The main purpose of the AOD-converter is to lower the carbon content in stainless steel production. The carbon content can be estimated by static theoretical models. It can also be estimated through dynamic models based on analysis of the exhaust gases from the converter. This master thesis is a study on an extended use of exhaust gas analysis data on the AOD-converter at Outokumpu’s stainless steel plant in Avesta, Sweden. There are two main methods of predicting the carbon content based on exhaust gas analysis, mass balance and a linear regression between decarburization rate and carbon content. This master thesis mainly focuses on the development of the linear regression model for steel grades ASTM 304L, 316L, S32101 and S32205 for the last step of the decarburization, as well as ASTM S32205 and S30815 for the second last step of the decarburization. The results showed that the linear regression model can predict the carbon content at the last step of decarburization with a standard deviation between 0,00626 %C and 0,0109 %C for the different steel grades. An equation for carbon prediction dependent on the steel composition was also developed in the master thesis, making it theoretically possible to use for all steel grades, it has however not yet been tested on other steel grades. The CRE measured from the exhaust gases was also studied to find out if it is possibleto use as basis for step changes during the decarburization, but the resultswere inconclusive. / Huvudsyftet med AOD-konvertern är att sänka kolhalten i produktionen av rostfritt stål. Kolhalten kan uppskattas av statiska teoretiska modeller. Den kan också uppskattas av dynamiska modeller baserade på analys av avgaserna från konvertern. Det här examensarbetet handlar om utvidgning av användandet av avgasanalysdata på AOD-konvertern på Outokumpus stålverk i Avesta, Sverige. Det finns i huvudsak två metoder för att bestämma kolhalten med hjälp av avgasanalys, massbalans och en linjär regression mellan kolfärskningshastigheten och kolhalten. Det här examensarbetet fokuserar i huvudsak på utvecklingen av den linjära modellen för stålsorterna ASTM 304L, 316L, S32101 och S32205 för sista steget i kolfärskningen. Samt stålsorterna ASTM S32205 och S30815 för näst sista steget i kolfärskningen. Resultaten visade att den linjära modellen kunde uppskatta kolhalten i sista steget av kolfärskningen med en standardavvikelse mellan 0,00626 %C och 0,0109 %C för de fyra olika stålsorterna. En ekvation som anger sambandet mellan sammansättningen på stålet under kolfärskningen och ekvationen för den linjära regressionen togs också fram i examensarbetet. Teoretiskt kan ekvationen användas för alla stålsorter men den har inte än blivit testad på andra stålsorter. CRE uppmätt med hjälp av avgasanalys undersöktes också för att ta reda på om CRE kan användas för att bestämma när stegbytena ska ske, det gick dock inte att utgöra från resultaten.

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Successful renovation of wastewater and sludge via land application depends upon sludge-induced soil changes associated with carbon (C) and nitrogen (N) cycles within the soil/plant system. The C, N, and hydrologic cycles within a soil/sludge system receiving a year-round, daily application of paper mill sludge were studied. Soil samples were collected from three locations on a land application site in the Piedmont of Virginia that had received papermill sludge applications for six, two, and no prior years. The average application rate was 4.4 cm/wk, each week of the year, with a N loading of 700 kg N ha⁻¹yr-⁻¹. The column study showed that C and N were still accumulating on the land application site after 6 years, but at a decreasing rate. Based on this study, C accumulation will level out after 13 years of application, but N will continue to accumulate for almost 30 years. As application period increased, soil bulk density increased in the O, A, and B horizons, the percentage of non-capillary porosity fell below 10% in the A horizon and approached zero in the B horizon, and there was a dramatic decrease in the soil's hydraulic conductivity in both the A and B horizons. Nitrogen leaching is expected to increase with time due to high amounts of N in the papermill sludge, a continued narrowing of the C:N ratio, a high percentage of nitrification, and low denitrification rates. Experimental timing and rates of sludge additions were imposed to alter the aerobic/anaerobic properties of the soil system to determine the conditions under which optimum C and N mineralization, nitrification, and denitrification would occur. Application rates were factorially arranged for single or multiple doses on a daily or alternating schedule. The C decomposition and N mineralization processes were both optimized with an increase in the length of cycle; they were maximized with an alternating 9 days on/9 off application schedule. The nitrification potential also increased with the length of cycling, with an average nitrification rate of 96%. Denitrification was minimal in all treatments, with an average denitrification rate of 16%. This was primarily attributed to movement of nitrate-N below the most biologically active zone in the soil column. Sludge renovation will ultimately depend upon the excess N being sequestered in plant biomass or denitrified. Proper management of these processes will ensure that wastes decompose, and that N is stored or evolved as a benign gas rather than leached at unacceptable levels. / Master of Science

Thesis (MPhil (Sustainable Development, Planning and Management))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Sustainable agricultural management practices have a profound impact on soil carbon sequestration. The amount of carbon that can be stored in a given soil is influenced by climate, soil type, and the quality and quantity of organic inputs. Together, the interactive effect of these factors determines the Soil Organic Content (SOC). Sustainable agricultural management practices influencing Soil Organic Matter (SOM) include application of organic amendments, conservation tillage, and use of cover crops, crop rotations, crop residue management, and nutrient management. Increasing SOC enhances soil quality, reduces soil erosion, and increases agricultural productivity with considerable on-farm and off-farm benefits. To assess how management practices affect SOC, two case studies were conducted in Yavatmal district of Maharashtra in India and Lynedoch near Stellenbosch. The first case study examined the differences in SOC content on four farms each managed with 13 different sustainable agricultural techniques and one farm managed under conventional management practices. The second case study investigated the SOC differences between an organic and a conventional vegetable farm. The results of both studies show that farms that are managed under sustainable agricultural practices generally contain higher SOC content than farms that are managed under conventional agricultural practices. / AFRIKAANSE OPSOMMING: Om te bepaal hoe bestuurspraktyke Grondlikke Organise Koolstoff raak, is twee gevallestudies in die distrikte Yavatmal in Maharashtra, Indië, en Lynedoch buite Stellenbosch uitgevoer. Die eerste gevallestudie het die verskille in Grondlikke Organise Koolstoff -inhoud bekyk op vier plase waar 13 verskillende Volhoubare landboubestuurspraktyke het ‟n diepgaande impak op grondkoolstof-beslaglegging. Die hoeveelheid koolstof wat binne gegewe grond gestoor kan word, word deur klimaat, grondsoort en die gehalte en hoeveelheid organiese toevoer beïnvloed. Saam bepaal die interaktiewe effek van vermelde faktore die Grondlikke Organise Koolstoff -inhoud. Volhoubare landboubestuurspraktyke wat Grondlikke Organise Materiaal beïnvloed, sluit in die toediening van organiese verbeterings, bewaringsgrondbewerking, die gebruik van dekkingsoeste, oesrotasies, die hantering van oesresidu en voedingstofbestuur. Vermeerdering van Grondlikke Organise Koolstoff verhoog grondgehalte, verminder gronderosie en vermeerder landbouproduktiwiteit met aansienlike voordele op en verwyderd van die plaas. volhoubare landboutegnieke in die bestuurproses toegepas word, en een plaas wat volgens konvensionele bestuurspraktyke bedryf word. Met die tweede gevallestudie is ondersoek gedoen na die Grondlikke Organise Koolstoff -verskille tussen ‟n organiese en ‟n konvensionele groenteplaas. Die uitslae van albei studies dui daarop dat plase wat volgens volhoubare landboupraktyke bestuur word oor die algemeen hoër Grondlikke Organise Koolstoff-inhoud aantoon in vergelyking met plase wat volgens konvensionele landboupraktyke bedryf word.

In an interdisciplinary study requiring the synergistic association of historical evidence and chemical and biochemical analyses, this thesis investigates the properties and characteristics of historically modified soils known as anthrosols. These soils, developed through the anthropogenic addition of high volumes of organic-rich municipal waste materials to land, including human and animal waste, as part of the waste management practices in medieval urban communities in Scotland at St Andrews, Roxburgh and Elgin, offer an insight to the state and dynamics of these organic material. Soil is one of the most sensitive environmental domains to transformation. These transformations are visible from the alterations to the physical and chemical properties of soil. Anthropogenic activities may leave behind signatures in the soil in the form of artefacts, ecofacts, elemental enrichment or depletion, enhancement in soil magnetic properties and organic matter content. In the historical dimension of this study, the observable features and measurable properties of soil profiles are exploited to reveal past organisation and functions of cultural landscapes by carefully studying the stratigraphic units of soil profile, and examining the association of each unit with settlement artefacts and soil properties. Through comparison with historical records of past events on the respective study sites, the relationship between the soils record of past human activities is observed through physical, chemical and biochemical properties. The historical record is used to assess if such evidence can be used reliably to develop the account of site use for the medieval burghs of Scotland. In the environmental aspect, investigation focuses on the physical and chemical conditions of these soils in terms of their carbon content, composition, residence time estimates and their role in global C cycle and terrestrial carbon budgeting. Past investigations of anthopogenically-deepened soils have been interpreted with respect to historical site use, however, the environmental implications of the resultant accumulated organic material or residue have not previously been considered in much detail. A particular novelty of this aspect of the project is that it is an in-depth examination of anthropogenic soils with known histories extending into the medieval period. This time-depth allows a new understanding of the processes and products of decomposition of known organic materials that were added to soil. The biophysicochemical data obtained from these soils such as their extant organic carbon content and variability with depth, the composition of the various carbon species that together constitute soil organic matter, and biological community and activity (microorganisms and enzymes) provides critical information on the relative recalcitrance, state of decomposition, and the mechanism of stabilisation of these materials in the soil.

Marine microorganisms play a significant role in the cycling of nutrients in the open ocean through production, consumption, and degradation of organic matter (OM). Carbon (C), nitrogen (N), and phosphorus (P) are essential ingredients in every known recipe for life. However, the cycling of each of these elements proceeds at different rates such that the ratio of C:N:P can vary widely between particulate, dissolved, organic, and inorganic pools. To better understand the mechanisms controlling these transformations, this study investigated the bacterial remineralization of photosynthetically-derived organic matter derived from cultures of Trichodesmium IMS101, Thalassiosira weissflogii, Prochlorococcus MED4, and particulate material collected from the surface waters of an upwelling regime. Experiments were conducted at sea for a short duration (<6d) and in the laboratory for longer periods (<150 days). In all treatments, across experiments, we observed rapid and selective P remineralization independent of the type of organic material added. Full solubilization and remineralization of P typically occurred within a week. Conversely, N remineralization was slower, with only 39-45% of particulate N (PN) remineralized in shorter (6d) experiments and 55-75% of PN remineralized in <150d experiments. Nitrification was observed after 70-98 days depending on the remineralizing bacteria (isolated from either the Oregon coastal upwelling regime or the North Pacific Subtropical Gyre (NPSG). Notably, these events did not transform the full complement of ammonium to nitrate. This differential lability between N and P led to rapid changes in the N:P ratio of inorganic pools as organic matter was depolymerized by varying bacterial populations. The variable input of potentially limiting elements could have consequences for primary productivity and particle export. Finally, we observed that in short-term experiments with heterotrophic bacteria collected from the NPSG, the N:P ratio of remineralization (11 ± 2.2) was independent of the N:P of added organic material (5-23). This uniformity of inorganic ratios implies differential lability and N:P composition of residual semi-labile and refractory organic matter. Formation of refractory C and N rich organic matter, often termed the microbial pump, is a significant pathway for the transport and sequestration of elements in the aphotic zone of the ocean interior. The experimental results reported here suggest that differential supply of POM leads to rapid and preferential P remineralization, N:P remineralization independent of the N:P of added substrates, and variable N:P of residual organic matter. These findings help constrain our knowledge of elemental cycling in the marine environment. / Graduation date: 2013

A two year study was initiated in 1999 at the Macdonald Campus Farm, on a 2.4 ha site consisting mainly of St-Amable sand to shallow loamy sand (Typic Endoaquent; Humic Gleysol). The site was planted to alfalfa ( Medicago sativa) prior to the establishment of the experimental design and has been planted to corn (Zea mays L.) since 1991. The experiment was set up as a randomized complete block design and consisted of three tillage levels (NT, no-till; RT, reduced tillage; and CT, conventional tillage) and two residue levels (-R, no residues; +R, with residues). This study was performed in order to ascertain the effect of these management systems on soil organic carbon (SOC), particulate organic matter carbon (POM-C), microbial biomass carbon (MBC) levels and soil physical properties. Soil physical properties measured included bulk density, saturated hydraulic conductivity (Ksat), dry and wet aggregate stability, total porosity, macroporosity at -1 kPa and -6 kPa of matric potential, and moisture content. Crop yield was also measured. Results indicated that lower rates of mineralization of POM-C under NT+R in the surface 0--10 cm led to significantly higher SOC at the same depth. There were no significant differences between treatments at the 10--20 cm depth. The MBC was not a good indicator of the differences in soil organic matter levels between treatments. No-till treatments had higher bulk densities, reduced total porosity and macroporosity, increased moisture content, and increased constant-head measured Ksat. Differences in Ksat as measured with the Guelph permeameter, were not significant between treatments, most likely due to increased earthworm activity in NT. There were no significant differences in crop yield in 1999, but a significantly wetter year in 2000 caused lower grain yields in NT+R compared to NT-R and CT+R.

CH$ sb4$ and CO$ sb2$ fluxes were measured in upland boreal forest soils, over the period May 16$ sp{ rm th}$ through Sept. 16$ sp{ rm th}$, 1994, among a variety of vegetation and drainage characteristics. Most upland soils consumed CH$ sb4$, (0.6 to $-$2.6 mg CH$ sb4$ m$ sp{-2}$ d$ sp{-1}$), and produced CO$ sb2$, (0.2 to 26.8 g CO$ sb2$ m$ sp{-2}$ d$ sp{-1}$). CH$ sb4$ consumption showed no seasonal trend, however CO$ sb2$ flux displayed an increasing rate until late August, after which flux rates began to decrease. Differences among the sites examined showed soil temperature and organic matter content to be the primary controls in predicting seasonal mean CH$ sb4$ flux rates. Similarly for CO$ sb2$ flux, soil temperature and C content proved to be the best predictors of seasonal mean differences among the range of sites examined. / Sites could be divided into 2 categories, strong CH$ sb4$ consuming and CO$ sb2$ producing sites, Gillam Aspen, Gillam Pine, OBS Aspen, Burn Moss, Palsa Birch, and YJP Dry and weak CH$ sb4$ consuming and CO$ sb2$ producing sites, Gillam Spruce, OBS Spruce, YJP Wet, Burn Spruce and Palsa Moss. The strong flux sites all exhibited similar trends in soil characteristics as they were the warmest, driest sites with faster nutrient cycling processes and thin ($ sim$2 to 10 cm) organic layers. The weak flux sites were colder, wetter, with slower nutrient cycling, and a thick organic/peat layer ($ sim$20 to 50 cm). The primary visual distinction between these two groups was the presence of a Sphagnum sp. ground cover, which was characteristic of weak CH$ sb4$ consuming and CO$ sb2$ producing sites.

In 1996, four cores (&sim;30 cm depth) were extracted from the high marsh zone of Dipper Harbour salt marsh in the Bay of Fundy. Soil bulk densities are shown to be controlled by mineral density and are higher than those reported for salt marshes in the northeastern United States. Examination of variations in mineral content suggests that regular tidal action and ice rafting deposits the majority of the mineral sediment to the high marsh zone. Dating techniques (based upon pollen, 137Cs, 210Pb and total Pb) were applied to selected cores, suggesting accretion rates from 0.25 to 0.31 cm yr-1 which are higher than the rates of local relative sea level rise. Correlation of trace metal densities (Cu, Fe, Pb and Zn) to Al densities were used to justify Al normalization. After consideration of natural sources and adsorption factors, the normalized Pb profiles are shown to reflect historical pollution levels of leaded gasoline consumption. Carbon storage values in the upper 25 cm of sediment range from 7.3--10.5 kg C m-2 and carbon accumulation rates vary from 95 to 124 g C m-2 yr-1, representing 15--29% of the salt marsh macrophyte productivity.

[Truncated abstract] The principal aim of this thesis was to examine the response of the microbial community to the addition of small amounts (<50 μg C g-1 soil) of organic C substrates (‘trigger molecules’) to soil. This addition is comparative to indigenous soluble C concentrations for a range of soil types in Western Australia (typically measured between 20 and 55 μg C g-1 soil). Previously it has been reported that the application of trigger molecules to European soils has caused more CO2-C to be evolved (up to six fold) than was applied . . . Findings from this study indicated that there was an additional CO2 release (i.e. greater than the C added) on application of organic C substrates to some soil treatments. However, findings from this study indicate that the response of the microbial community to small additions of soluble C substrate is not consistent for all soil types and may vary due to greater availability of C, and supports the premise that microbial responses vary in a yet to be predicted manner between soil type and ecosystems. Differences in microbial response to the addition of soluble organic C are likely attributable to differences in soil attributes and environmental factors influencing both the diversity of microbes present and the frequency of food events. Theoretically, trigger molecules could also provide a possible control mechanism for microorganisms in arable farming systems. These mechanisms include stimulating either targeted pathogenic microorganisms that starve after depletion of a suitable substrate; or stimulating beneficial microorganisms to manipulate nutrient cycling, by targeting specific functional groups and altering mineralisation and immobilisation turnover rates.