We examine the feasibility and added value of upscaling point data of soil moisture from a small- to a mesoscale catchment for the purpose of single-event flood prediction. We test the hypothesis that in a given catchment, the present soil moisture status is a key factor governing peak discharge, flow volume and flood duration. Multiple regression analyses of rainfall, pre-event discharge, single point soil moisture profiles from representative locations and peak discharge, discharge duration, discharge volume are discussed. The soil moisture profiles are selected along a convergent slope connected to the groundwater in flood plain within the small-scale catchment Husten (2.6 km²), which is a headwater catchment of the larger Hüppcherhammer catchment (47.2 km², Germany). Results show that the number of explanatory variables in the regression models is higher in summer (up to 8 variables) than in winter (up to 3 variables) and higher in the meso-scale catchment than in the small-scale catchment (up to 2 variables). Soil moisture data from selected key locations in the small catchment improves the quality of regression models established for the meso-scale catchment. For the different target variables peak discharge, discharge duration and discharge volume the adding of the soil moisture from the flood plain and the lower slope as explanatory variable improves the quality of the regression model by 15%, 20% and 10%, respectively, especially during the summer season. In the winter season the improvement is smaller (up to 6%) and the regression models mainly include rainfall characteristics as explanatory variables. The appearance of the soil moisture variables in the stepwise regression indicates their varying importance, depending on which characteristics of the discharge are focused on. Thus, we conclude that point data for soil moisture in functional landscape elements describe the catchments’ initial conditions very well and may yield valuable information for flood prediction and warning systems.

Here for the first time, we analyze the concentration of dissolved (DOC) and particulate organic carbon (POC), as well as its optical properties (absorbance and fluorescence) from several proglacial streams across Iceland, the location of Europe’s largest non-polar ice cap. We found high spatial variability of DOC concentrations and dissolved organic matter (DOM) composition during peak melt, sampling 13 proglacial streams draining the 5 main Icelandic glaciers. Although glacial-derived organic matter (OM) was dominated by proteinaceous florescence, organic matter composition was variable among glaciers, often exhibiting relatively higher aromatic content and increased humification (based on absorbance and fluorescence measurements) closer to the glacier terminus, modulated by the presence of glacial lakes. Additional sampling locations the in flow path of the river Hvitá revealed that while POC concentrations decreased downstream, DOC concentrations and the autochthonous fraction of OM increased, suggesting the reworking of the organic carbon by microbial communities, with likely implications for downstream ecosystems as glaciers continue to melt. Based on our measured DOC concentrations ranging from 0.11 mg·L⁻¹ to 0.94 mg·L⁻¹, we estimate a potential annual carbon release of 0.008 ± 0.002 Tg·C·yr⁻¹ from Icelandic glaciers. This non-conservative first estimate serves to highlight the potentially significant contribution of Icelandic pro-glacial streams to the global carbon cycle and the need for the quantification and determination of the spatio-temporal variation of DOC and POC fluxes and their respective drivers, particularly in light of increased rates of melting due to recent trends in climatic warming.

Springs are crucial interfaces within the Earth’s Critical Zone, connecting water and its related matter and energy at different scales from the microscopic to the macroscopic level. This connectivity is of importance for habitat conditions and the invertebrate community in springs as ecotones at the groundwater–surface water and the aquatic–terrestrial interfaces in headwater regions. Here, an integrative approach regarding an appropriate theoretical framework is given as an opinion on coupling perspectives from Ecohydrology and Earth Science. A theoretical integration within the approaches of the concepts of Earth’s Critical Zone and Hydropedology with its hierarchical framework is considered for bridging multiple scales from the individual substrate type to the entire spring habitat and the headwater catchment. The paper is in every respect an opinion on theoretical approaches and provides a synthesis within a conceptual framework for spring habitats, which should give further insight into how to study such small water bodies in the context of its adjacent landscape settings.

Despite substantial research, the spatio-temporal dynamics of microplastic fluxes remain underexplored, especially in lower-order rivers. This study aims to quantify microplastic loads using a spatio-temporal sampling approach in a single cross-section of the Lahn River, a typical low-mountain river in Central Germany, over a sampling period from July 2020 to April 2021, covering varying discharge conditions, from low to high flow. A total of 198 plastic particles were detected, averaging 3.67 particles per hour, with a mean microplastic load of 0.03 ± 0.027 particles per cubic metre. Microplastic abundance varied spatially within the river cross-section, with lower concentrations found at deeper sampling positions. The data indicate that higher discharge conditions correlate with increased microplastic loads, predominantly at the water surface, suggesting that hydrological conditions significantly influence plastic transport dynamics. However, it remains unclear whether the microplastics observed at higher discharges originate from additional sources or are reactivated from river sediments. This research highlights the need for further studies to validate model assumptions and better understand the reactivation and transport mechanisms of microplastics in river systems.

Heavy metals are known to be among one of the major environmental pollutants, especially in urban areas, and, as generally known, can pose environmental risks and direct risks to humans. This study deals with the spatial distribution of heavy metals in different pavement joints in the inner city area of Marburg (Hesse, Germany). Pavement joints, defined as the joint between paving stones and filled with different materials, have so far hardly been considered as anthropogenic materials and potential pollution sources in urban areas. Nevertheless, they have an important role as possible sites of infiltration for surface run-off accumulation areas and are therefore a key feature of urban water regimes. In order to investigate the spatial variability in heavy metals in pavement joints, a geospatial sampling approach was carried out on six inner city sampling sites, followed by heavy metal analyses via inductively coupled plasma–mass spectrometry (ICP–MS) and additional pH and organic matter analyses. A first risk assessment of heavy metal pollution from pavement joints was performed. Pavement joints examined consist mainly of basaltic gravel, sands, organic material and anthropogenic artefacts (e.g. glass and plastics), with an average joint size of 0.89 cm and a vertical depth of 2–10 cm. In general, the pavement joint material shows high organic matter loads (average 11.0 % by mass) and neutral to alkaline pH values. Besides high Al and Fe content, the heavy metals Cr, Ni, Cd and Pb are mainly responsible for the contamination of pavement joints. The identified spatial pattern of maximum heavy metal loads in pavement joints could not be attributed solely to traffic emissions, as commonly reported for urban areas. Higher concentrations were detected at run-off accumulation areas (e.g. drainage gutters) and at the lowest sampling points with high drainage accumulation tendencies. Additional Spearman correlation analyses show a clear positive correlation between the run-off accumulation value and calculated exposure factor (ExF; Spearman correlation coefficients (rSP) – 0.80; p<0.00). Further correlation analyses revealed different accumulation and mobility tendencies of heavy metals in pavement joints. Based on sorption processes with humic substances and an overall alkaline pH milieu, especially Cu, Cd and Pb showed a low potential mobility and strong adsorption tendency, which could lead to an accumulation and fixation of heavy metals in pavement joints. The presence of heavy metals in pavement joints poses a direct risk for urban environments and may also affect environments out of urban areas if drainage transports accumulated heavy metals. Finally, we encourage further research to give more attention to this special field of urban anthropogenic materials and potential risks for urban environments. Overall urban geochemical background values, and the consideration of run-off-related transport processes on pavements, are needed to develop effective management strategies of urban pavement soil pollution.