Ändra sökning
Avgränsa sökresultatet
1 - 10 av 10
RefereraExporteraLänk till träfflistan
Permanent länk
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf
Träffar per sida
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sortering
  • Standard (Relevans)
  • Författare A-Ö
  • Författare Ö-A
  • Titel A-Ö
  • Titel Ö-A
  • Publikationstyp A-Ö
  • Publikationstyp Ö-A
  • Äldst först
  • Nyast först
  • Skapad (Äldst först)
  • Skapad (Nyast först)
  • Senast uppdaterad (Äldst först)
  • Senast uppdaterad (Nyast först)
  • Disputationsdatum (tidigaste först)
  • Disputationsdatum (senaste först)
  • Standard (Relevans)
  • Författare A-Ö
  • Författare Ö-A
  • Titel A-Ö
  • Titel Ö-A
  • Publikationstyp A-Ö
  • Publikationstyp Ö-A
  • Äldst först
  • Nyast först
  • Skapad (Äldst först)
  • Skapad (Nyast först)
  • Senast uppdaterad (Äldst först)
  • Senast uppdaterad (Nyast först)
  • Disputationsdatum (tidigaste först)
  • Disputationsdatum (senaste först)
Markera
Maxantalet träffar du kan exportera från sökgränssnittet är 250. Vid större uttag använd dig av utsökningar.
  • 1.
    Dahlgren, Elin
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för miljövetenskap och analytisk kemi.
    Enhus, Carolina
    Lindqvist, Dennis
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för miljövetenskap och analytisk kemi.
    Eklund, Britta
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för miljövetenskap och analytisk kemi.
    Asplund, Lillemor
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för miljövetenskap och analytisk kemi.
    Induced production of brominated aromatic compounds in the alga Ceramium tenuicorne2015Ingår i: Environmental science and pollution research international, ISSN 0944-1344, E-ISSN 1614-7499, Vol. 22, nr 22, s. 18107-18114Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In the Baltic Sea, high concentrations of toxic brominated aromatic compounds have been detected in all compartments of the marine food web. A growing body of evidence points towards filamentous algae as a natural producer of these chemicals. However, little is known about the effects of environmental factors and life history on algal production of brominated compounds. In this study, several congeners of methoxylated polybrominated diphenyl ethers (MeO-PBDEs), hydroxylated polybrominated diphenyl ethers (OH-PBDEs) and brominated phenols (BPs) were identified in a naturally growing filamentous red algal species (Ceramium tenuicorne) in the Baltic Sea. The identified substances displayed large seasonal variations in the alga with a concentration peak in July. Production of MeO-/OH-PBDEs and BPs by C. tenuicorne was also established in isolated clonal material grown in a controlled laboratory setting. Based on three replicates, herbivory, as well as elevated levels of light and salinity in the culture medium, significantly increased the production of 2,4,6-tribromophenol (2,4,6-TBP). Investigation of differences in production between the isomorphic female, male and diploid clonal life stages of the alga grown in the laboratory revealed a significantly higher production of 2,4,6-TBP in the brackish water female gametophytes, compared to the corresponding marine gametophytes. Even higher concentrations of 2,4,6-TBP were produced by marine male gametophytes and sporophytes.

  • 2. Dahlgren, Elin
    et al.
    Lindqvist, Dennis
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för miljövetenskap och analytisk kemi.
    Dahlgren, Henrik
    Asplund, Lillemor
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för miljövetenskap och analytisk kemi.
    Lehtila, Kari
    Trophic transfer of naturally produced brominated aromatic compounds in a Baltic Sea food chain2016Ingår i: Chemosphere, ISSN 0045-6535, E-ISSN 1879-1298, Vol. 144, s. 1597-1604Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Brominated aromatic compounds (BACs) are widely distributed in the marine environment. Some of these compounds are highly toxic, such as certain hydroxylated polybrominated diphenyl ethers (OH-PBDEs). In addition to anthropogenic emissions through use of BACs as e.g. flame retardants, BACs are natural products formed by marine organisms such as algae, sponges, and cyanobacteria. Little is known of the transfer of BACs from natural producers and further up in the trophic food chain. In this study it was observed that total sum of methoxylated polybrominated diphenyl ethers (MeO-PBDEs) and OH-PBDEs increased in concentration from the filamentous red alga Ceramium tenuicorne, via Gammarus sp. and three-spined stickleback (Gasterosteus aculeatus) to perch (Perca fluviatilis). The MeO-PBDEs, which were expected to bioaccumulate, increased in concentration accordingly up to perch, where the levels suddenly dropped dramatically. The opposite pattern was observed for OH-PBDEs, where the concentration exhibited a general trend of decline up the food web, but increased in perch, indicating metabolic demethylation of MeO-PBDEs. Debromination was also indicated to occur when progressing through the food chain resulting in high levels of tetra-brominated MeO-PBDE and OH-PBDE congeners in fish, while some penta- and hexa-brominated congeners were observed to be the dominant products in the alga. As it has been shown that OH-PBDEs are potent disruptors of oxidative phosphorylation and that mixtures of different congener may act synergistically in terms of this toxic mode of action, the high levels of OH-PBDEs detected in perch in this study warrants further investigation into potential effects of these compounds on Baltic wildlife, and monitoring of their levels.

  • 3.
    Jensen, Sören
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för tillämpad miljövetenskap (ITM).
    Lindqvist, Dennis
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för tillämpad miljövetenskap (ITM).
    Asplund, Lillemor
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för tillämpad miljövetenskap (ITM).
    Lipid extraction and determination of halogenated phenols and alkylphenols as their pentafluorobenzoyl derivatives in marine organisms2009Ingår i: Journal of Agricultural and Food Chemistry, ISSN 0021-8561, E-ISSN 1520-5118, Vol. 57, nr 13, s. 5872-5877Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A method was developed for the extraction of lipids and analysis of halogenated phenols and alkylphenols in marine organisms. The extraction efficiency was evaluated by comparing the extractable lipid content and the recovery of 13 added phenols from three different marine species (herring, cod, and blue mussel), with the corresponding results from three well-established extraction procedures, the Bligh and Dyer (B&D), the Smedes (S), and the Jensen (J) methods. The J method and the new method, Jensen centrifugation (Jc), gave phenol recoveries of 80-100% for all species, whereas the B&D and S methods gave relatively low recoveries for the most acidic phenols, with recoveries of only 20-50% for pentachlorophenol (PCP) depending on the species. It was concluded that this effect was governed by the dissociation of the phenols and adsorption to the protein tissue during the extraction (due to ionic interactions). To increase the sensitivity of the analysis, the phenols were converted to their pentafluorobenzoyl esters, by using a tetrabutylammonium-catalyzed extractive acylation. The reaction was quantitative within 2 min at room temperature, and the formed derivatives were persistent enough to withstand treatment with concentrated sulfuric acid.

  • 4.
    Konovalenko, Lena
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Bradshaw, Clare
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Andersson, E.
    Lindqvist, Dennis
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för miljövetenskap och analytisk kemi.
    Kautsky, U.
    Evaluation of factors influencing accumulation of stable Sr and Cs in lake and coastal fish2016Ingår i: Journal of Environmental Radioactivity, ISSN 0265-931X, E-ISSN 1879-1700, Vol. 160, s. 64-79Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    As a result of nuclear accidents and weapons tests, the radionuclides Cs-137 and Sr-90 are common contaminants in aquatic ecosystems. Concentration ratios (CR) based on concentrations of stable Cs and Sr in biota and media are used for the estimation of transfer of their radioisotopes for radiation dose calculations in environmental and human safety assessments. Available element-specific CRs vary by over an order of magnitude for similar organisms, thus affecting the dose estimates proportionally. The variation could be reduced if they were based on a better understanding of the influence of the underlying data and how that affects accumulation and potential biomagnification of stable Cs and Sr in aquatic organisms. For fish, relationships have been identified between water concentrations of K and CR of Cs-137, and between water concentrations of Ca and CR of Sr-90. This has not been confirmed for stable Cs and Sr in European waters. In this study, we analysed an existing dataset for stable Cs and Sr, as well as K and Ca, in four Swedish lakes and three Baltic Sea coastal areas, in order to understand the behaviour of these elements and their radioisotopes in these ecosystems. We found significant seasonal variations in the water concentrations of Cs, Sr, K and Ca, and in electrical conductivity (EC), especially in the lakes. CR values based on measurements taken at single or few time points may, therefore, be inaccurate or introduce unnecessarily large variation into risk assessments. Instead, we recommend incorporating information about the underlying variation in water concentrations into the CR calculations, for example by using the variation of the mean. The inverse relationships between fish CRCs -[K](water) and fish CRSr-[Ca](water), confirmed that stable Cs and Sr follow the same trends as their radioisotopes. Thus, they can be used as proxies when radioisotope data are lacking. EC was also strongly correlated with K and Ca concentrations in the water and could potentially be used as a quick and cost-effective method to estimate water chemistry to obtain less variable CR. We also recommend some simple improvements to data collection that would greatly enhance our ability to understand Cs and Sr uptake by fish.

  • 5.
    Lindqvist, Dennis
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för miljövetenskap och analytisk kemi.
    Determination of hydroxylated polybrominated diphenyl ethers in blood from Baltic grey sealsManuskript (preprint) (Övrigt vetenskapligt)
  • 6.
    Lindqvist, Dennis
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för miljövetenskap och analytisk kemi.
    Hydroxylated polybrominat­ed diphenyl ethers in Baltic Sea biota: Natural production, food web distribution and biotransformation2016Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Hydroxylated polybrominated diphenyl ethers (OH-PBDEs) are naturally produced in aquatic ecosystems e.g. by algae. Many OH-PBDEs have been observed to be highly bioactive and to cause adverse effects through several pathways, e.g. via disrupting oxidative phosphorylation (OXPHOS). The levels of some OH-PBDEs have increased in Baltic biota over the past decades. This may be associated with the nutrient enrichment of the Baltic Sea, which has favored growth of some of the OH-PBDE producers.

    Ceramium tenuicorne has been suggested to be a producer of OH-PBDEs in the Baltic Sea, which is supported by the results presented in this thesis. The levels of OH-PBDEs were observed to fluctuate greatly in C. tenuicorne over the summer season, and to correlate with the levels of pigments in the algae. However, the observed congener pattern in C. tenuicorne questioned theories regarding the mechanism of their biosynthesis. The results indicate a much more selective pathway for biosynthesis than previously suggested for the production of OH-PBDEs.

    One of the most abundant OH-PBDEs in C. tenuicorne, 6-OH-BDE137, has previously been observed to be toxic to bacteria, fungi, and crustaceans. Furthermore, Baltic gammarids seemed to change their feeding preferences towards less grazing on C. tenuicorne during the production peek of OH-PBDEs in the alga. This suggests that OH-PBDEs may serve as allelochemical defense agents for C. tenuicorne.

    The transport and fate of OH-PBDEs through a Baltic food chain was also studied, including C. tenuicorne, Gammarus spp., three-spined stickleback (Gasterosteus aculeatus), and perch (Perca fluviatilis). A small portion of the OH-PBDEs were observed to be methylated in the alga, or by associated bacteria. The methylated OH-PBDEs biomagnified in the food chain up to perch, in which they were converted back to the OH-PBDEs via demethylation. The OH-PBDEs and their methylated counterparts were also partially debrominated in the food chain, which resulted in high concentration of 6-OH-BDE47 in the perch. This congener is the most toxic OH-PBDE with regards to OXPHOS disruption.

    Another biotransformation of OH-PBDEs was identified in Baltic Sea blue mussels (Mytilus edulis). High concentrations of OH-PBDEs were conjugated with lipophilic moieties, e.g. fatty acids. This increases the residence time of the OH-PBDEs in the mussels. Mussels have been suggested to conjugate steroids with fatty acids as a means to regulate hormone levels. The conjugation of OH-PBDEs to fatty acids may occur due to intrusion into this pathway. Methods were developed to include quantification of conjugated OH-PBDEs in the analysis of mussels.

    OH-PBDEs were also quantified in blood from Baltic Sea grey seals (Halichoerus grypus). Seals originating from the Baltic proper were observed to be more highly exposed to 6-OH-BDE47 than seals from the Gulf of Bothnia. However, the levels of OH-PBDEs were generally low. A major effort was invested into securing these results, including development of a new analytical method. Blood obtained from dead seals is a difficult matrix for quantification of OH-PBDEs, and previous attempts using an established method yielded unsatisfactory results.

  • 7.
    Lindqvist, Dennis
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för miljövetenskap och analytisk kemi.
    Asplund, Lillemor
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för miljövetenskap och analytisk kemi.
    Determination of Hydroxylated Polybrominated Diphenyl Ethers in Blood from Baltic Grey Seals2019Ingår i: Journal of analysis and testing, ISSN 2096-241X, Vol. 3, nr 4, s. 287-294Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Naturally produced hydroxylated polybrominated diphenyl ethers (OH-PBDEs) have been extensively studied in the lower end of the Baltic Sea food web. Certain OH-PBDE congeners have displayed increasing concentrations over the last 30 years in herring (Clupea harengus) from the Baltic proper. However, studies on the top carnivores in the Baltic Sea are scarce. Quantitative data on OH-PBDEs exist for ringed seal (Pusa hispida) from the Gulf of Bothnia, but only a limited amount of data have been produced with regard to Baltic grey seal (Halichoerus grypus), and seals from the Baltic proper. A method was developed and evaluated for quantification of OH-PBDEs in coagulated whole blood. The method was applied on blood obtained from dead grey seals originating from different parts of the Baltic Sea. The levels of OH-PBDEs were observed to be low in the analyzed seals in comparison with reported levels in white-tailed sea eagle nestlings (Halizeetus albicilla), and some Baltic fish species. The levels of the dominant congener, 6-OH-BDE47, were statistically significantly higher in seals from the Baltic proper than in seals from the Gulf of Bothnia. Hydroxylated polychlorinated biphenyls (OH-PCBs) were observed to be of much higher concentration than the OH-PBDEs in the analyzed seals. The average concentration of the dominant OH-PCB congener, 4-OH-CB107, was one order of magnitude greater than that of 6-OH-BDE47.

  • 8.
    Lindqvist, Dennis
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för miljövetenskap och analytisk kemi.
    Dahlgren, Elin
    Asplund, Lillemor
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för miljövetenskap och analytisk kemi.
    Biosynthesis of hydroxylated polybrominated diphenyl ethers and the correlation with photosynthetic pigments in the red alga Ceramium tenuicorne2017Ingår i: Phytochemistry, ISSN 0031-9422, E-ISSN 1873-3700, Vol. 133, s. 51-58Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Hydroxylated polybrominated diphenyl ethers (OH-PBDEs) have been identified in a variety of marine organisms from different trophic levels indicating a large spread in the environment. There is much evidence pointing towards natural production as the major source of these compounds in nature. However, much is still not known about the natural production of these compounds. Seasonal trend studies have shown large fluctuations in the levels of OH-PBDEs in Ceramium tenuicorne from the Baltic Sea. Yet, even though indications of stimuli that can induce the production of these compounds have been observed, none, neither internal nor external, has been assigned to be responsible for the recorded fluctuations. In the present study the possible relationship between the concentration of pigments and that of OH-PBDEs in C. tenuicorne has been addressed. Significant correlations were revealed between the concentrations of all OH-PBDEs quantified and the concentrations of both chlorophyll a and Σxanthophylls + carotenoids. All of which displayed a concentration peak in mid-July. The levels of OH-PBDEs may be linked to photosynthetic activity, and hence indirectly to photosynthetic pigments, via bromoperoxidase working as a scavenger for hydrogen peroxide formed during photosynthesis. Yet the large apparent investment in producing specific OH-PBDE congeners point towards an targeted production, with a more specific function than being a waste product of photosynthesis. The OH-PBDE congener pattern observed in this study is not agreeable with some currently accepted models for the biosynthesis of these compounds, and indicates a more selective route than previously considered in C. tenuicorne.

  • 9.
    Lindqvist, Dennis
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK). Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för tillämpad miljövetenskap (ITM).
    Jensen, Sören
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK). Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för tillämpad miljövetenskap (ITM).
    Asplund, Lillemor
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK). Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för tillämpad miljövetenskap (ITM).
    Lipid-soluble conjugates of hydroxylated polybrominated diphenyl ethers in blue mussels from the Baltic Sea2014Ingår i: Environmental science and pollution research international, ISSN 0944-1344, E-ISSN 1614-7499, Vol. 21, nr 2, s. 954-961Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Hydroxylated polybrominated diphenyl ethers (OH-PBDEs) of proposed natural origin have been detected throughout the food web of the Baltic Sea. Some OH-PBDEs have been shown to disrupt oxidative phosphorylation and the thyroid hormone system in exposed organisms. This paper describes an investigation into the fate of OH-PBDEs in the Baltic Sea's predominant specie, the blue mussel. The main focus was on the conjugation of OH-PBDEs with lipophilic moieties (e.g., fatty acids) and the potential role this transformation mechanism may have in heavily exposed mussels in nature. Analytical methods were developed to accurately determine the concentrations of these conjugates in blue mussels collected on different occasions during the summer in a coastal area of the Baltic proper. The measured concentrations of conjugated OH-PBDEs were compared to those of the unconjugated parent compounds, and it was found that in some cases, the levels of the conjugated derivatives can be equal or even higher than the levels of the unconjugated OH-PBDEs. This is, to our knowledge, the first study on lipid-soluble OH-PBDE conjugates, and the first study to investigate the occurrence of such conjugates of halogenated phenolic compounds in environmentally exposed mussels. The mussels were also found to contain hydrolysable water-soluble derivatives of OH-PBDEs (such as e.g., glucuronic acid and/or sulfate conjugates etc.). These were tentatively determined to be of lower concentration (by up to an order of magnitude) than that of the OH-PBDEs which were conjugated with lipophilic moieties.

  • 10.
    Löfstrand, Karin
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för miljökemi.
    Liu, Xitao
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för tillämpad miljövetenskap (ITM). Beijing Normal University, PR China.
    Lindqvist, Dennis
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för tillämpad miljövetenskap (ITM).
    Jensen, Sören
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för tillämpad miljövetenskap (ITM).
    Asplund, Lillemor
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för miljökemi.
    Seasonal variations of hydroxylated and methoxylated brominated diphenyl ethers in blue mussels from the Baltic Sea2011Ingår i: Chemosphere, ISSN 0045-6535, E-ISSN 1879-1298, Vol. 84, nr 4, s. 527-532Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Hydroxylated polybrominated diphenyl ethers (OH-PBDEs) and methoxylated polybrominated diphenyl ethers (MeO-PBDEs) found at high levels in the Baltic biota are mainly natural products, but can also be formed through metabolism or abiotic oxidation of polybrominated diphenyl ethers (PBDEs). The formation of OH-PBDEs is of concern since there is growing evidence of phenolic toxicity. This study investigates seasonal variations in levels of OH-PBDEs and MeO-PBDEs, focusing on an exposed species, the blue mussel (Mytilus edulis), sampled in the Baltic Sea in May, June, August and October of 2008. Both the OH-PBDE and MeO-PBDE levels in the mussels showed seasonal variations from May to October, the highest concentration of each congener appearing in June. The seasonal variation was more marked for OH-PBDEs than in MeO-PBDEs, but all congeners showed the same trends, except 6-MeO-BDE47 and 2′-MeO-BDE68, which did not significantly decline in concentrations after June. Biotic or abiotic debromination is suggested as a possible reason for the rapid decrease in methoxylated penta- and hexa-BDE concentrations observed in blue mussels from June to August, while the tetraBDE concentrations were stable. In addition, 1,3,7/1,3,8-tribrominated dibenzo-p-dioxins showed the same seasonal variation. The seasonal variations indicates natural formation and are unlikely to be due to transformation of anthropogenic precursors. The levels of PBDEs were fairly constant over time and considerably lower than those of the OH-PBDEs and MeO-PBDEs. The timing of the peaks in concentrations suggests that filamentous macro-algae may be important sources of these compounds found in the blue mussels from this Baltic Sea location.

1 - 10 av 10
RefereraExporteraLänk till träfflistan
Permanent länk
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf