399 research outputs found

    Use of rare earth oxides as tracers to identify sediment source areas for agricultural hillslopes

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    Understanding sediment sources is essential to enable more effective targeting of in-field mitigation approaches to reduce diffuse pollution from agricultural land. In this paper we report on the application of rare earth element oxides to arable soils at hillslope scale in order to determine sediment source areas and their relative importance, using a non-intrusive method of surface spraying. Runoff, sediments and rare earth elements lost from four arable hillslope lengths at a site in the UK with clay soils were monitored from three rainfall events after tracer application. Measured erosion rates were low, reflecting the typical event conditions occurring at the site, and less than 1% of the applied REO tracers were recovered, which is consistent with the results of comparable studies. Tracer recovery at the base of the hillslope was able to indicate the relative importance of different hillslope sediment source areas, which were found to be consistent between events. The principal source of eroded sediments was the upslope area, implying that the wheel tracks were principally conduits for sediment transport, and not highly active sites of erosion. Mitigation treatments for sediment losses from arable hillslopes should therefore focus on methodologies for trapping mobile sediments within wheel track areas through increasing surface roughness or reducing the connectivity of sediment transport processes

    Sensitivity analysis of EUROSEM using Monte Carlo simulation II::the effect of rills and rock fragments

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    A sensitivity analysis of the surface and catchment characteristics in the European soil erosion model (EUROSEM) was carried out with special emphasis on rills and rock fragment cover. The analysis focused on the use of Monte Carlo simulation but was supplemented by a simple sensitivity analysis where input variables were increased and decreased by 10%. The study showed that rock fragments have a significant effect upon the static output parameters of total runoff, peak flow rate, total soil loss and peak sediment discharge, but with a high coefficient of variation. The same applied to the average hydrographs and sedigraphs although the peak of the graphs was associated with a low coefficient of variation. On average, however, the model was able to simulate the effect of rock fragment cover quite well. The sensitivity analysis through the Monte Carlo simulation showed that the model is particularly sensitive to changes in parameters describing rills and the length of the plane when no rock fragments are simulated but that the model also is sensitive to changes in the fraction of non-erodible material and interrill slope when rock fragments were embedded in the topsoil. For rock fragments resting on the surface, changes in parameter values did not affect model output significantly. The simple sensitivity analysis supported the findings from the Monte Carlo simulation and illustrates the importance when choosing input parameters to describe both rills and rock fragment cover when modelling with EUROSEM

    Mitigating the Transfer of Sediment and Pollutants from Soils to Water

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    Determining The Cost Effectiveness Of Solutions To Diffuse Pollution: Developing A Model To Assess In-Field Mitigation Options for Phosphorous and Sediment Loss

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    The European Union Water Framework Directive requires governments to set water quality objectives based on good ecological status. This includes specific requirements to control diffuse pollution. Diffuse phosphorous (P) pollution plays a pivotal role in influencing water quality with losses of P associated with soil particles often linked to soil erosion. The Mitigation Options for Phosphorus and Sediment (MOPS) project, using three case study sites, is investigating the cost effectiveness of specific control measures in terms of mitigating sediment and P loss from combinable crops. The analysis is conducted at the farm level using a simple spreadsheet model. Further development of the model will allow the results to be extrapolated to generic regional farm typologies. Results from the initial farm level analysis suggest that some mitigation options may not be cost effective in reducing diffuse pollution, however, that other options may be very cost effective.Resource /Energy Economics and Policy,

    Using sorbent waste materials to enhance treatment of micro-point source effluents by constructed wetlands

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    Sorbent materials are widely used in environmental settings as a means of = enhancing pollution remediation. A key area of environmental concern is that of water pollution, including the need to treat micro-point sources of wastewater pollution, such as from caravan sites or visitor centres. Constructed wetlands (CWs) represent one means for effective treatment of wastewater from small wastewater producers, in part because they are believed to be economically viable and environmentally sustainable. Constructed wetlands have the potential to remove a range of pollutants found in wastewater, including nitrogen (N), phosphorus (P), biochemical oxygen demand (BOD) and carbon (C), whilst also reducing the total suspended solids (TSS) concentration in effluents. However, there remain particular challenges for P and N removal from wastewater in CWs, as well as the sometimes limited BOD removal within these treatment systems, particularly for micro-point sources of wastewater. It has been hypothesised that the amendment of CWs with sorbent materials can enhance their potential to treat wastewater, particularly through enhancing the removal of N and P. This paper focuses on data from batch and mesocosm studies that were conducted to identify and assess sorbent materials suitable for use within CWs. The aim in using sorbent material was to enhance the combined removal of phosphate (PO4-P) and ammonium (NH4-N). The key selection criteria for the sorbent materials were that they possess effective PO4-P, NH4-N or combined pollutant removal, come from low cost and sustainable sources, have potential for reuse, for example as a fertiliser or soil conditioner, and show limited potential for re-release of adsorbed nutrients. The sorbent materials selected for testing were alum sludge from water treatment works, ochre derived from minewater treatment, biochar derived from various feedstocks, plasterboard and zeolite. The performance of the individual sorbents was assessed through preliminary desorption studies, isotherm and kinetic adsorption studies, as well as through final desorption studies. Batch studies demonstrated that alum sludge and ochre effectively removed PO4-P from solution (maximum sorption capacity up to 45 mg/g), whilst biochar from both bamboo and rice feedstocks demonstrated effective removal of NH4-N from solution. The potential benefit of using combined reactive media in conjunction with wastewater recirculation to enhance N, P and C treatment was examined using mesocosm studies, and we report initial data from these mesocosm studies

    Comparison of Algorithms and Parameterisations for Infiltration into Organic-Covered Permafrost Soils

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    Infiltration into frozen and unfrozen soils is critical in hydrology, controlling active layer soil water dynamics and influencing runoff. Few Land Surface Models (LSMs) and Hydrological Models (HMs) have been developed, adapted or tested for frozen conditions and permafrost soils. Considering the vast geographical area influenced by freeze/thaw processes and permafrost, and the rapid environmental change observed worldwide in these regions, a need exists to improve models to better represent their hydrology. In this study, various infiltration algorithms and parameterisation methods, which are commonly employed in current LSMs and HMs were tested against detailed measurements at three sites in Canada’s discontinuous permafrost region with organic soil depths ranging from 0.02 to 3 m. Field data from two consecutive years were used to calibrate and evaluate the infiltration algorithms and parameterisations. Important conclusions include: (1) the single most important factor that controls the infiltration at permafrost sites is ground thaw depth, (2) differences among the simulated infiltration by different algorithms and parameterisations were only found when the ground was frozen or during the initial fast thawing stages, but not after ground thaw reaches a critical depth of 15 to 30 cm, (3) despite similarities in simulated total infiltration after ground thaw reaches the critical depth, the choice of algorithm influenced the distribution of water among the soil layers, and (4) the ice impedance factor for hydraulic conductivity, which is commonly used in LSMs and HMs, may not be necessary once the water potential driven frozen soil parameterisation is employed. Results from this work provide guidelines that can be directly implemented in LSMs and HMs to improve their application in organic covered permafrost soils

    A changepoint approach to modelling non-stationary soil moisture dynamics

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    Soil moisture dynamics provide an indicator of soil health that scientists model via soil drydown curves. The typical modeling process requires the soil moisture time series to be manually separated into drydown segments and then exponential decay models are fitted to them independently. Sensor development over recent years means that experiments that were previously conducted over a few field campaigns can now be scaled to months or even years, often at a higher sampling rate. Manual identification of drydown segments is no longer practical. To better meet the challenge of increasing data size, this paper proposes a novel changepoint-based approach to automatically identify structural changes in the soil drying process, and estimate the parameters characterizing the drying processes simultaneously. A simulation study is carried out to assess the performance of the method. The results demonstrate its ability to identify structural changes and retrieve key parameters of interest to soil scientists. The method is applied to hourly soil moisture time series from the NEON data portal to investigate the temporal dynamics of soil moisture drydown. We recover known relationships previously identified manually, alongside delivering new insights into the temporal variability across soil types and locations.Comment: 19 pages for the main manuscript, 6 pages for the supplemental documen
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