Modelling the effects of Zostera noltei meadows on sediment dynamics: application to the Arcachon lagoon

A three-dimensional model has been modified to describe the complex interactions between hydrodynamics, sediment dynamics and biological parameters in the presence of Zostera noltei. The model treats seagrass leafs as flexible blades that bend under hydrodynamic forcing and alter the local momentum and turbulence fluxes and, therefore, the benthic shear conditions; these changes cause related changes to the mass balance at the boundary of the bed, in turn affecting the suspended matter in the column and ultimately primary productivity and the growth of the dwarf-grass. Modelling parameters related to the impact of Z. noltei to the local flow and to erosion and deposition rates were calibrated using flume experimental measurements; results from the calibration of the model are presented and discussed. The coupled model is applied in the Arcachon Bay, an area with high environmental significance and large abundance of dwarf-grass meadows. In the present paper, results from preliminary applications of the model are presented and discussed; the effectiveness of the coupled model is assessed comparing modelling results with available field measurements of suspended sediment concentrations and seagrass growth parameters. The model generally reproduces sediment dynamics and dwarf-grass seasonal growth in the domain efficiently. Investigations regarding the effects of the vegetation to the near-bed hydrodynamics and to the sediment suspension in the domain show that dwarf-grass meadows play an important part to velocity attenuation and to sediment stabilisation, with flow and suspended sediment concentrations damping, compared to an unvegetated state, to reach 35–50 and 65 %, respectively, at peak seagrass growth.     

Lentil Straw: A Novel Adsorbent for Removing of Hazardous Dye – Sorption Behavior Studies

Sorption behavior of Lanaset Red (LR) G on lentil straw (LS) was studied as a function of particle size, adsorbent dose, initial pH value, initial dye concentration, and contact time. Sorption kinetics data was well described by logistic model. Modified logistic equation can be used to explain effects of initial dye concentrations and contact time on the sorption of LR G with high R² value. Freundlich model was found to be excellent in representing the equilibrium data. Thermodynamic parameters like free energy (ΔG⁰), enthalpy (ΔH⁰), and entropy (ΔS⁰) were calculated by the use of Langmuir constant. Thermodynamic data showed that the sorption processes were spontaneous and endothermic in nature. Desorption process suggested that strong binding and weak interactions could be formed between adsorbent surface and dye molecules. Results revealed that LS has a remarkable potential for the sorption of LR G.     

Aerosol Forcing: Rapporteur’s Report and Summary

This paper summarizes the discussions held during the session dedicated to Aerosol forcing at the Workshop Observing and Modelling Earth’s Energy Flows. The session Aerosol forcing was convened by P. Ingmann and J. Heintzenberg and included 10 presentations given by R. Kahn, D. Winker, U. Baltensperger, J. Haywood, S. Schwartz, J. Heintzenberg, H. Le Treut, U. Lohmann, R. Wood, and E. Philipona. The presentations given ranged from overviews of current observational capabilities to analyses of aerosol–cloud interactions in observations and models of varying complexity. This paper is organized around a few key points, summarizing the major points of agreement, disagreement, and discussion that the presentations gave rise to. The focus is largely on the uncertainties that remain with regard to aerosol forcing, particularly related to aerosol-cloud interactions and indirect aerosol effects on climate.     

Modelling river and riparian vegetation interactions and related importance for sustainable ecosystem management

We discuss the importance of modelling riparian vegetation and river flow interactions under differing hydrologic regimes. Modelling tools have notable implications with regard to the understanding of riverine ecosystem functioning and to promote sustainable management of water resources. We present both deterministic and stochastic approaches with different levels of simplification, and discuss their use in relation to river and vegetation dynamics at the related scale of interest. We apply such models to both meandering and braided rivers, in particular focusing on the floodplain dynamics of an alpine braided river affected by water impoundment. For this specific case we show what the expected changes in riparian vegetation may be in a ‘controlled release’ scenario for the postdam river Maggia, Switzerland. Finally, the use of these models is discussed in the context of current research efforts devoted to river restoration practice.     

Zur Modellierung der Adsorption von Mehrkomponentensystemen

Many dissolved organic compounds in waters and wastewaters can be effectively removed by adsorption processes. The design of such processes requires the modelling of adsorption equilibria in multi-solute systems. In this paper a review on the most useful equilibrium models for multicomponent systems of known and unknown composition is presented.     

Numerical and analogue modelling of induction effects in laterally non-uniform conductors

Modelling of electromagnetic fields in laterally non-uniform geoelectric structures is briefly reviewed. Attention is paid to progress achieved specifically during the last three years in numerical and analogue techniques of solving two- and three-dimensional problems. Some new important results are also mentioned.     

Aluminium solubility controls in acid waters: the need for a reappraisal

Stability diagrams have been frequently used to demonstrate aluminium solubility controls in acidic stream and soil waters. This paper shows that it is possible by this method to generate apparent controls using random numbers in place of stream chemistry data. Thermodynamic arguments demonstrate that a wide variety of reactions can produce relationships similar to Al(OH)₃ solubility controls. It is proposed that stability diagrams alone should be used with great caution in identifying aluminium solubility controls, taking care that their axes are independent. Thermodynamic solubility calculations should be used with due scepticism. Supplementary investigations should be used where possible to identify phases precipitating or dissolving.     

Spatially non‐local model of inelastic deformations: applications for rock failure problem

A spatially non‐local model for inelastic deformation of solids is proposed and studied. The non‐locality of deformation is taken into account by the additional parameter of state beyond the classical parameters such as stress and strain tensors. This additional parameter is the curvature tensor expressed in terms of the metric strain tensor, and it is called the failure parameter. In the case of small deformation, it is equivalent to the Saint‐Venant incompatibility tensor. Thermodynamic properties of the model are studied, and governing differential equations for spatially non‐local model are formulated, which are composed by the elasticity equations and parabolic equation for the failure parameter. The model can be applied to the study of the rock failure problem, and as an example, the one‐dimensional problem for the deformation of half‐plane loaded by the normal surface stress is studied. Stationary and non‐stationary formulations of the problem are considered, and qualitative agreement with available experimental data is observed.     

Stochastic analysis of a field-scale unsaturated transport experiment

Modelling of field-scale transport of chemicals is of deep interest to public as well as private sectors, and it represents an area of active theoretical research in many environmentally-based disciplines. However, the experimental data needed to validate field-scale transport models are very limited due to the numerous logistic difficulties that one faces out.     

Assessing uncertainties in urban drainage models

The current state of knowledge regarding uncertainties in urban drainage models is poor. This is in part due to the lack of clarity in the way model uncertainty analyses are conducted and how the results are presented and used. There is a need for a common terminology and a conceptual framework for describing and estimating uncertainties in urban drainage models. Practical tools for the assessment of model uncertainties for a range of urban drainage models are also required to be developed. This paper, produced by the International Working Group on Data and Models, which works under the IWA/IAHR Joint Committee on Urban Drainage, is a contribution to the development of a harmonised framework for defining and assessing uncertainties in the field of urban drainage modelling. The sources of uncertainties in urban drainage models and their links are initially mapped out. This is followed by an evaluation of each source, including a discussion of its definition and an evaluation of methods that could be used to assess its overall importance. Finally, an approach for a Global Assessment of Modelling Uncertainties (GAMU) is proposed, which presents a new framework for mapping and quantifying sources of uncertainty in urban drainage models.     

The stable isotope composition of Dead Sea waters

Dead Sea waters are moderately enriched in¹⁸O; the degree of enrichment constitutes a balance between the dilution by freshwater influx and the isotope fractionation which accompanies evaporative water loss and vapour exchange with the atmospheric moisture. Modelling of the seasonal cycle and long-term trends of δ¹⁸O, in response to the changes in the environmental parameters, shows that the major control is exercised by the salinity of the surface waters, through its effect on the vapour pressure gradient between the lake's surface and the atmosphere; the (steady state) isotopic composition of the more saline brines tends towards less enriched¹⁸O values. This fact can explain the relatively high δ¹⁸O levels encountered in the Lisan formation, which was deposited from Lake Lisan, —the less saline Pleistocene precursor of the Dead Sea.     

Overview of the EUROSAM project and a Decision Support System

The EUROpean SAlt marshes Modelling (EUROSAM) project is part of the Thematic Network European Land–Ocean Interaction Studies programme. The main aims of the EUROSAM project were to fill in some of the main gaps in the understanding of ecological processes, to integrate this knowledge into models to predict the likely response of salt marsh ecosystems to environmental changes, and to make the knowledge available to decision-makers. Research work and model development for the project were carried out by researchers in France, Portugal, the Netherlands, and England, and included studies on sediment dynamics and interactions with vegetation, plant population dynamics and genetics, models of organic matter production and cycling, studies of animal communities, food webs and organic matter fluxes, and development of hydrodynamic models at different scales: salt marsh, bay, and estuary.This paper describes the main aims and outputs of the EUROSAM project, and the incorporation of the findings and models into a prototype Decision Support System (DSS). The EUROSAM DSS is designed as a guide for the non-specialist to understand the important role and functioning of salt marshes, and for use as a management tool. Example scenarios were selected from the work within the project to illustrate the interactions between components of the salt marsh–mudflat ecosystem, and the potential impact of human activities and environmental change on the salt marsh system.     

Mathematische Modellierung der Komplexbildung von Metallen und ihre Nutzung bei der Interpretation physikochemischer Prozesse in natürlichen Wässern

A mathematical model is presented for the calculation of the concentrations or activities of complex compounds in the thermodynamic equilibrium state. Ten central atoms and ten ligands which form 400 complexes at the most can be included in the model. Complex stability constants, total concentrations of the central atoms and ligands, temperature and pH-value constitute input quantities. Activity and temperature dependence of the stability constants are covered by respective subprogrammes. The model is tested by the migration rate of iron(II) within a sand-filled column with a cation-exchange capacity of 1 mval/100 g solid matter: If there is an excess of sulphate, the iron(II)-breakthrough will be considerably earlier, the same holding for the EDTA-complex, whereas by means of EDTA the iron(II) bonded to the soil by ion exchange can be redissolved. In the batch experiment also the rate of oxidation of iron(II) is dependent on the degree of complexing. The model can be extended for dissolving, precipitation and redox processes.     

Modelling feedbacks between geomorphological and riparian vegetation responses under climate change in a Mediterranean context

Climate change is expected to alter temperatures and precipitation patterns, affecting river flows and hence riparian corridors. In this context we have explored the potential evolution of riparian corridors under a dryness gradient of flow regimes associated with climate change in a Mediterranean river. We have applied an advanced bio‐hydromorphodynamic model incorporating interactions between hydro‐morphodynamics and vegetation. Five scenarios, representing drier conditions and more extreme events, and an additional reference scenario without climate change, have been designed and extended until the year 2100. The vegetation model assesses colonization, growth and mortality of Salicaceae species. We analysed the lower course of the Curueño River, a free flowing gravel bed river (NW Spain), as a representative case study of the Mediterranean region. Modelling results reveal that climate change will affect both channel morphology and riparian vegetation in terms of cover, age distribution and mortality. Reciprocal interactions between flow conditions and riparian species as bio‐engineers are predicted to promote channel narrowing, which becomes more pronounced as dryness increases. Reductions in seedling cover and increases in sapling and mature forest cover are predicted for all climate change scenarios compared with the reference scenario, and the suitable area for vegetation development declines and shifts towards lower floodplain elevations. Climate change also leads to younger vegetation becoming more subject to uprooting and flooding. The predicted reduction in suitable establishment areas and the narrowing of vegetated belts threatens the persistence of the current riparian community. This study highlights the usefulness of advanced bio‐hydromorphodynamic modelling for assessing climate change effects on fluvial landscapes. It also illustrates the need to consider climate change in river management to identify appropriate adaptation measures for riparian ecosystems. Copyright © 2018 John Wiley & Sons, Ltd.     

Groundwater modelling and marine intrusion in the semi‐arid systems (Cap‐Bon,Tunisia)

This article studies the effect of drought and pumping discharge on groundwater supplies and marine intrusion in the Korba aquifer (Cap‐Bon peninsula, Tunisia). The Groundwater Modelling System has been used to model the groundwater flow and to simulate the seawater intrusion. The calibration is based on the groundwater levels in the steady state from 1963, and in the transient state from the groundwater levels from 1963 to 2005. The main objective is to quantify the components of the groundwater mass balance and to estimate the hydraulic conductivity distribution. The impact of pumping discharge on the groundwater level evolution has been examined by two pumping scenarios P1 (no. 8420) and P2 (no. 8862) wells. The hydrodynamic modelling shows the increasing drawdowns after 14 years of pumping: 4 m in P1 well and about 5 m in P2 well below sea level. The drawdowns are accompanied by the inverse hydraulic gradient. The numerical model was used to discuss the management of the groundwater resources of Cap‐Bon. As the population continues to grow and the demand for groundwater pumping intensifies beyond the 1963 level, it can be expected that the actual extent of seawater intrusion in the future would be more severe than the model prediction. Better strategies for groundwater development and management will be necessary to protect the freshwater aquifers to the marine intrusion. Copyright © 2011 John Wiley & Sons, Ltd.     

Bulk density optimization to determine subsurface hydraulic properties in Rocky Mountain catchments using the GEOtop model

Integrated watershed models can be used to calculate streamflow generation in snow‐dominated mountainous catchments. Parameterization of water flow is often complicated by the lack of information on subsurface hydraulic properties. In this study, bulk density optimization was used to determine hydraulic parameters for the upper and lower regolith in the GEOtop model. The methodology was tested in two small catchments in the Dry Creek Watershed in Idaho and the Libby Creek Watershed in Wyoming. Modelling efficiencies for profile‐average soil–water content for the two catchments were between 0.52 and 0.64. Modelling efficiencies for stream discharge (cumulative stream discharge) were 0.45 (0.91) and 0.54 (0.94) for the Idaho and Wyoming catchments, respectively. The calculated hydraulic properties suggest that lateral flow across the upper–lower regolith interface is an important driver of streamflow in both the Idaho and Wyoming watersheds. The overall calibration procedure is computationally efficient because only two bulk density values are optimized. The two‐parameter calibration procedure was complicated by uncertainty in hydraulic conductivity anisotropy. Different upper regolith hydraulic conductivity anisotropy factors had to be tested in order to describe streamflow in both catchments.     

An experimental study of the titanomagnetite solid solution series

Summary Analysis of saturation magnetization measurements and data from the literature indicate that the cation distribution in the titanomagnetite solid solution series is temperature dependent. The ionic configuration of ferric and ferrous ions on both lattice sites of their spinel structure can be described by a modified Boltzmann relation in agreement with theoretical consideratios. Thermodynamic equilibrium isotherms for the cation distribution and the resulting variation of saturation magnetization are calculated on the basis of the experimental values. These results should be especially valuable for the interpretation of magnetic properties of rapidly cooled igneous rock units where a respective high-temperature metastable state may exist in the magnetic ore component.Further measurements of the Curie temperature and lattice constant did not confirm a similar effect. Both these parameters should therefore be qualified for the identification of naturally occurring titanomagnetites.     

Geochemical modelling and speciation studies of metal pollutants present in selected water systems in South Africa

Metal pollutants in water poses great threats to living beings and hence requires to be monitored regularly to avoid loss of lives. Various analytical methods are available to monitor these pollutants in water and can be improved with time. Modelling of metal pollutants in any water system helps chemists, engineers and environmentalists to greatly understand the various chemical processes in such systems. Water samples were collected from waste water treatment plant and river from highlands close to its source all the way to the ocean as it passing through areas with high anthropogenic activities. Pre-concentration of pollutants in the samples was done through acid digestion and metal pollutants were analysed using inductively coupled plasma-optical emission spectra (ICP-OES) to determine the concentration levels. Metal concentrations ranged between 0.1356–0.4658 mg/L for Al; 0.0031–0.0050 mg/L for Co, 0.0019–0.0956 mg/L for Cr; 0.0028–0.3484 mg/L for Cu; 0.0489–0.3474 mg/L for Fe; 0.0033–0.0285 mg/L for Mn; 0.0056–0.0222 mg/L for Ni; 0.0265–0.4753 mg/L for Pb and 0.0052–0.5594 mg/L for Zn. Modelling work was performed using PHREEQC couple with Geochemist’s workbench (GWB) to determine speciation dynamics and bioavailability of these pollutants. Modelling thus adds value to analytical methods and hence a better complementary tool to laboratory-based experimental studies.