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- Nfon, Erick, et al.
(författare)
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Biomagnification of organic pollutants in benthic and pelagic marine food chains from the Baltic Sea
- 2008
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Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 397:1-3, s. 190-204
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Tidskriftsartikel (refereegranskat)abstract
- The trophic transfer of organic pollutants with varying physical chemical properties was determined in both a pelagic and benthic food chain using delta N-15 as a continuous variable for assessing trophic levels. The trophic transfer of organic pollutants through the entire food chain in terms of food chain magnification factors (FCMFs) was quantified from the slope of the regression between In [concentration] and delta N-15. Organic pollutants with statistically significant FCMFs >1 were considered to biomagnify within the food chain, whereas those with FCMFs < 1 were considered to trophically dilute. Statistically significant FCMFs >1 were found for PCB congeners and organochlorine pesticides in the Baltic food chains whereas statistically significant FCMFs <1 were found for PAHs and PCNs due to trophic dilution resulting from metabolism. FCMFs were generally greater in the pelagic food chain than in the benthic food chain. However, estimated FCMFs for the benthic food chain are likely in error, as the delta N-15 method suggested a food chain structure which was not consistent with the known dietary patterns of the species. Biomagnification factors (BMFs) were additionally calculated as the ratio of the lipid normalized concentrations in the predator and prey species with adjustment for trophic level and were generally consistent with the FCMFs with BMF >1 for PCBs and organochlorines.
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| 2. |
- Nfon, Erick, et al.
(författare)
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Development of a dynamic model for estimating the food web transfer of chemicals in small aquatic ecosystems
- 2011
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Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 409:24, s. 5416-5422
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Tidskriftsartikel (refereegranskat)abstract
- A dynamic combined fate and food web model was developed to estimate the food web transfer of chemicals in small aquatic ecosystems (i.e. ponds). A novel feature of the modeling approach is that aquatic macrophytes (submerged aquatic vegetation) were included in the fate model and were also a food item in the food web model. The paper aims to investigate whether macrophytes are effective at mitigating chemical exposure and to compare the modeling approach developed here with previous modeling approaches recommended in the European Union (EU) guideline for risk assessment of pesticides. The model was used to estimate bioaccumulation of three hypothetical chemicals of varying hydrophobicity in a pond food web comprising 11 species. Three different macrophyte biomass densities were simulated in the model experiments to determine the influence of macrophytes on fate and bioaccumulation. Macrophytes were shown to have a significant effect on the fate and food web transfer of highly hydrophobic compounds with log K(ow)> = 5. Modeled peak concentrations in biota were highest for the scenarios with the lowest macrophyte biomass density. The distribution and food web transfer of the hypothetical compound with the lowest hydrophobicity (log K(ow) = 3) was not affected by the inclusion of aquatic macrophytes in the pond environment. For the three different hypothetical chemicals and at all macrophyte biomass densities, the maximum predicted concentrations in the top predator in the food web model were at least one order of magnitude lower than the values estimated using methods suggested in EU guidelines. The EU guideline thus provides a highly conservative estimate of risk. In our opinion, and subject to further model evaluation, a realistic assessment of dynamic food web transfer and risk can be obtained using the model presented here.
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| 3. |
- Nfon, Erick, et al.
(författare)
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Influence of submerged aquatic vegetation on the fate and food web transfer of pesticides in small freshwater ecosystems
- 2009
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Ingår i: Chemosphere. - 0045-6535 .- 1879-1298.
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Tidskriftsartikel (refereegranskat)abstract
- A dynamic combined fate and food web model was developed to investigate the influence of macrophytes (submerged aquatic vegetation) on the fate and food web transfer of pesticides of varying chemical properties in small-scale ecosystems such as ponds, streams, ditches or mesocosms. The model results indicate that aquatic macrophytes have a significant effect on the fate and food web transfer of highly hydrophobic compounds with log KOW ≥ 5. Modelled peak concentrations in biota were highest for the scenarios assuming the lowest macrophytes biomass density. The distribution and food web transfer of compounds with log KOW ≤ 4, which is a more representative hydrophobicity of the majority of current-use pesticides, are not affected by the inclusion of aquatic macrophytes in the pond environment. The increased importance of macrophytes for the highly hydrophobic compounds is a result of the dominance of particle deposition in the mass transfer of organic compounds from water to macrophytes. It is recommended that the mechanistic model developed here be used as a tool for interpreting laboratory, mesocosm and field measurements as well as a possible higher-tier regulatory tool, especially for assessing the aquatic behaviour of pesticides with high KOW values.
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| 4. |
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| 6. |
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| 7. |
- Nfon, Erick, 1969-
(författare)
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Tools for Evaluating the Fate and Bioaccumulation of Organic Compounds in Aquatic Ecosystems
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The bioaccumulation of organic contaminants in aquatic ecosystems has been a key focus in environmental toxicology over the last decades. Bioaccumulation is a key concept in ecological risk assessments since it controls the internal dose of potential environmental contaminants. Information on the bioaccumulation of contaminants is used by regulatory authorities in the development of water quality standards, categorizing substances that are potential hazards and quantifying the risk of chemicals to human health. A basis for identifying priority chemicals has been the use of the octanol-water partition coefficient (KOW) as a criterion to estimate bioaccumulation potential. However, recognizing that the bioaccumulation process is not controlled by the hydrophobicity of a chemical alone, this thesis proposes a set of tools, incorporating chemical properties, environmental characteristics and physiological properties of organisms, to study the bioaccumulation of contaminants in aquatic ecosystems. In striving to achieve this objective, a tool based on an equilibrium lipid partitioning approach was used in Paper I to evaluate monitoring data for bioaccumulation of organic contaminants. In Papers II and III, mechanistic based modelling tools were developed to describe bioaccumulation of hydrophobic compounds in aquatic food webs. In Paper IV, the bioaccumulation of organic compounds in aquatic food chains was studied using stable isotopes of nitrogen. The mechanistic fate and food web models developed in this thesis provide regulators and chemical manufacturers with a means of communicating scientific information to the general public and readily applicable mechanistic fate and food web models that are easily modified for evaluative assessments purposes.
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| 8. |
- Nfon, Erick, et al.
(författare)
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Trophodynamics of mercury and other trace elements in a pelagic food chain from the Baltic Sea
- 2009
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Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 407:24, s. 6267-74
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Tidskriftsartikel (refereegranskat)abstract
- Mercury (Hg) and 13 other trace elements (Al, Ti, V, Cr, Fe, Mn, Co, Ni, Cu, Zn, As, Cd, and Pb) were measured in phytoplankton, zooplankton, mysis and herring in order to examine the trophodynamics in a well-studied pelagic food chain in the Baltic Sea. The fractionation of nitrogen isotopes (delta(15)N) was used to evaluate food web structure and to estimate the extent of trophic biomagnification of the various trace elements. Trophic magnification factors (TMFs) for each trace element were determined from the slope of the regression between trace element concentrations and delta(15)N. Calculated TMFs showed fundamental differences in the trophodynamics of the trace elements in the pelagic food chain studied. Concentrations of Al, Fe, Ni, Zn, Pb and Cd showed statistically significant decreases (TMF<1) with increasing trophic levels and thus these trace elements tropically dilute or biodilute in this Baltic food chain. Cu, As, Cr, Mn, V, Ti and Co showed no significant relationships with trophic levels. Hg was unique among the trace elements studied in demonstrating a statistically significant increase (TMF>1) in concentration with trophic level i.e. Hg biomagnifies in this Baltic food chain. The estimated TMF for Hg in this food chain was comparable to TMFs observed elsewhere for diverse food chains and locations.
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| 9. |
- Skarphéðinsdóttir, Halldóra, et al.
(författare)
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Bioaccumulation and Biomagnification of Organochlorines in a Marine Food Web at a Pristine Site in Iceland
- 2010
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Ingår i: Archives of Environmental Contamination and Toxicology. - : Springer Science and Business Media LLC. - 0090-4341 .- 1432-0703. ; 58:3, s. 800-809
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Tidskriftsartikel (refereegranskat)abstract
- Organochlorine (OC) bioaccumulation and biomagnification were studied in a marine food web at a pristine site in Iceland. The species studied were the gastropod and grazer chink shell (Lacuna vincta), the filter feeding bivalve blue mussel (Mytilus edulis), the predators butterfish (Pholis gunnellus), and the seabird black guillemot (Cepphus grylle), all sampled and analysed in 1996-1997. Individual OC levels were generally low in chink shell and blue mussels, somewhat elevated in the fish, and an order of a magnitude higher in the top predator black guillemot, except for SigmaHCH (hexachlorocyclohexane isomers) and Sigmachlordane levels, which were similar in all organisms, ranging from 10 to 36 ng/g lipid weight (lw). In the molluscs and fish, mean concentrations of SigmaPCB (polychlorinated biphenyl) ranged from 111 to 377 ng/g lw, SigmaDDT (dichlorodiphenyltrichloroethane) ranged from 19 to 65 ng/g lw, and HCB (hexachlorobenzene) ranged from 21 to 30 ng/g lw. The levels of same OCs in the black guillemot were on average 2352, 361, and 283 ng/g lw, respectively. The OC tissue concentrations in blue mussel and black guillemot are comparable to levels in Arctic and sub-Arctic regions, but OC levels in blue mussel tissue were an order of magnitude lower than found in the North Sea and the Baltic Sea. The relative composition of OCs were generally similar among species with the PCB congeners emerging as the most abundant compounds with levels an order of magnitude higher than the other compounds in all species. Food web magnification factors (FWMFs) were determined for the OCs by using trophic levels determined from delta(15)N. FWMFs >1, indicating biomagnification, were found for SigmaPCB, penta- or higher chlorinated PCBs (e.g., PCB 101, 118, 138, 153, 180), beta-HCH, HCB, SigmaDDT, p,p-DDE, and transnonachlor. The highest FWMF was observed for PCB 180 at FWMF = 5.8.
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