Most research applying spectral sensors has focused on soil attributes quantification, with strong statistics and hundreds of data. Nevertheless, the explanation of the fundamental relationship between several spectral ranges and specific soil processes remains unclear. Soil sensing can be performed in many spectral ranges, however, the focus is usually on a specific one, which limits the knowledge of the phenomenon. Thus, this work investigated the synergistic performance of several spectral ranges (Gamma-ray; X-ray fluorescence, XRF; visible, Vis; near infrared, NIR; shortwave infrared, SWIR; and mid-infrared, MIR) on the weathering process of soils developed from magmatic material. Two soil profiles from Southeast Brazil (São Paulo state) were analyzed, assessing their chemical, physical and mineralogical data. The same profiles were analyzed by the indicated spectral ranges, which were related to mineralogy, weathering indices and mass balance (MB). The elements provided by Gamma-ray were related to the soil mineralogy and weathering degree of horizons. The XRF data enabled the calculation of MB and weathering indices, which were similar to those calculated by the traditional analysis. The spectra of the Vis-NIR-SWIR-MIR region presented alterations in their behavior related to the weathering degree of horizons. This synergic approach separated soil horizons by weathering degree more efficiently than a single spectral region. Single spectral measurements identified several elements and indices, which explained the weathering process. These results support further understanding of large datasets and their validation in statistical modeling.

Soil erosion is widely acknowledged as a global problem but attempts to measure and estimate its significance are frustrated by our inability to develop reliable, cheap and easy methods of assessment. The limitations of qualitative methods such as GLASOD, errors and inaccuracies inherent in modelling based on small-scale plot experiments, and problems with 137 Cs approaches, mean that alternative strategies are required. For runoff-related erosion on arable land we propose the use of a well-tried estimation technique: volumetric measurement of rills, gullies and fans. Amounts of wash and interrill erosion can also be estimated. This approach allows for the estimation of erosion rates at the field scale, rather than relying on extrapolations from plot-based data. Measurements are based on sampling the population of rills and gullies and can be adapted to the aims of the project for ‘broad-brush’ or detailed data. Monitoring of large areas to produce regional assessments of erosion risk is frequently required and volumetric estimates provide these data. Thus predictions of the extent, frequency and amounts of erosion can be made and the vulnerability of particular crops becomes clear.

Off‐site impacts of soil erosion are of greater social and economic concern in Western Europe than on‐site impacts. They fall into two related categories: muddy flooding of properties and ecological impacts on watercourses because of excessive sedimentation and associated pollutants. Critical to these impacts is the connectedness of the runoff and sediment system between agricultural fields and the river system. We argue that well‐connected systems causing off‐site damage are not necessarily related to areas of high erosion rates; emphasis should therefore be on the way in which connections occur. In temperate, arable systems, important elements of connectivity are anthropogenic in origin: roads, tracks, sunken lanes, field drains, ditches, culverts and permeable field boundaries. Mapping these features allows us to understand how they affect runoff and modify its impacts, to design appropriate mitigation measures and to better validate model predictions. Published maps (digital and paper) do not, by themselves, give sufficient information. Field mapping and observation, aided by remote sensing, are also necessary.

Dobson and Brewer spectrophotometers are the primary, standard instruments for ground-based ozone measurements under the World Meteorological Organization's (WMO) Global Atmosphere Watch program. The accuracy of the data retrieval for both instruments depends on a knowledge of the ozone absorption coefficients and some assumptions underlying the data analysis. Instrumental stray light causes nonlinearity in the response of both the Brewer and Dobson to ozone at large ozone slant paths. In addition, it affects the effective ozone absorption coefficients and extraterrestrial constants that are both instrument-dependent. This effect has not been taken into account in the calculation of ozone absorption coefficients that are currently recommended by WMO for the Dobson network. The ozone absorption coefficients are calculated for each Brewer instrument individually, but in the current procedure the effect of stray light is not considered. This study documents the error caused by the effect of stray light in the Brewer and Dobson total ozone measurements using a physical model for each instrument. For the first time, new ozone absorption coefficients are calculated for the Brewer and Dobson instruments, taking into account the stray light effect. The analyses show that the differences detected between the total ozone amounts deduced from Dobson AD and CD pair wavelengths are related to the level of stray light within the instrument. The discrepancy introduced by the assumption of a fixed height for the ozone layer for ozone measurements at high latitude sites is also evaluated. The ozone data collected by two Dobson instruments during the period of December 2008 to December 2014 are compared with ozone data from a collocated double monochromator Brewer spectrophotometer (Mark III). The results illustrate the dependence of Dobson AD and CD pair measurements on stray light.

River discharge and nutrient measurements are subject to aleatory and epistemic uncertainties. In this study, we present a novel method for estimating these uncertainties in colocated discharge and phosphorus (P) measurements. The "voting point"-based method constrains the derived stage-discharge rating curve both on the fit to available gaugings and to the catchment water balance. This helps reduce the uncertainty beyond the range of available gaugings and during out of bank situations. In the example presented here, for the top 5% of flows, uncertainties are shown to be 139% using a traditional power law fit, compared with 40% when using our updated "voting point" method. Furthermore, the method is extended to in situ and lab analysed nutrient concentration data pairings, with lower uncertainties (81%) shown for high concentrations (top 5%) than when a traditional regression is applied (102%). Overall, for both discharge and nutrient data, the method presented goes some way to accounting for epistemic uncertainties associated with nonstationary physical characteristics of the monitoring site.

There is a need to model and predict the transfer of phosphorus (P) from land to water, but this is challenging because of the large number of complex physical and biogeochemical processes involved. This study presents, for the first time, a 'limits of acceptability' approach of the Generalized Likelihood Uncertainty Estimation (GLUE) framework to the Soil and Water Assessment Tool (SWAT), in an application to a water quality problem in the Newby Beck catchment (12.5 km(2)), Cumbria, United Kingdom (UK). Using high frequency outlet data (discharge and P), individual evaluation criteria (limits of acceptability) were assigned to observed discharge and P loads for all evaluation time steps, identifying where the model was performing well/poorly and to infer which processes required improvement in the model structure. Initial limits of acceptability were required to be relaxed by a substantial amount (by factors of between 5.3 and 6.7 on a normalized scale depending on the evaluation criteria used) in order to gain a set of behavioral simulations (1001 and 1016, respectively out of 5,000,000). Of the 39 model parameters tested, the representation of subsurface processes and associated parameters, were consistently shown as critical to the model not meeting the evaluation criteria, irrespective of the chosen evaluation metric. It is therefore concluded that SWAT is not an appropriate model to guide P management in this catchment. This approach highlights the importance of high frequency monitoring data for setting robust model evaluation criteria. It also raises the question as to whether it is possible to have sufficient input data available to drive such models so that we can have confidence in their predictions and their ability to inform catchment management strategies to tackle the problem of diffuse pollution from agriculture. (C) 2018 The Authors. Published by Elsevier B.V.

Climate projections for the future indicate that the United Kingdom will experience hotter, drier summers and warmer, wetter winters, bringing longer dry periods followed by rewetting. This will result in changes in phosphorus (P) mobilization patterns that will influence the transfer of P from land to water. We tested the hypothesis that changes in the future patterns of drying-rewetting will affect the amount of soluble reactive phosphorus (SRP) solubilized from soil. Estimations of dry period characteristics (duration and temperature) under current and predicted climate were determined using data from the UK Climate Projections (UKCP09) Weather Generator tool. Three soils (sieved <2 mm), collected from two regions of the United Kingdom with different soils and farm systems, were dried at 25°C for periods of 0, 2, 4, 5, 6, 8, 10, 15, 20, 25, 30, 60, and 90 d, then subsequently rewetted (50 mL over 2 h). The solubilized leachate was collected and analyzed for SRP. In the 2050s, warm period temperature extremes >25°C are predicted in some places and dry periods of 30 to 90 d extremes are predicted. Combining the frequency of projected dry periods with the SRP concentration in leachate suggests that this may result overall in increased mobilization of P; however, critical breakpoints of 6.9 to 14.5 d dry occur wherein up to 28% more SRP can be solubilized following a rapid rewetting event. The precise cause of this increase could not be identified and warrants further investigation as the process is not currently included in P transfer models.

Excess nutrients in surface waters, such as phosphorus (P) from agriculture, result in poor water quality, with adverse effects on ecological health and costs for remediation. However, understanding and prediction of P transfers in catchments have been limited by inadequate data and over-parameterised models with high uncertainty. We show that, with high temporal resolution data, we are able to identify simple dynamic models that capture the P load dynamics in three contrasting agricultural catchments in the UK. For a flashy catchment, a linear, second-order (two pathways) model for discharge gave high simulation efficiencies for short-term storm sequences and was useful in highlighting uncertainties in out-of-bank flows. A model with non-linear rainfall input was appropriate for predicting seasonal or annual cumulative P loads where antecedent conditions affected the catchment response. For second-order models, the time constant for the fast pathway varied between 2 and 15 h for all three catchments and for both discharge and P, confirming that high temporal resolution data are necessary to capture the dynamic responses in small catchments (10–50 km2). The models led to a better understanding of the dominant nutrient transfer modes, which will be helpful in determining phosphorus transfers following changes in precipitation patterns in the future.

Abstract. Excess nutrients in surface waters, such as phosphorus (P) from agriculture, result in poor water quality, with adverse effects on ecological health and costs for remediation. However, understanding and prediction of P transfers in catchments have been limited by inadequate data and over-parameterised models with high uncertainty. We show that, with high temporal resolution data, we are able to identify simple dynamic models that capture the P load dynamics in three contrasting agricultural catchments in the UK. For a flashy catchment, a linear, second-order (two pathways) model for discharge gave high simulation efficiencies for short-term storm sequences and was useful in highlighting uncertainties in out-of-bank flows. A model with non-linear rainfall input was appropriate for predicting seasonal or annual cumulative P loads where antecedent conditions affected the catchment response. For second-order models, the time constant for the fast pathway varied between 2 and 15 hours for all three catchments and for both discharge and P, confirming that high temporal resolution (hourly) data are necessary to capture the dynamic responses in small catchments (10–50 km2). The models led to a better understanding of the dominant nutrient transfer modes, which will, in-turn, help in planning appropriate pollution mitigation measures.

Soils deliver a range of ecosystem services and underpin conventional global food production which must increase to feed the projected growth in human population. Although soil erosion by water and subsequent sediment delivery to rivers are natural processes, anthropogenic pressures, including modern farming practices and management, have accelerated soil erosion rates on both arable and grassland. A range of approaches can be used to assess and document soil erosion rates and, in the case of the UK, these mainly comprise the 137Cs-based approach, conventional surveys using volumetric measurements, integration of information on suspended sediment flux, fine sediment source apportionment and landscape sediment retention and traditional bounded hydrological monitoring at edge-of-field using experimental platforms. We compare the erosion rates for arable and grassland in lowland England assessed by these different techniques. Rates assessed by volumetric measurements are similar to those generated by integrating information on suspended sediment flux, sources and landscape retention, but are much less than those estimated by the 137Cs-based approach; of the order of one magnitude less for arable land. The 137Cs approach assumes an initial distribution of 137Cs uniformly spread across the landscape and relates the sampled distribution to erosion, but other (transport) processes are also involved and their representation in the calibration procedures remains problematic. We suggest that the 137Cs technique needs to be validated more rigorously and conversion models re-calibrated. As things stand, rates of erosion based on the distribution of 137Cs may well overstate the severity of the problem in lowland Britain and, therefore, are not a reliable indicator of water erosion rates.

Monitoring of runoff and erosion in farmers' fields and their impacts gives a better understanding of erosion. However, it is rare that monitoring at frequent intervals is done over a prolonged period. A part of the upper Wissey catchment in central Norfolk, eastern England was monitored for 10years to assess the extent and frequency of erosion and runoff, their causes and impacts. Surface wash occurred more widely and more frequently than expected. Runoff and erosion took place a number of times in a year in a range of autumn- and spring-sown crops, and occurred dominantly down tractor wheelings or ruts left after harvesting potatoes or sugar beet under wet conditions. Over 10years erosion affected about half the 105 fields monitored, often more than once. Erosion was more extensive in autumn-sown cereal fields, but often more severe and with greater off-field effects, for example muddy flooding of roads from spring-sown late harvested crops such as potatoes and sugar beet. Runoff from outdoor pig fields also flooded roads and houses. This study confirms other studies of the extent, frequency and severity of erosion in Britain, that rill erosion does not occur in every field in the landscape, that in the main, fields do not erode frequently and rates of erosion are generally small. Runoff and erosion within a field took place more frequently than had been suspected. Compaction and destruction of topsoil structure by machinery especially at harvest, or by outdoor pigs, is important in initiating runoff. Rates of erosion were generally very low and will not affect soil productivity adversely over the short-term. However, flooding of roads and property, and especially pollution of water courses by sediment, nutrients and pesticides are important off-field impacts and are the primary reason, over the short-term, for mitigating runoff and erosion. Monitoring such as this sheds light on the problems of modelling to predict risk of erosion based on erosion rates. Copyright (c) 2017 John Wiley & Sons, Ltd.

Phosphorus losses from land to water will be impacted by climate change and land management for food production, with detrimental impacts on aquatic ecosystems. Here we use a unique combination of methods to evaluate the impact of projected climate change on future phosphorus transfers, and to assess what scale of agricultural change would be needed to mitigate these transfers. We combine novel high-frequency phosphorus flux data from three representative catchments across the UK, a new high-spatial resolution climate model, uncertainty estimates from an ensemble of future climate simulations, two phosphorus transfer models of contrasting complexity and a simplified representation of the potential intensification of agriculture based on expert elicitation from land managers. We show that the effect of climate change on average winter phosphorus loads (predicted increase up to 30% by 2050s) will be limited only by large-scale agricultural changes (e.g., 20–80% reduction in phosphorus inputs).

We hypothesise that climate change, together with intensive agricultural systems, will increase the transfer of pollutants from land to water and impact on stream health. This study builds, for the first time, an integrated assessment of nutrient transfers, bringing together a) high-frequency data from the outlets of two surface water-dominated, headwater (~10km(2)) agricultural catchments, b) event-by-event analysis of nutrient transfers, c) concentration duration curves for comparison with EU Water Framework Directive water quality targets, d) event analysis of location-specific, sub-daily rainfall projections (UKCP, 2009), and e) a linear model relating storm rainfall to phosphorus load. These components, in combination, bring innovation and new insight into the estimation of future phosphorus transfers, which was not available from individual components. The data demonstrated two features of particular concern for climate change impacts. Firstly, the bulk of the suspended sediment and total phosphorus (TP) load (greater than 90% and 80% respectively) was transferred during the highest discharge events. The linear model of rainfall-driven TP transfers estimated that, with the projected increase in winter rainfall (+8% to +17% in the catchments by 2050s), annual event loads might increase by around 9% on average, if agricultural practices remain unchanged. Secondly, events following dry periods of several weeks, particularly in summer, were responsible for high concentrations of phosphorus, but relatively low loads. The high concentrations, associated with low flow, could become more frequent or last longer in the future, with a corresponding increase in the length of time that threshold concentrations (e.g. for water quality status) are exceeded. The results suggest that in order to build resilience in stream health and help mitigate potential increases in diffuse agricultural water pollution due to climate change, land management practices should target controllable risk factors, such as soil nutrient status, soil condition and crop cover.

We respond to an article by Panagos et al.-'The new assessment of soil loss by water erosion in Europe' in Environ. Sci. Policy, 2015, 54, 438-447. It is aimed at helping policy makers make better decisions. The assessment uses a Geographical Information Systems approach based on the Revised Universal Soil Loss Equation. RUSLE is based on data gained from plot experiments. The authors assume RUSLE is the only way to assess erosion and ignore critiques of erosion models and other ways of assessing erosion. A different way of assessing water erosion, based on collecting information on extent, frequency and rates, mainly from farmers' fields but also grazed uplands, has been carried out over recent decades in Britain. The two ways of assessing erosion, one largely theoretical, the other based on reality, evolved in response to particular situations. However, they should relate well to each other. We show that the model is inappropriate to assess soil loss by water erosion in Britain, not only for agricultural land but also for uncultivated land. Predicted high rates of erosion do not relate well to where erosion actually occurs and are too high, and the model takes no account of the spatial extent of erosion on the ground. In other words, the model does not reflect reality. Policy decisions should not be taken based on such a model. Erosion must be assessed in a better way with a large field-based element. (C) 2016 Elsevier Ltd. All rights reserved.

Soil erosion on arable land in lowland Britain has been the subject of field‐based surveys, which have assessed the volumes or masses of soil transported in channels across farmers’ fields. These surveys provide a unique database on the extent, frequency and rates of soil loss by water. This study synthesizes the key findings from those surveys and underscores the implications for soil erosion modelling. Rill erosion occurs in a small number of fields (consistently <10%). Over ~5 yr, a considerable proportion of the farmed landscape will suffer from rill erosion, but mostly in fields that erode only once. Mean erosion rates for lowland arable landscapes are much less than mean erosion rates for individual eroded fields within that landscape. These observations pose important challenges for modelling. Rainfall and cropping vary from year to year so that risk of wash or rill erosion in the same field also varies. Due to the infrequent occurrence of rill erosion, loss rates of eroding fields cannot be spatially extrapolated across the landscape, except in the case of wash erosion which takes place a number of times in almost all fields every year. A consistent pattern of increasing wash erosion, in terms of spatial extent, is emerging in lowland Britain. Resulting losses of fine silt and clay‐sized particles are small in amount and possibly insignificant in terms of loss of soil as a resource, but have significant implications for contaminant concentrations and pollution of water courses.

We respond to the article by Panagos et al. in Environmental Science & Policy 2016, 59, 53–57. We first outline the history of assessing water erosion of cultivated land in Britain, to place in context why a model approach has not been considered the best way to assess erosion in Britain. Since 1982 a field- based approach has been consistently chosen. We then consider three particular points of contention between ourselves and Panagos et al.—1) the importance of wash erosion, 2) the cost of carrying out a field-based assessment of erosion, and 3) that the Revised Universal Soil Loss Equation should be the harmonized method to assess soil loss. Last, we respond to individual points made by Panagos et al. before drawing some conclusions. One conclusion is that a more harmonious way of assessing erosion was put forward in 2004 by Gobin et al. combining both field-based and model assessments, but unfortunately that route was not taken by researchers at the Joint Research Centre.

Mass transport, such as movement of phosphorus in soils and solutes in rivers, is a natural phenomenon and its study plays an important role in science and engineering. It is found that there are numerous practical diffusion phenomena that do not obey the classical advection-diffusion equation (ADE). Such diffusion is called abnormal or superdiffusion, and it is well described using a fractional advection-diffusion equation (FADE). The FADE finds a wide range of applications in various areas with great potential for studying complex mass transport in real hydrological systems. However, solution to the FADE is difficult, and the existing numerical methods are complicated and inefficient. In this study, a fresh lattice Boltzmann method is developed for solving the fractional advection-diffusion equation (LabFADE). The FADE is transformed into an equation similar to an advection-diffusion equation and solved using the lattice Boltzmann method. The LabFADE has all the advantages of the conventional lattice Boltzmann method and avoids a complex solution procedure, unlike other existing numerical methods. The method has been validated through simulations of several benchmark tests: a point-source diffusion, a boundary-value problem of steady diffusion, and an initial-boundary-value problem of unsteady diffusion with the coexistence of source and sink terms. In addition, by including the effects of the skewness β, the fractional order α, and the single relaxation time τ, the accuracy and convergence of the method have been assessed. The numerical predictions are compared with the analytical solutions, and they indicate that the method is second-order accurate. The method presented will allow the FADE to be more widely applied to complex mass transport problems in science and engineering.

This article analyzes the decision-making processes used by government agencies when trying to decide whether to approve or reject projects that impact the environment. This article examines some of the real-life inputs into the decision, as well as the influences on the decision maker. For example, some academics suggest that decision makers are more influenced by the environmental impact assessment process itself than by the conclusions of the assessment. Three case studies are presented. I provide an overview of each project and the various influences on the respective decision maker. I demonstrate that decision makers tend to elevate social, cultural, and political concerns over the natural environment. I also demonstrate that each decision maker was influenced by a particular social, cultural, or political aspect unique to each situation. I recommend further research in the expanding use of analytical tools and models in environmental decision making. These tools may encourage the decision maker to give more consideration to the results of the environmental impact assessment versus other external influences.

Soil erosion is a key issue in Europe, and strategies to protect soil need to be developed. Hence, eroding soils or those at risk of erosion need to be identified. Much model-derived information on rates of erosion and on erosion risk of cultivated land may be of dubious value, and thus, there is need for other ways to assess erosion. Field-based assessment is one approach for assessing and monitoring erosion and gives information that can be used at a variety of scales. In this review paper, the continuing use of models that predict potential erosion is questioned, and it is argued that there is a need for more field-based assessment and monitoring of water erosion with monitoring at frequent intervals. Such monitoring allows the magnitude of the erosion problem to be assessed properly, and thus, the physical, social and economic factors that drive erosion can be better analysed and addressed. Field-based erosion monitoring should be undertaken in all global environments, and then the results can be used to validate those from models of potential erosion.

Reconnaissance surveys were made to assess sources of diffuse pollution in the Wissey, Blyth, Little Ouse and Wensum catchments in East Anglia, eastern England. Water-eroded fields and the state of watercourses, roads and tracks were noted and photographed along traverses made across the catchments. Volumes of soil moved were estimated. River nutrient concentrations and turbidity were examined. Nutrient enrichment of watercourses is mostly explained by effluent leaving small Sewage Treatment Works. Sediment in watercourses can come not only from eroded fields but also from roads and tracks and erosion of the channels themselves. Farmers and land managers are not the only ones who must be targeted to curtail enrichment and sedimentation of watercourses. Policy makers need to take such findings into account if water quality in East Anglia is to be improved. Exploratory surveys can indicate sources of pollutants and be a basis for further investigation or ameliorative action.