Storm Response of Fluvial Sedimentary Microplastics

Up to 80% of the plastics in the oceans are believed to have been transferred from river networks. Microplastic contamination of river sediments has been found to be pervasive at the global scale and responsive to periods of flooding. However, the physical controls governing the storage, remobilization and pathways of transfer in fluvial sediments are unknown. This means it is not currently possible to determine the risks posed by microplastics retained within the world’s river systems. This problem will be further exacerbated in the future given projected changes to global flood risk and an increased likelihood of fluvial flooding. Using controlled flume experiments we show that the evolution of the sediment bed surface and the flood wave characteristics controls the transition from rivers being ‘sinks’ to ‘sources’ of microplastics under flood conditions. By linking bed surface evolution with microplastic transport characteristics we show that similarities exist between granular transport phenomena and the behavior, and hence predictability, of microplastic entrainment during floods. Our findings are significant as they suggest that microplastic release from sediment beds can be managed by altering the timing and magnitude of releases in flow managed systems. As such it may be possible to remediate or remove legacy microplastics in future

Hydrodynamics and sedimentary processes in the main drainage channel of a large open coast managed realignment site

Managed Realignment (MR) is becoming increasingly popular with many coastal managers and engineers. Monitoring of MR sites has provided growing evidence that many of the saltmarshes created in these environments have lower biodiversity than naturally formed intertidal marshes, and may not fully deliver the anticipated ecosystem services such as carbon sequestration and coastal flood defence. Despite the importance of the sedimentary environment in developing an intertidal morphology suitable for plant establishment and succession, the evolution of the sediment erosion, transportation, deposition and consolidation cycle in newly breached sites is rarely examined. This study evaluates the hydrodynamics and concentration of suspended sediment exported and imported along the main drainage channel within the Medmerry Managed Realignment Site, West Sussex, UK, the largest open coast realignment in Europe (at the time of breaching). Measurements were taken over a one year period (November 2015–October 2016) at the breach, at the landwards extremity where freshwater drains into the site, and in an excavated channel in the centre of the site. At the latter site, 1.7 cm of sediment accreted over the study period. Suspended sediment concentration (SSC) measurements indicate that, under ambient conditions, sediment is imported into and exported from the Medmerry site, although similar concentrations of sediment were recorded being internally redistributed around the site (typically 0.11 g/l measured in the breach area compared to 0.12 g/l measured in the centre of the site). Sediment is removed from the site following large (1–2 mm/hour) rainfall events, which take several tidal cycles to drain through the site. Peaks in SSC corresponding with lower intensity rainfall events, especially during periods when the intertidal mudflats have been exposed, have also been observed. Analysis of the hydrodynamics and patterns of sedimentation during and following storm occurrences (the 2015-16 Storms Eva, Imogen and Katie) however demonstrate the relative resilience (i.e. rapid recovery and minimal disturbance) of the site to extreme storm events.</p

Graphene oxide-based degradation of metaldehyde : effective oxidation through a modified Fenton's Process

A modified graphene oxide-based Fenton’s reaction has been investigated for the degradation of a challenging emerging contaminant which is not effectively removed in conventional water treatment. Metaldehyde, used as the challenge molecule in this study, is a common molluscicide that (like many highly soluble contaminants) has frequently breached European regulatory limits in surface waters. The new method involves graphene with higher hydrophilic characteristics (single-layer graphene oxide, SLGO) as a system that participates in a redox reaction with hydrogen peroxide and which can potentially stabilize the radical dotOH generated, which subsequently breaks down organic contaminants. The modified Fenton’s reaction has shown to be effective in degrading metaldehyde in natural waters (&gt;92% removal), even at high contaminant concentrations (50 mg metaldehyde/L) and in the presence of high background organic matter and dissolved salts. The reaction is relatively pH insensitive. SLGO maintained its catalytic performance over 3 treatment cycles when immobilized. Its performance gradually decreased over time, reaching around 50% of starting performance on the 10th treatment cycle. X-ray photoelectron spectroscopy (XPS) analysis of modifications caused in SLGO by the oxidizing treatment indicated that the oxidation of Csingle bondC sp2 to carbonyl groups may be the cause of the decrease in performance. The proposed modified Fenton’s process has the potential to substitute traditional Fenton’s treatment although regeneration of the nanocarbon is required for its prolonged use

Graphene oxide-based degradation of metaldehyde: Effective oxidation through a modified Fenton’s process

A modified graphene oxide-based Fenton’s reaction has been investigated for the degradation of a challenging emerging contaminant which is not effectively removed in conventional water treatment. Metaldehyde, used as the challenge molecule in this study, is a common molluscicide that (like many highly soluble contaminants) has frequently breached European regulatory limits in surface waters. The new method involves graphene with higher hydrophilic characteristics (single-layer graphene oxide, SLGO) as a system that participates in a redox reaction with hydrogen peroxide and which can potentially stabilize theOH generated, which subsequently breaks down organic contaminants. The modified Fenton’s reaction has shown to be effective in degrading metaldehyde in natural waters (>92% removal), even at high contaminant concentrations (50mgmetaldehyde/L) and in the presence of high background organic matter and dissolved salts. The reaction is relatively pH insensitive. SLGO maintained its catalytic performance over 3 treatment cycles when immobilized. Its performance gradually decreased over time, reaching around 50% of starting performance on the 10th treatment cycle. X-ray photoelectron spectroscopy (XPS) analysis of modifications caused in SLGO by the oxidizing treatment indicated that the oxidation of CC sp2to carbonyl groups may be the cause of the decrease in performance. The proposed modified Fenton’s process has the potential to substitute traditional Fenton’s treatment although regeneration of the nanocarbon is required for its prolonged use

A simple method for the production of large volume 3D macroporous hydrogels for advanced biotechnological, medical and environmental applications

The development of bulk, three-dimensional (3D), macroporous polymers with high permeability, large surface area and large volume is highly desirable for a range of applications in the biomedical, biotechnological and environmental areas. The experimental techniques currently used are limited to the production of small size and volume cryogel material. In this work we propose a novel, versatile, simple and reproducible method for the synthesis of large volume porous polymer hydrogels by cryogelation. By controlling the freezing process of the reagent/polymer solution, large-scale 3D macroporous gels with wide interconnected pores (up to 200??m in diameter) and large accessible surface area have been synthesized. For the first time, macroporous gels (of up to 400?ml bulk volume) with controlled porous structure were manufactured, with potential for scale up to much larger gel dimensions. This method can be used for production of novel 3D multi-component macroporous composite materials with a uniform distribution of embedded particles. The proposed method provides better control of freezing conditions and thus overcomes existing drawbacks limiting production of large gel-based devices and matrices. The proposed method could serve as a new design concept for functional 3D macroporous gels and composites preparation for biomedical, biotechnological and environmental applications

Sediment structure and physicochemical changes following tidal inundation at a large open coast managed realignment site

Managed realignment (MR) schemes are being implemented to compensate for the loss of intertidal saltmarsh habitats by breaching flood defences and inundating the formerly defended coastal hinterland. However, studies have shown that MR sites have lower biodiversity than anticipated, which has been linked with anoxia and poor drainage resulting from compaction and the collapse of sediment pore space caused by the site's former terrestrial land use. Despite this proposed link between biodiversity and soil structure, the evolution of the sediment sub-surface following site inundation has rarely been examined, particularly over the early stages of the terrestrial to marine or estuarine transition. This paper presents a novel combination of broad- and intensive-scale analysis of the sub-surface evolution of the Medmerry Managed Realignment Site (West Sussex, UK) in the three years following site inundation. Repeated broad-scale sediment physiochemical datasets are analysed to assess the early changes in the sediment subsurface and the preservation of the former terrestrial surface, comparing four locations of different former land uses. Additionally, for two of these locations, high-intensity 3D-computed X-ray microtomography and Itrax micro-X-ray fluorescence spectrometry analyses are presented. Results provide new data on differences in sediment properties and structure related to the former land use, indicating that increased agricultural activity leads to increased compaction and reduced porosity. The presence of anoxic conditions, indicative of poor hydrological connectivity between the terrestrial and post-inundation intertidal sediment facies, was only detected at one site. This site has experienced the highest rate of accretion over the terrestrial surface (ca. 7 cm over 36 months), suggesting that poor drainage is caused by the interaction (or lack of) between sediment facies rather than the former land use. This has significant implications for the design of future MR sites in terms of preparing sites, their anticipated evolution, and the delivery of ecosystem services

Fibre Reinforced Geopolymer versus Conventional Reinforced Concrete layers for the structural strengthening of RC beams

A common technique used to increase the flexural capacity of RC beams is the external application of RC layers. In this case, crucial parameter for the efficiency of the examined technique is the connection between the new layer and the existing concrete, since lack of sufficient connection at the interface may lead to premature failure of the strengthened elements. Another crucial parameter for the durability of the strengthened elements is the corrosion of the reinforcement of the layers. In the current study, fibre reinforced geopolymer concrete layers reinforced with steel bars were used for the flexural strengthening of reinforced concrete beams. Accelerated corrosion tests were conducted followed by flexural loading. The results indicate that, the addition of fibre reinforced geopolymer concrete offers improved load performance and durability, since higher maximum load increment was observed and the effect of corrosion was found to be negligible.</p