Increasingly, Instream wood is (re)introduced into river systems to reverse decades of catchment mismanagement and to deliver nature-based solutions to contemporary water resource challenges such as flooding and pollutant attenuation. Most Research concerned with instream wood has focused on its ability to modify morphological and ecological conditions within a reach, but less work has considered the implications for hyporheic connectivity, a primary control of many ecosystem functions. Here, we investigate the impact of wood additions in river restoration on hyporheic exchange, at both the feature-scale and reach-scale, with the application of a before-after-control-intervention experimental design. Research was conducted over a 200m long reach of Wood Brook (Staffordshire, UK), a lowland river, which drains a 3.1km2 catchment dominated by mixed-arable farmland and deciduous woodland. The experimental reach included 3 treatment sites where channel-spanning wood features were installed, 2 sites with natural wood features, and 3 control sites that were appropriate for treatment but received no intervention. High-resolution-temperature-sensors (HRTS) were installed at these sites to capture the temperature in the surface water and at 3 hyporheic depths, up to 25cm, at 3-minute intervals. Furthermore, a series of smart tracer injections allowed us to estimate (metabolically active) transient storage before and after intervention, in both the treatment sub-reach which had received wood additions and the control sub-reach which had not. Results indicate, once background conditions are excluded from the dataset, that the mean difference between hyporheic and surface water temperatures across the treatment sites reduced by 31% over the course of the study whilst the control sites remained unchanged. Further examination determined that the daily mean temperatures observed at treatment sites were significantly different to those witnessed at the control sites. This suggests that the introduction of instream wood fostered an increase in the magnitude of hyporheic exchange. This is supported by the analysis of before-after intervention data, where a smaller deviation was observed between surface water and hyporheic temperatures across the treatment sites when compared with the control group. Preliminary analysis of smart tracer injections suggests that wood additions increase reach-scale residence times of surface water and reach-scale metabolism. The current research supports observations previously derived from flume and model-based studies, suggesting that the addition of instream wood alters the magnitude of localised hyporheic exchange. Enhanced hyporheic exchange can offer numerous benefits to a reach including: increased habitat diversity, improved primary production, and greater attenuation and transformation of pollutants. Therefore, research within this area offers valuable insights for water resource managers who are increasingly under pressure to improve the health of our riverine environments as stipulated by international policies such as the European Unions’ Water Framework Directive. While our research has contributed to advancing current knowledge surrounding how instream wood alters hyporheic connectivity, there remains numerous questions which need addressing prior to its widespread application to global watersheds.

As a pervasive, material element of the global, plastics raise potent social and environmental questions. More than merely the "stuff" of potential global prosperity, plastics are substances that people inscribe with varied cultural meanings. Deploying four conceptual "entry points" for global research, we explore how global plastics have become not only a site of an emergent socioecological crisis but themselves a point of leverage for a more humanized globalization. We approach the problem first as an exercise in reframing, shifting our viewpoint away fromdebates on waste to re-examine ideas of culture and symbolism. Then, working through the entry points of the particular, materiality and affect, we ground our argument in examples from the contemporary pandemic response, earlier ethnographic work, and our own ethnographic projects. We show how plastics have failed people's desires for a durable modernity, but nonetheless come to shape the ways they feel and think about themselves and each other as sharing responsibility for a global world.

Plastic pollution has now been found across the Earth’s active zone, with recent studies finding plastics in remote parts of the Pacific Ocean, in deep ocean trenches, and in the high Arctic. Of particular concern are microplastics (<5mm diameter), these can be ingested by organisms where they have been shown to cause both chronic and acute health problems. In order to address plastic pollution there is a need to understand how plastic in the oceans is linked to terrestrial sources. Recent conceptual models have illustrated that plastic pollution is a complex interlinked problem with myriad sources and pathways introducing and redistributing plastic around the environment. Terrestrial and freshwater sources are likely to be significant contributors to overall plastic pollution; however, to date they remain poorly understood or quantified. There is a need to both identify and quantify sources of microplastic pollution in terrestrial and freshwater environments, as well as vectors which lead to the redistribution and storage of microplastics in hotspots of accumulation. In this study we present pilot data attempting to characterise the influence of Waste Water Treatment (WWT) processes on environmental plastic pollution. Using the concept of the “Plastic Cycle” we identify various pathways for plastics present in domestic waste water to enter the environment after treatment. Using two study areas in the UK, we quantify the microplastic loading to the environment from WWT effluent, which is discharged to freshwaters, and from WWT sludge, which is spread on agricultural land as fertiliser. Our results show that both effluent and sludge are important sources of microplastics to the environment. However, these can be of the same order of magnitude as other sources indicating that addressing environmental microplastic pollution is likely to need an integrated approach. Our results also show these sources have lower loadings at some of our sites than reported in other studies, this indicates both treatment processes in WWT and management practices in sludge spreading are likely to be important in determining environmental loading of microplastics at specific sites. The influence of waste water treatment as a source of microplastic pollution needs to be further constrained, but our pilot data indicates a complex picture which needs to be better understood in order to inform environmental governance.

Channel confluences are key nodes within large river networks, and yet surprisingly little is known about their spatial and temporal evolution. Moreover, because confluences are associated with vertical scour that typically extends to several times the mean channel depth, the deposits associated with such scours should have a high preservation potential within the rock record. Paradoxically, such scours are rarely observed, and their preservation and sedimentological interpretation are poorly understood. The present study details results from a physically‐based morphodynamic model that is applied to simulate the evolution and alluvial architecture of large river junctions. Boundary conditions within the model were defined to approximate the junction of the Ganges and Jamuna rivers, Bangladesh, with the model output being supplemented by geophysical datasets collected at this junction. The numerical simulations reveal several distinct styles of sedimentary fill that are related to the morphodynamic behaviour of bars, confluence scour downstream of braid bars, bend scour and major junction scour. Comparison with existing, largely qualitative, conceptual models reveals that none of these can be applied simply, although elements of each are evident in the deposits generated by the numerical simulation and observed in the geophysical data. The characteristics of the simulated scour deposits are found to vary according to the degree of reworking caused by channel migration, a factor not considered adequately in current conceptual models of confluence sedimentology. The alluvial architecture of major junction scours is thus characterized by the prevalence of erosion surfaces in conjunction with the thickest depositional sets. Confluence scour downstream of braid bar and bend scour sites may preserve some large individual sets, but these locations are typically characterized by lower average set thickness compared to major junction scour and by a lack of large‐scale erosional surfaces. Areas of deposition not related to any of the specific scour types highlighted above record the thinnest depositional sets. This variety in the alluvial architecture of scours may go some way towards explaining the paradox of ancient junction scours, that while abundant large scours are likely in the rock record, they have been reported rarely. The present results outline the likely range of confluence sedimentology and will serve as a new tool for recognizing and interpreting these deposits in the ancient fluvial record.

There is an increasing emphasis on using natural processes, including riparian forest restoration, to enhance the ecological, hydrological and geomorphological functioning of watercourses. However, we have insufficient knowledge on how the supply and retention of in‐channel wood from riparian forest stands changes with age, with inferences typically based on data from terrestrial forests. This presents a challenge in estimating the efficacy and functional lifespan of restoration projects. In this paper, we use a riparian forest growth model to show there is a lag of up to 40–50 years between the start of forest growth and trees delivering wood to the channel that is large enough to resist fluvial transport, anchor logjams and so increase channel complexity and hydraulic resistance. Resource managers need to account for realistic timescales over which changes promoted by riparian woodland restoration will occur and may need to consider using interim engineered logjams as the forest develops.

Abstract. Peatlands play a vital role in the global carbon cycle, acting as one of the most important global carbon sinks. However, an understanding of their environmental processes, particularly in relation to a changing climate, remains inchoate. In particular, the role seasonal ice or frost layers play in altering spring water balance, and thus vulnerability to deep smoldering combustion during wildfire is not fully understood. Continental boreal peatlands are characterized by periodic wildfire disturbance, which releases carbon, but can also inhibit short-term peat productivity and carbon sequestration as the peatland recovers, with recovery timescales linked to the severity or depth of burning. The presence of seasonal frost layers coincides with drier spring conditions and an enhanced risk of wildfire. Two-dimensional numerical modelling was conducted using HYDRUS-2D, a variably saturated flow model, to simulate water balance in the vadose zone and assess vulnerability to fire during prolonged rain free periods in the presence of continuous and discontinuous frost. Our results show there is a lack of horizontal water transfer which increases spatial variability in water balance and leads to pronounced heterogeneity in the risk of smoldering combustion and the potential for deep combustion at hummock-hollow interfaces. Peatlands are broadly divided into areas which are characterized by a dry near-surface and high water contents at depth (water conserving), and those with a wetter near-surface, but comparatively lower water contents at depth (productive). Those areas with dry near-surfaces will be more vulnerable to wildfire and characterize around 50 % of hummocks and 25 % of hollows. In the presence of a seasonal frost layer productive peat layers in hollows will show substantial drying out due to the frost layer disconnecting the surface from the water table; this approximately doubles the proportion of hollows vulnerable to wildfire. Breaks in the frost layer allows areas to maintain hydrological connectivity to a falling water table, but this connectivity is limited in lateral extent and can drive further spatial heterogeneity in vulnerability to wildfire ignition in the weeks when the frost layer begins to thaw.

River channel confluences are widely acknowledged as important geomorphological nodes that control the downstream routing of water and sediment, and which are locations for the preservation of thick fluvial deposits overlying a basal scour. Despite their importance, there has been little study of the stratigraphic characteristics of river junctions, or the role of confluence morphodynamics in influencing stratigraphic character and preservation potential. As a result, although it is known that confluences can migrate through time, models of confluence geomorphology and sedimentology are usually presented from the perspective that the confluence remains at a fixed location. This is problematic for a number of reasons, not least of which is the continuing debate over whether it is possible to discriminate between scour that has been generated by autocyclic processes (such as confluence scour) and that driven by allocyclic controls (such as sea-level change). This paper investigates the spatial mobility of river confluences by using the 40-year record of Landsat Imagery to elucidate the styles, rates of change and areal extent over which large river confluence scours may migrate. On the basis of these observations, a new classification of the types of confluence scour is proposed and applied to the Amazon and Ganges-Brahmaputra-Meghna (GBM) basins. This analysis demonstrates that the drivers of confluence mobility are broadly the same as those that drive channel change more generally. Thus in the GBM basin, a high sediment supply, large variability in monsoonal driven discharge and easily erodible bank materials result in a catchment where over 80% of large confluences are mobile over this 40-year window; conversely this figure is < 40% for the Amazon basin. These results highlight that: i) the potential areal extent of confluence scours is much greater than previously assumed, with the location of some confluences on the Jamuna (Brahmaputra) River migrating over a distance of 20 times the tributary channel width; ii) extensive migration in the confluence location is more common than currently assumed, and iii) confluence mobility is often tied to the lithological and hydrological characteristics of the drainage basins that determine sediment yield.

Microplastic pollution is widespread across the globe, pervading land, water, and air. These environments are commonly considered independently, however, in reality these are closely linked. This review gives an overview of the background knowledge surrounding sources, fate and transport of microplastics within the environment. We introduce a new “Plastic Cycle” concept in order to better understand the processes influencing flux and retention of microplastics between and across the wide range of environmental matrices. As microplastics are a pervasive, persistent and potentially harmful pollutant, an understanding of these processes will allow for assessment of exposure to better determine the likely long‐term ecological and human health implications of microplastic pollution. WIREs Water 2018, 5:e1268. doi: 10.1002/wat2.1268 This article is categorized under: Engineering Water > Water, Health, and Sanitation Science of Water > Water and Environmental Change Water and Life > Stresses and Pressures on Ecosystems

(1) University of Birmingham, Geography, Earth & Environmental Science, Birmingham, United Kingdom (s.j.dixon@bham.ac.uk), (2) Geography, College of Life and Environmental Sciences, University of Exeter, Exeter EX4 4RJ, UK, (3) Departments of Geology, Geography and Geographic Information Science, Mechanical Science and Engineering and Ven Te Chow Hydrosystems Laboratory, University of Illinois at Urbana-Champaign, Illinois, USA, (4) National Oceanography Centre, University of Southampton, Southampton, SO14 3ZH, UK, (5) Department of Earth and Environmental Sciences, Vanderbilt University, Nashville, Tennessee, USA, (6) Centre for Environmental and Geographic Information Services, House 6, Road 23/C, Gulshan-1, Dhaka 1212, Bangladesh

Northern peatlands are a vital component of the global carbon cycle, containing large stores of soil organic carbon and acting as a long‐term carbon sink. Moss productivity is an important factor in determining whether these wetlands will retain this function under future climatic conditions. Research on unsaturated water flow in peatlands, which controls moss productivity during periods of evaporative stress, has focused on relatively deep bog systems. However, shallower peatlands and marginal connective wetlands can be essential components of many landscape mosaics. In order to better understand factors influencing moss productivity, water balance simulations using HYDRUS‐1D were run for different soil profile depths, compositions, and antecedent moisture conditions. Our results demonstrate a bimodal distribution of peatland realizations, either primarily conserving water by limiting evapotranspiration or maximizing moss productivity. For sustained periods of evaporative stress, both deep water storage and a shallow initial water table delay the onset of high vegetative stress, thus maximizing moss productivity. A total depth of sand and peat of 0.8 m is identified as the threshold above which increasing peat depth has no effect on changing vegetative stress response. In contrast, wetlands with shallow peat deposits (less than 0.5 m thick) are least able to buffer prolonged periods of evaporation due to limited labile water storage and will thus quickly experience vegetative stress and so limit evaporation and conserve water. With a predicted increase in the frequency and size of rain events in continental North America, the moss productivity of shallow wetland systems may increase, but also greater moisture availability will increase the likelihood they remain as wetlands in a changing climate.

The extent of urban areas is rapidly expanding across the globe, both horizontally and vertically. While natural and social scientists have examined the impacts of this urbanisation on earth system and social processes, to date researchers have largely overlooked how in turn earth system processes can act on this urban fabric to produce hybrid landforms. Unique pseudokarst landforms are found within the urban fabric, including urban stalactites and urban sinkholes. Additionally, both the chronic and acute degradation of urban buildings can form rubble and dust that, if left in situ, will be shaped by fluvial and aeolian processes. For many of these urban geomorphological processes, the neglect or abandonment of parts of the urban network will facilitate or accelerate their influence. If there are economic, climatic or social reasons for abandonment or neglect, these processes are likely to reshape parts of the urban fabric into unique landforms at a range of scales. We contend that researchers need to explicitly consider the urban fabric as an Anthropocene landform and that by doing so important insights can be gained into urban hazards and geomorphological processes. Shelley's Ozymandias, in which the eponymous king failed to account for the effects of earth system processes acting on "mighty" urban structures over time, serves as an important reminder of the impermanence of our urban works and the need to recognise and understand the processes acting on them.