Browsing Matemaattis-luonnontieteellinen tiedekunta by Subject "Geologian ja geofysiikan maisteriohjelma"

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  • Voutilainen, Ahti (Helsingin yliopisto, 2021)
    A new ground motion prediction equation, named ON21, is solved for the ST1 Deep Heat enhanced geothermal system in Otaniemi, city of Espoo, Finland. The raw data from seismic events, that occurred during the stimulation of 2018, is processed, instrument response is removed, and frequency domain is used to obtain peak ground displacement, velocity, and acceleration. A database with 20,768 ground motion recordings from 204 events is compiled and used to solve a ground motion prediction equation for peak ground velocity and acceleration for vertical and horizontal movement. The model has a magnitude range from 0.0 to 1.8 on the scale of local magnitude used in Finland, and hypocentral distances of 0 km to 20 km. A 1σ value of 0.60 for vertical peak ground velocity model is lower than the 1σ of the models previously in use at Otaniemi and its surrounding areas. It is observed that the azimuth between the strike of the fault causing the earthquakes and the station recording the events seems to affect the peak ground motion values at a hypocentral distance of no more than 10 km, and beyond that the magnitude and distance are the dominant factors in the peak ground motion values. The new ground motion prediction equation model ON21 should be tested with ground motion data from earthquakes that occurred during the 2020 stimulations to assess its usefulness in predicting peak ground motion values, and to further study the effect of azimuth on the peak ground motion values.
  • Koskela, Elina (Helsingin yliopisto, 2019)
    Tiivistelmä/Referat – Abstract This study investigates temperature data that Posiva Oy has from the Olkiluoto and ONKALO® sites. The aim of the study was to create a unifying data classification for the existing temperature measurements, give an estimate of the initial undisturbed bedrock temperature and temperature gradient and model the temperature profiles in 3D. The thermal related issues, which the repository will undergo once in operating are significant and have fundamental contribution to the evolution of the repository, creating a need in such a study. Posiva Oy has temperature data obtained with four main methods; Geophysical drillhole loggings, Posiva flow log (PFL) measurements, thermal properties (TERO) measurements and Antares measurements. The data classification was carried out by creating a platform of quality aspects affecting the measurements. The classification was then applied for all the available data by inspecting the measurement specifics of each configuration and by observing the temperature/depth profiles with WellCad software. According to the specifics of each individual measurement the data was classified into three groups: A= the best data, recommended for further use, and which fulfils all quality criteria, B= data that should be used with reservation and which only partly fulfils quality criteria, and C= unusable data. Only data that showed no major disturbance within the temperature/depth profile (class A or B) were used in this study. All the temperature/depth data was corrected to the true vertical depth. The initial undisturbed average temperature of Olkiluoto bedrock at the deposition depth of 412 m and the temperature gradient, according to the geophysical measurements, PFL measurements (without pumping), TERO measurements and Antares measurements were found to be 10.93 ± 0.09°C and 1.47°C/100m, 10.85 ± 0.02°C and 1.43°C/100m, 10.60 ± 0.08°C and 1.65°C/100m, and 10.75°C and 1.39°C/100m, respectively. The 3D layer models presented in this study were generated by using Leapfrog Geo software. From the model a 10.5 – 12°C temperature range was obtained for the deposition depth of 412 – 432 m. The models indicated clear temperature anomalies in the volume of the repository. These anomalies showed relationship between the location of the major brittle fault zones (BFZ) of Olkiluoto island. Not all observed anomalies could be explained by a possible cause. Uncertainties within the modelling phase should be taken into consideration in further interpretations. By combining an up-to-date geological model and hydraulic model of the area to the temperature models presented here, a better understanding of the temperature anomalies and a clearer over all understanding of the thermal conditions of the planned disposal location will be achieved. Based on this study a uniform classification improves the usability of data and leads into a better understanding of the possibilities and weaknesses within it. The initial bedrock temperature and the temperature gradient in Olkiluoto present thermally a relatively uniform formation. The estimates of the initial bedrock temperatures and the temperature gradient presented in this study, endorse previous estimates. Presenting the classified temperature data in 3D format generated good results in the light of thermal dimensioning of Olkiluoto by showing distinct relationships between previously created brittle fault zone (fracture zone) models. The views and opinions presented here are those of the author, and do not necessarily reflect the views of Posiva.
  • Hekkala, Toni (Helsingin yliopisto, 2019)
    Arsenic (As) is a metalloid naturally present in the environment. Arsenic species vary in toxicity. Metal mining has contributed to the anthropogenic input of arsenic to groundwaters and surface waters. In this study, water samples were collected from 20 sample points in three mining-impacted study areas in Finland: the former Ylöjärvi Cu–W–As and Haveri Au–Cu mines, and the active Pyhäsalmi Zn–Cu mine. Six groundwater well samples, eleven surface water samples and three tailings seepage collection ditch samples were analyzed for dissolved arsenic speciation by HPLC-ICP-MS and for geochemical composition by ICP-MS, titration, and ion chromatography. Dissolved arsenic concentrations ranged from 14.2 to 6649 µg L-1 in samples collected at the Ylöjärvi study area, from 0.5 to 6.2 µg L-1 in samples collected at the Haveri study area, and from 0.2 to 9.4 µg L-1 in samples collected at the Pyhäsalmi study area. In all study areas, measured dissolved arsenic concentrations showed a general decrease from the tailings to the surroundings. Speciation analysis showed that two of the samples collected at the Ylöjärvi study area had arsenite [As(III)] as the dominant form of dissolved inorganic arsenic (iAs), three had arsenate [As(V)] as the dominant form of dissolved iAs, and four had a mixture of both. In the water samples collected at the Haveri and Pyhäsalmi study areas, all concentrations of dissolved arsenic species were below method detection limits. Also, none of the 22 water samples analyzed for arsenic speciation had dissolved MMA or DMA concentrations above method detection limits. Identification of dissolved arsenic species in the sampled waters in Haveri and Pyhäsalmi, and of MMA and DMA in all sampled waters requires more detailed study. A significant 2-tailed Pearson correlation between dissolved arsenic and dissolved molybdenum (Mo) (r=0.80**, n=20), and dissolved arsenic and dissolved potassium (K) (0.68**, n=19) suggests that in these three study areas the distributions of dissolved arsenic and Mo, as well as dissolved arsenic and K may be controlled by the same environmental variables. Anomalously high maximum concentrations of dissolved Al, Ca, Co, Cu, Fe, Ni, and SO4 were measured in surface water samples collected at the Ylöjärvi and Haveri study areas, and in a seepage collection ditch sample collected at the Pyhäsalmi study area.
  • Karjalainen, Aino (Helsingin yliopisto, 2020)
    NMR Services Australia (NMRSA) Pty Ltd has developed a Borehole Magnetic Resonance (BMR) tool which is based on the principles of nuclear magnetic resonance (NMR). Drillhole NMR tools have been used mostly in sedimentary environments for oil and gas exploration while applications in hard, heterogeneous, crystalline bedrock are still lacking. This study aims to test the BMR method in a hard rock environment, and for determining hydrogeological parameters in the spent nuclear fuel disposal site, the Olkiluoto island. Essentially, the objective is to design an optimal BMR data processing workflow and calibrate the estimated hydrogeological parameters, currently optimized for data from sedimentary environments, to suit the crystalline bedrock. For testing the BMR method in hard, crystalline bedrock, Posiva Oy, the Finnish expert organization responsible of spent nuclear fuel disposal, made test measurements in the drillholes of the spent nuclear fuel repository site, island of Olkiluoto. The collected data was processed with WellCAD software using additional NMR module. The BMR tool derives T2 distribution (representing pore size distribution), total porosity, bound water and moveable water volumes and permeability calculated with two different models. Some processing parameters (main/burst sequence, moving averages, temperature gradient, cutoff values) were tested and adjusted to fit into crystalline bedrock. Magnetizing material of the surface environment strongly disturbed the uppermost ~20.0 m portions of the measurement data. Some noise was encountered also deep in bedrock, which was cut away from the signal. A list of criteria was created for recognizing noise. The BMR data was compared with other drillhole data acquired by Posiva, i.e. fracture and lithology logs, seismic velocities and hydrogeological measurements. It was observed that the T2 distribution and total porosity correlate rather well to logged fractures and seismic velocities. Lithological variations did not correlate to BMR consistently, mostly because of the strong dependency on fracturing. Permeabilities were compared to earlier conducted hydrogeological measurements, with an intention to calibrate the permeability calculation models. However, this proved to be challenging due to the significant differences of the BMR method and conventional hydrogeological measurements. Preferably, the permeability models should be calibrated by laboratory calibration of the drillhole core, and possibly a new permeability model suitable for crystalline bedrock should be created.
  • Koskimaa, Kuutti (Helsingin yliopisto, 2020)
    AA Sakatti Mining Oy is researching the possibility of conducting mining operations in Sakatti ore deposit, located partially under the protected Viiankiaapa mire. In order to understand the waters in mining development site, the interactions of surface waters, shallow aquifers, and deep bedrock groundwaters must be understood. To estimate these interactions, hydrogeochemical characterization, together with four tracer methods were used: Tritium/helium, dichlorodifluoromethane and sulfur hexafluoride, stable isotopes of hydrogen and oxygen, and carbon-14. Most of the shallow groundwater samples are similar to the natural precipitation and groundwater in their chemical composition, being of Calcium bicarbonate type. B-11-17HYD013 was an exception, containing much more Cl and SO4. The samples from the deep 17MOS8193 all show a very typical composition for this type of a borehole, on the line between the saline Sodium sulphate and Sodium chloride water types. The samples from the 12MOS8102, as well as the river water samples and the Rytikuru spring sample are located between these two end members. The hydrogen and oxygen isotope values divided the samples into two distinct groups: those that show evaporation signal in the source water, and those that do not. The most likely source for the evaporated signal in the groundwaters is in the surface water pools in the Viiankiaapa mire, which have then infiltrated into the groundwater and followed the known groundwater flow gradient into the observation wells near the River Kitinen. Tritium showed no inclusion of recently recharged water in the deep 17MOS8193, and dated most of the shallow wells with screen below bedrock surface to be recharged in the 70’s and 80’s. B-10-17HYD017 had an older apparent age from 1955, and B-14-17HYD006 was curiously dated to be recharged in 2018. 14C gave apparent age of over 30 000 a for the deep 17MOS8193. The slight contents of 14C could be caused by slight contamination during sampling meaning the age is a minimum. The sample M-4-12MOS8102 got an apparent age of ~3 500 a, which could in turn be an overestimate due to ancient carbon being dissolved from the local bedrock fractures. CFC-12 showed apparent recharge dates from 1963 to 1975 in the shallow wells, and no recently recharged water in the deep 17MOS8193, and so was generally in line with the 14C and Tritium results, although some contamination had happened. SF6 concentrations exceeded possible concentrations considering other results, most likely due to underground generation, and the method was dismissed. By trace element composition, all samples from the deep 17MOS8139 are distinct from other samples and saw slight dilution in concentrations of most elements in the span of the test pumping. Other samples are more mixed and difficult to interpret, but some trends and connections are visible, such as the higher contents in wells with screens below the bedrock surface than those with screens above the bedrock surface, and the exceptionally high contents of many elements in B-13-17HYD004. Overall, the study did benefit from the large array of methods, showing no interaction between the deep bedrock groundwaters and shallow groundwaters or surface waters. The evaporated signal from the Viiankiaapa was clearly visible in the samples close to the River Kitinen.
  • Redmond Roche, Benjamin Heikki (Helsingin yliopisto, 2019)
    Significant changes in sea-ice variability have occurred in the northern North Atlantic since the last deglaciation, resulting in global scale shifts in climate. By inferring the dynamic changes of palaeo seaice to past changes in climate, it is possible to predict future changes in response to anthropogenic climate change. Diatoms allow for detailed reconstructions of palaeoceanographic and sea-ice conditions, both qualitatively, using information of species ecologies and quantitatively, via a transfer function based upon diatom species optima and tolerances of the variable to be reconstructed. Three diatom species comprising a large portion of the training set are proxies for the presence of sea ice: Fragilariopsis oceanica, Fragilariopsis reginae-jahniae and Fossula arctica, have currently been grouped into one species – F. oceanica – in the large diatom training set of the northern North Atlantic region. The clustering of the species may result in an imprecise reconstruction of sea ice that does not take into account all the available ecological information. The proportions of the three species were recounted from the original surface sediment slides alongside the additional chrysophyte cyst Archaeomonas sp. and statistically analysed using Canoco and the R software package eHOF. A core from Kangerlussuaq Trough comprising the Late Holocene (~690–1498 Common Era) was also recounted and analysed using C2. The separated diatom species and chrysophyte cyst Archaeomonas sp. exhibited different relationships to both sea-ice concentration (aSIC) and sea surface temperature (aSST). The separated F. oceanica is a ‘cold-mixed’ water species occurring at cold aSST and both low and high aSIC. High abundances occur in the marginal ice zone (MIZ) where surficial meltwater is high during the spring bloom, with additional inputs from glacial meltwaters nearshore. F. reginae-jahniae is a sea-ice associated species related to cold aSST and high aSIC. High abundances occur in the low salinity Arctic Water dominated MIZ which experiences significant aSIC. F. arctica is a sea-ice associated species related to cold aSST and high aSIC. High abundances occur in the low salinity Arctic Water dominated MIZ which experiences high aSIC, particularly in polynya conditions. F. arctica can be considered a characteristic polynya species at high abundances. Archaeomonas sp. is a ‘cold-mixed’ water species related to both cold and relatively warm aSST and low and high aSIC. High abundances occur in both relatively warm ice-free Atlantic Water and also in cold high aSIC Arctic Water conditions rendering it a more complex indicator for aSST or aSIC proxy. However, the aversion to MIZ conditions indicates that Archaeomonas sp. is associated with a relatively saline unstratified water column. This is the first time that the distribution and ecology of Archaeomonas sp. has been presented. As such, the ecology described here can be used in future studies. The separation of the three diatom species is crucial for the ecological interpretation of downcore assemblage changes. It is also crucial for the application of transfer functions in order to have greater precision in reconstructing aSIC and assessing the influence of Arctic Water or Atlantic Water, even at low abundances.
  • Orozco Ramírez, Lilia Estefanía (Helsingin yliopisto, 2019)
    The European Water Framework Directive aims at restoring all water bodies in good ecological conditions by the year 2023. For this aim, understanding the responses of these ecosystems to current and future pressures is a requisite. Lakes Hältingträsk and Storträsk are located in Östersundom, a latent developing suburban area in eastern Helsinki. Alterations to the catchment in Hältingträsk as a consequence of urbanization will likely change the conditions of the lake. Storträsk, part of Sipoonkorpi nature reserve is primarily influenced by recreational activities. Ecological status of both lakes is likely to alter under the ongoing urban development. For this reason, the reference conditions of Hältingträsk and the resilience of both lakes to human stressors must be assessed. A long term record from Hältingträsk, with special focus on the most recent section, as well as a short core from Storträsk targeting the most recent events, are analyzed for different palaeobiological and geochemical proxies. The sequence from Hältingträsk is evaluated with diatom assemblages, trace metal analyses, lithological description of sediments through loss-on-ignition and inferred chlorophyll a. For Storträsk, a high-resolution study of diatom communities and photosynthetic pigments is performed. Both sequences are framed with an age-depth model based on radiogenic dating techniques. In addition, the results are analyzed with statistical tools and fossil diatom data is used to reconstruct lake water pH. The results describe the evolution of Hältingträsk through the mid-Holocene until recent times; the diatom assemblages indicates the area was part of Ancylus Lake and, later of Litorina Sea, and that it was isolated from the Baltic Basin at 6500 cal BP. This is supported by the high concentrations of Fe and Mn, showing the presence of metallic nodules common in marine environments. The change in sediments and the predominance of fragilarioid diatoms, display the succession of the lake (from gloe to flada). Afterwards, the ontogeny of the lake and the development of surrounding peat bog can be tracked with changes in the diatom community and decrease in heavy metals concentrations. The reconstructed pH reveals that Hältingträsk is a naturally acidic lake. Furthermore, signals of agricultural activities and industrialization are recorded in the area, as well as their development, is recorded through shifts in the diatom community and the oscillation of trace metals of both local (Cu, Ni and V) and long (Pb, Zn and Cd) transport. Finally, climatic anomalies such as the Little Ice Age and current climate warming are imprinted in the diatom assemblages and the photosynthetic pigments. The high resolution of subsampling from Storträsk displayed little variation. The faint changes could be attributed to CaCO3 treatment, fish introduction or recent climate warming. However, discern the influence of each of these stressors was not possible.
  • Uusikorpi, Juuso (Helsingin yliopisto, 2020)
    The geochemical regolith data gathered from Dzhumba, a gold prospect in eastern Kazakhstan, was analyzed using factor analysis and then integrated into ArcGIS as spatial data. Principal axis factoring method was used for factor extraction combined with varimax orthogonal rotation and Kaiser normalization. Five clear factors were extracted from the data set of 47 elements in 3942 regolith samples. Kriging interpolation was used to generate spatial data surfaces from factor scores. The generated factors are composed of the geochemical associations in the raw data, and represent the underlying geological processes and formations of the area. The fourth factor generated represents gold mineralization with As, Sb, Au, Zr, Sc, Mn, Mo, Cu, K and Ni being the elements that are positively loaded onto factor 4. Therefore, single element maps of these elements have been produced alongside the factor maps in order to examine factor 4 more intensely. Also maps about structural geology and alteration in the Dzhumba project area have been produced in order to give better understanding of the factor maps. The data suggests that the deposit type is an orogenic gold deposit. Other factors created interesting results as well, and they gave information about the different geological units of the area. Factor 1 represents granitic rocks by their feldspar and trace element content, factor 2 represents black shales with possible mafic rock constituents, factor 3 represents a sulfide rich mafic mineral group or graphitic rocks that are most likely black shales and factor 5 possibly represents calcite alteration. Factor 4 is the main interest of this study. The most intense loadings for factor 4 are in Brigadnoe, Svistun and Dzhumba with a small peak in Belyi. Single element map for gold mostly corresponds to factor 4 for Svistun and Dzhumba, but Brigadnoe is represented with a small peak. However, gold has a major presence in Fedor-Ivanovskoe, which is absent from factor 4. Further exploration in Fedor-Ivanovskoe could be performed in order to clarify if this is due to an unrelated gold-only deposit or some other event. Possible future exploration in the area could benefit from factor 4 results, using As and Sb, or a combination of As, Sb, Zr, Sc, Mn, Mo, Cu, K and Ni as pathfinders for possible gold occurrences.
  • Ylä-Mella, Lotta (Helsingin yliopisto, 2020)
    Terrestrial cosmogenic nuclides can be used to date glacial events. The nuclides are formed when cosmic rays interact with atoms in rocks. When the surface is exposed to the rays, the number of produced nuclides increases. Shielding, like glaciation, can prevent production. Nuclide concentration decreases with depth because the bedrock attenuates the rays. The northern hemisphere has experienced several glaciations, but typically only the latest one can be directly observed. The aim of the study was to determine if these nuclides, produced by cosmic rays, can be used to detect glaciations before the previous one by using a forward and an inverse model. The forward model predicted the nuclide concentration with depth based on a glacial history. The longer the exposure duration was, the higher was the number of nuclides in the rock. In the model, it was possible to use three isotopes. Be-10, C-14 and Al-26. The forward model was used to produce synthetic samples, which were then used in the inverse model. The purpose of the inverse model was to test which kind of glacial histories produce similar nuclide concentrations than what the sample had. The inverse model produced a concentration curve which was compared with the concentration of the samples. The misfit of the inverse solution was defined with an “acceptance box”. The box was formed from the thickness of the sample and the corresponding concentrations. If the curve intersected with the box, the solution was accepted. Small misfit values were gained if the curve was close to the sample. The idea was to find concentration curves which have as similar values as the samples. The inverse model was used in several situations, where the number of limitations was varied. If the timing of the last deglaciation and amount of erosion were known, the second last deglaciation was found relatively well. With looser constraints, it was nearly impossible to detect the past glaciations unless a depth profile was used in the sampling. The depth profile provided a tool to estimate the amount of erosion and the total exposure duration using only one isotope.
  • Sandström, Joonas (Helsingin yliopisto, 2021)
    Aijala-Metsämonttu volcanogenic massive sulphide ore deposit belongs to Orijärvi regional volcanogenic massive sulphide mineralisation, localised within the schist zone southwestern Finland. Aijala-Orijärvi zone is an island-arc structure formed during the Paleoproterozoic (1895-1891 Ma). The mining operation in Aijala took place in 1949–1958 and Metsämonttu in 1952–1958 and 1964–1974. The Aijala and Metsämonttu deposits were 1 km apart. The main ore types were massive vein-like pyrite, sphalerite, pyrrhotite, chalcopyrite, and galena. The purpose of this thesis was to produce modern geological 3D models of the Aijala and Metsämonttu volcanogenic massive sulphide ore deposits and numerical grade models of the utilised minerals (copper, lead, zinc, silver, and gold) using historical material and to interpret the occurrences and emplacements of precious metals and base metals. In addition, compare the accuracy of the 3D models with digitised historical material. Geological 3D and numerical grade models were created using implicit modelling. Historical data used in this thesis consist of 266 drill holes from Aijala and 274 drill holes from Metsämonttu. Also, 61 mine tunnel maps and 47 cross-sections were used to create the geological models. The Aijala-Metsämonttu volcanogenic massive sulphide ore deposits are in the same stratigraphic zone between the footwall quartz-feldspar-porphyry and hanging wall amphibolite. Sulphide lenses of both deposits are vertically on the south side of the footwall and hanging wall contact. The main host rocks to sulphide ores are skarn and cordierite-gneiss. Several local faults intersect the deposits. The most significant faults displaced overlying blocks to the south in Aijala and to the north in Metsämonttu. The Aijala-Metsämonttu deposit belongs to the Zn-Pb-Cu group. The occurrence style and concentrations of metals vary between deposits. Copper ore is present in Aijala but absent in Metsämonttu, whilst zinc-lead ore is present in Metsämonttu but absent in Aijala. Precious metals occur in both deposits with a companion of base metals. The Metsämonttu deposit is rich in precious metals compared to the Aijala deposit, and the presence of high content of precious metals correlates with the incidence of lead ore. Precious metals concentrations increase from east to west and deeper in Metsämonttu.
  • Jokela, Eetu (Helsingin yliopisto, 2020)
    The Sukseton area is located in the northern part of Kittilä municipality, Central Lapland Greenstone Belt, approximately 15 km N from Suurikuusikko gold mine and 5 km NW from Iso-Kuotko orogenic gold deposit, between several large crustal scale thrust and shear zones. This area is a mix of different volcanic formations of Kittilä suite, felsic intrusion of Vuotso Complex and Paleoproterozoic intrusive rocks in the north. In addition to this, several porphyry dykes cut the Kittilä suite volcanic rocks around the area. Exploration work in this area started in the 1980’s when Outokumpu Oy found two minor gold and gold-copper mineralizations. In 2017, Agnico Eagle Finland Oy continued exploration in this area, intending to define the regional geology and the extent of the mineralizations. As a result of this exploration work, this study investigates more closely the regional geology, geochemistry, metamorphism and structural geology of the Sukseton area, as well as the geochronology of associated porphyry dykes. To understand and define the geology of the area, the following methods were used: geological bedrock and exploration trench mapping, interpretation of drill core loggings and several geophysical surveys, optical studies of polished thin sections and U–Pb dating a porphyry dyke sample. The metamorphic conditions of the area were studied through thorough petrological studies. In addition, an extensive geochemical and geotectonic classification of the rocks in the area was conducted. The Sukseton area composes mainly of different tholeiitic basalts and pyroclastic rocks with minor sulphide rich graphitic volcanic sediment and chert sections. Based on this study, these volcanic rocks originate from island arcs and mid-ocean ridges. With the help of geophysical surveys and field measurements, a couple of large fold structures were identified from the eastern part of the study area as well as a large shear zone in the middle of the area striking NE–SW. Porphyry dykes cut the volcanic rocks all around the area giving the minimum age of 1940±18 Ma for the volcanic rocks. Composition of porphyry dykes vary from rhyolites to basalt and they have similar geochemical characteristics with Nyssäkoski type felsic veins. The peak metamorphic conditions in the area represent high-P amphibolite facies metamorphism. Also, hydrothermal alteration is common in Sukseton and it can be metamorphic and magmatic in origin.
  • Georgi, Jaakko (Helsingin yliopisto, 2019)
    This study consists of a comprehensive characterization of the geology, geochemistry, alteration, and mineralization at the Ronaldo prospect as well as an evaluation of its ore potential. Previous mapping campaigns of the prospect, which lies in the Central Andes in Peru at an elevation of 4300 metres, have identified intrusions overlain by a volcanic package. The intrusions are crosscut by silicified ridges that host epithermal mineralization. Satellite imagery reveals that the topographically elevated areas exhibit strongly altered rocks identified as an advanced argillic-altered lithocap. The methods used to define and better understand the geology and the evolution of the hydrothermal system included reconnaissance field mapping, whole-rock geochemistry, short-wave infrared spectroscopy, petrography, and geochronology. Previous studies have shown that only high-sulfidation epithermal mineralization can be spatially and temporally linked to porphyry Cu mineralization, and therefore this study investigates – among other aspects – what type of epithermal mineralization is present at Ronaldo in order to evaluate the potential for concealed at-depth porphyry Cu mineralization. Two separate lower Miocene intrusive units were identified, a porphyritic diorite and a porphyritic granodiorite, whose average age difference is 1.79 Ma. The intrusive units display intermediate argillic alteration. The overlying extrusive units are Sacsaquero Formation basaltic andesites and ignimbrites that are either unaltered or display propylitic alteration. The basaltic andesite roof pendants observed at Ronaldo indicate that the tops of the intrusions are preserved. At high elevations, advanced argillic alteration composed of pyrophyllite, kaolinite, and dumortierite was observed. This area is the remnant, deeper zone of a larger lithocap. The steeply dipping silicified ridges that display sericitic alteration were inferred to be the root zone of this lithocap. Elevated values of trace elements such as Te, Bi, As, and Sb suggest that the Ronaldo prospect is mostly situated in a sericitic alteration zone related to a porphyry-like magmatic-hydrothermal source located at greater depth. Isolated magnetite aggregates were observed in magmatic-hydrothermal breccia, which indicates that the sericitic alteration may have overprinted potassic alteration. A few intermediate-sulfidation epithermal veins and porphyry-related veins, including a banded molybdenite quartz vein, were observed in the creek near the major fault. At Ronaldo, high silica content and sericitic alteration correlate well with elevated concentrations of Ag, Au, and Mo, whereas Cu concentration does not correlate well with any alteration type or with silica content. Quartz veinlets in the silicified ridges that host abundant Ag and Au mineralization were interpreted to have formed at a slightly later stage and to be unrelated to the magmatic-hydrothermal system. This mineralization was interpreted to be low-sulfidation epithermal in origin due to features such as abundant adularia, lattice-textured bladed calcite replaced by quartz, crustiform banding, banded quartz-chalcedony veins, druse-lined cavities, and high Ag/Au ratios. In conclusion, the Ronaldo prospect comprises a hydrothermal system in which the deep, root zone of an advanced argillic lithocap is exposed. The exploration potential for low-sulfidation epithermal mineralization in the silicified ridges is rather significant, whereas the potential for porphyry Cu mineralization is minor due to the lack of appreciable Cu and Mo mineralization, typically shallow-depth porphyry-related hydrothermal alteration, and the lack of high-sulfidation epithermal mineralization.
  • Juvonen, Katriina (Helsingin yliopisto, 2021)
    Etelä-Pohjanmaalla Kurikassa maaperän rakennettavuusominaisuudet ovat hankalat maaperän mittavien hienoaineskerrostumien vuoksi. Näiden kerrostumien alueellista jakautumista ei tiedetä, joten tämän työn tarkoituksena on toteuttaa maaperästä geoteknisiin pohjatutkimuksiin perustuva alueellinen 3D-malli Kurikan kaupungin rakennuslupaa-arkiston pohjatutkimusaineistoja käyttäen. Pohjatutkimukset koostuvat yksittäisiin rakennuskohteisiin toteutetuista maaperäkairauksista. Aineistona käytettäviä tutkimuskohteita on yhteensä kymmenen ja kairauksia 3D-mallissa on käytössä 112. Pohjatutkimusaineistoista digitoitiin kohde ja kairaus kerrallaan maalajitieto sekä kairauksen kuormitusominaisuudet. Digitointiin käytettiin suomalaisen 3D-Systemsin 3D-Win –ohjelmistoa. 3D-malli toteutettiin Leapfrog Geo® -ohjelmistolla. Mallin ensimmäisessä vaiheessa maaperä jaettiin kahdeksaan yksikköön. Lopullisessa yksinkertaistetussa mallissa maaperän hienoainesyksiköt yhdistettiin yhdeksi yksiköksi. Saatuja malleja verrattiin alueelta olevaan tyyppileikkaukseen. Malleilla arvioidaan millä aineiston resoluutiolla saadaan mallille paras ennustusvoima. 3D-mallien toteutus onnistui. Mallin mukaan alueella on kahdeksan maalajiyksikköä (vanhimmasta nuorimpaan): moreenit, hiekat, siltit, savet, liejusavet, siltit 2, savet 2 sekä pinnassa humus- ja täyttömaat. Useilla mallin yksiköistä (siltit, savet ja liejusavet) on samankaltaiset geotekniset ominaisuudet, joten ne yhdistettiin yhdeksi hienoainesyksiköksi. Yksinkertaistetun mallin yksiköitä verrattiin alueelta olevaan tyyppileikkaukseen. Tyyppileikkauksen sedimenttisarja ja mallin hienoainesyksikkö vastaavat hyvin toisiaan. Tämän työn tulosten perusteella geoteknisiin pohjatutkimuksiin perustuvassa maaperän 3D-mallinnuksessa hienoainesyksiköiden osalta yksinkertaistettu malli on ennustettavuuden kannalta luotettavampi kuin kompleksinen malli.
  • Turtiainen, Harri (Helsingin yliopisto, 2020)
    A promising Cu-Ni-PGE containing sulphide ore deposit was discovered in 2009 by Anglo American and since the company has continued studies aiming towards utilisation of the deposit. The discovered deposit lies underneath a Natura 2000 protected mire complex, Viiankiaapa, in Sodankylä municipality in Finnish Lapland. The research and exploration activities in the area are performed with mitigation and preventing actions in order to minimize the deterioration impact to the delicate ecosystem. The more detailed understanding of the hydrogeochemistry of the mire environment in its current state can assist: in monitoring, mitigating and preventing of potential environmental effects due to future mining operations as well as planning the monitoring program. Hydrogeochemical studies, consisting of water and peat sampling at eight sampling points, were carried out along a 1.6 km long study line. Water samples were collected from the surface of the mire as well as within the peat layer and the bottom of the peat layer. Water samples were collected using a mini-piezometer. The analyses for the water samples involved: major components, trace elements and δ18O & δ2H. Groundwater influence in the different sampling points as well as different sections of the peat was investigated using the mentioned chemical and isotopic properties. Peat sampling focused on finding samples which would have different hydraulic properties in order to find the influence of peat in the hydrology in the mire. Hydraulic conductivity of peat samples was determined using rigid wall permeameter test setup. The chemical and physical methods were supplemented by a ground penetrating radar survey completed with 30 and 100 MHz antennas. Studies of peat showed that the hydraulic conductivity varies substantially even inside the rather small study area. Widely recognized correlation between hydraulic conductivity and depth was not observed statistically, but the sampling sites individually show a clear connection with depth and hydraulic conductivity. The influence of the hydraulic properties of peat on to the flow of water in the mire was observed to be significant. In cases where the hydraulic conductivity of peat was very low, water flow may be prevented altogether. This was confirmed with the use of chemical analyses. With higher hydraulic conductivity, groundwater influence was seen more or less throughout the peat profile.
  • Rantanen, Aleksi (Helsingin yliopisto, 2021)
    Vulkaanisten kaarten magmaattinen aktiivisuus nostaa maankuoren lämpötilaa ja laskee sen kestävyyttä, mutta näiden muutosten suuruutta tai muutosten erinäisiä tekijöitä, kuten latenttilämpöä, sulamisesta aiheutunutta viskositeetin laskua sekä intruusioiden koostumusta, lämpötilaa ja sulan määrää ei ole laajemmilta osin tutkittu. Pro gradu tutkielman tarkoitus on kvantifioida näitä kuoressa tapahtuvia muutoksia sekä tutkia erinäisten tekijöiden vaikutusta kallioperän kestävyyteen, kuten sitä kuinka kestävyys muuttuu lämpötilan nousun seurauksena kiinteässä tilassa verrattuna siihen miten se muuttuu kiven sulaessa. Näitä näkökulmia tutkitaan mallilla, joka perustuu kaksiulotteiseen lämpöyhtälöön, joka ratkaistaan differenssimenetelmällä. Kuoren kestävyyden muutoksia lasketaan sarjalla yksiulotteisia kuoren kestävyyskriteerimalleja. Kivien sulamislämpötilat saadaan termodynaamisella ohjelmalla, joka laskee sulafraktiot eri paine ja lämpötilaolosuhteissa ja näitä sulia käytetään hyväksi mallissa, joka laskee efektiivisen viskositeetin osittain sulaneelle kivelle. Kuoren kestävyyttä ja lämpötilan muutoksia tarkastellaan tekemällä useampia simulaatioita, jotka jäljittelevät magmaattisen kaaren vulkanismia. Maankuoren integroitu kestävyys laskee magmakammioiden läheisyydessä jo muutaman miljoonan vuoden kuluttua ~80 % eikä tämä arvo muutu huomattavasti jatkuvan magmaattisen aktiivisuuden seurauksena. Magmakammioita ympäröivä maankuori kuitenkin jatkaa heikentymistä koko magmaattisen aktiivisuuden ajan (10 Ma) eikä tämä ei ole ainoastaan seurausta hitaasta lämmönjohtumisesta. Magmaattisen aktiivisuuden päätyttyä maankuori jäähtyy ja kiteytyy, jolloin intruusioiden mekaaniset ominaisuudet saattavat joko heikentää tai kestävöittää kallioperää suhteessa maankuoren alkuperäiseen kestävyyteen riippuen intruusioiden ja niitä ympäröivän kiven mekaanisista ominaisuuksista. Mafiset intruusion kykenevät kestävöittämään kallioperää helpommin syvemmällä, missä kuori alun perin deformoitui plastisesti, kun taas felsiset intruusiot kykenevät mekaanisesti heikentämään maankuorta matalammilla syvyyksillä. Pitkällä aikavälillä intrudoituvan magman lämpötila on vähemmän tärkeä tekijä kuoren kestävyydelle, kuin intruusioiden mekaaniset ominaisuudet. Kiven sulamisella ei näytä olevan huomattavaa vaikutusta kuoren kestävyyden muutoksiin. Suurin osa simulaatioista osoittaa, että kuoren integroitu kestävyys on pudonnut jo yli 99.9 % lämpötilan nousun seurauksena ennen kuin kuori alkaa sulamaan. Jopa äärimmäisimmissä skenaarioissa kuoren sulamisesta aiheutuva integroidun kestävyyden lasku pysyy pääsääntöisesti 0.5 % alapuolella. Mitä enemmän magmassa on sulaa, sitä suurempi vaikutus latenttilämmöllä on kuoren lämpötiloihin. Magmaattisen aktiivisuude aikana intrudoituvalla magmalla minkä sulamäärä on 10–100 %, latenttilämmön osuus lämpötilan noususta on 12–34 %. Latenttilämpö vaikuttaa enemmän kuoren kestävyyteen magmakammioiden läheisyydessä ja laskee kuoren kestävyyttä enemmän magmaattisen aktiivisuuden päätyttyä. Maximissaan latenttilämmöstä aiheutunut kuoren integroidun kestävyyden lasku on 10–30 % magmakammioiden läheisyydessä ja keskiarvo on 5–17.5 % 50 km säteellä magmakammioista, riippuen magman alkuperäisestä sulan määrästä. Tektoniikan kannalta on tärkeää ymmärtää miten magmaattinen aktiivisuus vaikuttaa maankuoren kestävyyteen. Maankuori on heikoimmillaan suoraan magmakammioiden läheisyydessä magmaattisen aktiivisuuden aikana, joka saattaa aiheuttaa paikallisia muutoksia kuoren deformaatiossa ja hiertovyöhykkeiden muodostumisessa, mutta pitkällä aikavälillä intruusioiden koostumus ja niiden mekaaniset ominaisuudet saattavat vaikuttaa huomattavasti kuoren kestävyyteen. Koska kuoren sulamisesta aiheutunut viskositeetin lasku ei ole huomattava tekijä kuoren kestävyydelle, niin muut magmaattiseen aktiivisuuteen ja vulkanismiin liittyvät tekijät ovat todennäköisesti tärkeämmässä osassa, kuten kiven sulamiseen liittyvä tiheyden lasku ja tilavuuden kasvu, joka taas johtaa uusiin maankuoreen syntyviin jännityskenttiin, kallioperän murrosten syntymiseen sekä magman liikkumiseen.
  • Laurila, Minna (Helsingin yliopisto, 2020)
    Artificial groundwater is produced in Jäniksenlinna water treatment facility in Tuusula by infiltrating surface water from the lake Päijänne to the Jäniksenlinna aquifer. The geochemical properties of the artificial groundwater vary and challenge the water purification process in the Jäniksenlinna facility. The objective of the study was to solve the geochemical quality of the water in different locations inside the aquifer area and in the different steps of the water purification process and to solve the changes in the geochemistry of the water caused by the seasonal changes. The study was put into effect by collecting 20 water samples, 16 of which were from different locations inside the aquifer area and 4 of which were from the different steps of the water purification process in the water plant. The samples were collected during the spring 2018 and repeated during the summer 2018. Each water sample was analyzed for major ions by ion chromatography, trace elements by ICP-MS method and stable isotopes of hydrogen and oxygen with the help of Picarro device. Additionally, each sample was analyzed in the field for electric conductivity, pH and temperature and in laboratory for alkalinity, pH and electric conductivity. The results from the spring and from the summer were handled separately since they differed with statistically significant levels from each other. The results were treated with statistical methods and visualized with tables, graphs, photos from the sampling points and maps. The results show that season changed the proportion of the natural and the artificial groundwater in the sampling points. However the season had no effect on the existence of the artificial groundwater in the sampling points. The proportion of the artificial groundwater was highest while the groundwater level was low, that is during the summer. The sampling points were selected with different distances to the infiltration area. However, the amount of infiltrated water did not decrease with the growing distance to the infiltration area, since the geological structures of the aquifer define the water flow inside the aquifer. The amount of artificial groundwater was lower in one sampling point closer to the infiltration area than in two sampling points further away the infiltration area. The water purification process removes the excess iron and manganese from the artificial groundwater and produces water which fulfills the standards set for the drinking water. The amount of iron and manganese in the drinking water might get even lower by conducting the water from the well 12 to the iron and manganese removal. The study covered the spring and the summer seasons, but in order to study the whole annual picture, the sampling should cover the autumn and the winter seasons as well. Flow modelling could give better picture of the formation of the artificial groundwater in Jäniksenlinna.
  • Silvennoinen, Sonja (Helsingin yliopisto, 2021)
    Itämeren pohja on ollut vähähappinen tai kokonaan hapeton useita kertoja viimeisten 8000 vuoden aikana. Holoseenin lämpömaksimin aikana, Litorinameren suojaisessa mataloituvassa lahdessa nykyisen Kurikan alueelle on kerrostunut aikaresoluutioltaan poikkeuksellisen hienosyinen sedimenttisarja, joka kertoo pohjan happitilanteen muutoksista. Ajallisesti sedimenttisarja kattaa paikallisen deglasiaation, Ancylusjärvivaiheen ja Litorinameren kehityksen paikalliseen kuroutumiseen asti, ajoittuen jaksolle n. 10 800–4 500. Magneettiset mineraalit ovat herkkiä ympäristön prokseja ja niiden kerrostumisen jälkeiseen diageneesiin liittyy joko detritaalisten magneettisten mineraalien muuttuminen tai uusien magneettisten mineraalien syntyminen. Koska muutoksia tapahtuu sekä hapettavissa että pelkistävissä ympäristöissä, voidaan magneettisia mineraaleja käyttää tutkittaessa sedimenttien diageneettisiä prosesseja ja ympäristöjä. Esimerkiksi greigiitti on rautasulfidi, jonka esiintyminen indikoi hapetonta ympäristöä. Greigiittiä voi syntyä diageneesissa sulfaatin pelkistymisen tai metaanin anaerobisen hapettumisen seurauksena. Lisäksi magnetotaktiset bakteerit tuottavat greigiittiä magnetosomeihinsa. Ympäristömagneettiset ominaisuudet kertovat greigiitin synty-ympäristön redox-olosuhteista. Huhtikuussa 2019 kerätystä 40 metriä pitkästä sedimenttisarjasta määritettiin sedimentin litologia, magneettinen suskeptilibeetti, orgaanisen aineksen pitoisuus sekä raekoko. Tulosten perusteella sedimenttisarja jaettiin viiteen yksikköön (KY15-1–KY15-5). Yksiköistä KY15-2, KY15-3 ja KY15-4 selvitettiin ympäristömagneettiset ominaisuudet neljästä eri vyöhykkeestä. Suskeptibiliteettiaineiston toistotarkkuus varmennettiin korkeamman resoluution mittauksin ja ympäristömagneettisia tuloksia verrattiin suskeptibiliteettimittauksiin. Ympäristömagneettisten tulosten vertailu suskeptibliteetin arvoihin osoittaa, että suskeptibiliteettia voidaan käyttää ympäristömagneettisten ominaisuuksien rekonstruoimiseen Kurikan sedimenttisarjan sedimenttiyksiköissä, joissa sedimentaatio on verrattain tasaista eikä suuria raekokomuutoksia esiinny. Litorinamerivaiheen sedimentistä havaittiin single-domain (SD) kokoista (200-1000 nm) autigeenistä greigiittiä Kurikan sedimenttisarjassa ja ympäristömagneettiset tulokset indikoivat sen alkuperäksi sulfidista ympäristöä. Tutkimuskohteen sedimenttisarja eroaa muista Itämerestä tutkituista sedimenttisarjoista erityisesti Ancylusjärven sedimenttien ympäristömagneettisilta tuloksiltaan. Poiketen syvänteistä kerätyistä sedimenttisarjoista, ei Ancylusjärven savista tunnistettu greigiittiä, eikä sedimentissä nähty selviä sulfidikerroksia. Litologisten ja ympäristömagneettisten tulosten perusteella greigiitin (autigeeninen) syntymekanismi Kurikan sedimenttisarjassa on erilainen, kuin Itämeressä aiemmin havaitulla greigiittillä (magnetotaktisten bakteerien synnyttämä). Tutkimuksen tulokset viittaavat siihen, että greigiitin syntytavat voivat olla jopa altaan samoissa sedimenteissä toisistaan poikkeavat, ja että sedimentaatioympäristö vaikuttaa vahvasti greigiitin syntymiseen ja sen säilymiseen sedimentissä. Suskeptibiliteetin perusteella hypoksia on ollut Litorinameren aikana mataloituvassa merenlahdessa yleistä, mutta ei jatkuvaa. Isomman mittakaavan trendit hapettomuuden vaihtelussa ovat olleet perenniaalisia oletetulla aikaresoluutiolla, mutta aineisto ei sulje pois hapettomuuden kausittaisuutta. Litorinameren ajalta voidaan erottaa ainakin kaksi pitempiaikaista, muutamia satoja vuosia jatkuvaa, hapetonta tai vähähappista kautta. Greigiitin määrä kuitenkin vaihtelee jaksojen aikana, heijastaen vaihtelua pohjaolosuhteissa. Hypoksisten kausien välillä (~6500–7000 cal BP) on viitteitä lyhytaikaisista hapellisista jaksoista. Kyseinen ajanjakso on yhdistetty kirjallisuudessa korkeampiin suolatasoihin Itämeren altaassa, suhteellisen merenpinnan korkeampiin tasoihin sekä hapellisten olosuhteiden yleistymiseen.
  • Kilpeläinen, Visa (Helsingin yliopisto, 2021)
    Järven kehityksen tunteminen auttaa rekonstruktioimaan ihmistoiminnan ja luonnollisten muutosten aiheuttamia tapahtumia järven kehityksessä. Näitä tapahtumia voidaan päätellä pohjasedimenttikooreista saatavien tietojen avulla. Tämä tutkimus tutkii pienen vuoristojärven kehitystä viimeisen 800 vuoden aikana. Tutkimuksen tavoitteena on selvittää sedimentaatiossa tapahtuneita poikkeamia sekä ihmistoiminnan vaikutusta niihin. Kohdejärvi Laka sijaitsee Tšekin lounaisosassa Sumavan luonnonsuojelualueella. Laka-järvi on pituudeltaan 300 metriä ja leveydeltään 100 metriä. Järven alueella vallitsee vuoristoilmasto, ja järvi on jäässä keskimäärin 4–5 kuukautta vuoden aikana. Järveä ympäröivä metsäalue toimi teollisesta toiminnasta aiheutuneiden rikki- ja typpipäästöjen nieluna 1950-luvulta 1980-luvun loppuun, mikä aiheutti happamoitumista. Työn aineisto on PEDECO-projektin yhteydessä tuotettua, jonka tekijä on saanut ohjaajaltaan valmiina käyttöönsä. Tutkimuksessa käytetty aineisto on tuotettu venäläisellä suokairalla otetusta sedimenttikoorista ja Limnos-nostimella otetusta pintasedimenttikoorista tehdyt analyysit. Tutkimuksessa käytetyt menetelmät ovat radiohiiliajoitus yli 70 vuotta vanhojen sedimenttien ajoittamiseen, 210Pb-ajoitus alle 70 vuotta vanhojen sedimenttien ajoittamiseen, raekokoanalyysi lajitteiden osuuksien määrittämiseen, infrapunan lähellä olevien aallonpituuksien spektrometria orgaanisen aineksen, mineraaliaineksen ja biogeenisen silikaatin osuuksien määrittämiseen, röntgensädefluoresenssi alkuainepitoisuuksien määrittämiseen, siitepölyanalyysi ja muiden palynomorfien analyysi kasvien ja muiden itiöperäisten eliöiden esiintyvyyden määrittämiseen. Lisäksi aineistoista tehtiin Pearsonin korrelaatio ja pääkomponenttianalyysi, joiden avulla määritettiin eri muuttujien suhteita toisiinsa. Tuloksista näkyy kolme erilaista aikakautta järven kehityksessä: luonnontilainen 1200-luvulta 1600-luvulle, vähäistä ihmistoiminnan vaikutusta 1600-luvulta 1850-luvulle ja huomattavaa ihmistoiminnan vaikutusta 1850- luvulta nykyaikaan. Luonnollisista muutoksista järven kehitykseen vaikutti eniten sademäärien muutokset. Myös paikalliset tuulen ja hyönteisten aiheuttamat metsätuhot vaikuttivat järven kehitykseen. Ihmistoiminnan suurimmat vaikutukset aiheutuivat järven patoamisesta, sekä veden ajoittaisista juoksutuksista padon läpi. Kun veden juoksutus padon läpi lopetettiin 1920-luvulla, järven pinta nousi ja sen pinta-ala kasvoi. Veden alle jääneestä maaperästä liukeni veteen runsaasti eri alkuaineita, mikä aiheutti monien alkuaineiden kohdalla suurimmat pitoisuudet koko tutkimuksen ajanjakson aikana. Lisäksi järveen päätyi jonkin verran teollisuuden aiheuttamia päästöjä kaukokulkeumana.
  • Clergeaud, Joona (Helsingin yliopisto, 2020)
    Pro gradu -tutkielma on osa Vantaanjoen ja Helsingin seudun vesiensuojeluyhdistys ry:n hanketta, jossa tutkitaan maanläjitystoiminnan tyypillisiä pinta- ja pohjavesivaikutuksia sekä havainnoidaan lohikalojen lisääntymisalueille tapahtuvia haittoja Vantaanjoen valuma-alueella. Maanläjitystoiminnan moninaisen luonteen vuoksi, toiminnan laajuudesta ja sen vaikutuksista ei ole olemassa luotettavaa tutkimuksiin perustuvaa tietoa. Tutkielmassa selvitettiin millaisia vaikutuksia pilaantumattomien ylijäämämaiden välivarastoinnilla ja läjityksellä on lähiympäristön pohja- ja pintaveden laatuun. Pilaantumattomien ylijäämämaiden osalta tutkimuksia tehtiin kolmessa eri kohteessa Vantaanjoen valuma-alueella. Tutkielma keskittyi valuma-alueella sijaitsevien ympäristöluvanvaraisten- ja muilla luvilla toimivien maanläjitysalueiden velvoitetarkkailutulosten kokoamiseen, tarkasteluun ja paikkatietoanalyysin kehittämiseen. Näiden kriteerien avulla voidaan arvioida läjitysalueiden vesille aiheuttamia riskejä. Tutkimukseen kuului lisäksi pohjaveden purkautumispaikkojen ja luonnonpurojen kartoitusta, vedenlaadun kenttämittauksia ja vesinäytteenottoa. Esiselvitysten perusteella odotettiin maanläjitysalueiden läheisyydessä olevissa pinta- ja pohjavesissä olevan tausta-arvoista kohonneita raskasmetalleja, talousveden laatuvaatimuksista poikkeavia pH-arvoja sekä sähkönjohtavuuden muutoksia. Tulosten perusteella pilaantumattomilla ylijäämämailla on lieviä haitallisia vaikutuksia niin pinta- ja kuin pohjaveden laadullisiin tekijöihin. Pinta- ja pohjavesissä todettiin alueittain kohonneita pitoisuuksia ja arvoja muun muassa sulfaatilla, sähkönjohtavuudella, liukoisessa muodossa raudalla, mangaanilla, uraanilla, rikillä sekä sinkillä. Tutkielman tulokset auttavat arvioimaan läjitysalueiden haitta-ainekuormituksia vesiympäristöön ja suunnittelemaan riskienhallintatoimenpiteitä kuormituksen rajoittamiseksi. Suppeita analyysipaketteja tulisi laajentaa raskasmetallien osalta, sillä vähäinen analyysivalikoima ei edusta kaikkia kohteita. Tavoitteena on ohjata maanläjitystoiminta sellaisille alueille, joilla vesiin kohdistuvat haitat voidaan hallita.
  • Takalo, Mimmi (Helsingin yliopisto, 2021)
    In 2011 Anglo American published a promising multi metal ore deposit in Sodankylä, Northern Finland. The ore is named Sakatti, after a small pond in the vicinity of the discovering place. The ore is under the Viiankiaapa mire, which is part of national mire protecting program and Natura 2000 program. Viinkiaapa is at the eastern side of river Kitinen, which is known to have flooded, bringing mineral material to the mire. To prevent the possibly environment effects in the future, it is essential to know present conditions of the mire. The study area is at the southern part of the Viiankiaapa mire and consist of eight sampling sites for peat. The basal sediment of the study area was determined with ground penetrating radar profiles that pass the sampling sites. To study the mineral supply of the mire, nine elements (Na, Mg, Al, S, P, K, Ca, Mn, and Fe) were chosen for geochemical analyses and the ash content of the peat profiles was determined. The basal sediment is highly affected by the vicinity of the river Kitinen. Fluvial channels have eroded till, which was deposited during the last glacial period. At the eastern side of the study area possibly aeolian sand is detected. Depressions eroded by fluvial channels are filled by gyttja, typically below 179 m a.s.l. The geochemistry of the peat indicates that the early phase of the mire was characterized with higher mineral supply. At the eastern part of Viiankiaapa the mineral supply has decreased after the early phase of the mire. The mineral supply has been higher at the middle parts of the mire throughout the Holocene. The floods of the river Kitinen are the main source of the mineral supply. The decrease in the mineral supply indicates that the flooding events have reduced, and the normal floods inundate smaller area than the early floods.