No abstract

Our understanding of hydraulic properties of peat soils is limited compared with that of mineral substrates. In this study, we aimed to deduce possible alterations of hydraulic properties of peat soils following degradation resulting from peat drainage and aeration. A data set of peat hydraulic properties (188 soil water retention curves [SWRCs], 71 unsaturated hydraulic conductivity curves [UHCs], and 256 saturated hydraulic conductivity [Ks] values) was assembled from the literature; the obtained data originated from peat samples with an organic matter (OM) content ranging from 23 to 97 wt% (weight percent; and according variation in bulk density) representing various degrees of peat degradation. The Mualem‐van Genuchten model was employed to describe the SWRCs and UHCs. The results show that the hydraulic parameters of peat soils vary over a wide range confirming the pronounced diversity of peat. Peat decomposition significantly modifies all hydraulic parameters. A bulk density of approximately 0.2 g cm−3 was identified as a critical threshold point; above and below this value, macroporosity and hydraulic parameters follow different functions with bulk density. Pedotransfer functions based on physical peat properties (e.g., bulk density and soil depth) separately computed for bog and fen peat have significantly lower mean square errors than functions obtained from the complete data set, which indicates that not only the status of peat decomposition but also the peat‐forming plants have a large effect on hydraulic properties. The SWRCs of samples with a bulk density of less than 0.2 g cm−3 could be grouped into two to five classes for each peat type (botanical composition). The remaining SWRCs originating from samples with a bulk density of larger than 0.2 g cm−3 could be classified into one group. The Mualem‐van Genuchten parameter values of α can be used to estimate Ks if no Ks data are available. In conclusion, the derived pedotransfer functions provide a solid instrument to derive hydraulic parameter values from easily measurable quantities; however, additional research is required to reduce uncertainty.

Photodynamic therapy (PDT) is a clinical cancer treatment modality based on the induction of therapeutic reactive oxygen species (ROS), which can trigger immunogenic cell death (ICD). With the aim of simultaneously improving both PDT-mediated intracellular ROS production and ICD levels, we designed a serum albumin (SA)-coated boehmite (“B”; aluminum hydroxide oxide) organic–inorganic scaffold that could be loaded with chlorin e6 (Ce6), a photosensitizer, and a honey bee venom melittin (MLT) peptide, denoted Ce6/MLT@SAB. Ce6/MLT@SAB was anchored by a boehmite nanorod structure and exhibited particle size of approximately 180 nm. Ce6/MLT@SAB could significantly reduce hemolysis relative to that of free MLT, while providing MLT-enhanced PDT antitumor effects in vitro. Compared with Ce6@SAB, Ce6/MLT@SAB improved Ce6 penetration of cancer cells both in vitro and in vivo, thereby providing enhanced intracellular ROS generation with 660 nm light treatment. Following phototreatment, Ce6/MLT@SAB-treated cells displayed significantly improved levels of ICD and abilities to activate dendritic cells. In the absence of laser irradiation, multidose injection of Ce6/MLT@SAB could delay the growth of subcutaneous murine tumors by more than 60%, compared to controls. When combined with laser irradiation, a single injection and phototreatment with Ce6/MLT@SAB eradicated one-third of subcutaneous tumors in treated mice. The addition of an immune checkpoint blockade to Ce6/MLT@SAB phototreatment further augmented antitumor effects, generating increased numbers of CD4+ and CD8+ T cells in tumors with concomitant reduction of myeloid-derived suppressor cells.

The preferential movement of water and transport of substances play an important role in soil, but they are not yet fully understood, especially in degraded peat soil. In this study, we aimed to deduce changes in flow and transport patterns with titanium dioxide (TiO2) as a dye tracer during the course of soil degradation resulting from peat drainage. The dye tracer experiments were carried out on columns of eight types of differently degraded peat soil from three sites taken in both vertical and horizontal directions. The titanium dioxide suspension (average particle size of 0.3 µm; 10 g l−1) was applied in a pulse of 40 mm to each soil core. The cores were subsequently cut into six slices, photographed and the images were analysed for the extent of dye cover and number of pores. In addition, the saturated hydraulic conductivity (Ks) was determined. Preferential flow occurred in all of the peat types investigated. From the stained soil structural elements, we concluded that undecomposed plant remains are the major preferential flow pathways in less degraded peat. For more strongly degraded peat, bio‐pores, such as root and earthworm channels, operated as the major transport network. Results show that Ks and the effective pore network in less degraded peat soil are anisotropic. With increasing peat degradation, Ks and the cross‐section of effective pores decreased in the predominant direction only and the anisotropy of both properties decreased. The Ks was closely related to the number of macropores and pore continuity. Therefore, we conclude that changes in flow and transport pathways and Ks with increasing peat degradation result from the disintegration of the peat‐forming plant material and the decrease in number and continuity of macropores. Highlights We aimed to deduce changes in flow and transport patterns during peat degradation. TiO2 (dye tracer) was used to visualize the flow and transport patterns in degraded peat soil. The preferential flow paths, Ks and pore structures changed with peat degradation. Changes in flow and transport paths and Ks relate to peat‐forming plant materials and pore structure.

Peatlands have been drained for land use for a long time and on a large scale, turning them from carbon and nutrient sinks into respective sources, diminishing water regulation capacity, causing surface height loss and destroying biodiversity. Over the last decades, drained peatlands have been rewetted for biodiversity restoration and, as it strongly decreases greenhouse gas emissions, also for climate protection. We quantify restoration success by comparing 320 rewetted fen peatland sites to 243 near-natural peatland sites of similar origin across temperate Europe, all set into perspective by 10k additional European fen vegetation plots. Results imply that rewetting of drained fen peatlands induces the establishment of tall, graminoid wetland plants (helophytisation) and long-lasting differences to pre-drainage biodiversity (vegetation), ecosystem functioning (geochemistry, hydrology), and land cover characteristics (spectral temporal metrics). The Paris Agreement entails the rewetting of 500,000 km2 of drained peatlands worldwide until 2050-2070. A better understanding of the resulting locally novel ecosystems is required to improve planning and implementation of peatland rewetting and subsequent management.