Academic Papers

@article{Najdanovic2017,
title = {Kinetics of extraction and in situ transesterification of oils from spent coffee grounds.},
author = {Vesna Najdanovic and
Lee Yee-Lam Lee and
Marcia Tavares and
Alona Armstrong },
url = {http://eprints.lancs.ac.uk/85993/1/1_s2.0_S2213343717301781_main.pdf},
doi = {10.1016/j.jece.2017.04.041},
year = {2017},
date = {2017-06-01},
journal = {Journal of Environmental Chemical Engineering},
volume = {5},
number = {3},
pages = {2611-2616},
abstract = {Resource limits, environmental concerns and unstable petroleum costs have led to an increased effort to develop alternative liquid fuels. Purpose grown feedstocks are expensive and demand additional resources such as land and water. Spent coffee grounds (SCGs) are a good potential low-cost feedstock, however, processing times and costs must be lowered in order to be cost competitive with fossil fuels.

In this work, we investigated the kinetics of oil extraction from SCGs to explore if current methods of oil extraction could be hastened and an integrated process which couples oil extraction and conversion to biodiesel stages in one single step (in situ transesterification) which could significantly cut down biodiesel production costs.

Kinetics of oil extraction from SCGs using n-hexane as solvent was studied as a function of temperature, solvent to solid ratio and water content. We have found that oil extraction times could be significantly reduced to 10 minutes due to high diffusion coefficients. Further, we demonstrate, for the first time, the successful in situ transesterification of SCGs using different concentration of sodium hydroxide as catalyst and methanol to oil mole ratio, promising lower biodiesel production costs from a ubiquitous waste product around the world.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{Armstrong2016-2,
title = {Solar park microclimate and vegetation management effects on grassland carbon cycling.},
author = {Alona Armstrong and
Nicholas John Ostle and
Jeanette Whitaker},
url = {http://eprints.lancs.ac.uk/80413/1/2016_ERL_solar.pdf},
doi = {10.1088/1748-9326/11/7/074016},
year = {2016},
date = {2016-07-13},
journal = {Environmental Research Letters},
volume = {11},
number = {7},
abstract = {Increasing energy demands and the drive towards low carbon (C) energy sources has prompted a rapid increase in ground-mounted solar parks across the world. This represents a significant global land use change with implications for the hosting ecosystems that are poorly understood. In order to investigate the effects of a typical solar park on the microclimate and ecosystem processes, we measured soil and air microclimate, vegetation and greenhouse gas emissions for twelve months under photovoltaic (PV) arrays, in gaps between PV arrays and in control areas at a UK solar park sited on species-rich grassland. Our results show that the PV arrays caused seasonal and diurnal variation in air and soil microclimate. Specifically, during the summer we observed cooling, of up to 5.2 °C, and drying under the PV arrays compared with gap and control areas. In contrast, during the winter gap areas were up to 1.7 °C cooler compared with under the PV arrays and control areas. Further, the diurnal variation in both temperature and humidity during the summer was reduced under the PV arrays. We found microclimate and vegetation management explained differences in the above ground plant biomass and species diversity, with both lower under the PV arrays. Photosynthesis and net ecosystem exchange in spring and winter were also lower under the PV arrays, explained by microclimate, soil and vegetation metrics. These data are a starting point to develop understanding of the effects of solar parks in other climates, and provide evidence to support the optimisation of solar park design and management to maximise the delivery of ecosystem services from this growing land use.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{Armstrong2016,
title = {Ground-level climate at a peatland wind farm in Scotland is affected by wind turbine operation.},
author = {Alona Armstrong and
Ralph Burton and
Susan Lee and
Stephen Mobbs and
Nicholas John Ostle and
Victoria Smith and
Susan Waldron and
Jeanette Whitaker},
url = {http://eprints.lancs.ac.uk/79454/1/2016_ERL_wind.pdf},
doi = {10.1088/1748-9326/11/4/044024},
year = {2016},
date = {2016-04-22},
journal = {Environmental Research Letters},
volume = {11},
number = {4},
abstract = {The global drive to produce low-carbon energy has resulted in an unprecedented deployment of onshore wind turbines, representing a significant land use change for wind energy generation with uncertain consequences for local climatic conditions and the regulation of ecosystem processes. Here, we present high-resolution data from a wind farm collected during operational and idle periods that shows the wind farm affected several measures of ground-level climate. Specifically, we discovered that operational wind turbines raised air temperature by 0.18 °C and absolute humidity (AH) by 0.03 g m−3 during the night, and increased the variability in air, surface and soil temperature throughout the diurnal cycle. Further, the microclimatic influence of turbines on air temperature and AH decreased logarithmically with distance from the nearest turbine. These effects on ground-level microclimate, including soil temperature, have uncertain implications for biogeochemical processes and ecosystem carbon cycling, including soil carbon stocks. Consequently, understanding needs to be improved to determine the overall carbon balance of wind energy.
},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{Armstrong2015,
title = {Biotic and abiotic factors interact to regulate Northern peatland carbon cycling.},
author = {Alona Armstrong and
Susan Waldron and
Nicholas J. Ostle and
Harriett Richardson and
Jeanette Whitaker},
url = {http://eprints.lancs.ac.uk/81057/1/2015_Ecosystems_biotic_and_abiotic_peatland.pdf},
doi = {10.1007/s10021-015-9907-4},
year = {2015},
date = {2015-12-01},
journal = {Ecosystems},
volume = {18},
number = {8},
pages = {1395-1409},
abstract = {Understanding the spatio-temporal variability of controls on peatland carbon (C) cycling is essential to project the effects of future environmental change. While there is understanding of individual drivers of C cycling, the effect of multiple drivers, including interactions, remains poorly understood. Using a spatially and temporally explicit sampling framework, we examined the effects of biotic and abiotic controls on key indicators of peatland functioning: ecosystem respiration (R (eco)), photosynthesis (P (cal)), net ecosystem exchange (NEE), methane (CH4) fluxes, and pore water dissolved organic carbon concentration ([DOC]). Measurements were made over 12 months in a blanket peatland hosting a wind farm in Scotland, UK. Overall, we found that (i) season and plant functional type (PFT) explained most variation in R (eco) and P (cal), (ii) PFT and spatial location within the wind farm, which integrates several peat properties, were dominant predictors of CH4 fluxes, and (iii) season and location within the wind farm correlated with pore water [DOC]. Examination of predictors indicated that interactions, between and within biotic and abiotic factors, explained a significant amount of variation in greenhouse gas fluxes and [DOC]. These findings indicate that combinations of biotic and abiotic factors could mediate or exacerbate the effects of future environmental change on peatland C cycling. Given this, studies of C cycling need to capture the spatial and temporal variance of biotic and abiotic factors and their interactions to project the likely impacts of environmental change.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{Padfield2015,
title = {Research agendas for the sustainable management of tropical peatland in Malaysia},
author = {Rory Padfield and
Susan Waldron and
Simon Drew and
Effie Papargyropoulou and
Shashi Kumaran and
Sue Page and
Dave Gilvear and
Alona Armstrong and
Stephanie Evers and
Paul Williams and
Zuriati Zakaria and
Sing Yun Chin and
Sune Balle Hansen and
Ahimsa Campos-Arceiz and
Mohd Talib Latif and
Alex Sayok and
Mun Hou Tham},
doi = {10.1017/S0376892914000034},
year = {2015},
date = {2015-03-01},
journal = {Environmental Conservation},
volume = {42},
number = {1},
pages = {73-83},
abstract = {There is a need for coordinated research for the sustainable management of tropical peatland. Malaysia has 6% of global tropical peat by area and peatlands there are subject to land use change at an unprecedented rate. This paper describes a stakeholder engagement exercise that identified 95 priority research questions for peatland in Malaysia, organized into nine themes. Analysis revealed the need for fundamental scientific research, with strong representation across the themes of environmental change, ecosystem services, and conversion, disturbance and degradation. Considerable uncertainty remains about Malaysia's baseline conditions for peatland, including questions over total remaining area of peatland, water table depths, soil characteristics, hydrological function, biogeochemical processes and ecology. More applied and multidisciplinary studies involving researchers from the social sciences are required. The future sustainability of Malaysian peatland relies on coordinating research agendas via a ‘knowledge hub’ of researchers, strengthening the role of peatlands in land-use planning and development processes, stricter policy enforcement, and bridging the divide between national and provincial governance. Integration of the economic value of peatlands into existing planning regimes is also a stakeholder priority. Finally, current research needs to be better communicated for the benefit of the research community, for improved societal understanding and to inform policy processes.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{Armstrong2014,
title = {Wind farm and solar park effects on plant–soil carbon cycling: uncertain impacts of changes in ground-level microclimate},
author = {Alona Armstrong and
Susan Waldron and
Jeanette Whitaker and
Nick Ostle},
url = {http://eprints.lancs.ac.uk/69530/1/gcb12437.pdf},
doi = {10.1111/gcb.12437},
year = {2014},
date = {2014-06-01},
journal = {Global Change Biology},
volume = {20},
number = {6},
pages = {1699-1706},
abstract = {Global energy demand is increasing as greenhouse gas driven climate change progresses, making renewable energy sources critical to future sustainable power provision. Land-based wind and solar electricity generation technologies are rapidly expanding, yet our understanding of their operational effects on biological carbon cycling in hosting ecosystems is limited. Wind turbines and photovoltaic panels can significantly change local ground-level climate by a magnitude that could affect the fundamental plant–soil processes that govern carbon dynamics. We believe that understanding the possible effects of changes in ground-level microclimates on these phenomena is crucial to reducing uncertainty of the true renewable energy carbon cost and to maximize beneficial effects. In this Opinions article, we examine the potential for the microclimatic effects of these land-based renewable energy sources to alter plant–soil carbon cycling, hypothesize likely effects and identify critical knowledge gaps for future carbon research.
},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{Drew2013,
title = {The price of knowledge in the knowledge economy: Should development of peatland in the UK support a research levy?},
author = {Simon Drew and
Susan Waldron and
David Gilvear and
Ian Grieve and
Alona Armstrong and
Olivia Bragg and
Francis Brewis and
Mark Cooper and
Tom Dargie and
Colin Duncan and
Lorna Harris and
Lorraine Wilson and
Cameron McIver and
Rory Padfield and
Nadeem Shah},
doi = {10.1016/j.landusepol.2012.10.007},
year = {2013},
date = {2013-05-01},
journal = {Land Use Policy},
volume = {32},
pages = {50-60},
abstract = {Peatlands provide a wide range of ecosystem services, the most important of which are terrestrial carbon storage, maintenance of biodiversity and protection of water resources. Exploitation of UK peatlands may be detrimental to these services, but scientific understanding and quantification of the effects is currently limited. This paper considers the possibility of imposing a levy on the exploitation of peatland, which would be used to fund high-quality prioritised research into the impacts of such human interventions, thereby enabling improvements to environmental management during the development process. The viability of the concept was explored with a group of peatland stakeholders. The group included most of the significant stakeholders with an interest in development on peatland, including regulators, developers and consultants. Qualitative and semi-quantitative responses were gathered by direct consultation with individuals and using a questionnaire to determine group responses. The latter were generally positive. Offered a choice of research funding mechanisms, stakeholders responded most positively to a levy. Whilst other funding mechanisms were also viewed positively a levy (in the form proposed or with some modification) was regarded as equitable by a large majority and workable by a smaller majority. Developers were reluctant to pledge full support to the proposal but recognised the importance of a number of the concerns that it was designed to address. Crown Copyright (C) 2012 Published by Elsevier Ltd. All rights reserved.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{Armstrong2012-3,
title = {Thermal enhancement of natural magnetism as a tool for tracing eroded soil.},
author = {Alona Armstrong and
John Quinton and
Barbara Maher},
doi = {10.1002/esp.3312},
year = {2012},
date = {2012-11-01},
journal = {Earth Surface Processes and Landforms},
volume = {37},
number = {14},
pages = {1567-1572},
abstract = {Determining sources, quantities and travel distances of eroding soil is of increasing importance given its impact on- and off-site, the sediment-associated transport of nutrients, metals and micro-organisms and the ongoing need to provide data for soil erosion model development and validation. Many soil tracers have been developed; however, most comprise foreign materials, such as fluorescent beads and rare earth oxides,which cast doubts on the validity of tracing results given their different physical characteristics.
To avoid these problems, we have investigated the potential of soil, which has been heated under reducing conditions to enhance its ferrimagnetic content, as a soil erosion tracer; while the technique has been used successfully to trace river sediment it has not been successfully applied to soil erosion studies. For a suite of 16 magnetic concentration-dependent properties, values were found to be
significantly greater, by at least one order of magnitude, after heating, both for the bulk soil and nine individual particle size fractions.
Individual size fractions could be differentiated using two different magnetic properties, thus illustrating the technique’s potential to provide information on particle size-specific erosion. Soil box experiments demonstrated the potential for both in situ measurement of magnetic susceptibility and laboratory measurement of the magnetic properties of eroded sediment, to trace and quantify soil erosion. Thus, heated soil, with artificially-enhanced ferrimagnetic properties, is successfully demonstrated to have great potential as a
size-specific, cost-effective and representative soil erosion tracer.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{Armstrong2012-2,
title = {Multi-scale relationship between peatland vegetation type and dissolved organic carbon concentration.},
author = {A. Armstrong and
J. Holden and
K. Luxton and
J. N. Quinton},
doi = {10.1016/j.ecoleng.2012.06.027},
year = {2012},
date = {2012-10-01},
journal = {Ecological Engineering},
volume = {47},
pages = {182-188},
abstract = {Dissolved organic carbon (DOC) is a key component of the carbon cycle and has significant impacts on aquatic ecosystems and potable water treatment. Upward trends in river and lacaustrine DOC concentrations have been observed and a number of key drivers have been proposed. Here, we present DOC concentration data from plot scale pore waters at one site and surface water from artificial drains sampled within a national survey which demonstrate a significant correlation between peatland vegetation type and DOC concentration. Calluna dominance was associated with the highest DOC concentration, Molinia and Sphagnum dominance with lower concentrations, and sedge dominance with intermediate concentrations. Water sampled from drains dominated by Calluna had greater DOC concentrations than water sampled from pore waters in plots dominated by Calluna. In contrast DOC concentrations from plots dominated by sedges were greater than those sampled from drains dominated by sedges. We discuss these findings in relation to plant functional traits and their influence on the physical and biotic conditions that regulate DOC concentrations. Given the known effects of management activities and climate change on peatland vegetation composition there is potential to manage plant community composition to ameliorate the observed rising DOC concentration. (C) 2012 Elsevier B.V. All rights reserved.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{Novara2012,
title = {Effects of soil compaction, rain exposure and their interaction on soil carbon dioxide emission.},
author = {Agata Novara and
Alona Armstrong and
Luciano Gristina and
Kirk T. Semple and
John N. Quinton},
doi = {10.1002/esp.3224},
year = {2012},
date = {2012-07-01},
journal = {Earth Surface Processes and Landforms},
volume = {37},
number = {9},
pages = {994-999},
abstract = {Soils release more carbon, primarily as carbon dioxide (CO2), per annum than current global anthropogenic emissions. Soils emit CO2 through mineralization and decomposition of organic matter and respiration of roots and soil organisms. Given this, the evaluation of the effects of abiotic factors on microbial activity is of major importance when considering the mitigation of greenhouse gases emissions. Previous studies demonstrate that soil CO2 emission is significantly affected by temperature and soil water content. A limited number of studies have illustrated the importance of bulk density and soil surface characteristics as a result of exposure to rain on CO2 emission, however, none examine their relative importance. Therefore, this study investigated the effects of soil compaction and exposure of the soil surface to rainfall and their interaction on CO2 release. We conducted a factorial laboratory experiment with three soil types after sieving (clay, silt and sand soil), three different bulk densities (1.1?g cm3, 1.3?g cm3, 1.5?g cm3) and three different exposures to rainfall (no rain, 30 minutes and 90 minutes of rainfall). The results demonstrated CO2 release varied significantly with bulk density, exposure to rain and time. The relationship between rain exposure and CO2 is positive: CO2 emission was 53% and 42% greater for the 90 minutes and 30 minutes rainfall exposure, respectively, compared to those not exposed to rain. Bulk density exhibited a negative relationship with CO2 emission: soil compacted to a bulk density of 1.1?g cm3 emitted 32% more CO2 than soil compacted to 1.5?g cm3. Furthermore we found that the magnitude of CO2 effluxes depended on the interaction of these two abiotic factors. Given these results, understanding the influence of soil compaction and raindrop impact on CO2 emission could lead to modified soil management practices which promote carbon sequestration. Copyright (C) 2012 John Wiley & Sons, Ltd.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{Armstrong2012,
title = {Processes controlling the development of a shielding layer on natural soil.},
author = {A. Armstrong and
John Quinton and
B. C. P. Heng and
G. C. Sander},
doi = {10.1111/j.1365-2389.2011.01416.x},
year = {2012},
date = {2012-02-01},
journal = {European Journal of Soil Science},
volume = {63},
number = {1},
pages = {54-64},
abstract = {A significant amount of research focusing on the formation of surface seals and crusts and their effect on erosion can be found in the literature. In contrast, there has been limited research investigating the formation of surface shields, a layer of loose coarse sediment on the soil surface, despite the consequences for the transport of sediment, nutrients, metals and microorganisms. This study used rainfall simulation to examine the role of slope (2 and 10%), infiltration (with and without) and ponding depth (0, 0.3 and 0.7 cm) on the development of surface shields on a silt loam and a loamy sand soil. The results show that a continuous surface shield of loose coarse particles developed on the loamy sand, whereas the silt loam soil surface was covered by varying proportions of aggregates, compacted soil and loose coarse particles. Infiltration had a limited positive impact on shield development and both slope and ponding depth were significant controls over the development of the surface characteristics.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{Armstrong2011-2,
title = {Controls over nutrient dynamics in overland flows on slopes representative of agricultural land in North West Europe.},
author = {A. Armstrong and
J. N. Quinton and
B. Francis and
B. C. P. Heng and
G. C. Sander},
doi = {10.1016/j.geoderma.2011.04.011},
year = {2011},
date = {2011-08-15},
journal = {Geoderma},
volume = {164},
number = {1-2},
pages = {2-10},
abstract = {Several models and risk assessments that estimate nutrient transfer from agricultural land have been developed. The majority of these associate increased particulate or total nutrient transfer with increased slope and do not make any inferences on the impact of slope on the transfer of nutrients in solution. These models and risk assessments are increasingly used for water quality assessments as part of the implementation of the European Union Water Framework Directive. To illustrate that these conventional assumptions may be ill-founded when considering total phosphorous, total nitrogen, total carbon, soluble reactive phosphorous, total dissolved phosphorous and nitrate transfer on slope ranges representative of agricultural land in North West Europe we present results from laboratory rainfall experiments using a large soil flume, a silt loam soil, slopes of 3%, 6% and 9% and a rainfall intensity of 47 mm hr(-1). The results show that: (1) with the exception of nitrate, nutrient transfer was as variable between repeats as between slopes: (2) discharge, time since onset of runoff sediment concentration, slope and sediment size were all dominant controls over nutrient transfer and (3) there was a relationship in the ratio of nutrient concentration to sediment concentration with slope which was attributed to the impact of sediment source and proportion of organics due to different surface connectivity, flow threads and ponding. Consequently, this questions the used of models and risk assessments which rely on slope as a driver when assessing nutrient transfer from low slopes. (C) 2011 Elsevier B.V. All rights reserved.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{Wilson2011-2,
title = {The impact of drain blocking on an upland blanket bog during storm and drought events, and the importance of sampling-scale.},
author = {Lorraine Wilson and
Jared Wilson and
Joseph Holden and
Ian Johnstone and
Alona Armstrong and
Michael Morris},
doi = {10.1016/j.jhydrol.2011.04.030},
year = {2011},
date = {2011-07-11},
journal = {Journal of Hydrology},
volume = {404},
number = {3-4},
pages = {198-208},
abstract = {Organic carbon solution and transport processes which occur during periods of heavy rainfall and periods or little or no rainfall, can exert a significant control over a systems' annual organic carbon budget. In addition, either or both extremes can be key contributors to contaminant release, water discolouration, flood risk or vegetation growth. Although there is an increasing body of work studying hydrological responses to peatland restoration, there are very little available data on the performance of restored peatlands during these key periods. This study builds on previous work from an upland peatland in Wales that has been restored through drain-blocking, and presents evidence from a landscape scale experimental study at the site. A comparison of sampling scales within the study demonstrates the necessity of larger spatial scales, in combination with high resolution datasets, in assessing catchment level responses. Our results suggest that drain blocking leads to higher and more stable water tables that are able to better resist drought periods, and thus lead to more stable discharge from the system. The shallower water tables and pooling in drains also appear to reduce the production and transport of fluvial organic carbon, and thus less organic material is available to be released as during peak flow or dry periods. Despite restoration apparently reducing the available water storage within the peat, the increase in overland flow and in pooling within blocked drains appears to have led to a less flashy system. Peak flow responses in both drains and upland streams are less severe, with more rainfall being retained within the bog. We suggest that restoration leads to a more buffered system, with more moderate responses to extreme events, and reduced release of both dissolved and particulate organic carbon. We discuss the implications of this for fluxes of fluvial organic carbon and sediment loss. (C) 2011 Elsevier B.V. All rights reserved.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{Wilson2011,
title = {Ditch blocking, water chemistry and organic carbon flux: Evidence that blanket bog restoration reduces erosion and fluvial carbon loss.},
author = {Lorraine Wilson and
Jared Wilson and
Joseph Holden and
Ian Johnstone and
Alona Armstrong and
Michael Morris},
doi = {10.1016/j.scitotenv.2011.02.036},
year = {2011},
date = {2011-05-01},
journal = {Science of the Total Environment},
volume = {409},
number = {11},
pages = {2010-2018},
abstract = {The potential for restoration of peatlands to deliver benefits beyond habitat restoration is poorly understood. There may be impacts on discharge water quality, peat erosion, flow rates and flood risk, and nutrient fluxes. This study aimed to assess the impact of drain blocking, as a form of peatland restoration, on an upland blanket bog, by measuring water chemistry and colour, and loss of both dissolved (DOC) and particulate organic carbon (POC). The restoration work was designed to permit the collection of a robust experimental dataset over a landscape scale, with data covering up to 3 years pre-restoration and up to 3 years post-restoration. An information theoretic approach to data analyses provided evidence of a recovery of water chemistry towards more 'natural' conditions, and showed strong declines in the production of water colour. Drain blocking led to increases in the E4:E6 ratio, and declines in specific absorbance, suggesting that DOC released from blocked drains consisted of lighter, less humic and less decomposed carbon. Whilst concentrations of DOC showed slight increases in drains and streams after blocking, instantaneous yields of both DOC and POC declined markedly in streams over the first year post-restoration. Attempts were made to estimate total annual fluvial organic carbon fluxes for the study site, and although errors around these estimates remain considerable, there is strong evidence of a large reduction in aquatic organic carbon flux from the peatland following drain-blocking. Potential mechanisms for the observed changes in water chemistry and organic carbon release are discussed, and we highlight the need for more detailed information, from more sites, to better understand the full impacts of peatland restoration on carbon storage and release. (C) 2011 Elsevier BM. All rights reserved.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{Heng2011,
title = {Modeling the dynamics of soil erosion and size-selective sediment transport over nonuniform topography in flume-scale experiments.},
author = {B. C. P. Heng and
G. C. Sander and
A. Armstrong and
John Quinton and
J. H. Chandler and
C. F. Scott},
url = {http://eprints.lancs.ac.uk/51378/1/Heng_et_al._2011.pdf},
doi = {10.1029/2010wr009375},
year = {2011},
date = {2011-02-10},
journal = {Water Resources Research},
volume = {47},
number = {2},
abstract = {Soil erosion and the associated nutrient fluxes can lead to severe degradation of surface waters. Given that both sediment transport and nutrient sorption are size selective, it is important to predict the particle size distribution (PSD) as well as the total amount of sediment being eroded. In this paper, a finite volume implementation of the Hairsine-Rose soil erosion model is used to simulate flume-scale experiments with detailed observations of soil erosion and sediment transport dynamics. The numerical implementation allows us to account for the effects of soil surface microtopography (measured using close range photogrammetry) on soil erosion. An in-depth discussion of the model parameters and the constraints is presented. The model reproduces the dynamics of sediment concentration and PSD well, although some discrepancies can be observed. The calibrated parameters are also consistent with independent data in the literature and physical reason. Spatial variations in the suspended and deposited sediment and an analysis of model sensitivity highlight the value of collecting distributed data for a more robust validation of the model and to enhance parametric determinacy. The related issues of spatial resolution and scale in erosion prediction are briefly discussed.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{Armstrong2011,
title = {Variability of interrill erosion at low slopes.},
author = {A. Armstrong and
J. N. Quinton and
B. C. P. Heng and
J. H. Chandler},
doi = {10.1002/esp.2024},
year = {2011},
date = {2011-01-01},
journal = {Earth Surface Processes and Landforms},
volume = {36},
number = {1},
pages = {97-106},
abstract = {Numerous models and risk assessments have been developed in order to estimate soil erosion from agricultural land, with some including estimates of nutrient and contaminant transfer. Many of these models have a slope term as a control over particle transfer, with increased transfer associated with increased slopes. This is based on data collected over a wide range of slopes and using relatively small soil flumes and physical principals, i.e. the role of gravity in splash transport and flow. This study uses laboratory rainfall simulation on a large soil flume to investigate interrill soil erosion of a silt loam under a rainfall intensity of 47 mm h(-1) on 3%, 6% and 9% slopes, which are representative of agricultural land in much of northwest Europe. The results show: (1) wide variation in runoff and sediment concentration data from replicate experiments, which indicates the complexities in interrill soil erosion processes; and (2) that at low slopes processes related to surface area connectivity, soil saturation, flow patterns and water depth may dominant over those related to gravity. Consequently, this questions the use of risk assessments and soil erosion models with a dominant slope term when assessing soil erosion from agricultural land at low slopes. Copyright (C) 2010 John Wiley & Sons, Ltd.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{Wilson2010,
title = {Recovery of water tables in Welsh blanket bog after drain blocking: Discharge rates, time scales and the influence of local conditions.},
author = {Lorraine Wilson and
Jared Wilson and
Joseph Holden and
Ian Johnstone and
Alona Armstrong and
Michael Morris},
doi = {10.1016/j.jhydrol.2010.07.042},
year = {2010},
date = {2010-09-24},
journal = {Journal of Hydrology},
volume = {391},
number = {3-4},
pages = {377-386},
abstract = {Peatland practitioners and scientists have increasingly recognised the damage resulting from various management methods, and the need to restore peatlands to achieve several potential benefits. Many of the hoped-for benefits of peatland restoration, such as Carbon storage, biodiversity conservation and water quality improvements, are thought to depend on a reinstatement of high water tables that had been reduced by drainage. Despite the current emphasis on restoring drained peatlands, many of the predicted responses to restoration are still not adequately proven and the mechanisms behind them still uncertain. This study reports on water table and discharge responses to drain blocking restoration of a degraded Welsh upland blanket bog. Restoration work and monitoring were designed to permit a novel catchment scale control-intervention experimental design. An information theoretic approach to examining the data provided evidence of increases in water retention and water tables within the bog after restoration. But the study also demonstrated the importance of small and large scale topography in determining the degree of these responses. The increases in water storage after restoration produced lower discharge rates observable at the level of both drains and hill streams; as well as greater water table stability, reduction in peak flows and increases in water residency after rainfall. Crucially, this study showed strong catchment scale differences in response, and a very gradual recovery of water tables, both of which highlight the need for more studies to be carried out at the landscape scale and over longer time periods. (c) 2010 Elsevier B.V. All rights reserved.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{Hend2010,
title = {Applying close range digital photogrammetry in soil erosion studies},
author = {B. C. Peter Heng and
Jim H. Chandler and
Alona Armstrong},
doi = {10.1111/j.1477-9730.2010.00584.x},
year = {2010},
date = {2010-09-01},
journal = {The Photogrammetric Record},
volume = {25},
number = {131},
pages = {240-265},
abstract = {Soil erosion due to rainfall and overland flow is a significant environmental problem. Studying the phenomenon requires accurate high-resolution measurements of soil surface topography and morphology. Close range digital photogrammetry with an oblique convergent configuration is proposed in this paper as a useful technique for such measurements, in the context of a flume-scale experimental study. The precision of the technique is assessed by comparing triangulation solutions and the resulting DEMs with varying tie point distributions and control point measurements, as well as by comparing DEMs extracted from different images of the same surface. Independent measurements were acquired using a terrestrial laser scanner for comparison with a DEM derived from photogrammetry. The results point to the need for a stronger geometric configuration to improve precision. They also suggest that the camera lens models were not fully adequate for the large object depths in this study. Nevertheless, the photogrammetric output can provide useful topographical information for soil erosion studies, provided limitations of the technique are duly considered.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{Armstrong2010-1,
title = {The impact of peatland drain-blocking on dissolved organic carbon loss and discolouration of water : results from a national survey.},
author = {Alona Armstrong and
Joseph Holden and
Paul Kay and
Brian Francis and
Miles Foulger and
Sarah Gledhill and
Adrian McDonald and
Andrew Walker},
doi = {10.1016/j.jhydrol.2009.11.031},
year = {2010},
date = {2010-02-05},
journal = {Journal of Hydrology},
volume = {381},
number = {1-2},
pages = {112-120},
abstract = {Peatlands are important terrestrial carbon stores but their environmental degradation has led to concerns of increased carbon loss. Many peatlands have been drained using open ditches and this practice has been associated with enhanced dissolved organic carbon loss and water discolouration. Recent peatland restoration schemes have therefore included the blocking of peatland drains as a strategy for environmental improvement. However, it is not clear whether drain-blocking consistently reduces dissolved organic carbon loads and water discolouration because many peats undergo significant physical and chemical change when they are disturbed. Previous studies investigating the impact of drain-blocking on water colour and dissolved organic carbon have been restricted to a limited spatial and temporal research framework. This study combines an extensive UK-wide survey of blocked and unblocked drains across 32 study sites and intensive monitoring of a peat drain system that has been blocked for 7 years. Dissolved organic carbon concentrations and water discolouration were significantly lower in blocked drains: the mean dissolved organic carbon concentration of water sampled from blocked drains was 28% less than that sampled from unblocked drains. However, this pattern was not consistent at all sites. At the intensive monitoring site no significant differences could be observed in total dissolved organic carbon flux from the fully instrumented blocked and unblocked drains: the blocked drain exported 31,592 kg km2 yr1 and the unblocked drain 30,123 kg km2 yr1. Results from bi-weekly grab samples from other drains at the intensively monitored site, however, did conform to the general national pattern of lower dissolved organic carbon and discolouration in blocked drains. The results demonstrate that drain-blocking can be an effective management strategy for reducing DOC loss and water discolouration in disturbed peat catchments. The caveat remains, however, that there will be a number of sites where no significant change will occur.
},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{Armstrong2009-2,
title = {Drain-blocking techniques on blanket peat : a framework for best practice.},
author = {Alona Armstrong and
Joseph Holden and
Paul Kay and
Miles Foulger and
Sarah Gledhill and
Adrian McDonald and
Andrew Walker},
doi = {10.1016/j.jenvman.2009.06.003},
year = {2009},
date = {2009-08-01},
journal = {Journal of Environmental Management},
volume = {90},
number = {11},
pages = {3512-3519},
abstract = {Abstract In recent years there has been a dramatic increase in artificial drain-blocking in world peatlands. The UK blanket peatlands have been severely drained over the past few decades but now drains are being blocked in an attempt to improve peatland environments. The drain-blocking has been a disparate process with limited knowledge transfer between organisations and within organisations operating in different geographic areas. Consequently, there has been no compilation of techniques used and their effectiveness. During this study thirty-two drain-blocked sites were surveyed and all the key stakeholders interviewed. A drain-blocking using peat turf was preferred by practitioners and was also the most cost-effective method. Peat turves were successful except on steep slopes, in areas of severe erosion, in very wet or very dry locations, or if the mineral substrate was exposed. A drain-blocking best practice guide is offered by this paper, providing information on the most suitable methods for blocking peatland drains under different circumstances. Additional considerations are provided for practitioners to ensure peatland drain-blocking is as successful as possible.
},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{Armstrong2009,
title = {Pumped rainfall simulators: the impact of rain pulses on sediment concentration and size.},
author = {Alona Armstrong and
John Quinton},
doi = {10.1002/esp.1810},
year = {2009},
date = {2009-07-01},
journal = {Earth Surface Processes and Landforms},
volume = {34},
number = {9},
pages = {1310-1314},
abstract = {Many pumped rainfall simulators used in soil erosion studies use pulsed rain to control the rainfall intensity. We examined the effect of the rain pulsing on sediment concentration and size using three different pulse cycles with the same rainfall intensity. There was considerable variation in sediment concentration through the pulse cycle: the highest concentration was up to four times that of the lowest concentration. Furthermore, the particle size distribution also varied: the peak median particle size was double the lowest median particle size. The magnitude of differences in sediment concentration and particle size were greater the longer the rain was off for and these dynamics will vary with between rainfall simulators and studies. We suggest the impact of the pulsing on sediment is significant and should be investigated prior to experimentation so that sampling periods are designed to avoid bias introduced by fine temporal scale sediment dynamics.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{Kay2009,
title = {A pilot study of the efficacy of residuum lodges for managing sediment delivery to impoundment reservoirs.},
author = {Paul Kay and
Alona Armstrong and
Adrian McDonald and
Dan Parsons and
Jim Best and
Jeff Peakall and
Andrew Walker and
Miles Foulger and
Sarah Clements},
doi = {10.1111/j.1747-6593.2008.00111.x},
year = {2009},
date = {2009-03-01},
journal = {Water and Environment Journal},
volume = {23},
number = {1},
pages = {52-62},
abstract = {Residuum lodges comprise small dams constructed on feeder streams immediately before they enter a reservoir, behind which ponds form, where sediment is deposited. Despite their construction on many impoundment reservoirs (IRE) and catchwaters, little research has previously investigated their efficacy at removing sediments from feeder streams. The current pilot study has, therefore, been carried out at an IRE supplying Halifax, West Yorkshire, UK, where a residuum lodge was recently cleaned out. Sediment concentrations reaching the reservoir were reduced by up to 42% although no certain impacts were noted on the other water quality variables that were measured. Moreover, it was found that the clearance operation did not result in the release of excessive quantities of sediment into the reservoir. It was estimated that the cleared residuum lodge would take 12 years to refill. A survey of other residuum lodges in the Yorkshire region showed there to be considerable differences in their remaining capacities.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{Cox2008,
title = {Fitting concentration and load rating curves with generalized linear models.},
author = {Nicholas J. Cox and
Jeff Warburton and
Alona Armstrong and
Victoria J. Holliday},
doi = {10.1002/esp.1523},
year = {2008},
date = {2008-01-01},
journal = {Earth Surface Processes and Landforms},
volume = {33},
number = {1},
pages = {25-39},
abstract = {Generalized linear models may be used as a systematic and flexible alternative to existing practices in fitting sediment or solute concentration and load rating curves. Through widely available statistical software they offer a one-step solution to the common and awkward problem that a bias correction is needed when estimating total loads. In particular, using a logarithmic link function has an advantage over logarithmic transformation of concentration or load, as generalized linear models return predictions directly on the original measured scale; there is thus no need for back-transformation or subsequent correction factors. Example analyses are given for suspended sediment concentration for an upland stream in the Northern Pennines and for phosphorus load for the Illinois River. General criteria for choosing models and good practice in the use of figures of model merit and of residual plots are also discussed in detail.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{Worrall2007-3,
title = {Predicting the future carbon budget of an upland peat catchment.},
author = {Fred Worrall and
Tim Burt and
John Adamson and
Mark Reed and
Jeff Warburton and
Alona Armstrong and
Martin Evans},
doi = {10.1007/s10584-007-9300-1},
year = {2007},
date = {2007-11-00},
journal = {Climatic Change},
volume = {85},
number = {1-2},
pages = {139-158},
abstract = {Using data from a single upland peat catchment (North Pennines, UK), this study combines descriptions of the uptake of carbon by primary productivity and input from both wet and dry deposition with descriptions of carbon release pathways: soil CO2 respiration, CH4 flux, particulate organic carbon (POC), dissolved organic carbon (DOC), and excess dissolved CO2. Each pathway is projected 10 years into the future based upon extrapolated changes in rainfall and temperature. The study shows that the catchment is presently a net source of carbon and that over a period of 10 years the catchment goes from a net source of 11.2 to 20.9 gC/m2/year. The probability that the catchment is a net sink of carbon decreases from 35 to 26% over the study period, i.e. upland peats are predicted to become an increasing source of carbon. With respect to carbon gases (CO2 + CH4), the catchment remains a net sink but this decreases from 15.9 to 11.2 gC/m2/year, given current trends the catchment will become a net source of carbon gases by 2034. For most pathways the predicted increases or decreases are in line with increasing temperature predicted for the area, but DOC flux shows a larger percentage increase because of additional production caused by the increased frequency of severe droughts within the catchment. If this result is extended across the UK uplands, peats would be a net source of between 0.26 and 0.45 Mt C/year, but with respect to carbon gases alone the catchment is net sink of between 0.35 and 0.23 Mt C/year.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{Worral2007-2,
title = {The effects of burning and sheep-grazing on water table depth and soil water quality in a upland peat.},
author = {Fred Worrall and
Alona Armstrong and
John Adamson},
doi = {10.1016/j.jhydrol.2006.12.025},
year = {2007},
date = {2007-06-10},
journal = {Journal of Hydrology},
volume = {339},
number = {1-2},
pages = {1-14},
abstract = {Rotational burning of heather to improve grazing and grouse breeding is a common management practice for upland catchments in the UK. However, the effects of such practices on hydrology and water quality are not well understood because the timescale of burning rotation is typically between 7 and 20 years thus requiring long-term experiments in order to resolve the effects. Furthermore, land management, such as changes in burning or grazing practices, has been proposed as a possible strategy for the remediation of the widespread increases in dissolved organic carbon (DOC) observed across the northern hemisphere. This study is based on a long-term experiment on the effect of different rotational burning cycles and grazing intensities on upland vegetation and aims to understand the effects of these management strategies on hydrology and water quality. The main outcomes are: (i) The depth to water table in the soil showed significant differences between different burning rotations and grazing intensities. Depth to water table was greatest on plots where burning did not occur or for longer burning cycles where livestock had been excluded. (ii) The pH and conductivity of sampled soil water showed no significant difference between grazing treatments, with the presence of burning being the most important factor (frequency of the burning cycle was not important). (iii) The DOC content showed no significant difference between grazing treatments but showed a significant decrease with the presence of burning, though no direct relationship with the depth to water table could be found. (iv) Burn management explains only a small proportion of the variance in the composition of the DOC, rather the variation is dominated by the differences between days of sampling and seasonal variation. Therefore, this study suggests that land management controls hydrology and water quality through controlling the development of vegetation.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{Worrall2007,
title = {Short-term impact of peat drain-blocking on water colour, dissolved organic carbon concentration, and water table depth.},
author = {Fred Worrall and Alona Armstrong and Joseph Holden},
doi = {10.1016/j.jhydrol.2007.01.046},
year = {2007},
date = {2007-04-30},
journal = {Journal of Hydrology},
volume = {337},
number = {3-4},
pages = {315-325},
abstract = {Water discolouration is a major management problem for UK water companies as a proportion of the supply relies on runoff from peat-covered catchments. Many peats have been drained using surface ditches but this has been shown to lead to more severe water discolouration. Drain-blocking is now actively encouraged in UK peatlands to promote peatland habitats and water companies are considering funding drain-blocking if water colour benefits can be demonstrated. However, there is concern that rewetting of the peat may lead to a sudden flush of water colour from the peat causing problems for water treatment works downstream. This study tested different drain-blocking techniques in an upland peat catchment and evaluated the impact of drain-blocking on water colour production immediately after drain-blocking. The study started sampling prior to the blocking of the drains and continued for 10 months afterwards. It was shown that drain-blocking significantly increased water tables in the vicinity of the drains. Drain-blocking approximately doubled water colour within blocked drains, a difference that was sustained across the entire study period. Whenever runoff occurred from a blocked drain it was always more discoloured than prior to blocking. However, during the 10 months following drain-blocking no catchment scale change in river water colour could be determined. No drain-blocking technique was demonstrably better or worse than any other with respect to water colour and percentage of time for which there was flow in the drain. Therefore, if more drain-blocking is undertaken then the most economical methods, using peat turves, should be adopted.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}