| 1. |
- Otte, Jens C., et al.
(författare)
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A bioassay approach to determine the dioxin-like activity in sediment extracts from the Danube River : ethoxyresorufin-O-deethylase induction in gill filaments and liver of three-spined sticklebacks (Gasterosteus aculeatus L.)
- 2008
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Ingår i: Environment International. - Amsterdam : Elsevier. - 0160-4120 .- 1873-6750. ; 34:8, s. 1176-1184
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Tidskriftsartikel (refereegranskat)abstract
- Sediment samples from the upper Danube River in Germany have previously been characterized as ecotoxicologically hazardous and contaminants in these sediments may contribute to the observed decline of fish populations in this river section. For the investigation of sediment toxicity there is a need for development, standardization and implementation of in vivo test systems using vertebrates. Therefore, the main objective of this study was to apply and evaluate a recently established fish gill EROD assay as a biomarker in sediment toxicity assessment by using extracts of well characterised sediment samples from the upper Danube River. This to our knowledge is the first application of this novel assay to sediment extracts. Sediments from four different sites along the upper Danube River were Soxhlet-extracted with acetone and dissolved in DMSO. Three-spined sticklebacks (Gasterosteus aculeatus L.) were exposed for 48 h to various concentrations of the extracts, to the positive control β-naphthoflavone or to the solvent. Measurements of EROD activity in gill filaments and liver microsomes followed the exposure. Concentration-dependent induction of EROD in both gill and liver was found for all sediment extracts. The highest EROD-inducing potency was determined for extracts of sediments from the sites “Öpfinger See” and “Sigmaringen” and the EROD activities in gill and liver correlated well. The results from the gill and liver assays were in accordance with in vitro results of previous investigations. The EROD activities measured in the present study corresponded with the concentrations of PAHs, PCBs and PCDD/Fs in the sediment samples derived in a previous study. The sticklebacks in this study were in the reproductive phase and a stronger EROD induction was obtained in the females than in the males. Implementation of the EROD assay in testing of sediment extracts gave highly reliable results which make this assay an ecotoxicologically relevant method for assessment of contamination with Ah receptor agonists in sediments.
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| 2. |
- Rickaby, Rosalind E. M., et al.
(författare)
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Perturbing phytoplankton : response and isotopic fractionation with changing carbonate chemistry in two coccolithophore species
- 2010
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Ingår i: Climate of the Past. - : Copernicus Publications on behalf of the European Geosciences Union. - 1814-9324 .- 1814-9332. ; 6, s. 771-785
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Tidskriftsartikel (refereegranskat)abstract
- All species of coccolithophore appear to respond to perturbations of carbonate chemistry in a different way. Here, we show that the degree of malformation, growthrate and stable isotopic composition of organic matter and carbonate produced by two contrasting species of coccolithophore (Gephyrocapsa oceanica and Coccolithus pelagicusssp. braarudii) are indicative of differences between their photosynthetic and calcification response to changing DIC levels (ranging from 1100 to 7800 μmol kg−1) at constant pH (8.13±0.02). Gephyrocapsa oceanica thrived under all conditions of DIC, showing evidence of increased growth rates at higher DIC, but C. braarudii was detrimentally affected at high DIC showing signs of malformation, and decreased growth rates. The carbon isotopic fractionation into organic matter and the coccoliths suggests that C. braarudii utilises a common internal pool of carbon for calcification and photosynthesis but G. oceanica relies on independent supplies for each process. All coccolithophores appear to utilize bicarbonate as their ultimate source of carbon for calcification resulting in the release of a proton. But, we suggest that this proton can be harnessed to enhance the supply of CO2(aq) for photosynthesis either from a large internal HCO−3 pool which acts as a pH buffer (C. braarudii), or pumped externally to aid the diffusive supply of CO2 across the membrane from the abundant HCO−3 (G. oceanica), likely mediated by an internal and external carbonic anhydrase respectively. Our simplified hypothetical spectrum of physiologies may provide a context to understand different species response to changing pH and DIC, the species specific Ep and calcite “vital effects”, as well as accounting for geological trends in coccolithophore cell size.
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| 3. |
- Geibe, Christine, et al.
(författare)
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Comparison of soil solution chemistry sampled by centrifugation, two types of suction lysimeters and zero-tension lysimeters
- 2006
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Ingår i: Applied Geochemistry. - : Elsevier BV. - 0883-2927 .- 1872-9134. ; 21:12, s. 2096-2111
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Tidskriftsartikel (refereegranskat)abstract
- The choice of sampling method for soil solution is of great importance. In this paper soil solution chemistry sampled by centrifugation, two types of suction lysimeters and zero-tension lysimeters have been studied with the purpose of investigating systematic differences between them. The samples were taken at 4 depths from an acidified forest soil as well as from adjacent lime and ash treated soils. A centrifugation drainage method was compared with two types of suction lysimeters ('Rhizon' and 'Prenart') and zero-tension lysimeters. About half of the 27 variables measured showed a significant difference between the sampling methods used. Typically the centrifuged samples had lower pH (4.0 vs. 4.4), Ca (21 mu M vs. 30 mu M) and Mg (25 mu M vs. 34 mu M) concentrations and higher CI (330 mu M vs. 230 mu M) and DOC (4.4 mM vs. 3.2 mM) concentrations than the Rhizon lysimeters. Also the other lysimeters showed significant differences compared to the centrifuged samples for about half the number of analytes. Centrifuged samples had higher concentrations of all analytes except NO3 and PO4 compared to zero-tension lysimeters and also for all analytes except NO3 and Al compared to Prenart lysimeters. Among the environmental factors considered depth showed an influence to some extent, while sampling occasion had a great significant impact on the difference between the centrifugation method and the Rhizon lysimeters. Factors like individual pits or soil treatment did not show any influence on the difference between the methods. (c) 2006 Elsevier Ltd. All rights reserved.
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| 4. |
- Ahlgren, Joakim, et al.
(författare)
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Biogenic phosphorus in oligotropic mountain lake sediments: Differences in composition measured with NMR spectroscopy
- 2006
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Ingår i: Water Research. - Uppsala Univ, Dept Phys & Analyt Chem, S-75124 Uppsala, Sweden. Univ So Denmark, Inst Biol, DK-5230 Odense M, Denmark. Uppsala Univ, Dept Organ & Biol Chem, S-75123 Uppsala, Sweden. Uppsala Univ, Dept Ecol & Evolut, EBC, S-75236 Uppsala, Sweden. : Elsevier BV. - 0043-1354 .- 1879-2448. ; :40, s. 3705-3712
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Tidskriftsartikel (refereegranskat)
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| 5. |
- Asp, Vendela, et al.
(författare)
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Chiral effects in adrenocorticolytic action of o,p'-DDD (mitotane) in human adrenal cells
- 2010
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Ingår i: Xenobiotica. - : Informa UK Limited. - 0049-8254 .- 1366-5928. ; 40:3, s. 177-183
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Tidskriftsartikel (refereegranskat)abstract
- 1. Adrenocortical carcinoma (ACC) is a rare malignant disease with poor prognosis. The main pharmacological choice, o,p'-DDD (mitotane), produces severe adverse effects. 2. Since o,p'-DDD is a chiral molecule and stereoisomers frequently possess different pharmacokinetic and/or pharmacodynamic properties, we isolated the two o,p'-DDD enantiomers, (R)-(+)-o,p'-DDD and (S)-(-)-o,p'-DDD, and determined their absolute structures. 3. The effects of each enantiomer on cell viability and on cortisol and dehydroepiandrosterone (DHEA) secretion in the human adrenocortical cell line H295R were assessed. We also assayed the o, p'-DDD racemate and the m,p'- and p,p'-isomers. 4. The results show small but statistically significant differences in activity of the o, p'-DDD enantiomers for all parameters tested. The three DDD isomers were equally potent in decreasing cell viability, but p, p'- DDD affected hormone secretion slightly less than the o,p'- and m,p'-isomers. 5. The small chiral differences in direct effects on target cells alone do not warrant single enantiomer administration, but might reach importance in conjunction with possible stereochemical effects on pharmacokinetic processes in vivo.
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| 6. |
- Carrod, Andrew J., 1994, et al.
(författare)
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Recent advances in triplet-triplet annihilation upconversion and singlet fission, towards solar energy applications
- 2022
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Ingår i: Energy & Environmental Science. - : Royal Society of Chemistry (RSC). - 1754-5692 .- 1754-5706. ; 15, s. 4982-5016
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Forskningsöversikt (refereegranskat)abstract
- Solar energy is an ample renewable energy resource, with photovoltaic (PV) technology enabling a direct route from light to electricity. Currently, PVs are limited in photon conversion efficiency, due in major part to spectral losses. Mitigation of these losses is therefore important, economically and environmentally. Two processes that aim to increase solar light utilisation are described herein. The first is triplet-triplet annihilation upconversion (TTA-UC), through which two incoherent photons of low energy can produce one of higher energy, reducing below bandgap losses. Secondly, singlet fission (SF), through which two triplet states may be obtained from one initial singlet excited state, in theory allowing two electrons per photon in a PV, reducing thermalisation losses. These fields are often covered seperately, despite being the reverse processes of one another. This work aims to consolidate research in the two fields and highlight their similarities and common challenges, specifically those relevant to PV applications. Herein, we cover systems primarily based on organic small molecules (anthracene, rubrene, tetracene, pentacene), and detail the fabrication of functional materials containing them (MOFs, gels, SAMs on TiO2, thin evaporated and solution cast films, and cavities). We further offer our recommendations for the focus of future work in both the TTA and SF fields, and discuss the need to address current limitations such as poor triplet diffusion, limited charge injection to PVs, and material stability. Specifically, one could do this by cherry picking ideas from other research fields, for example photosensitisers for photodynamic therapy could be used as TTA sensitisers, and molecules having a considerable excited state aromaticity could be considered as SF materials. We hope this review may aid development towards the end goal of an efficient PV, incorporating either, or both, SF and TTA-UC materials.
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| 7. |
- Temnerud, Johan, et al.
(författare)
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Spatial patterns of some trace elements in four Swedish stream networks
- 2013
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Ingår i: Biogeosciences. - : Copernicus GmbH. - 1726-4170 .- 1726-4189. ; 10, s. 1407-1423
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Tidskriftsartikel (refereegranskat)abstract
- Four river basins in southern Sweden, with catchment sizes from 0.3 to 127 km(2) (median 1.9), were sampled in October 2007. The 243 samples were analysed for 26 trace elements (Ag, As, Au, Ba, Be, Bi, Cd, Co, Cr, Cu, Ga, Ge, In, La, Li, Mo, Ni, Pb, Sb, Se, Sn, Tl, Ti, U, V and Zn) to identify spatial patterns within drainage networks. The range and median of each element were defined for different stream orders, and relationships to catchment characteristics, including deposition history, were explored. The sampling design made it possible to compare the differences along 40 stream reaches, above and below 53 stream junctions with 107 tributaries and between the 77 inlets and outlets of 36 lakes. The largest concentration differences (at reaches, junctions and lakes) were observed for lakes, with outlets usually having lower concentration compared to the inlets for As, Ba, Be, Bi, Cd, Co, Cr, Ga, Ge, Ni, Pb, Sn, Ti, Tl, U, V and Zn. Significantly lower concentrations were observed for Cd and Co when comparing headwaters with downstream sites in each catchment. Common factor analysis (FA) revealed that As, Bi, Cr, Ga, Ge, Tl and V co-vary positively with Al, Fe and total organic carbon (TOC) and negatively with La, Li and pH. The strong removal of a large number of trace elements when passing through lakes is evident though in the FA, where lake surface coverage plots opposite to many of those elements. Forest volume does not respond in a similar systematic fashion and, surprisingly, the amount of wetland does not relate strongly to either Fe or TOC at any of the rivers. A better understanding of the quantitative removal of organic carbon and iron will aid in understanding trace element fluxes from landscapes rich in organic matter and iron.
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| 8. |
- Kvashnina, K., et al.
(författare)
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Electron transfer during selenium reduction by iron surfaces in aqueous solution: high resolution X-ray absorption study
- 2009
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Ingår i: Journal of Physics, Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 190:012191, s. 1-4
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Tidskriftsartikel (refereegranskat)abstract
- In several designs proposed by different countries, high-level radioactive waste will be disposed in a canister with a copper outer container and a cast iron or carbon steel insert. If the iron insert comes into contact with anoxic geological water, anaerobic corrosion could take place and release fission products such as 79Se to the biosphere. This paper present studies of the long-term kinetics of selenate (SeO42-) in the presence of iron surface under anaerobic conditions by Near Edge X-ray Absorption Spectroscopy (XANES). Substantial changes in the selenium oxidation state is found and discussed in details. We assume that such behaviour corresponds to the electron transfer from iron to selenium, which couldn't take place on oxidized iron surface. When selenate was in contact with polish steel foil in groundwater solution, reduction of Se and formation of Se(II-)was found. These findings suggest that depending of corroded or oxidised iron surface, the selenium mobility in nuclear waste disposal systems will be different.
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| 9. |
- Berastegui, Pedro, et al.
(författare)
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Electrochemical reactions of AgFeO2 as negative electrode in Li- and Na-ion batteries
- 2018
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Ingår i: Journal of Power Sources. - : Elsevier. - 0378-7753 .- 1873-2755. ; 401, s. 386-396
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Tidskriftsartikel (refereegranskat)abstract
- AgFeO2 nanoparticles synthesized via precipitation at room temperature are investigated in Li- and Na-ion cells through electrode coatings with an alginate binder. The electrochemical reactions of AgFeO2 with Li+ and Na+ions, as well as its role as alternative negative electrode in these cell systems are carefully evaluated. Initial Li uptake causes irreversible amorphization of the AgFeO2 structure with concomitant formation of Ag0 nanoparticles. Further Li incorporation results in conversion into Fe0 nanoparticles and Li2O, together with Li-alloying of these Ag0 clusters. Similar mechanisms are also found upon Na uptake, although such processes are hindered by overpotentials, the capacity and reversibility of the reactions with Na+ ions being not comparablewith those of their Li+ counterparts. The behaviour of AgFeO2 at low potentials vs. Li+/Li displays a synergic pseudo-capacitive charge storage overlapping Li-Ag alloying/de-alloying. This feature is exploited in full cells having deeply lithiated AgFeO2 and LiFePO4 as negative and positive electrodes, respectively. These environmentally friendly iron-based full cells exhibit attractive cycle performances with ≈80% capacity retention after 1000 cycles without any electrolyte additive, average round trip efficiency of ≈89% and operational voltage of 3.0 V combined with built-in pseudo-capacitive characteristics that enable high cycling rates up to≈25C.
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| 10. |
- Capo, Eric, et al.
(författare)
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Expression Levels of hgcAB Genes and Mercury Availability Jointly Explain Methylmercury Formation in Stratified Brackish Waters
- 2022
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 56:18, s. 13119-13130
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Tidskriftsartikel (refereegranskat)abstract
- Neurotoxic methylmercury (MeHg) is formed by microbial methylation of inorganic divalent Hg (Hg-II) and constitutes severe environmental and human health risks. The methylation is enabled by hgcA and hgcB genes, but it is not know nif the associated molecular-level processes are rate-limiting or enable accurate prediction of MeHg formation in nature. In this study, we investigated the relationships between hgc genes and MeHg across redox-stratified water columns in the brackish Baltic Sea. We showed, for the first time, that hgc transcript abundance and the concentration of dissolved Hg-II-sulfide species were strong predictors of both the Hg-II methylation rate and MeHg concentration, implying their roles as principal joint drivers of MeHg formation in these systems. Additionally, we characterized the metabolic capacities of hgc(+) microorganisms by reconstructing their genomes from metagenomes (i.e., hgc(+) MAGs), which highlighted the versatility of putative Hg-II methylators in the water column of the Baltic Sea. In establishing relationships between hgc transcripts and the Hg-II methylation rate, we advance the fundamental understanding of mechanistic principles governing MeHg formation in nature and enable refined predictions of MeHg levels in coastal seas in response to the accelerating spread of oxygen-deficientzones.
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