• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 176
  • 133
  • 56
  • 10
  • 6
  • 4
  • 4
  • 3
  • 2
  • 2
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 445
  • 445
  • 153
  • 122
  • 82
  • 78
  • 67
  • 66
  • 64
  • 52
  • 48
  • 47
  • 46
  • 45
  • 38
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
31

Reduction of Enteric Pathogens and Indicator Microorganisms in the Environment and Treatment Processes

Schmitz, Bradley William January 2016 (has links)
The reduction of pathogenic microorganisms is essential to minimize human health risks associated with the reuse, reclamation, and recycling of wastewater and the land application of biosolids (sewage sludge). The most advanced treatment technologies, as well as, the most representative methods and indicator organisms are necessary to ensure public safety. The goal of this dissertation is to assess advanced Bardenpho wastewater treatment technologies in regards to virus removal, suggest the most appropriate viral indicators of human fecal contamination and/or treatment process controls, and develop an updated method for enumerating Ascaris ova viability in land applied biosolids. Appendix A evaluates the incidence of 11 different virus types in sewage throughout a 12-month time period, and their subsequent reduction via advanced Bardenpho treatment processes. This study showed that wastewater treatment facilities utilizing advanced Bardenpho for secondary treatment are more effective at reducing viruses in wastewater than facilities utilizing conventional aeration basin and trickling filter processes. Appendix B develops a new method for determining the viability of Ascaris ova in land applied biosolids. In this method, early development stages prior to larval-development, are included in the estimation of potential viability. Comparisons between viability enumerations suggests that the conventional microscopy method, in which only ova containing motile larva are considered viable, underestimates the number of eggs that may progress to an infectious stage. Whereas, the method based on early-to-late stage development, considers the potential viability of all eggs, providing a more conservative approach.
32

Soil formation and soil moisture dynamics in agriculture fields in the Mekong Delta, Vietnam conceptual and numerical models

van Quang, Pham January 2009 (has links)
<p>Previous studies of agricultural conditions in the Mekong Delta (MD) have identified soil compaction as an obstacle to sustainable production. A conceptual model for soil formation was presented to demonstrate the link between soil hydrology and plant response. Detailed studies of soil moisture dynamics in agricultural fields were conducted using a dynamic process-orientated model. Pressure head and water flow were simulated for three selected sites during a year for which empirical data were available. Daily meteorological data were used as dynamic input and measured pressure head was used to estimate parameter values that satisfied various acceptance criteria. The Generalised Likelihood Uncertainty Estimation (GLUE) approach was applied for calibration procedures with 10,000 runs, each run using random values within the chosen range of parameter values. To evaluate model performance and uncertainty estimation, re-sampling was carried out using coefficient of determination (R2) and mean error (ME) as the criteria. Correlations between parameters and R2 (and ME) and among parameters were also considered to analyse the relationship of the selected parameter set in response to increases/decreases in the acceptable simulations. The method was successful for two of the three sites, with many accepted simulations. For these sites, the uncertainty was reduced and it was possible to quantify the importance of the different parameters.</p><p> </p>
33

Assessing the drought risk of oilseed rape to target future improvements to root systems

Hess, Linde January 2011 (has links)
The yield of UK’s commercial oilseed rape (Brassica napus) crops has not increased over the last three decades, while a significant increase in yield has been found in trials that test new varieties before they enter the market. It has been suggested that oilseed rape is susceptible to drought and that this may contribute to the poor yield of some commercial crops. A thorough literature review revealed that there is little information on the water relations of oilseed rape crops and in particular on root growth and function and thus no strong evidence to support the above hypothesis. The aim of this thesis was to investigate root function and water relations of oilseed rape to determine whether it is more sensitive to drought than wheat, a crop species grown in rotation with oilseed rape. The water relations of wheat (Triticum aestivum L. cv. Tybalt) and oilseed rape (Brassica napus L. cv. SW Landmark) were compared in a lysimeter experiment conducted in an open sided glass house to test the hypothesis that oilseed rape was more sensitive to drying soil than wheat. Plants were grown with or without irrigation at a population density equivalent to that of commercial field crops. Irrigated oilseed rape crops transpired more water than wheat crops and oilseed rape showed a greater reduction in growth when water was withheld. The onset of drought also occurred slightly earlier in oilseed rape. In a separate experiment the root hydraulic conductance of oilseed rape, measured on a root surface area basis, was about twice that of wheat (113.1 ± 20.0 mlNm-2Nh-1NMPa-1 for oilseed rape and 53. 5 ± 10.6 for wheat). These results suggest that oilseed rape needs a less dense root system for water extraction than wheat. In the above experiment plants were grown in relatively loose soil repacked into the lysimeters. It has been suggested that oilseed rape is particularly sensitive to soil compaction, which may be a common occurrence in commercial fields. Therefore the sensitivity of oilseed rape and wheat growth to compaction was compared in an experiment under well-watered conditions. Plants were grown in a controlled environment chamber in pots packed with soil at four different bulk densities. Although the root length, shoot mass, leaf area and stomatal conductance of oilseed rape were all reduced by soil compaction, oilseed rape was no more sensitive to soil compaction than wheat under these well-watered conditions. When soil dries it also hardens and high soil strength is known to impede root growth and alter plant-water relations. The hypothesis that oilseed rape is more sensitive to increasing soil strength than wheat was tested in an experiment in which soil bulk density and soil water content were varied to create a range of soil strengths. At low soil strength oilseed rape had a greater stomatal conductance than wheat, but as soil strength increased, stomatal conductance decreased to a greater extent in oilseed rape, indicating a more sensitive response. In dense or strong soil, plants often rely on pores created by earthworms or roots of the previous crop to explore the soil volume. The ability of oilseed rape and wheat to exploit soil pores to penetrate hard soil layers was compared in a pot experiment. A hard layer, comparable to a hard–pan in a cultivated field, was created at twelve centimetre depth of each pot by packing the soil to a bulk density of 1.5 g·cm-3 relatively loose soil at a bulk density of 1.1 g·cm-3 was present above and below the layer. In one treatment seven pores were drilled through the hard layer; controls had none. Presence of pores in the hard layer led to a significant increase in number of roots in the deeper soil, of 29% for wheat and 54% for oilseed rape. This project has shown that the physiological response to drought occurred earlier in oilseed rape than in wheat and that stomatal conductance and biomass production of oilseed rape reacted more sensitively to soil drying. However, water use by oilseed rape does not seem to be limited by the ability of its roots to explore the soil and transport water compared to wheat. The growth and distribution of roots under a range of soil conditions was as good as, if not better than, that of wheat. The implications of these findings for the commercial production of oilseed rape in the UK are discussed.
34

Impact du changement climatique sur la fréquence et l'intensité des sécheresses en Bretagne / Climate change impact on the frequency and intensity of droughts in Brittany

Lamy, Chloé 28 June 2013 (has links)
Par le passé la Bretagne a connu des épisodes de sécheresses très intenses. Peu communs pour des régions caractérisées par un climat océanique, ils ont eu des conséquences notables à l'échelle du territoire. De nombreuses activités socio-économiques sont ainsi apparues vulnérables face à ces évènements. Durant la sécheresse de 1976, l'agriculture fut particulièrement touchée, avec des pertes de récoltes importantes. La sécheresse est donc un risque important à l'échelle du territoire breton. Or, le changement du climat observé depuis plusieurs décennies amène des doutes quant à l'évolution des sécheresses en termes de fréquence et d'intensité. Cette thèse propose ainsi une analyse des caractéristiques des épisodes secs en Bretagne selon trois scénarios SRES du GIEC : B1, A1B et A2. Les sorties climatiques désagrégées utilisées ont été comparées, dans un premier temps, aux observations, afin de s'assurer de l'adaptabilité des jeux de données pour une analyse de ce type. Pour chacun des scénarios deux types de bilans hydriques ont été calculés. Ils permettent d'obtenir des valeurs de déficit d'évaporation, paramètre illustrant l'intensité des sécheresses, ainsi que des valeurs de réserve hydrique qui mettent en évidence les périodes d'assèchement et de recharge des sols. Les premiers bilans hydriques, de résolution de 8 km et au pas de temps mensuel, proposent une vision générale sur le comportement hydrique des sols bretons. Les seconds, de résolution kilométrique et au pas de temps journalier, apportent plus de précision quant aux secteurs vulnérables et à l'intensité probable des épisodes secs. On peut ainsi voir que des sécheresses exceptionnelles, similaires à celle de 1976, seraient régulièrement observées à la fin du 21ème siècle d'après le scénario A2. La comparaison avec un indice de sécheresse utilisé par Météo-France confirme les tendances régionales attendues au 21ème siècle d'après les trois scénarios SRES. Une approche agronomique est également proposée dans cette thèse afin d'apprécier les impacts de différentes types de culture sur la réserve hydrique des sols / Several extreme droughts occurred in Brittany during the past. Although they are rare in this oceanic region, their impacts are noticeable on the territory. Several socio-economical activities thus appeared to be vulnerable to dryness. In 1976, agriculture has been highly impacted during the drought, with important harvest loss. Droughts are therefore a significant hazard in Brittany. However, the changing climate observed for several decades raises issues on the way drought events might evolve in terms of frequency and intensity. This thesis offers an analysis of drought's characteristics in Brittany according to three IPCC's SRES scenarios : B1, A1B and A2. At first, disaggregated climate outputs have been compared to observed data to make sure of their suitability for this kind of study. For each scenario, two soil water balances have been calculated in order to get values of evaporation deficit, quantifying drought intensity, and of water storage, illustrating periods of emptying and filling of soils. Soil water balances calculated at a 8-km spatial resolution and monthly timescale displayed a general view of water content in Britannic's soils. Soil water balances calculated at a higher spatial resolution (1 km) and daily timescale brought more details than previous results in terms of intensity and localization of droughts. They revealed that droughts of similar intensity than that of 1976 might occur regularly at the end of the 21st century according to the A2 scenario. These results are confirmed by another drought index used by Météo-France. An agronomic approach is also developed in this thesis in order to reveal impacts of farming on soil water content
35

Variabilidade dos parâmetros da equação da condutividade hidráulica em função da umidade de um latossolo sob condições de campo. / Variability of the parameters of the hydraulic conductivity as a function of soil-water content equation for a field latosol.

Melo Filho, José Fernandes de 08 March 2002 (has links)
O presente trabalho foi realizado com o objetivo de quantificar e caracterizar a variabilidade espacial dos parâmetros equação K = Kq=0 exp(bq), determinada pelo método do perfil instantâneo. Nessa equação, Kq=0 é o coeficiente linear da reta lnK versus q ou a condutividade hidráulica (K) para o teor de água no solo (q) igual a zero e b o coeficiente angular. O experimento foi realizado no campus da "Escola Superior de Agricultura Luiz de Queiroz" - ESALQ/USP, localizado no município de Piracicaba (SP), em um Latossolo Vermelho Amarelo, álico, A moderado, textura média, (Typic Hapludox), moderadamente a bem drenado. A parcela experimental tinha um comprimento de 70 m e uma largura de 20 m; na sua linha central ao longo do comprimento foram considerados 50 pontos de observação, distanciados de 1 m entre si e, em cada um deles, instalados 5 tensiômetros eqüidistantes com suas cápsulas porosas localizadas às profundidades de 0,15; 0,30; 0,45; 0,60; 0,75 m. No ponto central de cada circunferência de 0,10 m de raio, na qual foram equidistantemente instalados 5 tensiômetros, foi instalada uma sonda de TDR para medida da umidade nas mesmas cinco profundidades em cada ponto de observação. As medições de umidade e potencial mátrico foram feitas durante 62 dias ou 1.370 horas, escolhendo se para este estudo o período compreendido entre os tempos de redistribuição 78 a 604 horas. Os resultados de umidade no solo (q), potencial mátrico (fm), lnKq=0 e b, foram submetidos à análise estatística exploratória e descritiva para verificação da distribuição e identificação de valores extremos. Também se calculou o número mínimo de subamostras necessárias para estimar o valor médio representativo dos parâmetros avaliados, para um nível de probabilidade de 95%, nos valores de 5, 10, 20 e 30% de coeficiente de variação em torno da média. Para os parâmetros lnKq=0 e b a análise do número de amostras foi também feita pela técnica "bootstrap". Análise da estabilidade temporal foi realizada com os dados de umidade no solo e potencial mátrico. Os resultados indicaram que o padrão de variabilidade dos parâmetros hídricos estudados (q, fm, b e lnKq=0 ) aumentou em profundidade, sendo os maiores coeficientes de variação aqueles apresentados pelo b. A variabilidade da umidade (q) foi baixa e aumentou com o tempo de redistribuição, enquanto que o potencial mátrico (fm), apresentou comportamento oposto, qual seja, variabilidade alta no início da redistribuição diminuindo para média no final da avaliação. Não houve relação entre os parâmetros quanto ao número de amostras necessárias para estimar a média, indicando que a utilização dos métodos para determinação de número de amostras pode gerar valores bem diferentes e que sua aplicação deve ser feita com prudência. Tanto a umidade do solo quanto o potencial mátrico apresentaram estabilidade temporal, o que permitiu identificar quais os locais mais indicados para a realização de amostragens com reduzido esforço e grande precisão. / This work was carried out with the objective of quantifying and characterizing the spatial variability of the K = Kq=0 exp(bq) equation parameters, determined by means of instantaneous profile method. In this equation, b is the slope and Kq=0 the intercept of the linear regression of lnK versus q. The experiment site is located at the Campus "Luiz de Queiroz", University of São Paulo, county of Piracicaba (SP), Brasil (22 o 42’ 30" S e 47 o 38’ 00" W) in a Typic Hapludox. The experimental plot dimensions were: length = 70 m and width = 20 m. In the central line of the length, 50 observation points 1m among themselves were considered each one with i) 5 mercury manometer tensiometers equally spaced in a 0.10 m radius circumference with their porous cups installed at 0.15, 0.30, 0.45, 0.60 and 0.75 m soil depths and ii) one TDR probe in the central point of the above circumference to measure soil-water content at the same five soil depths. Measurements of soil-water content and matric potential were made during 62 days of soil water redistribution, but the study was carried out using the redistribution time range from 78 to 604 hours. Results of soil-water content (q), matric potential (fm), lnKq=0 and b were analyzed by the exploratory and descriptive statistics in order to verify the data distribution and to identify outliers values. The minimum number of samples necessary to estimate the mean value of the assessed parameters was also calculated at a probability level of 5%, for variation coefficient values of 5, 10, 20 and 30%. For the parameters lnKq=0 and b, the analysis of number of sa mples was also made by using the "bootstrap" technique. Time stability analysis was used for soil-water content and matric potential data. The results have indicated that the variability of the studied hydric parameters (q, fm, b and lnKq=0 ) increased with soil depth, being the higher variation coefficients those of the parameters b. The soil water-content (q) variability was low and increased with the soil water redistribution time, whereas the matric potential had an inverse behavior, that is, high variability at the beginning of the soil water redistribution, decreasing to a medium one at the end of evaluation. There was no relation among parameters in terms of number of samples needed to estimate the mean, indicating that the use of methods to determine the number of samples can led to values very differents; hence the appliance of these methods should be done with caution. Both soil-water content and matric potential presented time stability, which permitted to identify the best points for future samplings with less effort and high precision.
36

VODNO FIZIČKA SVOJSTVA KARBONATNOG ČERNOZEMA U USLOVIMA NAVODNJAVANJA POVRĆA / Water physical properties of calcic chernozem invegetable production under irrigation

Mačkić Ksenija 12 May 2016 (has links)
<p>Zemlji&scaron;te i voda predstavljaju važne prirodne resurse koji su čovekovim kori&scaron;ćenjem bitno&nbsp;izmenjeni. Zemlji&scaron;te predstavlja neobnovljiv resurs čijom antropogenizacijom često dolazi do&nbsp;degradacije. Nestručnom ili nesavesnom primenom navodnjavanja uglavnom dolazi do pojave&nbsp;neželjenih posledica na zemlji&scaron;tu. U Vojvodini postoje i zemlji&scaron;ni i klimatski uslovi koji&nbsp;mogu prouzrokovati zaslanjivanje zemlji&scaron;ta u sistemima za navodnjavanje, naročito kada je&nbsp;voda za navodnjavanje mineralizovana. Pravilno (racionalno) navodnjavanje podrazumeva<br />dobro poznavanje zemlji&scaron;nih i klimatskih uslova područja i biolo&scaron;kih karakteristika gajenih&nbsp;biljaka. Kada se govori o promenama na zemlji&scaron;tu koje navodnjavanje može da izazove, treba&nbsp;odvojiti direktan uticaj vode i navodnjavanja od dejstva agrotehnike i ostalih pratećih činilaca&nbsp;i uslova.<br />Cilj istraživanja bio je da se utvrdi da li je dugogodi&scaron;nje navodnjavanje, u uslovima intenzivne&nbsp;proizvodnje povrća, uticalo na promenu morfolo&scaron;kih, vodno fizičkih i hemijskih svojstava&nbsp;karbonatnog černozema. Ukoliko se primenjuje racionalno navodnjavanje, uz uvažavanje&nbsp;hidropedolo&scaron;kih osobinama zemlji&scaron;ta i biolo&scaron;kih osobenosti gajenih biljaka, pretpostavka je&nbsp;da na ispitivanom zemlji&scaron;tu tipa černozem neće doći do degradacije in situ.<br />Istraživanja su obavljena na Oglednom polju Instituta za ratarstvo i povrtarstvo, Novi Sad, u&nbsp;Odeljenju za povrtarstvo na Rimskim &scaron;ančevima. Za potrebe analiza, otvoreno je osam&nbsp;pedolo&scaron;kih profila do dva metra dubine, četiri na zemlji&scaron;tu koje se u kontinuitetu navodnjava&nbsp;oro&scaron;avanjem od 1946. godine i četiri na zemlji&scaron;tu koje nikada nije navodnjavano. Za&nbsp;navodnjavanje je kori&scaron;ćena voda iz kopanih bunara. Za potrebe laboratorijskih istraživanja,&nbsp;uzeti su uzorci u poremećenom i prirodnom, neporemećenom stanju iz sredine utvrđenih&nbsp;genetičkih horizonata, kao i uzorci vode za navodnjavanje. Analizirani su fizička, vodno&nbsp;fizička i hemijska svojstva zemlji&scaron;ta, kao i hemijska svojstva vode za navodnjavanje,&nbsp;standardnim metodama koje su primenjuju za ovu vrstu istraživanja, kao i savremenim svetski&nbsp;priznatim metodama. Podaci su obrađeni metodom analize varijanse, a testiranje razlika&nbsp;između aritmetičkih sredina obavljeno je pomoću Dankanovog testa za nivo značajnosti 5%.<br />U cilju realnog sagledavanja uticaja navodnjavanja na vodno fizička i hemijska svojstva&nbsp;ispitivanog zemlji&scaron;ta, kori&scaron;ćena je i numerička multivarijantna (claster) metoda za simultanu&nbsp;analizu većeg broja podataka.vrednosti su ispod<br />graničnih vrednosti koje ukazuju da je u zemlji&scaron;tu do&scaron;lo do procesa zaslanjivanja.<br />Na osnovu rezultata istraživanja uočava se blagi trend pogor&scaron;anja hemijskih svojstava&nbsp;zemlji&scaron;ta pod uticajem navodnjavanja, te se stoga predlaže periodična kontrola kvaliteta, ne&nbsp;samo vode za navodnjavanje, nego i zemlji&scaron;ta. Dobijeni rezultati i zaključci predstavljaju&nbsp;osnovu za preduzimanje potrebnih mera u cilju očuvanja kvaliteta zemlji&scaron;ta.<br />Dobijeni rezultati istraživanja su pokazali da je do&scaron;lo do pogor&scaron;anja vodno fizičkih svojstva&nbsp;černozema, koje nije posledica navodnjavanja već drugih antropogenih i prirodnih faktora.<br />Utvrđeno je i blago pogor&scaron;anje hemijskih svojstava zemlji&scaron;ta kao posledica navodnjavanja&nbsp;zaslanjenom vodom. Ustanovljeno je povećanje pH vrednosti zemlji&scaron;ta, veći sadržaj kalcijum&nbsp;karbonata, usled navodnjavanja tvrdom vodom, i manji sadržaj humusa usled povećane&nbsp;mikrobiolo&scaron;ke aktivnosti i brže mineralizacije organske materije u uslovima povoljne&nbsp;vlažnosti zemlji&scaron;ta. Pod uticajem navodnjavanja, do&scaron;lo je do povećanja količine soli u&nbsp;zemlji&scaron;tu usled kori&scaron;ćenja zaslanjene vode za navodnjavanje. Iako je do&scaron;lo do blagog<br />povećanja saliniteta, izmerene vrednosti ukupne količine soli i ECe</p> / <p>Land and water are important natural resources, which are substantially altered by its use.<br />Land is a nonrenewable resource, whose anthropogenization often leads to degradation.<br />Improper or unconscious use of irrigation usually leads to detrimental effects on soil. In<br />Vojvodina there are soil and climate prerequisites that can cause soil salinization in irrigation<br />systems, especially irrigation water is saline. Correct (rational) irrigation means good<br />understanding of soil and climatic conditions of the area and the biological characteristics of<br />cultivated plants. Direct impact of water and irrigation on soil should be distinguished from<br />the effects of agricultural technology and other factors and conditions.<br />The aim of this study was to determine whether long-term irrigation, in intensive vegetable<br />production, caused the change of morphological, hydro physical and chemical properties of<br />carbonate chernozem. If rational irrigation is applied, in respect to hydropedological soil<br />properties and biological characteristics of cultivated plants, the assumption is that the<br />investigated chernozem soil will not show signs of degradation.<br />Investigations were carried out at the Experimental Field of the Institute of Field and<br />Vegetable Crops, Novi Sad, in the Department of Vegetable Crops. For the purpose of<br />analysis eight soil profiles were dug up to two meters deep, four on land that is irrigated by<br />sprinkling continuously since 1946 and four on land that has never been irrigated. Water for<br />irrigation was from the wells. For the purposes of laboratory tests, disturbed and undisturbed<br />soil samples were taken from the mid-determined genetic horizons, as well as irrigation water<br />samples. Physical, water physical and chemical soil properties and chemical properties of<br />irrigation water were analyzed by standard methods that are used for this type of research, as<br />well as the modern world-recognized methods. Data were analyzed using analysis of variance<br />and Duncan&#39;s LSD test for significance level of 5%. In order to objectively determine the<br />impact of irrigation on water physical and chemical properties of soil, multivariate numerical<br />(claster) method for the simultaneous analysis of large number of data was also used.<br />The results showed that there was deterioration in water physical properties of chernozem,<br />which, however is not the result of irrigation, but other anthropogenic and natural factors. It<br />was also found slight deterioration of chemical properties of the soil as a result of the<br />irrigation with saline water. It was found an increase in soil pH, higher content of calcium<br />carbonate due irrigation and lower humus content due to increased microbial activity and<br />faster mineralization of organic matter in favorable conditions of soil moisture. The increase<br />of salt amount was also found. Although there was a slight increase in salinity, total amount<br />of salt and ECe values are below the threshold for indicating the soil as saline.<br />The results indicate a mild trend of deterioration of chemical properties of soil under<br />irrigation. Therefore, periodic quality control is suggested, not only for irrigation water, but<br />also for the soil. The results and conclusions are the basis for taking the necessary measures in<br />order to preserve the soil quality.</p>
37

Soil Water Flux Estimates From Streaming Potential and Penta-Needle Heat Pulse Probe Measurements

Szafruga, Pawel J. 01 May 2014 (has links)
Better management of water resources is a growing concern with increasing stress on natural resources. Despite technological improvements in the past decades, a method to instantaneously measure soil water flux remains elusive, especially at a resolution adequate for monitoring natural processes (i.e. 1 mm d-1). The objectives of this research were to evaluate and improve two emerging methods for water flux estimates, 1) streaming potential and 2) heat pulse measurements, as tools to perform at these low flux rates. Streaming potential measures a voltage between two electrodes resulting from water with charged particles generating a current as it flows between the charged surfaces of the soil. Heat pulse measurements, performed with a penta-needle heat pulse probe (PHPP), measure the transport rate and direction of a heat pulse as it propagates from a central needle to surrounding thermistors through soil. Water moving past this sensor carries heat and this allows estimation of water flux from measured heat flux. Streaming potential experimentation demonstrated a clear voltage response to low flow rates. Unfortunately, inconsistent results coupled with measurement complications – susceptibility to electromagnetic noise, drifting, etc. – led to difficulties when trying to establish a congruent relationship between flow rate and voltage behavior. We concluded that the necessary steps to potentially improve measurement consistency made streaming potential less desirable to pursue compared to other emerging tools for water flux measurements. Heat pulse work focused on modifying design parameters to improve low flux rate determination. We tested the effect of increasing heater needle diameter (from 2 mm to 5 mm), increasing heating time (from 8 to 24 and 40 seconds), and doubling heat input (from 120 W m-1 to 240 W m-1) in saturated sand. Results indicated that using larger heater needles and higher heat input improve flux estimation but increasing heating time resulted in marginal improvement. By using a PHPP with a 5 mm heater needle, 24 second heating time, and 240 W m-1 heating input, fluxes were resolved down to 1 cm d-1. Refinement of calibration procedures and inconsistencies between probes used must be resolved if measurement resolution is to be improved further.
38

On farm yield and water use response of pearl millet to different management practices in Niger

Manyame, Comfort 15 May 2009 (has links)
Pearl millet [Pennisetum glaucum (L.) R.Br.] production under subsistence farmer management on the sandy soils of southwestern Niger is faced with many challenges, including declining soil fertility, highly variable and scarce rainfall and poor resource base of the peasant farmers in the region. This study was conducted to evaluate the potential of management to increase yield and water use efficiency of pearl millet grown on two farmers’ fields in Niger during two growing seasons, 2003 and 2004. The management practices tested were: 1) Five manure treatments (no manure, transported manure, current corralling, a year after corralling, and two years after corralling); 2) The microdose technology (20 kg di-ammonium phosphate ha-1, and 20 kg di-ammonium phosphate ha-1 + 10 kg urea ha-1); and lastly, 3) Three different pearl millet cultivars (Heini Kirei, Zatib, and ICMV IS 89305). In both growing seasons, manure had the greatest effect on the yield and water use of pearl millet at both sites. In 2003 grain yields were 389 kg ha-1 in the NM treatment and 1495 kg ha-1 in the C0 treatment at Banizoumbou whereas at Bagoua, the NM treatment had 423 kg ha-1 vs. 995 kg ha-1 in the C0 treatment. In 2004, the NM treatment at Banizoumbou had 123 kg ha-1 grain yield and the C0 treatment had 957 kg ha-1 whereas at Bagoua the NM treatment had 506 kg ha-1 vs. 1152 kg ha-1 in the C0 treatment. Residual effects of manure led to grain yields in the C1 and C2 treatments which were more than twice as high as in the NM treatment. The improved cultivars were generally superior for grain yields, whereas the local landrace was superior for straw yields at both sites. Root zone drainage was decreased by between 50 to 100 mm, and water use increased by the same amount in the current corrals at the two sites during the two growing seasons. Increased water use under corralling and presence of residual profile moisture at the end of each of the two seasons suggested that water did not limit pearl millet production at the two sites.
39

Estimation of global radon exhalation rate distribution

Goto, Masayoshi, Moriizumi, Jun, Yamazawa, Hiromi, lida, Takao, Zhuo, Weihai 08 1900 (has links)
No description available.
40

Batch and Column Transport Studies of Environmental Fate of 3-nitro-1,2,4-triazol-5-one (NTO) in Soils

Mark, Noah William January 2014 (has links)
NTO (3-nitro-1,2,4-triazol-5-one) is one of the new explosive compounds used in insensitive munitions (IM) and developed to replace traditional explosives, TNT and RDX. Data on NTO fate and transport is needed to determine its environmental behavior and potential for groundwater contamination. In this study, we measured how NTO in solution interacts with different types of soils and related soil properties to transport and fate behavior. We conducted a series of kinetic and equilibrium batch soil sorption experiments and saturated column transport studies under steady-state and transient conditions. NTO adsorbed very weakly to the studied soils. Adsorption coefficients (Kds) measured for NTO in a range of soils in batch experiments were less than 1 cm³ g⁻¹. There was a highly significant negative relationship between measured NTO adsorption coefficients and soil pH (P = 0.00011). In kinetic experiments, first order transformation rate estimates ranged between 0.0004 h⁻¹ and 0.0221 h⁻¹. There was a general agreement between batch and column-determined fate and transport parameters. However, transport studies showed an increase in the NTO transformation rate as a function of time, possibly indicating microbial growth.

Page generated in 0.0733 seconds