A semi-distributed ntegrated itrogen model for multiple source assessment in tchments (INCA): Part I — model structure and process equations

A new model has been developed for assessing multiple sources of nitrogen in catchments. The model (INCA) is process based and uses reaction kinetic equations to simulate the principal mechanisms operating. The model allows for plant uptake, surface and sub-surface pathways and can simulate up to six land uses simultaneously. The model can be applied to catchment as a semi-distributed simulation and has an inbuilt multi-reach structure for river systems. Sources of nitrogen can be from atmospheric deposition, from the terrestrial environment (e.g. agriculture, leakage from forest systems etc.), from urban areas or from direct discharges via sewage or intensive farm units. The model is a daily simulation model and can provide information in the form of time series at key sites, or as profiles down river systems or as statistical distributions. The process model is described and in a companion paper the model is applied to the River Tywi catchment in South Wales and the Great Ouse in Bedfordshire.

The water quality of the River Enborne, UK: observations from high-frequency Monitoring in a rural, lowland river system

This paper reports the results of a 2-year study of water quality in the River Enborne, a rural river in lowland England. Concentrations of nitrogen and phosphorus species and other chemical determinands were monitored both at high-frequency (hourly), using automated in situ instrumentation, and by manual weekly sampling and laboratory analysis. The catchment land use is largely agricultural, with a population density of 123 persons km−2. The river water is largely derived from calcareous groundwater, and there are high nitrogen and phosphorus concentrations. Agricultural fertiliser is the dominant source of annual loads of both nitrogen and phosphorus. However, the data show that sewage effluent discharges have a disproportionate effect on the river nitrogen and phosphorus dynamics. At least 38% of the catchment population use septic tank systems, but the effects are hard to quantify as only 6% are officially registered, and the characteristics of the others are unknown. Only 4% of the phosphorus input and 9% of the nitrogen input is exported from the catchment by the river, highlighting the importance of catchment process understanding in predicting nutrient concentrations. High-frequency monitoring will be a key to developing this vital process understanding.

The catastrophic flash-flood event of 8–9 September 2002 in the Gard region, France: a first case study for the Cévennes–Vivarais Mediterranean Hydrometeorological Observatory

The Cévennes–Vivarais Mediterranean Hydrometeorological Observatory (OHM-CV) is a research initiative aimed at improving the understanding and modeling of the Mediterranean intense rain events that frequently result in devastating flash floods in southern France. A primary objective is to bring together the skills of meteorologists and hydrologists, modelers and instrumentalists, researchers and practitioners, to cope with these rather unpredictable events. In line with previously published flash-flood monographs, the present paper aims at documenting the 8–9 September 2002 catastrophic event, which resulted in 24 casualties and an economic damage evaluated at 1.2 billion euros (i.e., about 1 billion U.S. dollars) in the Gard region, France. A description of the synoptic meteorological situation is first given and shows that no particular precursor indicated the imminence of such an extreme event. Then, radar and rain gauge analyses are used to assess the magnitude of the rain event, which was particularly remarkable for its spatial extent with rain amounts greater than 200 mm in 24 h over 5500 km2. The maximum values of 600–700 mm observed locally are among the highest daily records in the region. The preliminary results of the postevent hydrological investigation show that the hydrologic response of the upstream watersheds of the Gard and Vidourle Rivers is consistent with the marked space–time structure of the rain event. It is noteworthy that peak specific discharges were very high over most of the affected areas (5–10 m3 s−1 km−2) and reached locally extraordinary values of more than 20 m3 s−1 km−2. A preliminary analysis indicates contrasting hydrological behaviors that seem to be related to geomorphological factors, notably the influence of karst in part of the region. An overview of the ongoing meteorological and hydrological research projects devoted to this case study within the OHM-CV is finally presented.

ERA-Interim/Land: a global land surface reanalysis data set

ERA-Interim/Land is a global land surface reanalysis data set covering the period 1979–2010. It describes the evolution of soil moisture, soil temperature and snowpack. ERA-Interim/Land is the result of a single 32-year simulation with the latest ECMWF (European Centre for Medium-Range Weather Forecasts) land surface model driven by meteorological forcing from the ERA-Interim atmospheric reanalysis and precipitation adjustments based on monthly GPCP v2.1 (Global Precipitation Climatology Project). The horizontal resolution is about 80 km and the time frequency is 3-hourly. ERA-Interim/Land includes a number of parameterization improvements in the land surface scheme with respect to the original ERA-Interim data set, which makes it more suitable for climate studies involving land water resources. The quality of ERA-Interim/Land is assessed by comparing with ground-based and remote sensing observations. In particular, estimates of soil moisture, snow depth, surface albedo, turbulent latent and sensible fluxes, and river discharges are verified against a large number of site measurements. ERA-Interim/Land provides a global integrated and coherent estimate of soil moisture and snow water equivalent, which can also be used for the initialization of numerical weather prediction and climate models.

High-frequency water quality monitoring in an urban catchment: hydrochemical dynamics, primary production and implications for the Water Framework Directive

This paper describes the hydrochemistry of a lowland, urbanised river-system, The Cut in England, using in situ sub-daily sampling. The Cut receives effluent discharges from four major sewage treatment works serving around 190,000 people. These discharges consist largely of treated water, originally abstracted from the River Thames and returned via the water supply network, substantially increasing the natural flow. The hourly water quality data were supplemented by weekly manual sampling with laboratory analysis to check the hourly data and measure further determinands. Mean phosphorus and nitrate concentrations were very high, breaching standards set by EU legislation. Though 56% of the catchment area is agricultural, the hydrochemical dynamics were significantly impacted by effluent discharges which accounted for approximately 50% of the annual P catchment input loads and, on average, 59% of river flow at the monitoring point. Diurnal dissolved oxygen data demonstrated high in-stream productivity. From a comparison of high frequency and conventional monitoring data, it is inferred that much of the primary production was dominated by benthic algae, largely diatoms. Despite the high productivity and nutrient concentrations, the river water did not become anoxic and major phytoplankton blooms were not observed. The strong diurnal and annual variation observed showed that assessments of water quality made under the Water Framework Directive (WFD) are sensitive to the time and season of sampling. It is recommended that specific sampling time windows be specified for each determinand, and that WFD targets should be applied in combination to help identify periods of greatest ecological risk. This article is protected by copyright. All rights reserved.

Sediment-contact fish embryo toxicity assay with Danio rerio to assess particle-bound pollutants in the Tiete River Basin (Sao Paulo, Brazil)

The Tiete River and its tributary Pinheiros River receive a highly complex organic and inorganic pollutants load from sanitary sewage and industrial sources, as well as agricultural and agroindustrial activities. The aim of the present study was to evaluate the embryotoxic and teratogenic effects of sediments from selected locations in the Tiete River Basin by means of the sediment contact embryo toxicity assay with Danio rerio, in order to provide a comprehensive and realistic insight into the bioavailable hazard potential of these sediment samples. Lethal and sub-lethal effects were recorded, and high embryo toxicity could be found in the samples not only in the vicinity of the megacity Sao Paulo (Billings reservoir and Pinheiros River samples), but also downstream (in the reservoirs Barra Bonita, Promissao and Tres Irmaos). Results confirm that most toxicity is due to the discharges of the metropolitan area of Sao Paulo. However, they also indicate additional sources of pollutants along the river course, probably from industrial, agricultural and agroindustrial residues, which contribute to the degradation of each area. The sediment contact fish embryo test showed to be powerful tool to detect embryo toxicity in sediments, not only by being a sensitive method, but also for taking into account bioavailability. This test provides an ecological highly realistic and relevant exposure scenario, and should therefore be added in ecotoxicological sediment quality assessments. (C) 2011 Elsevier Inc. All rights reserved.

Identification of geodesic chirping Alfven modes and q-factor estimation in hot core tokamak plasmas in ASDEX Upgrade

Alfven eigenmodes (AE) driven by ion cyclotron resonance heating are usually registered by different diagnostic channels in the hot core plasmas of large tokamaks like JET and ASDEX Upgrade. These AE appear very near to the extremum points of Alfven wave continuum, which is modified by the geodesic effect due to poloidal mode coupling. It is shown that the AE spectrum may be explored as the magnetic spectroscopy (like Alfven cascades by Sharapov et al 2001 Phys. Lett. A 289 127) to determine the q-factor minimum and geodesic frequency at the magnetic axis in standard sawtoothed discharges without reversed shear.

Temporal behaviour of toroidal rotation velocity in the TCABR tokamak

A new method for determining the temporal evolution of plasma rotation is reported in this work. The method is based upon the detection of two different portions of the spectral profile of a plasma impurity line, using a monochromator with two photomultipliers installed at the exit slits. The plasma rotation velocity is determined by the ratio of the two detected signals. The measured toroidal rotation velocities of C III (4647.4 angstrom) and C VI (5290.6 angstrom), at different radial positions in TCABR discharges, show good agreement, within experimental uncertainty, with previous results (Severo et al 2003 Nucl. Fusion 43 1047). In particular, they confirm that the plasma core rotates in the direction opposite to the plasma current, while near the plasma edge (r/a > 0.9) the rotation is in the same direction. This technique was also used to investigate the dependence of toroidal rotation on the poloidal position of gas puffing. The results show that there is no dependence for the plasma core, while for plasma edge (r/a > 0.9) some dependence is observed.

Anisotropy of thermal stresses in confined dusty plasmas

Anisotropy of thermal stresses in confined dusty plasmas is considered. It is shown that in a multi-component low-temperature plasma containing electrons, ions and dust, the complicated dependence of the ion viscosity on ion temperature gradients leads to a plasma equilibrium state with anisotropic pressure. This pressure anisotropy can be of the order of the ion pressure in some limiting cases, in which the ion Larmor radius or the ion mean free path are of the order of the characteristic length of the plasma nonuniformity. For a sufficiently large dust number density, they contribute to the plasma pressure anisotropy and to its spatial dependence. Currently, it is not yet clear whether this equilibrium state is stable or not. Under these conditions, some convective plasma flows can arise in confinement devices. Therefore, this question needs special consideration.

Recycled effluent irrigation in vineyards : an Australian case study. I. issues and monitoring

The viticultural industry is becoming an increasingly significant part of the Australian agricultural sector, with gross earnings of over $4 billion in 2002. Expansion of the industry in the last decade has been rapid, however its heavy reliance on irrigation has resulted in further expansion in many wine growing regions being limited by the availability of water. This problem is not confined to the viticultural industry, with ever increasing pressures on water resources worldwide. As demands for water continue to rise, new strategies to meet demands must be adopted. One of the strategies being increasingly employed is the recycling of waste waters for a number of applications such as irrigation and industrial uses. The use of recycled water for vineyard irrigation provides a number of benefits. Among them are the reduced demands on potable supplies, reduced waste discharges to surface waters, and the opportunity for expansion of production. Recycled waters however, contain constituents which have the potential to cause deleterious effects to both production and the environment. Therefore, the use of recycled water for irrigation requires targetted monitoring and management to ensure the long-term sustainability of both the vineyard and the surrounding environment. Traditional monitoring techniques including water quality monitoring and soil testing can be complimented by new technologies and techniques which provide large quantities of information with relatively less labour and time. Such techniques can be used to monitor the vineyard environment to identify impacts arising from management practices, allowing vineyard managers to adjust management for sustainable production

Laboratory model studies of flushing of trapped salt water from a blocked tidal estuary

Results are presented from a series of laboratory model studies of the flushing of saline water from a partially- or fully-closed estuary. Experiments have been carried out to determine quantitatively the response of the trapped saline volume to fresh water flushing discharges Q for different values of the estuary bed slope α and the density difference (∆ρ)_o between the saline and fresh water. The trapped saline water forms a wedge within the estuary and for maintained steady discharges, flow visualisation and density profile data confirm that its response to the imposition of the freshwater purging flow occurs in two stages, namely (i) an initial phase characterised by intense shear-induced mixing at the nose of the wedge and (ii) a relatively quiescent second phase where the mixing is significantly reduced and the wedge is forced relatively slowly down and along the bed slope. Scalings based upon simple energy balance considerations are shown to be successful in (i) describing the time-dependent wedge behaviour and (ii) quantifying the proportion of input kinetic energy converted into increasing the potential energy of the wedge/river system. Measurements show that the asymptotic value of the energy conversion factor increases with increasing value of the river Froude number Fr_o at small values of Fr_o, thereafter reaching a maximum value and a gradual decrease at the highest values of Fr_o. Dimensional analysis considerations indicate that the normalised, time-dependent wedge position (x_w)³(g')o/q² can be represented empirically by a power-law relationship of the form (x_w)[(g')_o/q²]^1/3 =C [(t)[(g')_o²/q]^1/3]"where the proportionality coefficient C is a function of both Fr_o and the slope angle α and the exponent n has a value of 0.24. Successful attempts are made to relate the model data to existing field observations from a microtidal estuary.

Experiments with multiple, intermittent periodic flushing flows confirm the importance of the starting phase of each flushing event for the time dependent behaviour of the saline wedge after reaching equilibrium in the intervals between such events. For the parameter ranges investigated and for otherwise-identical external conditions, no significant differences are found in the position of the wedge between cases of sequential multiple flushing flows and steady single discharges of the same total duration.

The salt wedge position in a bar-blocked estuary subject to pulsed inflows

A series of laboratory experiments were carried out to investigate the response of a bar-blocked, saltwedge estuary to the imposition of both steady freshwater inflows and transient inflows that simulate storm events in the catchment area or the regular water releases from upstream reservoirs. The trapped salt water forms a wedge within the estuary, which migrates downstream under the influence of the freshwater inflow. The experiments show that the wedge migration occurs in two stages, namely (i) an initial phase characterized by intense shear-induced mixing at the nose of the wedge, followed by (ii) a relatively quiescent phase with significantly reduced mixing in which the wedge migrates more slowly downstream.

Provided that the transition time t_T between these two regimes satisfies t_T>g′h⁴L/q³α, as was the case for all our experiments and is likely to be the case for most estuaries, then the transition occurs at time t_T=1.2(gα³L⁶/g′³q²)^1/6, where g′=gΔρ/ρ0 is the reduced gravity, g the acceleration due to gravity, Δρ the density excess of the saline water over the density ρ₀ of the freshwater, q the river inflow rate per unit width, and L and α are the length and bottom slope of the estuary, respectively.

A simple model, based on conversion of the kinetic energy of the freshwater inflow into potential energy to mix the salt layer, was developed to predict the displacement xw over time t of the saltwedge nose from its initial position. For continuous inflows subject to t<t_T, the model predicts the saltwedge displacement as x_w/h=1.1 (t/τ)^1/3, where the normalizing length and time scales are h=(q²/g)^1/3 and τ=g′α²h4L/q³, respectively. For continuous inflows subject to t>tT, the model predicts the displacement as xw/h=0.45N1/6(t/τ)1/6/α, where N=q²/g′h²L is a non-dimensional number for the problem. This model shows very good agreement with the experiments. For repeated, pulsed discharges subject to t<t_T, the saltwedge displacement is given by (xw/h)3−(x0/h)(xw/h)2=1.3t/τ, where x₀ is the initial displacement following one discharge event but prior to the next event. For pulsed discharges subject to t>t_T, the displacement is given by (xw/h)⁶−(x0/h)(xw/h)⁵=0.008N(t/τ)/α⁶. This model shows very good agreement with the experiments for the initial discharge event but does systematically underestimate the wedge position for the subsequent pulses. However, the positional error is less than 15%.

Critical care nurses' beliefs about discharge planning process: a questionnaire survey

Aim: To report on the beliefs of critical care nurses with regard to the discharge planning process, in Victoria, Australia.

Methods: An exploratory descriptive design was used. A total of 502 Victorian critical care nurses were approached to take part in the study. A total of 218 eligible participants completed the survey, which represented a nett response rate of 43.4%. The data were analysed using descriptive statistics.

Results: The current discharge planning processes are ad hoc and influenced by patient acuity. Critical care nurses believe that workload issues, unplanned discharges and inadequate communication contribute to difficulties implementing the discharge plan.

'Green' treatment of acid mine drainage - a step towards sustainability

Sustainability is becoming increasingly important in the mining and mineral processing industries and must incorporate the associated waste products. Acid mine drainage (AMD) is one such by-product and is one of the most serious environmental problems facing the minerals industry today. The oxidation of sulphidic mine wastes often continues for a substantial period of time after mine closure, resulting in difficult and costly remediation and rehabilitation works. Mining companies are often reluctant to spend increasing amounts of money on waste treatment when the mine life is limited or even finished. Hence a simple, low maintenance and low-cost method of treating AMD is required. Whilst this paper does not address the issue of AMD, it does propose methods for removal of individual species from AMD with potential benefits, including raising AMD pH.

A novel concept of using biosolids as a biological adsorbent, or ‘biosorbent’, of metals from AMD is being investigated at a laboratory/pilot scale level. Biosolids are a by-product resulting from the biological treatment of wastewater, and have been previously shown to adsorb metals from aqueous solutions. This could lead to an environmentally sustainable or ‘green’ method for treating both AMD discharges and disposing/reusing the biosolids.

The result of a laboratory-scale study of the biosorption of Zn(II) is presented in this paper. Physical parameters including reaction kinetics, mixing speed and solution pH were investigated. Solution pH also rose an average of 2 pH units over the 24 hour equilibrium time – a valuable side effect when treating acid mine drainage. The outcome of the study highlights the usefulness of biosolids as a biosorbent for the removal/recovery of metal ions from acid mine drainage. A simple, low-cost treatment technology requiring low maintenance would be beneficial to the mining industry to address some issues relating to AMD and would help integrate environmental and economic considerations into sustainable environmental management.

Acoustic emission study on corona discharge using FDTD model

This paper attempts to study the propagating characteristics of acoustic signals emitted from the breakdown of air using time domain numerical model. Acoustic emissions are produced by high voltage faults such as partial discharge and surface discharge. Study of such emissions has become popular among researchers because of the promising correlation between partial and surface discharges and its byproduct, acoustic signal emission. In this paper, propagation characteristics of acoustic signals are studied using finite difference time domain (FDTD) method. Multiple monitoring points are placed within a designated computation space at different distance away from a source.