| 1. |
- Graversgaard, Morten, et al.
(författare)
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Policies for wetlands implementation in Denmark and Sweden - historical lessons and emerging issues
- 2021
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Ingår i: Land use policy. - : Elsevier. - 0264-8377 .- 1873-5754. ; 101
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Tidskriftsartikel (refereegranskat)abstract
- Natural wetlands used to cover a significant part of the landscape, but these ecosystems have declined by >50% worldwide, and even more in Denmark and Sweden. However, since the 1980s, various policies have been implemented to restore and create wetlands. This study provides a comprehensive historical overview of policies used to stimulate the creation and restoration of wetlands in Denmark and Sweden, and also analyses what factors have facilitated participation or have been barriers for landowners. The analysis of wetlands implementation programmes in Denmark showed a change towards narrower focus on nitrogen reduction from 1998 and onwards, whereas policies in Sweden often have had a wider multifunctional purpose. In both countries, there has been a change in the compensation structure from a lump sum to annual payments, parallel to an observed increase in costs for wetlands implementation. There is still a large potential for recreating many more wetlands, and the national targets have not been reached in neither Denmark nor Sweden. Key success factors, for future wetlands implementation are sufficient compensation levels, flexible scheme designs and information-based strategies documenting relevant benefits and sustainability issues. In general, more advice and support from the state, regional and local participants, and farmers organisations, are required to increase the participation and achieve successful and cost-efficient wetlands implementation. A collaborative and catchment-based approach holds promise, where wetland governance can serve as a platform for collaboration between policy bodies and between farmers. Additionally, politicians and decision makers need to accept the area targets presented to them when setting policy goals for wetlands implementation, and to accept that restoring and constructing wetlands requires long implementation times before results can be demonstrated.
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| 2. |
- Johannesson, Karin, 1982-
(författare)
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Analysis of phosphorus retention variations in constructed wetlands receiving variable loads from arable land
- 2011
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Seven wetlands, constructed on agricultural land in the south of Sweden, were investigated with respect to phosphorus (P) retention. The overall aim was to increase the understanding of P retention and find possible explanations for the variations in retention that have been observed in previous studies. This was done by i) investigating P retention in wetlands receiving various water and P loads, ii) investigating the effect of variations in water flow on P transport, iii) comparing how well retention estimates based on water quality data agreed with measurements of the amount of P accumulated in the sediment.Results showed that P retention was positive in all wetlands, but it was variable (1–58 kg ha-1 yr-1) and months with negative retention were observed in nearly all wetlands. Such monthly negative retention coincided with i) high flow periods, when particulate P was either flushed straight through the wetlands or resuspended from the bottoms, and ii) warm low flow periods, in which case dissolved P was probably released from wetland sediments due to anoxic conditions.The results from the two methods for estimating P retention differed. Based on water quality data, the total P load during four years was 65 kg ha-1 and the mean P retention 2.8 kg ha-1 yr-1, or 17% of the total P load. In contrast, the amount of P accumulated in the inlet zone alone amounted to 78% of the P load, and the P content in the upper sediment of the whole wetland area exceeded the P load with a factor four. This discrepancy showed the need to add studies of sediment accumulation to inflow-outflow estimates for an improved understanding of wetland P retention.
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| 3. |
- Mendes, Lipe Renato Dantas, et al.
(författare)
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Phosphorus accumulation and stability in sediments of surface-flow constructed wetlands
- 2018
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Ingår i: Geoderma. - : ELSEVIER SCIENCE BV. - 0016-7061 .- 1872-6259. ; 331, s. 109-120
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Tidskriftsartikel (refereegranskat)abstract
- Surface-flow constructed wetlands (CWs) are systems that replicate the nutrient reduction processes of natural wetlands and are considered suitable measures to reduce the nutrient losses from agricultural drainage discharge to surface waters. The present study aimed to investigate the biogeochemical stability of phosphorus (P) in three CWs. Intact soil cores were collected from each CW zone and included the soil and the sediment layer (average 28 mm thickness) formed by deposition of the incoming sediments with the water flow. Soil and sediment layer were analysed geochemically, including bulk density, pH, and total contents of carbon, nitrogen, P as well as different extracts of iron (Fe), aluminium and P. In situ measurements of soil redox potential, dissolved oxygen concentration and temperature were carried out in the CWs during 16 months. Grab water samples were collected across the CWs for determination of P species, total Fe, sulphate and pH. Soil core analysis revealed that the major P storage in the CWs was attributed to retention of Fe-bound P in the sediment layer. The Fe and total P (TP) retention differed significantly between CWs (11-63 g Fe m(-2) yr(-1) and 1-9 g TP m(-2) yr(-1)). Amorphous Fe oxides constituted the major P sorbent fraction in the soil and sediments of all CWs, and the higher P sorption capacity in the sediment layer demonstrated the continuous supply of P sorbents to this layer. The stability of Fe bound P in the anaerobic sediments seemed to be controlled by the high molar ratios of bicarbonate-dithionite extractable Fe (Fe-BD) to associated P, which varied from 21 to 49, and the presence of an aerobic sediment-water
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| 4. |
- Mendes, Lipe Renato Dantas, et al.
(författare)
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Phosphorus retention in surface-flow constructed wetlands targeting agricultural drainage water
- 2018
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Ingår i: Ecological Engineering. - : ELSEVIER SCIENCE BV. - 0925-8574 .- 1872-6992. ; 120, s. 94-103
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Tidskriftsartikel (refereegranskat)abstract
- Surface-flow constructed wetlands (CWs) are potential cost-efficient solutions to mitigate phosphorus (P) loads from agricultural areas to surface waters. Hydraulic and phosphorus loading rates (HLR and PLR) are critical parameters that regulate P retention in these systems. The present study aimed to assess P retention from agricultural drainage discharge by three new CWs in Denmark during three years. The CWs presented different geologies, and received event-driven drainage discharge. The relations of HLR, PLR, dominant P forms, and iron (Fe) inputs to P retention were also investigated. The drainage discharge varied seasonally and average annual HLR ranged from 17 to 60 m yr(-1) for the three CWs. PLR varied concomitantly to HLR with average annual PLR from 2.8 to 13.5 g m(-2) yr(-1), where specific total P (TP) retention followed its variations. Specific TP retention responded differently to HLR and PLR in the CWs, depending on the dominant P forms at the inlet water. The CWs worked as P sinks and presented similar or higher retentions than other Nordic CWs with similar loads. PLR explained most of the variation in specific TP retention (52-72%), whereas HLR only explained 20-34%. Specific TP retention responded more promptly to PLR when the inlet water was dominated by particulate P (PP), since it is more easily retained than dissolved P. TP retention efficiency varied more irregularly and the annual retention ranged from 24 to 66%. It presented weak correlations to HLR and PLR, and depended on the dominant P forms and major retention mechanisms, as well as P biogeochemical stability. Thus, increasing TP retention efficiency occurred under higher stability of sediment bound P, as supported by higher total Fe:PP molar ratios at the inlet water. The supply of P sorbents by drainage discharge, soil redox conditions and Fe:P molar ratios are considered key parameters controlling the biogeochemical stability of P, and thus the long-term P retention performance in CWs.
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