• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 4
  • 1
  • Tagged with
  • 5
  • 4
  • 3
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 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.
1

Sulfatmätningar i kokeriet

Bergius, Lina January 2015 (has links)
Arbetet har mestadels utförts i kokeriet på Domsjö Fabriker i syfte att kartlägga hur processförhållandena hänger samman med koncentrationen sulfatjoner. Detta för att lättare kunna undvika förhållanden i processen som innebär mycket höga värden. Arbetet ingår i examen för högskoleutbildningen: processoperatör vid Umeå Universitet.Vid Domsjö Fabriker har tidigare liknande mätningar gjorts i kokeriet och det har konstaterats att koncentrationen sulfatjoner hänger samman med pH och tid. Syftet är att djupare kartlägga hur processförhållandena hänger samman för att lättare kunna undvika förhållanden som innebär höga koncentrationer sulfatjoner. Målet med examensarbetet och dess undersökning är att sammanställa resultat som visar hur och när under koket som sulfatjoner bildas i stora mängder i kokeriet. Förfarandet av undersökningen har bestått i att prov tas ut i provserier om fyra provtillfällen per kok, fryses in och slutligen analyseras genom titrering och pH-mätning.Efter totalt 22 stycken provserier om fyra prov från de olika kokarna konstaterades att sulfatkoncentrationen är högst i slutet av nedgasningssteget. Det första provtillfället hade de högsta pH-värdena men också de lägsta koncentrationerna sulfat. Inget av dessa värden sticker ur och anses onormalt på något sätt. Om sulfatkoncentrationen påverkas av pH-värdet går inte att fastställa av detta arbete, då det inte är de lägsta pH-värdena som genererar de högsta sulfatkoncentrationerna utifrån resultatet i undersökningen. / This work has been performed in the digester at Domsjö Fabriker in order to clarify the concentration of sulphate-ions comparing to different driving-conditions in the process. The reason to this is to understand and be able to avoid conditions in the digester process that means very high concentrations of sulphate-ions. The work is included in the examination of higher education: process operator at Umeå University.At Domsjö Fabriker similar studies have been done in the digester and from that it has been found out that the concentration of sulphate-ions is connected to pH and over time. The purpose is to approve the understanding of the process conditions to avoid extremely high concentration of sulphate-ions. The mission with this work and the measurements included in the work is to put together results that show when the concentration of sulphate-ions is high. The procedure of the study has consisted in taking samples in series of four, frozen the samples and finally analyzing them by titration and pH-measurements.After 22 evaluated trial-series á four samples each from the boilers it was concluded that the concentration of sulphate-ions was the greatest in the end of this process-step. The pH was upper and the concentration of sulphate lower in the first sample. None of the data is abnormal in any way, and they are all connected and relevant to each other. In this experiment it is not possible to state if the concentration of sulphate is affected by the pH or not.
2

Composition Of Atmosphere At The Central Anatolia

Yoruk, Ebru 01 January 2004 (has links) (PDF)
Concentrations of elements and ions measured in samples collected between February 1993 and December 2000 at a rural site in central Anatolia were investigated to evaluate the chemical composition of atmosphere at central Anatolia, to determine pollution level of the region, to study temporal variability of the pollutants and to investigate the sources and source regions of air pollutants in the region. Level of pollution at central Anatolia was found to be lower than the pollution level at other European countries and Mediterranean and Black Sea regions of Turkey. Enrichment factor calculations revealed that SO42-, Pb and Ca are highly enriched in the aerosol / whereas, soil component has dominating contribution on observed concentrations of V, Mg, Ca and K. SO42-/(SO2+SO42-) ratio observed in &Ccedil / ubuk station indicates that contribution of distant sources is more important than the contribution of local sources on observed SO42- levels. SO42-/NO3- ratio calculations showed that Central Anatolia is receipt of SO42- from Eastern European countries. Positive Matrix Factorization (PMF) analysis revealed 6 source groups, namely motor vehicle source, mixed urban factor, long range transport factor, soil factor, NO3- factor and Cd factor. Distribution of Potential Source Contribution Function (PSCF) values showed that main source areas of SO42-, NH4+ and Cd are western parts of Turkey, Balkan countries, central and western Europe, central Russian Federation and north of Sweden and Finland / NO3- are the regions located around the Mediterranean Sea / and there is no very strong potential source area observed for NH3 and Pb.
3

The 200-year history of nss-SO42- concentration in snow and ice from Lomonosovfonna, Svalbard / Sulfatkoncentrationens 200-åriga historia i snö och is från Lomonosovfonna, Svalbard

Schoeps, Maria, Andersson, Josefin January 2015 (has links)
Environmental scientists use ice-core records to reconstruct past atmospheric conditions. Anthropogenic and natural sources of emissions can be traced when analyzing ions in the ice, which is included in the science of glaciochemistry. Sulfate is an excellent ion to use in these studies since it is traceable to these emissions. This study is therefore focused on the sulfate ion, how its concentration has fluctuated over the last 200-years and when a change of trend occurred. The ice-cores used in this study were extracted at Lomonosovfonna, Svalbard, and analyzed by Ion Chromatography (IC). The new data that has been brought forth in this study covers nss-SO42- concentrations in the years of 1998-2012 and is connected to previous extracted ice-core records. The results of nss-SO42- concentration in the ice-cores confirm the change of trend in the 1970s. The increasing trend in the result correlate with historical emissions and the decrease after the change of trend enhances less anthropogenic impact on the atmosphere. / Miljöforskare använder sig av isborrkärnor för att återskapa tidigare atmosfäriska förhållanden. Antropogena och naturliga utsläppskällor kan spåras genom att analysera joner i isen. Sulfat är en utmärkt jon att använda sig av i dessa studier, eftersom den kan anknytas till dessa utsläpp. Denna studie fokuserar därför på sulfatjonen, hur dess koncentration har ändrats under de senaste 200-åren och på det trendbrott som har ägt rum. Isborrkärnorna som har använts i denna studie borrades upp på Lomonosovfonna, Svalbard, och analyserades med jonkromato-grafi. Ny data som har tagits fram i den här studien täcker nss-SO42- koncentrationen mellan 1998-2012 och är sammankopplad med tidigare framtagen data från samma plats. Resultatet av nss-SO42- koncentrationen i isborrkärnorna bekräftar trendbrottet som inträffade på 1970-talet. Den ökande trenden i resultatet korrelerar med historiska utsläpp och minskningen efter trendbrottet påvisar mindre antropogen påverkan på atmosfären.
4

How Do Long-Term Declines in Anthropogenic Sulfur Dioxide Emissions and Sulfate Wet Deposition Compare with Trends in Freshwater Chemistry in Scandinavian Rivers? / Hur kan långsiktiga minskningar av antropogena svaveldioxidutsläpp och sulfat i nederbörd jämföras med trender i sötvattenkemi i skandinaviska vattendrag?

Georgii, Linnea January 2017 (has links)
Acidification of precipitation is an important environmental problem that emerged during the past century, especially after the Second World War. Acidification was primarily caused by human-made emissions of SOx (mostly SO2) and NOx, which are oxidized sulfur and nitrogen gases. The main sources of anthropogenic SOx emissions are non-ferrous ore refining, and the burning of fossil fuels and biofuels. SO2 emitted to the atmosphere combines with water vapor to produce sulfuric acid, which is one of the main compounds responsible for acid precipitation. In the 1970s and 1980s, more strict regulations regarding emissions of air pollutants such as SOx were established in Western Europe and North America, which led to declining levels of SO2 emissions and by this, declining levels of acidification in surface waters. This project was preformed by assembling and analyzing existing, publicly- available datasets of anthropogenic SO2 emissions for the period 1970 to 2010 from ten different regions in the Northern Hemisphere, and compare them with SO42- concentrations in precipitation and river chemistry in Sweden and Norway for the same period. It was discovered that it is the SO2 emissions from Northwestern Europe, the UK & Ireland and from the USA that have the greatest influence over the SO42- concentration in Scandinavian rivers. The SO42- concentration in stream water is also declining faster than the concentration in precipitation, with a faster decline in the southern parts of Scandinavia. / Försurning av nederbörd är ett miljöproblem som uppstod under det senaste århundradet, särskilt efter andra världskriget. Försurningen orsakades främst av mänskliga utsläpp av SOx (mestadels SO2) och NOx, vilka är oxiderade svavel- och kvävgaser. Huvudkällorna för dessa antropogena SOx-utsläpp är malmförädling samt förbränning av fossila bränslen och biobränslen. SO2 som släpps ut i atmosfären reagerar med vattenånga och bildar svavelsyra, vilket är en av huvudföreningarna ansvarig för sur nederbörd. På 1970- och 1980-talet fastställdes strängare bestämmelser beträffande utsläpp av luftföroreningar (som SOx) i Västra Europa och i Nordamerika. Detta ledde till minskande nivåer av SO2-utsläpp och genom denna sänkning även en minskning av försurning av ytvatten. Det här arbetet utfördes genom att befintlig, offentligt tillgänglig data samlades in och analyserades. Antropogena SO2-utsläpp för perioden 1970-2010 från tio olika regioner på norra halvklotet jämfördes med koncentrationer av SO42- i nederbörd och i vattendrag i Sverige och Norge för samma period. Genom detta fastslogs att de regioner som har störst inflytande över koncentrationen i skandinaviska vattendrag är SO2-utsläpp från nordvästra Europa, Storbritannien och Irland samt från USA. SO42- koncentrationen i vattendragen sjunker också snabbare än koncentrationen i nederbörden, med en snabbare nedgång i de södra delarna av Skandinavien.
5

Comparison Of The Rural Atmosphere Aerosol Compositions At Different Parts Of Turkey

Dogan, Guray 01 January 2005 (has links) (PDF)
Long term data generated at four rural stations are compared to determine similarities and differences in aerosol compositions and factors contributing to observed differences at different regions in Turkey. The stations used in this study are located at Mediterranean coast (20 km to the west of Antalya city), Black Sea coast (20 km to the east of Amasra town), Central Anatolia (&Ccedil / ubuk, Ankara) and Northeastern part of the Anatolian Plateau (at Mt. Uludag). Data used in comparisons were generated in previous studies. However, some re-analysis of data were also performed / (1) to improve the similarities of the parameters compared and (2) to be able to apply recently-developed methodologies to data sets. Data from Mediterranean and Black Sea stations were identical in terms of parameters measured and were suitable for extensive comparison. However, fewer parameters were measured at &Ccedil / ubuk and Uludag stations, which limited the comparisons involving these two stations. Comparison included levels of major ions and elements, short-term and seasonal variations in concentrations, background (baseline) concentrations of elements, flow climatology of regions, correlations between elements, potential source areas affecting regions, and source types affecting chemical composition of particles. Comparison of levels of measured parameters in four regions showed that there are some differences in concentrations that arise from differences in the local characteristics of the sampling points. For example very high concentrations of elements such as Na and Cl in the Mediterranean region is attributed to closer proximity of the Antalya station to coast and not a general feature of the Mediterranean aerosol. There are also significant regional differences in the concentrations of measured elements and ions as well. Concentrations of anthropogenic elements are very similar at two coastal stations (Antalya and Amasra), but they are approximately a factor of two smaller at the two stations that are located on the Anatolian Plateau. This difference between coastal and high altitude plateau stations, which is common to all anthropogenic species, is attributed to different source regions and transport mechanisms influencing coastal regions and Anatolian Plateau. Some statistically significant differences were also observed in the temporal variations of elements and ions measured in different stations. The elements with crustal origin showed similar seasonal pattern at all stations, with higher concentrations in summer and lower concentrations in winter. This difference between summer and winter is attributed to suppression of re-suspension of crustal aerosol from wet or ice-covered surface soil in winter. Concentrations of anthropogenic elements, on the other hand, did not show a statistically significant seasonal trend at Amasra, &Ccedil / ubuk and Uludag stations, but they have higher concentrations during summer months at the Antalya station. This difference between Mediterranean aerosol and aerosol at the Central and Northern Turkey is due to influence of more local sources on &Ccedil / ubuk, Amasra and Uludag stations and domination of more distant source in determining aerosol composition at the Mediterranean region. A similar conclusion of strong influence of local sources on chemical composition of particles at the Central Anatolia was also suggested by the comparison of baseline concentrations in each station. General features in flow climatology (residence times of upper atmospheric air masses) in each region are found to be similar with more frequent flow from W, WNW, NW and NNW wind sectors. Since these are the sectors that include high emitting countries in Eastern and Western Europe and Russia, transport from these sectors are expected to bring pollution from both distant European countries and more local Balkan countries and western parts of Turkey. Flow climatology in stations showed small, but statistically significant, differences between summer and winter seasons. These variations suggested that the station at the Central Anatolia and Black Sea (&Ccedil / ubuk Amasra and Uludag stations) are affected from sources located at the Western Europe in winter season and from sources located at the Eastern Europe in summer. Mediterranean aerosol, on the other hand, are affected from sources at the Western Europe and do not show any seasonal differences. This variation in flow climatology between summer and winter seasons (and lack of variation at the Mediterranean station) is supported by the seasonal variation (and lack of variation at the Mediterranean station) in SO42-/NO3- ratio measured at the stations. Potential source contribution function (PSCF) values are calculated for selected elements and ions in each station. Statistical significance of calculated PSCF values is tested using bootstrapping technique. Results showed that specific grids at Russia and at Balkan countries are common source regions affecting concentrations of anthropogenic elements at all four regions in Turkey. However, each station is also affected from specific source regions as well. Aerosol composition at the Anatolian Plateau are affected from sources closer to the sampling points whereas Mediterranean and Black Sea aerosol are affected from source regions that farther away from the receptors. It should be noted that the same conclusion is also reached in comparison of seasonal patterns and baseline concentrations at these stations. Types of sources affecting aerosol composition at Black Sea, Mediterranean and Central Anatolia are also compared. Source types affecting atmospheric composition in these regions were calculated using positive matrix factorization (PMF). The results showed that aerosol at the Black Sea, Central Anatolia and Mediterranean atmosphere consists of 8, 6 and 7 components, respectively. Two of these components, namely a crustal component and a long-range transport component are common in all three stations. The chemical compositions of these common components are shown to the same within 95% statistical significance interval. Three factors, namely a fertilizer factor, which is highly enriched in NH4+ ion, a sea salt component and an arsenic factor are common in the Mediterranean and Black Sea aerosol but not observed at the Central Anatolia. Other factors found in the regions are specific for that region.

Page generated in 0.0188 seconds