen av rotorekvivalent vindhastigheten leda till ett bättre prognosresultat. / In dieser Studie wurde einerseits die lokale ähnlichkeitstheorie mit zwei unterschiedlichen Ansätzen berechnet und andererseits die durchschnittliche Nabenhöhen- mit der rotor-äquivalenten Windgeschwin- digkeit verglichen. Dafür standen zwei unabhängige Datensätze zur Verfügung, welche Messwerte zwischen 98 und 173 m beinhalteten. Die Messungen wurden in Südschweden durch die Messtürme Hornamossen und Ryningsnäs in den Zeiträumen von Mai 2015 bis Juni 2017 und von November 2012 bis Februar 2012 erhoben. Das Ziel dieser Studie war es, die Ergebnisse aus den Berechnungen mit Referenzfunktionen zu validieren und den ausgewählten Ansätzen zu vergleichen. Für Messungen mit mehr als 100 m über der Erdoberfläche ist die lokale ähnlichkeitstheorie anstelle der ähnlichkeitstheorie basierend auf der konstanten Flussschicht besser geeignet, da letztere von einem konstanten Wert ausgeht. Die Ansätze, die hierfür verwendet wurden, sind die „Flux-Gradient Formulation“ und die „Gradient Richardson Number Formulation“. Mit beiden kann die universelle Impuls- und Wärmefunktion berechnet und als Funktion des Stabilitätsparameters dargestellt werden. Wie diese Studie zeigt, ist die Streuung um die Referenzkurven sehr klein für die „Gradient Richardson Number“ Ergebnisse im Vergleich zur „Flux-Gradient Formulation“. Dies liegt daran, dass sowohl der Stabilitätsparameter und die universellen Impuls- und Wärmefunktion nur von der Richardson-Zahl abhängen. Trotz der höheren Streuung für die „Flux-Gradient Formulation“ stimmen die Mediane der universellen Impulsfunktionen von beiden Datensätzen und die Referenzkurven überein. Das Gleiche gilt für die Ergebnisse der universellen Wärmefunktion basierend auf der „Flux-Gradient Formulation“, wenn der Mindestwert für den kinetischen Wärmefluss signifikant größer ist als für die universelle Impulsfunktion. Ausgangspunkt ist die Veröffentlichung von England & McNider 1995, welche die „Gradient Richardson Number Formulation“ dargestellt haben. Diese enthält zwei fehlerhafte Gleichungen, wovon eine einen Tippfehler aufweist und die andere auf einer fehlerhaften Herleitung basiert. Diese Arbeit stellt daher ebenso die korrigierten Gleichungen dar. Zusätzlich werden neue Gleichungen vorgestellt, bei denen nicht angenommen wird, dass die von England & McNider angenommenen Konstanten der empirischen Funktionen für die universelle Impuls- und Wärmefunktion den gleichen Wert haben. In der Windindustrie ist es üblich, dass die durchschnittliche Nabenhöhen-Windgeschwindigkeit als Durchschnittsgeschwindigkeit für die gesamte „rotor swept area“ angenommen wird. Diese Annahme weicht immer mehr von der Realität ab, weil Windkraftwerke kontinuierlich größer werden. Daher wird in dieser Arbeit auf eine flächengewichtete mittlere Windgeschwindigkeit mit der Bezeichnung Rotor-äquivalente Windgeschwindigkeit gearbeitet. Diese produziert realistischere Durchschnittswerte, weil sie Messungen von mehreren vertikal verteilten Messpunkten einbezieht. Aufgrund des sich verändernden Windgradientens in der Grenzschicht wird die Abweichung zwischen diesen beiden Geschwindig- keiten als Funktion der Schichtungsstabilität dargestellt. Die zentralen Ergebnisse dieser Studie zeigen zusammenfassend, dass bei labiler Schichtung die Nabenhöhen-Windgeschwindigkeit die Rotor-äquivalente Windgeschwindigkeit um etwa 1 % bis 1.5 % unterschätzt. Für die stabile Schichtung unterscheiden sich die Ergebnisse: Zwei Berechnungen zeigen, dass die Nabenhöhen-Windgeschwindigkeit die Rotor-äquivalente Windgeschwindigkeit um ca. 1 % überschätzt und eine andere Berechnung zeigt keinen Unterschied zwischen den Mittelwerten. Daraus kann gefolgert werden, dass die Nabenhöhen-Windgeschwindigkeit eine höhere Fehlerquelle aufweist. Im Gegensatz dazu liefert die rotor-äquivalente Windgeschwindigkeit genauere Prognosewerte.