<p> The forms of phosphorus in sediments of acid and non-acid shield lakes were determined in order to assess the effects of lake acidification on the mobility of sediment phosphorus. Sediment phosphorus is conveniently classified into three categories: non-apatite inorganic phosphorus (NAI-P), apatite-P and organic P. The distribution of P between different categories was found to be dependent on the lithology of the lake basin, the pH in the water column, and the redox conditions.</p> <p> More than 90% of inorganic P in shield lake sediments was in the NAI-P category, associated presumably with hydrated Fe and Al oxides. Organic P accounted for more than 40% of total P in sediments of acid lakes, which is proportionally higher than that found in sediments of neutral lakes. Bioavailable P, a measure of the fraction of sediment inorganic P readily available for biological utilization, amounted to ~70% of NAI-P, similar to that found in hard water lakes.</p> <p> A series of experiments was designed to investigate the immobilization of P from solution. The uptake of P by solid phase was explained by an adsorption mechanism. The quantitative estimates of phosphate sorption parameters for sediments of acid and non-acid lakes show that mineralogical and chemical characteristics of sediments are more important than the pH of water in determining their efficiency of P removal. Therefore, acidification of lakes does not significantly influence the uptake of P by sediments.</p> / Thesis / Master of Science (MSc)

Fossil fuel combustion produces fly-ash particles that are released into the atmosphere and deposited in the environment. A particularly characteristic kind of fly-ash is spheroidal carbonaceous particles. They are composed of an amorphous carbon matrix in which other elements are dispersed. The elemental carbon content makes them very resistant to chemical degradation and these particles can be relatively easily extracted from sediment and soil samples using a method described in this thesis. The distribution of spheroidal carbonaceous particles in lake sediment profiles, surface sediments and forest soils has been studied. Cores from several Swedish lakes have been analysed and, although the lakes are from different parts of the country, consistent trends in the deposition of the carbonaceous particles have been found. The analyses of dated cores show that the carbonaceous particle deposition in the sediments follows the same general pattern as statistics for Swedish coal and oil combustion over the last two centuries. This indicates that the sediment records reflect the history of the atmospheric deposition of particulate pollutants from fossil fuel combustion. Analysis of surface sediment samples provides an integrated picture of the deposition over the preceding few years and can be used to indicate the contemporary geographical pattern of deposition from the atmosphere. Two sets of surface sediment samples (0-1 cm) were analysed. One comprised samples from 66 lakes around Sweden's second largest city, Gothenburg, and showed very high carbonaceous particle concentrations within a distance of 50 to 100 km from the city. The second set comprised surface sediment samples from 114 lakes distributed all over Sweden. This survey of Sweden demonstrated a geographical north-south gradient with more than a hundred times higher particle concentrations in the south than in the north. This distribution is similar to the distribution of other air pollutants (data obtained from a moss survey and an air monitoring program) and suggests that carbonaceous particles in palaeolimnological investigations of air pollution, can be used as tracers for pollutants that are otherwise difficult to determine in lake sediments. Spheroidal carbonaceous particles also accumulate in soils, and forest soil samples can be used for geographical surveys of particle deposition. In Swedish podzol soils the particles mainly accumulate in the thin organic horizon and concentrations in this layer reflect the total deposition since industrialisation, although most will have been deposited during the last few decades. Since the spheroidal carbonaceous particle record in Swedish lake sediments has a characteristic temporal pattern, carbonaceous particle profiles can be used for indirect dating of recent sediment cores. Analyses of multiple sediment cores from three lakes demonstrate that carbonaceous particles can also be used for studies of sediment distribution in lake basins. Results from Gårdsjön indicate that the acidification of the lake changed sediment distribution processes from a normal sediment focusing regime to a more even distribution of sediments over the lake bottom. Liming of the lake seems to have restored normal sedimentation processes. / <p>Diss. (sammanfattning) Umeå : Umeå universitet, 1992, Härtill 8 uppsatser</p> / digitalisering@umu