Dissertations / Theses: 'Nitrogen budgets'

1

Watson, Christine A. "Nitrogen budgets in pluricompartmental systems." Thesis, University of Aberdeen, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.296512.

Full text

Abstract:

Increasing concern over the adverse environmental impact of intensive agriculture has led to pressure to develop more sustainable, integrated farming systems which have the potential to minimise the loss of nitrogen to the environment whilst maintaining productivity. Alternative systems include pluricompartmental systems, which combine more than one enterprise or species in a formalised design, such as a crop rotation or spatial arrangement e.g. agroforestry. Three approaches to nitrogen budgeting were developed and their ability to quantitatively describe nitrogen cycling in pluricompartmental systems tested. Budgets ranged in complexity from the EIO Budget, which accounted simply for purchases and sales of nitrogen over the farmgate, through the BIO Budget which included estimation of biological nitrogen fixation and attempted to partition losses into leaching and gaseous forms, to the TRIO Budget which also accounted for key soil processes. Unaccounted for N was attributed to leaching, however it is recognised that this is a predictor of leaching potential rather than actual loss. These approaches were tested in a range of systems; a mixed organic farm, a silvopastoral agroforestry system, organically and conventionally managed beef systems and a series of ley/arable rotations containing different proportions of ley. A simple model for predicting nitrogen fixation from yield was also developed and tested. The success of the different approaches was strongly dependent on the precise objective; whilst all the approaches were able to predict N use efficiency in economic terms, the TRIO Budget was likely to give the best estimate of potential N loss by leaching. The TRIO Budget was the only approach which quantified intercompartmental N fluxes, and it is suggested that this parameter may be a useful indicator of sustainability. Intercompartmental fluxes were particularly difficult to quantify in spatially pluricompartmental systems due to the importance of belowground processes in these systems.

APA, Harvard, Vancouver, ISO, and other styles

2

Eriksson, Hägg Hanna. "Nitrogen land-sea fluxes in the Baltic Sea catchment : Empirical relationships and budgets." Doctoral thesis, Stockholms universitet, Institutionen för tillämpad miljövetenskap (ITM), 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-32493.

Full text

Abstract:

In this thesis empirical relationships and modeling tools are used to describe the relationship between human activities and meso- and large scale riverine N fluxes from land to sea. On a large scale Paper I showed that by only having knowledge about human population size and runoff one can estimate the riverine export of DIN (r2= 0.76). In Paper II we included two other important anthropogenic N inputs, i.e. atmospheric deposition and primary emission (PE) from animals. In most of the catchments the PE from animals were larger than the PE from humans. Hence, development of livestock is important and increased animal protein consumption by humans might increase the riverine N export. Scenario analysis (Paper II) show that climate change is expected to both decrease and increase the riverine N export depending on which part of the catchment is modeled. In the southern and eastern parts of the Baltic Sea catchment there is large potential for N reductions from point sources (Papers III & V). The diffuse sources are more difficult to decrease and a reduction of mineral fertilizer does not always lead to reduced N loadings because the agricultural systems can buffer even a slight surplus (Paper III). There is inertia in the catchments which can be seen in for example in the northern part of the catchment. Here atmospheric N deposition is almost as high as in the southern part but the nitrogen flux from these rivers is not elevated. These northern river catchments have N exports of the same magnitude as the natural background (Paper IV), indicating that the atmospheric N deposition is retained in the system and probably taken up by N limited boreal forests. However, important reductions can be achieved in the agricultural sector by detailed management of the planted land and animal manure. The highest sensitivity is in catchments with high animal density and high specific discharge, primarily draining to Kattegat and Danish Straits (Paper II & IV).
At the time of doctoral dissertation the following publications were unpublished and had a status as follows: Paper 2: Manuscript. Paper 4: Manuscript

APA, Harvard, Vancouver, ISO, and other styles

3

Halpop, John W. "Nitrogen and Energy Budgets of Production Ewes on Summer Range in Southwestern Utah." DigitalCommons@USU, 1988. https://digitalcommons.usu.edu/etd/4086.

Full text

Abstract:

Nitrogen (N) and energy budgets for free-roaming ewes were quantified on mountain summer range in southwestern Utah in 1986 and 1987. Diet quality (%N), in vitro organic matter digestibility (IVOMD), and energy were estimated with the use of five esophageally fistulated ewes. Excretion rates of N and energy to feces and urine were measured by total collection from five nonfistualted ewes. Total intake N(gN/(MBW*d-1) tracked intraseasonal changes of dietary N percent but was apparently buffered by fluctuations in dry matter intake. In each year, total urine N was closely related to dietary N concentration, r2=0.97 (1986) and r2=0.89 (1987). Total N excreted via feces varied as a function of dry matter output rather than fecal N concentration. Consumption of gross energy (GE) paralleled dry matter intake in both years of the study, r2=.99. Fecal energy excretion (kcal/(MBW*d-1) was associated with dry matter output while urine energy varied with little amplitude across both grazing seasons. In both years, absolute values for metabolizable energy (ME) and nitrogen balance indicated that the sheep were in a positive nutritional state throughout the grazing season. ME levels calculated by difference were consistently higher than when determined by DE X 0.82, since the gaseous products of fermentation were not accounted for in difference determinations. Ratios of estimated intake versus maintenance levels of nitrogen and energy were calculated for each grazing season under study. The data suggest that in 1986, N was relatively more limiting in early summer, while energy was relatively more limiting at the end of the season. Digestible organic matter intake appeared to be below maintenance requirements in September, 1986. In 1987, relative amounts of both nutrients paralleled each other throughout the grazing season and were above maintenance, with the exception of the September trial when both nitrogen and energy were below calculated maintenance levels.

APA, Harvard, Vancouver, ISO, and other styles

4

James, Andrew Gordon. "The feeding ecology of and carbon and nitrogen budgets for Engraulis capensis in the southern Benguela ecosystem." Doctoral thesis, University of Cape Town, 1988. http://hdl.handle.net/11427/8409.

Full text

Abstract:

Bibliography: leaves 179-231.
The two main schools of thought regarding the diets of intermediate microphagous clupeids are: A) that they are herbivorous and B) that they are omnivorous, but consume mainly zooplankton. The former view has been employed to explain their abundance in upwelling areas, since their purported ability to efficiently utilise the primary producers shortens the pelagic food chain to 1 or 2 links. The literature concerning the trophic ecology of some commercially important clupeids is reviewed and it is concluded that few are true phytophagists. Most are omnivorous and derive the bulk of their energy from zooplankton. Results indicating that these fish are herbivorous are largely due to inadequate sampling strategies and analytical techniques. The results of field work show that Engraulis capensis feeds selectively upon meso- and macro-zooplankton. Laboratory experiments supported these findings. Prey are selected on the basis of size and particulate feeding is the dominant mode of intake when the' fish are presented with a mixed size assemblage of prey. Engraulis capensis cannot filter feed on particles less than 0.200mm maximum dimension, and there is a threshold size of approximately 0.700mm when feeding behaviour switches from filter to particulate feeding. Particulate feeding produced faster clearance rates than filtering, and the Cape anchovy feeds at maximum efficiency over most of their prey size spectrum.

APA, Harvard, Vancouver, ISO, and other styles

5

van, der Lingen Carl David. "The Feeding ecology of, and carbon and nitrogen budgets for, sardine sardinops sagax in the Southern Benguela upwelling ecosystem." Doctoral thesis, University of Cape Town, 1999. http://hdl.handle.net/11427/17510.

Full text

Abstract:

Bibliography : pages 178-202.
Combined laboratory and field studies were employed to examine the feeding ecology of sardine Sardinops sagax in order to evaluate conflicting hypotheses regarding the trophic position of clupeoids in upwelling ecosystems, and to compare the trophodynamics of sardine with those of the co-occurring anchovy Engraulis capensis. Carbon and nitrogen budget models constructed using data from these studies were used to quantify the effect of particular food environments upon sardine growth. Sardinops sagax is primarily a filter-feeder, with food particles <1230μm total length eliciting a filtering response while larger particles elicit particulate-feeding at low concentrations and filter-feeding at high concentrations. This species is able to retain cells as small as 13μm, feeds at near-maximum efficiency when filterfeeding, and displays size-selectivity during particulate-feeding. Significant linear relationships between respiration rate and swimming speed obtained for sardine demonstrate that filter-feeding is the most energetically cheap feeding mode. Although omnivorous, sardine absorbs carbon and nitrogen more efficiently from zooplankton than from phytoplankton. Gastric evacuation follows an exponential pattern in sardine, and is influenced by food type; phytoplankton is evacuated faster than zooplankton. Feeding periodicity in sardine is size dependent; small fish show a feeding peak at, or around, sunset whereas larger fish appear to feed continuously. Estimates of daily ration range between 0.99 to 7.58% wet body mass.d-¹, depending on fish size and food type. Sardine stomach contents are numerically dominated by small particles, principally dinoflagellate phytoplankton, but the majority of the sardine's dietary carbon is derived from zooplankton, principally small calanoid and cyclopoid copepods. The budget models indicate that sardine is capable of positive growth under most of the trophic conditions it is likely to encounter in the southern Benguela upwelling system. The classical hypothesis that the high abundance of clupeoids in upwelling ecosystems results from their phytophagy is rejected; like anchovy, sardine are primarily zoophagous. However, these two species are trophodynamically distinct and show resource partitioning on the basis of prey size; sardine consume small zooplankton whilst anchovy consume large zooplankton. This difference is likely to contribute to regime shifts observed between these two species.

APA, Harvard, Vancouver, ISO, and other styles

6

Randall, Benjamin. "Characterisation and quantification of the fluxes of particulate and dissolved nitrogen in the unicellular diazotroph crocosphaera watsonii : towards a closed nitrogen budget." Electronic Thesis or Diss., Sorbonne université, 2019. http://www.theses.fr/2019SORUS685.

Full text

Abstract:

Les flux importants de la phase N dissoute, qui renseignent sur les bilans globaux en N des diazotrophes individuels, sont mal compris. Cela est particulièrement vrai des diazotrophes récemment découverts, qui peuvent ne pas fonctionner selon des paradigmes préétablis. Crocosphaera watsonii est un de ces diazotrophes, que l'on trouve largement répandu dans les océans subtropicaux. Nous caractérisons ici les flux d'azote à la diazotrophie de Crocosphaera, y compris les flux de NO3-, NH4 + et de N organique dissous (DON). Nous visons également à utiliser nos résultats pour évaluer la précision des tests biologiques de fixation du N2 couramment utilisés. Nous avons d'abord évalué l'utilisation de NO3- par Crocosphaera. Pour ce faire, des cultures discontinues de Crocosphaera ont été cultivées à long terme avec NO3-, en mesurant l'absorption de NO3-, son effet sur la diazotrophie, la croissance de la culture et d'autres paramètres physiologiques importants. Nous avons trouvé peu d'absorption sans effet sur les paramètres évalués, y compris la diazotrophie. Nous avons ciblé la disponibilité de la lumière comme paramètre important. Entre les conditions de culture de sous-saturation (SSL) et de lumière saturante (SL), nous avons constaté une augmentation de l'acquisition de N, de l'acquisition de C et du taux de croissance cellulaire dans les conditions de SL. De plus, nous avons constaté une absorption du DON sur une période de 24 heures, avec une plus grande adoption dans le scénario SSL (42% contre 7%). Il y avait un plus grand flux de NH4 + dans le support dans le SSL. En utilisant une approche isotopique, nous avons trouvé que 2,5 à 3,5% de l'azote récemment fixé étaient exsudés 24h. Notre évaluation de l'exactitude de la méthodologie a révélé que les incubations de 15N2 sous-estimaient la fixation de N2 alors que le test de réduction à l'acétylène était surestimé
Diazotrophy exists as a source of fixed N in the ocean, affecting processes like the marine food web. Important fluxes of the dissolved N phase, which inform the overall N budgets of individual diazotrophs, are poorly understood. This is especially true of recently discovered diazotrophs which may not function under pre-established paradigms. One such diazotroph is Crocosphaera watsonii, which is found widespread throughout sub-tropical oceans. Here we characterise N fluxes consequent to diazotrophy for Crocosphaera, including fluxes of NO3-, NH4+, and dissolved organic N (DON). We also aim to use our results to assess the accuracy of commonly used biological N2 fixation assays. We first assessed the use of NO3- by Crocosphaera. To do this, batch cultures of Crocosphaera were grown long term with NO3-, measuring uptake of NO3- uptake its effect on diazotrophy, culture growth and other important physiological parameters. We found little uptake with no effect on the assessed parameters, including diazotrophy. We next focussed on flux of DON and NH4+ in continuous cultures regulated for conditions such as temperature, light, and pH. We targeted light availability as an important parameter. Between culture conditions of sub-saturating (SSL) and saturating light (SL), we found an increase in N acquisition, C acquisition and cell growth rate in the SL condition. Furthermore, we found an uptake of DON over a 24h period, with greater uptake in the SSL scenario (42% v.s. 7%). There was greater flux of NH4+ into the medium in the SSL. Using an isotopic approach, we found 2.5-3.5% of recently fixed N was exuded 24h. Our assessment of the accuracy of methodology found that 15N2 incubations underestimated N2 fixation while the acetylene reduction assay overestimated. Overall, 15N2 incubations were more reliable when factoring in fluxes of dissolved N. Our findings represent new perspectives into the importance of fluxes of dissolved N to N budgets of Crocosphaera watsonii

APA, Harvard, Vancouver, ISO, and other styles

7

Bristow, Corben Emerson. "Experimental freshwater cage aquaculture: Short term effects on carbon, nitrogen and phosphorus budgets and the metabolism of a boreal shield lake." Thesis, University of Ottawa (Canada), 2006. http://hdl.handle.net/10393/27114.

Full text

Abstract:

We conducted an experiment to determine the effects of cage aquaculture on the functional properties of a lake. We installed a commercial aquaculture operation into a lake located within a pristine headwater region of the boreal shield. We used a before-after control-impact design to evaluate the weight of evidence for causal effects. We quantified sinks, sources and exchanges of carbon, nitrogen and phosphorus to the lake and presented this information in a budget format. We then calculated retention rates for these chemicals and compared them to integral amounts of carbon, nitrogen and phosphorus accumulating in the water column. We also measured removal rates (sedimentation) of these elements from the water column and transformation rates (primary production) within the water column. We found that the amounts of nitrogen and phosphorus retained in the lake increased dramatically during farm operation. With the exception of an increase in particulate carbon, we did not observe an accumulation of these chemicals in the water column. We did however observe lake wide increases in carbon and nitrogen sedimentation. Primary production increased significantly in the aquaculture-impacted lake and the period of peak productivity shifted to later in the summer. We discuss our results in the context of consequences to aquatic life and source water and we provide some recommendations for management.

APA, Harvard, Vancouver, ISO, and other styles

8

Michori, Peter K. "Nitrogen budget under coffee." Thesis, University of Reading, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.333405.

Full text

APA, Harvard, Vancouver, ISO, and other styles

9

Lernbecher, Vincent. "Swedish Nitrogen Flows : A national budget of anthropogenically induced reactive nitrogen." Thesis, KTH, Hållbar utveckling, miljövetenskap och teknik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-289176.

Full text

Abstract:

Nitrogen is a fundamental element in all forms of life and a crucial component of our agricultural productivity and global food security. However, excess nitrogen caused by human activity poses a serious threat to the environment and human health. Understanding human influences on the nitrogen cycle are therefore essential for sustainable management of the nutrient. The flows of anthropogenically influenced and created reactive nitrogen in Sweden are examined in this study. Human-induced sources and mechanisms associated with nitrogen are quantified and illustrated in several charts constructed with material flow analysis (MFA) methodology. Swedish society is divided into sectors of agriculture, industry, consumption, and waste management and the quantified nitrogen flows interacting with each system are used to highlight areas of interest. Results show considerable impacts stemming mainly from the food system, starting with agricultural use of mineral and organic fertilizer. Emissions of ammonia to air from animal husbandry and leakage of nitrogen to waterways are the biggest losses in the agricultural sector. The driving force behind the large agricultural losses is first and foremost the consumption pattern of households. Emissions of nitrogen oxides from traffic and industrial processes also make up a large part of the total nitrogen load. The recovery rate of nutrients that ultimately end up in the waste sector is relatively low and most of the nitrogen is denitrified in wastewater treatment plants.
Kvävgas i form av N2 finns i överflöd i jordens atmosfär. Cirka 78% av luften är i själva verket N2. För att levande organismer ska kunna använda det atmosfäriska kvävet måste den först brytas ned och bindas till antingen väte, kol eller syre. I sin reaktiva form fungerar elementet som en grundläggande byggsten för alla levande varelser. Den naturliga processen som förvandlar oanvändbart atmosfäriskt kväve till dess reaktiva former kallas kvävefixering och utförs av bakterier. I ekosystemet avgör därmed tillgängligheten av reaktivt kväve vegetationens tillväxt och är därmed en begränsande faktor för jordbruket. Denna begränsning upphörde med uppfinningen av industriell kvävefixering i form av Haber-Bosch processen där ammoniak utvinns ur luften. Sedan dess har miljontals ton av reaktivt kväve införts till den naturliga kvävecykeln och orsakat störningar med allvarliga konsekvenser. I Sverige började arbetet med att reducera överskottet av reaktivt kväve på allvar under 1980-talet då näringsinnehållet i Östersjön redan hade överskridit hållbara nivåer. Sedan dess har ny lagstiftning som behandlar frågan införts både på nationell nivå och på EU- nivå. Insatserna har påverkat minskningen av kväveöverskottet, men många belastningsgränser överskrids fortfarande. För att samordna strategier och lagstiftning kring den komplexa kvävecykeln och ytterligare begränsa miljöbelastningen krävs en mer integrerad, holistisk strategi och ett gemensamt ramverk. Denna studie skapades med detta i åtanke och med målet att öka medvetenheten om kvävets belastning på miljön. I studien kvantifierades mänskligt inducerade källor och mekanismer associerade med kväve och illustrerades i flera diagram konstruerade med en materialflödesanalys (MFA) metod. Det svenska samhället är indelat i fyra sektorer: jordbruk, industri, konsumtion och avfallshantering. De resulterande kväveflödena används sedan för att lyfta fram intressanta områden och skapa en översiktsbild. Resultaten visar betydande flöden som huvudsakligen härrör från livsmedelssystemet, med början i jordbruksanvändning av mineral- och organisk gödselmedel. Utsläpp av ammoniak till luft från djurhållning samt läckage av kväve till vattendrag utgör de största förlusterna i jordbrukssektorn. Den drivande kraften bakom det stora inflödet av gödselmedel och orsaken till jordbruksförlusterna är först och främst hushållens konsumtionsmönster. Utsläpp av kväveoxider från trafik och industriprocesser utgör även en stor del den totala kvävebelastningen. Återvinningsgraden av näringsämnen som slutligen hamnar i avfallssektorn är relativt låg och majoriteten av kvävet denitrifieras i reningsverk. Slutsatsen är att det nuvarande tillståndet för antropogent kväveflöde i Sverige är linjärt och att nytt kväve kontinuerligt måste tillföras till systemet.

APA, Harvard, Vancouver, ISO, and other styles

10

Batson, Jacqulyn A. "Denitrification and a Nitrogen Budget of Created Riparian Wetlands." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1284968767.

Full text

APA, Harvard, Vancouver, ISO, and other styles

11

Lee, Kun-seop. "Nitrogen budget of the seagrass Thalassia testudinum in the western Gulf of Mexico /." Digital version accessible at:, 1998. http://wwwlib.umi.com/cr/utexas/main.

Full text

APA, Harvard, Vancouver, ISO, and other styles

12

Mckenzie, Rebecca. "Fluxes of nitrogen in a semi-natural ecosystem." Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/fluxes-of-nitrogen-in-a-seminatural-ecosystem(14fa4deb-56e1-4cf4-b5bf-2afb74081cc8).html.

Full text

Abstract:

Nitrogen (N) is known to be a limiting factor in peatlands and as such, the vegetation present has adapted to living in low N conditions. This makes such ecosystems particularly vulnerable to increases in the deposition of reactive N (Nr), which may result in significant changes to its biodiversity and biogeochemistry. Since the industrial revolution, the amount of anthropogenic Nr globally has increased from ~15 Tg N y-1 in the 1860’s to ~187 Tg N y-1 in 2005, and is estimated to reach ~267 Tg N yr-1 by 2050 (Galloway et al. 2004, Galloway et al. 2008). Consequences include acidification, loss of biodiversity, changes in vegetation, N-saturation, eutrophication, health impacts and the release of greenhouse gases.Objectives of this thesis were (i) to measure key components of the N-budget at Auchencorth Moss, a Scottish moorland, for a two year period (Jan 2009 – Dec 2010) and (ii) to compare current deposition rates with those measured 14/15 years previously. Annual fluxes of N inputs were estimated from measurements of wet only deposition, estimates of N-fixation deposition and from atmospheric deposition modelled from hourly concentrations of N containing gases and aerosols. Exports were estimated from stream measurements and from atmospheric emissions modelled from hourly concentrations. Organic N is often an underreported part of the N-cycle, but the results presented here suggest it is an important part of the N story. An attempt to identify (dissolved organic nitrogen) DON compounds in both precipitation and stream water was made using GC×GC-NCD. Ten unique compounds were detected, of which only five could be identified: pyrrole, benzonitrile, dodecylamine, N-nitrosodipropylamine and decylamine. Pyrrole, benzonitrile and three unknown compounds were present in both precipitation and stream samples. Ammonia (NH3) fluxes were measured over a 7 month period in 2009 using a wet-chemistry gradient system with online analysis and calculated with the aerodynamic gradient method. The results were used to refine a bi-directional dynamic exchange model. Several parameters were updated, including an increased stomatal emission potential from 180 to 350, a reduction of the minimum cuticular resistance (Rw,min) used to calculate Rw from 20 s m-1 to 15 s m-1 and an increase in the leaching rate (Kr¬) from the leaf surfaces from -0.01 to -0.1 s-1. The exchange parameterisations used to estimate HNO3, HONO and the aerosol compounds were taken from the literature and earlier studies at the site.Overall, Auchencorth was found to accumulate N, with deposition exceeding export by -1.61 kg N ha-1 yr-1. The main N deposition was from NH3, followed by wet deposition of ammonium. DON, which is not routinely included in N budgets, contributed 6.5% of total deposition. The largest loss of N was as DON via the stream with N losses of -5.31 kg N ha-1 yr-1 or 71.8% of total export. Between 1995 and 2009/2010, deposition decreased by 0.81 kg N ha-1 yr-1, with the wet deposition of inorganic nitrogen decreasing by 25.2%, but dry deposition increasing by 12.5%. DON, N2O and N-fixation were not included in the comparison as they were not measured in 1995.This thesis has demonstrated that DON is an important parameter in the overall N budget, and should be routinely measured when assessing the N status of ecosystems.

APA, Harvard, Vancouver, ISO, and other styles

13

Kathawaroo, Deshika. "A nitrogen budget for the Cape Metropolitan area : is nitrogen enrichment occurring in the soils of remnant patches of lowland fynbos?" Bachelor's thesis, University of Cape Town, 2000. http://hdl.handle.net/11427/25968.

Full text

Abstract:

Anthropogenic activities create nitrogenous pollutants which threaten the existence of lowland fynbos, comprising 92 Red Data Book species and 14 Cape Flats endemics. A regional Nitrogen budget was constructed through the collation of existing data for the Cape Metropolitan Area. An NOx inventory has revealed that vehicles emit 66 % of the total NOx emissions into the atmosphere. The maximum potential N deposition is 184 kg N ha⁻¹ yr⁻¹ for the lowlands. Air quality in an industrial area, Goodwood, has revealed that a large proportion of the emissions remain in the air and have the potential to deposit 33 kg N ha⁻¹ yr⁻¹. Atmospheric N deposited on unimpacted coastal fynbos is 1.99 kg ha⁻¹ yr⁻¹. Thus remnant patches of lowland fynbos are threatened by replacement by grasslands as a result of atmospheric N inputs. Direct measurements of soil N pools are required, since signals of leaching in rivers may be premature as N accumulating in soil pools may not yet have reached saturation point. NH₃ emissions, wet and dry N deposition, and atmospheric transport models are required in order to construct a N budget for the CMA. Thereafter, appropriate preventative strategies can be devised in order to prevent the replacement of remnant patches of lowland fynbos.

APA, Harvard, Vancouver, ISO, and other styles

14

Trimmer, Mark. "The role of bottom sediments in the nitrogen budget of the Great Ouse estuary." Thesis, University of Essex, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.361018.

Full text

APA, Harvard, Vancouver, ISO, and other styles

15

Sandu, Simonel Ioan. "Evaluation of ozone treatment, pilot-scale wastewater treatment plant, and nitrogen budget for Blue Ridge Aquaculture." Diss., Virginia Tech, 2003. http://hdl.handle.net/10919/11271.

Full text

Abstract:

Sustainable tilapia production at Blue Ridge Aquaculture (BRA) is constrained by availability of high quality replacement water. I developed a pilot-scale wastewater treatment system to treat and reuse effluent presently discharged. An initial study was conducted to determine the response of the BRA waste stream to ozone application. Dosages of 6.9, 4.8 and 2.4 g O3 were applied for 30 minutes to 35 L of settled effluent. Optimum ozone dosage and reaction time, ozone transfer efficiency, ozone yield coefficient, degree of pollutant removal, and other ozone and water quality parameters were determined. Most results suggested that the maximum process feasibility limit for ozone contact time was approximately 9 minutes at an applied ozone concentration of 23g/m3 (6.9 g O3 dose). Formation of foam increased solids and COD removal up to three times. Poor removal or accumulation of DOC and TAN was observed, indicating the need for biological treatment following ozonation. Next, I evaluated a pilot station treatment train including sedimentation, microscreen filtration, fluidized bed denitrification, ozonation, aerobic biological oxidation in a trickling filter, and jar-test chemical flocculation. Significant improvements were found regarding solids, COD, cBOD5, NO3--N, TKN, and turbidity. Removal of foam after ozonation improved ozonation efficacy and pollutant removal. A nitrogen budget for the BRA facility was derived, indicating that 35% of the nitrogen applied in feed was assimilated in fish. I evaluated the possible impact of residual inorganic nitrogen forms from treated effluent upon fish in the recirculating systems. I found that less than 1% of the TAN produced would return the recovered stream, and that the existing biological contactors can remove it. Evaluation of TAN fate indicated that 84% was oxidized in biofilters, 14% was oxidized by passive nitrification, and 1% was removed by water exchange. For NO3-N, I determined that 56% was removed by passive denitrification and 44% by daily water exchange. The pilot station design was effective for removing organics and nutrients, and can serve as the basis for scale-up for treating and reusing the entire BRA effluent stream.
Ph. D.

APA, Harvard, Vancouver, ISO, and other styles

16

Vogt, Esther. "Nitrogen fluxes at the landscape scale : a case study in Scotland." Thesis, University of Edinburgh, 2012. http://hdl.handle.net/1842/6244.

Full text

Abstract:

Nitrogen (N) fluxes show a substantial variability at the landscape scale. Emissions are transferred by atmospheric, hydrological and anthropogenic dispersion between different landscape elements or ecosystems, e.g. farms, fields, forests or moorland. These landscape N fluxes can cause impacts to the environment, such as loss of biodiversity. The aim of this study is to illustrate how landscape N fluxes can be quantified by integrating atmospheric and fluvial fluxes in a Scottish landscape of 6 km x 6 km that contains intensively managed poultry farming, extensively managed beef and sheep farming, semi-natural moorland and woodland. Atmospheric ammonia (NH3) emissions of two deep pit free range layer poultry houses were estimated by high time-resolution measurements of NH3 concentrations and meteorological variables downwind of layer poultry houses and the application of an inverse Gaussian plume model. Atmospheric NH3 concentrations and deposition fluxes across the study landscape were studied at a resolution of 25 m x 25 m. The approach combined a detailed landscape inventory of all farm activities providing high resolution NH3 emission estimates for atmospheric dispersion modelling and an intensive measurement programme of spatial NH3 concentrations for verifying modelled NH3 concentrations. The spatially diverse emission pattern resulted in a high spatial variability of modelled mean annual NH3 concentrations (0.3 to 77.9 μg NH3 m-3) and dry deposition fluxes (0.1 to >100 kg NH3-N ha-1 yr-1) within the landscape. Annual downstream fluxes and variation in spatial concentration of dissolved inorganic nitrogen (NH4 + and NO3 -) and dissolved organic nitrogen (DON) were studied in the two main catchments within the study landscape (agricultural grassland vs. semi-natural moorland catchment). The grassland catchment was associated with an annual downstream total dissolved nitrogen (TDN) flux of 14.4 kg N ha-1 yr-1, which was 66% higher than the flux of 8.7 kg ha-1 yr-1 from the moorland catchment. This difference was largely due to the NO3 - flux being one order of magnitude higher in the grassland catchment. The contribution of DON to the TDN flux varied between the catchments with 49% in the grassland and 81% in the moorland catchment. Fluvial and atmospheric N fluxes were combined to derive N budgets of the two catchments. Agricultural activities accounted for the majority of N input to the catchments, with atmospheric deposition also playing a significant role, especially in the moorland catchment. Both catchments showed large stream export fluxes compared to their net import which suggests that their capacity of N storage is limited. This thesis quantifies major N fluxes in a study landscape and shows their large spatial variability. Agricultural activities dominate landscape N dynamics. The work demonstrates the importance of considering landscape N variability when attempting to reduce the environmental impact of agricultural activities.

APA, Harvard, Vancouver, ISO, and other styles

17

Rutz, Charlotte. "The energy budget of green apple aphids (Aphis pomi de Geer) (Homoptera: Aphididae), as influenced by nitrogen fertilization /." [S.l.] : [s.n.], 1993. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=10176.

Full text

APA, Harvard, Vancouver, ISO, and other styles

18

Pandeya, Hemant Raj. "Carbon and nitrogen flux dynamics in highly weathered tropical mango soils: Effect of leaf litter and nitrogen fertiliser." Thesis, Queensland University of Technology, 2022. https://eprints.qut.edu.au/232828/1/Hemant%20Raj_Pandeya_Thesis.pdf.

Full text

Abstract:

This thesis is a comparative study of carbon and nitrogen flux dynamics following sole and combined application of mango leaf litter mulch and inorganic fertiliser in highly weathered tropical mango orchard soils. In doing so, the thesis investigated litter decomposition dynamics and litter carbon mass balance and provided baseline datasets of seasonal and annual reactive nitrogen losses (through hydrological and gaseous pathways) under the tropical environmental conditions of Northern Territory Australia.

APA, Harvard, Vancouver, ISO, and other styles

19

Pasakdee, Sajeemas. "Nitrogen and water management in organic vegetable production in California : implications for soil properties, plant nutrient, and farm budget analysis /." Diss., Digital Dissertations Database. Restricted to UC campuses, 2006. http://uclibs.org/PID/11984.

Full text

APA, Harvard, Vancouver, ISO, and other styles

20

Pardon, Lénaïc. "Modelling of the nitrogen budget of oil palm plantations to help reduce losses to the environment. Case study in Sumatra, Indonesia." Thesis, Paris, Institut agronomique, vétérinaire et forestier de France, 2017. https://researchonline.jcu.edu.au/52952/1/52952-pardon-2017-thesis.pdf.

Full text

Abstract:

Humanity faces the challenges of urgently decreasing the environmental impact of agriculture, shifting diets and increasing food production. Oil palm is a tropical perennial crop emblematic of these challenges. While its cultivation can be associated with environmental impacts, oil palm can produce 3 to 7 t of edible oil ha⁻¹ in optimal conditions, which is 7 to 10 fold higher than in annual oil crops. In this context, improving palm oil production sustainability is crucial for both reducing negative environmental impacts and ensuring food security. Application of synthetic nitrogen (N) fertilisers was identified as a major source of environmental impacts associated with the cultivation of oil palm. Life cycle assessments of palm oil have already been performed to help quantify impacts and identify potential improvements of management practices. However, the only available emission models to estimate N losses to environment are generally valid for annual crops and temperate climate conditions. The use of such general models in life cycle assessment may lead to very uncertain results or to low sensitivity of assessments to management practices. The overall objective of this research work was to help identify management practices to reduce N losses in the environment. The core of the work was hence to develop a model that estimates all N losses in oil palm plantations, while being sensitive to management practices. The study focused on N fluxes in industrial oil palm plantations on mineral soils. We performed four steps in order to complete the objectives of this research work. First, we conducted a literature review of all the existing knowledge about N fluxes and losses in plantations. Second, we compared 11 existing models that may be used to predict N losses in plantations. Third, we performed an in-depth Morris's sensitivity analysis of one of the models, the APSIM-Oil palm process-based model. Fourth, we used all the information identified in the previous chapters, together with expert knowledge, to build IN-Palm, an agri-environmental indicator for N losses in oil palm plantations. We used the INDIGO® method and the fuzzy decision tree modelling approach to develop IN-Palm, and we validated this indicator using a field dataset of N leaching from a plantation in Sumatra, Indonesia. Our literature review and model comparison showed that oil palm peculiarities may impact significantly N dynamics and losses. We identified research gaps and uncertainties about N losses, their drivers and the modelling of oil palm peculiarities. We identified the main drivers of N losses and yield in the APSIM-Oil palm process-based model. We built IN-Palm, which uses 21 readily available input variables to estimate each N loss pathway. IN-Palm predictions of N leaching were acceptable, and IN-Palm has shown efficient to help testing management changes. This research constitutes a comprehensive synthesis of the available knowledge and models for N fluxes and losses in oil palm plantations. One of the main results is a novel agri-environmental indicator, IN-Palm, operationally-oriented, sensitive to local practices and environmental conditions, as well as potentially useable as an emission model for holistic approaches such as life cycle assessment. The INDIGO® method and fuzzy decision tree modelling approach were shown to be very well adapted for building agri-environmental indicators in contexts of knowledge scarcity. This indicator can be a useful base for further research about using agri-environmental indicators to reduce uncertainty in life cycle assessment, and for future adaptations for other tropical perennial crops.

APA, Harvard, Vancouver, ISO, and other styles

21

Pardon, Lénaïc. "Modelling of the nitrogen budget of oil palm plantations to help reduce losses to the environment. Case study in Sumatra, Indonesia." Thesis, Paris, Institut agronomique, vétérinaire et forestier de France, 2017. http://www.theses.fr/2017IAVF0018/document.

Full text

Abstract:

L’humanité fait face aux défis urgents de réduire l’impact environnemental de l’agriculture, de changer les régimes alimentaires et d’accroître la production alimentaire. Le palmier à huile est une plante pérenne tropicale emblématique de ces défis. Alors que sa culture peut être à l’origine d’impacts environnementaux, le palmier à huile peut produire, en conditions optimales, 7 à 10 fois plus d’huile alimentaire que les cultures oléagineuses annuelles. Dans ce contexte, améliorer la durabilité de la production d’huile de palme est crucial, tant pour réduire les impacts environnementaux négatifs que pour garantir la sécurité alimentaire. L’application de fertilisants azotés (N) a été identifiée comme une source majeure d’impacts environnementaux dus à la culture du palmier. Des analyses de cycle de vie de l’huile de palme ont été réalisées pour quantifier les impacts et identifier des améliorations de pratiques agricoles. Cependant, les seuls modèles d’émissions disponibles pour estimer les pertes de N dans l’environnement sont généralement valides pour les cultures annuelles et en climat tempéré. L’utilisation de tels modèles dans l’analyse de cycle de vie peut mener à des résultats très incertains ou à une faible sensibilité aux pratiques. L’objectif global de ce travail de recherche était d’aider à l’identification de pratiques pour réduire les pertes de N dans l’environnement. Le cœur du travail était le développement d’un modèle estimant toutes les pertes de N dans les plantations, tout en étant sensible aux pratiques. L’étude s’est concentrée sur les flux de N dans les plantations de palmiers sur sols minéraux. Nous avons réalisé quatre étapes pour mener à bien cette recherche. Premièrement, nous avons mené une revue de littérature de tout le savoir existant concernant les flux et pertes de N dans les plantations. Deuxièmement, nous avons comparé 11 modèles existants, pouvant être utilisés pour prédire les pertes de N dans les plantations. Troisièmement, nous avons réalisé une analyse de sensibilité de Morris approfondie du modèle mécaniste APSIM-Oil palm. Quatrièmement, nous avons construit IN-Palm, un indicateur agri-environnemental pour les pertes de N dans les plantations. Nous avons utilisé la méthode INDIGO® et l’approche de modélisation par arbres de décisions flous pour développer IN-Palm, et nous avons validé cet indicateur en utilisant des mesures de lixiviation de N d’une plantation à Sumatra, Indonésie. Notre revue de littérature et notre comparaison de modèles ont montré que les particularités du palmier à huile peuvent affecter significativement les dynamiques et pertes de N. Nous avons identifié des manques de recherche et des incertitudes sur les pertes de N, leurs déterminants et la modélisation des particularités du palmier. Nous avons identifié les déterminants des pertes de N et du rendement dans le modèle mécaniste APSIM-Oil palm. Nous avons développé IN-Palm, qui utilise 21 variables d’entré facilement accessibles pour estimer chaque voie de perte de N. Les prédictions de lixiviation de N par IN-Palm étaient acceptables, et IN-Palm s’est montré efficace pour tester des changements de pratiques agricoles. Cette recherche constitue une synthèse exhaustive des connaissances et modèles disponibles pour les flux et pertes de N dans les plantations. L’un des principaux résultats est un nouvel indicateur agri-environnemental, IN-Palm, sensible aux pratiques et conditions locales, de même qu’utilisable en tant que modèle d’émission dans des approches holistiques. Cet indicateur peut être une base utile pour de futures recherches sur l’utilisation d’indicateurs agri-environnementaux pour réduire l’incertitude des analyses cycle de vie, et pour de futures adaptations à d’autres plantes pérennes tropicales
Humanity faces the challenges of urgently decreasing the environmental impact of agriculture, shifting diets and increasing food production. Oil palm is a tropical perennial crop emblematic of these challenges. While its cultivation can be associated with environmental impacts, oil palm can produce 3 to 7 t of edible oil ha-1 in optimal conditions, which is 7 to 10 fold higher than in annual oil crops. In this context, improving palm oil production sustainability is crucial for both reducing negative environmental impacts and ensuring food security. Application of synthetic nitrogen (N) fertilisers was identified as a major source of environmental impacts associated with the cultivation of oil palm. Life cycle assessments of palm oil have already been performed to help quantify impacts and identify potential improvements of management practices. However, the only available emission models to estimate N losses to environment are generally valid for annual crops and temperate climate conditions. The use of such general models in life cycle assessment may lead to very uncertain results or to low sensitivity of assessments to management practices. The overall objective of this research work was to help identify management practices to reduce N losses in the environment. The core of the work was hence to develop a model that estimates all N losses in oil palm plantations, while being sensitive to management practices. The study focused on N fluxes in industrial oil palm plantations on mineral soils. We performed four steps in order to complete the objectives of this research work. First, we conducted a literature review of all the existing knowledge about N fluxes and losses in plantations. Second, we compared 11 existing models that may be used to predict N losses in plantations. Third, we performed an in-depth Morris’s sensitivity analysis of one of the models, the APSIM-Oil palm process-based model. Fourth, we used all the information identified in the previous chapters, together with expert knowledge, to build IN-Palm, an agri-environmental indicator for N losses in oil palm plantations. We used the INDIGO® method and the fuzzy decision tree modelling approach to develop IN-Palm, and we validated this indicator using a field dataset of N leaching from a plantation in Sumatra, Indonesia. Our literature review and model comparison showed that oil palm peculiarities may impact significantly N dynamics and losses. We identified research gaps and uncertainties about N losses, their drivers and the modelling of oil palm peculiarities. We identified the main drivers of N losses and yield in the APSIM-Oil palm processbased model. We built IN-Palm, which uses 21 readily available input variables to estimate each N loss pathway. IN-Palm predictions of N leaching were acceptable, and IN-Palm has shown efficient to help testing management changes. This research constitutes a comprehensive synthesis of the available knowledge and models for N fluxes and losses in oil palm plantations. One of the main results is a novel agri-environmental indicator, IN-Palm, operationally-oriented, sensitive to local practices and environmental conditions, as well as potentially useable as an emission model for holistic approaches such as life cycle assessment. The INDIGO® method and fuzzy decision tree modelling approach were shown to be very well adapted for building agri-environmental indicators in contexts of knowledge scarcity. This indicator can be a useful base for further research about using agrienvironmental indicators to reduce uncertainty in life cycle assessment, and for future adaptations for other tropical perennial crops

APA, Harvard, Vancouver, ISO, and other styles

22

Kettering, Janine Verfasser], and Yakov [Akademischer Betreuer] [Kuzyakov. "Budget and fluxes of nitrogen in mountainous agroecosystems in a summer monsoonal climate under intensive land use / Janine Kettering. Betreuer: Yakov Kuzyakov." Bayreuth : Universität Bayreuth, 2012. http://d-nb.info/1059412756/34.

Full text

APA, Harvard, Vancouver, ISO, and other styles

23

Bythell, J. C. "A nitrogen budget for the Caribbean elkhorn coral Acropora palmata (lamarck) from the back-reef environment of Tague Bay reef, St. Croix, U.S. Virgin Islands." Thesis, University of Newcastle Upon Tyne, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.383984.

Full text

APA, Harvard, Vancouver, ISO, and other styles

24

Wellington, Christine. "A nutrient mass balance for nitrogen and phosphorous for the nearshore water of the west coast of Barbados, W.I., July 1996 to May 1997 /." Thesis, McGill University, 1999. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=29931.

Full text

Abstract:

A mass balance approach was used in an attempt to quantify nutrient flux to the nearshore at the West Coast, Barbados, W.I. Total nitrogen and total phosphorus levels of the groundwater at inland pumping stations and above beach margins, as well as in the water of the nearshore zone and approximately 2 km offshore, were obtained. Nearshore groundwater seepage rates and salinity data were also taken. This study attempted to use this raw data to estimate flushing rates, nutrient loading rates, and nutrient loss rates, to ultimately create a picture of the fate of nutrients as they travel in groundwater into the nearshore zone. Annual loading for the entire West Coast was calculated at 1.46 x 105 kg NO3---N for nitrogen and 1.19 x 103 kg PO4 3---P for phosphorus. Mean nutrient levels in groundwater above the beach margin were estimated at 969.83 muM for nitrogen and 3.63 muM for phosphorus. For nitrogen and phosphorus respectively, these levels were twice and three times higher than at the pumping stations farther inland; and there was also a fourfold and fivefold drop in nitrogen and phosphorus, respectively, in the nearshore zone relative to this groundwater above the beach margin. This indicated that the dense coastal population at the West Coast was adding significant amounts of nutrient to groundwater after it had left the inland pumping stations. There were no patterns of gradation in nutrient concentrations detected within the immediate nearshore, making completion of an accurate mass balance impossible, though indicating that there was significant advection of submarine groundwater offshore, beyond the study zone. This may contribute to the poor health of West Coast reefs, where sewage and fertiliser leaching and runoff are suspected as the primary sources for nutrient input to submarine groundwater to the south and northern parts of the West Coast, respectively.

APA, Harvard, Vancouver, ISO, and other styles

25

Borges, David AraÃjo. "UtilizaÃÃo de cepas de bactÃrias no cultivo intensivo de tilÃpia Oreochromis niloticus, sob sistema de renovaÃÃo zero Ãgua." Universidade Federal do CearÃ, 2006. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=7591.

Full text

Abstract:

CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior
O controle da qualidade da Ãgua em sistemas intensivo de cultivo de peixes Ã, via de regra, um dos pontos crÃticos para o sucesso do supracitado sistema. Os problemas mais comuns de qualidade de Ãgua nos sistemas em questÃo estÃo relacionados com depleÃÃo do oxigÃnio dissolvido, acÃmulo de matÃria orgÃnica e nitrogÃnio inorgÃnico, particularmente amÃnia. Bioremediadores ou bioincrementaÃÃo refere-se ao tratamento de poluentes ou detritos com o uso de microorganismos, como por exemplo, bactÃrias nitrificantes, as quais degradam as substÃncias indesejadas no sistema. A utilizaÃÃo desta biorremediaÃÃo vem sendo gradualmente aplicada em sistemas de recirculaÃÃo. Os benefÃcios sugeridos vÃo desde a remoÃÃo de nitrogÃnio inorgÃnico, fosfato e matÃria orgÃnica, a controle algal da Ãgua dos cultivos. O presente trabalho teve o objetivo de comparar o cultivo intensivo da tilÃpia Oreochromis niloticus, sob sistema de renovaÃÃo zero de Ãgua, com e sem inÃculo de cepas de bactÃrias. No experimento foram utilizados um total de 6 aquÃrios com capacidade de 180L e volume nominal de 160L, divididos em dois tratamentos âAâ (grupo controle) e âExâ (grupo com inÃculo bacteriano), neste ultimo sendo realizado 3 inoculaÃÃes semanais de bactÃrias,em dias alternados. Os aquÃrios foram povoados com juvenis de tilÃpia com peso mÃdio de 26,20 + 0,20 g, tendo sido os mesmos alimentados, diariamente, com raÃÃo com 35% de PB. Durante os 35 dias de cultivo diariamente foram registrados valores de pH, temperatura e oxigÃnio dissolvido. Semanalmente foram realizadas anÃlises de DBO, DQO, amÃnia total, nitrito, nitrato, ortofosfato e clorofila âaâ. Para a anÃlise do experimento, alÃm dos parÃmetros supracitados, foi utilizado um balanÃo de massa do nitrogÃnio e anÃlise de Ãndices zootÃcnicos como: crescimento dos indivÃduos, fator de conversÃo alimentar e sobrevivÃncia. Embora o tratamento âExâ tenha apresentado melhores resultados nos parÃmetros fÃsico-quÃmicos, no balanÃo de massa do nitrogÃnio e nos Ãndices zootÃcnicos, nÃo foi verificada diferenÃa estatÃstica entre os tratamentos âAâ e âExâ, a um nÃvel de significÃncia de 5%.
Control of water quality in intensive fish culture systems is offten the bottleneck for their successful operation. The most comon problems of water quality in those systems are related to oxigen depletion, organic matter and inorganic nitrogen accumulation, particularly ammonia. Bioaugmentation refers to the treatment of wastes or detrits using microorganisms, as an exemple nitrifing bacterias, which degradate undisareble substances in the system. The employment of bioaugmentation is becoming an option for recirculating fish cultures. Sugested benefits goes from inorganic nitrogen, phosfate and organic matter removal, to algae control in fish culture water. The aim of this experimental was to compare the intensive culture of tilapia Oreochromis niloticus with zero exchage water with and without biocultures introduction. The experiment consisted of 6 aquariums of 180L and nominal volume of 160L, separeted in two diferent treatments âAâ and âExâ; the first one the control grup and the second one the test. Those aquariums were stocked with juvenils of tilapia weiting 26,20 + 0,20g, and fed with 35%CP. During 35 days of culture none water have been chaged in the system Three times a week biocultures were introduced only on treatment âExâ. Daily some fÃsico â chemical parameters were collected like: pH, temperature and dissolved oxigen; and every week BOD,COD, total ammonia, nitite, nitrate, phosfate and chlorophyll âaâ were analized from âAâ and âExâ treatments. For the experimental evaluation, besides those forementioned parameters, nitrogen budget, and some zootecnical index like: growth rate, food conversion rate and survival were utilized. Although âExâ treatment has shown better results than âAâ treatment, after a statistical analises we concluded that there were no diference between those two treatments

APA, Harvard, Vancouver, ISO, and other styles

26

Borges, David Araújo. "Utilização de cepas de bactérias no cultivo intensivo de tilápia Oreochromis niloticus, sob sistema de renovação zero água." reponame:Repositório Institucional da UFC, 2006. http://www.repositorio.ufc.br/handle/riufc/18252.

Full text

Abstract:

BORGES, David Araújo. Utilização de cepas de bactérias no cultivo intensivo de tilápia Oreochromis niloticus, sob sistema de renovação zero água. 2006. 50 f. : Dissertação (mestrado) - Universidade Federalç do Ceará, Centro de Ciências Agrárias, Departamento de Engenharia de Pesca, Fortaleza-CE, 2006
Submitted by Nádja Goes (nmoraissoares@gmail.com) on 2016-07-12T13:03:29Z No. of bitstreams: 1 2006_dis_daborges.pdf: 228199 bytes, checksum: 33b54c2614fad5363ad43ae8d399c8d4 (MD5)
Approved for entry into archive by Nádja Goes (nmoraissoares@gmail.com) on 2016-07-12T13:04:07Z (GMT) No. of bitstreams: 1 2006_dis_daborges.pdf: 228199 bytes, checksum: 33b54c2614fad5363ad43ae8d399c8d4 (MD5)
Made available in DSpace on 2016-07-12T13:04:07Z (GMT). No. of bitstreams: 1 2006_dis_daborges.pdf: 228199 bytes, checksum: 33b54c2614fad5363ad43ae8d399c8d4 (MD5) Previous issue date: 2006
Control of water quality in intensive fish culture systems is offten the bottleneck for their successful operation. The most comon problems of water quality in those systems are related to oxigen depletion, organic matter and inorganic nitrogen accumulation, particularly ammonia. Bioaugmentation refers to the treatment of wastes or detrits using microorganisms, as an exemple nitrifing bacterias, which degradate undisareble substances in the system. The employment of bioaugmentation is becoming an option for recirculating fish cultures. Sugested benefits goes from inorganic nitrogen, phosfate and organic matter removal, to algae control in fish culture water. The aim of this experimental was to compare the intensive culture of tilapia Oreochromis niloticus with zero exchage water with and without biocultures introduction. The experiment consisted of 6 aquariums of 180L and nominal volume of 160L, separeted in two diferent treatments “A” and “Ex”; the first one the control grup and the second one the test. Those aquariums were stocked with juvenils of tilapia weiting 26,20 + 0,20g, and fed with 35%CP. During 35 days of culture none water have been chaged in the system Three times a week biocultures were introduced only on treatment “Ex”. Daily some físico – chemical parameters were collected like: pH, temperature and dissolved oxigen; and every week BOD,COD, total ammonia, nitite, nitrate, phosfate and chlorophyll “a” were analized from “A” and “Ex” treatments. For the experimental evaluation, besides those forementioned parameters, nitrogen budget, and some zootecnical index like: growth rate, food conversion rate and survival were utilized. Although “Ex” treatment has shown better results than “A” treatment, after a statistical analises we concluded that there were no diference between those two treatments
O controle da qualidade da água em sistemas intensivo de cultivo de peixes é, via de regra, um dos pontos críticos para o sucesso do supracitado sistema. Os problemas mais comuns de qualidade de água nos sistemas em questão estão relacionados com depleção do oxigênio dissolvido, acúmulo de matéria orgânica e nitrogênio inorgânico, particularmente amônia. Bioremediadores ou bioincrementação refere-se ao tratamento de poluentes ou detritos com o uso de microorganismos, como por exemplo, bactérias nitrificantes, as quais degradam as substâncias indesejadas no sistema. A utilização desta biorremediação vem sendo gradualmente aplicada em sistemas de recirculação. Os benefícios sugeridos vão desde a remoção de nitrogênio inorgânico, fosfato e matéria orgânica, a controle algal da água dos cultivos. O presente trabalho teve o objetivo de comparar o cultivo intensivo da tilápia Oreochromis niloticus, sob sistema de renovação zero de água, com e sem inóculo de cepas de bactérias. No experimento foram utilizados um total de 6 aquários com capacidade de 180L e volume nominal de 160L, divididos em dois tratamentos “A” (grupo controle) e “Ex” (grupo com inóculo bacteriano), neste ultimo sendo realizado 3 inoculações semanais de bactérias,em dias alternados. Os aquários foram povoados com juvenis de tilápia com peso médio de 26,20 + 0,20 g, tendo sido os mesmos alimentados, diariamente, com ração com 35% de PB. Durante os 35 dias de cultivo diariamente foram registrados valores de pH, temperatura e oxigênio dissolvido. Semanalmente foram realizadas análises de DBO, DQO, amônia total, nitrito, nitrato, ortofosfato e clorofila “a”. Para a análise do experimento, além dos parâmetros supracitados, foi utilizado um balanço de massa do nitrogênio e análise de índices zootécnicos como: crescimento dos indivíduos, fator de conversão alimentar e sobrevivência. Embora o tratamento “Ex” tenha apresentado melhores resultados nos parâmetros físico-químicos, no balanço de massa do nitrogênio e nos índices zootécnicos, não foi verificada diferença estatística entre os tratamentos “A” e “Ex”, a um nível de significância de 5%.

APA, Harvard, Vancouver, ISO, and other styles

27

Brédoire, Félix. "Impacts of global change on the biogeochemical cycling of water and nutrients in the soil-plant system and consequences for vegetation growth in south-western Siberia." Thesis, Bordeaux, 2016. http://www.theses.fr/2016BORD0033/document.

Full text

Abstract:

Dans un contexte de changement global, prédire l’évolution de la productivité de la végétation dans le sud-ouest (SO) Sibérien reste un défi du fait d’incertitudes fortes sur les processus régulant la disponibilité en eau et en nutriments. Nous avons mis en évidence des relations entre cycles biogéochimiques, climat et propriétés du sol sur six sites contrastés.La croissance radiale des tiges de peuplier est principalement sensible au bilan hydrique du sol en forêt de steppe, au sud du SO Sibérien, alors qu’elle est stimulée par de hautes températures estivales en sub-taïga, dans le nord de la région.Des mesures de terrain et des simulations du bilan hydrique du sol ont montré que la fonte des neiges est importante pour la recharge des réserves hydriques du sol au sud. Au nord, ces réserves sont souvent rechargées en automne. La fonte des neiges est alors associée à du drainage. De plus, au nord, une épaisse couverture de neige protège le sol du gel en hiver. La distribution des racines fines est plus profonde en forêt de steppe qu’en sub-taïga, impactée par le déficit hydrique et le gel.L’homogénéité du statut en phosphore (P) des sols dans le SO Sibérien montre qu’il n’est pas encore très impacté par la pédogénèse. Les stocks en P élevés, notammen tles formes disponibles pour les plantes, suggèrent que le P n’est pas et ne sera pas limitant dans le futur.La décomposition des litières aériennes et la libération de l’azote (N) sont plus rapides en sub-taïga qu’en forêt de steppe. Un fort drainage pourrait expliquer un transfert profond du N dans les sols en sub-taïga. Cependant ces sols semblent efficaces pour retenir le N, limitant les pertes pour le système sol–plante
Predicting the evolution of vegetation productivity in SW Siberia in the contextof global change remains a challenge because of major uncertainties concerningthe biogeochemical cycling and the plant-availability of water and nutrients. Weprovided insights on their relation to climate and soil properties, investigating sixcontrasting sites.Aspen stem radial growth is mainly sensitive to soil water budget in the foreststeppezone established in the south of SW Siberia while it is enhanced by highsummer temperatures in the sub-taiga, in the north of the region.Field measurements and water budget simulations revealed that snow-melt isimportant re-filling soil water reserves in the south. In the north, these reservesare mostly re-filled in autumn and snow-melt is associated with drainage. A thicksnow-pack also prevents soil from freezing in winter in the sub-taiga. Water deficitand soil freezing largely impact the distribution of fine roots within the soil profilewhich is deeper in forest-steppe than in sub-taiga.The homogeneous soil phosphorus (P) status in the region investigated revealedthis nutrient has not been yet very impacted by contrasting soil processes. High Pstocks, and in particular plant-available forms, suggest P is unlikely to be limitingunder current and future conditions.By contrast, we found differences in nitrogen (N) status. Above-ground litterdecay and the release of N occurs faster in sub-taiga than in forest-steppe. Higherdrainage may explain deeper N transfer in sub-taiga soils. However, sub-taiga soilsalso seem to be efficient in retaining N, limiting losses from the soil–plant system

APA, Harvard, Vancouver, ISO, and other styles

28

Li, Po-Lin, and 李博霖. "Nitrogen Budgets and Nitrous Oxide Flux from Constructed Wetland." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/d562c5.

Full text

Abstract:

碩士
嘉南藥理科技大學
環境工程與科學系暨研究所
99
This study monitored influent flow and effluent, water quality, nitrogen content of plant and sediment, and N2O flux in a constructed wetland system built in Chia Nan University of Pharmacy & Science from December 2007 to May 2010. Sampling frequency was once a month and twenty-seven data by actual gas sampling. The constructed wetland system in Chia Nan University of Pharmacy & Science which operated for tertiary treatment of campus wastewater was composed by subsurface flow (SSF) (1450 m2) and free water surface flow (FWS) wetland (2200 m2). The purpose of this study was to estimate N2O flux, to figure out the major environmental factors for influencing N2O fluxes by statistical analyses and to estimate the results of nitrogen budgets for wetland. The average of influent flow was 316 m3/d, the average of hydraulic loading was 0.087 m/d, and the average of hydraulic retention time was 3.14 d for the wetland in this study. The TN concentrations of the influent ranged from 2.95 to 52.66 mg/L, 0.99 to 22.27 mg/L in effluent and the average of removal efficiencies reached 56±28％. The N2O flux which ranged from 3.83 to 87.37 μg N2O/m2/h for the SSF wetland was monitored, and it was monitored from －6.10 to 128.78 μg N2O/m2/h for the FWS wetland. The average of N2O flux was 33.58±11.32, 30.78±14.41 and 32.38±11.75 μg N2O/m2/h for the SSF, FWS and SSF-FWS wetland. In order to estimate the N2O flux accurately, it used the day and night correction factor ( α ), the existence of plants ( β ) and percentage coverage of plants ( γ ) to assess the Average flux of N2O. There are significant differences for the average flux of N2O for each sample, thus it discovered the main affected factors in water temperature, containing nitrogen substances (NH4-N, NO2-N, NO3-N) , BOD, ORP and pH by principal component analysis and stepwise multiple regression. Finally, it established the functions formula. The results were significantly related to the temperature and average fluxes of N2O. Therefore, it was calculated that the temperature correction factor between 1.047 and 1.085 by Modified Arrhenius equation. The results demonstrated that the nitrogen content in plant were 77.9, 41 and 55.7 g N/m2/year by above-ground and below-ground primary production and the nitrogen rate in plant. It also estimated the result of nitrification and denitrification cycle with nitrogen accumulation flux which was 737.9, 158.9 and 388.9 g N/m2/year by nitrogen budgets. Finally, the results estimated the average fluxes of N2O (1,336.67 mg N2O/m2/ year, 575.94 mg N2O/m2/ year) in Chia Nan University of Pharmacy & Science and the area of SSF and FWS in Taiwan. It predicted that the average fluxes of N2O were 65,496 g N2O/year and 866,213 g N2O/ year for SSF and FWS wetland in Taiwan. It transformed the results to the average fluxes of N2O for GWP were 5,323,106 g CO2-C/ year and 70,399,554 g CO2-C/ year for constructed wetland in Taiwan.

APA, Harvard, Vancouver, ISO, and other styles

29

Nimmo, Jeffrey. "Whole Farm Nutrient Budgets of Two Dairy Farms in Atlantic Canada." 2011. http://hdl.handle.net/10222/14330.

Full text

Abstract:

Whole farm nutrient budgets (WFNB) enable producers to link dairy herd management with traditional field nutrient management plans. The objective of this study was to calculate WFNBs of nitrogen, phosphorus, and potassium (N, P, and K) at a commercial farm in New Brunswick and in Prince Edward Island. Reliable estimates of N fixation from alfalfa and red clover on the farms were obtained with adjustments to the Høgh-Jensen et al. (2004) dry matter conversion models. The farms had surpluses of N, P, and K. Both farms imported feed as well as nutrient inputs for crop production. Surpluses of all nutrients were typical in comparison to WFNBs of similar dairy farms; however, the nutrient use efficiencies were low. The imported manure and fertilizer used in the crop production components contributed to surpluses of N and P which could likely be reduced to improve overall farm nutrient use efficiency.

APA, Harvard, Vancouver, ISO, and other styles

30

"Molybdenum Biogeochemistry in an Evolutionary Context: Nitrogen Assimilation, Microbial Storage and Environmental Budgets." Doctoral diss., 2011. http://hdl.handle.net/2286/R.I.9049.

Full text

Abstract:

abstract: Molybdenum (Mo) is a key trace nutrient for biological assimilation of nitrogen, either as nitrogen gas (N2) or nitrate (NO3-). Although Mo is the most abundant metal in seawater (105 nM), its concentration is low (<5 nM) in most freshwaters today, and it was scarce in the ocean before 600 million years ago. The use of Mo for nitrogen assimilation can be understood in terms of the changing Mo availability through time; for instance, the higher Mo content of eukaryotic vs. prokaryotic nitrate reductase may have stalled proliferation of eukaryotes in low-Mo Proterozoic oceans. Field and laboratory experiments were performed to study Mo requirements for NO3- assimilation and N2 fixation, respectively. Molybdenum-nitrate addition experiments at Castle Lake, California revealed interannual and depth variability in plankton community response, perhaps resulting from differences in species composition and/or ammonium availability. Furthermore, lake sediments were elevated in Mo compared to soils and bedrock in the watershed. Box modeling suggested that the largest source of Mo to the lake was particulate matter from the watershed. Month-long laboratory experiments with heterocystous cyanobacteria (HC) showed that <1 nM Mo led to low N2 fixation rates, while 10 nM Mo was sufficient for optimal rates. At 1500 nM Mo, freshwater HC hyperaccumulated Mo intercellularly, whereas coastal HC did not. These differences in storage capacity were likely due to the presence in freshwater HC of the small molybdate-binding protein, Mop, and its absence in coastal and marine cyanobacterial species. Expression of the mop gene was regulated by Mo availability in the freshwater HC species Nostoc sp. PCC 7120. Under low Mo (<1 nM) conditions, mop gene expression was up-regulated compared to higher Mo (150 and 3000 nM) treatments, but the subunit composition of the Mop protein changed, suggesting that Mop does not bind Mo in the same manner at <1 nM Mo that it can at higher Mo concentrations. These findings support a role for Mop as a Mo storage protein in HC and suggest that freshwater HC control Mo cellular homeostasis at the post-translational level. Mop's widespread distribution in prokaryotes lends support to the theory that it may be an ancient protein inherited from low-Mo Precambrian oceans.
Dissertation/Thesis
Ph.D. Geological Sciences 2011

APA, Harvard, Vancouver, ISO, and other styles

31

Ko, Francy, and 郭芳旭. "Biogeochemical Processes and Modeling Budgets of Carbon, Nitrogen and Phosphorus in the Chiku Lagoon." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/99471812245534257713.

Full text

Abstract:

碩士
國立中山大學
海洋地質及化學研究所
88
This study focuses on the biogeochemical processes and budgets of nutrients and organic carbon in the Chiku Lagoon through periodic observations and data analyses. During the study, samples were collected bimonthly for measuring hydrochemistry (temp., salinity, pH and DO), nutrients (DIN, DIP and D-Si), carbon (DOC, POC) from the lagoon-associated water bodies. Results of temporal and spatial variations were used to model carbon fluxes and budgets in the Chiku Lagoon. Space and time variations of nutrients and other chemical inputs and distributions were highly significant in the lagoon, particularly during the typhoon period. Thus, the steady-state biogeochemical modelling for carbon budgets is only valid for a time scale shorter than a season. The water exchange rate of Chiku Lagoon ranges from 1.1 day (June 1997) to 10.6 day (September 1997) with an annual mean of 5.8 day. As a result, the residue time of nutrients varies coincidentally with water exchange rate. The annual removal of terrestrial nutrient inputs from the lagoon system is 69.4%, 47%, 27.7% and 42%, respectively, for DIN, DON, DIP and DOP. Consequently, the nonconservative fluxes of dissolved inorganic phosphorus (ΔDIP) and total phosphorus (ΔP) from the lagoon are -0.11 and -0.14 mole m-2 yr-1, respectively. The negative nonconservative phosphorus fluxes indicate that the lagoon is an autotrophic system (p-r>0). The ΔP and ΔDIP are respectively equivalent to internal organic carbon sinks on 14.8 and 12.2 mole m-2 yr-1, which may be one of the largest values reported from world''s lagoons. The Chiku Lagoon is also estimated to uptake 4.7 mole m-2 yr-1 inorganic carbon through oyster calcification. Although a net nitrogen fixation occurred during some observed periods, denitrification was slightly greater than nitrogen fixation when both were integrated through the whole span of observation [(nfix-denit)= -1.04 mole m-2 yr-1].

APA, Harvard, Vancouver, ISO, and other styles

32

Ferguson, Kirsten Sheena. "The atmospheric nitrogen budget over the South African Highveld." Thesis, 2010. http://hdl.handle.net/10539/7677.

Full text

Abstract:

Molecular nitrogen is a highly abundant element in the atmosphere; it is stable and not very reactive. Anthropogenic activities have caused greater concentrations of nitrogen-containing compounds that are highly reactive and ultimately toxic. Reactive nitrogen concentrations have become a growing concern on the South African Highveld, with satellite images indicating very high nitrogen dioxide concentrations in the region. This study investigates the nitrogen budget on the Highveld through the analysis of the nitrogen species emitted into the atmosphere on a temporal scale as well as the atmospheric conversion, transport and removal of these species. Data was collected at Elandsfontein monitoring site, which is centrally located on the industrialised Highveld. The formation and interaction of nitric oxide (NO), nitrogen dioxide (NO2), and nitrate (NO3) are a major focus in the study. NOx concentrations are higher in winter (6.5 to 8.5 μg.m-3) as a result of stable atmospheric conditions. NO3 concentrations also peak during winter (3.5 to 5.5 μg.m-3), with a distinct biomass burning peak during July and August. Diurnally, NOx concentrations indicate a tall-stack industrial source, with concentrations peaking at midday. NO3 concentrations are higher at night and lower during the day, as during the day the NO3 radical is rapidly photolysed and nitrates cannot be produced. Case studies indicate that the conversion rate of NO to NO2 is highly variable as a result of varying atmospheric factors. These rates range from 11% to 59% per hour. Rates of dry deposition of NO, NO2 and NO3 are generally higher during winter as a result of higher concentrations and increased atmospheric stability, which prevents transport out of the region. Nitrogen is predominantly deposited as NO2 throughout the year, except during spring when NO3 deposition dominates. The total amount of nitrogen deposited to the Mpumalanga Highveld region is in the range of 6.7 to 13.1 kg ha-1 yr-1, which is well below the stipulated critical load value. Such deposition therefore does not pose significant threats to the natural environment on the Highveld. Between 4% and 14% of the total emitted nitrogen on the Highveld is deposited to the surface via wet and dry deposition. The remainder stays in the atmosphere and is advected out of the region.

APA, Harvard, Vancouver, ISO, and other styles

33

Brye, Kristofor Richard. "Carbon and nitrogen budget evaluation of natural and managed ecosystems." 1999. http://www.library.wisc.edu/databases/connect/dissertations.html.

Full text

APA, Harvard, Vancouver, ISO, and other styles

34

Liaw, Yeong-Tzonq, and 廖永綜. "Studies on the Nitrogen Budget and Cycle of Nanjenshan Forest Ecosystem." Thesis, 1998. http://ndltd.ncl.edu.tw/handle/16879480283411611260.

Full text

Abstract:

碩士
國立屏東科技大學
環境工程技術研究所
86
The objective of this project is to study the nitrogen budget and cycle of Nanjenshan forest ecosystem. At Kuhu experimental area, we explored soil properties, soil water contents, amounts and compositions of litterfall, mineralization of organic matter, dry and wet deposition and lake water quality. The results of soil property analysis showed that soils to be extremely acidic（pH4.3∼4.8）, fine-textured（clay and clay loam）, low in organic matter（1.0﹪∼5.34﹪）, total（0.06﹪∼0.17﹪）and available nitrogen, but high in "free" Fe and Al. Analyses of soil water samples found their pH values were between 4.6∼6.2, decreasing with increasing depth. The NH4+－N content was higher in surface layers than in bottom layers. Lake water and rain water had higher NO3- content than soil water. Nitrite wa not detectable. The amount of litterfall at the experimental site was 6.56 ton/ha*year. Leaves were the main litterfall component（66.47﹪）. There were two pronounced peaks of higher monthly litterfall, occurring during the growing season（from March to May）and during the typhoon period（from July to September）. The average nitrogen content of the litterfall was 1.04﹪and the total amounts accumulated by litterfall were 68.58 kg/ha*year. The results of incubation experiments indicated that the amounts of soil organic matter, inorganic nitrogen, NH4+－N and NO3-－N increased about 0.18﹪, 123.1 mg/kg, 76.3 mg/kg and 37.7 mg/kg per month, respectively. Based on these results, the annual inputs of NH4+－N and NO3-－N through mineralization were 2783.4 and 1357.3 kg/ha*year, respectively. The annual inputs of NO2-, NO3-, NH4+ and HNO3 from dry deposition were 0.03, 0.10, 0.012 and 1.53 ton/km2, respectively. While NO3- and NH4+ from wet desition were 4.13 and 3.87 ton/km2, respectively. According to this data, the amounts of nitrogen originating from dry and wet deposition were, respectively, 16.64 and 80.08 kg/ha*year. Lake water pH values ranged from 4.39 to 8.69. The respective concentrations of NO3-, NO2- and NH4+ were 0∼2.7, 0.03, and 0∼0.4 mg/L. Within the studied area, the main sources of nitrogen were dry deposition（16.64 kg/ha*year）, wet deposition（80.08 kg/ha*year）and decomposition of litterfall（73.54 kg/ha*year）. On the other hand, the nitrogen outputs were soil and sediment absorption（103.35 kg/ha*year）, plant uptake（68.58 kg/ha*year）, denitrification and release by soil water（1.33 kg/ha*year）. Since the soil were extremely acidic and low in available nitrogen, it is assumed that denitrification is negligible.

APA, Harvard, Vancouver, ISO, and other styles

35

(8775677), Megan N. Hughes. "Exploring the Effects of Cover Crop Use on Farm Profitability in Central Indiana." Thesis, 2020.

Find full text

Abstract:

Cover crop use provides a myriad of benefits to soil health. Despite strong agronomic evidence of the benefits of using cover crops, farmers have been slow to adopt cover crop systems. Surveys show that this is due to a lack of understanding on how cover crop use will impact the farm, and limited economic analysis on the effects of cover crop use on the farm.

In this thesis, a variable-rate nitrogen study was analyzed to determine the relationship between applied nitrogen fertilizer and corn yields, and how a cover crop treatment impacts that relationship. Data were obtained from a case farm in Central Indiana. Production information was then translated into a partial budget to see how the use of the different cover crop treatments impacted net return per acre for corn production on the farm. Net returns were analyzed using both historical corn and nitrogen prices and stochastic modelling.

Results showed that the final impact on farm net return per acre associated with adoption of a cover crop system varies among cover crop species. Implementing annual rye resulted in a negative change to net return; while cereal rye and an oats and radish blend resulted in a positive change to net return. When additional benefits of cover crop use; such as drought tolerance, carbon content, and erosion reduction; are included, all three cover crop species resulted in a substantial increase in net return. This information will be of interest to farmers as a source to draw upon when making decisions regarding their own farms. Further research is needed to fully understand the relationship between cover crop use and farm profitability, particularly for farms at the early stages of adoption.

APA, Harvard, Vancouver, ISO, and other styles

36

Johnson, Benjamin William. "Nitrogen in the Earth System: planetary budget and cycling during geologic history." Thesis, 2015. http://hdl.handle.net/1828/7755.

Full text

Abstract:

The distribution and geologic history of nitrogen on Earth is poorly known. Traditionally thought to be an inert gas, with only a small but important biologic cycle, geochemical investigation highlights that it can also be present in rocks and minerals. Even at low concentrations, the great mass of the solid Earth allows for the possibility of substantial N mass and cycling in the geosphere over Earth history. Thus, the assumption that N on the surface of the Earth has remained in steady state over Earth history can be questioned. The research goals of this thesis are to investigate the Earth System N cycle using both large- and small-scale approaches. I present a comprehensive literature compilation to ascertain the N budget of Earth. Determining the total abundance of N in all reservoirs of the Earth, including the atmosphere, oceans, crust, mantle, and core is crucial to a discussion of its cycling in the past. This budget study suggests that the majority of planetary N is likely in the core, with the Bulk Silicate Earth a more massive reservoir than the atmosphere. I also present experimental data and data from lunar samples as added context. As quantification of geologic N is difficult, I present research detailing the adaptation of a fluorometric technique common in aquatic geochemistry for use on geologic samples. I compare fluorometry analysis of geochemical standards to several other techniques: colourimetry, elemental analyzer mass spectrometry, and neutron activation analysis. Fluorometry generally behaves well for crystalline samples, and is a relatively quick and easy alternative to more expensive or intensive techniques. As a preliminary application, I have determined a N budget estimate for the continental crust based on analysis of crystalline crustal rocks and glacial tills from North America. This budget is consistent with published work, suggesting about 2 × 1018 kg N, or half a present atmospheric mass of N, is in the continental crust. I also present a geochemical study measuring N-isotopes and redox sensitive trace elements from a syn-glacial unit deposited during the the Marinoan Snowball Earth. Snowball Earth events were the most extreme glaciations in Earth history. The measurements presented herein are the first to quantify biologic activity via N-isotopes as well as the redox state of the atmosphere and ocean using trace elements from this intriguing time period in Earth history. The data suggests that there was active N- fixing in the biosphere, persistent but limited O2, nitrification, and nearly quantitative denitrification during the glaciation. After the glacial interval, O2 levels increased and denitrification levels dropped, indicated by near-modern δ15N values. The combined use of N-isotope with redox sensitive trace elements provides a more nuanced and comprehensive view in reconstructing past ocean and biologic conditions. Lastly, I present an Earth-system N cycle model with nominal results. Previous modelling efforts have agreed with the traditional notion that atmospheric N-levels have remained constant over geologic time. This is in contrast with modern geochemical evidence suggesting net transport of N from the surface into the mantle. The aim, in turn, of this model is to model N cycling over Earth history by explicitly incorporating both biologic and geologic fluxes. The model is driven by a mantle cooling history and calculated plate tectonic speed, as well as a prescribed atmospheric O2 evolution history. This approach is the first of its kind, to my knowledge, and produces stable model runs over Earth history. While tuning and sensitivity studies may be required for publishable results, nominal runs are compelling. In model output, atmospheric N varies by an factor of 2 − 3 over Earth history, and the availability of nutrients (i.e., PO4) exerts a strong control on biologic activity and movement of N throughout the Earth system. Such a planetary perspective on N serves as an entry point into discussions of planetary evolution as a whole. With the great increase in the number of discovered exoplanets, the scientific community is charged with developing models of planetary evolution and factors that promote habitability. Comparison of Earth to its solar system neighbours and future data on exoplanets will allow a system of evolution pathways to be explored, with the role of N expected to be prominent in discussions of habitability and planetary evolution.
Graduate
0996
0425
bwjohnso@uvic.ca

APA, Harvard, Vancouver, ISO, and other styles

37

Li, Yi-Jen, and 李宜珍. "Top-down vs. bottom-up control on the nitrogen budget of coral reef mesocosms." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/79190385381932616453.

Full text

Abstract:

碩士
中興大學
生命科學院碩士在職專班
99
The coral reef in Nanwan Bay undergoes the phase shift because of excessive nutrient loading and overfishing. Among them, nitrogen is an important element to affect the primary production. In order to establish the control model for coral degradation, we have investigated the nitrogen budget which states the nitrogen variation in temporal and space in this study. Almost 6% of system nitrogen was absorbed by the control producers of the coral reef mesocosm. The order of major nitrogen pools and their size rank are coral, phytoplankton and Dictyota cervicornis. However, 18% of system nitrogen was immersed by the producers of eutrophic coral reef mesocosm, and the order of the major nitrogen pools and their size rank were Codium edule, coral and phytoplankton. Compared to the herbivores effect in eutrophic mesocosm, the producers coexist with herbivores uptake 18% nitrogen and the producers without herbivores uptake 48%. The major nitrogen pools of existed herbivores are Caulerpa racemosa, Valonia aegagropila and coral, and the others are Codium edule, Caulerpa racemosa, Valonia aegagropila. The nitrogen recycling rate of coexist-herbivores reef is higher than the one doesn’t have herbivores. Our conclusion is that the nitrogen pools in the marine biota would change overtime if more unnecessary nutrients are loaded and the herbivores are removed from coral reef .The extra nitrogen would interfere the marine nitrogen cycling and further the global nitrogen cycle. In the future, the better coral reef management should be focused on the treatment and drain of the sewage, and the marine protected area for saving the coral reef can avoid phase shift.

APA, Harvard, Vancouver, ISO, and other styles

38

Chao, Hsiang-Yi, and 趙湘怡. "Comparison of nitrogen budget models between organic duck-rearing paddy field and conventional paddy field." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/89620203149456768773.

Full text

Abstract:

碩士
國立中興大學
生命科學院碩士在職專班
101
Owning to the rise of environmental consciousness and concerns about harmful effects of chemical compounds on the human body during agricultural processes around the whole world, the traditional rice-duck organic farming, the common agricultural methods in rural area between 1945 and 1971, becomes popular again in Taiwan. Different from conventional farming, the method of rice-duck organic farming uses ducks instead of pesticides and chemical fertilizers to feed pests and stamp paddy fields for suppressing weed and increasing the amount of dissolved oxygen in the water. Meanwhile, as a result of the reducing the amount of organic fertilizer, the duck organic farming can diminish the amount of nutrient overflowing into the environment. By building up the nitrogen budget model of rice-duck organic farming, the purpose of this study is to understand whether rice-duck organic farming can reduce the impact of fertilizer on the environment and maintain fertility by comparing nitrogen loss during the processes of cultivation and the capability of fixed nitrogen and the inhibition of apple snails and other pests between rice-duck organic and conventional farming. The results showed that the amount of nitrogen loss during the drainage is 57.79 g m-2 in duck paddy field and 62.79 g m-2 in conventional paddy field respectively. The amount of soil nitrogen was 8.7 g m-2　in duck paddy field and 21.4 g m-2 in conventional paddy field, which indicated the latter would release more nitrogen into the environment during the fallow. Nitrogen fixation was the dominating factor affecting the change in the amount of soil nitrogen. There were 64.06 g m-2 in duck paddy field nitrogen and 54.07 g m-2 in conventional paddy field of nitrogen fixed in the soil, which suggested rice-duck paddy field had better capability of nitrogen fixation in the soil. Without spilling tea-seed meal, the number of apple snails would be out of control; on the contrary, the number of apple snails in the duck paddy field had been maintained in 0-2 per m2 by duck feeding. In the conclusion, compared to conventional paddy farming, duck farming, without pesticide and chemical fertility, not only showed more control over the number of apple snails and other pests, but also reduced the environmental impact by the loss of nitrogen produced from agricultural activities, to likely achieve sustainability agricultural use.

APA, Harvard, Vancouver, ISO, and other styles

39

Rouse, Sarah E. "Effects of vegetation type on the hydrologic budget and inorganic nitrogen in recently established rain gardens." 2007. http://catalog.hathitrust.org/api/volumes/oclc/151109710.html.

Full text

Abstract:

Thesis (M.S.)--University of Wisconsin--Madison, 2007
Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 29-31).

APA, Harvard, Vancouver, ISO, and other styles

40

Hartmann, Linda. "Implementierung und bodenökologische Charakterisierung von Kurzumtriebsplantagen und Agroforstsystemen am Beispiel der Bioenergie-Regionen "Göttinger Land" & "Thüringer Ackerebene"." Doctoral thesis, 2014. http://hdl.handle.net/11858/00-1735-0000-0023-9962-F.

Full text

APA, Harvard, Vancouver, ISO, and other styles

41

Ojumu, Adefolake Mayokun. "Transport of nitrogen oxides and nitric acid pollutants over South Africa and air pollution in Cape Town." Diss., 2013. http://hdl.handle.net/10500/11911.

Full text

Abstract:

The deteriorating air quality in Cape Town (CT) is a threat to the social and economic development of the city. Although previous studies have shown that most of the pollutants are emitted in the city, it is not clear how the transport of pollutants from neighbouring cities may contribute to the pollution. This thesis studies the transport of atmospheric nitrogen oxides (NOx) and nitric acid (HNO3) pollutants over South Africa and examines the role of pollutant transport from the Mpumalanga Highveld on pollution in CT. The study analysed observation data (2001 - 2008) from the CT air quality network and from regional climate model simulation (2001 - 2004) over South Africa. The model simulations account for the influences of complex topography, atmospheric conditions, and atmospheric chemistry on transport of the pollutants over South Africa. Flux budget analysis was used to examine whether the city is a net source or sink for NOx and HNO3. The results show that north-easterly flow transports pollutants (NOx and HNO3) at low level (i.e., surface to 850 hPa) from the Mpumalanga Highveld towards CT. In April, a tongue of high concentration of HNO3 extends from the Mpumalanga Highveld to CT, along the southern coast. The flux budget analysis shows that CT can be a net sink for NOx and HNO3 during extreme pollution events. The study infers that, apart from the local emission of the pollutants in CT, the accumulation of pollutants transported from other areas may contribute to pollution in the city.
Environmental Sciences
M. Sc. (Environmental Science)

APA, Harvard, Vancouver, ISO, and other styles

Dissertations / Theses on the topic 'Nitrogen budgets'

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles