Seasonal trends and retention of polycyclic aromatic compounds (PACs) in a remote sub-Arctic catchment

Atmospheric deposition is the most dominant source of polycyclic aromatic hydrocarbons (PAHs) in remote and pristine areas. Despite low bioaccumulation potential, PAHs and their persistent transformation products (PAHderivatives) are chemicals of concern as they can harm human and animal health through chronic low dose exposure. In this study, atmospheric deposition fluxes of polycyclic aromatic compounds (PACs) were measured on a seasonal basis (3-month periods) from 2012 to 2016 in a remote subarctic forest catchment in northern Europe. The target PACs included 19 PAHs and 15 PAH-derivatives (oxygenated, nitrogenated, and methylated PAHs). The deposition fluxes of Sigma PAHs and Sigma PAH-derivatives were in the same range and averaged 530 and 500 ng m(2) day(-1), respectively. The fluxes were found to be higher with a factor of 2.5 for Sigma PAHs and a factor of 3 for.PAH-derivatives during cold (10 degrees C) periods. PAHs and PAH-derivatives showed similar seasonal patterns, which suggests that these two compound classes have similar sources and deposition mechanisms, and that the source strength of the Sigma PAH-derivatives in air follows that of the PAHs. The terrestrial export of PACs via the outlet of the catchment stream was estimated to be 1.1% for.PAHs and 1.7% for Sigma PAH-derivatives in relation to the annual amounts deposited to the catchment, which suggests that boreal forests are sinks for PACs derived from the atmosphere. Some individual PACs showed higher export than others (i.e. chrysene, cyclopenta(c,d)pyrene, carbazole, quinoline, and benzo(f)quinoline), with high export PACs mostly characterized by low molecular weight and low hydrophobicity (2-3 benzene rings; log K-ow<6.0)

Seasonal trends of per- and polyfluoroalkyl substances in river water affected by fire training sites and wastewater treatment plants

Fire-fighting training areas and wastewater treatment plants (WWTPs) are potential sources of per- and polyfluoroalkyl substances (PFASs) to the nearby aquatic environment. This study investigated seasonal variations of PFAS levels in two river catchments in Sweden; one impacted by Stockholm Arlanda Airport (Sites 1 and 2), and the other by WWTPs and a military airport (Uppsala) (Sites 3 and 4). Sigma PFAS concentrations were up to 61 (Sites 1 and 2) and 4 (Sites 3 and 4) times higher compared to the reference site. Distinct different seasonal trends were observed in the two catchments with higher Sigma PFAS concentrations during the high water flow season at Site 1 compared to the low water flow season, whereas Sites 3 and 4 showed an inverse seasonal trend. This demonstrates that the pollution is mobilized during periods of high flow in the first catchment (Stockholm Arlanda Airport), while it is diluted during high flow in the second catchment (Uppsala). Average annual loads for Sigma PFASs were estimated at similar to 5.2 and similar to 3.7 kg yr(-1) for the catchment in Uppsala and Stockholm Arlanda Airport, respectively. Thus, both catchments add PFASs to Lake Malaren, which is Sweden's most important source area for drinking water production

Unifying N=5 and N=6

We write the Lagrangian of the general N=5 three-dimensional superconformal Chern-Simons theory, based on a basic Lie superalgebra, in terms of our recently introduced N=5 three-algebras. These include N=6 and N=8 three-algebras as special cases. When we impose an antisymmetry condition on the triple product, the supersymmetry automatically enhances, and the N=5 Lagrangian reduces to that of the well known N=6 theory, including the ABJM and ABJ models.Comment: 19 pages. v2: Published version. Minor typos corrected, references adde

Re-analysis of organic flame retardants in Swedish rivers

Flame retardants (FRs) are used in everyday products such as furniture and electronics to provide fire protection. The intensive use of FRs has led to their wide spread in the environment. Many chemicals have been found to have bioaccumulative, persistent and toxic properties which have led to a ban of some of these FR compounds based on international agreements. For example, Penta- and octa-polybrominated diphenyl ethers (BDEs) have been included in the Stockholm Convention. However, most FRs are not restricted, and in many cases it is not known to which extent they are used or to which degree they are polluting the environment. The aim of this study was to provide a snapshot of the current FR pollution in Swedish rivers and streams. In total, 25 rivers and streams were sampled along the east coast of Sweden from north to south. The sampling was done in October 2013 and results from this pre-study were presented previously (Ahrens et al. 2014). Since then, the analytical method for FRs has been improved, and here we report on the re-analysis of the extracts from the previous study. In total 61 (including 7 PBDEs, 35 AFRs, 19 OPFRs), mainly novel FRs, were included in the analytical method. The highest number of FRs was detected in Nyköpingsån (22) and Indalsälven (16). The most frequently detected FRs were ∑tris(1,3-dichloroisopropyl) phosphate/tris(2-ethylhexyl) phosphate) (ΣTDCIPP/TEHP, quantified as the sum of both) detected in all 25 samples from north to south, followed by tris(2-chloroethyl) phosphate (TCEP) (detected in 15 samples) and tetrabromobisphenol-A (TBBPA) (detected in 11 samples). The highest FR concentrations were observed in Nyköpingsån, Fyrisån and Indalsälven with ∑FR concentrations of 240, 230 and 140 ng L-1, respectively. It is evident that FR concentrations in general are higher in the south than in the north, likely explained by the higher population density in the south. Daily loads of ∑FRs transported from Swedish rivers into the Baltic Sea were estimated to be in total 15 kg/day. Indalsälven and Nyköpingsån showed highest total daily loads with 5.2 and 4.9 kg/day, respectively. The composition profiles of these two rivers showed a similar pattern with 3,4,5,6-Tetrabromophthalic anhydride (TEBP-Anh, ~30% of the ∑FR), Tetrachlorobisphenol-A (TCBPA, ~23% of the ∑FR) and TBBPA (~30% of the ∑FR) as the major FRs indicating that these are the three main FRs transported into the Baltic Sea from Swedish rivers. Since this study only provides a snapshot of current conditions, care needs to be taken in the interpretation of the results. This type of screening study is, however, useful for getting a general idea on pollution levels and revealing of tentative hot spots. For better insight into the pollution situation, another sampling strategy is neded, e.g. covering longer time periods (and different seasons) and using more frequent sampling or time/flow-proportional sampling

Informationskompetens – generella färdigheter för fördjupat lärande

Förmågan att effektivt utnyttja och kritiskt förhålla sig till olika informationsresurser – ”information literacy” eller informationskompetens – är en central färdighet i det moderna samhället. Det utgör också en allt viktigare del av lärandet i högre utbildning. Syftet med detta paper är tvåfaldigt: 1) att problematisera relationen mellan informationskompetens som en generell färdighet och mer specifika ämnesorienterade kunskaper och färdigheter; 2) ge exempel på och utveckla redskap för lärare att på ett ämnesmässigt integrerat sätt arbeta med, utveckla och examinera studenternas informationskompetens. Ett huvudspår i framställningen är att synliggöra hur träningen i informationskompetens kan stimulera och hjälpa studenterna till fördjupade ämneskunskaper

Superconformal M2-branes and generalized Jordan triple systems

Three-dimensional conformal theories with six supersymmetries and SU(4) R-symmetry describing stacks of M2-branes are here proposed to be related to generalized Jordan triple systems. Writing the four-index structure constants in an appropriate form, the Chern-Simons part of the action immediately suggests a connection to such triple systems. In contrast to the previously considered three-algebras, the additional structure of a generalized Jordan triple system is associated to a graded Lie algebra, which corresponds to an extension of the gauge group. In this note we show that the whole theory with six manifest supersymmetries can be naturally expressed in terms of such a graded Lie algebra. Also the BLG theory with eight supersymmetries is included as a special case.Comment: 15 pages, v2 and v3: minor corrections and clarifications, references added, v2: section 4 extended, v3: published versio

The Politics of Foreign Policy Change : Explaining the Swedish Reorientation on EC Membership

This study addresses the problem of foreign policy change. While the 1990s has been characterized by remarkable changes in world affairs, political scientists have been slow to study the processes through which such changes take place. Drawing on the limited research that does exist in this field, the study presents an alternative explanatory model of foreign policy change, arguing that states tend to alter their foreign policy orientations when changes in fundamental structural conditions coincide with strategic political leadership and the presence of a crisis of some kind. This model is then applied to the Swedish government1s decision in October 1990 to restructure its relationship to the West European integration process. The author argues that with the end of the Cold War, the poor prospects in the EEA negotiations and the emerging recession, the basic preconditions for Sweden1s long-standing policy of non-EC membership had been significantly altered. The structural changes in the international and domestic environment were perceived and acted upon by Prime Minister Ingvar Carlsson. Forming an informal coalition with Minister of Finance Allan Larsson, Carlsson launched the policy reorientation in the midst of a severe balance of payments crisis. By redefining Swedish EC membership from a political to an economic issue, he successfully capitalized on the seriousness of the economic situation and marginalized potential opponents to EC membership within the cabinet