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...
BackgroundInadequate iodine intake has been identified in several population groups in the Nordic countries over the past years; however, studies of iodine status in infants and toddlers are scarce.ObjectiveThe aim of this study is to evaluate the iodine status and dietary iodine sources among 18-month-old toddlers from Norway.MethodsCross-sectional and country representative data from the Little in Norway study were used. All children who had given a spot urine sample at 18 months age were included (n = 416). Urinary iodine concentration (UIC) was determined by inductively coupled plasma mass-spectrometry. Dietary habits and supplement use were measured by a food frequency questionnaire.ResultsMedian (25th–75th percentiles [p25–p75]) UIC was 129 (81–190) μg/L while estimated median (p25–p75) habitual iodine intake was 109 (101–117) μg/day. None of the children were below the estimated average requirement (EAR) of 65 μg/day or above the upper intake level of 180 μg/day. There were no differences in either UIC or estimated habitual iodine intake between different geographic areas in Norway. Milk was the most important iodine source, contributing an estimated 70% to the total iodine intake, while other foods rich in iodine such as seafood and enriched baby porridge contributed about 30%.ConclusionsThe iodine status among 18-month-old toddlers from different geographic areas in Norway was sufficient, indicated by a median UIC above the WHO cutoff of 100 μg/L. This was further supported by the estimated habitual iodine intake, where none of the participants were below the EAR. Milk was an important iodine source in this age group; thus children with a low intake might be at risk of insufficient iodine intake.
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