| 1. |
- Stepanauskas, Ramunas, et al.
(författare)
-
Bioavailability of wetland-derived DON to freshwater and marine bacterioplankton
- 1999
-
Ingår i: LIMNOLOGY AND OCEANOGRAPHY. - 0024-3590. ; 44:6, s. 1477-1485
-
Tidskriftsartikel (refereegranskat)abstract
- Access to bioavailable nitrogen often limits primary production in marine and freshwater ecosystems. Around 70% of nitrogen transported by rivers worldwide consists of dissolved organic nitrogen (DON), but its bioavailability has been poorly investigated.
|
|
| 2. |
|
|
| 3. |
- Bastviken, S K, et al.
(författare)
-
Potential nitrification and denitrification on different surfaces in a constructed treatment wetland
- 2003
-
Ingår i: Journal of Environmental Quality. - 0047-2425. ; 32:6, s. 2414-2420
-
Tidskriftsartikel (refereegranskat)abstract
- Improved understanding of the importance of different surfaces in supporting attached nitrifying and denitrifying bacteria is essential if we are to optimize the N removal capacity of treatment wetlands. The aim of this study was therefore to examine the nitrifying and denitrifying capacity of different surfaces in a constructed treatment wetland and to assess the relative importance of these surfaces for overall N removal in the wetland. Intact sediment cores, old pine and spruce twigs, shoots of Eurasian watermilfoil (Myriophyllum spicatum L.), and filamentous macro-algae were collected in July and November 1999 in two basins of the wetland system. One of the basins had been constructed on land that contained lots of wood debris, particularly twigs of coniferous trees. Potential nitrification was measured using the isotope-dilution technique, and potential denitrification was determined using the acetylene-inhibition technique in laboratory microcosm incubations. Nitrification rates were highest on the twigs. These rates were three and 100 times higher than in the sediment and on Eurasian watermilfoil, respectively. Potential denitrification rates were highest in the sediment. These rates were three times higher than on the twigs and 40 times higher than on Eurasian watermilfoil. The distribution of denitrifying bacteria was most likely due to the availability of organic material, with higher denitrification rates in the sediment than on surfaces in the water column. Our results indicate that denitrification, and particularly nitrification, in treatment wetlands could be significantly increased by addition of surfaces such as twigs.
|
|
| 4. |
|
|
| 5. |
- Kallner Bastviken, Sofia, et al.
(författare)
-
Potential nitrification and denitrification on different surfaces in a constructed treatment wetland
- 2004
-
Ingår i: Journal of environmental quality. - 0047-2425. ; 32:6, s. 2414-2420
-
Tidskriftsartikel (refereegranskat)abstract
- Improved understanding of the importance of different surfaces in supporting attached nitrifying and denitrifying bacteria is essential if we are to optimize the N removal capacity of treatment wetlands. The aim of this study was therefore to examine the nitrifying and denitrifying capacity of different surfaces in a constructed treatment wetland and to assess the relative importance of these surfaces for overall N removal in the wetland. Intact sediment cores, old pine and spruce twigs, shoots of Eurasian watermilfoil (Myriophyllum spicatum L.), and filamentous macro-algae were collected in July and November 1999 in two basins of the wetland system. One of the basins had been constructed on land that contained lots of wood debris, particularly twigs of coniferous trees. Potential nitrification was measured using the isotope-dilution technique, and potential denitrification was determined using the acetylene-inhibition technique in laboratory microcosm incubations. Nitrification rates were highest on the twigs. These rates were three and 100 times higher than in the sediment and on Eurasian watermilfoil, respectively. Potential denitrification rates were highest in the sediment. These rates were three times higher than on the twigs and 40 times higher than on Eurasian watermilfoil. The distribution of denitrifying bacteria was most likely due to the availability of organic material, with higher denitrification rates in the sediment than on surfaces in the water column. Our results indicate that denitrification, and particularly nitrification, in treatment wetlands could be significantly increased by addition of surfaces such as twigs.
|
|
| 6. |
- Leonardson, L., et al.
(författare)
-
Nitrogen Retention in Artificially Flooded Meadows
- 1994
-
Ingår i: Ambio: a Journal of Human Environment. - 0044-7447. ; 23:6, s. 332-341
-
Tidskriftsartikel (refereegranskat)abstract
- Investigations of nitrogen retention in artificially flooded wetlands were performed in southern Sweden during 1991-1993. The purpose of the study was to investigate whether artificial flooding of meadows would be a possible means of reducing the nitrogen content in streams and rivers. Two case studies are presented, one from a sandy/organic soil, one from a peaty soil. Overall nitrogen retention was estimated by mass balance. Denitrification activity and plant biomass incorporation of nitrogen were used to complement and verify the mass-balance data. The study shows that artificial flooding of meadows did not contribute significantly to nitrogen retention in the introduced river water under the irrigation regimes utilized. The technique stimulated mineralization of the soil nitrogen pool to an extent which corresponded to the reduction of nitrate caused by denitrification. In the sandy/organic soil, denitrification was enhanced by the artificial flooding, while in the peat area the activity was lower than in a nonflooded reference area. Plant uptake of nitrogen was stimulated by flooding.
|
|
| 7. |
- Robroek, Bjorn J. M., et al.
(författare)
-
How nitrogen and sulphur addition, and a single drought event affect root phosphatase activity in Phalaris arundinacea
- 2009
-
Ingår i: Science of the Total Environment. - : Elsevier BV. - 1879-1026 .- 0048-9697. ; 407:7, s. 2342-2348
-
Tidskriftsartikel (refereegranskat)abstract
- Conservation and restoration of fens and fen meadows often aim to reduce soil nutrients, mainly nitrogen (N) andphosphorus (P). The biogeochemistry of P has received much attention as P-enrichment is expected to negatively impact on species diversity in wetlands. It is known that N, sulphur (S) and hydrological conditions affect the biogeochemistry of P, yet their interactive effects on P-dynamics are largely unknown. Additionally, in Europe, climate change has been predicted to lead to increases in summer drought. We performed a greenhouse experiment to elucidate the interactive effects of N, S and a single drought event on the P-availability for Phalaris arundinacea. Additionally, the response of plant phosphatase activity to these factors was measured over the two year experimental period. In contrast to results from earlier experiments, our treatments hardly affected soil P-availability. This may be explained by the higher pH in our soils, hampering the formation of Fe-P or Fe-Al complexes. Addition of S, however, decreased the plants N:P ratio, indicating an effect of S on the N:P stoichiometry and an effect on the plant's P-demand. Phosphatase activity increased significantly after addition of S, but was not affected by the addition of N or a single drought event. Root phosphatase activity was also positively related to plant tissue N and P concentrations, plant N and P uptake, and plant aboveground biomass, suggesting that the phosphatase enzyme influences P-biogeochemistry. Our results demonstrated that it is difficult to predict the effects of wetland restoration, since the involved mechanisms are not fully understood. Short-term and long-term effects on root phosphatase activity may differ considerably. Additionally, the addition of S can lead to unexpected effects on the biogeochemistry of P. Our results showed that natural resource managers should be careful when restoring degraded fens or preventing desiccation of fen ecosystems. (C) 2008 Elsevier B.V. All rights reserved.
|
|
| 8. |
- Stadmark, Johanna, et al.
(författare)
-
Emissions of greenhouse gases from ponds constructed for nitrogen removal
- 2005
-
Ingår i: Ecological Engineering: the Journal of Ecotechnology. - : Elsevier BV. - 1872-6992. ; 25:5, s. 542-551
-
Tidskriftsartikel (refereegranskat)abstract
- Methane and carbon dioxide emission from three constructed ponds were monitored during an annual cycle. Water temperature was a good predictor of methane emission in all three ponds. In the most intensively studied pond, nitrate concentration in the bottom water could further explain the amount of methane emitted. When water temperature exceeded 15 °C between 1 and 54 mg, CH4 m−2 h−1 was emitted on all occasions, while at temperatures below 10 °C, less than 0.6 mg CH4 m−2 h−1 was emitted. The flux of carbon dioxide differed between the ponds and no consistent patterns were found. In a laboratory study at 20 °C, we showed that high, but naturally occurring, nitrate concentrations (8 and 16 mg NO3−–N l−1) constrained the production of methane compared to the treatment with no nitrate addition. Nitrous oxide production was positively correlated with nitrate concentration. Carbon dioxide production was highest at the highest nitrate concentration, which indicates that increased nitrate loading on ponds and wetlands will stimulate organic matter decomposition rates. Our conclusion is that these ponds constructed for nitrate removal emit greenhouse gases comparable to lakes in the temperate region.
|
|
| 9. |
- Stadmark, Johanna, et al.
(författare)
-
Greenhouse gas production in a pond sediment: Effects of temperature, nitrate, acetate and season
- 2007
-
Ingår i: Science of the Total Environment. - : Elsevier BV. - 1879-1026 .- 0048-9697. ; 387:1-3, s. 194-205
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper we investigate the impact of nitrate (NO3-) concentration and temperature on the production of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O). We studied sediment collected during spring, summer and autumn from a constructed pond in South Sweden. Homogenised sediment samples were dark incubated in vitro under N-2 atmosphere at 13 degrees C and 20 degrees C after addition of five NO3- concentrations, between 0 and 16 mg NO3- -N per litre. We found higher net production of N2O and CO, at the higher temperature. Moreover, increased NO3- concentrations had strong positive impact on the N2O3 concentration, but no effect on CH4 and CO2 production. The lack of response in CO2 is suggested to be due to the use of alternative oxidants as electron acceptors. Interaction between NO3- and temperature suggests a further increase of N-2O, net production when both NO3 and temperature are high. Our interpretation of the CH4 data is that at high concentrations of NO3 temperature is of less importance for CH4 production. We also found that at 13 degrees C CH4 production was substrate limited and that the addition of acetate increased CH4 as well as CO2 production. There was a seasonal effect on gas production potential, with more CH4 and NO produced in spring than in summer. Re-calculation of the gas concentrations into global warming potential (GWP) units (i.e. CO2, CH4, and N2O transferred to CO2 equivalents) shows that GWP increases with temperature. However, under environmental conditions generally occurring in South Swedish ponds, i.e. low temperature and high NO3 concentration during spring and high temperature and low NO3 concentration during summer, NO3- concentration is of minor importance. (C) 2007 Elsevier B.V. All rights reserved.
|
|
| 10. |
- Stadmark, Johanna, et al.
(författare)
-
Transforming meadows into free surface water wetlands: Impact of increased nitrate and carbon loading on greenhouse gas production
- 2009
-
Ingår i: Atmospheric Environment. - : Elsevier BV. - 1352-2310. ; 43:6, s. 1182-1188
-
Tidskriftsartikel (refereegranskat)abstract
- In a laboratory study we investigated 1) the potential production of nitrous oxide (N2O), methane (CH4) and carbon dioxide (CO2) and 2) the effect of nitrate (NO3−) and anaerobic N2O development on CH4 production in sediment from a recently recreated free surface water wetland (FSWW) and in soil from an adjacent meadow. We designed an experiment where production of greenhouse gases was registered at the time of maximum net development of N2O. We made additions of biodegradable carbon (glucose) and/or NO3− to sediment and soil slurries and incubated them at four temperatures (4, 13, 20, 28 °C). Gas production from both substrates was positively correlated with temperature. We also found that the sediment produced more N2O than the soil. N2O production in sediment was NO3− limited, whereas in soil carbon availability was lower and only combined additions of NO3− and glucose supported increased N2O development. CH4 production was generally low and did not differ between soil and sediment. Nor did glucose addition increase CH4 rates. The results suggest that neither soil nor sediment environment did support development of methanogenic populations. There were no clear effects of NO3− on CH4 production. However, the highest records of CH4 were found in incubations with low N2O production, which indicates that N2O might be toxic to methanogens. In summary, our study showed that transforming meadows into FSWWs implies a risk of increased N2O emissions. This does not seem to be valid for CH4. However, since N2O is almost always produced wherever NO3− is denitrified, increased N2O production in wetlands leads to reduced rates in downstream environments. Hence, we conclude that when balancing NO3− retention and global warming aspects, we find no reason to discourage future creation or restoration of wetlands.
|
|
