| 1. |
- Choudhury, Maidul I., et al.
(författare)
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Enhancing nitrogen removal through macrophyte harvest and installation of woodchips-based floating beds in surface-flow constructed wetlands
- 2024
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Ingår i: Chemosphere. - Oxford : Elsevier. - 0045-6535 .- 1879-1298. ; 359
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Tidskriftsartikel (refereegranskat)abstract
- Wetland management maintains nitrogen (N) removal capacity in mature and overgrown constructed wetlands (CWs). We evaluated whether CW management by macrophyte harvesting, and subsequent installation of woodchips-based floating beds (WFBs) planted with Glyceria maxima and Filipendula ulmaria improved N removal. In sixteen heavily overgrown experimental CWs, we applied four treatments: i) only macrophyte harvesting, ii) 5% of the harvested-CW surface covered with WFBs, iii) 20% WFBs cover, and iv) a control treatment (heavily overgrown). N removal was determined in all wetlands at nine occasions. Plant biomass accrual, N assimilation, and denitrification genes nirS, nirK, nosZI and nosZII on plant roots and woodchips from WFBs were estimated. Macrophyte harvesting improved N removal of heavily overgrown CWs, whereas subsequent WFB installation only sometimes improved N removal. Mean N removal efficiencies (± standard deviation) overall were 41 ± 15 %, 45 ± 20 %, 46 ± 16 % and 27 ± 8.3 % for treatments i to iv, respectively. Relative biomass production, root length and root surface area for G. maxima (mean ± standard deviation: 234 ± 114 %, 40 ± 6.5 cm, 6308 ± 1059 cm2g-1, respectively) were higher than those for F. ulmaria (63 ± 86 %, 28 ± 12 cm, 3131 ± 535 cm2g-1, respectively) whereas biomass N assimilation was higher for F. ulmaria (1.8 ± 0.9 gNm−2 of WFB) than for G. maxima (1.3 ± 0.5 gNm−2 of WFB). Denitrification gene abundance was higher on plant roots than on woodchips while G. maxima hosted higher root denitrification gene abundance than F. ulmaria. We conclude that macrophyte harvesting improves N removal in heavily overgrown CWs. WFBs installation has the potential to support plant growth and denitrification in surface-flow constructed wetlands. Further studies need to evaluate the long-term effects of macrophyte harvesting and WFB installation on N removal in CWs. © 2024 The Authors
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| 2. |
- Hambäck, Peter A., et al.
(författare)
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Tradeoffs and synergies in wetland multifunctionality : A scaling issue
- 2023
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Ingår i: Science of the Total Environment. - Amsterdam : Elsevier BV. - 0048-9697 .- 1879-1026. ; 862
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Forskningsöversikt (refereegranskat)abstract
- Wetland area in agricultural landscapes has been heavily reduced to gain land for crop production, but in recent years there is increased societal recognition of the negative consequences from wetland loss on nutrient retention, biodiversity and a range of other benefits to humans. The current trend is therefore to re-establish wetlands, often with an aim to achieve the simultaneous delivery of multiple ecosystem services, i.e., multifunctionality. Here we review the literature on key objectives used to motivate wetland re-establishment in temperate agricultural landscapes (provision of flow regulation, nutrient retention, climate mitigation, biodiversity conservation and cultural ecosystem services), and their relationships to environmental properties, in order to identify potential for tradeoffs and synergies concerning the development of multifunctional wetlands. Through this process, we find that there is a need for a change in scale from a focus on single wetlands to wetlandscapes (multiple neighboring wetlands including their catchments and surrounding landscape features) if multiple societal and environmental goals are to be achieved. Finally, we discuss the key factors to be considered when planning for re-establishment of wetlands that can support achievement of a wide range of objectives at the landscape scale.
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| 3. |
- Nilsson, Josefin E., 1994-, et al.
(författare)
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Mature wetland ecosystems remove nitrogen equally well regardless of initial planting
- 2020
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Ingår i: Science of the Total Environment. - Amsterdam : Elsevier. - 0048-9697 .- 1879-1026. ; 716
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Tidskriftsartikel (refereegranskat)abstract
- Restored and constructed semi-natural wetlands are increasingly used in the agricultural landscape to intercept nutrients from surface waters. Vegetated surface-flow wetlands remove more nitrogen (N) than those without vegetation. However, changes in N removal over time as differently vegetated wetlands progress from early successional stages to mature systems are less investigated. We monitored three different types of initial planting over the course of 12 years, with the aim to examine how planting of newly constructed wetlands affects long-term N removal. All our data were collected in an experimental wetland facility in south-western Sweden. The facility consists of 18 identical small (ca. 25 m2) surface-flow wetlands, simulating semi-natural wetlands in an agricultural landscape. Initially, the 18 wetlands were randomly divided into three treatments (vegetation types) with six replicates each and planted with (1) emergent vegetation, (2) submerged vegetation and (3) no vegetation for free development. Vegetation succession afterwards progressed uninhibited in all wetlands. Emergent vegetation wetlands initially removed more N than both submerged vegetation and free development wetlands. We found that N removal in submerged vegetation and free development wetlands increased with ecosystem age, whereas N removal in emergent vegetation wetlands did not. N removal in all three vegetation types converged when the wetlands reached a more mature state, around 8 years after wetland construction. However, although all wetlands contained emergent vegetation in year 8, the proportion of emergent vegetation cover and vegetation composition still differed substantially between wetland types. Our study indicates that it is not the cover of emergent vegetation per se which promotes higher N removal in more mature wetlands, but the maturation process itself; mature wetlands despite differing emergent vegetation coverage achieved equally high N removal. In conclusion, once wetlands reach maturity, beneficial effects of initial planting on N removal disappear. © 2020 The Authors. Published by Elsevier B.V.
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| 4. |
- Nilsson, Josefin E., 1994-
(författare)
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Nitrogen Removal in Created Wetlands : Considerations – Challenges – Possibilities
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Created wetlands in agricultural landscapes deliver a multitude of ecosystem services, one of which is the removal of nitrogen (N) from water to reduce eutrophication. Wetland N removal, primarily through denitrification, is influenced by various factors. For instance, macrophytes support denitrifying microorganisms and thus N removal, and the extent of N removal varies both spatially and temporally. The overall aim of this thesis was to provide a broadened understanding of considerations, challenges, and possibilities associated with achieving high N removal in created wetlands. To fulfil this aim, and thereby address knowledge gaps concerning wetland N removal, this thesis evaluates how N removal is affected by wetland placement and design, planting and harvesting of vegetation, installation of floating wetlands, changing climatic conditions, and interactions with other ecosystem services. These assessments were done using a combination of experimental wetland studies, a field study of created wetlands, and a literature review, all presented in the five included papers. The results highlight the rapid achievement of high N removal in wetlands planted with emergent vegetation, but also the diminishing effects of initial planting as wetland ecosystems approach maturity. Further, N removal is promoted in wetlands placed downstream of fertilised arable land to intercept as much runoff as possible, and in wetlands of elongated shape with maximised distance between inlet and outlet. Through such placement and design, created wetlands can maintain efficient N removal in spite of the anticipated increase in summer droughts. Additionally, multiple wetlands can jointly enhance landscape multifunctionality despite trade-offs between ecosystem services in individual wetlands. Even within a wetland, ecosystem services can synergistically interact. Although dependent on design, created wetlands can efficiently remove N and attenuate floods, without elevating greenhouse gas emissions. Moreover, specific wetland properties promote ecosystem services additional to N removal, making it possible to increase N removal by creating wetlands with other primary objectives. Lastly, N removal in heavily overgrown wetlands can be enhanced through macrophyte harvest, and floating wetlands offer further possibilities of improved N removal. In conclusion, with an improved understanding of wetland N removal, future creation and restoration of wetlands in agricultural areas hold the potential to further contribute to mitigating eutrophication and its detrimental consequences.
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| 5. |
- Nilsson, Josefin E., 1994-, et al.
(författare)
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Näringsavskiljning i anlagda våtmarker i Kalmar län
- 2020
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- I den här studien beräknades kväve- och fosforavskiljningen utifrån automatiserad flödesproportionell provtagning i fem anlagda våtmarker i Kalmar län under tre års tid samt i ett anlagt fosfordike i länet under två år (fortsättningsvis benämns alla sex studieobjekt som våtmarker). Syftet med studien var att utvärdera funktionen av våtmarker i Kalmar län för avskiljning av kväve och fosfor. I rapporten presenteras även nya beräkningsmetoder som tagits fram för att hantera de osäkerheter som oundvikligen följer av denna typ av situ-studier. Denna rapport bör kunna bidra till förbättrade mätmetoder och analyser i framtida våtmarksstudier.De våtmarker som ingår i studien är lokaliserade i fem olika kommuner i Kalmar län. Våtmarkerna som studerats är Hanåsa (Högsby kommun), Resmo (Mörbylånga kommun), Påboda (Torsås kommun), Grisbäck (Torsås kommun), Hossmo (Kalmar kommun) och Häckenstad (Västerviks kommun). Urvalet av våtmarker är gjort av Länsstyrelsen med målsättningen att få ett representativt urval av våtmarker i Kalmar län. Våtmarkerna i studien skiljer sig därför från varandra både i utformning och i vilken omgivning de är anlagda. De flesta av våtmarkerna är cirka en halv hektar stora, men den största våtmarkens area är 2,5 hektar och den minsta har en area på endast 220 kvadratmeter. Några av våtmarkerna har mycket hög andel åkermark i tillrinningsområdet, medan andra våtmarker främst har skog i sitt tillrinningsområde.Flödesproportionell provtagning har kontinuerligt genomförts vid in- och utlopp i fem våtmarker från november 2016 till och med december 2019, och i en våtmark från maj 2018 till och med december 2019. I tre av våtmarkerna mättes flöde både vid inlopp och utlopp, och i tre av våtmarkerna mättes flöde endast vid utlopp. Flödesmätning gjordes en gång per minut, och varje vecka hämtades vattenprover från våtmarkerna för att analyseras för bland annat innehåll av näringsämnen. Den data som samlats in har sedan bearbetats, beräknats och korrigerats för att kunna användas i bedömningen av våtmarkernas näringsavskiljning.Flödena i våtmarkerna följde vanligen tydliga säsongsmönster där sommarflöden var låga och flödestoppar skedde under höst, vinter och vår. Resmo, på Öland, hade längre torrperioder än övriga våtmarker i studien. Näringskoncentrationerna vid de olika våtmarkernas inlopp var i genomsnitt under studien mellan 1,7 och 9,9 mg kväve per liter och mellan 64 och 157 µg fosfor per liter. Kvävet var huvudsakligen i form av nitratkväve, och fosforn var i huvudsak partikelbunden fosfor. Både kväve- och fosforavskiljning i våtmarkerna ökade med ökad belastning. Den genomsnittliga årliga kväve- och fosforavskiljningen per hektar vattenyta skiljde sig stort mellan våtmarkerna. Den varierade från negativ avskiljning i den största våtmarken till över 1 000 kg per hektar vattenyta och år för både kväve och fosfor i den minsta våtmarken (tabell 1). Angivet i procent avskildes i genomsnitt upp till 14 % av den årliga kvävebelastningen och upp till 70 % av den årliga fosforbelastningen. Jämfört med tidigare modellerad kväve- och fosforavskiljning för våtmarker i Kalmar län och andra delar av Sverige var avskiljningen i våtmarkerna i denna studie generellt högre.Tabell 1. Genomsnittlig kväve- och fosforavskiljning angivet per hektar vattenyta och år och i procent av den årliga belastningen i de sex våtmarkerna i studien. På grund av mätosäkerheter anges avskiljningen i vissa av våtmarkerna som ett intervall. Kväveavskiljning FosforavskiljningVåtmark kg ha-1 år-1 % kg ha-1 år-1 %Hanåsa -351 -37 -49 -91Resmo 407 3,8 19 31Påboda 845 – 1 013 12 – 14 20 – 28 22 – 29Grisbäck 523 – 899 7,2 – 12 113 – 153 45 – 54Hossmo 346 – 965 2,7 – 7,3 -1,1 – 14 -4,4 – 13Häckenstad 1 471 4,3 1 688 70Resultaten i denna studie visar att våtmarker i Kalmar län kan uppnå hög näringsavskiljning, men att skillnaderna mellan olika våtmarker är stora. Resultaten visar också att hög kväve- och fosforavskiljning kan uppnås i våtmarker med relativt låg andel åkermark i tillrinningsområdet, och att mycket hög fosforavskiljning kan uppnås i små våtmarker även utan en djuphåla. Projektet bidrar till en bättre bild av vilken avskiljning av kväve och fosfor som kan uppnås i anlagda våtmarker i södra Sverige. Resultat från projektet kan tillsammans med tidigare mätningar utgöra en grund för säkrare modellberäkningar av kväve- och fosforavskiljning, vilka kan användas för att på ett enklare sätt undersöka avskiljningen i ett större antal våtmarker eller för att prediktera vad som kan uppnås i planerade våtmarksprogram.
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| 6. |
- Nilsson, Josefin E., 1994-, et al.
(författare)
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Wetlands in a future climate : How will drier summers affect wetland nitrogen removal?
- 2022
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Ingår i: Abstract Book. ; , s. 138-139
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Wetland nitrogen (N) removal is temperature dependent and therefore generally highest during summer in the northern temperate zone. However, climate change scenarios predict more frequent summer droughts in these regions, resulting in lowered N transports during summer to wetlands created for interception of agricultural runoff. This may adversely affect annual wetland N removal, thus reducing the mitigative effects wetlands have on eutrophication. In this study, continuous flow-proportional sampling was performed in six agricultural wetlands located on the east coast, and three on the west coast, of southern Sweden. These two regions represent different climate conditions, where precipitation is lower and summer temperatures are higher on the east coast. Our results showed a pronounced no-flow period during summer in east coast wetlands, but not in west coast wetlands. No-flow periods only decreased N load and removal rate during summer but had no effect on annual N removal. Annual N removal was instead best explained by multiple regression with annual N load and hydraulic efficiency as predictors. This indicates that low wetland N removal during drier summers may be compensated by higher N removal during other seasons. A possible explanation is that annual N removal through denitrification is determined by the amount of organic carbon provided by wetland vegetation, and that organic carbon not utilized during summer, due to lack of nitrate and oxygen under no-flow conditions, will be available for denitrification during other seasons. In conclusion, climate change might not have the anticipated decreasing effect on wetland N removal.
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| 7. |
- Nilsson, Josefin E., 1994-, et al.
(författare)
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Will planting of surface-flow wetlands improve nitrogen removal in the long run?
- 2019
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Ingår i: Book of Abstracts. - Aarhus : Aarhus Universitetsforlag. - 9788797148600 - 9788797148617 ; , s. 340-340
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Initial planting of created wetlands is common practice in order to, for instance, improve nitrogen (N) removal. It has been shown that vegetated surface-flow wetlands remove more N than non-vegetated surface-flow wetlands. However, changes in N removal as differently vegetated wetlands progress from an early successional stage to a mature system are less investigated.In our study, we followed three different wetland types of initial planting over the course of 12 years, with the aim to examine how planting of newly created wetlands affects long-term N removal. All our data were collected in the experimental wetland facility near Halmstad in south-western Sweden. The facility consist of 18 small (ca. 25 m2) surface-flow wetlands, equal in age, shape and size. At the time of creation, the 18 wetlands were randomly divided into three types. One type was then planted with emergent vegetation, one was planted with submerged vegetation and the last type was left unplanted for free development. Succession of vegetation was thereafter allowed to progress uninhibited in all wetlands.Our results confirmed that emergent vegetation wetlands initially removed more N than submerged vegetation and free development wetlands. In addition, our results showed that N removal in submerged vegetation and free development wetlands increased with ecosystem age, whereas N removal in emergent vegetation wetlands did not. N removal in all three wetland vegetation types converged when the wetlands reached a more mature state, around year 9 after wetland creation. However, although all wetlands contained emergent vegetation in year 9, proportion cover of emergent vegetation and vegetation composition still differed substantially between wetland types.We therefore conclude planting of created surface-flow wetlands with emergent vegetation will have a positive effect on N removal, but only during an early successional stage. Our study indicates it is not the emergent vegetation per se which results in higher N removal in more mature wetlands, but the maturation process in itself, since mature wetlands with different emergent vegetation cover achieved similar N removal. Initial planting will not result in higher N removal once the system has reached maturity.
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