1,102 research outputs found
Estimating the leakage contribution of phosphate dosed drinking water to environmental phosphorus pollution at the nationalâscale
Understanding sources of phosphorus (P) to the environment is critical for the management of freshwater and marine ecosystems. Phosphate is added at water treatment works for a variety of reasons: to reduce pipe corrosion, to lower dissolved lead and copper concentrations at customerâs
taps and to reduce the formation of iron and manganese precipitates which can lead to deterioration in the aesthetic quality of water. However, the spatial distribution of leakage into the environment of phosphate added to mains water for plumbosolvency control has not been
quantified to date. Using water company leakage rates, leak susceptibility and road network mapping, we quantify the total flux of P from leaking water mains in England and Wales at a 1 km grid scale. This is validated against reported leaks for the UKs largest water utility. For 2014, we estimate the total flux of P from leaking mains to the environment to be c. 1.2 kt P/yr. Spatially, P flux is concentrated in urban areas where pipe density is highest, with major cities acting as a significant source of P (e.g. London into the Thames, with potentially 30% of total flux). The model suggests the majority (69%) of the P flux is likely to be to surface water. This is due to leakage
susceptibility being a function of soil corrosivity and shrinkâswell behaviour which are both controlled by presence of lowâpermeability clays. The location of major cities such as London close to the coast results in a potentially significant flux of P from mains leakage to estuarine environments. The contribution of leakage of phosphate dosed mains water should be considered in
future source apportionment and ecosystem management. The methodology presented is generic and can be applied in other countries where phosphate dosing is undertaken or used prior to dosing during investment planning
Phosphate dosing of mains water : novel approaches to water loss reduction through leakage detection and policy [abstract]
Detection and t
racing of leakage in the environment
are
essential component
s
of water loss
reduction strategies.
Industry standard techniques for tracing leaks include
analysis of chlorine and
trihalomethane concentrations, but levels of
these determinands can fall belo
w detection limits due
to their volatile nature
1
.
Consequently additional
tools to
trace
leakage in the environment are
a
useful step to move towards minimum losses
Mapping groundwater denitrification potential : methodology report
An understanding of the fate of nitrate in groundwater is vital for managing risks associated with nitrate pollution, and to safeguard groundwater supplies and groundwater-dependent surface waters. One of the main mechanisms to control nitrate is the designation of nitrate vulnerable zones (NVZs). Recent review of the designation process in England has highlighted that in some locations measured groundwater nitrate concentrations are not as high as might be expected from knowledge of the surface loads of nitrate applied at the ground surface. A possible reason for this is that the nitrate is being transformed through denitrification. The aim of this work was to develop a weight of evidence approach to allow the assessment of denitrification potential across groundwater in England using literature and existing groundwater and other relevant data
Quantification of nitrate storage in the vadose (unsaturated) zone: a missing component of terrestrial N budgets
National terrestrial nitrogen budgets for many developed countries have been calculated as part of the management of impacts of N on the environment, but these rarely represent the subsurface explicitly. Using estimates of vadose zone travel time and agricultural nitrate loading, we quantify, for the first time, the total mass of nitrate contained in the vadose zone of aquifers in England and Wales. This mass peaked in 2008 at 1400 kt N (800 to >1700 kt N from sensitivity analyses) which is approximately 2.5 to 6 times greater than saturated zone estimates for this period and indicates that the subsurface is an important store of reactive nitrogen. About 70% of the nitrate mass is estimated to be in the Chalk, with the remainder split between the Permo-Triassic sandstones, the Jurassic Oolitic limestones and minor aquifers. Current controls on fertiliser application mean that the vadose zone is now a nitrate source and in 2015 we estimate the net flux from the unsaturated zone to groundwater to be 72 kt N/annum. The mass of nitrate in the vadose zone should be included in future terrestrial nitrogen budgets at national and global scales to improve ecosystem management. This article is protected by copyright. All rights reserved
Low-cost hyperspectral imaging system: Design and testing for laboratory-based environmental applications
The recent surge in the development of low-cost, miniaturised technologies provides a significant opportunity to develop miniaturised hyperspectral imagers at a fraction of the cost of currently available commercial set-ups. This article introduces a low-cost laboratory-based hyperspectral imager developed using commercially available components. The imager is capable of quantitative and qualitative hyperspectral measurements, and it was tested in a variety of laboratory-based environmental applications where it demonstrated its ability to collect data that correlates well with existing datasets. In its current format, the imager is an accurate laboratory measurement tool, with significant potential for ongoing future developments. It represents an initial development in accessible hyperspectral technologies, providing a robust basis for future improvements
The changing trend in nitrate concentrations in major aquifers due to historical nitrate loading from agricultural land across England and Wales from 1925 to 2150
Nitrate is necessary for agricultural productivity, but can cause considerable problems if released into aquatic systems. Agricultural land is the major source of nitrates in UK groundwater. Due to the long time-lag in the groundwater system, it could take decades for leached nitrate from the soil to discharge into freshwaters. However, this nitrate time-lag has rarely been considered in environmental water management. Against this background, this paper presents an approach to modelling groundwater nitrate at the national scale, to simulate the impacts of historical nitrate loading from agricultural land on the evolution of groundwater nitrate concentrations. An additional process-based component was constructed for the saturated zone of significant aquifers in England and Wales. This uses a simple flow model which requires modelled recharge values, together with published aquifer properties and thickness data. A spatially distributed and temporally variable nitrate input function was also introduced. The sensitivity of parameters was analysed using Monte Carlo simulations. The model was calibrated using national nitrate monitoring data. Time series of annual average nitrate concentrations along with annual spatially distributed nitrate concentration maps from 1925 to 2150 were generated for 28 selected aquifer zones. The results show that 16 aquifer zones have an increasing trend in nitrate concentration, while average nitrate concentrations in the remaining 12 are declining. The results are also indicative of the trend in the flux of groundwater nitrate entering rivers through baseflow. The model thus enables the magnitude and timescale of groundwater nitrate response to be factored into source apportionment tools and to be taken into account alongside current planning of land-management options for reducing nitrate losses
Extracting Br(omega->pi^+ pi^-) from the Time-like Pion Form-factor
We extract the G-parity-violating branching ratio Br(omega->pi^+ pi^-) from
the effective rho-omega mixing matrix element Pi_{rho omega}(s), determined
from e^+e^- -> pi^+ pi^- data. The omega->pi^+ pi^- partial width can be
determined either from the time-like pion form factor or through the constraint
that the mixed physical propagator D_{rho omega}^{mu nu}(s) possesses no poles.
The two procedures are inequivalent in practice, and we show why the first is
preferred, to find finally Br(omega->pi^+ pi^-) = 1.9 +/- 0.3%.Comment: 12 pages (published version
Determination of Electromagnetic Source Direction as an Eigenvalue Problem
Low-frequency solar and interplanetary radio bursts are generated at
frequencies below the ionospheric plasma cutoff and must therefore be measured
in space, with deployable antenna systems. The problem of measuring both the
general direction and polarization of an electromagnetic source is commonly
solved by iterative fitting methods such as linear regression that deal
simultaneously with both directional and polarization parameters. We have
developed a scheme that separates the problem of deriving the source direction
from that of determining the polarization, avoiding iteration in a
multi-dimensional manifold. The crux of the method is to first determine the
source direction independently of concerns as to its polarization. Once the
source direction is known, its direct characterization in terms of Stokes
vectors in a single iteration if desired, is relatively simple. This study
applies the source-direction determination to radio signatures of flares
received by STEREO. We studied two previously analyzed radio type III bursts
and found that the results of the eigenvalue decomposition technique are
consistent with those obtained previously by Reiner et al. (Solar Phys. 259,
255, 2009). For the type III burst observed on 7 December 2007, the difference
in travel times from the derived source location to STEREO A and B is the same
as the difference in the onset times of the burst profiles measured by the two
spacecraft. This is consistent with emission originating from a single,
relatively compact source. For the second event of 29 January 2008, the
relative timing does not agree, suggesting emission from two sources separated
by 0.1 AU, or perhaps from an elongated region encompassing the apparent source
locations.Comment: 22 pages, 7 figures, Accepted in Solar Physic
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