| 1. |
- Bastviken, S K, et al.
(author)
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Potential nitrification and denitrification on different surfaces in a constructed treatment wetland
- 2003
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In: Journal of Environmental Quality. - 0047-2425. ; 32:6, s. 2414-2420
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Journal article (peer-reviewed)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.
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| 2. |
- Johannesson, K., 1982-, et al.
(author)
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Phosphorus dynamics and retention in non-point source wetlands in southern Sweden
- 2010
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In: Proceedings of the 12th International Water Association International Conference on Wetland Systems for Water Pollution Control. - San Giovanni Valdarno : Palombi Editori. - 9788860603005 ; , s. 493-494
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Conference paper (peer-reviewed)abstract
- Seven constructed wetlands receiving diffuse pollution from agricultural land in the south of Sweden were investigated with respect to water flow patterns and phosphorus (P) dynamics. P retention was positive, and correlated to P load in all wetlands. However, there was a large variation in both specific and relative retention, both between wetlands and between years. Thus, the phosphorus retention in a specific wetland is difficult to predict using simple loadretention models. The water flow was correlated to P concentrations in most wetlands; however, there were some exceptions. For instance, one wetland showed a negative relationship between water flow and P concentration during summer, which indicated that other factors than the water flow determined the dynamics of P during this season. This investigation will provide a better understanding of factors affecting phosphorus retention in constructed wetlands, with further implications for wetland research and monitoring. Furthermore, the results can assist when formulating models for phosphorus removal in wetlands receiving nonpoint source runoff.
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| 3. |
- Reusch, T. B. H., et al.
(author)
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The Baltic Sea as a time machine for the future coastal ocean
- 2018
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In: Science Advances. - : American Association for the Advancement of Science (AAAS). - 2375-2548. ; 4:5
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Journal article (peer-reviewed)abstract
- Coastal global oceans are expected to undergo drastic changes driven by climate change and increasing anthropogenic pressures in coming decades. Predicting specific future conditions and assessing the best management strategies to maintain ecosystem integrity and sustainable resource use are difficult, because of multiple interacting pressures, uncertain projections, and a lack of test cases for management. We argue that the Baltic Sea can serve as a time machine to study consequences and mitigation of future coastal perturbations, due to its unique combination of an early history of multistressor disturbance and ecosystem deterioration and early implementation of cross-border environmental management to address these problems. The Baltic Sea also stands out in providing a strong scientific foundation and accessibility to long-term data series that provide a unique opportunity to assess the efficacy of management actions to address the breakdown of ecosystem functions. Trend reversals such as the return of top predators, recovering fish stocks, and reduced input of nutrient and harmful substances could be achieved only by implementing an international, cooperative governance structure transcending its complex multistate policy setting, with integrated management of watershed and sea. The Baltic Sea also demonstrates how rapidly progressing global pressures, particularly warming of Baltic waters and the surrounding catchment area, can offset the efficacy of current management approaches. This situation calls for management that is (i) conservative to provide a buffer against regionally unmanageable global perturbations, (ii) adaptive to react to new management challenges, and, ultimately, (iii) multisectorial and integrative to address conflicts associated with economic trade-offs.
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| 4. |
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| 5. |
- Diwan, Vishal, et al.
(author)
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Antibiotics and antibiotic-resistant bacteria in waters associated with a hospital in Ujjain, India
- 2010
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In: BMC Public Health. - : BioMed Central. - 1471-2458. ; 10:414
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Journal article (peer-reviewed)abstract
- Background: Concerns have been raised about the public health implications of the presence of antibiotic residues in the aquatic environment and their effect on the development of bacterial resistance. While there is information on antibiotic residue levels in hospital effluent from some other countries, information on antibiotic residue levels in effluent from Indian hospitals is not available. Also, concurrent studies on antibiotic prescription quantity in a hospital and antibiotic residue levels and resistant bacteria in the effluent of the same hospital are few. Therefore, we quantified antibiotic residues in waters associated with a hospital in India and assessed their association, if any, with quantities of antibiotic prescribed in the hospital and the susceptibility of Escherichia coli found in the hospital effluent. Methods: This cross-sectional study was conducted in a teaching hospital outside the city of Ujjain in India. Seven antibiotics - amoxicillin, ceftriaxone, amikacin, ofloxacin, ciprofloxacin, norfloxacin and levofloxacin - were selected. Prescribed quantities were obtained from hospital records. The samples of the hospital associated water were analysed for the above mentioned antibiotics using well developed and validated liquid chromatography/tandem mass spectrometry technique after selectively isolating the analytes from the matrix using solid phase extraction. Escherichia coli isolates from these waters were tested for antibiotic susceptibility, by standard Kirby Bauer disc diffusion method using Clinical and Laboratory Standard Institute breakpoints. Results: Ciprofloxacin was the highest prescribed antibiotic in the hospital and its residue levels in the hospital wastewater were also the highest. In samples of the municipal water supply and the groundwater, no antibiotics were detected. There was a positive correlation between the quantity of antibiotics prescribed in the hospital and antibiotic residue levels in the hospital wastewater. Wastewater samples collected in the afternoon contained both a higher number and higher levels of antibiotics compared to samples collected in the morning hours. No amikacin was found in the wastewater, but E. coli isolates from all wastewater samples were resistant to amikacin. Although ciprofloxacin was the most prevalent antibiotic detected in the wastewater, E. coli was not resistant to it. Conclusions: Antibiotics are entering the aquatic environment of countries like India through hospital effluent. Indepth studies are needed to establish the correlation, if any, between the quantities of antibiotics prescribed in hospitals and the levels of antibiotic residues found in hospital effluent. Further, the effect of this on the development of bacterial resistance in the environment and its subsequent public health impact need thorough assessment.
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| 6. |
- Sundberg, Carina, 1963-, et al.
(author)
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Overland flow systems for treatment of landfill leachates : Potential nitrification and structure of the ammonia-oxidising bacterial community during a growing season
- 2007
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In: Soil Biology and Biochemistry. - : Elesevire. - 0038-0717 .- 1879-3428. ; 39:1, s. 127-138
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Journal article (peer-reviewed)abstract
- Overland flow systems are useful for treating landfill leachates, because they provide favourable conditions for nitrification and they are easy to maintain. However, little is known about the microbial communities in such systems or the nitrification capacity of those microorganisms. In this study, seasonal variations in potential nitrification and in community composition of nitrifying bacteria were investigated in two overland flow areas receiving leachate from landfills at Korslöt and Hagby, Sweden. Samples were collected in the settling ponds sediment and at two depths in the overland flow areas (the macrophyte litter layer and the rhizosphere) in May, August and November 2003. A short-term incubation method was used to measure potential oxidation of ammonia and nitrite (designated PAO and PNO). The ammonia-oxidising bacterial (AOB) community was investigated using a 16S rRNA gene approach that included PCR amplification and analysis of PCR products by denaturing gradient gel electrophoresis (DGGE), followed by nucleotide sequencing and phylogenetic analysis. PAO was determined in the range 5–2700 (NO2−+NO3−)-N g−1 dw d−1 and PNO in the range 60–2000 μg NO2−-N g−1 dw d−1. At Korslöt, PAO and PNO showed similar temporal variation in the different ecosystems, whereas no such relationship was noticed at Hagby. Considering both sites, there was no obvious change in the composition of the AOB community over the growing season. However, the composition did differ between the ecosystems: Nitrosomonas-like sequences were more common in the ponds, and in the litter layers they were found as often as Nitrosospira-like sequences, whereas Nitrosospira-like sequences were more common in the rhizospheres. Altogether, we found nine different AOB sequences, five Nitrosomonas-like and four Nitrosospira-like, which belonged to clusters 0, 2, 3b, 6a, 6b and 7. There was no apparent relationship between the number of AOB populations and the PAO in different soil layers and sediments.
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| 8. |
- Thoren, A.-K., et al.
(author)
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Temporal export of nitrogen from a constructed wetland : Influence of hydrology and senescing submerged plants
- 2004
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In: Ecological Engineering. - : Elsevier BV. - 0925-8574 .- 1872-6992. ; 23:4-5, s. 233-249
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Journal article (peer-reviewed)abstract
- Nitrogen export was measured during monthly monitoring in an 18-ha constructed wetland in southeast Sweden 1998-2001. To investigate the influence of increased water flow on wetland nitrogen export, we performed intensive sampling (eight samples per day) of total-N, urea-N, NH4+-N, NO3--N in January-March 2001. Investigations of wetland plant distribution 1997-2001 and submerged plant biomass were combined with investigations of plant nitrogen content 1998-2001, to test the hypothesis that nitrogen export was linked to wetland plant decomposition. Nitrogen was exported from the wetland (3.3 kg N ha-1 d-1), during the end of the intensive sampling period (19 February-12 March), coinciding with increased water flow (from 0.2 to 0.6 m3 s-1). Plant cover expanded rapidly and nitrogen assimilated in the submerged plant community was estimated to be 39 kg ha-1 in July 2001. After senescence in April the following year, plant biomass was reduced by 75%. We concluded that a significant part (40%) of this wetland nitrogen export might be associated with the release of organic and inorganic nitrogen from the senesced submerged plant community. Moreover, we hypothesize that nitrogen removal in wetlands in cold temperate climate may be limited by temporal nitrogen export induced by high water flow velocity when wetland plants are decomposing. © 2004 Elsevier B.V. All rights reserved.
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