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  • 1. Ahlgren, Joakim
    et al.
    De Brabandere, Heidi
    Reitzel, Kasper
    Rydin, Emil
    Gogoll, Adolf
    Waldeback, Monica
    Sediment phosphorus extractants for phosphorus-31 nuclear magnetic resonance analysis: A quantitative evaluation2007In: Journal of Environmental Quality, ISSN 0047-2425, E-ISSN 1537-2537, Vol. 36, no 3, p. 892-898Article in journal (Refereed)
    Abstract [en]

    The influence of pre-extractant, extractant, and post-extractant on total extracted amounts of P and organic P compound groups measured with 31 P nuclear magnetic resonance (P-31-NMR) in lacustrine sediment was examined. The main extractants investigated were sodium hydroxide (NaOH) and sodium hydroxide ethylenediaminetetraacetic acid (NaOH-EDTA) with bicarbonate buffered dithionite (BD) or EDTA as pre-extractants. Post extractions were conducted using either NaOH or NaOH-EDTA, depending on the main extractant. Results showed that the most efficient combination of extractants for total P yield was NaOH with EDTA as pre-extractant, yielding almost 50% more than the second best procedure. The P compound groups varying the most between the different extraction procedures were polyphosphates and pyrophosphates. NaOH with BD as pre-extractant was the most efficient combination for these compound groups.

  • 2. Ahlgren, Joakim
    et al.
    Djodjic, Faruk
    Borjesson, G.
    Mattsson, L.
    Identification and quantification of organic phosphorus forms in soils from fertility experiments2013In: Soil use and management, ISSN 0266-0032, E-ISSN 1475-2743, Vol. 29, p. 24-35Article in journal (Refereed)
    Abstract [en]

    The effects of soil type, crop rotation, fertilizer type and application rate on the composition of organic phosphorus (P) compounds in soils from four sites in a Swedish long-term fertilizer experiment were investigated with 31P-NMR. Soil textures investigated were loamy sand, sandy loam, silty clay loam and clay. Phosphorus has been added to the soils since the 1950s and 1960s at four different rates in the form of either mineral fertilizer or a combination of manure and mineral fertilizer. Results show that in soils receiving no P addition, most of the soil P was present in the form of phosphate monoesters (6070%, depending on soil type). However, a P addition equivalent to the amount of P removed annually by harvest altered this relationship so that the soils were dominated by orthophosphate instead. This trend became more obvious with increasing P addition. At the greatest P application rate, orthophosphate comprised 70% or more of the total extracted P in all the soils. These changes in the soil were due entirely to increase in orthophosphate, because the amounts of monoesters did not change with increasing P additions. This was true both for mineral fertilizer and the combination of manure and mineral fertilizer P. Soil type and crop rotation did not influence the results. The results indicate that there is no apparent build-up of organic P in the soils, but that P addition mainly affects the orthophosphate amounts in the soils regardless of form or amount of fertilizer.

  • 3. Ahlgren, Joakim
    et al.
    Djodjic, Faruk
    Wallin, Mats
    Barium as a Potential Indicator of Phosphorus in Agricultural Runoff2012In: Journal of Environmental Quality, ISSN 0047-2425, E-ISSN 1537-2537, Vol. 41, no 1, p. 208-216Article in journal (Refereed)
    Abstract [en]

    In many catchments, anthropogenic input of contaminants, and in particular phosphorus (P), into surface water is a mixture of agricultural and sewage runoff. Knowledge about the relative contribution from each of these sources is vital for mitigation of major environmental problems such as eutrophication. In this study, we investigated whether the distribution of trace elements in surface waters can be used to trace the contamination source. Water from three groups of streams was investigated: streams influenced only by agricultural runoff, streams influenced mainly by sewage runoff, and reference streams. Samples were collected at different flow regimes and times of year and analyzed for 62 elements using ICP-MS. Our results show that there are significant differences between the anthropogenic sources affecting the streams in terms of total element composition and individual elements, indicating that the method has the potential to trace anthropogenic impact on surface waters. The elements that show significant differences between sources are strontium (p < 0.001), calcium (p < 0.004), potassium (p < 0.001), magnesium (p < 0.001), boron (p < 0.001), rhodium (p = 0.001), and barium (p < 0.001). According to this study, barium shows the greatest potential as a tracer for an individual source of anthropogenic input to surface waters. We observed a strong relationship between barium and total P in the investigated samples (R-2 = 0.78), which could potentially be used to apportion anthropogenic sources of P and thereby facilitate targeting of mitigation practices.

  • 4.
    Ahlgren, Joakim
    et al.
    Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF). The Swedish Institute for the Marine Environment, PO Box 260, SE-40530 Göteborg, Sweden.
    Grimvall, Anders
    Omstedt, Anders
    Rolff, Carl
    Wikner, Johan
    Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF). The Swedish Institute for the Marine Environment, PO Box 260, SE-40530 Göteborg, Sweden.
    Temperature, DOC level and basin interactions explain the declining oxygen concentrations in the Bothnian Sea2017In: Journal of Marine Systems, ISSN 0924-7963, E-ISSN 1879-1573, Vol. 170, p. 22-30Article in journal (Refereed)
    Abstract [en]

    Hypoxia and oxygen deficient zones are expanding worldwide. To properly manage this deterioration of the marine environment, it is important to identify the causes of oxygen declines and the influence of anthropogenic activities. Here, we provide a study aiming to explain the declining oxygen levels in the deep waters of the Bothnian Sea over the past 20 years by investigating data from environmental monitoring programmes. The observed decline in oxygen concentrations in deep waters was found to be primarily a consequence of water temperature increase and partly caused by an increase in dissolved organic carbon (DOC) in the seawater (R-Adj(2). = 0.83) as well as inflow from the adjacent sea basin. As none of the tested eutrophication-related predictors were significant according to a stepwise multiple regression, a regional increase in nutrient inputs to the area is unlikely to explain a significant portion of the oxygen decline. Based on the findings of this study, preventing the development of anoxia in the deep water of the Bothnian Sea is dependent on the large-scale measures taken to reduce climate change. In addition, the reduction of the nutrient load to the Baltic Proper is required to counteract the development of hypoxic and phosphate-rich water in the Baltic Proper, which can form deep water in the Bothnian Sea. The relative importance of these sources to oxygen consumption is difficult to determine from the available data, but the results clearly demonstrate the importance of climate related factors such as temperature, DOC and inflow from adjacent basins for the oxygen status of the sea.

  • 5. Ahlgren, Joakim
    et al.
    Reitzel, Kasper
    Danielsson, Rolf
    Gogoll, Adolf
    Rydin, Emil
    Biogenic phosphorus in oligotrophic mountain lake sediments: Differences in composition measured with NMR spectroscopy2006In: Water Research, ISSN 0043-1354, E-ISSN 1879-2448, Vol. 40, no 20, p. 3705-3712Article in journal (Refereed)
    Abstract [en]

    Phosphorus (P) composition in alkaline sediment extracts from three Swedish oligotrophic mountain lakes was investigated using P-31-NMR spectroscopy. Surface sediments from one natural lake and two mature reservoirs, one of which has received nutrient additions over the last 3 years, were compared with respect to biogenic P composition. The results show significant differences in the occurrence of labile and biogenic P species in the sediments of the different systems. The P compound groups that varied most between these three systems were pyrophosphate and polyphosphates, compound groups known to play an important role in sediment P recycling. The content of these compound groups was lowest in the reservoirs and may indicate a coupling between anthropogenic disturbances (i.e., impoundment) to a water system and the availability of labile P species in the sediment. A statistical study was also conducted to determine the accuracy and reliability of using P-31-NMR spectroscopy for quantification of sediment P forms. (c) 2006 Elsevier Ltd. All rights reserved.

  • 6. Ahlgren, Joakim
    et al.
    Reitzel, Kasper
    De Brabandere, Heidi
    Gogoll, Adolf
    Rydin, Emil
    Release of organic P forms from lake sediments2011In: Water Research, ISSN 0043-1354, E-ISSN 1879-2448, Vol. 45, no 2, p. 565-572Article in journal (Refereed)
    Abstract [en]

    The effects of different physical and chemical conditions on the decomposition and release of organic and inorganic P compound groups from the sediment of Lake Erken were investigated in a series of laboratory experiments. Conditions investigated were temperature, oxygen level, and the effects of additions of carbon substrate (glucose) and poison (formalin). The effects on the P compound groups were determined by measurements with (31)P NMR before and after the experiments, as well as analysis of P in effluent water throughout the experiment. Phosphate analysis of the effluent water showed that oxygen level was the most influential in terms of release rates, with the sediments under anoxic conditions generally releasing more phosphate than the other treatments. (31)P NMR showed that the various treatments did influence the P compound group composition of the sediment. In particular, the addition of glucose led to a decrease in orthophosphate and polyphosphate while the addition of formalin led to a decrease in phosphorus lipids, DNA-phosphate and polyphosphate. Oxic conditions resulted in an increase in polyphosphates, and anoxic conditions in a decrease in these. Temperature did not seem to affect the composition significantly. (c) 2010 Elsevier Ltd. All rights reserved.

  • 7. Ahlgren, Joakim
    et al.
    Reitzel, Kasper
    Tranvik, Lars
    Gogoll, Adolf
    Rydin, Emil
    Degradation of organic phosphorus compounds in anoxic Baltic Sea sediments: A P-31 nuclear magnetic resonance study2006In: Limnology and Oceanography, ISSN 0024-3590, E-ISSN 1939-5590, Vol. 51, no 5, p. 2341-2348Article in journal (Refereed)
    Abstract [en]

    The composition and abundance of phosphorus extracted by NaOH-ethylenediaminetetraacetic acid from anoxic Northwest Baltic Sea sediment was characterized and quantified using solution P-31 nuclear magnetic resonance. Extracts from sediment depths down to 55 cm, representing 85 yr of deposition, contained 18.5 g m(-2) orthophosphate. Orthophosphate monoesters, teichoic acid P, microbial P lipids, DNA P, and pyrophosphate corresponded to 6.7, 0.3, 1.1, 3.0, and 0.03 g P m(-2), respectively. The degradability of these compound groups was estimated by their decline in concentration with sediment depth. Pyrophosphate had the shortest half-life (3 yr), followed by microbial P lipids with a half-life of 5 yr, DNA P (8 yr), and orthophosphate monoesters (16 yr). No decline in concentration with sediment depth was observed for orthophosphate or teichoic acid P.

  • 8.
    Ahlgren, Joakim
    et al.
    Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF). Havsmiljöinstitutet.
    Rolff, Carl
    Stockholms universitet.
    Grimvall, Anders
    Havsmiljöinstitutet.
    Omstedt, Anders
    Göteborgs universitet.
    Wikner, Johan
    Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF). Havsmiljöinstitutet.
    Orsaker till minskande syrehalter i Bottenhavet2017Report (Refereed)
    Abstract [sv]

    Resultat från den nationella miljöövervakningen visar att syrehalterna i Bottenhavet har minskat sedan 1970-talet, en minskning som accelererat från 1990. För att ha möjlighet att på något sätt kunna åtgärda denna försämring av den marina miljön är det nödvändigt att identifiera orsakerna till denna syreminskning, eftersom olika orsaker kan kräva olika former av åtgärder. Om orsaken till exempel är ökad syreförbrukning beroende på regional övergödning, skulle detta innebära ökat behov av regionala reningsåtgärder. Målsättningen med projektet var därmed att ge en tillförlitlig förklaring till de sjunkande syrehalterna i Bottenhavet under de senaste 20 åren genom att använda data från de nationella miljöövervakningsprogrammen. De huvudhypoteser som undersöktes som orsaker till de sjunkande syrehalterna var:  • Ökad regional gödning av Bottenhavet och därmed ökad produktion.  • Tillförsel av syrefattigt och fosfatrikt från Egentliga Östersjön.  • Starkare haloklin och försämrad ventilation av Bottenhavets djupvatten.  • Ökad temperatur och ökad tillförsel av löst organiskt kol. Analys av tidsserier och modellanalyser utifrån miljöövervaknings- och forskningsdata visade att den observerade syrehaltsminskningen i Bottenhavets djupvatten främst beror på en ökning av vattentemperaturen och delvis på en ökning av löst organiskt kol i vattnet, samt tillflöde från Egentliga Östersjön. Dataanalysen visade däremot inget tydligt stöd för att ökad produktion av biomassa i Bottenhavet orsakat de minskande syrehalterna. Detta gäller indikatorer för växtplankton, sedimentation och bakterieplankton som alla förväntas öka vid ökad produktion och det finns således inga direkta indicier för att stödja hypotesen om ökad gödning av Bottenhavet.  Sammantaget visar de analyser som gjorts inom projektet att Bottenhavets framtida hälsa främst gynnas av en kombination av åtgärder för att motverka globala klimatförändringar, samt åtgärder för att förbättra vattenkvaliteten i Egentliga Östersjön. Näringstillförsel från Bottenhavets avrinningsområden bedöms främst ha haft betydelse för syresituationen i kustnära vattenförekomster. Den bedöms därför inte i betydande omfattning ha orsakat de minskande syrehalterna i Bottenhavets utsjöområden.  

  • 9. Ahlgren, Joakim
    et al.
    Tranvik, L
    Gogoll, A
    Waldeback, M
    Markides, K
    Rydin, E
    Sediment depth attenuation of biogenic phosphorus compounds measured by P-31 NMR2005In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 39, no 3, p. 867-872Article in journal (Refereed)
    Abstract [en]

    Being a major cause of eutrophication and subsequent loss of water quality, the turnover of phosphorus (P) in lake sediments is in need of deeper understanding. A major part of the flux of P to eutrophic lake sediments is organically bound or of biogenic origin. This P is incorporated in a poorly described mixture of autochthonous and allochthonous sediment and forms the primary storage of P available for recycling to the water column, thus regulating lake trophic status. To identify and quantify biogenic sediment P and assess its lability, we analyzed sediment cores from Lake Erken, Sweden, using traditional P fractionation, and in parallel, NaOH extracts were analyzed using (31)p NMR. The surface sediments contain orthophosphates (ortho-P) and pyrophosphates (pyro-P), as well as phosphate mono- and diesters. The first group of compounds to disappear with increased sediment depth is pyrophosphate, followed by a steady decline of the different ester compounds. Estimated half-life times of these compound groups are about 10 yr for pyrophosphate and 2 decades for mono- and diesters. Probably, these compounds will be mineralized to ortho-P and is thus potentially available for recycling to the water column, supporting further growth of phytoplankton. In conclusion, P-31 NMR is a useful tool to asses the bioavailability of certain P compound groups, and the combination with traditional fractionation techniques makes quantification possible.

  • 10. De Brabandere, Heidi
    et al.
    Danielsson, Rolf
    Sjoberg, Per J. R.
    Ahlgren, Joakim
    Rydin, Emil
    Waldeback, Monica
    Sediment extraction and clean-up for organic phosphorus analysis by electrospray ionization tandem mass spectrometry2008In: Talanta: The International Journal of Pure and Applied Analytical Chemistry, ISSN 0039-9140, E-ISSN 1873-3573, Vol. 74, no 5, p. 1175-1183Article in journal (Refereed)
    Abstract [en]

    A method to prepare NaOH sediment extracts for organic P compound analysis with electrospray ionization tandem mass spectrometry (ESI-MS-MS) was developed on natural samples. Ion exchange, rotary evaporation and mass cut-off filtering proved to be suitable for sample preparation. Samples were analyzed with ESI-MS-MS, and reproducibility and repeatability of the method was calculated. In addition, P-31-nuclear magnetic resonance Spectroscopy (P-31 NMR)was used to measure recovery of different P compound groups such as orthophosphate (Ortho-P), orthophosphate monoesters (Monoester-P), orthophosphate diesters (Diester-P) and pyrophosphates (Pyro-P). The developed sample preparation method resulted in an easy-to-spray liquid for the ESI-MS-MS instrumentation. The overall P recovery was 65% and P-31 NMR showed that Diester-P, possibly in the form of DNA, was apparently lost through the filtering step most likely due to their size. Variances in the total intensities of the MS scans (relative standard deviation (R.S.D.) 35-54%) were for about 50% due to repeated MS runs. Covariances of the peaks in the MS spectra were calculated to be for about 30% due to the sample preparation procedure. Finally, with the ESI-MS-MS approach, 11 peaks in the mass spectra were found likely to represent phosphate containing compounds. (c) 2007 Elsevier B.V. All rights reserved.

  • 11. Reitzel, Kasper
    et al.
    Ahlgren, Joakim
    DeBrabandere, Heidi
    Waldeback, Monica
    Gogoll, Adolf
    Tranvik, Lars
    Rydin, Emil
    Degradation rates of organic phosphorus in lake sediment2007In: Biogeochemistry, ISSN 0168-2563, E-ISSN 1573-515X, Vol. 82, no 1, p. 15-28Article in journal (Refereed)
    Abstract [en]

    Phosphorus (P) binding groups were identified in phytoplankton, settling particles, and sediment profiles by P-31 NMR spectroscopy from the Swedish mesotrophic Lake Erken. The P-31 NMR analysis revealed that polyphosphates and pyrophosphates were abundant in the water column, but rapidly mineralized in the sediment. Orthophosphate monoesters and teichoic acids degraded more slowly than DNA-P, polyphosphates, and P lipids. Humic acids and organic acids from phytoplankton were precipitated from the NaOH extract by acidification and identified by P-31 NMR spectroscopy. The precipitated P was significantly more recalcitrant than the P compound groups remaining in solution, but does not constitute a major sink of P as it did not reach a stable concentration with depth, which indicates that it may eventually be degraded. Since P also precipitated from phytoplankton, the origin of humic-P can not be related solely to allochthonous P.

  • 12. Reitzel, Kasper
    et al.
    Ahlgren, Joakim
    Gogoll, Adolf
    Jensen, Henning S.
    Rydin, Emil
    Characterization of phosphorus in sequential extracts from lake sediments using P-31 nuclear magnetic resonance spectroscopy2006In: Canadian Journal of Fisheries and Aquatic Sciences, ISSN 0706-652X, E-ISSN 1205-7533, Vol. 63, no 8, p. 1686-1699Article in journal (Refereed)
    Abstract [en]

    Phosphorus (P) compounds in three different lake surface sediments were extracted by sequential P extraction and identified by P-31 nuclear magnetic resonance (P-31 NMR) spectroscopy. The extraction procedure primarily discriminates between inorganic P-binding sites but most extraction steps also contained P not reacting (nrP) with the molybdenum complex during P analyses. In all three lakes, the nrP dominated in the NaOH extracts. Nonreactive P from the dystrophic lake was dominated by potentially recalcitrant P groups such as orthophosphate monoesters, while the nrP in the two more productive lakes also contained polyphosphates, pyrophosphate, and organic P groups such as P lipids and DNA-P that may be important in remineralization and recycling to the water column. In addition, polyphosphates showed substantial dynamics in settling seston. The Humic-P pools (P associated with humic acids) showed strong signals of orthophosphate monoesters in all three lakes, which supported the assumption that P-containing humic compounds are indeed recovered in this fraction, although other organic P forms are also present. Thus, in addition to expanding the understanding of which organic P forms that are present in lake sediments, the P-31 NMR technique also demonstrated that the chemical extraction procedure may provide some quantification of recalcitrant versus labile organic P forms.

  • 13. Reitzel, Kasper
    et al.
    Ahlgren, Joakim
    Gogoll, Adolf
    Rydin, Emil
    Effects of aluminum treatment on phosphorus, carbon, and nitrogen distribution in lake sediment: A P-31 NMR study2006In: Water Research, ISSN 0043-1354, E-ISSN 1879-2448, Vol. 40, no 4, p. 647-654Article in journal (Refereed)
    Abstract [en]

    The effects of aluminum (Al) treatment on sediment composition of carbon (C), nitrogen (N) and phosphorus (P) were investigated in sediment representing pre- and post-treatment years in the Danish Lake Sonderby. P-31 NMR spectroscopy analysis of EDTA-NaOH extracts revealed six functional P groups. Direct effects of the Al treatment were reflected in the orthophosphate profile revealing increased amounts of AI-P in the sediment layers representing the post-treatment period, as well as changes in organic P groups due to precipitation of phytoplankton and bacteria at the time of Al addition. Furthermore, changes in phytoplankton community structure and lowered production due to the Al treatment resulted in decreased concentrations of sediment organic P groups and total C. Exponential regressions were used to describe the diagenesis of C, N, and P in the sediment. From these regressions, half-life degradation times and C, N, and P burial rates were determined. (c) 2006 Elsevier Ltd. All rights reserved.

  • 14. Reitzel, Kasper
    et al.
    Ahlgren, Joakim
    Rydin, Emil
    Egemose, Sara
    Turner, Benjamin L.
    Hupfer, Michael
    Diagenesis of settling seston: identity and transformations of organic phosphorus2012In: Journal of Environmental Monitoring, ISSN 1464-0325, E-ISSN 1464-0333, Vol. 14, no 3, p. 1098-1106Article in journal (Refereed)
    Abstract [en]

    Solution (31)phosphorus NMR spectroscopy and sequential fractionation were used to follow diagenetic changes in phosphorus forms during decomposition of settling seston in Lake Nordborg, a shallow eutrophic lake in Denmark. In a decomposition experiment, seston released >60% of their total phosphorus during similar to 50 days incubation, although seston collected during summer contained more phosphorus and released it over a longer period compared to seston collected during spring. Seston decomposition increased concentrations of potentially bioavailable polyphosphate and phosphodiesters, but also promoted the formation of refractory phosphorus forms that might be buried permanently in the sediment. Combining these results with in situ measurements of phosphorus concentrations in lake water and sediment traps revealed that the release from settling seston plays only a minor role in the accumulation of phosphorus in the hypolimnion of Lake Nordborg.

  • 15. Taubald, H.
    et al.
    Tonderski, K.
    Andersson, L.
    Ronnberg, R.
    Ahlgren, J.
    Oxygen isotopes in phosphate as a tracer for sources and pathways of catchment P in stream water2010In: Geochimica et Cosmochimica Acta, ISSN 0016-7037, E-ISSN 1872-9533, Vol. 74, no 12, p. A1030-A1030Article in journal (Other academic)
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