Browsing by Subject "valuma-alue"
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(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.
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(2023)Global warming and anthropogenic activity will change the environmental conditions in the northern regions. For example, precipitation and river flow are expected to increase, the amount of organic matter ending up in the sea from land will increase, and its quality will change. The impact of changes in organic matter on northern coastal ecosystems and the carbon cycle is poorly known and these impacts need to be studied. In this study, the amount, quality and variations of organic matter accumulated in the surface sediments of the Bothnian Bay coastal areas in the northern part of the Baltic Sea and in the Liminka Bay over the past 100 years are studied by analyzing the concentrations of organic carbon and nitrogen (TOC and TN), C/N ratio, and the stable isotope ratios δ13C and δ15N, thus assessing environmental change in the coastal area of the Bothnian Sea. The accumulation of organic matter along the coast of Bothnian Bay is affected by both the proximity of the rivers and the land cover and land use of the river basin. More organic matter accumulates on the coasts (average 3.5 wt%) than further into the open sea (average 1.9 wt%). Contrary to presuppositions, there is no clear variation in the quality of organic matter between the coast and the open sea, but the observed change is north-south: in the northern areas, organic matter is more terrestrial and autochthonous, and in the southern areas it is more aquatic and allochthonous. The northern regions are characterized by large rivers with large amounts of forests and peatlands in the catchment areas. Further south, the rivers are smaller and carry less organic matter in quantity. Further north in the coastal ecosystem, the amount of primary production is lower and nitrogen does not limit primary production, as opposed to more southern areas. Primary production of ice may also have affected the organic matter deposited in the Bothnian Sea sediments. The amount of organic matter deposited in Liminka Bay has been on the rise over the past century, probably due to global warming, increased river flow and the impact of human activity. Based on the C/N ratio, the material has been more terrestrial in the 1930s to 1970s, after which the material has become more aquatic. In addition, aquatic primary production has increased in the Liminka Bay and nitrogen has begun to restrict primary production more. The study shows that climate and environmental change and human activities affect the amount and quality of organic matter in northern coastal areas, but further research is needed to determine more accurate ecosystem impacts.
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(2022)The Arctic is facing a major turning point with climate change and the region's climate will experience a particularly sharp rise in temperature. Subarctic ponds are important habitats and shelters for many organisms in the area but are nevertheless poorly known compared to larger water bodies. Along with climate change, the importance of studying ponds becomes more important as they are the first to manifest a changing climate. Factors affecting the water properties of subarctic ponds include the characteristics of the catchment area, such as its location relative to the sea, altitude, bedrock, and soil. Of the climatic factors, the temperature in the summer months and the amount of precipitation are of great importance. The purpose of the thesis was to find out the factors influencing the water properties of ponds in the Kilpisjärvi region and how the water properties vary between ponds. Water samples were collected from 94 tundra ponds in and around Malla Strict Nature Reserve and in the areas around Ailakkavaara in August-September 2018 and 2019. The collected samples were later analyzed in the laboratory of the Department of Geosciences and Geography in University of Helsinki. The hydrochemical variables studied were metals dissolved in water, major ions, and total phosphorus and nitrogen. Variables describing catchment characteristics such as the Normalized Difference Vegetation Index (NDVI), TWI (Topographic Wetness Index) and climatic variables such as precipitation during the summer months and average temperature in July were collected from open spatial data sources. Based on the results of the principal component analysis (PCA), the chemical properties of pond waters vary slightly on average between Malla and Ailakkavaara, but there is more variation within the regions. The characteristics of the catchment areas and the climate clearly influenced the vegetation type surrounding the ponds, but these factors were not as strongly reflected in the characteristics of the pond waters. The absolute amounts of nutrients and water-dissolved metals are small, but the relative variation between ponds is substantial. Based on GAM-modeling, influence of groundwater (deuterium excess) was the single most significant factor influencing water quality, which was the explanatory variable for several water properties. The drier-than-average summer months in the study years emphasize the importance of runoff to water quality. Rainfall during the summer months, altitude, mean temperature in July, and amount of vegetation (NDVI) were the main factors influencing the subarctic ponds in the study. The increase in temperature caused by climate change will raise the temperature of pond waters and increased precipitation will increase the runoff of metals dissolved in ponds.
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