| 1. |
- Björk, Mikael, 1957-
(author)
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Ecological and physiological aspects of contaminant accumulation and transport by the filter-feeding mussel, Mytilus edulis
- 1998
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Doctoral thesis (other academic/artistic)abstract
- This thesis examines the influence of food availability on the bioaccumulation kinetics and the transport of hydrophobic organic contaminants (HOCs) by the Baltic Sea blue mussel, Mytilus edulis. In laboratory studies, food availability was found to significantly modify the rate of physiological processes involved in filter-feeding. This also influenced the rate of exposure to HOCs as determined by the amount of HOCs associated with the flux of water and food. The uptake rate of HOCs by the mussels was found to be positively related to the exposure rate, whereas HOC elimination appeared to be unaffected by differences in food availability. However, the amount of HOCs assimilated declined with increases in the exposure rate, and the largest increase in HOC tissue concentrations was found at an intermediate food availability.The role of the blue mussel in the cycling of carbon and HOCs was also investigated in the field and by a modelling approach. As filter-feeders the mussels consume near-bed suspended particulate organic matter that, in contaminated areas, contains high concentrations of HOCs. Filter-feeding activity and the subsequent release of faecal matter by the mussels increased the vertical flux of HOCs from the water column to the benthic community by at least 50% in the study area. Other significant routes of HOC transport by mussels in the coastal zone of the Baltic proper include transfer to predators, elimination of dissolved HOC, and elimination via spawning and transfer to zooplanktivores, as indicated in the established annual budget models.It is concluded that the filter-feeding activity of the mussels have a significant influence on HOC fluxes within both the organism and the ecosystem. The findings presented here emphasise the role of animal physiology in contaminant kinetics and have important implications for the experimental design and interpretation of laboratory bioaccumulation and toxicity studies, as well as field sampling and marine monitoring programmes.
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| 2. |
- Josefsson, Sarah, 1976-
(author)
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Fate and transport of POPs in the aquatic environment : with focus on contaminated sediments
- 2011
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Doctoral thesis (other academic/artistic)abstract
- Persistent organic pollutants (POPs) are hydrophobic substances that readily sorb to organic matter in particles and colloids instead of being freely dissolved in the water phase. This sorption affects the bioavailability and environmental transport of the POPs. The major part of this thesis concerns the role of sediments as secondary sources of POPs. As the primary emissions decrease, contaminated sediments where POPs have accumulated can become the main source of contamination. If the contaminated sediment by time becomes covered with cleaner layers, the POPs are buried and no longer in contact with the aquatic environment. Experiments in this thesis showed, however, that new invading species can alter the sediment-water dynamics as a result of their bioturbation, i.e. mixing of sediment particles and pore-water. Marenzelleria spp., invading species in the Baltic Sea that burrow deeper than native species, were found to increase the remobilization of buried contaminants. The sediment-to-water flux was inversely related to the burial depth (2-10 cm) of the POP congeners (polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers) and also inversely related to the hydrophobicity of the congener. The flux was therefore most pronounced for less hydrophobic contaminants, which was linked to the bioirrigating behaviour of these species. Marenzelleria spp. also accumulated the buried POPs and increased concentrations in surface sediment. Contaminants previously considered buried at a ’safe’ depth can thus be remobilized as a result of the invasion of Marenzelleria spp. in the Baltic Sea.One method to decrease the remobilization of contaminants from sediments is ’capping’, i.e. a layer of clean material is placed as a cap on the sediment. By amending the cap with active materials, which sequester the POPs and decrease their availability, thinner layers can be used (’active capping’ or ’thin-layer capping’). Results from an experiment with thin-layer capping using different active materials (activated carbon (AC) and kraft lignin) showed that both the sediment-to-water flux and the bioaccumulation by benthic species of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), hexachlorobenzene (HCB) and octachlorostyrene (OCS) decreased with increased thickness of the cap layer (0.5-5 cm). Amendments with active materials further increased the cap efficiency. AC was more efficient than kraft lignin, and a 3 cm cap with 3.3% AC reduced the flux and bioaccumulation with ~90%. The reduction of the sediment-to-water flux was inversely related to the hydrophobicity of the POP, and reductions in the flux had similar magnitudes as reductions in the concentration in deep-burrowing polychaetes, demonstrating the importance of bioturbation for sediment-to-water transport.In a one-year study on the levels of PCDD/Fs, PCBs, and HCB in a coastal area of the Baltic Sea, the correlations between the POP levels and the levels of particles and organic carbon in the water were found to differ for POPs of different structure and hydrophobicity. The levels of PCDD/Fs decreased to one third in May, which could be related to the increased sedimentation, i.e. water-to-sediment transport, during spring bloom.
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| 3. |
- Lappalainen, Hanna K., et al.
(author)
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Pan-Eurasian Experiment (PEEX) : towards a holistic understanding of the feedbacks and interactions in the land-atmosphere-ocean-society continuum in the northern Eurasian region
- 2016
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In: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 16:22, s. 14421-14461
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Journal article (peer-reviewed)abstract
- The northern Eurasian regions and Arctic Ocean will very likely undergo substantial changes during the next decades. The Arctic-boreal natural environments play a crucial role in the global climate via albedo change, carbon sources and sinks as well as atmospheric aerosol production from biogenic volatile organic compounds. Furthermore, it is expected that global trade activities, demographic movement, and use of natural resources will be increasing in the Arctic regions. There is a need for a novel research approach, which not only identifies and tackles the relevant multi-disciplinary research questions, but also is able to make a holistic system analysis of the expected feedbacks. In this paper, we introduce the research agenda of the Pan-Eurasian Experiment (PEEX), a multi-scale, multi-disciplinary and international program started in 2012 (https://www.atm.helsinki.fi/peex/). PEEX sets a research approach by which large-scale research topics are investigated from a system perspective and which aims to fill the key gaps in our understanding of the feedbacks and interactions between the land-atmosphereaquatic-society continuum in the northern Eurasian region. We introduce here the state of the art for the key topics in the PEEX research agenda and present the future prospects of the research, which we see relevant in this context.
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| 4. |
- Laurén, Ari, et al.
(author)
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Nitrogen and Carbon Dynamics and the Role of Enchytraeid Worms in Decomposition of L, F and H Layers of Boreal Mor
- 2012
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In: Water, Air and Soil Pollution. - : Springer Science and Business Media LLC. - 0049-6979 .- 1573-2932. ; 223:7, s. 3701-3719
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Journal article (peer-reviewed)abstract
- Decomposition of organic material releases carbon dioxide (CO2) into the atmosphere, and dissolved organic carbon (DOC), dissolved organic nitrogen (DON) and ammonium (NH4-N) into soil water. Each of the decomposition products contributes differently to overall export of carbon (C) and nitrogen (N) to water courses. Our aim was to study the quantity and composition of the released C and N as affected by the organic material and soil fauna, represented by enchytraeid worms. We measured the release rate of carbon dioxide, and calculated the release rates for DOC and dissolved N in soil from repeated measurements of DOC and N pools during laboratory incubation of litter (L), fermented (F) and humus (H) layers of boreal forest mor. The intermediate decomposition products, DOC and DON, were characterised according to the molecule size. The release rate of the decomposition products was higher for fresh than for old organic material. The majority of N and C were released as NH4-N and CO2, respectively. The amount of extractable organic N in soil decreased by time but DON increased. Enchytraeids stimulated N mineralisation and the release of large molecule size DOC, particularly in L layer. The results suggest that organic N in extractable form biodegrades effectively, and that soil fauna have an important role in the decomposition. The results were interpreted from the water quality point of view and the implications of the results to modelling of decomposition and export of DOC and dissolved N to recipient water bodies are discussed. In the modelling context, the novelty of the study is the description of the intermediate decomposition products and the division of the dissolved organic compounds into low molecular weight and high molecular weight fractions.
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