Catchment-scale vulnerability assessment of groundwater pollution from diffuse sources using the DRASTIC method : a case study

The catchment-scale groundwater vulnerability assessment that delineates zones representing different levels of groundwater susceptibility to contaminants from diffuse agricultural sources has become an important element in groundwater pollution prevention for the implementation of the EUWater Framework Directive (WFD). This paper evaluates the DRASTIC method using an ArcGIS platform for assessing groundwater vulnerability in the Upper Bann catchment, Northern Ireland. Groundwater vulnerability maps of both general pollutants and pesticides in the study area were generated by using data on the factors depth to water, net recharge, aquifer media, soil media, topography, impact of vadose zone, and hydraulic conductivity, as defined in DRASTIC. The mountain areas in the study area have “high” (in 4.5% of the study area) or “moderate” (in 25.5%) vulnerability for general pollutants due to high rainfall, net recharge and soil permeability. However, by considering the diffuse agricultural sources, the mountain areas are actually at low groundwater pollution risk. The results of overlaying the maps of land use and the groundwater vulnerability are closer to the reality. This study shows that the DRASTIC method is helpful for guiding the prevention practices of groundwater pollution at the catchment scale in the UK

Relativistic dust disks and the Wilson-Mathews approach

Treating problems in full general relativity is highly complex and frequently approximate methods are employed to simplify the solution. We present comparative solutions of a infinitesimally thin relativistic, stationary, rigidly rotating disk obtained using the full equations and the approximate approach suggested by Wilson & Mathews. We find that the Wilson-Mathews method has about the same accuracy as the first post-Newtonian approximation.Comment: 4 Pages, 5 eps-figures, uses revtex.sty. Submitted to PR

Influence of temperature and nitrogen on growth, photosynthesis and accumulation of non-structural carbohydrate in a tropical grass, Panicum maximum var. trichoglum.

After an initial growth period on half-strength Hoagland solution at 25 deg C, plants of P. maximum var. trichoglume were transferred to N-free nutrient solution and an equal number were kept on half-strength Hoagland solution. Plants from both N treatments were grown under constant temperatures of 15, 20, 25, 30 or 35 deg . Leaf net photosynthetic rate, RGR and NAR/unit leaf area were affected to a similar relative extent with change in temperature or N, thereby precluding accumulation of very high percentages of total non-structural carbohydrates (% TNC). At low temperature and low N, changes in % TNC were inversely related to relative leaf area growth rate and also to some extent with dark respiration rate. In high-N plants, reduction in % TNC at higher temperatures was probably accentuated by the use of constant day/night temperatures. The influence of temperature on % TNC in low-N plants was slight. (Abstract retrieved from CAB Abstracts by CABI’s permission

Comparative response to nitrogen deficiency of a tropical and temperate grass in the interrelation between photosynthesis, growth, and the accumulation of non-structural carbohydrate.

A tropical grass, Panicum maximum var. trichoglume and a temperate grass, Lolium perenne, were grown in controlled environment rooms at near optimum temperatures of 25 and 18 deg C, respectively. After an initial period of growth on full nitrogen nutrient solution, a proportion of the plants of both species were transferred to 'nil' N nutrient solution. A sequence of destructive harvests was taken as the plants became increasingly N deficient, and calculations were made of relative growth rate (RW), relative leaf area growth rate (RA) and net assimilation rate per unit leaf area (EA). On a similarly treated group of plants, net photosynthetic rate (PN) and dark respiration rate of attached leaves were measured.Organic and nitrate N were estimated on the photosynthesis-tested leaves, and on comparable leaves from the growth analysis plants at each harvest. Percentage total non-structural carbohydrate (%TNC) was estimated for P. maximum only.P. maximum maintained a higher RW and PN than L. perenne at comparable percent leaf N. With increasing N stress, EA of both species declined to a similar relative extent, but RA of P. maximum decreased much less than that of L. perenne. This difference in response to N between the species in the balance of assimilate input and consumption in new growth may in part explain why, under N deficiency, published studies indicate that % TNC reach higher levels in L. perenne and other temperate grasses than in tropical grasses such as P. maximum. (Abstract retrieved from CAB Abstracts by CABI’s permission

A Study of Long-Term Satellite-Tracked Iceberg Drifts in Baffin Bay and Davis Strait

Long-term, satellite-tracked iceberg trajectories were analyzed relative to the larger spatial and temporal scales of iceberg drift in Baffin Bay and Davis Strait. Berg movements were concentrated in the core of the Baffin Current which flows along the continental slope in a primarily southerly direction. The net rate of southward movements was found to be governed by a combination of grounding and landfast ice entrapment which tended to be of particular significance in areas of the coastal shelf adjacent to major submarine canyon systems.Key words: Baffin Bay, Davis Strait, icebergs, satellite-trackin

A daily representation of Great Britain's energy vectors : Natural gas, electricity and transport fuels

In much of Europe there is a strong push to decarbonise energy demands, including the largest single end-use demand – heat. Moving heat demands over to the electrical network poses significant challenges and the use of hybrid energy vector and storage systems (heat and electrical storage) will be a critical component in managing this transition. As an example of these challenges (facing many developed countries), the scale of recently available daily energy flows through the UK’s electrical, gas and transport systems are presented. When this data is expressed graphically it illustrates important differences in the demand characteristics of these different vectors; these include the quantity of energy delivered through the networks on a daily basis, and the scale of variability in the gas demand over multiple timescales (seasonal, weekly and daily). As the UK proceeds to migrate heating demands to the electrical network in its drive to cut carbon emissions, electrical demand will significantly increase. Additionally, the greater variability and uncertainty shown in the gas demand will also migrate to the electrical demand posing significant difficulties for the maintenance of a secure and reliable electrical system in the coming decades. The paper concludes an analysis of the different means of accommodating increasingly volatile electricity demands in future energy networks

A Linear-Nonlinear Formulation of Einstein Equations for the Two-Body Problem in General Relativity

A formulation of Einstein equations is presented that could yield advantages in the study of collisions of binary compact objects during regimes between linear-nonlinear transitions. The key idea behind this formulation is a separation of the dynamical variables into i) a fixed conformal 3-geometry, ii) a conformal factor possessing nonlinear dynamics and iii) transverse-traceless perturbations of the conformal 3-geometry.Comment: 7 pages, no figure

Irrotational binary neutron stars in quasiequilibrium

We report on numerical results from an independent formalism to describe the quasi-equilibrium structure of nonsynchronous binary neutron stars in general relativity. This is an important independent test of controversial numerical hydrodynamic simulations which suggested that nonsynchronous neutron stars in a close binary can experience compression prior to the last stable circular orbit. We show that, for compact enough stars the interior density increases slightly as irrotational binary neutron stars approach their last orbits. The magnitude of the effect, however, is much smaller than that reported in previous hydrodynamic simulations.Comment: 4 pages, 2 figures, revtex, accepted for publication in Phys. Rev.

An Investigation on Cooling of CZT Co-Planar Grid Detectors

The effect of moderate cooling on CdZnTe semiconductor detectors has been studied for the COBRA experiment. Improvements in energy resolution and low energy threshold were observed and quantified as a function of temperature. Leakage currents are found to contribute typically $\sim$5 keV to the widths of photopeaks.Comment: 14 pages, 9 figures. Accepted for publication in Nuclear Inst. and Methods in Physics Research,

Great Britain's Energy Vectors and Transmission Level Energy Storage

As an example of the challenges facing many developed countries, the scale of daily energy flows through Great Britain's electrical, gas and transport systems are presented. When this data is expressed graphically it illustrates important differences in the demand characteristics of these different vectors; these include the scale of energy delivered through the networks on a daily basis, and the scale of variability in the different demands over multiple timescales (seasonal, weekly and daily). The paper discusses energy storage in general; the scale of within day stores of energy available to the gas and electrical transmission networks, and suggests Synthetic Natural Gas as an interesting energy carrier that could use existing natural gas infrastructure