Kaksikertasironnan simulointi

Mahdollisimman tarkka tieto varatun hiukkasen energianmenetyksestä sen kulkiessa näytteessä on usein hyvin olennaista varteenotettavien tutkimustulosten aikaansaamiseksi monilla eri fysiikan suuntautumisaloilla. Aihe onkin hyvin laajalti tutkittu. Kehityksen kuitenkin edetessä yhä pienempiin mittasuhteisiin ja tarkempiin arvoihin on tärkeää, että myös ionien energianmenetyksestä väliaineessa saadaan yhä tarkempaa tietoa. Takaisinsirontaspektrometriassa tarkastellaan näytteestä sironneita ammusioneja. Takaisinsironnan avulla voidaan tunnistaa näytteen sisältämät alkuaineet, selvittää syvyysjakauma ja näytteen alkuaineiden suhteelliset runsaudet. Menetelmään liittyvät ilmiöt ovat varsin monimutkaisia ja niiden teoreettinen mallintaminen siten haasteellista. Kun tavoitteena on simuloida mahdollisimman tarkasti tilannetta, jossa kiihdytetty ioni etenee näytteessä ei analyyttinen ratkaisumalli välttämättä ole paras vaihtoehto. Tilannetta kuvaamaan onkin kehitetty useita eri laskennallisia menetelmiä. Tässä työssä tarkasteltiin sitä kuinka paljon kaksikertasironnan huomioon ottaminen vaikuttaa tuloksiin takaisinsirontaa simuloitaessa. Useimmat takaisinsironnan mallinnusohjelmat ottavat huomioon ainoastaan yksikertasironnan. Tämä on varsin ymmärrettävää, sillä jo toisen sirontatapahtuman huomioon ottaminen ja mallintaminen analyyttisesti lisää huomattavasti simulaation laskutapahtumien lukumäärää ja hidastaa siten itse simulaatiota. Työtä varten kirjoitettiin ohjelma, jolla simuloituja tuloksia verrattiin sekä näytteistä mitattuihin että toisella simulaatio-ohjelmalla tuotettuihin spektreihin. Vertailusta kävi selvästi ilmi kaksikertasironnan merkitys takaisinsirontaa simuloitaessa. Yksikertasironnan tuoma informaatio päättyy energiaan, jolla näytteen takareunasta sironnut ioni havaitaan ilmaisimessa. Toisen sirontatapahtuman huomioon ottaminen tuo lisäinformaatiota etenkin spektrin häntäalueella. Laaditulla ohjelmalla pystyttiin nyt käsittelemään ainoastaan erikoistapausta, jossa ionisuihku ammuttiin kohtisuoraan näytteeseen. Looginen jatkotoimenpide työn parissa olisi laajentaa ohjelma käsittämään muutkin ionisuihkun tulokulmat.

Satelliitti-instrumentti IASI ja sen sovellukset sääpalvelulle

IASI on vuodesta 2007 käytössä ollut satelliitti-instrumentti Metop-polaarisatelliitissa. IASI-mittauksista johdettuja lopputuotteita ovat mm. lämpötilan ja kosteuden pystyprofiilit, pilven ylärajan lämpötila ja paine sekä eri hivenkaasujen pitoisuudet. Tämä työ on alkua IASI:n käyttöönotolle Ilmatieteen laitoksella. Työssä selvitetään IASI:n lämpötilaprofiileiden ja pilven ylärajan paineen soveltuvuutta sääpalvelulle vertailemalla niitä jo käytössä oleviin sääpalvelun työkaluihin. IASI-mittauksista johdettuja lämpötilaprofiileita verrataan Ilmatieteen laitoksen operatiivisiin pintaluotauksiin. Lisäksi tarkastellaan IASI:n lämpötilaprofiileiden vaikutusta paikallisen analyysi- ja ennustustyökalu LAPS:in lämpötila-analyysiin. IASI:n pilven ylärajan lämpötiloja verrataan AVHRR-radiometrista johdettuihin pilven ylärajan lämpötiloihin. IASI:sta ja AVHRR:stä johdetut keskimääräiset lämpötilat olivat lähes samat alapilville. Yläpilville ja osittain läpinäkyville cirrus-pilville lämpötilaero oli noin 5 Celsius-astetta. IASI:n lämpötilaluotaukset osoittautuivat käyttökelpoisiksi etenkin keski- ja ylätroposfäärissä (350 - 600 hPa), jossa IASI:n antama lämpötila erosi pintaluotauksen lämpötilasta vain noin +-1 Celsius-astetta. IASI:n lämpötilaluotausten suurin ongelma on mittausten katkeaminen pilven ylärajaan. IASI-luotauksilla oli suuri vaikutus LAPS-lämpötila-analyysiin mallin koko alueella, mutta vertailuaineiston puutteessa ei voida varmasti sanoa onko vaikutus positiivinen vai negatiivinen. Tulokset ovat lupaavia. IASI:n lämpötilaluotaukset ja pilven ylärajan lämpötila vaikuttavat käyttökelpoisilta sääpalvelun tarpeisiin.

Lumi ilmaston osana - Lumen vesiarvon ja pinnan albedon mallintaminen Pohjois-Euraasian alueella

Työssä tarkasteltiin ilmakehän yleisen kiertoliikkeen mallin, ECHAM5:n, ja Euroopan keskipitkien sääennusteiden keskuksen uudelleenanalyysijärjestelmän, ERA-40:n, lumen vesiarvon ja lumisten alueiden pinnan albedon mallintamista. Tarkoituksena oli selvittää näiden välisiä eroja sekä sitä, kuinka hyvin ECHAM5 kuvaa nykyilmaston lumioloja. Esimerkinomaisesti tarkasteltiin myös Rossby-keskuksen alueellisen ilmastomallin, RCA3:n, lumen mallintamistapaa. ECHAM5-simulaatioissa käytetty pakote oli havaintojen mukainen meriveden pintalämpötilan ja merijään jakauma. ECHAM5:n ja ERA-40:n aineistoja vertailtiin jaksolla 1986-1990 Pohjois-Euraasian alueella. ERA-40:n lumen vesiarvoja verrattiin lisäksi INTAS-SCCONE-hankkeen havaintoaineistoon. Saatujen tulosten mukaan ECHAM5:n lumen vesiarvo oli monilla alueilla ERA-40:n lumen vesiarvoa pienempi. Suurimmillaan erot olivat vesiarvon maksimialueilla Euraasian keskiosissa. ECHAM5:ssä myös eri vuosien välinen vaihtelu oli pienempää kuin ERA-40:ssä. Varsinkin tarkastelujakson viimeisinä vuosina, 1989 ja 1990, lumen vesiarvo sai Pohjois-Euroopan alueella ERA-40:n mukaan hyvin matalia arvoja, jotka selittyvät NAO-indeksin korkeilla arvoilla. NAO-ilmiön voimakkuus 1980-luvun lopulla ei kuitenkaan erotu ECHAM5:n lumen vesiarvossa. ERA-40:n lumianalyysissä on mukana lumensyvyyshavaintoja, mikä on suurin tuloksiin eroa aiheuttava tekijä. Lienee myös mahdollista, että ECHAM5-simulaatioissa käytetty pakote ei ole riittävän voimakas tuottamaan kaikilta osin realistista lumen vesiarvon jakaumaa. ERA-40:n ja INTAS-SCCONE-aineiston välillä ei ollut kovin suuria eroja. Lumisten alueiden pinnan albedon osana käytetty lumialbedo on ERA-40:ssä ennustettava muuttuja, ECHAM5:ssä se parametrisoidaan. Saatujen tulosten mukaan pinnan albedon arvot ovat ECHAM5:ssä laajalti suurempia kuin ERA-40:ssä. Erot aiheutuvat albedojen erilaisesta laskentatavasta sekä mallien erilaisista kasvillisuusjakaumista. ECHAM5 aliarvioi kasvillisuuden albedoa pienentävän vaikutuksen varsinkin pohjoisen havumetsävyöhykkeen alueella. ERA-40:n pinnan albedo lieneekin realistisempi kuin ECHAM5:n.

Autoxidation of conjugated linoleic acid methyl ester in the presence of α-tocopherol: the hydroperoxide pathway

The autoxidation of conjugated linoleic acid (CLA) is poorly understood in spite of increasing interest in the beneficial biological properties of CLA and growing consumption of CLA-rich foods. In this thesis, the autoxidation reactions of the two major CLA isomers, 9-cis,11-trans-octadecadienoic acid and 10-trans,12-cis-octadecadienoic acid, are investigated. The results contribute to an understanding of the early stages of the autoxidation of CLA methyl ester, and provide for the first time a means of producing and separating intact CLA methyl ester hydroperoxides as well as basic knowledge on lipid hydroperoxides and their hydroxy derivatives. Conjugated diene allylic monohydroperoxides were discovered as primary autoxidation products formed during autoxidation of CLA methyl esters in the presence and absence of α-tocopherol. This established that one of the autoxidation pathways of CLA methyl ester is the hydroperoxide pathway. Hydroperoxides were produced from the two major CLA methyl esters by taking advantage of the effect of α-tocopherol to promote hydroperoxide formation. The hydroperoxides were analysed and separated first as methyl hydroxyoctadecadienoates and then as intact hydroperoxides by HPLC. The isolated products were characterized by UV, GC-MS, and NMR techniques. In the presence of a high amount of α-tocopherol, the autoxidation of CLA methyl ester yields six kinetically-controlled conjugated diene monohydroperoxides and is diastereoselective in favour of one particular geometric isomer as a pair of enantiomers. The primary autoxidation products produced from the two major CLA isomers include new positional isomers of conjugated diene monohydroperoxides, the 8-, 10-, 12-, and 14-hydroperoxyoctadecadienoates. Furthermore, two of these new positional isomers have an unusual structure for a cis,trans lipid hydroperoxide where the allylic methine carbon is adjacent to the cis instead of the usual trans double bond. The 1H and 13C NMR spectra of nine isomeric methyl hydroxyoctadecadienoates and of ten isomeric methyl hydroperoxyoctadecadienoates including the unusual cis,trans hydroperoxides, i.e. Me 8-OOH-9c,11t and Me 14-OOH-10t,12c, were fully assigned with the aid of 2D NMR spectroscopy. The assigned NMR data enabled determination of the effects of the hydroxyl and hydroperoxyl groups on the carbon chemical shifts of CLA isomers, identification of diagnostic signals, and determination of chemical shift differences of the olefinic resonances that may help with the assignment of structure to as yet unknown lipid hydroperoxides either as hydroxy derivatives or as intact hydroperoxides. A mechanism for the hydroperoxide pathway of CLA autoxidation in the presence of a high amount of α-tocopherol was proposed based on the characterized primary products, their relative distribution, and theoretical calculations. This is an important step forward in CLA research, where exact mechanisms for the autoxidation of CLA have not been presented before. Knowledge of these hydroperoxide formation steps is of crucial importance for understanding the subsequent steps and the different pathways of the autoxidation of CLA. Moreover, a deeper understanding of the autoxidation mechanisms is required for ensuring the safety of CLA-rich foods. Knowledge of CLA oxidation and how it differs from the oxidation of nonconjugated polyunsaturated fatty acids may also be the key to understanding the biological mechanisms of CLA activity.

Aspects and Applications of Pulse Sequence Design for Solution-State Nuclear Magnetic Resonance Spectroscopy

NMR spectroscopy enables the study of biomolecules from peptides and carbohydrates to proteins at atomic resolution. The technique uniquely allows for structure determination of molecules in solution-state. It also gives insights into dynamics and intermolecular interactions important for determining biological function. Detailed molecular information is entangled in the nuclear spin states. The information can be extracted by pulse sequences designed to measure the desired molecular parameters. Advancement of pulse sequence methodology therefore plays a key role in the development of biomolecular NMR spectroscopy. A range of novel pulse sequences for solution-state NMR spectroscopy are presented in this thesis. The pulse sequences are described in relation to the molecular information they provide. The pulse sequence experiments represent several advances in NMR spectroscopy with particular emphasis on applications for proteins. Some of the novel methods are focusing on methyl-containing amino acids which are pivotal for structure determination. Methyl-specific assignment schemes are introduced for increasing the size range of 13C,15N labeled proteins amenable to structure determination without resolving to more elaborate labeling schemes. Furthermore, cost-effective means are presented for monitoring amide and methyl correlations simultaneously. Residual dipolar couplings can be applied for structure refinement as well as for studying dynamics. Accurate methods for measuring residual dipolar couplings in small proteins are devised along with special techniques applicable when proteins require high pH or high temperature solvent conditions. Finally, a new technique is demonstrated to diminish strong-coupling induced artifacts in HMBC, a routine experiment for establishing long-range correlations in unlabeled molecules. The presented experiments facilitate structural studies of biomolecules by NMR spectroscopy.

Cellulose Derivatives : Synthesis, Properties and Applications

Even though cellulose is the most abundant polymer on Earth, its utilisation has some limitations regarding its efficient use in the production of bio-based materials. It is quite clear from statistics that only a relatively small fraction of cellulose is used for the production of commodity materials and chemicals. This fact was the driving force in our research into understanding, designing, synthesising and finding new alternative applications for this well-known but underused biomaterial. This thesis focuses on the developing advanced materials and products from cellulose by using novel approaches. The aim of this study was to investigate and explore the versatility of cellulose as a starting material for the synthesis of cellulose-based materials, to introduce new synthetic methods for cellulose modification, and to widen the already existing synthetic approaches. Due to the insolubility of cellulose in organic solvents and in water, ionic liquids were applied extensively as the reaction media in the modification reactions. Cellulose derivatives were designed and fine-tuned to obtain desired properties. This was done by altering the inherent hydrogen bond network by introducing different substituents. These substituents either prevented spontaneous formation of hydrogen bonding completely or created new interactions between the cellulose chains. This enabled spontaneous self-assembly leading to supramolecular structures. It was also demonstrated that the material properties of cellulose can be modified even those molecules with a low degree of substitution when highly hydrophobic films and aerogels were prepared from fatty acid derivatives of nanocellulose. Development towards advanced cellulose-based materials was demostrated by synthesising chlorophyllcellulose derivatives that showed potential in photocurrent generation systems. In addition, liquid crystalline cellulose derivatives prepared in this study, showed to function as UV-absorbers in paper.

Alueellinen imago ja identiteetti liikkeessä

Regions are considered to be in competition for investments, industries, inhabitants and skilled labour nationally as well as internationally. In the context of tightening competition, more and more attention has been paid to regional attractors. A positive image is an important attractor in regional competition. In Finland, many towns and regions have either implemented or are planning to implement various image-enhancing campaigns or other measures aimed at improving their image. The role of identity is very important in developing a regional image. Good regional image should be based on a strong regional identity and awareness. Related to this is the perception of one's own region as separate from others and the familiarity of the region. If a region has no place in the awareness of its residents or if the inhabitants do not identify with it, its very existence as a social construct can be questioned. This means that building the regional image, which in this context is seen as social constructivism, is extremely difficult if the degree of regional awareness and identification is low. On the other hand, regional identity is being built also by developing the regional image. In a way, regional discourses have become more marketing-oriented in that instead of trying to create a regional esprit de corps there is now more image-oriented speech aimed at striving to improve the attractivity to outsiders of the region. Even though the goal is to bring the region to the attention of non-residents, a measure of construction of regional identity for the local population is automatically effected at the same time. Regional image and identity are consequences of linguistic producing and understanding of a region. It means that both image and identity are seen as language-created social constructions. The regional image is created through various discourses, but also the construction of a regional identity as regional consciousness and identification is largely a linguistic process. Essential in this context is perceiving the region as a discursive project characterized by its representation as texts, images and symbols. The linguistic production of a region is not a neutral description of "reality", but a representation based on interpretations, experiences and different motivations. Production and perceiving vary in time, so regional image and identity are on the move. This research is driven by the ongoing change of the regional system. The municipal and service structure reform is in progress and the number of municipalities seems to be on the decrease. At the same time, European Union s regional policy and regionalism on the whole are changing the status of sub-regions. At municipal level the crucial question is how the municipal structure reform will affect regional identity. This study points out that strong sense of municipal identity is a source of opposition to changes in municipal structure, but on the other hand the deinstitutionalization of the old municipality in municipal merger does not in itself mean the weakening of municipal identity.

Aika ennen aluepolitiikkaa. Pohjoisen kehityshankkeet ja alueiden kehittämisen idea 1950-luvun Suomessa

The dissertation focuses on the recognition of the problems of uneven regional development in Finland in the 1950s, and the way the idea of controlling this development was introduced to Finnish politics. Since it is often stated that Finnish regional policy only began in the mid-1960s, the period at hand is considered to fall in the time before regional policy. However, various ideas, plans and projects of regional development as well as different aims of development were brought forward and discussed already in the 1950s. These give an interesting perspective to the ideas of later regional development. In the 1950s, many Finnish politicians became more conscious of the unavoidable societal change. The need for overall modernisation of the society made it reasonable to expect a growing level of unemployment and eagerness to migration. The uneven distribution of well-being was also feared to cause discontent and political changes. International experience proved interfering in the regional development possible when using the argument of public interest ; the measures taken increased the level of well-being, helped sustain societal balance, and supported national economy. Many of the development projects of the 1950s focused on Northern Finland, the natural resources of which were considered an important reserve and the political climate of which was regarded unstable. After the late 1940s, regional development was discussed frequently both on the national and the regional level. Direct and indirect support was given to less developed areas and the government outlined thorough investigations in order to relieve the regional problem. Towards the end of the decade, the measures taken were already often connected to the idea of equality. In the 1950s the conflicts within and between the largest Finnish political parties significantly affected the decisions of regional development. There are three case studies in this qualitative research based on the narrative method. The case studies clarify the characteristics of the 1950s regional development. In the first one, the representatives of the northern region and the state first discuss the location of a state-run nitrogen fertilizer factory and later the location of a new university. In the second, the aims and perspectives of private entrepreneurs and the state collide due to ideas of statist industrialisation projects and later due to an idea of a tax relief targeting northern industry. In the third case, the main role is given to the changing rural areas, in relation to which societal development and urbanisation were often measured. The regional development of the 1950s laid groundwork for the new, more established regional policy. The early problem solving actions were aimed both at the prevailing situation and the future and thus showed the way for the upcoming actions. Regional development policy existed already before regional policy.

Topographical, structural and geophysical characterization of fracture zones: implications for groundwater flow and vulnerability

The main objective of this study is to evaluate selected geophysical, structural and topographic methods on regional, local, and tunnel and borehole scales, as indicators of the properties of fracture zones or fractures relevant to groundwater flow. Such information serves, for example, groundwater exploration and prediction of the risk of groundwater inflow in underground construction. This study aims to address how the features detected by these methods link to groundwater flow in qualitative and semi-quantitative terms and how well the methods reveal properties of fracturing affecting groundwater flow in the studied sites. The investigated areas are: (1) the Päijänne Tunnel for water-conveyance whose study serves as a verification of structures identified on regional and local scales; (2) the Oitti fuel spill site, to telescope across scales and compare geometries of structural assessment; and (3) Leppävirta, where fracturing and hydrogeological environment have been studied on the scale of a drilled well. The methods applied in this study include: the interpretation of lineaments from topographic data and their comparison with aeromagnetic data; the analysis of geological structures mapped in the Päijänne Tunnel; borehole video surveying; groundwater inflow measurements; groundwater level observations; and information on the tunnel s deterioration as demonstrated by block falls. The study combined geological and geotechnical information on relevant factors governing groundwater inflow into a tunnel and indicators of fracturing, as well as environmental datasets as overlays for spatial analysis using GIS. Geophysical borehole logging and fluid logging were used in Leppävirta to compare the responses of different methods to fracturing and other geological features on the scale of a drilled well. Results from some of the geophysical measurements of boreholes were affected by the large diameter (gamma radiation) or uneven surface (caliper) of these structures. However, different anomalies indicating more fractured upper part of the bedrock traversed by well HN4 in Leppävirta suggest that several methods can be used for detecting fracturing. Fracture trends appear to align similarly on different scales in the zone of the Päijänne Tunnel. For example, similarities of patterns were found between the regional magnetic trends, correlating with orientations of topographic lineaments interpreted as expressions of fracture zones. The same structural orientations as those of the larger structures on local or regional scales were observed in the tunnel, even though a match could not be made in every case. The size and orientation of the observation space (patch of terrain at the surface, tunnel section, or borehole), the characterization method, with its typical sensitivity, and the characteristics of the location, influence the identification of the fracture pattern. Through due consideration of the influence of the sampling geometry and by utilizing complementary fracture characterization methods in tandem, some of the complexities of the relationship between fracturing and groundwater flow can be addressed. The flow connections demonstrated by the response of the groundwater level in monitoring wells to pressure decrease in the tunnel and the transport of MTBE through fractures in bedrock in Oitti, highlight the importance of protecting the tunnel water from a risk of contamination. In general, the largest values of drawdown occurred in monitoring wells closest to the tunnel and/or close to the topographically interpreted fracture zones. It seems that, to some degree, the rate of inflow shows a positive correlation with the level of reinforcement, as both are connected with the fracturing in the bedrock. The following geological features increased the vulnerability of tunnel sections to pollution, especially when several factors affected the same locations: (1) fractured bedrock, particularly with associated groundwater inflow; (2) thin or permeable overburden above fractured rock; (3) a hydraulically conductive layer underneath the surface soil; and (4) a relatively thin bedrock roof above the tunnel. The observed anisotropy of the geological media should ideally be taken into account in the assessment of vulnerability of tunnel sections and eventually for directing protective measures.

Aluesuunnittelu ja kestävä kehitys Luoteis-Venäjällä : Ympäristösuunnittelun mahdollisuus paikallisissa hallintatavoissa

In this Ph.D. thesis I have studied how the objectives of sustainable development have been integrated into Northwest Russian urban and regional planning, and how the Russian planning discourse has changed after the collapse of the Soviet Union. By analysing the planning discussion, processes, and strategic documents I have also investigated the use of power and governmentality in urban and regional planning. As a methodological foundation I have used an approach that I call geographical constructivism . It was possible to answer in a relevant manner the question of how sustainable development has become a part of planning in Northwest Russia through a discourse analysis of the planning discussion. During the last decades, the aim of sustainable development has become globally one of the most central societal challenges. Urban and regional planning has a central role to play in promoting this process, since many meta-level objectives actually take shape within its sphere. An ever more actual challenge brought by sustainable development is to plan regions and places while balancing the conflicts of the pressures of safeguarding a good environment and of taking into consideration social and economic needs. I have given these unavoidable conflicts of sustainable development a central place in my work. In my view, complementing instrumental and communicative rationality with conflict rationality gives environmental planning a well-equipped toolbox. Sustainable development can be enhanced in urban and regional planning by seeking open, and especially hidden, potential conflicts. Thus, the expressed thinking (mentality) and actions taken by power regimes in and around conflicts open an interesting viewpoint into Northwest Russian governmentality. I examine the significance of sustainable development in planning through Northwest Russian geography, and also through recent planning legislation and four case studies. In addition, I project my analysis of empirical material onto the latest discussion of planning theory. My four case studies, which are based on independent and separate empirical material (42 thematic interviews and planning documents), consider the republics of Karelia and Komi, Leningrad oblast and the city of Saint Petersburg. In the dissertation I argue how sustainable development is, in the local governmentalities of Northwest Russia, understood as a concept where solving environmental problems is central, and that they can be solved through planning carried out by the planning professionals. Despite this idealism, environmental improvements have been overlooked by appealing to difficult economic factors. This is what I consider environmental racism, which I think is the most central barrier to sustainable development in Northwest Russia. The situation concerning the social dimension of sustainable development is even more difficult, since, for example, the development of local democracy is not highly valued. In the planning discourse this democracy racism is explained by a short history of democracy in Russia. However, precisely through planning conflicts, for example in St. Petersburg, planning has become socially more sustainable: protests by local inhabitants have bypassed the poorly functioning representational democracy, when the governmentality has changed from a mute use of power to one that adopts a stand on a conflicting issue. Keywords: Russia, urban and regional planning, sustainable development, environmental planning, power and conflicts in planning, governmentality, rationalities.

Lake sediment research as a part of lake management - case studies and implications from southern Finland

In Finland one of the most important current issues in the environmental management is the quality of surface waters. The increasing social importance of lakes and water systems has generated wide-ranging interest in lake restoration and management, concerning especially lakes suffering from eutrophication, but also from other environmental impacts. Most of the factors deteriorating the water quality in Finnish lakes are connected to human activities. Especially since the 1940's, the intensified farming practices and conduction of sewage waters from scattered settlements, cottages and industry have affected the lakes, which simultaneously have developed in to recreational areas for a growing number of people. Therefore, this study was focused on small lakes, which are human impacted, located close to settlement areas and have a significant value for local population. The aim of this thesis was to obtain information from lake sediment records for on-going lake restoration activities and to prove that a well planned, properly focused lake sediment study is an essential part of the work related to evaluation, target consideration and restoration of Finnish lakes. Altogether 11 lakes were studied. The study of Lake Kaljasjärvi was related to the gradual eutrophication of the lake. In lakes Ormajärvi, Suolijärvi, Lehee, Pyhäjärvi and Iso-Roine the main focus was on sediment mapping, as well as on the long term changes of the sedimentation, which were compared to Lake Pääjärvi. In Lake Hormajärvi the role of different kind of sedimentation environments in the eutrophication development of the lake's two basins were compared. Lake Orijärvi has not been eutrophied, but the ore exploitation and related acid main drainage from the catchment area have influenced the lake drastically and the changes caused by metal load were investigated. The twin lakes Etujärvi and Takajärvi are slightly eutrophied, but also suffer problems associated with the erosion of the substantial peat accumulations covering the fringe areas of the lakes. These peat accumulations are related to Holocene water level changes, which were investigated. The methods used were chosen case-specifically for each lake. In general, acoustic soundings of the lakes, detailed description of the nature of the sediment and determinations of the physical properties of the sediment, such as water content, loss on ignition and magnetic susceptibility were used, as was grain size analysis. A wide set of chemical analyses was also used. Diatom and chrysophycean cyst analyses were applied, and the diatom inferred total phosphorus content was reconstructed. The results of these studies prove, that the ideal lake sediment study, as a part of a lake management project, should be two-phased. In the first phase, thoroughgoing mapping of sedimentation patterns should be carried out by soundings and adequate corings. The actual sampling, based on the preliminary results, must include at least one long core from the main sedimentation basin for the determining the natural background state of the lake. The recent, artificially impacted development of the lake can then be determined by short-core and surface sediment studies. The sampling must be focused on the basis of the sediment mapping again, and it should represent all different sedimentation environments and bottom dynamic zones, considering the inlets and outlets, as well as the effects of possible point loaders of the lake. In practice, the budget of the lake management projects of is usually limited and only the most essential work and analyses can be carried out. The set of chemical and biological analyses and dating methods must therefore been thoroughly considered and adapted to the specific management problem. The results show also, that information obtained from a properly performed sediment study enhances the planning of the restoration, makes possible to define the target of the remediation activities and improves the cost-efficiency of the project.

Paleomagnetic and rock magnetic study with emphasis on the Precambrian intrusions and impact structures in Fennoscandia and South Africa

The importance of supercontinents in our understanding of the geological evolution of the planet Earth has been recently emphasized. The role of paleomagnetism in reconstructing lithospheric blocks in their ancient paleopositions is vital. Paleomagnetism is the only quantitative tool for providing ancient latitudes and azimuthal orientations of continents. It also yields information of content of the geomagnetic field in the past. In order to obtain a continuous record on the positions of continents, dated intrusive rocks are required in temporal progression. This is not always possible due to pulse-like occurrences of dykes. In this work we demonstrate that studies of meteorite impact-related rocks may fill some gaps in the paleomagnetic record. This dissertation is based on paleomagnetic and rock magnetic data obtained from samples of the Jänisjärvi impact structure (Russian Karelia, most recent 40Ar-39Ar age of 682 Ma), the Salla diabase dyke (North Finland, U-Pb 1122 Ma), the Valaam monzodioritic sill (Russian Karelia, U-Pb 1458 Ma), and the Vredefort impact structure (South Africa, 2023 Ma). The paleomagnetic study of Jänisjärvi samples was made in order to obtain a pole for Baltica, which lacks paleomagnetic data from 750 to ca. 600 Ma. The position of Baltica at ca. 700 Ma is relevant in order to verify whether the supercontinent Rodinia was already fragmented. The paleomagnetic study of the Salla dyke was conducted to examine the position of Baltica at the onset of supercontinent Rodinia's formation. The virtual geomagnetic pole (VGP) from Salla dyke provides hints that the Mesoproterozoic Baltica - Laurentia unity in the Hudsonland (Columbia, Nuna) supercontinent assembly may have lasted until 1.12 Ga. Moreover, the new VGP of Salla dyke provides new constraint on the timing of the rotation of Baltica relative to Laurentia (e.g. Gower et al., 1990). A paleomagnetic study of the Valaam sill was carried out in order to shed light into the question of existence of Baltica-Laurentia unity in the supercontinent Hudsonland. Combined with results from dyke complex of the Lake Ladoga region (Schehrbakova et al., 2008) a new robust paleomagnetic pole for Baltica is obtained. This pole places Baltica on a latitude of 10°. This low latitude location is supported also by Mesoproterozoic 1.5 1.3 Ga red-bed sedimentation (for example the Satakunta sandstone). The Vredefort impactite samples provide a well dated (2.02 Ga) pole for the Kaapvaal Craton. Rock magnetic data reveal unusually high Koenigsberger ratios (Q values) in all studied lithologies of the Vredefort dome. The high Q values are now first time also seen in samples from the Johannesburg Dome (ca. 120 km away) where there is no impact evidence. Thus, a direct causative link of high Q values to the Vredefort impact event can be ruled out.