bluuebunny/crossref_metadata_2025 huggingface dataset:
An innovative treatment concept for future drinking water production: fluidized ion exchange-ultrafiltration-nanofiltration-granular activated carbon filtration
Authors: Li S. , Heijman S. G. J. , Verberk J. Q. J. C. , van Dijk J. C.
Published: April 2010

Abstract. A new treatment concept for drinking water production from surface water has been investigated on a pilot scale. The treatment concept consists of fluidized ion exchange (FIEX), ultrafiltration (UF), nanofiltration (NF), and granular activated carbon filtration (GAC). The FIEX process removed calcium and other divalent cations; the UF membrane removed particles and micro-organisms; and the NF membrane and GAC removed natural organic matter (NOM) and micro-pollutants. This study focused on the prevention of fouling of the UF and scaling of the NF and investigated the overall removal of micro-pollutants by the treatment concept. The results of the experiments showed that in 14 days of continuous operation at a flux of 65 l/h. m2 the UF performance was stable with the FIEX pre-treated feed water without the aid of a coagulant. The scaling of the NF was also not observed even at 97% recovery. Different micro-pollutants were spiked in the NF feed water and their concentrations in the effluent of NF and GAC were measured. The combination of NF and GAC removed most of the micro-pollutants successfully, except for the very polar substances with a molecular weight lower than 100 Daltons.
Effects of ozonation and temperature on biodegradation of natural organic matter in biological granular activated carbon filters
Authors: van der Aa L. T. J. , Rietveld L. C. , van Dijk J. C.
Published: April 2010

Abstract. Four pilot (biological) granular activated carbon ((B)GAC) filters were operated to quantify the effects of ozonation and water temperature on the biodegradation of natural organic matter (NOM) in (B)GAC filters. Removal of dissolved organic carbon (DOC), assimilable organic carbon (AOC) and oxygen and the production of carbon dioxide were taken as indicators for NOM biodegradation. Ozonation stimulated DOC and AOC removal in the BGAC filters, but had no significant effect on oxygen removal and carbon dioxide production. The temperature had no significant effect on DOC and AOC removal, while oxygen removal and carbon dioxide production increased with increasing temperature. Multivariate linear regression was used to quantify these relations. In summer the ratio between oxygen consumption and DOC removal exceeded the theoretical maximum of 2.5 g O2·g C−1 and the ratio between carbon dioxide production and DOC removal exceeded the theoretical maximum of 3.7 g CO2·g C−1. Bioregeneration of large NOM molecules could explain this excesses and the non-correlation between DOC and AOC removal and oxygen removal and carbon dioxide production. However bioregeneration of large NOM molecules was considered not likely to happen, due to sequestration.
CARINA oxygen data in the Atlantic Ocean
Authors: Stendardo I. , Gruber N. , Körtzinger A.
Published: April 2010

Abstract. In the CARINA (Carbon dioxide in the Atlantic Ocean) project, a new dataset with many previously unpublished hydrographic data from the Atlantic, Arctic and Southern Ocean was assembled and subjected to careful quality control (QC) procedures. Here, we present the dissolved oxygen measurements in the Atlantic region of the dataset and describe in detail the secondary QC procedures that aim to ensure that the data are internally consistent. This is achieved by a cross-over analysis, i.e. the comparison of deep ocean data at places that were sampled by different cruises at different times. Initial adjustments to the individual cruises were then determined by an inverse procedure that computes a set of adjustments that requires the minimum amount of adjustment and at the same time reduces the offsets in an optimal manner. The initial adjustments were then reviewed by the CARINA members, and only those that passed the following two criteria were adopted: (i) the region is not subject to substantial temporal variability, and (ii) the adjustment must be based on at least three stations from each cruise. No adjustment was recommended for cruises that did not fit these criteria. The final CARINA-Oxygen dataset has 103414 oxygen samples from 9491 stations obtained during 98 cruises covering three decades. The sampling density of the oxygen data is particularly good in the North Atlantic north of about 40° N especially after 1987. In contrast, the sample density in the South Atlantic is much lower. Some cruises appear to have poor data quality, and were subsequently omitted from the adjusted dataset. Of the data included in the adjusted dataset, 20% were adjusted with a mean adjustment of 2%. Due to the achieved internal consistency, the resulting product is well suited to produce an improved climatology or to study long-term changes in the oxygen content of the ocean. However, the adjusted dataset is not necessarily better suited than the unadjusted data to address questions that require a high level of accuracy, such as the computation of the saturation state.
Quality control procedures and methods of the CARINA database
Authors: Tanhua T. , van Heuven S. , Key R. M. , Velo A. , Olsen A. , Schirnick C.
Published: April 2010

Abstract. Data on the carbon and carbon relevant hydrographic and hydrochemical parameters from previously not publicly available cruises in the Arctic, Atlantic and Southern Ocean have been retrieved and merged to a new data base: CARINA (CARbon IN the Atlantic). These data have gone through rigorous quality control (QC) procedures to assure the highest possible quality and consistency. All CARINA data were subject to primary QC; a process in which data are studied in order to identify outliers and obvious errors. Additionally, secondary QC was performed for several of the measured parameters in the CARINA data base. Secondary QC is a process in which the data are objectively studied in order to quantify systematic differences in the reported values. This process involved crossover analysis, and as a second step the offsets derived from the crossover analysis were used to calculate corrections of the parameters measured on individual cruises using least square models. Significant biases found in the data have been corrected in the data products, i.e. three merged data files containing measured, calculated and interpolated data for each of the three regions (i.e. Arctic Mediterranean Seas, Atlantic, and Southern Ocean). Here we report on the technical details of the quality control and on tools that have been developed and used during the project, including procedures for crossover analysis and least square models. Furthermore, an interactive website for uploading of results, plots, comments etc. was developed and was of critical importance for the success of the project, this is also described here.
CARINA-Oxygen: a new high-quality oxygen database for the Atlantic Ocean
Authors: Stendardo I. , Gruber N. , Körtzinger A.
Published: April 2010

Abstract. In the CARINA project, a new dataset with many previously unpublished hydrographic data from the Atlantic, Arctic and Southern Ocean was assembled and subjected to careful quality control (QC) procedures. In this paper, we present the dissolved oxygen measurements in the Atlantic region of the database and describe in detail the secondary QC procedures that aim to ensure optimal consistency between different cruises in order to permit studies of long-term change. The secondary QC is based on a cross-over analysis, i.e. the comparison of deep ocean data at places that were sampled by different cruises at different times. Initial adjustments to the individual cruises were then determined by an inverse procedure that computes a set of adjustments that requires the minimum amount of adjustment and at the same time reduces the offsets in an optimal manner. The initial adjustments were then reviewed by the CARINA members, and only those that passed the following two criteria were adopted: (i) the region not subject to substantial temporal variability, and (ii) the adjustment must be based on at least three stations from each cruise. No adjustment was recommended for cruises that did not fit these criteria. The final CARINA-Oxygen database has 113005 oxygen samples from 9535 stations obtained during 98 cruises covering three decades. The sampling density of the oxygen data is particularly good in the North Atlantic north of about 40° N especially after 1987. In contrast, the sample density in the South Atlantic is much lower. Some cruises appear to have poor data quality, and were subsequently omitted from the adjusted data base. Of the data included in the adjusted data base, 20% were adjusted with a mean adjustment of 2%.
CARINA data synthesis project: pH data scale unification and cruise adjustments
Authors: Velo A. , Pérez F. F. , Lin X. , Key R. M. , Tanhua T. , de la Paz M. , van Heuven S. , Jutterström S. , Ríos A. F.
Published: April 2010

Abstract. Data on carbon and carbon-relevant hydrographic and hydrochemical parameters from previously non-publicly available cruise data sets in the Artic Mediterranean Seas (AMS), Atlantic and Southern Ocean have been retrieved and merged to a new database: CARINA (CARbon IN the Atlantic). These data have gone through rigorous quality control (QC) procedures to assure the highest possible quality and consistency. The data for most of the measured parameters in the CARINA database were objectively examined in order to quantify systematic differences in the reported values, i.e. secondary quality control. Systematic biases found in the data have been corrected in the data products, i.e. three merged data files with measured, calculated and interpolated data for each of the three CARINA regions; AMS, Atlantic and Southern Ocean. Out of a total of 188 cruise entries in the CARINA database, 59 reported pH measured values. Here we present details of the secondary QC on pH for the CARINA database. Procedures of quality control, including crossover analysis between cruises and inversion analysis of all crossover data are briefly described. Adjustments were applied to the pH values for 21 of the cruises in the CARINA dataset. With these adjustments the CARINA database is consistent both internally as well as with GLODAP data, an oceanographic data set based on the World Hydrographic Program in the 1990s. Based on our analysis we estimate the internal accuracy of the CARINA pH data to be 0.005 pH units. The CARINA data are now suitable for accurate assessments of, for example, oceanic carbon inventories and uptake rates and for model validation.
Automated sequence analysis of atmospheric oxidation pathways: SEQUENCE version 1.0
Authors: Butler T. M.
Published: April 2010

Abstract. An algorithm for the sequential analysis of the atmospheric oxidation of chemical species using output from a photochemical model is presented. Starting at a "root species", the algorithm traverses all possible reaction sequences which consume this species, and lead, via intermediate products, to final products. The algorithm keeps track of the effects of all of these reactions on their respective reactants and products. Upon completion, the algorithm has built a detailed picture of the effects of the oxidation of the root species on its chemical surroundings. The output of the algorithm can be used to determine product yields, radical recycling fractions, and ozone production potentials of arbitrary chemical species.
The Lagrangian chemistry and transport model ATLAS: validation of advective transport and mixing
Authors: Wohltmann I. , Rex M.
Published: April 2010

Abstract. We present a new global Chemical Transport Model (CTM) with full stratospheric chemistry and Lagrangian transport and mixing called ATLAS (Alfred Wegener InsTitute LAgrangian Chemistry/Transport System). Lagrangian (trajectory-based) models have several important advantages over conventional Eulerian (grid-based) models, including the absence of spurious numerical diffusion, efficient code parallelization and no limitation of the largest time step by the Courant-Friedrichs-Lewy criterion. The basic concept of transport and mixing is similar to the approach in the commonly used CLaMS model. Several aspects of the model are different from CLaMS and are introduced and validated here, including a different mixing algorithm for lower resolutions which is less diffusive and agrees better with observations with the same mixing parameters. In addition, values for the vertical and horizontal stratospheric bulk diffusion coefficients are inferred and compared to other studies. This work focusses on the description of the dynamical part of the model and the validation of the mixing algorithm. The chemistry module, which contains 49 species, 170 reactions and a detailed treatment of heterogeneous chemistry, will be presented in a separate paper.
Evaluation of the new UKCA climate-composition model – Part 1: The stratosphere
Authors: Morgenstern O. , Braesicke P. , O'Connor F. M. , Bushell A. C. , Johnson C. E. , Osprey S. M. , Pyle J. A.
Published: April 2010

Abstract. The UK Chemistry and Aerosols (UKCA) model is a new aerosol-chemistry model coupled to the Met Office Unified Model capable of simulating composition and climate from the troposphere to the mesosphere. Here we introduce the model and assess its performance with a particular focus on the stratosphere. A 20-year perpetual year-2000 simulation forms the basis of our analysis. We assess basic and derived dynamical and chemical model fields and compare to ERA-40 reanalyses and satellite climatologies. Polar temperatures and the lifetime of the southern polar vortex are well captured, indicating that the model is suitable for assessing the ozone hole. Ozone and long-lived tracers compare favourably to observations. Chemical-dynamical coupling, as evidenced by the anticorrelation between winter-spring northern polar ozone columns and the strength of the polar jet, is also well captured. Remaining problems relate to a warm bias at the tropical tropopause, slow ascent in the tropical pipe with implications for the lifetimes of long-lived species, and a general overestimation of ozone columns in middle and high latitudes.
Upgrading photolysis in the p-TOMCAT CTM: model evaluation and assessment of the role of clouds
Authors: Voulgarakis A. , Savage N. H. , Wild O. , Carver G. D. , Clemitshaw K. C. , Pyle J. A.
Published: April 2010

Abstract. A new version of the p-TOMCAT Chemical Transport Model (CTM) which includes an improved photolysis code, Fast-JX, is validated. Through offline testing we show that Fast-JX captures well the observed J(NO2) and J(O1D) values obtained at Weybourne and during a flight above the Atlantic, though with some overestimation of J(O1D) when comparing to the aircraft data. By comparing p-TOMCAT output of CO and ozone with measurements, we find that the inclusion of Fast-JX in the CTM strongly improves the latter's ability to capture the seasonality and levels of tracers' concentrations. A probability distribution analysis demonstrates that photolysis rates and oxidant (OH, ozone) concentrations cover a broader range of values when using Fast-JX instead of the standard photolysis scheme. This is not only driven by improvements in the seasonality of cloudiness but also even more by the better representation of cloud spatial variability. We use three different cloud treatments to study the radiative effect of clouds on the abundances of a range of tracers and find only modest effects on a global scale. This is consistent with the most relevant recent study. The new version of the validated CTM will be used for a variety of future studies examining the variability of tropospheric composition and its drivers.
Streamflow data assimilation for soil moisture analysis
Authors: Warrach-Sagi K. , Wulfmeyer V.
Published: April 2010

Abstract. Streamflow depends on the soil moisture of a river catchment and can be measured with relatively high accuracy. The soil moisture in the root zone influences the latent heat flux and, hence, the quantity and spatial distribution of atmospheric water vapour and precipitation. As numerical weather forecast and climate models require a proper soil moisture initialization for their land surface models, we enhanced an Ensemble Kalman Filter to assimilate streamflow time series into the multi-layer land surface model TERRA-ML of the regional weather forecast model COSMO. The impact of streamflow assimilation was studied by an observing system simulation experiment in the Enz River catchment (located at the downwind side of the northern Black Forest in Germany). The results demonstrate a clear improvement of the soil moisture field in the catchment. We illustrate the potential of streamflow data assimilation for weather forecasting and discuss its spatial and temporal requirements for a corresponding, automated river gauging network.
Pliocene Model Intercomparison Project (PlioMIP): experimental design and boundary conditions (Experiment 1)
Authors: Haywood A. M. , Dowsett H. J. , Otto-Bliesner B. , Chandler M. A. , Dolan A. M. , Hill D. J. , Lunt D. J. , Robinson M. M. , Rosenbloom N. , Salzmann U. , Sohl L. E.
Published: April 2010

Abstract. In 2008 the temporal focus of the Palaeoclimate Modelling Intercomparison Project was expanded to include a model intercomparison for the mid-Pliocene warm period (3.29–2.97 million years ago). This project is referred to as PlioMIP (Pliocene Model Intercomparison Project). Two experiments have been agreed upon and comprise phase 1 of PlioMIP. The first (Experiment 1) will be performed with atmosphere-only climate models. The second (Experiment 2) will utilise fully coupled ocean-atmosphere climate models. The aim of this paper is to provide a detailed model intercomparison project description which documents the experimental design in a more detailed way than has previously been done in the literature. Specifically, this paper describes the experimental design and boundary conditions that will be utilised for Experiment 1 of PlioMIP.
GENIE-M: a new and improved GENIE-1 developed in Minnesota
Authors: Matsumoto K. , Tokos K. S. , Price A. , Cox S.
Published: April 2010

Abstract. Here we describe GENIE-M, a new and improved version of the Grid ENabled Integrated Earth system model (GENIE), which is a 3-D earth system model of intermediate complexity. Main development goals of GENIE-M were to: (1) bring oceanic uptake of anthropogenic transient tracers within data constraints; (2) increase vertical resolution in the upper ocean to better represent near-surface biogeochemical processes; (3) calibrate the deep ocean ventilation with observed abundance of radiocarbon. We achieved all these goals through a transparent process of calibration that mostly consisted of objective model optimization. An important new feature in GENIE-M that dramatically improved the uptake of CFC-11 and anthropogenic carbon is the depth dependent vertical diffusivity in the ocean, which is spatially uniform in GENIE-1. In GENIE-M, biological production occurs in the top two layers above the compensation depth of 100 m and is modified, for example, by diagnosed mixed layer depth. In contrast, production in GENIE-1 occurs in a single layer with thickness of 175 m. These improvements make GENIE-M a well-calibrated model of intermediate complexity suitable for investigations of the global marine carbon cycle requiring long integration time.
Evaluation of the new UKCA climate-composition model – Part I: The stratosphere
Authors: Morgenstern O. , Braesicke P. , O'Connor F. M. , Bushell A. C. , Johnson C. E. , Osprey S. M. , Pyle J. A.
Published: April 2010

Abstract. The UK Chemistry and Aerosols model is a new aerosol-chemistry model coupled to the Met Office Unified Model capable of simulating composition and climate from the troposphere to the mesosphere. Here we introduce the model and assess its performance with a particular focus on the stratosphere. A 20-year perpetual year-2000 simulation forms the basis of our analysis. We compare the model results to ERA-40 reanalyses and some observational climatologies, and also assess aspects of dynamical-chemical coupling.
Evaluation of the parametrized transport of lead-210 in high-altitude European sites
Authors: Dombrowski-Etchevers I. , Peuch V.-H. , Josse B. , Legrand M.
Published: April 2010

Abstract. One important aspect in current climate modelling is to correctly simulate the regional variability of aerosols forcings. A first step to address this issue is to evaluate the tropospheric vertical distribution of submicronic aerosol (including sulfate and organic aerosol) in particular in the free troposphere. 210Pb is particularly interesting to study the dynamic transport by chemistry and transport models, because it is an excellent passive tracer of atmospheric circulation. Hence, it is a simple representative of atmospheric submicronic aerosol and its transport is well correlated with sulfate aerosol. Indeed, 210Pb and 222Rn (its radioactive parent) have been widely used for model verification. We present here pluriannual simulations of 210Pb made with the multiscale global to regional model MOCAGE of Météo-France, which allows to investigate resolution effects over Europe and specially anomalies in link with the heat wave episode of summer 2003 and associated increased convection. Precisely, simulations over Europe over 3 years, 2002 to 2004, are compared with the original dataset gathered in particular over high-altitude sites during the CARBOSOL project. We particularly focus our attention on the vertical unresolved-scale transport parameterisation and analyse the strong seasonality in 210Pb concentrations (maximum in summer, minimum in winter), which was exceptionnally marked in 2003.
An Intermediate Complexity Climate Model (ICCM) based on the GFDL Flexible Modelling System
Authors: Farneti R. , Vallis G. K.
Published: April 2010

Abstract. An intermediate complexity coupled ocean-atmosphere-land-ice model, based on the Geophysical Fluid Dynamics Laboratory (GFDL) Flexible Modelling System (FMS), has been developed to study mechanisms of ocean-atmosphere interactions and natural climate variability at interannual to interdecadal and longer time scales. The model uses the three-dimensional primitive equations for both ocean and atmosphere, but is simplified from a "state of the art" coupled model in two respects: it uses simplified physics and parameterisation schemes, especially in the atmosphere, and idealised geometry and geography. These simplifications provide considerable savings in computational expense and, perhaps more importantly, allow mechanisms to be investigated more cleanly and thoroughly than with a more elaborate model. For example, the model allows integrations of several millennia as well as broad parameter studies. For the ocean, the model uses the free surface primitive equations Modular Ocean Model (MOM) and the GFDL/FMS sea-ice model (SIS) is coupled to the oceanic grid. The atmospheric component consists of the FMS B-grid moist primitive equations atmospheric dynamical core with highly simplified physical parameterisations. A simple bucket model is implemented for our idealised land following the GFDL/FMS Land model. Here we describe the model components and present a climatology of coupled simulations achieved with two different geometrical configurations. Throughout the paper, we give a flavour of the potential for this model to be a powerful tool for the climate modelling community by mentioning a wide range of studies that are currently being explored.
OASIS4 – a coupling software for next generation earth system modelling
Authors: Redler R. , Valcke S. , Ritzdorf H.
Published: April 2010

Abstract. In this article we present a new version of the Ocean Atmosphere Sea Ice Soil coupling software (OASIS4). With this new fully parallel OASIS4 coupler we target the needs of Earth system modelling in its full complexity. The primary focus of this article is to describe the design of the OASIS4 software and how the coupling software drives the whole coupled model system ensuring the synchronization of the different component models. The application programmer interface (API) manages the coupling exchanges between arbitrary climate component models, as well as the input and output from and to files of each individual component. The OASIS4 Transformer instance performs the parallel interpolation and transfer of the coupling data between source and target model components. As a new core technology for the software, the fully parallel search algorithm of OASIS4 is described in detail. First benchmark results are discussed with simple test configurations to demonstrate the efficiency and scalability of the software when applied to Earth system model components. Typically the compute time needed in order to perform the search is in the order of a few seconds and is only weakly dependant on the grid size.
A kinetic chemistry tagging technique and its application to modelling the stable isotopic composition of atmospheric trace gases
Authors: Gromov S. , Jöckel P. , Sander R. , Brenninkmeijer C. A. M.
Published: April 2010

Abstract. Isotope composition, in many cases, holds unique information on sources, chemical modification and sinks of atmospheric trace gases. Vital to the interpretation and use of an increasing number of isotope analyses is appropriate modelling. However, the exact implementation of isotopic information is a challenge, and often studies use simplifications which limit their applicability. Here we confer a thorough isotopic extension to MECCA, a comprehensive kinetic chemistry sub-model. To this end, we devise a generic tagging technique for the kinetic chemistry mechanisms implemented as the sub-submodel MECCA-TAG. The technique constitutes a diagnostic tool that can benefit the investigation of various aspects of kinetic chemistry schemes; at the same time, the designed numerical optimisation reduces the computational effort while keeping important details unaffected. We further focus specifically on the modelling of stable isotopic composition, including the required extensions of the approach. The results of MECCA-TAG are evaluated against the reference sub-submodel MECCA-DBL, which is implicitly full-detailed, but necessarily is sub-optimal in practical applications due to its high computational demands. Furthermore, we evaluate the elaborate carbon and oxygen isotopic mechanism by simulating the multi-isotope composition of CO and other trace gases in the CAABA/MECCA box-model. The mechanism realistically simulates the oxygen isotope composition of key species resulting from the interchange with ozone and main atmospheric reservoirs, as well as the carbon isotope signature transfer. The model adequately reproduces the isotope chemistry features for CO under the limitation of the modelling domain. In particular, the mass-independently fractionated (MIF) composition of CO due to reactions of ozone with unsaturated hydrocarbons (a source effect) versus its intrinsic MIF enrichment induced in the removal reaction via oxidation by OH is assessed. As for the simulated conditions, the ozone source effect was found to be up to +1‰ in Δ17O(CO). The versatile modelling framework we employ (the Modular Earth Submodel System, MESSy) opens the way for implementation of the novel detailed isotopic chemistry treatment in the three-dimensional atmospheric-chemistry general circulation model EMAC. We therefore also present estimates of the computational gain obtained by the developed optimisations.
The accuracy of simple soil water models in climate forecasting
Authors: Blyth E. M. , Daamen C. C.
Published: April 2010

Abstract. Several simple soil water models with four layers or less, typical of those used in GCMS, are compared to a complex multilayered model. They are tested by applying a repeating wetting/drying cycle at different frequencies, and run to equilibrium. The ability of the simple soil models to reproduce the results of the multilayer model vary according to the frequency of the forcing cycle, the soil type, the number of layers and the depth of the top layer of the model. The best overall performance was from the four layer model. The two layer model with a thin top layer (0.1 m) modelled sandy soils well while the two layer model with a thick top layer (0.5 m) modelled clay soils well. The model with just one layer overestimated evaporation during long drying periods for all soil types.
Electrical Imaging of Saline Tracer Migration for the Investigation of Unsaturated Zone Transport Mechanisms
Authors: Slater L. , Zaidman M. D. , Binley A. M. , West L. J.
Published: April 2010

Abstract. Abstract: Better understanding of field-scale unsaturated zone transport mechanisms is required if the fate of contaminants released at the surface is to be predicted accurately. Interpretation of results from direct tracer sampling in terms of operative hydraulic processes is often limited by the poor spatial coverage and the invasive nature of such techniques. Cross-borehole electrical imaging during progress of saline tracer migration is proposed to assist investigation of field-scale solute transport in the unsaturated zone. Electrical imaging provides non-destructive, high density and spatially continuous sampling of saline tracer transport injected over an area of the ground surface between two boreholes. The value of electrical imaging was tested at a field site on an interfluve of the UK Chalk aquifer. Improved understanding of active transport mechanisms in the unsaturated zone of the UK Chalk is required to predict its vulnerability to surface pollutants. In a tracer experiment in May 1996, a conductive saline tracer was infiltrated over 18 m2 at an average rate of 47 mm day-1 for 56 hours. Cross-borehole images obtained during and after infiltration show a large, homogenous, resistivity reduction in the top 3 m, no change between 3 m and 6 m depth, and smaller, inhomogeneous, resistivity reductions below 6 m depth. The resistivity has reduced at down to 15 m depth less than 2 days after tracer infiltration began. Hydrological interpretation of a sequence of electrical images obtained prior to, during, and up to three months after tracer injection suggests: (1) rapid tracer entry into the soil zone and upper 2 m of weathered Chalk, (2) intergranular transport of the bulk of the tracer, (3) a significant fissure flow component transporting tracer to at least 15 m depth in 31 hours, and (4) vertical changes in transport mechanisms possibly caused by interception of fissures by marl layers. The results of this experiment suggest that electrical imaging can assist the description of unsaturated zone hydraulic mechanisms through visual identification of spatial and temporal variations in transport processes.
A comparative study of the soil solution chemistry of two Amazonian forest soils (Central Amazonia, Brazil)
Authors: Cornu, S. , Ambrosi J. P. , Lucas Y. , Fevrier D.
Published: April 2010

Abstract. Analyses of the chemical composition of rapidly percolating soil water were used to study the genesis of a shallow podzol in a Campinarana forest and a clayey ferralsol from a typical rainforest located in North Manaus (Amazonia, Brazil). The samples were collected in lysimeters and analysed for Ca2+, Na+, K+, NH4+, SO42-, NO3-, Fe, Si, and Al. A large percentage of the nutrients was recycled in the upper 40 centimetres of both soils. The soil water concentrations in nutrients were very similar for both environments but levels of Si, Fe and AI were higher in the podzol than in the ferralsol. In the podzolic environment, the waters were enriched in Si, Fe and AI when passing through the organic layer and the top 10 cm of the soil. The concentrations decreased between 10 and 40 cm depth due to variations in mineralogy of this soil. In the ferralsol, the Si concentrations increased considerably on reaching the soil top-horizons while small increases occurred for AI and Fe. Thermodynamic equilibrium calculations indicate that most of the dissolved AI and Fe in both soil environments were in the form of organometallic complexes and that the waters were under-saturated in respect to kaolinite and gibbsite.
The effects of clear-felling established forestry on stream-flow losses from the Hore sub-catchment
Authors: Roberts G. , Crane S. B.
Published: April 2010

Abstract. The effects on streamflow of clear-felling a substantial part of the established forestry within the Hore sub-catchment at Plynlimon were estimated by a regression comparison of pre-and post-felling rainfall/runoff relationships and by a model based on evapotranspiration estimates from plot studies of established forestry and heather moorland. Increases in streamflow were predicted using both methods, with those using the regression method being substantially larger than those using the model. The largest increases using the regression method occurred about 5 years after the end of felling, and amounted to 10.5% of the measured annual flow. On a seasonal basis, the largest increases using the regression method occurred during the latter half of the year, whilst the model predicted the largest increases during the summer months. These patterns are explained in terms of forest transpiration and canopy interception.
Effects of summer drought on peat soil solution chemistry in an acid gully mire
Authors: Hughes S. , Reynolds B. , Hudson J. A. , Freeman C.
Published: April 2010

Abstract. In a field experiment to investigate potential impacts of climatic change, a small area of flush wetland in Wales was subjected to three successive years of simulated summer drought/rewetting (autumn-spring) cycles (1992–94). Drought was simulated achieved by diverting stream water around the experimental wetland during the summer, so that the wetland received only precipitation inputs during that time. The effects on peat-water chemistry in the rhizosphere were monitored at regular intervals until spring 1996, and comparisons made with a control. Simulated summer drought decreased, significantly, the natural summer peaks in dissolved organic carbon (DOC) and iron, whilst subsequently increasing the natural autumn-winter peaks in sulphate concentrations and acidity in the peat water. The effects of simulated drought on SO4 concentrations in the peat water compared favourably with subsequent events monitored following a natural summer drought in 1995. Autumn-winter peaks in SO4 concentrations in the control wetland following the natural drought were of similar magnitude to those induced by the drought simulated in the experimental wetland in the previous three years.
A Regionalised Neyman-Scott Model of Rainfall with Convective and Stratiform Cells
Authors: Cowpertwait P. S. P. , O'Connell P. E.
Published: April 2010

Abstract. A single-site Neyman-Scott Poisson cluster model of rainfall, with convective and stratiform cells, is fitted to data for 112 sites scattered throughout the UK using harmonic variables to account for seasonality. The model is regionalised by regressing the estimates of the harmonic variables on site dependent variables (e.g. altitude) to enable rainfall to be simulated at any ungauged site in the UK. An assessment of the residual errors indicates that the regression models can be used with reasonable confidence for urban sites. Furthermore, the regional variations of the model parameter estimates are found to be in agreement with meteorological knowledge and observation. Simulated I h extreme rainfalls are found to compare favourably with observed historical values, although some lack-of-fit is evident for higher aggregation levels.
Critical loads for soils and freshwaters; a comparison methods at the Plynlimon catchments
Authors: Jenkins A. , Coric S. , Reynolds B. , Curtis C. , Renshaw M.
Published: April 2010

Abstract. International agreements aimed at reducing sulphur deposition from the atmosphere are now focused on the "critical loads" concept. This provides a distributed link between sources and receptors of acidic oxides and also links the level of reduction with biological recovery. Methods for calculating critical loads include simple classification (Level 0), mass-balance equilibrium models (Level 1) and dynamic hydrochemical models (Level 2). Here, examples of each method are applied to headwater catchments in Plynlimon, mid-Wales. The critical loads derived are compared and the utility of the critical loads concept as a tool for local pollution control and land management is assessed. Differences in critical load methods for soils result from assumptions regarding biological receptors. Surface water critical loads are generally similar under all methods. As a local management tool, the dynamic model is most appropriate although it has a high data requirement. The utility of other methods depends upon detailed maps of soil and vegetation being available at an appropriate scale.
A view of water quality from the Plynlimon watershed
Authors: Neal C.
Published: April 2010

Abstract. A summary of hydrochemical research in the Plynlimon catchments from 1983 to the present is related to identifying water flow pathways within catchments and the modelling of soil and stream water acidification. The study reveals a highly heterogeneous system that barely conforms with current understanding of hydrology and acidification theory. The role of hydrochemical mixing processes and groundwater flow routing is emphasised as is the need for maintaining long term monitoring studies and enhancing process based studies of water and chemical fluxes through catchments. The applicability of current environmental impact models for predictive and environmental management purposes is questioned and it is proposed that new hydrochemical modelling structures are needed to examine the highly heterogeneous systems being modelled.
A combined field and numerical approach to investigate flow processes in natural macroporous soils under extreme precipitation
Authors: Faeh A. O. , Scherrer S. , Naef F.
Published: April 2010

Abstract. A procedure involving simultaneous experimental and numerical research is described for the purposes of understanding the mechanisms involved when extreme precipitation is transformed to flood stream discharge. It is shown that experiments and model applications by themselves are not sufficient for process identification, but that their combined application provides considerable insight into the subsurface flow processes. The proposed approach is unconventional in that a numerical model, based on stringent continuity and momentum criteria, is used as a tool for process identification only. Unlike other studies, it is not intended to demonstrate the applicability of the utilised model for general hydrological applications, or to provide evidence of the suitability of particular model simplifications. Rather, different and sometimes conflicting model realisations are used to examine the plausibility of flow processes which may occur on natural hill slopes. Hereby, small scale effects such as those relating to the mechanisms of water entry into the macropores, and the movement of water to the surrounding matrix are identified from the results of well instrumented field experiments.
Preferential transport of water and 131Iodide in a clay loam assessed with TDR-techniques and boundary-layer flow theory
Authors: Mdaghri Alaoui A. , Germann P. , Lichner L. , Novak V.
Published: April 2010

Abstract. Rapid soil moisture variations were measured with TDR equipment at five depths ranging from 0.1 to 0.9 m during five consecutive infiltration experiments under ponding. Each time, 27 mm of water were applied. The water of the second experiment was spiked with 200 mbq of K131I-tracer. Its activity was recorded as functions of depth and time with Geiger-Müller probes in 12 vertically installed access tubes. The soil moisture variations were classified as showing (i) no reaction, (ii) monotonous increase, and (iii) rapid increase followed by a gradual decrease. Reaction type (iii) was investigated further according to the boundary-layer flow theory and diagnosed as preferential flow. Rapid variations of 131I-activities occurred at all depths showing soil moisture reaction type (iii). However, some of the reaction types (i) and (ii) also included rapid variations of the activities. The approach based on boundary-laver flow theory allows fluxes to be estimated from soil moisture variations. Seven estimated total volumes of rapid flow ranged from 0.15 to 1.1 of the applied volume of water, and in only one case was the total volume badly overestimated by a factor of almost 3. The approach is worth further exploration.
Prediction of chloride leaching from a non-irrigated, de-watered saline soil using the MACRO model
Authors: Bourgault du Coudray P. L. , Williamson D. R. , Scott W. D.
Published: April 2010

Abstract. A pedon scale study was conducted to investigate the degree of chloride leaching from a de-watered saline soil profile in the non-irrigated wheatbelt region of south-western Australia. Within the surface 250mm of the soil profile was a dispersed layer acting as a hydraulic throttle. Soil water tensions and chloride concentrations were obtained over a two-year period over depths ranging from 0.2m to 1.5m. In the first year the soil surface remained untouched. In the second year, the throttle layer was fractured by ripping to a depth of 250mm. Rainfall, runoff and potential evaporation were also measured at the site. These data were used to calibrate and run the MACRO solute transport model using three surface treatment management scenarios: I. the soil surface remains unchanged (`Do nothing'); II. the soil surface is continually ripped; III. the soil surface is ripped followed by surface scaling. The time period required, effectively, to leach the chloride from the profile, to a depth of 1.5m, was predicted. Effective leaching would take at least 400 years and possibly in excess of 200,000 years for Treatment I, 5 years for Treatment II and 90 years for Treatment III. Macropores that were observed within the sub-surface soil profile played no significant role in the leaching of the chloride. However, the rip fractures were treated as macropores by the MACRO model and as such allowed greater infiltration of water that resulted in the mobilisation of chloride within the rest of the soil profile.
Translating environmental xenobiotic fate models across scales
Authors: Richter O. , Diekkrüger B.
Published: April 2010

Abstract. The classical models developed for degradation and transport of xenobiotics have been derived with the assumption of homogeneous environments. Unfortunately, deterministic models function well in the laboratory under homogeneous conditions but such homogeneous conditions often do not prevail in the field. A possible solution is the incorporation of the statistical variation of soil parameters into deterministic process models. This demands the development of stochastic models of spatial variability. To this end, spatial soil parameter fields are conceived as the realisation of a random spatial process. Extrapolation of local fine scale models to large heterogeneous fields is achieved by coupling deterministic process models with random spatial field models.
Determination of evaporation from a catchment water balance at a monthly time scale
Authors: Savenije H. H. G.
Published: April 2010

Abstract. A method is presented to determine total evaporation from the earth's surface at a spatial scale that is adequate for linkage with climate models. The method is based on the water balance of catchments, combined with a calibrated autoregressive rainfall-runoff model. The time scale used is in the order of decades (10 days) to months. The rainfall-runoff model makes a distinction between immediate processes (interception and short term storage) and the remaining longer-term processes. Besides the calibrated rainfall-runoff model and the time series of observed rainfall and runoff, the method requires a relation between transpiration and soil moisture storage. The method is applied to data of the Bani catchment in Mali, a sub-catchment of the Niger river basin.
On the calculation of the topographic wetness index: evaluation of different methods based on field observations
Authors: Sørensen R. , Zinko U. , Seibert J.
Published: April 2010

Abstract. The topographic wetness index (TWI, ln(a/tanβ)), which combines local upslope contributing area and slope, is commonly used to quantify topographic control on hydrological processes. Methods of computing this index differ primarily in the way the upslope contributing area is calculated. In this study we compared a number of calculation methods for TWI and evaluated them in terms of their correlation with the following measured variables: vascular plant species richness, soil pH, groundwater level, soil moisture, and a constructed wetness degree. The TWI was calculated by varying six parameters affecting the distribution of accumulated area among downslope cells and by varying the way the slope was calculated. All possible combinations of these parameters were calculated for two separate boreal forest sites in northern Sweden. We did not find a calculation method that performed best for all measured variables; rather the best methods seemed to be variable and site specific. However, we were able to identify some general characteristics of the best methods for different groups of measured variables. The results provide guiding principles for choosing the best method for estimating species richness, soil pH, groundwater level, and soil moisture by the TWI derived from digital elevation models.
Top-kriging - geostatistics on stream networks
Authors: Skøien J. O. , Merz R. , Blöschl G.
Published: April 2010

Abstract. We present Top-kriging, or topological kriging, as a method for estimating streamflow-related variables in ungauged catchments. It takes both the area and the nested nature of catchments into account. The main appeal of the method is that it is a best linear unbiased estimator (BLUE) adapted for the case of stream networks without any additional assumptions. The concept is built on the work of Sauquet et al. (2000) and extends it in a number of ways. We test the method for the case of the specific 100-year flood for two Austrian regions. The method provides more plausible and, indeed, more accurate estimates than Ordinary Kriging. For the variable of interest, Top-kriging also provides estimates of the uncertainty. On the main stream the estimated uncertainties are smallest and they gradually increase as one moves towards the headwaters. The method as presented here is able to exploit the information contained in short records by accounting for the uncertainty of each gauge. We suggest that Top-kriging can be used for spatially interpolating a range of streamflow-related variables including mean annual discharge, flood characteristics, low flow characteristics, concentrations, turbidity and stream temperature.