The origin and evolution of deep groundwater in the 2.5 km deep Outokumpu Deep Drill Hole in eastern Finland was investigated using geochemical and isotopic methods. The sample material included water and gas derived from the drill hole by tube sampling, pumping and pressurized methods, as well as fracture minerals. Similar results were obtained for water samples using different sampling techniques. However, as uncontrolled degassing took place during tube sampling and pumping, it is suggested that pressurized methods should be used for gas sampling.

Five water types were discerned along the drill hole, which reflect changes in lithology and indicate isolation from the surface and from each other within the Outokumpu bedrock. An evolutionary model was proposed that includes precipitation and infiltration of meteoric water at warmer than present climatic conditions, a shift in the stable isotopic composition of water and an increase in salinity through waterrock interaction between virtually stagnant groundwater and the bedrock, and both the abiotic and biotic formation of hydrocarbons. Two independent lines of evidence from water stable isotopes and the accumulation of radiogenic and nucleogenic noble gases indicated isolation of the Outokumpu Deep Drill Hole groundwaters from the meteoric water cycle from the Eocene-Miocene epochs, placing the evolutionary model in the time frame of millions to tens of millions of years.

The results shed light on how deep groundwaters have evolved in geochemical and microbiological processes through time and space. Furthermore, they emphasise the complexity of these environments, as they are being increasingly utilised for underground construction, and provide background information for assessment of the long-term safety of nuclear waste disposal.

]]>This thesis aims to 1) examine the most influential watershed properties determining spatial variation in stream water quality; 2) identify key water quality and watershed variables controlling stream biotic responses (i.e. diatom community composition); 3) investigate the effects of multiscale temporal variation on urban runoff in cold climatic regions; and 4) evaluate whether advanced statistical methods are applicable in hydrogeographical modeling of small watersheds. To fulfill these objectives, spatial watershed-scale analyses were conducted using modern non-parametric approaches and theory-driven methods such as structural equation modeling. This thesis is based on unique data sets of both multibasin and multiyear sampling and spatial data from the Helsinki region, southern Finland.

A combination of GIS-based approaches and statistical analyses revealed significant links and novel insights into complex relationships between water quality and spatial biogeophysical properties of the surrounding landscape. The importance of land cover was emphasized throughout the thesis. Under base flow conditions the significance of soil type was mainly controlled by land cover. Further, this thesis demonstrates how land cover and stream water quality strongly determine the spatial assemblages of aquatic biota, as elevated pollutant levels were linked to decreased species richness and dominance of more tolerant species of diatom taxa. From a temporal perspective, the results suggest that urban runoff pollution is a chronic phenomenon, and is controlled by both runoff volume (summer) and pollutant sources (winter). Both the divergent temporal behavior and dominant role of diffuse pollution sources indicated challenges for stream water management practices. Based on the observed substance levels, year-round runoff treatment in urban areas is highly recommended. Finally, this thesis increases our knowledge of stream water quality variation in space and time. In this thesis, key local phenomena in contemporary hydrogeography were identified with a spatial modeling framework. The inclusion of indirect effects into the models improved our understanding of these systems, thus emphasizing the importance of simultaneously studying multiple concurrent processes.

]]>In the first part of the thesis we define generalized Kakeya sets in metric spaces satisfying certain axioms. These allow us to prove some lower bounds for the Hausdorff dimension of generalized Kakeya sets using two methods introduced in the Euclidean context by Bourgain and Wolff. With this abstract setup we can deal with many special cases in a unified way, recovering some known results and proving new ones.

In the second part we present various applications. We recover some of the known estimates for the classical Kakeya and Nikodym sets and for curved Kakeya sets. Moreover, we prove lower bounds for the dimension of sets containing a segment in a line through every point of a hyperplane and of an (n-1)-rectifiable set. We then show dimension estimates for Furstenberg type sets (already known in the plane) and for the classical Kakeya sets with respect to a metric that is homogeneous under non-isotropic dilations and in which balls are rectangular boxes with sides parallel to the coordinate axis. Finally, we prove lower bounds for the classical bounded Kakeya sets and a natural modification of them in Carnot groups of step two whose second layer has dimension one, such as the Heisenberg group. On the other hand, if the dimension is bigger than one we show that we cannot use this approach.

]]>We also use game theoretical methods to study the evolution of trade-offs: another pattern ubiquitous in nature. Specifically, we model an annual plant population and study the correlation of seed size and germination time. We do not assume any physiological constraints on the production of seeds of any combination of size and germination time. However, we find that typically an Evolutionarily Stable Strategy is such that a correlation emerges between the two. This raises the general question whether trade-offs observed in nature are caused by physiological constraints or whether they are just implementations of an evolutionarily beneficial strategy.

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