| 1. |
- Laturnus, Frank, 1975-, et al.
(författare)
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Release of reactive organic halogens by the brown macroalga Saccharina latissima after exposure to ultraviolet radiation
- 2010
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Ingår i: Polar Research. - : Norsk polarinstitut Oslo. - 0800-0395 .- 1751-8369. ; 29:3, s. 379-384
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Tidskriftsartikel (refereegranskat)abstract
- The brown macroalga Saccharina latissima (Linnaeus) C.E. Lane, C. Mayes, Druehl & G.W. Saunders (formerly Laminaria saccharina [L.] Lamouroux) was exposed to ultraviolet radiation (UVR) in the mW UV-A and mW UV-B range in the laboratory for up to 28 days. The release rates of volatile organohalogens, such as chloroform, bromoform, dibromomethane and methyl iodide, were determined. From these rates, the total emission of reactive organic halogens was calculated. The results revealed that exposure to UVR significantly affected the emission of reactive organic halogens by the macroalga under investigation. An increase in the release of reactive organic iodine was observed for the algal species. In contrast, for reactive organic bromine and reactive organic chlorine, a decrease in emission by the macroalga was observed. Apparently, the potential for increased levels of UVR resulting from further ongoing destruction of the stratospheric ozone layer may increase the importance of marine macroalgae in atmospheric reactions involving organic halogens.
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| 2. |
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| 3. |
- Bastviken, David, et al.
(författare)
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Chloride retention in forest soil by microbial uptake and by natural chlorination of organic matter
- 2007
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Ingår i: Geochimica Cosmochimica Acta. - : Elsevier BV. - 0016-7037 .- 1872-9533. ; 71:13, s. 3182-3192
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Tidskriftsartikel (refereegranskat)abstract
- Inorganic chlorine (i.e. chloride; Cl-in) is generally considered inert in soil and is often used as a tracer of soil and ground water movements. However, recent studies indicate that substantial retention or release of Cl-in can occur in soil, but the rates and processes responsible under different environmental conditions are largely unknown. We performed Cl-36 tracer experiments which indicated that short-term microbial uptake and release of Cl-in, in combination with more long-term natural formation of chlorinated organic matter (Cl-org), caused Cl-in imbalances in coniferous forest soil. Extensive microbial uptake and release of Cl-in occurred over short time scales, and were probably associated with changes in environmental conditions. Up to 24% of the initially available Clin within pore water was retained by microbial uptake within a week in our experiments, but most of this Cl-in, was released to the pore water again within a month, probably associated with decreasing microbial populations. The natural formation of Clorg resulted in a net immobilization of 4% of the initial pore water Clin over four months. If this rate is representative for the area where soil was collected, Clorg formation would correspond to a conversion of 25% of the yearly wet deposition of Cl-in. The study illustrates the potential of two Clin retaining processes in addition to those previously addressed elsewhere (e.g. uptake of chloride by vegetation). Hence, several processes operating at different time scales and with different regulation mechanisms can cause Clin imbalances in soil. Altogether, the results of the present study (1) provide evidence that Cl-in cannot be assumed to be inert in soil, (2) show that microbial exchange can regulate pore water Cl-in, concentrations and (3) confirm the controversial idea of substantial natural chlorination of soil organic matter.
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| 4. |
- Johansson, Madelaine, et al.
(författare)
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Individual Reflection Paper : Supporting Student's Learning in the Critical Phase of Self-directed Learning in PBL
- 2019
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Ingår i: Journal of Problem Based Learning in Higher Education. - : Aalborg Universitetsforlag. - 2246-0918. ; 7:1, s. 97-106
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Tidskriftsartikel (refereegranskat)abstract
- Supporting and assessment of students’ preparation and learning process in problem-based learning (PBL) tutorials has long been a challenge. We present a modified PBL model focussing on the specific critical phase in the PBL process, the self-directed learning phase in between tutorial meetings. The modified seven step PBL model including an Individual reflection paper (IRP) is presented as well as students’ perspectives on the implementation of IRP and information literacy, knowledge gathering, and PBL tutorial work. The assessment of PBL work is complex, and the ways in which IRPs support the tutor’s role as an examiner is beyond the scope of the current study. However, it seems that the students experienced assessment of the IRPs as part of their as a positive driving force in their learning process.
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| 5. |
- Montelius, Malin, 1984-, et al.
(författare)
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Radiotracer evidence that the rhizosphere is a hot-spot for chlorination of soil organic matter
- 2019
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Ingår i: Plant and Soil. - : Springer. - 0032-079X .- 1573-5036. ; 443:1-2, s. 245-257
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Tidskriftsartikel (refereegranskat)abstract
- AimsThe ubiquitous and extensive natural chlorination of organic matter in soils, leading to levels of chlorinated soil organic matter that often exceed the levels of chloride, remains mysterious in terms of its causes and regulation. While the composition of plant species and the availability of labile organic matter was recently shown to be important, the physical localization of chlorination in soils remains unclear but is a key for understanding regulation and patterns observed. Here we assess the relative importance of organic matter chlorination in (a) bulk soil, (b) the plant roots plus the rhizosphere zone surrounding the roots, and (c) above-ground plant biomass, in an experimental plant-soil system.MethodsA radiotracer, 36Cl, was added to study translocation and transformations of Cl− and Clorg in agricultural soil with and without wheat (Triticum vulgare) over 50 days.ResultsThe specific chlorination rates (the fraction of the added 36Cl− converted to 36Clorg per day) in soil with plants was much higher (0.02 d−1) than without plants (0.0007 d−1) at peak growth (day 25). The plant root and rhizosphere showed much higher formation of 36Clorg than the bulk soil, suggesting that the rhizosphere is a hotspot for chlorination in the soil. In addition, the treatment with plants displayed a rapid and high plant uptake of Cl−.ConclusionsOur results indicate that the rhizosphere harbour the most extensive in-situ chlorination process in soil and that root-soil interaction may be key for terrestrial chlorine cycling.
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| 6. |
- Pickering, Lauren, et al.
(författare)
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Portable Chamber System for Measuring Chloroform Fluxes from Terrestrial Environments – Methodological Challenges
- 2013
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 47:24, s. 14298-14305
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Tidskriftsartikel (refereegranskat)abstract
- This study describes a system designed to measure chloroform flux from terrestrial systems, providing a reliable first assessment of the spatial variability of flux over an area. The study takes into account that the variability of ambient air concentrations is unknown. It includes quality assurance procedures, sensitivity assessments, and testing of materials used to ensure that the flux equation used to extrapolate from concentrations to fluxes is sound and that the system does not act as a sink or a source of chloroform. The results show that many materials and components commonly used in sampling systems designed for CO2, CH4, and N2O emit chloroform and other volatile chlorinated compounds (VOCls) and are thus unsuitable in systems designed for studies of such compounds. To handle the above-mentioned challenges, we designed a system with a non-steady-state chamber and a closed-loop air-circulation unit returning scrubbed air to the chamber. Based on empirical observations, the concentration increase during a deployment was assumed to be linear. Four samples were collected consecutively and a line was fitted to the measured concentrations. The slope of the fitted line and the y-axis intercept were input variables in the equation used to transform concentration change data to flux estimates. The soundness of the flux equation and the underlying assumptions were tested and found to be reliable by comparing modeled and measured concentrations. Fluxes of chloroform in a forest clear-cut on the east coast of Vancouver Island, BC, during the year were found to vary from −130 to 620 ng m–2 h–1. The study shows that the method can reliably detect differences of approximately 50 ng m–2 h–1 in chloroform fluxes. The statistical power of the method is still comparatively strong down to differences of 35 ng m–2 h–1, but for smaller differences, the results should be interpreted with caution.
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| 7. |
- Ryberg, Johanna, et al.
(författare)
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Risk of uterine rupture in multiparous women after induction of labor with prostaglandin: A national population-based cohort study.
- 2024
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Ingår i: International journal of gynaecology and obstetrics: the official organ of the International Federation of Gynaecology and Obstetrics. - 0020-7292 .- 1879-3479. ; 165:1, s. 328-334
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Tidskriftsartikel (refereegranskat)abstract
- To assess whether, after induction of labor with prostaglandin, multiparous (≥2 para) women have an increased risk of uterine rupture compared with nulliparous or uniparous women.This was a retrospective population-based cohort study including women who underwent induction with prostaglandin in all maternity wards in Sweden between May 1996 and December 2019 (n=56784). The study cohort was obtained by using data from the Swedish Medical Birth Register, which contains information from maternity and delivery records. The main outcome measure was uterine rupture.Overall, multiparous women induced with prostaglandin had an increased risk of uterine rupture compared with nulliparous women (adjusted odds ratio [OR], 3.33 [95% confidence interval (CI), 1.38-8.04]; P<0.007). Multiparous women with no previous cesarean section (CS) induced with prostaglandin had more than three times higher risk of uterine rupture (crude OR, 3.55 [95% Cl, 1.48-8.53]; P=0.005) compared with nulliparous women and four times higher risk compared with uniparous women (OR, 4.10 [95% CI, 1.12-15.00]; P<0.033). Multiparous women with previous CS had a decreased risk of uterine rupture compared with uniparous women with one previous CS (crude OR, 0.41 [95% Cl, 0.21-0.78]; P=0.007).Our study implies that multiparity in women with no previous CS is a risk factor for uterine rupture when induced with prostaglandin. This should be taken into consideration when deciding on the appropriate method of induction.
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| 8. |
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| 9. |
- Svensson, Teresia, 1975-, et al.
(författare)
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Chlorination of soil organic matter : The role of humus type and land use
- 2022
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Ingår i: Science of the Total Environment. - : Elsevier. - 0048-9697 .- 1879-1026. ; 806p2
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Tidskriftsartikel (refereegranskat)abstract
- The levels of natural organic chlorine (Clorg) typically exceed levels of chloride in most soils and is therefore clearly of high importance for continental chlorine cycling. The high spatial variability raises questions on soil organic matter (SOM) chlorination rates among topsoils with different types of organic matter. We measured Clorg formation rates along depth profiles in six French temperate soils with similar Cl deposition using 36Cl tracer experiments. Three forest sites with different humus types and soils from grassland and arable land were studied. The highest specific chlorination rates (fraction of chlorine pool transformed to Clorg per time unit) among the forest soils were found in the humus layers. Comparing the forest sites, specific chlorination was highest in mull-type humus, characterized by high microbial activity and fast degradation of the organic matter. Considering non-humus soil layers, grassland and forest soils had similar specific chlorination rates in the uppermost layer (0–10 cm below humus layer). Below this depth the specific chlorination rate decreased slightly in forests, and drastically in the grassland soil. The agricultural soil exhibited the lowest specific chlorination rates, similar along the depth profile. Across all sites, specific chlorination rates were correlated with soil moisture and in combination with the patterns on organic matter types, the results suggest an extensive Cl cycling where humus types and soil moisture provided best conditions for microbial activity. Clorg accumulation and theoretical residence times were not clearly linked to chlorination rates. This indicates intensive Cl cycling between organic and inorganic forms in forest humus layers, regulated by humic matter reactivity and soil moisture, while long-term Clorg accumulation seems more linked with overall deep soil organic carbon stabilization. Thus, humus types and factors affecting soil carbon storage, including vegetation land use, could be used as indicators of potential Clorg formation and accumulation in soils.
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| 10. |
- Svensson, Teresia, 1975-, et al.
(författare)
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Chlorine cycling and the fate of Cl in terrestrial environments
- 2021
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Ingår i: Environmental Science and Pollution Research. - : Springer. - 0944-1344 .- 1614-7499. ; 28:7, s. 7691-7709
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Tidskriftsartikel (refereegranskat)abstract
- Chlorine (Cl) in the terrestrial environment is of interest from multiple perspectives, including the use of chloride as a tracer forwater flow and contaminant transport, organochlorine pollutants, Cl cycling, radioactive waste (radioecology; 36Cl is of largeconcern) and plant science (Cl as essential element for living plants).During the past decades, there has been a rapid developmenttowards improved understanding of the terrestrial Cl cycle. There is a ubiquitous and extensive natural chlorination of organicmatter in terrestrial ecosystems where naturally formed chlorinated organic compounds (Clorg) in soil frequently exceed theabundance of chloride. Chloride dominates import and export from terrestrial ecosystems while soil Clorg and biomass Cl candominate the standing stock Cl. This has important implications for Cl transport, as chloride will enter the Cl pools resulting inprolonged residence times. Clearly, these pools must be considered separately in future monitoring programs addressing Clcycling. Moreover, there are indications that (1) large amounts of Cl can accumulate in biomass, in some cases representing themain Cl pool; (2) emissions of volatile organic chlorines could be a significant export pathway of Cl and (3) that there is aproduction of Clorg in tissues of, e.g. plants and animals and that Cl can accumulate as, e.g. chlorinated fatty acids in organisms.Yet, data focusing on ecosystem perspectives and combined spatiotemporal variability regarding various Cl pools are still scarce,and the processes and ecological roles of the extensive biological Cl cycling are still poorly understood.
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