Seasonal Dynamics of Brownification Mitigation in Constructed Wetlands
Borgert, Jasmin LU ; Jones, Kevin LU
; Nilsson, Josefin E.
; Sjöstedt, Johanna
LU
and Liess, Antonia
(2025)
In Wetlands
45(5).
- Abstract
Increasing total organic carbon (TOC) concentrations concurrent with a darkening in water colour in boreal freshwaters is called brownification. This can affect crucial ecosystem services. Our study investigated constructed wetland optimisation regarding depth and water residence time (WRT) during different seasons to remedy dark water colour and high TOC concentrations, while retaining nitrogen removal. We conducted eleven-day experiments with deep-brown, shallow-brown and shallow-control treatments, in June and November 2023, using 18 small constructed wetlands at an experimental wetland area in southern Sweden. At the beginning of both experiments, the flow through the wetlands was halted and extracted peat was added to the brown... (More)
Increasing total organic carbon (TOC) concentrations concurrent with a darkening in water colour in boreal freshwaters is called brownification. This can affect crucial ecosystem services. Our study investigated constructed wetland optimisation regarding depth and water residence time (WRT) during different seasons to remedy dark water colour and high TOC concentrations, while retaining nitrogen removal. We conducted eleven-day experiments with deep-brown, shallow-brown and shallow-control treatments, in June and November 2023, using 18 small constructed wetlands at an experimental wetland area in southern Sweden. At the beginning of both experiments, the flow through the wetlands was halted and extracted peat was added to the brown treatments, to increase absorbance and TOC concentrations. Thereafter, changes in absorbance, TOC concentration and total nitrogen (TN) concentration were measured. A maximum TOC reduction of 25% was reached with a WRT of two days in summer and one day in autumn. A maximum absorbance reduction of 40% and 65% was reached with a WRT of one day in summer and two days in autumn, respectively. TN removal was not affected by TOC addition. We conclude that constructed wetlands increase water clarity and boost carbon degradation if their WRT, especially during summer, is sufficiently short. If WRT exceeds two to three days in summer, internal carbon production together with low oxygen levels and increased iron (Fe) mobilization, may instead increase downstream brownification. Our study shows that wetlands with a depth of 0.6 m and a short WRT of one to two days may mitigate the effects of brownification.
(Less)
- author
- Borgert, Jasmin
LU
; Jones, Kevin
LU
; Nilsson, Josefin E.
; Sjöstedt, Johanna
LU
and Liess, Antonia
- organization
- publishing date
- 2025-06
- type
- Contribution to journal
- publication status
- published
- subject
- keywords
- Allochthonous carbon, Autochthonous carbon, Browning, Nature-based solutions, Organic matter
- in
- Wetlands
- volume
- 45
- issue
- 5
- article number
- 63
- publisher
- Springer Science and Business Media B.V.
- external identifiers
-
- scopus:105007912189
- ISSN
- 0277-5212
- DOI
- 10.1007/s13157-025-01944-6
- language
- English
- LU publication?
- yes
- additional info
- Publisher Copyright: © The Author(s) 2025.
- id
- f19b55d0-d957-40f1-8807-5fe13dc12c29
- date added to LUP
- 2025-12-17 13:50:55
- date last changed
- 2025-12-17 13:51:44
@article{f19b55d0-d957-40f1-8807-5fe13dc12c29,
abstract = {{<p>Increasing total organic carbon (TOC) concentrations concurrent with a darkening in water colour in boreal freshwaters is called brownification. This can affect crucial ecosystem services. Our study investigated constructed wetland optimisation regarding depth and water residence time (WRT) during different seasons to remedy dark water colour and high TOC concentrations, while retaining nitrogen removal. We conducted eleven-day experiments with deep-brown, shallow-brown and shallow-control treatments, in June and November 2023, using 18 small constructed wetlands at an experimental wetland area in southern Sweden. At the beginning of both experiments, the flow through the wetlands was halted and extracted peat was added to the brown treatments, to increase absorbance and TOC concentrations. Thereafter, changes in absorbance, TOC concentration and total nitrogen (TN) concentration were measured. A maximum TOC reduction of 25% was reached with a WRT of two days in summer and one day in autumn. A maximum absorbance reduction of 40% and 65% was reached with a WRT of one day in summer and two days in autumn, respectively. TN removal was not affected by TOC addition. We conclude that constructed wetlands increase water clarity and boost carbon degradation if their WRT, especially during summer, is sufficiently short. If WRT exceeds two to three days in summer, internal carbon production together with low oxygen levels and increased iron (Fe) mobilization, may instead increase downstream brownification. Our study shows that wetlands with a depth of 0.6 m and a short WRT of one to two days may mitigate the effects of brownification.</p>}},
author = {{Borgert, Jasmin and Jones, Kevin and Nilsson, Josefin E. and Sjöstedt, Johanna and Liess, Antonia}},
issn = {{0277-5212}},
keywords = {{Allochthonous carbon; Autochthonous carbon; Browning; Nature-based solutions; Organic matter}},
language = {{eng}},
number = {{5}},
publisher = {{Springer Science and Business Media B.V.}},
series = {{Wetlands}},
title = {{Seasonal Dynamics of Brownification Mitigation in Constructed Wetlands}},
url = {{http://dx.doi.org/10.1007/s13157-025-01944-6}},
doi = {{10.1007/s13157-025-01944-6}},
volume = {{45}},
year = {{2025}},
}