Intact peatlands are key resources for freshwater that contribute to multiple hydrological ecosystem services. They retain rainwater and regulate water quality downstream by storing contaminants in the peat profile. The release of heavy metals and nutrients, through burning or erosion of near-surface deposits, has the potential to provide a persistent source of legacy contamination, namely metal contamination, to downstream drinking water supplies. With future climate change increasing the frequency and severity of wildfires in summer and heavy rainfall in winter, the risk of contaminant release from high-latitude peat regions and downstream impact is uncertain.

In June 2018, a major wildfire affected an area of upland moorland (Saddleworth Moor, UK), which contains peat deposits contaminated with atmospherically derived metal deposits. We assessed potential water quality impacts from hillslope contaminant source to the fluvial system by monitoring of heavy metals in the catchment, namely lead (Pb), zinc (Zn), copper (Cu) and nickel (Ni). Specifically, we quantified the (1) metal concentrations in ash deposits resulting from contrasting burn severities; (2) dissolution and erosion of ash and peat deposits under intense rainstorm events; and (3) their transport via the stream network to the receiving reservoir. Ash and peat samples obtained following the wildfire were analysed for total elemental concentration and leaching potential. We calculated ash loads at different burn severities and hillslope erosion was monitored through a series of sediment fences. Heavy metal concentrations in five rainstorm runoff events were measured at the stream outlet of a small catchment within the burn perimeter in the year following the wildfire.

Both ash and peat samples had elevated total heavy metal concentrations, which varied spatially across the study site. The spatial variability was partly associated with different burn severities and ash loads. In extreme burn severity areas, ash loads reached nearly 40 t ha^-1 and Pb concentrations in ash, for example, were as high as 2650 µg g^-1, indicating particularly high potential for contamination of water sources. Conversely, the maximum concentration of dissolved heavy metals in the stream-flow were much lower during the initial post-wildfire storm events (Pb 0.77 µg g^-1; Zn 38.67 µg g^-1; Cu 5.05 µg g^-1; Ni 0.26 µg g^-1).

The low solubility of heavy metals in both ash and peat samples likely constrains mobilisation by dissolution during storm events, suggesting low acute risk to drinking water quality post-wildfire. Instead, we hypothesise that metals likely remain bound to peat and ash particles, and are subsequently transported downstream in particulate form. Further quantification of heavy metals in sediment cores from sink zones will test if the metal contaminants pose a future chronic threat to drinking water quality.

How to cite: Marcotte, A. L., Limpens, J., Shuttleworth, E. L., Clay, G., Nunes, J. P., Santín, C., Doer, S. H., Neris, J., Warburton, J., Chiverrell, R. C., and Kettridge, N.: After the flames: Post-wildfire heavy metal mobilisation in a contaminated temperate peatland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-562, https://doi.org/10.5194/egusphere-egu24-562, 2024.

Mires are one of the systems, which are highly affected by climate change. At the same time, they are main sources of greenhouse gases (GHG) such as methane (CH₄) and carbon dioxide (CO₂). Considering that hydrological patterns remain major factors affecting these emissions and they are likely to be affected by climate change, GHG fluxes may be altered as well. Whereas majority of the studies focused on direct GHG emissions from the peat or mire surface waters, less in known about the processes of groundwater flow especially in relation to transfer of GHG-rich groundwater to the mire ecosystems.

The main objective of this study was to assess how dynamics of CO₂ and CH₄ in groundwater of mires is likely to be affected due to changed paths of groundwater flow.

The study was conducted from May 2023 till October 2023 in four mires located along latitudinal gradient from subarctic Norway to temperate areas in Poland, which serve as examples of systems exposed to abrupt climate change. They include Nordic permafrost and bog-like systems in Norway through bog-lake system in Poland. The study used the set of gas piezometers (gas-equilibrators) located towards-to-lake transect, where concentrations of CO₂ and CH₄ were measured in vertical profiles (2 m, 1m, 0.1m). Simultaneously, water levels were measured with automatic pressure transducers in a 3-h interval. We also documented electric conductivity of groundwater along the transects in which the dynamics of CO₂ and CH₄ were assessed.

We determined the amounts of CO₂ and CH₄ transported by groundwater to the mires. Our results demonstrate high vertical and temporal variability of GHG concentrations in groundwater of mires, which has implications for determination of future carbon balance in such areas.  Additionally, our findings imply that groundwater is an important GHG source to the mire and need to be considered in the light of climate change as increasing sources of GHG into the atmosphere. Changes in groundwater flow caused by global warming (e.g., palsa mires decomposition, increase of evapotranspiration in temperate mires) can have significant influence on emissions of GHG in the future.

How to cite: Sieczko, A., Silvennoinen, H., Lyngstad, A., Stachowicz, M., Osuch, P., Michałowski, R., Trandziuk, P., and Grygoruk, M.: Impact of changing groundwater flow paths on CO2 and CH4 dynamics in the groundwater of temperate-to-arctic mires, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13481, https://doi.org/10.5194/egusphere-egu24-13481, 2024.

Peat accumulates when there is a positive mass balance between plant productivity inputs and litter/peat decomposition losses. Here we examine apparent peat accumulation rates (aPAR) during the last two millennia from 28 well-dated European peatlands and find them to range between 0.005 and 0.448 cm yr^-1 (mean = 0.118 cm yr^-1). Our work provides important context for the commonplace assertion that peatlands accumulate at ~1mm per year. We find that relationships between aPAR and climatic variables are generally weak – summer temperature is the only significant climatic control on aPAR across our European sites. aPAR tends to be higher when water-table depth (reconstructed from testate-amoeba subfossils) is within 5-10 cm of the peatland surface. When a Generalized Additive Model and Gaussian Response Curve are fitted to the data, both methods show that the optimal water-table depth for highest aPAR is ~10 cm.  aPAR is generally lower when water table depths are <0 cm (standing water) or >25 cm, which may relate to a decrease in plant productivity and increased decomposition losses, respectively. These findings corroborate contemporary experimental studies which examined the relationship between peatland water-table depth, or the thickness of the aerobic surface layer (the ‘acrotelm’), and the rate of peat formation. Our work suggests that for European peat bogs, an average water-table depth of ~10 cm is optimal to enable rapid peat growth and therefore carbon sequestration in the long term. This has important implications for peatland restoration and rewetting strategies, in our global efforts to mitigate climate change.

How to cite: Swindles, G. T., Mullan, D. J., Brannigan, N. T., Sim, T. G., Gallego-Sala, A., Blaauw, M., Lamentowicz, M. L., Green, S. M., Roland, T. P., and Fewster, R. and the European peatland research group: Climate and hydrology control apparent rates of peat accumulation across Europe, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21369, https://doi.org/10.5194/egusphere-egu24-21369, 2024.

Peatlands are complex wetlands that play an important role in global carbon cycling as both carbon sinks and sources. They contain over one-third of all global soil carbon but cover <3% of all land surfaces. The hydrology of a peatland exerts a significant control on overall carbon cycling as the position of the water table directly impacts carbon sequestration and emission while circulation within the peat basin will influence nutrient availability. Hydro-geophysical studies of northern peatlands over the last two decades have identified the presence of eskers buried beneath some peat deposits in Maine. These studies have hypothesized that eskers drive vertical groundwater flow within these systems and may act as hotspots for methane emissions. However, only conceptual hydrologic models have been developed to support this claim. Using the results of these studies along with new hydrologic and geophysical datasets, a USGS MODFLOW 6, finite-difference groundwater flow model was developed for Caribou Bog near Bangor, ME. Caribou Bog is a multi-unit, ombrotrophic, domed bog with a patterned pool system. Groundwater flow simulations were run at regional and local scales by inserting a fine-scale model encompassing a single peat unit into a coarser-grid, watershed area. The PEST parameter estimation package was used to calibrate the model and MODPATH 7 was used to identify flow paths within the model. Simulation results show that these esker deposits enhance vertical flow through the peat and potentially connect the peatland to the regional aquifer system. These results challenge the traditional viewpoint that ombrotrophic peat systems in boreal regions are relatively disconnected from groundwater flow. Furthermore, they may provide insights into the spatial variability of carbon cycling within peatlands, particularly to assess hydrologic response caused by changing precipitation patterns and warming temperatures expected due to climate change.

How to cite: Niedzinski, V., Reeve, A., Slater, L., and Comas, X.: Modeling the Influence of Subsurface Geology on Northern Peatland Hydrology, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13729, https://doi.org/10.5194/egusphere-egu24-13729, 2024.

Drainage is often used to increase agriculture production, but it has adverse effects on biodiversity and water retention. Here, the effect of
subsurface pipe drainage on peat meadows near Senotín (Czechia), which were drained from the mid-1980s to 1990s, was studied. Attempts
were made to restore the peat meadows by damming drainage pipes using clay-filled trenches in 1996. In this case study, the effect on the
depth of the water table, soil water retention, infiltration, and soil temperature were recorded. Measurements of the original peat meadow
(undrained site), drained meadow (drained site), and restored meadow (restored site) before restoration and two decades after restoration
were recorded. The water table in undrained areas was higher than at drained and restored sites, indicating that drainage had a lasting effect
on drained and restored sites. Infiltration was lowest at the undrained site, greater at the drained site, and highest at the restored sites. Field
water capacity was lowest at the restored site, greater at the drained site, and highest at the undrained site. Soil water content at maximum
saturation was lowest at the restored site, greater at the drained site, and highest at the undrained site. Soil temperature was highest at the
restored site with no significant difference between the undrained and drained sites. Soil moisture levels were highest at the undrained site
and lowest at the drained site. In addition, the undrained and restored sites did not differ significantly in soil moisture content. In conclusion,
restoration did not have a significant effect on the level of the water table, initiation of peat formation, or ability of soil to hold water.

How to cite: Oppong, J. C., Macháčková, J., and Frouz, J.: The Effect of Underground Pipe Drainage and Consequent Site Restoration by Drainage Inactivation on the Ability of Soils to Retain Water., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4553, https://doi.org/10.5194/egusphere-egu24-4553, 2024.

Shrinkage is the volume reduction of a soil due to desiccation and decreasing pore pressure. This is important for the determination of volume based physical and hydraulic soil properties in the laboratory e.g., bulk density, volumetric moisture and water retention functions. Furthermore, it leads to changing surface elevation and crack formation at the field scale.

There are two types of shrinking soils, clayey soils and organic soils, which are defined here as soils having a soil organic carbon content (SOC) above 7.5%. Clayey and organic soils differ strongly in their shrinkage behavior.  Furthermore, only few shrinkage studies differentiate between different organic soils. Parameters of existing shrinkage models are fully empiric and not directly linked to soil properties as dry bulk density, SOC, botanical composition and degree of decomposition.

To determine the soil shrinkage characteristics (SSC i.e., relationship between moisture ratio and void ratio) of a variety of organic soils, we determined sample volumes with a three-dimensional (3D) structured light scanner at different moisture states from full saturation to dryness. We sampled 33 horizons (n = 4 replicates each) covering a wide range of botanical composition, development stages and degree of decompositions. Desiccation was performed by suction plates up to pressure heads of -200 hPa, followed by evaporation and oven-drying at 105°C. Volume and height of the 3D models created this way were determined by 3D graphic software and R, respectively. The volumetric moisture was determined by weighing the sample before and after scanning. Afterwards, volume and volumetric moisture were converted to moisture ratio and void ratio with the volume of solid particles. Due to small differences in particle volume between the replicates, both, moisture and void ratio were normalized by dividing them by the value at saturation. This normalization led to congruent results for the replicates.

The shape of the SSCs strongly depended on the botanical composition and degree of decomposition. Peat consisting of slightly decomposed Sphagnum remains showed a supernormal shrinkage phase, i.e., volume reduction exceeds lost water volume at the dry end of the SSC and a relatively large range where volume reduction is (much) smaller than lost water volume, i.e., subnormal or structural shrinkage phase, at the wet end. The latter behavior was also shown by amorphous top soils. With increasing degree of decomposition or complete absence of Sphagnum remains the SSC flattened and tended to show a (near-) normal shrinkage phase, i.e., volume reduction equals lost water volume.

The results showed that rigid Sphagnum remains strongly influence the shrinkage behavior of organic soils by stabilizing the matrix during desiccation until the large pores collapse rapidly when soil moisture and tension undercut a certain level. The SSC of organic soils without rigid fibers were more similar to SSCs of clayey soils.

How to cite: Seidel, R., Dettmann, U., and Tiemeyer, B.: Soil Shrinkage Characteristics of Peat and Other Organic Soils , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5066, https://doi.org/10.5194/egusphere-egu24-5066, 2024.

Peat and peat-based growing media continue to serve as the major constituents in soil-less cultivation due to their favorable physical and hydraulic characteristics. However, the substrate’s inherent high organic nature, and the intensive dehydration  process employed to compact peat into bales for cost effective transportation , results in the substrate development of water repellency. Consequently, this alters the media's optimal physical and hydraulic characteristics and reducing productivity in cultivation systems. Efforts to ameliorate substrate water repellency have predominantly involved the application of wetting agents, primarily focusing on their effect on various plant growth parameters. Synthetic surfactants were proposed to treat the substrate’s water repellency, but given the environmental concerns, alternative strategies become imperative. Biosurfactants, particularly rhamnolipids, have emerged as intriguing compounds at the scientific and commercial levels. Nonetheless, comprehensive quantitative investigations on the rate and extent of wetting and spreading behaviors of aqueous biosurfactant solutions which is essential for understanding drop penetration dynamics on peat, are currently inadequate. In this regard, the main objective of this study is to quantify the drop penetration dynamics of biosurfactants on peat porous substrate under different initial moisture conditions and on peat pellet compressed at different pressures to account for different densities and surface roughness. The study involved measurements of contact angle (CA), drop height, base diameter, and volume of aqueous biosurfactant solutions on prewetted peat with water and biosurfactant and peat pellets using optical tensiometer (OCA-15, Data Physics, Germany). The results demonstrate the relative degree of water repellency with the droplet dynamics of water exhibiting a CA of ~120⁰ and relatively constant drop height and base diameter. Conversely, biosurfactant droplets reduced drop height and volume, and the CA of 120⁰-80⁰ was dependent on prewetting conditions. Furthermore, drop penetration dynamics into pellet peat highlighted the role of surface roughness with higher CA at lower compression pressure (69 bars) relative to higher one (517 bars). Furthermore, the study revealed a pronounced dependence on biosurfactant solution surface tension (ϒ_lv), with negligible CA changes within the higher ϒ_lv ( from 72 down to 41mN/m) domain and significant alterations within the lower ϒ_lv (down to 33 mN/m) domain. These outcomes underscore the effectiveness of rhamnolipid biosurfactant in aiding drop infiltration into initially hydrophobic peat, implying its role in aiding to peat wettability.

Keywords: Peat, Pellets, water repellency, contact angle, surface tension, rhamnolipid biosurfactant, droplet dynamics.

How to cite: Duggireddy, R. and Arye, G.: Drop penetration dynamics of rhamnolipid biosurfactant on peat, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5026, https://doi.org/10.5194/egusphere-egu24-5026, 2024.

Cultivated peatlands play a significant role in grass and dairy production, particularly in Northern regions. However, agricultural activities on these organic soils often lead to undesirable environmental effects, namely increased nutrient leaching and greenhouse gas (GHG) emissions. The hydrological characteristics and dynamics of cultivated peatlands significantly influence the formation of leachable nutrients and GHGs. Currently, there is a gap in the comprehensive understanding of hydrological responses in these cultivated areas. To address this gap, the NorPeat research platform at Ruukki research station, managed by the Natural Resources Institute Finland (Luke), has been established in Northern Ostrobothnia, Finland. The site features varying peat thickness (10-80 cm) over a mineral subsoil and a subsurface drainage system consisting of perforated pipes installed within the mineral layer at a depth of 120-130 cm from the surface. Continuous hydrological monitoring of key parameters such as groundwater table, soil moisture, drainage discharge, precipitation, and soil temperature has been ongoing on the platform since 2016. In this study, we focus on the dynamics of the groundwater table and soil moisture in response to seasonal variations, soil structure, and land management; to establish a comprehensive water balance quantifying water fluxes (evapotranspiration, drain flow, overland flow) to the adjacent stream; and to develop a hydrological conceptual model of the field. The outcomes of this research are expected to improve our understanding of cultivated peatland hydrology, inform future studies on environmental impacts, and provide valuable data for both farmers and policymakers.

How to cite: Pham, T., Marttila, H., Liimatainen, M., Lötjönen, T., Kekkonen, J., Läpikivi, M., and Kløve, B.: Hydrological dynamics of a Northern cultivated peatland and implications for management, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7097, https://doi.org/10.5194/egusphere-egu24-7097, 2024.

High water content and poor trafficability are typical challenges of cultivation on peatlands. Draining of peatlands is necessary for cultivation which results in peat degradation and emission of Green House Gases (GHGs). The primary aim of this ongoing study is to understand the hydrology of “peat inversion” used as an alternative to other drainage systems in Norway. In the peat inversion method, the mineral soil layer underlying the peat soil is excavated and placed on top of the peat to provide a cover layer to limit further decomposition of peat and GHG emissions. To better understand drainage effects on hydrology, Carbon balances and GHG emissions in agricultural peatlands in Norway, we study different drainage systems located in different climatic settings. Water table behavior and the relationship with precipitation is investigated at four cultivated peatland sites: Farstad (Western Norway, wet, mild climates), Våler (Southeast Norway, dry, cold winter dominated), Sortland (Northwest Norway, mild climate), Pasvik (Northern Norway, dry, cold winter dominated). Different drainage settings including pipe drainage, surface grading and peat inversion exist in these fields.

How to cite: Gunathilake, M., Takiriti, M., Marttilla, H., Rivedal, S., and Kløve, B.: Hydrology in differently drained agricultural peatlands in Norway , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4250, https://doi.org/10.5194/egusphere-egu24-4250, 2024.

In Europe, approximately 52 % of former peatland area is strongly degraded due to human exploitation. This makes the EU the worlds’ second largest emitter of greenhouse gases from drained peatlands. Rewetting of drained peatland sites has therefore a great climate change mitigation potential, as net greenhouse gas emissions can be strongly reduced in the long term. To assess the success of rewetting actions, there is a strong demand for cost-effective and unified monitoring techniques. With the aid of cloud-based remote sensing, the field of earth observation has quickly improved in terms of data accessability and handling, which facilitates the development of individual open-access solutions for environmental monitoring, and may therefore provide suitable tools to monitor peatland rewetting.

We developed a tool to assess the status and changes of peatlands in terms of vegetation and moisture conditions. Therefore, time-series of vegetation and moisture indices (such as NDVI, NDWI) based on freely available satellite data (such as Landsat) were compiled, which provide spatially and temporally continuous information on changes in peatland ecosystems for the last decades.
Anomalies were calculated with reference to the known pre-rewetting time period of selected peatlands, and pre- and post-rewetting trends were analyzed. This provides a spatio-temporal overview of eco-hydrologic changes at individual user-defined peatland sites, which allows deriving information even for remote locations and inaccessable or protected areas. In this contribution we exemplary focus on a rewetted peatland in Northwestern Germany (Neustaedter Moor) for which we could show a clear signal in NDWI anomalies following a rewetting measure in 2013, indicating that these measures have indeed been effective.

We intend to test the application further at multiple sites in cooperation with practitioners and to assess the analysis by comparing results to field-specific data. The fully automatized multi-index approach is provided as a web-based application, which can be used to summarize and compare the advances in peatland restoration at continental scale also in the future. We aim to provide opportunities for new insights by creating synergies between earth observation and restoration practice in European Peatlands.

This research was funded through the 2020-2021 Biodiversa+ and Water JPI joint call for research projects, under the BiodivRestore ERA-NET Cofund (GA N°101003777), with the EU and the funding organisations DFG (Germany), FWF (Austria), NSC (Poland) and the LNV (The Netherlands)

How to cite: Giese, L., Renken, M., Ludwig, M., Bartel, A., Lehmann, J., Knorr, K.-H., and Meyer, H.: High-Resolution Monitoring of Eco-hydrological Changes Following Rewetting of European Peatlands – Bridging Earth Observation and Restoration Practices, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11745, https://doi.org/10.5194/egusphere-egu24-11745, 2024.