Phosphorus (P) limitations to agricultural productivity commonly occur in Australian soils and have largely been overcome by the use of inorganic fertilisers. However, studies have shown that most of the P taken up by plants is from native P pools. The turnover of P and native soil organic matter may be strongly affected by drying and rewetting (DRW). Rewetting dry soil results in a pulse of respiration activity and available nutrients. In Mediterranean-type climates surface soils naturally undergo recurrent DRW cycles. In southern Australia, soils experience DRW due to erratic rainfall within the growing season, and short, high intensity thunderstorms also during summer periods. The principal objective of this thesis was to determine the significance of dry-rewet events, for altering P availability and cycling in agricultural soils in Australia. Soils representing a wide range of soil types and climatic zones of southern Australia, showed large flushes in carbon (C) mineralisation after a single DRW event. For some soils these were comparable with reported values, however large variability in flush size between soils was observed. Soils that commonly experience DRW did not appear to be more resilient to DRW than soils from areas with fewer DRW events. Even when soils had relatively small respiration flushes, as a result of low soil organic matter, a high proportion of the soil C was mineralised after rewetting. Soil physiochemical properties (total C, total N, organic C, humus, microbial biomass P, organic P, sand and silt) were correlated to the size of the flush, hence nutrient availability and soil texture appear to primarily determine flush size. Therefore, the influence of climate on DRW may relate to determining the quantity of organic matter and microbial biomass that is available for turnover. Different size and composition of the microbial biomass within the same soil matrix were achieved by adding three different C substrates (glucose, starch and cellulose at 2.5 g kg-¹) at 5 times over 25 weeks. The treatments showed disparate responses to DRW, due to greater biomass (larger flushes) and effects of community composition, highlighting the central role of the soil microbes in DRW processes. When subjected to multiple DRW events these soils showed smaller rewetting respiration flushes with subsequent rewetting events. In contrast, the amount of P released after rewetting was the same. This study showed that increases in P after rewetting were transient and rapid immobilisation of P by microbes occurred, which may limit the availability to plants. The composition of the microbial community was changed by DRW with a reduction in fungi and gram negative bacteria, showing that certain species are more susceptible to DRW than others. Closer investigation at 2 hourly intervals after rewetting confirmed the transient nature of P flushes. The response in microbial respiration after rewetting was immediate, with the highest activity occurring within the first 2 h. Phosphorus availability was increased by DRW but remained stable over the following 48 h incubation period. The study highlights the rapid nature of changes in available nutrients after rewetting. Furthermore, while potentially only a small component of the P flush that occurred, the DRW soil had higher levels of P than most incubated soil at 48 h, this would be potentially available for plant uptake or movement with the soil solution. Long-term water regimes (continuously moist or air-dry, or DRW occurring at different times during incubation) that were imposed on two soils from different climatic regions over a 14 wk period, did not alter available nutrient (P and C) pools or the size of the microbial biomass. However, these long-term water regimes determined the respiration response of the soils to experimental DRW. The largest flushes occurred in the treatment with the longest dry period, and confirm findings of reported studies that the response of a soil at rewetting is determined by the length of the period that it is dried. Microbial biomass was little affected by experimental DRW, but showed large changes in C:P ratio. Thus, changes in physiological state or community composition may be more affected by DRW than the size of the microbial biomass. Microbial communities were altered by DRW irrespective of climatic history (warm wet summer and temperate Mediterranean), however these changes were not related to specific groups of organisms. In addition, the disparate respiration responses and inhibition of phosphatase by DRW, indicate that functional changes may be induced by DRW but can not be sufficiently explained by quantifying available nutrient pools or the microbial biomass. The use of wheat seedlings bio-indicators of P availability after the long-term water regimes, confirmed that plant available P was altered by DRW, indicated by differences in growth, although the large variability in seedling growth made it difficult to quantify these differences. However, the distribution of labile P, available at planting, in soil and plant pools at harvest, showed that long-term water regimes increased P allocation in plant tissue in one soil and decreased it in another. Furthermore, only a small fraction of the labile P present at planting was taken up by plants, which confirms the superior ability of soil microbes to immobilise P that is released by DRW. Nevertheless, since the long-term water regimes increased P availability, this may be transported via surface water or leaching. DRW is important for C and P turnover in soils of southern Australia. However, P flushes occur rapidly after rewetting and are transient. Therefore, DRW appears to have only minor consequences for P availability to plants. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1321018 / Thesis (Ph.D.) -- University of Adelaide, School of Earth and Environmental Sciences, 2008

This master thesis provides an overview of the paper machine with focus on the forming section. The forming section is the first part in the paper machine where the paper pulp is injected through a head box. The paper pulp contains about 99.5% of water and 0.5% fiber. The water as content is reduced by vacuum and gravity. The problem to be studied in this project is related to external rewetting. This is water going back to the paper web from the forming fabric after the dewatering zone. The dewatering is based on vacuum slots under the forming fabric. The vacuum slots absorb water from the soaked paper pulp through the forming fabric. External rewetting causes problem, hence the paper will have a higher dry content when leaving the forming section. The paper should have as low dry content as possible in the end of the forming section. Three different forming fabrics from Albany International were chosen for the project. The structures of the forming fabrics were two different double layers and one plain weave. The performance of the fabrics was studied by 4 different methods. The methods used were 2 different wicking tests, a vacuum dewatering trial and one foulard test. Also micro tomography was done to understand the structure of each design. The main test was a foulard test where the aim was to see in what way the rewetting got affected by different pores sizes. The results showed higher water content for the paper that was on top of the forming fabric with the larger pores.

<p>Rich fens are an important, but threatened, habitat type in the boreal landscape. In this thesis I have examined responses of rich fen vascular plants and bryophytes after drainage and restoration. </p><p>The effects of drainage on the rich fen flora were observed in a long time study and the responses were rapid and drastic. During an initial stage a rapid loss of brown mosses was observed, followed by increases of sedges and early successional bryophytes, and later by an expansion of dominants. Initial effects of hydrological restoration showed that rewetting can promote re-establishment of an ecologically functional rich fen flora, but has to be combined with other treatments, such as mowing or surface disturbance. </p><p>After restoration, re-establishment of locally extinct species may be hampered by dispersal limitations. To test if reintroductions could help to overcome dispersal limitations I performed transplantation studies with four common rich fens bryophytes to a rewetted site. The results showed that the species were able to establish, and that survival and growth were promoted by desiccation protection and liming. </p><p>I further examined competition among three of the most common bryophytes in natural boreal rich fens that usually occur mixed in a mosaic pattern but show small but important microtopographical niche separation. The results indicate similar competitive abilities among the species, and no case of competitative exclusion occurred. The results help to explain the coexistence of these species under natural conditions with microtopographic variation and repeated small scale natural disturbances. </p><p>Restoring a functional flora in drained rich fens is a complex task, which requires understanding of underlying causes of substrate degradation in combination with suitable restoration measures. The thesis suggests how the results can be used in practical restoration work, and also stresses the need for monitoring of restoration experiments over longer time. </p>

Os óleos vegetais vêm sendo estudados como substitutos aos minerais em várias aplicações industriais, em particular no resfriamento de aços, no processo de tratamento térmico de têmpera. Este trabalho trata do estudo das características de viscosidade e propriedades de resfriamento de óleos vegetais e de formulações feitas a partir desses óleos com diésteres: Bis (2-etilhexil) adipato DOA, Bis (2-etilhexil) sebacato DOS e Diiso Tridecil adipato DITA, nas proporções de 2,5% e 5,0% (m/m). Realizou-se também nos óleos vegetais, sem aditivos, uma avaliação prévia da estabilidade oxidativa feita por RMN, baseando-se nas proporções de ácidos graxos saturados e insaturados presentes na cadeia. Avaliações foram também feitas para formulações com óleo de soja após o processo de envelhecimento acelerado. Os resultados indicaram como sendo o óleo de coco, o de maior estabilidade oxidativa. Os óleos de amendoim e soja apresentaram menores variações de viscosidade com a temperatura, caracterizados pelos menores valores do coeficiente de Walther (B). Das formulações estudadas, no estado não oxidado, a adição de 2,5% de DOS ao óleo de soja foi a que proporcionou maiores taxas máximas e camada de vapor menos estável. Após a oxidação de 48 horas, a composição de óleo de soja adicionado a 5,0% de DOA foi a que sofreu menores alterações comparadas do estado não oxidado. / Vegetable oils have been studied in the replacement of mineral oils in many industrial applications particularly on the quenching steel in the heat treatment process. This work presents studies conducted to vegetable oils in terms of viscosity characteristics and cooling behavior. Such studies incorporate also formulations on vegetable oil based by diesters additions [Bis (2-etylhexyl) Adipate - DOA, Bis (2-etylhexyl) Sebacate DOS, Diiso Trydecil Adipate DITA] in the proportions of 2.5 and 5.0 % (m/m). Oxidation stability was evaluated by NMR performed in the vegetable oil without diesters additions. This evaluation was based in the satured and insatured compounds presented in the vegetable oil chain. Similar evaluations were also performed for formulations based on the soybean oil, before and after the accelerated oxidation tests. Results indicated coconut oil as the most stable in terms of oxidation. Peanut oil and soybean oil shown minor alterations on the viscosity values when the raise of temperature, since they presented lower Walther coefficient (B). Comparing the formulations soybean oil based in the not oxidized condition, the addition of 2,5% DOS was that shown greater maximum cooling rates (CRmax) and less stable vapour phase. After accelerated oxidation tests (48 hours), formulation with 5% DOA (soybean oil based) was that presented minor variations in terms of cooling parameters compared with not oxidized condition.

Evaporation, wetting and multiphase flows of drops and bubbles are everyday life phenomena with potential impact in many industrial, biological, medical or engineering applications. The understanding and controlling of the physical and chemical mechanisms governing these phenomena have become of paramount importance. This thesis encompasses three topics: evaporation of sessile droplets of polymer solutions, the role of thermocapillarity on self-rewetting fluid dynamics and migration of bubbles in liquid flows. Firstly, the evaporative behaviour of sessile droplets of aqueous polymer solutions and the effect of different molecular weights on the drying process has been studied. Drop shape analysis allowed monitoring the evolution of all stages during drying and indicating the transitions between stages. The mechanisms taking place during the crucial stages of pinning and depinning were illustrated, revealing the effects of adhesion and contact line friction forces on the final morphology of the dried polymeric deposits. Additionally, the effect of varying substrates from hydrophilic to hydrophobic was examined demonstrating the importance of interfacial interaction phenomena. The initial spreading dynamics of binary alcohol mixtures (and pure liquids) deposited on different substrates in partially wetting situations, under non-isothermal conditions was systematically investigated. Moreover, the temporal and spatial thermal dynamics within pure droplets and alcohol mixtures using IR thermography revealed the existence of characteristic thermal patterns due to thermal and/or solutal instabilities. The contribution of the Marangoni effect as an important heat transport mechanism within the evaporating droplets was investigated. The motion of buoyancy-driven bubbles in a vertical microchannel and the significant role of thermocapillarity was reported in this series of experiments. The behaviour of the bubbles in self-rewetting fluid flows departed considerably from that of pure liquids flows. Furthermore, heat transfer coefficient calculations in the single and two phase flows demonstrated that the presence of Marangoni (surface tension) stresses resulted in the enhancement of the heat transfer distribution in the self-rewetting fluid flows compared with the pure ones.

Rich fens are an important, but threatened, habitat type in the boreal landscape. In this thesis I have examined responses of rich fen vascular plants and bryophytes after drainage and restoration. The effects of drainage on the rich fen flora were observed in a long time study and the responses were rapid and drastic. During an initial stage a rapid loss of brown mosses was observed, followed by increases of sedges and early successional bryophytes, and later by an expansion of dominants. Initial effects of hydrological restoration showed that rewetting can promote re-establishment of an ecologically functional rich fen flora, but has to be combined with other treatments, such as mowing or surface disturbance. After restoration, re-establishment of locally extinct species may be hampered by dispersal limitations. To test if reintroductions could help to overcome dispersal limitations I performed transplantation studies with four common rich fens bryophytes to a rewetted site. The results showed that the species were able to establish, and that survival and growth were promoted by desiccation protection and liming. I further examined competition among three of the most common bryophytes in natural boreal rich fens that usually occur mixed in a mosaic pattern but show small but important microtopographical niche separation. The results indicate similar competitive abilities among the species, and no case of competitative exclusion occurred. The results help to explain the coexistence of these species under natural conditions with microtopographic variation and repeated small scale natural disturbances. Restoring a functional flora in drained rich fens is a complex task, which requires understanding of underlying causes of substrate degradation in combination with suitable restoration measures. The thesis suggests how the results can be used in practical restoration work, and also stresses the need for monitoring of restoration experiments over longer time.

In previous studies on suction box dewatering, three mechanisms were identified that determine the dry content of a web, viz. web compression, displacement of water by air and rewetting. In the present work, the relative importance of the three mechanisms was investigated through direct measurement of the web deformation, the dry content changes during and after the suction pulse, the air flow through the fibre network and the saturation of the web after the suction pulse. Suction pressure, suction time and rewetting time were varied. The experiments were done with chemical and mechanical pulp webs of various grammages. It was found that a large web deformation took place during the suction pulse, particularly at its beginning. Compression dewatering was found to be the most dominant dewatering mechanism. Displacement dewatering started after most of the web compression had occurred. Its contribution to the increase in dry content was most pronounced for higher suction pressures, longer suction times and for chemical pulp webs. A surprisingly large expansion of the web was observed immediately after the suction pulse. This expansion was the effect of rewetting. This rewetting strongly reduced the dry content of the web if the web had not been immediately separated from the forming fabric at the end of the suction pulse. Under the conditions studied, the decrease in dry content amounted to the order of 3 to 6 %. Rewetting was smaller for longer suction times and higher suction pressures. A considerable air flow through the web occurred under these conditions. This air flow apparently moved water from the forming fabric into the suction box, thus making less water available for rewetting. Rewetting for mechanical pulp webs was more pronounced and took place faster than for chemical pulps. The use of a membrane on top of the web during suction box dewatering proved to be advantageous for reducing the air flow through the web. However, under the conditions investigated, the dry content could not be improved. Although the web compression was increased when using a membrane, especially at a higher suction pressure, rewetting after the suction pulse had an even larger negative impact on the dry content, which, as a result, was lower. / QC 20100924

Os óleos vegetais vêm sendo estudados como substitutos aos minerais em várias aplicações industriais, em particular no resfriamento de aços, no processo de tratamento térmico de têmpera. Este trabalho trata do estudo das características de viscosidade e propriedades de resfriamento de óleos vegetais e de formulações feitas a partir desses óleos com diésteres: Bis (2-etilhexil) adipato DOA, Bis (2-etilhexil) sebacato DOS e Diiso Tridecil adipato DITA, nas proporções de 2,5% e 5,0% (m/m). Realizou-se também nos óleos vegetais, sem aditivos, uma avaliação prévia da estabilidade oxidativa feita por RMN, baseando-se nas proporções de ácidos graxos saturados e insaturados presentes na cadeia. Avaliações foram também feitas para formulações com óleo de soja após o processo de envelhecimento acelerado. Os resultados indicaram como sendo o óleo de coco, o de maior estabilidade oxidativa. Os óleos de amendoim e soja apresentaram menores variações de viscosidade com a temperatura, caracterizados pelos menores valores do coeficiente de Walther (B). Das formulações estudadas, no estado não oxidado, a adição de 2,5% de DOS ao óleo de soja foi a que proporcionou maiores taxas máximas e camada de vapor menos estável. Após a oxidação de 48 horas, a composição de óleo de soja adicionado a 5,0% de DOA foi a que sofreu menores alterações comparadas do estado não oxidado. / Vegetable oils have been studied in the replacement of mineral oils in many industrial applications particularly on the quenching steel in the heat treatment process. This work presents studies conducted to vegetable oils in terms of viscosity characteristics and cooling behavior. Such studies incorporate also formulations on vegetable oil based by diesters additions [Bis (2-etylhexyl) Adipate - DOA, Bis (2-etylhexyl) Sebacate DOS, Diiso Trydecil Adipate DITA] in the proportions of 2.5 and 5.0 % (m/m). Oxidation stability was evaluated by NMR performed in the vegetable oil without diesters additions. This evaluation was based in the satured and insatured compounds presented in the vegetable oil chain. Similar evaluations were also performed for formulations based on the soybean oil, before and after the accelerated oxidation tests. Results indicated coconut oil as the most stable in terms of oxidation. Peanut oil and soybean oil shown minor alterations on the viscosity values when the raise of temperature, since they presented lower Walther coefficient (B). Comparing the formulations soybean oil based in the not oxidized condition, the addition of 2,5% DOS was that shown greater maximum cooling rates (CRmax) and less stable vapour phase. After accelerated oxidation tests (48 hours), formulation with 5% DOA (soybean oil based) was that presented minor variations in terms of cooling parameters compared with not oxidized condition.

Historically, approximately 25% of Sweden's wetlands have been ditched and drained in favour of agriculture, forestry, infrastructure and peat extraction. Major investments have been made in recent years to recreate the natural and environmental benefits that have been lost. Among other things, this has given rise to Falkenberg municipality's plans to apply for funding to rewet Hakamosse. The purpose of the study is to provide Falkenberg municipality with data through analysis of the current situation regarding water chemical parameters and give suggestions on sampling points and suitable parameters to monitor for Hakamosse. The study is limited to hydrology, water chemistry and greenhouse gases. The water chemistry study was performed by sampling and analysis from three sampling points on five occasions. Scientific information and knowledge gained from other rewetting projects has been collected from scientific literature, reports and semi-structured interviews. The chemical water analysis results show variations between the sampling points and the sampling occasions but with few deviating values. The control program's water chemical monitoring should build on the current situation analysis in this study. Based on the literature study, hydrological measurements should include measurements of groundwater levels and water flow. Greenhouse gas emissions can be measured with instruments or calculated using the IPCC's emission factors. A limiting factor in the implementation of monitoring programs is often the availability of time and financial resources, which often leads to a balance between sampling frequency and the number of sampling points depending on the parameter and method. The results also highlight that a risk analysis is needed as the rewetting of Hakamosse may have a major impact on the surrounding environment. / Historiskt har cirka 25% av Sveriges våtmarker dikats och torrlagts till förmån för jordbruk, skogsbruk, infrastruktur och torvtäkter. Stora satsningar har på senare år gjorts för att återskapa de natur- och miljönyttor som gått förlorade. Det har bland annat har gett upphov till Falkenberg kommuns planer på ansökan om bidrag till att återväta Hakamosse. Syftet med studien är att förse Falkenbergs kommun med underlag genom nulägesanalys av vattenkemiska parametrar samt underlag till ett kontrollprogram för Hakamosse. Kontrollprogrammet är avgränsat till hydrologi, vattenkemi och växthusgaser. Den kvantitativa vattenkemiska undersökningen utfördes genom provtagning och analys från tre provtagningspunkter under fem tillfällen. Underlag till utformning av kontrollprogram har insamlats från vetenskaplig litteratur, rapporter och semistrukturerade intervjuer. Det vattenkemiska analysresultatet visar variationer mellan provtagningspunkterna och provtagningstillfällena men med få avvikande värden. Kontrollprogrammets vattenkemiska övervakning bör bygga vidare på nulägesanalysen i denna studie. Baserat på litteraturstudien ska hydrologiska mätningar inkludera mätningar av grundvattennivåer samt vattenflöde. Växthusgasgasavgången kan förslagsvis mätas med provtagningsinstrument eller beräknas med hjälp av IPCC:s emissionsfaktorer. En begränsande faktor vid utformningen av kontrollprogram är ofta tillgången till tidsmässiga och ekonomiska resurser, vilket ofta leder till avvägning mellan provtagningsfrekvens och antalet provtagningspunkter beroende på parameter och metod. Resultatet belyser även att en riskanalys behövs då en återvätning av Hakamosse kan ha en stor påverkan på omgivningen.

Many researchers have reported differences in soil C and N dynamics between soils of different textures and/or soil organic matter contents. However, it has proven difficult to determine the exact relationships and mechanisms between C and N dynamics and soil texture/SOM. There are few studies that consider how these soil physical and chemical conditions influence the effects of drying and rewetting on the mineralisation of C and N and the microbial transformations that follow. The objectives of this study were: 1) To determine the effects of repeated drying and rewetting cycles on C and N dynamics in soils of differing textural class and organic matter levels. 2) To use C & N mineralised at constant moisture contents to calculate mineralisation during dry/wet cycles for comparison with actual mineralisation. Two soil types with contrasting textures were chosen and 6 paddocks on each soil type were selected to produce an OM gradient for each soil. Three moisture treatments were chosen to simulate moist (field capacity at -0.01 MPa), moderately dry (120% of wilting point at -1.5 MPa) and very dry (80% of wilting point at - 1.5 MPa) field conditions. The dry moisture treatments were then combined with a rewet treatment where they were either rewet or maintained dry (+ or – rewet), resulting in a total of five dry/rewet treatments. Soils were packed into funnel tops to a BD of 1.1 g/cm³ and sealed in glass jars fitted with septa to allow gas sampling. Drying was achieved using silica gel which allowed continued gas measurement during drying periods. Gas samples were collected throughout the experiment and analysed for CO₂ by IRGA and N₂O by GC. At the start and end of the study, soils were analysed for Min N, MBC, MBN, HWC, DOC, POM, total C and total N. The correlation between calculated and actual C mineralisation data indicates that the intercept is not consistent with the origin and that the slope is not consistent with the 1:1 line. While those paddocks with high %C had high cumulative C mineralisation, there didn’t appear to be any strong relationship between soil texture or OM content and the difference between actual and calculated C mineralisation. A plot of calculated C mineralisation rates against the actual C mineralisation rates shows that much of the error in the calculated cumulative data arises from an underestimation of the mineralisation flush when the dry soil is rewetted, especially during the first dry-rewet cycle, and an over estimation of the rate at which respiration decreases as the soil dries. In order to use C mineralisation data from soils held at constant moisture contents to accurately predict C mineralisation in soils exposed to dry-rewet cycles, knowledge of the stress history for the soil would be required e.g. size, duration and frequency of rainfall events, dry rates etc. The N₂O-N emission data is inherently more variable than the C mineralisation data. The fine-textured soils tend to have much higher N₂O-N emissions than the coarser soils, probably due to the creation of anoxic sites upon rewetting in the fine-textured soils. The data indicates that prediction of N₂O-N emissions in soils exposed to dry-rewet cycles using emission data from soils held at constant moisture contents would be very inaccurate, primarily due to the inherent variability of N₂O-N emissions in soils.