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P G Whitehead - One of the best experts on this subject based on the ideXlab platform.
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an inca model for pathogens in Rivers and catchments model structure sensitivity analysis and application to the River Thames catchment uk
Science of The Total Environment, 2016Co-Authors: P G Whitehead, Martyn N. Futter, H Leckie, K Rankinen, D Butterfield, Gianbattista BussiAbstract:Pathogens are an ongoing issue for catchment water management and quantifying their transport, loss and potential impacts at key locations, such as water abstractions for public supply and bathing sites, is an important aspect of catchment and coastal management. The Integrated Catchment Model (INCA) has been adapted to model the sources and sinks of pathogens and to capture the dominant dynamics and processes controlling pathogens in catchments. The model simulates the stores of pathogens in soils, sediments, Rivers and groundwaters and can account for diffuse inputs of pathogens from agriculture, urban areas or atmospheric deposition. The model also allows for point source discharges from intensive livestock units or from sewage treatment works or any industrial input to River systems. Model equations are presented and the new pathogens model has been applied to the River Thames in order to assess total coliform (TC) responses under current and projected future land use. A Monte Carlo sensitivity analysis indicates that the input coliform estimates from agricultural sources and decay rates are the crucial parameters controlling pathogen behaviour. Whilst there are a number of uncertainties associated with the model that should be accounted for, INCA-Pathogens potentially provides a useful tool to inform policy decisions and manage pathogen loading in River systems.
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fate and transport of polychlorinated biphenyls pcbs in the River Thames catchment insights from a coupled multimedia fate and hydrobiogeochemical transport model
Science of The Total Environment, 2016Co-Authors: Martyn N. Futter, Gianbattista Bussi, Luca Nizzetto, Monika D. Jürgens, P G WhiteheadAbstract:The fate of persistent organic pollutants (POPs) in Riverine environments is strongly influenced by hydrology (including flooding) and fluxes of sediments and organic carbon. Coupling multimedia fate models (MMFMs) and hydrobiogeochemical transport models offers unique opportunities for understanding the environmental behaviour of POPs. While MMFMs are widely used for simulating the fate and transport of legacy and emerging pollutants, they use greatly simplified representations of climate, hydrology and biogeochemical processes. Using additional information about weather, River flows and water chemistry in hydrobiogeochemical transport models can lead to new insights about POP behaviour in Rivers. As most Riverine POPs are associated with suspended sediments (SS) or dissolved organic carbon (DOC), coupled models simulating SS and DOC can provide additional insights about POPs behaviour. Coupled simulations of River flow, DOC, SS and POP dynamics offer the possibility of improved predictions of contaminant fate and fluxes by leveraging the additional information in routine water quality time series. Here, we present an application of a daily time step dynamic coupled multimedia fate and hydrobiogeochemical transport model (The Integrated Catchment (INCA) Contaminants model) to simulate the behaviour of selected PCB congeners in the River Thames (UK). This is a follow-up to an earlier study where a Level III fugacity model was used to simulate PCB behaviour in the Thames. While coupled models are more complex to apply, we show that they can lead to much better representation of POPs dynamics. The present study shows the importance of accurate sediment and organic carbon simulations to successfully predict Riverine PCB transport. Furthermore, it demonstrates the important impact of short-term weather variation on PCB movement through the environment. Specifically, it shows the consequences of the severe flooding, which occurred in early 2014 on sediment PCB concentrations in the River Thames.
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modelling the future impacts of climate and land use change on suspended sediment transport in the River Thames uk
Journal of Hydrology, 2016Co-Authors: Gianbattista Bussi, Christel Prudhomme, Simon Dadson, P G WhiteheadAbstract:The effects of climate change and variability on River flows have been widely studied. However the impacts of such changes on sediment transport have received comparatively little attention. In part this is because modelling sediment production and transport processes introduces additional uncertainty, but it also results from the fact that, alongside the climate change signal, there have been and are projected to be significant changes in land cover which strongly affect sediment-related processes. Here we assess the impact of a range of climatic variations and land covers on the River Thames catchment (UK). We first calculate a response of the system to climatic stressors (average precipitation, average temperature and increase in extreme precipitation) and land-cover stressors (change in the extent of arable land). To do this we use an ensemble of INCA hydrological and sediment behavioural models. The resulting system response, which reveals the nature of interactions between the driving factors, is then compared with climate projections originating from the UKCP09 assessment (UK Climate Projections 2009) to evaluate the likelihood of the range of projected outcomes. The results show that climate and land cover each exert an individual control on sediment transport. Their effects vary depending on the land use and on the level of projected climate change. The suspended sediment yield of the River Thames in its lowermost reach is expected to change by −4% (−16% to +13%, confidence interval, p = 0.95) under the A1FI emission scenario for the 2030s, although these figures could be substantially altered by an increase in extreme precipitation, which could raise the suspended sediment yield up to an additional +10%. A 70% increase in the extension of the arable land is projected to increase sediment yield by around 12% in the lowland reaches. A 50% reduction is projected to decrease sediment yield by around 13%.
Gianbattista Bussi - One of the best experts on this subject based on the ideXlab platform.
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Modelling metaldehyde in catchments: a River Thames case-study.
Environmental Science: Processes & Impacts, 2017Co-Authors: Paul Whitehead, Gianbattista Bussi, Martyn N. Futter, Luca NizzettoAbstract:The application of metaldehyde to agricultural catchment areas to control slugs and snails has caused severe problems for drinking water supply in recent years. In the River Thames catchment, metaldehyde has been detected at levels well above the EU and UK drinking water standards of 0.1 μg l-1 at many sites across the catchment between 2008 and 2015. Metaldehyde is applied in autumn and winter, leading to its increased concentrations in surface waters. It is shown that a process-based hydro-biogeochemical transport model (INCA-contaminants) can be used to simulate metaldehyde transport in catchments from areas of application to the aquatic environment. Simulations indicate that high concentrations in the River system are a direct consequence of excessive application rates. A simple application control strategy for metaldehyde in the Thames catchment based on model results is presented.
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fate and transport of polychlorinated biphenyls pcbs in the River Thames catchment insights from a coupled multimedia fate and hydrobiogeochemical transport model
Science of The Total Environment, 2016Co-Authors: Martyn N. Futter, Gianbattista Bussi, Luca Nizzetto, Monika D. Jürgens, P G WhiteheadAbstract:The fate of persistent organic pollutants (POPs) in Riverine environments is strongly influenced by hydrology (including flooding) and fluxes of sediments and organic carbon. Coupling multimedia fate models (MMFMs) and hydrobiogeochemical transport models offers unique opportunities for understanding the environmental behaviour of POPs. While MMFMs are widely used for simulating the fate and transport of legacy and emerging pollutants, they use greatly simplified representations of climate, hydrology and biogeochemical processes. Using additional information about weather, River flows and water chemistry in hydrobiogeochemical transport models can lead to new insights about POP behaviour in Rivers. As most Riverine POPs are associated with suspended sediments (SS) or dissolved organic carbon (DOC), coupled models simulating SS and DOC can provide additional insights about POPs behaviour. Coupled simulations of River flow, DOC, SS and POP dynamics offer the possibility of improved predictions of contaminant fate and fluxes by leveraging the additional information in routine water quality time series. Here, we present an application of a daily time step dynamic coupled multimedia fate and hydrobiogeochemical transport model (The Integrated Catchment (INCA) Contaminants model) to simulate the behaviour of selected PCB congeners in the River Thames (UK). This is a follow-up to an earlier study where a Level III fugacity model was used to simulate PCB behaviour in the Thames. While coupled models are more complex to apply, we show that they can lead to much better representation of POPs dynamics. The present study shows the importance of accurate sediment and organic carbon simulations to successfully predict Riverine PCB transport. Furthermore, it demonstrates the important impact of short-term weather variation on PCB movement through the environment. Specifically, it shows the consequences of the severe flooding, which occurred in early 2014 on sediment PCB concentrations in the River Thames.
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an inca model for pathogens in Rivers and catchments model structure sensitivity analysis and application to the River Thames catchment uk
Science of The Total Environment, 2016Co-Authors: P G Whitehead, Martyn N. Futter, H Leckie, K Rankinen, D Butterfield, Gianbattista BussiAbstract:Pathogens are an ongoing issue for catchment water management and quantifying their transport, loss and potential impacts at key locations, such as water abstractions for public supply and bathing sites, is an important aspect of catchment and coastal management. The Integrated Catchment Model (INCA) has been adapted to model the sources and sinks of pathogens and to capture the dominant dynamics and processes controlling pathogens in catchments. The model simulates the stores of pathogens in soils, sediments, Rivers and groundwaters and can account for diffuse inputs of pathogens from agriculture, urban areas or atmospheric deposition. The model also allows for point source discharges from intensive livestock units or from sewage treatment works or any industrial input to River systems. Model equations are presented and the new pathogens model has been applied to the River Thames in order to assess total coliform (TC) responses under current and projected future land use. A Monte Carlo sensitivity analysis indicates that the input coliform estimates from agricultural sources and decay rates are the crucial parameters controlling pathogen behaviour. Whilst there are a number of uncertainties associated with the model that should be accounted for, INCA-Pathogens potentially provides a useful tool to inform policy decisions and manage pathogen loading in River systems.
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modelling the future impacts of climate and land use change on suspended sediment transport in the River Thames uk
Journal of Hydrology, 2016Co-Authors: Gianbattista Bussi, Christel Prudhomme, Simon Dadson, P G WhiteheadAbstract:The effects of climate change and variability on River flows have been widely studied. However the impacts of such changes on sediment transport have received comparatively little attention. In part this is because modelling sediment production and transport processes introduces additional uncertainty, but it also results from the fact that, alongside the climate change signal, there have been and are projected to be significant changes in land cover which strongly affect sediment-related processes. Here we assess the impact of a range of climatic variations and land covers on the River Thames catchment (UK). We first calculate a response of the system to climatic stressors (average precipitation, average temperature and increase in extreme precipitation) and land-cover stressors (change in the extent of arable land). To do this we use an ensemble of INCA hydrological and sediment behavioural models. The resulting system response, which reveals the nature of interactions between the driving factors, is then compared with climate projections originating from the UKCP09 assessment (UK Climate Projections 2009) to evaluate the likelihood of the range of projected outcomes. The results show that climate and land cover each exert an individual control on sediment transport. Their effects vary depending on the land use and on the level of projected climate change. The suspended sediment yield of the River Thames in its lowermost reach is expected to change by −4% (−16% to +13%, confidence interval, p = 0.95) under the A1FI emission scenario for the 2030s, although these figures could be substantially altered by an increase in extreme precipitation, which could raise the suspended sediment yield up to an additional +10%. A 70% increase in the extension of the arable land is projected to increase sediment yield by around 12% in the lowland reaches. A 50% reduction is projected to decrease sediment yield by around 13%.
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Impacts of climate change, land-use change and phosphorus reduction on phytoplankton in the River Thames (UK)
Science of The Total Environment, 2016Co-Authors: Gianbattista Bussi, Michael J Bowes, Paul Whitehead, Daniel S. Read, Christel Prudhomme, Simon DadsonAbstract:Potential increases of phytoplankton concentrations in River systems due to global warming and changing climate could pose a serious threat to the anthropogenic use of surface waters. Nevertheless, the extent of the effect of climatic alterations on phytoplankton concentrations in River systems has not yet been analysed in detail. In this study, we assess the impact of a change in precipitation and temperature on River phytoplankton concentration by means of a physically-based model. A scenario-neutral methodology has been employed to evaluate the effects of climate alterations on flow, phosphorus concentration and phytoplankton concentration of the River Thames (southern England). In particular, five groups of phytoplankton are considered, representing a range of size classes and pigment phenotypes, under three different land-use/land-management scenarios to assess their impact on phytoplankton population levels. The model results are evaluated within the framework of future climate projections, using the UK Climate Projections 09 (UKCP09) for the 2030s. The results of the model demonstrate that an increase in average phytoplankton concentration due to climate change is highly likely to occur, with the magnitude varying depending on the location along the River Thames. Cyanobacteria show significant increases under future climate change and land use change. An expansion of intensive agriculture accentuates the growth in phytoplankton, especially in the upper reaches of the River Thames. However, an optimal phosphorus removal mitigation strategy, which combines reduction of fertiliser application and phosphorus removal from wastewater, can help to reduce this increase in phytoplankton concentration, and in some cases, compensate for the effect of rising temperature.
Simon P.g. Hoggart - One of the best experts on this subject based on the ideXlab platform.
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Macroinvertebrate richness on flood defence walls of the tidal River Thames
Urban Ecosystems, 2011Co-Authors: Simon P.g. Hoggart, Robert A. Francis, Michael A. ChadwickAbstract:The River Thames through central London has seen significant environmental recovery, particularly in regard to water quality, but a substantial barrier to further ecological improvement is the spatial restriction of riparian areas. Flood defence walls represent a potential habitat for ecological improvements to benefit biodiversity. However before restoration actions are considered, an understanding of the current biodiversity and ecological status of these structures is necessary. Physical habitat and macroinvertebrate richness of flood defence walls at 15, evenly spaced sites along a 32 Km reach in central London were evaluated. We found no longitudinal patterns in total macroinvertebrate richness among our 15 sites, but did find that richness was influenced by wall type. Specifically, we found the highest richness on brick walls and lowest richness on concrete walls. Further, wall sections with algal cover supported significantly higher numbers of macroinvertebrates than sections lacking algal cover. However, reaches of the River where the channel was constricted had fewer macroinvertebrates likely due to scouring flows. These results show that macroinvertebrates of the River walls are influenced by habitat availability (i.e., wall type) and localised River flows. This work suggests that appropriate management of River wall habitats has the potential to enhance the biodiversity of highly modified, urban Rivers.
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Urban River wall habitat and vegetation: observations from the River Thames through central London
Urban Ecosystems, 2009Co-Authors: Robert A. Francis, Simon P.g. HoggartAbstract:Along heavily engineered urban Rivers, River walls and embankments represent the most common habitat available to riparian vegetation. This paper presents the first study into River wall vegetation and the influence of wall surface materials on plant diversity. We were concerned with investigating the plant diversity of such wall habitats, assessing relationships between different wall surface materials and plant diversity, and determining whether River wall and embankment habitats along the River Thames through central London could support native riparian species alongside more typical urban wall flora. Fifteen sites along the River Thames through central London were surveyed to describe wall flora and establish relationships between plant diversity and wall materials. Walls were not species rich, but contained a mix of terrestrial and riparian species. Stone walls with surface fractures and heterogeneous wall surfaces were conducive to plant diversity at the local scale, while wall surface heterogeneity was also important at the landscape scale. Some stratification of vegetation was observed based on wall position relative to flow disturbance. The potential exists for walls to act as sites for habitat improvement and reconciliation ecology within urban Rivers.
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Meeting the challenges of urban River habitat restoration: developing a methodology for the River Thames through central London
Area, 2008Co-Authors: Robert A. Francis, Simon P.g. Hoggart, Angela M. Gurnell, Chris CoodeAbstract:The River Thames is a heavily engineered urban system in recovery, though absence of habitat in the reaches through central London has restricted recovery in this area, making habitat creation or improvement a restoration priority. Here we discuss the pre-disturbance Thames, its current ecological status, and then present a methodology for establishing habitat restoration potential through central London. Habitats primarily supporting ecological communities include inter-tidal foreshore and artificial structures, and novel techniques for improving these habitats are under development. It is hoped that such approaches along the Thames will provide a template for habitat creation along other large urban Rivers.
Heather Wickham - One of the best experts on this subject based on the ideXlab platform.
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identifying multiple stressor controls on phytoplankton dynamics in the River Thames uk using high frequency water quality data
Science of The Total Environment, 2016Co-Authors: Michael J Bowes, Heather Wickham, Sarah Harman, L K Armstrong, E. Gozzard, Daniel S. Read, Christel Prudhomme, M Loewenthal, M G Hutchins, Laurence CarvalhoAbstract:River phytoplankton blooms can pose a serious risk to water quality and the structure and function of aquatic ecosystems. Developing a greater understanding of the physical and chemical controls on the timing, magnitude and duration of blooms is essential for the effective management of phytoplankton development. Five years of weekly water quality monitoring data along the River Thames, southern England were combined with hourly chlorophyll concentration (a proxy for phytoplankton biomass), flow, temperature and daily sunlight data from the mid-Thames. Weekly chlorophyll data was of insufficient temporal resolution to identify the causes of short term variations in phytoplankton biomass. However, hourly chlorophyll data enabled identification of thresholds in water temperature (between 9 and 19 °C) and flow (<30 m3 s−1) that explained the development of phytoplankton populations. Analysis showed that periods of high phytoplankton biomass and growth rate only occurred when these flow and temperature conditions were within these thresholds, and coincided with periods of long sunshine duration, indicating multiple stressor controls. Nutrient concentrations appeared to have no impact on the timing or magnitude of phytoplankton bloom development, but severe depletion of dissolved phosphorus and silicon during periods of high phytoplankton biomass may have contributed to some bloom collapses through nutrient limitation. This study indicates that for nutrient enriched Rivers such as the Thames,manipulating residence time (through removing impoundments) and light/temperature (by increasing riparian tree shading) may offer more realistic solutions than reducing phosphorus concentrations for controlling excessive phytoplankton biomass.
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nutrient and light limitation of periphyton in the River Thames implications for catchment management
Science of The Total Environment, 2012Co-Authors: Michael J Bowes, Nicola L Ings, Stephanie Mccall, Alan Warwick, Cyril Barrett, Heather Wickham, Sarah Harman, L K Armstrong, Peter Scarlett, Colin RobertsAbstract:Abstract Soluble reactive phosphorus (SRP) concentrations in the River Thames, south east England, have significantly decreased from an annual maximum of 2100 μg l − 1 in 1997 to 344 in 2010, primarily due to the introduction of phosphorus (P) removal at sewage treatment works within the catchment. However, despite this improvement in water quality, phytoplankton biomass in the River Thames has greatly increased in recent years, with peak chlorophyll concentrations increasing from 87 μg l − 1 in the period 1997 to 2002, to 328 μg l − 1 in 2009. A series of within-River flume mesocosm experiments were performed to determine the effect of changing nutrient concentrations and light levels on periphyton biomass accrual. Nutrient enrichment experiments showed that phosphorus, nitrogen and silicon were not limiting or co-limiting periphyton growth in the Thames at the time of the experiment (August–September 2010). Decreasing ambient SRP concentration from 225 μg l − 1 to 173 μg l − 1 had no effect on periphyton biomass accrual rate or diatom assemblage. Phosphorus limitation became apparent at 83 μg SRP l − 1 , at which point a 25% reduction in periphyton biomass was observed. Diatom assemblage significantly changed when the SRP concentration was reduced to 30 μg l − 1 . Such stringent phosphorus targets are costly and difficult to achieve for the River Thames, due to the high population density and intensive agriculture within the Thames basin. Reducing light levels by shading reduced the periphyton accrual rate by 50%. Providing shading along the River Thames by planting riparian tree cover could be an effective measure to reduce the risk of excessive algal growth. If the ecology of the Thames is to reach the WFD's “good ecological status”, then both SRP concentration reductions (probably to below 100 μg l − 1 ) and increased shading will be required.
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Spatial and temporal changes in chlorophyll-a concentrations in the River Thames basin, UK: are phosphorus concentrations beginning to limit phytoplankton biomass?
Science of The Total Environment, 2012Co-Authors: Michael J Bowes, Sarah Harman, L K Armstrong, Peter Scarlett, Colin Roberts, E. Gozzard, Andrew C. Johnson, Daniel S. Read, Heather WickhamAbstract:Abstract Chlorophyll-a and nutrient concentrations were monitored at weekly intervals across 21 River sites throughout the River Thames basin, southern England, between 2009 and 2011. Despite a 90% decrease in soluble reactive phosphorus (SRP) concentration of the lower River Thames since the 1990s, very large phytoplankton blooms still occur. Chlorophyll concentrations were highest in the mid and lower River Thames and the larger tributaries. Lowest chlorophyll concentrations were observed in the smaller tributaries, despite some having very high phosphorus concentrations of over 300 μg l− 1. There was a strong positive correlation between River length and mean chlorophyll concentration (R2 = 0.82), and Rivers connected to canals had ca. six times greater chlorophyll concentration than ‘natural’ Rivers with similar phosphorus concentrations, indicating the importance that residence time has on determining phytoplankton biomass. Phosphorus concentration did have some influence, with phosphorus-enriched Rivers having much larger phytoplankton blooms than nutrient-poor Rivers of a similar length. Water quality improvements may now be capping chlorophyll peaks in the Rivers Thames and Kennet, due to SRP depletion during the spring/early summer phytoplankton bloom period. Dissolved reactive silicon was also depleted to potentially-limiting concentrations for diatom growth in the River Thames during these phytoplankton blooms, but nitrate remained in excess for all Rivers throughout the study period. Other potential mitigation measures, such as increasing riparian shading and reducing residence times by removing impoundments may be needed, alongside phosphorus mitigation, to reduce the magnitude of phytoplankton blooms in the future.
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Rainfall and runoff water quality of the Pang and Lambourn, tributaries of the River Thames, south-eastern England
Hydrology and Earth System Sciences, 2004Co-Authors: Colin Neal, Heather Wickham, Margaret Neal, Linda Hill, Richard Skeffington, R. Wyatt, N. HewittAbstract:Abstract. The water quality of rainfall and runoff is described for two catchments of two tributaries of the River Thames, the Pang and Lambourn. Rainfall chemistry is variable and concentrations of most determinands decrease with increasing volume of catch probably due to "wash out" processes. Two rainfall sites have been monitored, one for each catchment. The rainfall site on the Lambourn shows higher chemical concentrations than the one for the Pang which probably reflects higher amounts of local inputs from agricultural activity. Rainfall quality data at a long-term rainfall site on the Pang (UK National Air Quality Archive) shows chemistries similar to that for the Lambourn site, but with some clear differences. Rainfall chemistries show considerable variation on an event-to-event basis. Average water quality concentrations and flow-weighted concentrations as well as fluxes vary across the sites, typically by about 30%. Stream chemistry is much less variable due to the main source of water coming from aquifer sources of high storage. The relationship between rainfall and runoff chemistry at the catchment outlet is described in terms of the relative proportions of atmospheric and within-catchment sources. Remarkably, in view of the quantity of agricultural and sewage inputs to the streams, the catchments appear to be retaining both P and N. Keywords: water quality, nitrate, ammonium, phosphorus, ammonia, nitrogen dioxide, pH, alkalinity, nutrients, trace metals, rainfall, River, Pang, Lambourn, LOCAR
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The water quality of the River Thames at a rural site downstream of Oxford
Science of The Total Environment, 2000Co-Authors: Colin Neal, Heather Wickham, M. Harrow, Richard J. Williams, Margaret Neal, Lal C Bhardwaj, Linda HillAbstract:Water quality information is presented for the River Thames 34 km downstream of the market town of Oxford in Oxfordshire to provide an overview of the hydrochemical functioning of a major agriculturally impacted River entering the North Sea. The data, which cover the period from the spring of 1997 to the spring of 1999, relate to three types of data. These types are: (1) weekly spot sampling for determination of major, minor and trace elements, pH, alkalinity and herbicides; (2) tri-weekly spot sampling for pH, alkalinity and dissolved silicon; and (3) continuous measurements of pH and dissolved oxygen. Calcium and bicarbonate provide, respectively, the dominant cation and anion in solution and their compositions remain relatively constant through time, irrespective of flow levels. In contrast, many determinands show seasonally related fluctuations. Concentrations for most of the major anions, sodium, potassium as well as soluble reactive phosphorus and several soluble trace elements such as boron, antimony, arsenic and molybdenum decrease as flow increases. A reverse pattern is observed for nitrate, some herbicides and trace elements associated with particulate phases: concentrations increase with increasing flow. These patterns reflect the influence of: (1) a calcium carbonate rich groundwater system which provides the main stream flow component; (2) dilution of point source pollutant inputs associated with sewage and possibly light industry at high flows for several major, nutrient and trace elements; (3) enhanced nitrate and herbicide runoff from agricultural land at high flows; (4) enhanced microparticulate trace metal levels associated with increased suspended sediment loads at high flows; and (5) biological processes which affect pH, dissolved silicon, dissolved carbon dioxide and dissolved oxygen levels. An examination of soluble reactive phosphorus (SRP) and boron relationships reveals a reduction in concentrations for SRP associated possibly with phosphorus removal from a major sewage treatment works on an upstream tributary of the Thames, the Thame.
Robert A. Francis - One of the best experts on this subject based on the ideXlab platform.
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Macroinvertebrate richness on flood defence walls of the tidal River Thames
Urban Ecosystems, 2011Co-Authors: Simon P.g. Hoggart, Robert A. Francis, Michael A. ChadwickAbstract:The River Thames through central London has seen significant environmental recovery, particularly in regard to water quality, but a substantial barrier to further ecological improvement is the spatial restriction of riparian areas. Flood defence walls represent a potential habitat for ecological improvements to benefit biodiversity. However before restoration actions are considered, an understanding of the current biodiversity and ecological status of these structures is necessary. Physical habitat and macroinvertebrate richness of flood defence walls at 15, evenly spaced sites along a 32 Km reach in central London were evaluated. We found no longitudinal patterns in total macroinvertebrate richness among our 15 sites, but did find that richness was influenced by wall type. Specifically, we found the highest richness on brick walls and lowest richness on concrete walls. Further, wall sections with algal cover supported significantly higher numbers of macroinvertebrates than sections lacking algal cover. However, reaches of the River where the channel was constricted had fewer macroinvertebrates likely due to scouring flows. These results show that macroinvertebrates of the River walls are influenced by habitat availability (i.e., wall type) and localised River flows. This work suggests that appropriate management of River wall habitats has the potential to enhance the biodiversity of highly modified, urban Rivers.
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Urban River wall habitat and vegetation: observations from the River Thames through central London
Urban Ecosystems, 2009Co-Authors: Robert A. Francis, Simon P.g. HoggartAbstract:Along heavily engineered urban Rivers, River walls and embankments represent the most common habitat available to riparian vegetation. This paper presents the first study into River wall vegetation and the influence of wall surface materials on plant diversity. We were concerned with investigating the plant diversity of such wall habitats, assessing relationships between different wall surface materials and plant diversity, and determining whether River wall and embankment habitats along the River Thames through central London could support native riparian species alongside more typical urban wall flora. Fifteen sites along the River Thames through central London were surveyed to describe wall flora and establish relationships between plant diversity and wall materials. Walls were not species rich, but contained a mix of terrestrial and riparian species. Stone walls with surface fractures and heterogeneous wall surfaces were conducive to plant diversity at the local scale, while wall surface heterogeneity was also important at the landscape scale. Some stratification of vegetation was observed based on wall position relative to flow disturbance. The potential exists for walls to act as sites for habitat improvement and reconciliation ecology within urban Rivers.
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Meeting the challenges of urban River habitat restoration: developing a methodology for the River Thames through central London
Area, 2008Co-Authors: Robert A. Francis, Simon P.g. Hoggart, Angela M. Gurnell, Chris CoodeAbstract:The River Thames is a heavily engineered urban system in recovery, though absence of habitat in the reaches through central London has restricted recovery in this area, making habitat creation or improvement a restoration priority. Here we discuss the pre-disturbance Thames, its current ecological status, and then present a methodology for establishing habitat restoration potential through central London. Habitats primarily supporting ecological communities include inter-tidal foreshore and artificial structures, and novel techniques for improving these habitats are under development. It is hoped that such approaches along the Thames will provide a template for habitat creation along other large urban Rivers.
