Physical and biological controls on fine sediment transport and storage in rivers

Excess fine sediment, comprising particles <2 mm in diameter, is a major cause of ecological degradation in rivers. The erosion of fine sediment from terrestrial or aquatic sources, its delivery to the river, and its storage and transport in the fluvial environment are controlled by a complex interplay of physical, biological and anthropogenic factors. Whilst the physical controls exerted on fine sediment dynamics are relatively well-documented, the role of biological processes and their interactions with hydraulic and physico-chemical phenomena has been largely overlooked. The activities of biota, from primary producers to predators, exert strong controls on fine sediment deposition, infiltration and resuspension. For example, extracellular polymeric substances (EPS) associated with biofilms increase deposition and decrease resuspension. In lower energy rivers, aquatic macrophyte growth and senescence are intimately linked to sediment retention and loss, whereas riparian trees are dominant ecosystem engineers in high energy systems. Fish and invertebrates also have profound effects on fine sediment dynamics through activities that drive both particle deposition and erosion depending on species composition and abiotic conditions. The functional traits of species present will determine not only these biotic effects but also the responses of river ecosystems to excess fine sediment. We discuss which traits are involved and put them into context with spatial processes that occur throughout the river network. Whilst strides towards better understanding of the impacts of excess fine sediment have been made, further progress to identify the most effective management approaches is urgently required through close communication between authorities and scientists

The use of unmanned aerial systems for the mapping of legacy uranium mines

AbstractHistorical mining of uranium mineral veins within Cornwall, England, has resulted in a significant amount of legacy radiological contamination spread across numerous long disused mining sites. Factors including the poorly documented and aged condition of these sites as well as the highly localised nature of radioactivity limit the success of traditional survey methods. A newly developed terrain-independent unmanned aerial system [UAS] carrying an integrated gamma radiation mapping unit was used for the radiological characterisation of a single legacy mining site. Using this instrument to produce high-spatial-resolution maps, it was possible to determine the radiologically contaminated land areas and to rapidly identify and quantify the degree of contamination and its isotopic nature. The instrument was demonstrated to be a viable tool for the characterisation of similar sites worldwide

Underwater Spectroscopic Techniques for In-situ Nuclear Waste Characterisation

Decommissioning legacy spent fuel ponds within nuclear facilities can be a complicated process, largely in part due to the unknown state of materials deposited into such storage ponds during the operational lifetime of the facility. Materials may have corroded, and their condition deteriorated. Due to the nature of the materials deposited in such storage sites, minimising disturbance is desirable, and as such non-destructive techniques such as optical analysis methods are preferred over destructive techniques. In this work, we demonstrate three such optical techniques (Raman spectroscopy, photogrammetry, and hyperspectral imaging) capable of ascertaining useful characteristics of objects such as material type, surface corrosion, degradation, and 3D structure. A pool environment was used to capture data and demonstrate the techniques suitability for use in nuclear waste characterization in active spent fuel ponds. The optical techniques used enabled material characteristics to be obtained